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Sample records for sandstone facies texas

  1. Paleotectonic controls on sandstone trends and depositional facies distribution of the low-permeability, gas-bearing Cleveland Formation (Upper Pennsylvanian), Texas panhandle

    SciTech Connect

    Hentz, T.F. )

    1992-04-01

    Low-permeability ('tight') reservoir sandstones of the Cleveland Formation have produced over 412 bcf of natural gas through January 1990, mostly from Ochiltree and Lipscomb counties in the northeastern Texas panhandle. Although large-scale gas production started in 1956, the regional stratigraphic, depositional, and structural settings of the Cleveland are poorly known. A study was conducted in a 5100-mi{sup 2}, seven-county area in the western Anadarko basin using log suites from over 860 evenly spaced wells, three cores, and numerous sample logs. Reservoir facies of the predominantly siliciclastic Cleveland Formation, in part, were deposited as a series of three eastward-prograding, probably wave-dominated deltas composed of (in ascending sequence) prodelta, distal delta-front, and proximal delta-front deposits. An upward-fining fluvial sandstone occurs in one stratigraphic zone in the middle Cleveland throughout most of the study area. Distinctive trends of thickness variation record elements of the paleophysiography of the Cleveland depositional area and evidence of syndepositional faulting, flexure, and marked differential subsidence. Depositional patterns were controlled by (1) a paleohigh in the western part of the study area (eastern flank of Cimarron arch) that separates siliciclastic facies from carbonate-dominate Cleveland of the Kansas shelf, (2) subsidence of two subbasins within a northwest-trending half-graben bounded by a syndepositional fault on its southern edge and a monoclinal flexure on the north, and (3) a two-tiered depositional shelf that reflects differential subsidence of an underlying Oswego Limestone buildup.

  2. Geology of a stratigraphically complex natural gas play: Canyon Sandstones, Val Verde Basin, southwest Texas. Topical report, January-October 1993

    SciTech Connect

    Laubach, S.E.; Clift, S.J.; Hamlin, H.S.; Dutton, S.P.; Hentz, T.F.

    1994-07-01

    The report examines the influence of stratigraphy, diagenesis, natural fractures, and in situ stress on low-permeability, gas-bearing sandstone reservoirs of the Paleozoic Ozona and Sonora Canyon Sandstones of the Val Verde Basin, Texas. The main stratigraphic controls on distribution and quality of Canyon Sandstone reservoirs are submarine fan depositional patterns. These patterns are revealed in regional facies and maximum sandstone maps. Siderite cement is key to good within-sandstone reservoir quality. Natural fractures are widespread in both Ozona and Sonora Canyon sandstones. They could be future targets for advanced drilling methods, and they need to be taken into account in hydraulic fracture treatment design and reservoir management.

  3. Palaeocurrent and facies analysis of Ajali Sandstone in Western Anambra basin, Nigeria

    NASA Astrophysics Data System (ADS)

    Akpofure, Edirin; Akana, Tombra S.

    2016-06-01

    Outcrops of the Campanian - Maastrichtian Ajali Sandstone in Ayogwiri, Fugar and Orame in the Western Anambra Basin allow for the recognition of palaeocurrent fabric and facies characterization of the formation. Detailed outcrop logging was carried out and production of graphic logs was made for each outcrop location. The Ajali is extensively cross-stratified with different types of cross-bedding, such as the planar, trough, and herring-bone cross-beddings. Palaeocurrent directions of the cross-beds were taken using the compass-clinometer to elucidate the palaeocurrent direction of the environment of formation and rose diagrams were constructed for each bed. The Ajali Sandstone is made up of two basic facies. The basal facies, is made up of thinly laminated, heterolithic beds of the shoreface environment. The upper facies consists mainly of cross-bedded sandstones of a tidally influenced shallow marine environment. The major palaeocurrent direction of the Ajali Sandstone in the studied area was in the NE direction which infers the sediment provenance source to be the uplifted Abakiliki Anticlinorium. However, subordinate direction to the south occurs in Orame1.

  4. Post-depositional alteration of titanomagnetite in a Miocene sandstone, south Texas (U.S.A.)

    USGS Publications Warehouse

    Reynolds, R.L.

    1982-01-01

    Petrographic and geochemical studies have yielded information on the time-space relationships of the post-depositional alteration of detrital titanomagnetite (Ti-mt) in fine- to medium-grained sandstone from unoriented core samples (taken below the water table at depths of 30-45 m) of the Miocene Catahoula Sandstone, south Texas. Aqueous sulfide introduced from sour gas reservoirs along a growth fault into part of the Catahoula shortly after deposition resulted in the replacement at the periphery of Ti-mt grains by iron disulfide (FeS2) minerals. Remnants of Ti-mt in cores of the partly sulfidized grains show no evidence of earlier hematitic oxidation. After sulfidization, part of the sandstone body was invaded by oxygenated groundwaters flowing down a shallowly inclined (1??) hydrologic gradient. The boundary between oxidized and reduced facies is clearly defined by the distribution of ferric and ferrous iron minerals, and the concentrations of Mo, U, and Se. In oxidized (light-red) strata that had not been previously subjected to sulfidic-reducing conditions but that are correlative with strata containing FeS2 minerals, Ti-mt has been partly to entirely replaced pseudomorphously by hematite to form martite. The absence of hematitic alteration of Ti-mt in the reduced facies is strong evidence that martite in the oxidized facies formed after deposition. ?? 1982.

  5. Depositional systems and productive characteristics of major low-permeability gas sandstones in Texas

    SciTech Connect

    Finely, R.J.; Seni, S.J.; Tyler, N.; Lin, Z.S.

    1984-04-01

    Major tight gas sandstones in Texas range from lenticular to blanket geometry, from hydropressured to geopressured, and from Pennsylvanian to Eocene in age. The Cotton Valley sandstone (East Texas basin) includes barrier- and marine-bar sandstones (blanket) derived from prograding fan deltas with associated braided stream, delta-front, and prodelta deposits. Estimated gas in place varies from 53 tcf (Cotton Valley) to 25 tcf (Travis Peak); most wells initially produce from 500 to 1500 mcf and few wells produce 2500 mcf. Tight gas sandstones in the Wilcox and Vicksburg Groups (Gulf Coast basin) are mostly geopressured delta-front, shelf, and slope deposits. Initial well yields are most 300 to 2400 mcfd; resource estimates for tight Wilcox and Vicksburg trends are not available. Canyon Group sandstones of the Sonora basin (parts of the Ozona arch, Concho platform and Val Verde basin) contain 24 tcf of estimated gas in place and initial flow rates are commonly 100 to 1000 mcf. These sandstones are broadly lenticular and are interpreted to be submarine fan and possibly shelf-margin deposits. The Olmos Formation (Maverick basin) contains gas within broadly lenticular delta-front deposits of high-constructive delta systems; liquid hydrocarbons in the Olmos are trapped in more proximal facies. Gas in place in the Olmos is estimated to be 5 tcf and initial well yields are 300 to 3000 mcf. In 1980, 893 wells were completed in formations designated as partially or completely tight by the Railroad Commission of Texas. These completions represent 2.5% of new gas wells in the state, but 28.0% of those completed in the 5000 to 15,000-ft depth range in that year.

  6. Tidal flats and tempestites: An integrated approach to an atypical facies of the Cypress Sandstone

    SciTech Connect

    Stark, J.T. ); Smosna, R.; Bruner, K. ); Davis, R.; Musselman, J.

    1994-08-01

    The Cypress Sandstone (Mississippian Chesterian series) is a major hydrocarbon-producing formation in the Illinois basin. Depositional settings consisting of fluvial and deltaic environments are recognized throughout the basin. Upon the southern flank of the Moorman syncline in the Stringtown field, a distal facies of the Cypress depositional system is recognized as a stormswept tidal flat. Developed above marine shales, a lower shoreface/platform facies is interbedded with carbonate-rich tempesite storm deposits. High clay concentrations within the sands create non-reservoir conditions, characterized by low permeabilities and high irreducible water content. As proximal tidal environments build seaward, a scour channel downcut into the lower shoreface/platform facies. Continuing tidal flat progradation deposited lower and middle tidal-flat pay sands on the scour surface. Overlying upper tidal-flat strata provide the seal for this reservoir. Regional transgression destroyed the balance of the prograded tidal flat, preserving the sequence only within the deep scour features. Lithologically, the pay sands are classified as quartzarenites and sublitharenites, the latter containing appreciable concentrations of shale rock fragments and feldspars. The development of secondary moldic porosity is the primary determinant of reservoir quality, derived from the dissolution of rock fragment fabrics. Geophysical well logs and Formation MicroScanner data analysis were correlated to core lithogies, and were successfully used to identify various facies within the Cypress Sandstone section. Early development wells flowed oil, due to overpressured reservoir conditions.

  7. Facies and stratigraphy of the Pennsylvanian Warren Point Sandstone, central Cumberland Plateau, Tennessee

    SciTech Connect

    Hurd, S.A.; Stapor, F.W. Jr. . Earth Sciences Dept.)

    1994-03-01

    The Warren Point Sandstone is a fine-grained, quartz arenite composed primarily of the following three facies: planar bedded 2-D cross beds, low angle cross beds, and broad, shallow channel-fills. Ripple cross lamination, horizontal lamination, and laminated shale facies are also observed. These facies units are grouped into four of Miall's major architectural elements: sandy bedforms, channels, laminated sand sheets, and overbank fines. Paleocurrent measurements made on the 2-D cross beds indicate southwest transport. Throughout this region the Warren Point occurs as a nearly continuous and essentially homogeneous, 7--12 m-thick, sandstone sheet. The authors interpret a sandy braid plain depositional environment for the Warren Point. Initial sand composition data suggest a foreland uplift provenance that along with the southwest transport indicate the Alleghenian orogen as the probable source. The Warren Point disconformably overlies each of it's two stratigraphically subjacent units: the Pennsylvanian Raccoon Mountain (0--5 m-thick) and the upper limestone member of the Mississippian Pennington formations. The Sewanee Conglomerate disconformably overlies the Warren Point and, near Spencer, TN, rests directly on the Pennington limestone member that was a topographic high during Warren Point deposition. The absence of underlying shelfal and marginal marine Pennsylvanian siliciclastics in conjunction with the Warren Point's basal disconformity suggests a sea-level fall that resulted in a basinward facies shift.

  8. Sequence stratigraphy and facies of estuarine Borrego Pass sandstone, New Mexico

    SciTech Connect

    Tillman, R.W.; Nummedal, D.

    1989-09-01

    The Coniacian-age Borrego Pass sandstone outcrops along the southern flank of the San Juan basin between Gallup and Albuquerque, New Mexico. The unit is discontinuous along strike, forming five discrete sand bodies separated by areas of apparent nondeposition. Sequence stratigraphically, the Borrego Pass sandstone is inferred to represent a transgressive systems tract related to the Coniacian sea level rise. Observed discontinuities along strike of this sandstone suggest the existence of significant coastal plain relief in the form of estuaries which were previously valleys cut and occupied by Torrivio Member (Gallup Formation) streams during the preceding sea level lowstand. The base of the Torrivio is a sequence boundary. With rise in sea level the estuaries were, in part, filled by the tidally dominated Borrego Pass sandstone. Nine different lithofacies are discriminated on the basis of lithology, physical and biogenic sedimentary structures, paleoflow patterns, fossil content, and lateral and vertical trends in texture. Coarse-grained facies are flood-tidal deltas, tidal channels, washover fans, oyster reefs, estuary mouth shoals, and fluvial (distributary ) channels. The finer grained facies are bioturbated back-barrier tidal flats, coals and carbonaceous shales, and flood-plain shales.

  9. Clarksville field Red River County, Texas: Production and facies interpretation

    SciTech Connect

    Reed, C.H. )

    1991-03-01

    The Clarksville field was discovered in December in 1985 while targeting a deeper paleozoic horizon. Since production went on line in 1986, this field has produced over 1 million barrels of oil (MMBO) with the appearance of a considerably longer and more lucrative life. The producing horizon is a Jurassic-age lithic conglomerate sitting unconformably on the Paleozoic and Triassic structural front of the buried Ouachita range. Facies correlation out of the basin indicate this unit to be Louark age. Mapping and compositional analysis indicate the depositional environmental of this unit to be an arid climate alluvial fan deposited as a 'Bajada' complex. This fan system was laid down at the updip margin of the actively forming Mesozoic embayment where it meets the Ouachita structural front. The significance of this field is demonstrated by the production yield at a relatively shallow depth (5800 ft). At this time, production similar to Clarksville field has yet to be encountered anywhere along the Mesozoic rim of the East Texas basin but does represent a viable exploration trend, in addition to being a gateway for future paleozoic production in the basin.

  10. Consolidation of geologic studies of geopressured-geothermal resources in Texas: Barrier-bar tidal-channel reservoir facies architecture, Jackson Group, Prado field, South Texas; Final report

    SciTech Connect

    Seni, S.J.; Choh, S.J.

    1994-01-01

    Sandstone reservoirs in the Jackson barrier/strandplain play are characterized by low recovery efficiencies and thus contain a large hydrocarbon resource target potentially amenable to advanced recovery techniques. Prado field, Jim Hogg County, South Texas, has produced over 23 million bbl of oil and over 32 million mcf gas from combination structural-stratigraphic traps in the Eocene lower Jackson Group. Hydrocarbon entrapment at Prado field is a result of anticlinal nosing by differential compaction and updip pinch-out of barrier bar sandstone. Relative base-level lowering resulted in forced regression that established lower Jackson shoreline sandstones in a relatively distal location in central Jim Hogg County. Reservoir sand bodies at Prado field comprise complex assemblages of barrier-bar, tidal-inlet fill, back-barrier bar, and shoreface environments. Subsequent progradation built the barrier-bar system seaward 1 to 2 mi. Within the barrier-bar system, favorable targets for hydrocarbon reexploration are concentrated in tidal-inlet facies because they possess the greatest degree of depositional heterogeneity. The purpose of this report is (1) to describe and analyze the sand-body architecture, depositional facies variations, and structure of Prado field, (2) to determine controls on distribution of hydrocarbons pertinent to reexploration for bypassed hydrocarbons, (3) to describe reservoir models at Prado field, and (4) to develop new data affecting the suitability of Jackson oil fields as possible candidates for thermally enhanced recovery of medium to heavy oil.

  11. Multinomial Logistic Regression & Bootstrapping for Bayesian Estimation of Vertical Facies Prediction in Heterogeneous Sandstone Reservoirs

    NASA Astrophysics Data System (ADS)

    Al-Mudhafar, W. J.

    2013-12-01

    Precisely prediction of rock facies leads to adequate reservoir characterization by improving the porosity-permeability relationships to estimate the properties in non-cored intervals. It also helps to accurately identify the spatial facies distribution to perform an accurate reservoir model for optimal future reservoir performance. In this paper, the facies estimation has been done through Multinomial logistic regression (MLR) with respect to the well logs and core data in a well in upper sandstone formation of South Rumaila oil field. The entire independent variables are gamma rays, formation density, water saturation, shale volume, log porosity, core porosity, and core permeability. Firstly, Robust Sequential Imputation Algorithm has been considered to impute the missing data. This algorithm starts from a complete subset of the dataset and estimates sequentially the missing values in an incomplete observation by minimizing the determinant of the covariance of the augmented data matrix. Then, the observation is added to the complete data matrix and the algorithm continues with the next observation with missing values. The MLR has been chosen to estimate the maximum likelihood and minimize the standard error for the nonlinear relationships between facies & core and log data. The MLR is used to predict the probabilities of the different possible facies given each independent variable by constructing a linear predictor function having a set of weights that are linearly combined with the independent variables by using a dot product. Beta distribution of facies has been considered as prior knowledge and the resulted predicted probability (posterior) has been estimated from MLR based on Baye's theorem that represents the relationship between predicted probability (posterior) with the conditional probability and the prior knowledge. To assess the statistical accuracy of the model, the bootstrap should be carried out to estimate extra-sample prediction error by randomly

  12. Fluvial architecture and reservoir heterogeneity of middle Frio sandstones, Seeligson field, Jim Wells and Kleberg Counties, south Texas

    SciTech Connect

    Jirik, L.A.; Kerr, D.R.; Zinke, S.G.; Finley, R.J. )

    1990-05-01

    Evaluation of fluvial Frio reservoirs in south Texas reveals a complex architectural style potentially suited to the addition of incremental gas reserves through recognition of untapped compartments or bypassed gas zones. Seeligson field is being studied as part of a GRI/DOE/Texas-sponsored program, in cooperation with Oryx Energy Company and Mobil Exploration and Production U.S., Inc., and is designed to develop technologies and methodologies for increasing gas reserves from conventional reservoirs in mature fields. Seeligson field, discovered in 1937, has produced 2.2 tcf of gas from more than 50 middle Frio reservoirs. Cross sections as well as net sand and log facies maps illustrate depositional style, sandstone geometry, and reservoir heterogeneities. Far-offset vertical seismic profiles show laterally discontinuous reflections corresponding to the reservoirs. Lenticular lateral-bar sandstones dominate channel-fill deposits that together are commonly less than 50 ft thick, forming belts of sandstone approximately 2,500 ft wide. Crevasse-splay deposits commonly extend a few thousand feet beyond the channel system. Sand-rich channel-fill deposits are flanked by levee and overbank mudstones, isolating the reservoirs in narrow, dip-elongate trends. Deposition on an aggrading coastal plain resulted in a pattern of laterally stacked sandstone bodies that are widespread across the study area. Alternating periods of more rapid aggradation resulted in deposition of vertically stacked sandstones with limited areal distribution. Facies architecture of both depositional styles has implications for reservoir compartmentalization. Reservoir compartments within a laterally stacked system may be leaky, resulting from sandstone contact from producing wells along depositional axes. This effect is a major factor controlling incremental recovery. Reservoirs in vertically stacked systems should be better isolated.

  13. Reservoir heterogeneity in middle Frio fluvial sandstones: Case studies in Seeligson field, Jim Wells County, Texas

    SciTech Connect

    Jirik, L.A. )

    1990-09-01

    Detailed evaluation of middle Frio (Oligocene) fluvial sandstones reveals a complex architectural style potentially suited to the addition of gas reserves through recognition of poorly drained reservoir compartments and bypassed gas zones. Seeligson field is being studied as part of a Gas Research Institute/US Department of Energy/State of Texas-sponsored program, with the cooperation of Oryx Energy Company and Mobil Exploration and Producing US, Inc. Four reservoirs, Zones 15, 16D, 16E, and 19C, were studied in a 20 mi{sup 2} area within Seeligson field. Collectively, these reservoirs have produced more than 240 bcf of gas from wells within the study area. Detailed electric log correlation of individual reservoirs enabled subdivision of aggregate producing zones into component genetic units. Cross sections, net-sandstone maps, and log-facies maps were prepared to illustrate depositional style, sand-body geometry, and reservoir heterogeneity. Zones 15 and 19C are examples of laterally stacked fluvial architecture. Individual channel-fill sandstones range from 10 to 50 ft thick, and channel widths are approximately 2,500 ft. Crevasse-splay sandstones may extend a few thousand feet from the main channel system. Multiple, overlapping channel and splay deposits commonly form sand-rich belts that result in leaky reservoir compartments that may be incompletely drained. Zones 16D and 16E are examples of vertically stacked fluvial architecture, with discrete, relatively thin and narrow channel and splay sandstones generally encased within floodplain muds. This architectural style is likely to form more isolated reservoir compartments. Although all of these reservoirs are currently considered nearly depleted, low-pressure producers, recent well completions and bottomhole pressure data indicate that untapped or poorly drained compartments are being encountered.

  14. Diagenetic facies controls on pore structure and rock electrical parameters in tight gas sandstone

    NASA Astrophysics Data System (ADS)

    Liu, Hongping; Zhao, Yanchao; Luo, Yang; Chen, Zhaoyou; He, Sheng

    2015-08-01

    Rock electrical parameters of tight gas sandstone show large variations in the T2 member in Dingbei Block, Ordos Basin, China. Applying the same rock electrical parameters in water saturation calculations would lead to large errors. Based on casting thin sections, x-ray diffraction, scanning electron microscopy (SEM), cathode luminescence, porosity and permeability, image analysis, and high-pressure mercury intrusion/withdrawal method, identification of the diagenetic facies are first conducted, and then their pore structure and their relationship with rock electrical parameters are investigated. Five diagenetic facies (A-E), which are identified based mainly on pore types and authigenic minerals, have different pore structure and rock electrical parameters. Conceptual models that incorporate the rock properties of each diagenetic facies have been built, before applying the electrical efficiency theory to explain the values of cementation exponent (m) and saturation exponent (n). A conventional network model, a shunt pore model, a netted pore model, and a dotted line model are utilized to mimic the intergranular pores, authigenic kaolinite intercrystal pores, carbonate-cement dissolution pores, and clay-matrix intercrystal pores, respectively. A decrease of the contents of large pores increases electrical efficiency and therefore reduces m. The saturation exponent, which depends on the distribution of water and gas, can be better understood by applying the different pore models. In the shunt and netted pore models, gas displacement starts from the larger pores and smaller pores provide alternative conduction pathways, hence sustaining electrical efficiency and decreasing n. Clay-matrix intercrystal pores are mainly micropores, since the brine in the rocks are isolated after gas displacement, reducing overall electrical efficiency and dramatically increasing the value of n in the diagenetic facies, which is dominated by clay-matrix intercrystal pores.

  15. Differentiating Detrital and Metamorphic Monazite in Greenschist-Facies Sandstones From the Witwatersrand Supergroup

    NASA Astrophysics Data System (ADS)

    Muhling, J. R.; Rasmussen, B.

    2009-05-01

    Monazite is a robust and reliable geochronometer of low-temperature metamorphic and hydrothermal events. It is a widespread accessory phase in sedimentary rocks metamorphosed at prehnite-pumpellyite to lower greenschist facies grade, and also in a range of hydrothermal ore deposits. Its ability to date multiple fluid-flow events in low-grade metasedimentary belts has been largely neglected, possibly because of a misconception that it is rare in these rocks and possibly because of misidentification of metamorphic monazite grains as detrital. Both detrital and metamorphic monazites are present in sandstone and conglomerate from the Witwatersrand Supergroup but can be distinguished by their occurrence, chemistry and age. Detrital grains were unstable during regional greenschist-facies metamorphism, and show evidence for a number of destructive reactions dependent on bulk rock composition and the original composition of the monazite. In quartz sandstone and conglomerate, detrital grains were present in heavy mineral bands with pyrite, zircon and chromite. The monazite grains have been pseudomorphed by intergrowths of apatite, florencite and Th-silicate, as well as matrix muscovite and chlorite. In some samples, Th-silicate forms only minute specks but in others it forms larger prismatic crystals that comprise up to 2% of some pseudomorphs. These variations may reflect differences in the original compositions of the detrital grains. In other samples detrital monazite cores, dated at 2.8-3.0 Ga, are enclosed within 2.04 Ga metamorphic rims. These composite grains formed by dissolution and reprecipitation of monazite during metamorphism. The cores and rims have distinctly different compositions, and the metamorphic rims show pronounced zoning of REE. In more calcic sandstone monazite occurs in heavy mineral bands with chromite, zircon, rutile, pyrite, apatite, Th-silicate, allanite and baddeleyite. These sandstones are notably rich in Ca-bearing minerals such as epidote

  16. Submarine-fan facies associations of the Upper Cretaceous and Paleocene Gottero Sandstone, Ligurian Apennines, Italy

    USGS Publications Warehouse

    Nilsen, T.H.; Abbate, E.

    1984-01-01

    The Upper Cretaceous and Paleocene Gottero Sandstone was deposited as a small deep-sea fan on ophiolitic crust in a trench-slope basin. It was thrust northeastward as an allochthonous sheet in Early and Middle Cenozoic time. The Gottero, as thick as 1500 m, was probably derived from erosion of Hercynian granites and associated metamorphic rocks in northern Corsica. Outcrops of inner-fan channel, middle-fan channel and interchannel, outer-fan lobe, fan-fringe, and basin-plain facies associations indicate that the depositional model of Mutti and Ricci Lucchi for mixed-sediment deep-sea fans can be used. The original fan had a radius of 30 to 50 km. ?? 1984 Springer-Verlag New York Inc.

  17. Facies architecture of the Bluejacket Sandstone in the Eufaula Lake area, Oklahoma: Implications for the reservoir characterization of the Bartlesville Sandstone

    SciTech Connect

    Ye, Liangmiao; Yang, Kexian

    1997-08-01

    Outcrop studies of the Bluejacket Sandstone (Middle Pennsylvanian) provide significant insights to reservoir architecture of the subsurface equivalent Bartlesville Sandstone. Quarry walls and road cuts in the Lake Eufaula area offer excellent exposures for detailed facies architectural investigations using high-precision surveying, photo mosaics. Directional minipermeameter measurements are being conducted. Subsurface studies include conventional logs, borehole image log, and core data. Reservoir architectures are reconstructed in four hierarchical levels: multi-storey sandstone, i.e. discrete genetic intervals; individual discrete genetic interval; facies within a discrete genetic interval; and lateral accretion bar deposits. In both outcrop and subsurface, the Bluejacket (Bartlesville) Sandstone comprises two distinctive architectures: a lower braided fluvial and an upper meandering fluvial. Braided fluvial deposits are typically 30 to 80 ft thick, and are laterally persistent filling an incised valley wider than the largest producing fields. The lower contact is irregular with local relief of 50 ft. The braided-fluvial deposits consist of 100-400-ft wide, 5-15-ft thick channel-fill elements. Each channel-fill interval is limited laterally by an erosional contact or overbank deposits, and is separated vertically by discontinuous mudstones or highly concentrated mudstone interclast lag conglomerates. Low-angle parallel-stratified or trough cross-stratified medium- to coarse-grained sandstones volumetrically dominate. This section has a blocky well log profile. Meandering fluvial deposits are typically 100 to 150 ft thick and comprise multiple discrete genetic intervals.

  18. Consolidation of geologic studies of geopressured-geothermal resources in Texas: Barrier-bar tidal-channel reservoir facies architecture, Jackson Group, Prado Field, South Texas

    SciTech Connect

    Seni, S.J.; Choh, S.J.

    1993-09-01

    Sandstone reservoirs in the Jackson barrier/strandplain play are characterized by low recovery efficiencies and thus contain a large hydrocarbon resource target potentially amenable to advanced recovery techniques. Prado field, Jim Hogg County, South Texas, has produced over 23 million bbl of oil and over 32 million mcf gas from combination structural-stratigraphic traps in the Eocene lower Jackson Group. Hydrocarbon entrapment at Prado field is a result of anticlinal nosing by differential compaction and updip pinch-out of barrier bar sandstone. Relative base-level lowering resulted in forced regression that established lower Jackson shoreline sandstones in a relatively distal location in central Jim Hogg County. Reservoir sand bodies at Prado field comprise complex assemblages of barrier-bar, tidal-inlet fill, back-barrier bar, and shoreface environments. Subsequent progradation built the barrier-bar system seaward 1 to 2 mi. With the barrier-bar system, favorable targets for hydrocarbon reexploration are concentrated in tidal-inlet facies because they possess the greatest degree of depositional heterogeneity.

  19. Impact of depositional facies on the distribution of diagenetic alterations in the Devonian shoreface sandstone reservoirs, Southern Ghadamis Basin, Libya

    NASA Astrophysics Data System (ADS)

    Khalifa, Muftah Ahmid; Morad, Sadoon

    2015-11-01

    The middle Devonian, shoreface quartz arenites (present-day burial depths 2833-2786 m) are important oil and gas reservoirs in the Ghadamis Basin, western Libya. This integrated petrographic and geochemical study aims to unravel the impact of depositional facies on distribution of diagenetic alterations and, consequently, related reservoir quality and heterogeneity of the sandstones. Eogenetic alterations include the formation of kaolinite, pseudomatrix, and pyrite. The mesogenetic alterations include cementation by quartz overgrowths, Fe-dolomite/ankerite, and illite, transformation of kaolinite to dickite, illitization of smectite, intergranular quartz dissolution, and stylolitization, and albitization of feldspar. The higher energy of deposition of the coarser-grained upper shoreface sandstones combined with less extensive chemical compaction and smaller amounts of quartz overgrowths account for their better primary reservoir quality compared to the finer-grained, middle-lower shoreface sandstones. The formation of kaolin in the upper and middle shoreface sandstones is attributed to a greater flux of meteoric water. More abundant quartz overgrowths in the middle and lower shoreface is attributed to a greater extent of stylolitization, which was promoted by more abundant illitic clays. This study demonstrated that linking the distribution of diagenetic alterations to depositional facies of shoreface sandstones leads to a better understanding of the impact of these alterations on the spatial and temporal variation in quality and heterogeneity of the reservoirs.

  20. Assessment of undiscovered sandstone-hosted uranium resources in the Texas Coastal Plain, 2015

    USGS Publications Warehouse

    Mihalasky, Mark J.; Hall, Susan M.; Hammarstrom, Jane M.; Tureck, Kathleen R.; Hannon, Mark T.; Breit, George N.; Zielinski, Robert A.; Elliott, Brent

    2015-01-01

    The U.S. Geological Survey estimated a mean of 220 million pounds of recoverable uranium oxide (U3O8 ) remaining as potential undiscovered resources in southern Texas. This estimate used a geology-based assessment method for Tertiary sandstone-hosted uranium deposits in the Texas Coastal Plain sedimentary strata (fig.1).

  1. Identification of remaining oil resource potential in the Frio Fluvial/Deltaic Sandstone play, South Texas

    SciTech Connect

    Holtz, M.H.; McRae, L.E.; Tyler, N.

    1994-05-01

    The Frio Fluvial/Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas has produced nearly 1 billion stock tank barrels (BSTB) of oil, yet still contains about 1.2 BSTB of unrecovered mobile oil and an even greater amount of residual oil resources (1.5 BSTB). More than half of the reservoirs in this depositionally complex play have been abandoned, and large volumes of oil may remain unproduced. Interwell-scale geological facies models of Frio fluvial/deltaic reservoirs will be combined with engineering assessments and geophysical evaluations in order to characterize Frio fluvial/deltaic reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. Reservoir attribute data were statistically analyzed from oil and gas fields throughout the geographic area covered by the Frio Fluvial/Deltaic Sandstone oil play. General reservoir attributes analyzed in detail included porosity, initial water saturation, residual oil saturation, net pay, reservoir area, and fluid characteristics. Statistical analysis of variance demonstrated no difference between oil reservoir attributes and gas reservoir attributes. Probability functions that describe attribute frequency distributions were determined for use in risk adjusting resource calculations. The oil play was found to contain significant volumes of remaining oil. The volumetric probability distribution between 5- and 95-percent probability for original oil in place ranges from 3.8 to 5.6 BSTB, original mobile oil in place ranges from 2.5 to 3.6 BSTB, and residual oil ranges from 1.5 to 2.3 BSTB. The untapped oil resource may be 10 percent of the original oil in place, or 380 million stock tank barrels.

  2. A submarine welded ignimbrite-crystal-rich sandstone facies association in the Cambrian Tyndall Group, western Tasmania, Australia

    NASA Astrophysics Data System (ADS)

    White, Matthew J.; McPhie, Jocelyn

    1997-04-01

    Three occurrences of rhyolitic welded ignimbrite are intercalated within a submarine, below-storm-wave-base sedimentary succession in the Cambrian Tyndall Group, Mount Read Volcanics, western Tasmania. These occurrences are closely associated with very thick crystal-rich sandstone facies that is present at this stratigraphic level throughout the Tyndall Group. This facies is interpreted to comprise deposits from syn-eruptive, crystal-rich, submarine sediment gravity flows that were generated by interaction of subaerial pyroclastic flows with seawater. Removal of fine ash and pumice from the submarine flows by hydraulic sorting and flotation resulted in marked crystal enrichment in the deposits. Rapid, essentially syn-eruptive aggradation of crystal-rich sand led to temporary shoaling so that in some cases, subsequent pyroclastic flows deposited welded ignimbrite in shallow marine or possibly subaerial settings (e.g., Zig Zag Hill welded ignimbrite). Breccia units composed of welded ignimbrite clasts and crystal-rich matrix (e.g., Comstock and Anthony Road ignimbrite breccias) imply that some welded ignimbrite was submerged, providing clasts to syn-eruptive, submarine, crystal-rich sediment gravity flows. One example of welded ignimbrite (Cradle Mountain Link Road) may have been deposited in an entirely below-storm-wave-base environment. The distinctive facies association of welded ignimbrite, crystal-rich sandstone and ignimbrite-clast breccia in the Tyndall Group exemplifies the submarine record of a major rhyolitic explosive eruption in the source volcanic terrane.

  3. Deposition of the Woodbine-Eagleford sandstones, Aggieland field, Brazos County, Texas

    SciTech Connect

    Dedominic, J.R.

    1988-01-01

    Sandstones of the Upper Cretaceous Woodbine-Eagleford interval produce oil from a stratigraphic trap at Aggieland field. The reservoir has an overall north-south trending, ovate morphology and is composed of two elongate bodies. The sandstones are thin with an average net thickness of 16 ft (4.9 m). Grain size generally increases upward, ranging from 0.15 mm (fine grained) to 0.30 mm (medium grained). The sandstones are composed of 47% quartz, 43% matrix and are classified as a lithic greywacke. Due to the high percentage of matrix and poor sorting, permeability values are low, averaging 0.09 md. Porosity ranges from 8.6 to 17.6 percent. Based on sedimentary structures, four individual facies can be defined: (1) a massive, structureless facies, which contains numerous shale and oolitic classes; (2) a rippled facies with thinly interbedded shale laminations; (3) a thin, quartz-rich, cross-bedded facies; and (4) a bioturbated, shaly sand facies. The sandstones are encased within marine shales and were transported to a middle- to outer-shelf location by a combination of turbidity, storm and tidal currents. The eastern edge of the reservoir is truncated and unconformably overlain by the Austin Chalk. This truncation resulted from submarine erosion due to a deep seated salt uplift, which also influenced the paleotopography and deposition of the sands. The lowermost massive, clast rich facies was deposited by debris/gravity flows associated with the paleotopographic high created by the uplift. The upper portion of the sandstone was deposited as a marine bar associated with either a break in slope or intrashelf basin.

  4. Sedimentary facies and petrophysical characteristics of cores from the lower Vicksburg gas reservoirs, McAllen Ranch field, Hidalgo County, Texas

    SciTech Connect

    Langford, R.P.; Maguregui, J. ); Howard, W.E.; Hall, J.D. )

    1990-09-01

    As part of an effort funded by the Gas Research Institute, the Department of Energy, and the State of Texas, and with the cooperation of Shell Oil Co., sandstones in the Vicksburg S (Oligocene) reservoir were cored in the McAllen Ranch gas field in the A. A. McAllen B- 17 and B- 18 wells. Detailed correlation of the cores with petrophysical data illustrates the controls of deposition and diagenesis on reservoir quality. The cores were drilled using oil-based mud, and special care in handling minimized evaporation. Core-derived water saturations were compared with log-calculated water saturations. Special core analyses of cementation factor, saturation exponent, and relative permeability were performed. Thin-section petrography and X-ray diffraction were used to determine mineralogy. The cores consist of prodelta and delta-front facies. Permeability and porosity generally increase with increasing grain size and are greatest in 1 to 2 ft thick zones within massive and laminated beds in the uppermost delta front. Porous intervals increase in abundance upward within the delta-front sandstones. Permeability variation over two orders of magnitude within the reservoir sands corresponds to diagenetic facies within the core. High permeability occurs only within thin bands. Trough cross-stratified sandstone is commonly porous only near the tops of the foresets. Differences in the character of the microresistivity curve of the high-resolution dipmeter log correlate with differences in cementation and with different depositional facies within the cores. Comparison of microresistivity logs and cores allows extrapolation of facies and cement characteristics and resulting reservoir properties to uncored intervals with the objective of maximizing recovery of natural gas.

  5. Upper Permian (Guadalupian) facies and their association with hydrocarbons - Permian basin, west Texas and New Mexico

    SciTech Connect

    Ward, R.F.; Kendall, C.G.S.C.; Harris, P.M.

    1986-03-01

    Outcrops of Guadalupian sedimentary rocks in the Permian basin of west Texas and southeastern New Mexico are a classic example of the facies relationships that span a carbonate shelf. In the subsurface, these rocks form classic hydrocarbon-facies taps. Proceeding from basin to the updip termination of the shelf, the facies are (1) deep-water basin, (2) an apron of allochthonous carbonates, (3) carbonate shelf margin or reef, (4) carbonate sand flats, (5) carbonate barrier islands, (6) lagoon, and (7) coastal playas and supratidal salt flats (sabkhas). Over a half century of exploration drilling has shown that hydrocarbons in the Permian rocks of the Permian basin have accumulated at the updip contact of the lagoonal dolomites and clastics with the coastal evaporites, and in the basinal channel-fill clastics. The shelf marginal (reef) facies contain cavernous porosity, but commonly are water saturated. These facies relationships and hydrocarbon occurrences provide an exploration model with which to explore and rank hydrocarbon potential in other carbonate provinces. 16 figures, 3 tables.

  6. Lower Cretaceous barrier reef and outer shelf facies, Sligo Formation, south Texas

    SciTech Connect

    Kirkland, B.L.; Lighty, R.G.; Rezak, R.; Tieh, T.T.

    1987-09-01

    Along the south Texas margin, a vast carbonate-shelf complex with an extensive barrier-reef system and abundant shallow-lagoon and skeletal-shoal deposits existed during the Aptian to Albian. The Sligo Formation represents more than 609.6 m (2000 ft) of deposition along this margin. Facies types along the shelf edge were quantitatively delineated by cluster analysis of detailed point-count data from 90 thin sections of whole cores from five wells. In addition, studies of 42.6 m (140 ft) of core slabs and thin sections of well cuttings from four other wells were used to establish a regional depositional model. Along the Sligo shelf edge, three major facies occur: reef or reef rubble (two subfacies), back reef (three subfacies), and lagoonal (two subfacies). Reef facies are dominated by caprinids and also contain solenoporid algae, stromatoporoids, and an assortment of corals. Behind the reef, a spectrum of extensive back-reef deposits interfinger with shallow (< 5 m), lagoonal sediments. Farther behind the shelf-margin reef complex, along the outer shelf, benthic foraminifera, peloids, and ooids were deposited in high-energy shoals, and are interbedded with low-energy lagoonal sediments. The two types of buildups probably existed along the Sligo shelf margin and the equivalent Cupido shelf margin to the south: (1) wave-resistant coral-caprinid-stromatoporid barrier reefs (adjacent to restricted lagoonal facies), and (2) low-lying rudist banks (adjacent to diverse, washed lagoonal facies).

  7. Assessment of in-place solution methane in tertiary sandstones: Texas Gulf Coast

    SciTech Connect

    Gregory, A.R.; Dodge, M.M.; Posey, J.S.; Morton, R.A.

    1981-01-01

    The higher prices obtained for commercial natural gas in recent years have stimulated interest in methane-saturated formation waters of sandstone reservoirs in the Texas Gulf Coast as a potential alternative source of energy. The objective of this project was to appraise the total volume of in-place methane dissolved in formation waters of deep sandstone reservoirs of the onshore Texas Gulf Coast within the stratigraphic section extending from the base of significant hydrocarbon production (8000 ft) to the deepest significant sandstone occurrence. Factors that must be evaluated to determine the total methane resource are reservoir bulk volume, porosity, and methane solubility. The latter is controlled by the temperature, pressure, and salinity of formation waters. Regional assessment of the volume and distribution of potential sandstone reservoirs was made from a data base of 880 electrical well logs, from which a grid of 24 structural dip cross sections and 4 strike cross sections was constructed. These cross sections extend from near the Wilcox outcrop to the coastline. Reservoir bulk volume was determined by mapping the structural and stratigraphic framework of Tertiary sandstone units. Structural and stratigraphic boundaries were used to divide the Texas Gulf Coast into 24 subdivisions. Methane content in each of nine formations or divisions of formations was determined for each subdivision. The total in-place methane for Tertiary sandstones below 8000 ft in the Texas Gulf Coast was found to be 690 TCF./sup 2/ The total in-place methane for effective Tertiary sandstones (sandstone units greater than 30 ft thick) below 8000 ft was 325 TCF.

  8. Thermal conductivity of Wilcox and Frio sandstones in South Texas (Gulf of Mexico basin)

    SciTech Connect

    McKenna, T.E.; Sharp, J.M. Jr.; Lynch, F.L.

    1996-08-01

    Thermal conductivity and petrographic data are presented for verifying mechanistic models of sandstone thermal conductivity. We measured the thermal conductivity of 83 Wilcox and Frio sandstones from south Texas in the Gulf of Mexico sedimentary basin, and correlated conductivity to petrographic variables. Thermal conductivities of water-saturated sandstones at 20{degrees}C (68{degrees}F) and 3 MPa (435 psi) were measured on core plugs using a divided-bar apparatus. Thermal conductivity ranges from 2.06 to 5.73 W/m/K over a porosity range of 2.4 to 29.6%. Because of a higher quartz content, Wilcox sandstones at a given porosity are more conductive than Frio sandstones. A grain-matrix conductivity of 5.9 W/m/K is estimated for Wilcox sandstones; matrix conductivity is adequately described with an arithmetic mixing model. Thermal conductivities of clean (<25% clay) sandstones can be described by a multilinear function of decreasing thermal conductivity with increasing porosity and increasing thermal conductivity with quartz content. For clean, quartzose (>35% of the solids) sandstones, the dependence on quartz content can be dropped and thermal conductivities can be predicted with a linear decrease in conductivity with increasing porosity. These sandstones appear isotropic with respect to thermal conductivity.

  9. Analysis of Texas Gulf Coast Tertiary sandstones to delineate areas of high-quality geopressured geothermal reservoirs

    SciTech Connect

    Loucks, R.G.; Dodge, M.M.

    1980-06-01

    In Lower and in parts of Middle and Upper Texas Gulf Coast the Wilcox sandstones are relatively well consolidated, but in other parts of Middle and Upper Texas Gulf Coast they show a reversal toward increased porosity at depth. The Wilcox Group has good reservoir potential for geopressured geothermal energy in the Middle Texas Gulf Coast and possibly in adjacent areas, but other Wilcox areas are marginal. Vicksburg sandstones have the poorest reservoir quality of sandstones of any formation and are not prospective for geothermal energy. Reservoir quality in the Frio Formation increases from very poor to lowermost Texas, to marginal into the Middle Texas Gulf Coast, and to good through the Upper Texas Gulf Coast. This increase in reservoir quality correlates to changes in rock composition and cementation. The Frio Formation in the Upper Texas Gulf Coast has the best deep-reservoir quality of any unit along the Texas Gulf Coast. 18 references.

  10. Sedimentary facies and reservoir characteristics of Cretaceous J Sandstone at Torrington field (North), Goshen County, Wyoming, exploration and development implications

    SciTech Connect

    Mikesh, D.L.; Lafollette, R.F.

    1983-08-01

    Torrington field (North) is productive from the Lower Cretaceous J sandstone in the Wyoming portion of the Denver basin. The trapping mechanism is stratigraphic, with reservoir sandstones enveloped laterally and updip by shale-dominated lithofacies. The field has produced 13,000 bbl of oil from two wells since its discovery in late 1981. Three major sedimentary environments and their associated facies, characteristic of a meandered fluvial system, occur within the J interval in the area: abandoned channel, point bar(s), and interfluvial plain. Production at both Torrington (North) and Torrington is from reservoir development within point bar deposits. Cores of the J point bar at Torrington (North) show that it is comprised primarily of very fine to fine-grained quartzarenites and sublitharenites. Sedimentary structures observed in the cores include burrowing and bioturbation, high-angle plane-parallel cross-bedding, discontinuous wavy shale laminae, climbing ripples, and truncated laminae. Although excellent hydrocarbon shows occur from the base to the top of the point bar, production appears to be confined to thin intervals of medium-grained quartzarenite found near the middle of the vertical sequence. Petrophysical reservoir characteristics of the J sandstone were established through examination of X-ray diffraction, scanning electron microscopy, thin-section petrography, and conventional core analysis data. Microporosity development and geometry also affect production. Field extension locations and an exploratory drill site have been established as a result of this study.

  11. Assessment of tight-gas resources in Canyon sandstones of the Val Verde Basin, Texas, 2016

    USGS Publications Warehouse

    Schenk, Christopher J.; Tennyson, Marilyn E.; Klett, Timothy R.; Mercier, Tracey J.; Brownfield, Michael E.; Gaswirth, Stephanie B.; Hawkins, Sarah J.; Leathers-Miller, Heidi M.; Marra, Kristen R.; Finn, Thomas M.; Pitman, Janet K.

    2016-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey assessed mean resources of 5 trillion cubic feet of gas and 187 million barrels of natural gas liquids in tight-gas assessment units in the Canyon sandstones of the Val Verde Basin, Texas.

  12. Environment of deposition of downdip Lower Wilcox sandstones, Provident City field, Lavaca County, Texas

    SciTech Connect

    Vest, S.W.

    1990-09-01

    The Lower Wilcox section at Provident City field produces dry gas from thin-bedded, silty sandstones, at depths of 12,500 to 14,100 ft (3,810 to 4,298 m). Cores show that sandstone cosets range 0.1 to 2.7 ft (0.03 to 0.82 m) and average 0.5 8 ft (0. 18 m) in thickness. Sedimentary structures within the cosets range upward from a massive unit (A) to a planar-laminated unit (B) to a ripple-laminated unit (C). The cosets have an average composition of lithic arkose and show textural grading indicative of deposition from turbidity flows. The sandstones lie within the Wilcox fault zone, downdip of the Colorado and Guadalupe deltas of the Rockdale Delta System. Regional stratigraphy and structural trends indicate that the sandstones were deposited in a deep marine environment. A growth fault, having approximately 1000 ft (3048 m) of throw at a depth of 12,300 ft (3750 m), bounds the field to the northwest and largely controls the distribution of lithofacies. Stacked, AB-type, turbidite cosets indicate channel facies. The M Sandstone was deposited as a constructional channel, with abrupt lateral grading to overbank facies, where turbidites of the BC- and C-type are dominant. The S Sandstone was deposited as a series of thin, constructional channels, mostly with turbidites of the AB- and ABC-type that are generally stacked, causing superimposed, dip-trending lobes on an otherwise strike-trending sandstone.

  13. Recent Advances in Characterizing Depositional Facies and Pore Network Modeling in Context of Carbon Capture Storage: An Example from the Cambrian Mt. Simon Sandstone in the Illinois Basin

    NASA Astrophysics Data System (ADS)

    Freiburg, J. T.; Nathan, W.; Best, J.; Reesink, A.; Ritzi, R. W., Jr.; Pendleton, J.; Dominic, D. F.; Tudek, J.; Kohanpur, A. H.

    2015-12-01

    In order to understand subsurface flow dynamics, including CO2 plume migration and capillary trapping, a diverse set of geologic properties within the reservoir, from the pore scale to the basin scale, must be understood and quantified. The uncertainty about site-specific geology stems from the inherent variation in rock types, depositional environments, and diagenesis. In collaboration with geocellular and multiphase modeling, detailed characterization of the Lower Mt. Simon Sandstone (LMSS), a reservoir utilized for carbon capture storage, is supporting data-driven conceptual models to better understand reservoir heterogeneity and its relationship to reservoir properties. This includes characterization of sedimentary facies and pore scale modeling of the reservoir The Cambrian-age Lower Mt. Simon Sandstone (LMSS) is a reservoir utilized for two-different carbon capture storage projects in the Illinois Basin, USA. The LMSS is interpreted to have formed in a braided river environment comprising a hierarchy of stratification, with larger scale depositional facies comprising assemblages of smaller scale facies. The proportions, geometries, length scales, and petrophysical attributes of the depositional facies, and of the textural facies they comprise, are being quantified. Based on examination of core and analog outcrop in adjacent areas, the LMSS is comprised of five dominant depositional facies, the most abundant facies being planar to trough cross-bedded sandstones produced by subaqueous sand dunes. This facies has the best reservoir conditions with porosity up to 27% and permeability up to 470 mD. Three-dimensional pore network modeling via micro computed tomography of this facies shows well-connected and unobstructed pore throats and pore space. This presentation will outline the depositional heterogeneity of the LMSS, its relationship to diagenetic fabrics, and its influence on fluid movement within the reservoir.

  14. Analysis of sedimentary facies and petrofacies of lower Morrowan-upper Chesterian sandstones, Anadarko Basin, Oklahoma

    USGS Publications Warehouse

    Keighin, C. William; Flores, Romeo M.

    1989-01-01

    Three major lithofacies have been identified within the Morrow (Pennsylvanian) and Springer (Pennsylvanian-Mississippian) units, in core from 30 drill holes ranging from the Oklahoma Panhandle to the southwestern portion of the Anadarko basin. The study included inspection of ~6,500 ft of core, examination of ~100 thin sections, and a scanning-electron-microscope study of butts of the material used for thin-section preparation. The lithofacies identified are (1) fluvial-influenced coastal, which includes the deltaic facies described by Swanson (1979), (2) tidal-influenced nearshore, and (3) mixed, which shows mixed tidal and nontidal marine influence. Our interpretation is supported by the investigations of Moore (1979), Haiduk (1987), and Swanson (1979). The fluvial-influenced coastal facies is restricted to the northwestern (Panhandle) portion of the Anadarko basin.

  15. Depositional systems and structural controls of Hackberry sandstone reservoirs in southeast Texas

    SciTech Connect

    Ewing, T.E.; Reed, R.S.

    1984-01-01

    Deep-water sandstones of the Oligocene-age Hackberry unit of the Frio Formation contain significant quantities of oil and gas remain potentially one of the most productive exploration targets in southeast Texas. The Hackberry is a wedge of sandstone and shale containing bathyal fauna that separates upper Frio barrier-bar-strandplain sandstones from lower Frio neritic shale and sand. Major Hackberry sandstones lie atop a channeled unconformity that forms the base of the unit. Sandstones in a typical sand-rich channel at Port Arthur field grade upward from a basal, confined channel-fill sandstone to more widespread, broad, fan-channel deposits. Topmost are proximal to medial fan deposits and overbank turbidite deposits. The sequence suggests that Hackberry sandstones were laid down by an onlapping submarine canyon-fan complex deposited in canyons that eroded headward into the contemporaneous Frio barrier system. Regional maps and seismic interpretations outline a network of sand-filled channels extending from the barrier toward the southeast.

  16. Lower Permian facies of the Palo Duro Basin, Texas: depositional systems, shelf-margin evolution, paleogeography, and petroleum potential

    SciTech Connect

    Handford, C.R.

    1980-01-01

    A Palo geological study suggests that potential hydrocarbon reservoirs occur in shelf-margin carbonates, delta-front sandstones, and fan-delta arkoses. Zones of porous (greater than 10 percent) dolomite are concentrated near shelf margins and have configurations similar to productive Lower Permian shelf-margin trends in New Mexico. Delta-front sandstones (log-computed porosity of 18 to 25 percent) are similar to producing deltaic sandstones of Morris Buie-Blaco Fields in North-Central Texas. Porous (18 percent) fan-delta sandstones along the south flank of the Amarillo Uplift may form reservoirs similiar to that of the Mobeetie Field on the north side of the Amarillo Uplife in Wheeler County, Texas. Potential hydrocarbon source beds occur in slope and basinal environments. Total organic carbon generally ranges from 1 to 2.3 percent by weight and averages 0.589 percent by weight.

  17. Depositional setting, structural style, and sandstone distribution in three geopressured geothermal areas, Texas Gulf Coast

    SciTech Connect

    Winker, C.D.; Morton, R.A.; Ewing, T.E.; Garcia, D.D.

    1981-10-01

    Three areas in the Texas Gulf Coast region with different depositional settings, structural styles, and sandstone distribution were studied with well log and seismic data to evaluate some of the controls on subsurface conditions in geopressured aquifers. Structural and stratigraphic interpretations were made primarily on the basis of well log correlations. Seismic data confirm the log interpretations but also are useful in structure mapping at depths below well control.

  18. Petrography and diagenesis of Eagle Mills sandstones, subsurface - Northeast Texas and southwest Arkansas

    SciTech Connect

    Dawson, W.C.; Callender, C.A. )

    1991-03-01

    The Eagle Mills Formation (Triassic-Jurassic) has been penetrated by several deep wells (12,000 to 18,000 ft) in northeast Texas and southwest Arkansas. It consists of green, red, and pink conglomeratic lithic arenites and fine- to coarse-grained feldspathic arenites, interbedded with red and greenish gray shales and siltstones. Lithic arenites contain basalt, chert, quartzite, and dolomite rock fragments; plagioclase is the predominant feldspar. All Eagle Mills sandstones have low textural and mineralogic maturities. Eagle Mills red beds and associated intrusive igneous rocks (diabase and basalt dikes and sills) represent the fillings of grabens or rift basins that actively subsided during deposition (in alluvial, fluvial-deltaic, and lacustrine paleoenvironments). Eagle Mills lithic and feldspathic sandstones have undergone a complex diagenetic history, including chlorite cementation (pore linings and pore fillings), compaction, quartz and feldspar overgrowths, dolomite cementation, chloritization and albitization of detrital feldspars, local dissolution of framework grains (igneous lithics and feldspars), precipitation of kaolinite, late Fe-calcite cementation, and saddle dolomite formation. Cement mineralogies are strongly correlative with lithofacies. Lithic sandstones contain the highest frequency of chlorite cements, whereas feldspathic sandstones are preferentially cemented with carbonates and anhydrite; quartz and feldspar overgrowths are ubiquitous. The suite of authigenic minerals in Eagle Mills sandstones records progressive burial into a deep, high-temperature (120-150C), semiclosed, diagenetic regime.

  19. Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies

    PubMed Central

    Harding, Sherie C.; Nash, Barbara P.; Petersen, Erich U.; Ekdale, A. A.; Bradbury, Christopher D.; Dyar, M. Darby

    2014-01-01

    The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe3+0.89 Mg0.45 Al0.67 Fe2+0.30 Ti0.01 Mn0.01) Σ = 2.33 (Si1.77 Al0.23) O5.00 (OH)4.00. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions. PMID:24503875

  20. Mineralogy and geochemistry of the main glauconite bed in the Middle Eocene of Texas: paleoenvironmental implications for the verdine facies.

    PubMed

    Harding, Sherie C; Nash, Barbara P; Petersen, Erich U; Ekdale, A A; Bradbury, Christopher D; Dyar, M Darby

    2014-01-01

    The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe(3+) 0.89 Mg0.45 Al0.67 Fe(2+) 0.30 Ti0.01 Mn0.01) Σ = 2.33 (Si1.77 Al0.23) O5.00 (OH)4.00. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions. PMID:24503875

  1. Diagenetic modification of Sm-Nd model ages in Tertiary sandstones and shales, Texas Gulf Coast

    SciTech Connect

    Awwiller, D.N.; Mack, L.E. )

    1991-04-01

    Sm-Nd model ages of sandstones and shales from the Oligocene Frio Formation of south Texas and the Paleocene-Eocene Wilcox Group of south-central Texas increase with increasing depth of burial. The sampling scheme employed minimizes, but does not eliminate, the possibility that these trends in depleted-mantle model ages (T{sub dm}) are due to detrital variability. Close correlation of these trends with diagenetic changes in the rock and evidence of rare earth element mobility preserved in the diagenetic products suggests that diagenesis has modified T{sub dm}. Diagenetic modification of T{sub dm} in Frio sandstone and Wilcox shale is due primarily to loss of radiogenic Nd, whereas increased {sup 147}Sm/{sup 144}Nd (Sm/Nd) produces elevated T{sub dm} in deeper Wilcox sandstones. The T{sub dm} of Frio shales does not change appreciably with depth, owing to the opposite effects on T{sub dm} of decreased Sm/Nd and decreased {epsilon}{sub Nd}(0). Loss of radiogenic Nd is due primarily to reactions involving unstable volcanic detritus, which is more abundant in Frio than in the Wilcox. Decreased Sm/Nd in authigenic illite, and consequent increased Sm/Nd in pore fluids, results in elevated T{sub dm} in Wilcox and Frio sandstones containing late-diagenetic cement, and in decreased Sm/Nd in deeper Frio shale. The similar T{sub dm} trends observed in both units, which have different detrital characteristics, suggest that modification of Sm-Nd model ages in siliciclastic rocks may be commonplace during burial diagensis.

  2. Carbonate facies and stratigraphic framework of middle Magdalena (middle Pennsylvanian), Hueco Mountains, west Texas

    SciTech Connect

    Lambert, L.L.; Stanton, R.J. Jr.

    1988-01-01

    The middle Magdalena of the Hueco Mountains, west Texas, is best exposed in the vicinity of Pow Wow Canyon, particularly along the western scarp of the range. It can be divided into two major depositional sequences, the lowermost of which consists predominantly of alternating bank, interbank, and shoal deposits of Atokan age. These banks are low-relief accumulations of Donezella, with coeval slackwater skeletal wackestones and interbedded deposits of foraminiferal sands. A prominent zone of intertonguing Chaetetes biostromes punctuates the middle part of this sequence. The Desmoinesian sequence begins as a series of rubbly limestones in association with abundant silicified plant remains and is interpreted as a set of paleosols. These are overlain by argillaceous, low-diversity wackestones and packstones of lagoonal origin, followed by carbonates of more open-marine circulation with abundant corals and other stenotypic fossils. In turn, these deposits are succeeded by a sequence of phylloid algal banks that increase in resistance upward to where they represent strata of the upper Magdalena. At this locality, however, the upper Magdalena is very thin because it is truncated by the pre-Hueco unconformity which, so prominent at the head of the canyon, can now be traced to the western scarp. These deposits are directly analogous to subsurface reservoir facies of the same age on the opposite side of the Diablo uplift in the Permian basin and thus provide an opportunity to generate reservoir models based on extensive outcrop exposure.

  3. Clay mineralogy and its controls on production, Pennsylvanian upper Morrow sandstone, Farnsworth field, Ochiltree County, Texas

    SciTech Connect

    Munson, T.W. )

    1989-12-01

    Farnsworth field in Ochiltree County, Texas, is the most prolific upper Morrow oil field in the Anadarko basin, producing more than 36 million bbl of oil and 27 billion ft{sup 3} of gas since its discovery in 1955. The bulk of the production comes from an upper Morrow-aged sandstone locally referred to as the Buckhaults sandstone. The Buckhaults sandstone is a coarse to very coarse-grained, arkose to arkosic wacke. Grain-size distributions, sedimentary structure analysis, and sand-body geometry indicate that the Buckhaults was deposited in a fluvial-deltaic environment as distributary channel and distributary mouth-bar sands. Depositional strike is northwest to southeast. The source area for the Buckhaults sediments was primarily a plutonic igneous terrane, with a minor contribution from volcanic and reworked sedimentary rocks. The proposed source area is the Amarillo-Wichita uplift to the south. In addition, the Cimarron arch and/or Keyes dome to the west-northwest may also have contributed sediment to the study area. The large (average) grain size, the amount of feldspar present, and the overall immaturity of the Buckhaults sediments indicate a relatively short distance of transport. Detailed scanning electron microscopy and x-ray diffraction analysis of cores from the productive interval coupled with comparisons of varying completion practices across the field indicate a significant correlation between individual well performance, clay mineralogy, and completion technique.

  4. Regional geology of the low-permeability, gas-bearing Cleveland Formation, western Anadarko Basin, Texas Panhandle: Lithologic and depositional facies, structure, and sequence stratigraphy

    NASA Astrophysics Data System (ADS)

    Hentz, Tucker F.

    1992-09-01

    The Upper Pennsylvania (lower Missourian) Cleveland formation produces gas from low-permeability ('tight') sandstone reservoirs in the western Anadarko Basin of the northeastern Texas Panhandle. In the six-county region, these reservoirs had produced more than 412 Bcf of natural gas through December 31, 1989. Because of their typically low permeability, the Cleveland sandstones require acidizing and hydraulic fracture treatment to produce gas at economic rates. Since 1982, the Gas Research Institute has supported geological investigations throughout the United States to develop the scientific and technological knowledge for producing from low-permeability, gas-bearing sandstones. As part of the program and the GRI Tight Gas Sands project, the Bureau of Economic Geology has been conducting research on low-permeability sandstones in the Cleveland formation and on several other sandstone units of similar character in Texas and Wyoming.

  5. Depositional setting, structural style, and sandstone distribution in three geopressured geothermal areas, Texas Gulf Coast

    SciTech Connect

    Winker, C.D.; Morton, R.A.; Ewing, T.E.; Garcia, D.D.

    1983-01-01

    Three areas in the Texas Gulf Coastal Plain were studied using electric logs and seismic-reflection data to interpret their depositional and structural history and to compare their potential as geopressured-geothermal reservoirs. The Cuero study area, on the lower Wilcox (upper Paleocene) growth-fault trend, is characterized by closely and evenly spaced, subparallel, down-to-the-basin growth faults, relatively small expansion ratios, and minor block rotation. Distributary-channel sandstones in the geopressured lower Wilcox Group of the South Cook fault block appear to be the best geothermal aquifers in the Cuero area. The Blessing study area, on the lower Frio (Oligocene) growth-fault trend, shows wider and more variable fault spacing and much greater expansion ratios and block rotation, particularly during early Frio time. Thick geopressured sandstone aquifers are laterally more extensive in the Blessing area than in the Cuero area. The Pleasant Bayou study area, like the Blessing area, is on the Frio growth-fault trand, and its early structural development was similar rapid movement of widely spaced faults resulted in large expansion ratios and major block rotation. However, a late-stage pattern of salt uplift and withdrawal complicated the structural style. Thick geopressured lower Frio sandstone aquifers are highly permeable and laterally extensive, as in the Blessing area. In all three areas, geopressured aquifers were created where early, rapid movement along down-to-the-basin growth faults juxtaposed shallow-water sands against older shales, probably deposited in slope environments. Major transgressions followed the deposition of reservoir sands and probably also influenced the hydraulic isolation that allowed the build up of abnormal pressures. 26 refs., 49 figs., 8 tabs.

  6. Shelf margin bioherms and associated facies in the Lower Permian Hueco Group (Late Wolfcampian), Hueco Mountains, West Texas

    SciTech Connect

    Wahlman, G.P.; Tasker, D.R.; St. John, J.W.; Werle, K.J. )

    1992-01-01

    Late Wolfcampian phylloid algal/Tubiphytes biohermal complexes are exposed in three erosional oilers lying about 3 miles west of and parallel to the main Hueco Mountains in far West Texas. The biohermal complexes are located paleogeographically along the shelf margin between the Diablo Platform and Orogrande Basin. Based on fusulinids the shelf margin buildups correlate with well-bedded shelf carbonates of the type Hueco Group in the main Hueco Mountains. The phylloid algal/Tubiphytes shelf margin bioherms contain an upward shallowing facies succession, which, in ascending order, consists of: (1) phylloid algal wackestone-bafflestone, (2) phylloid algal-fusulinid bafflestone-packstone, and (3) Tubiphytes boundstone and Tubiphytes-fusulinid-phylloid algal packstone-grainstone. The crest of the southernmost outlier has a different type of bioherm that consists of nodular boundstones composed of calcisponges, encrusting bryozoans and laminar red algae. The shelf margin complexes prograded over slope facies of dark-gray cherty limestones, which generally lack skeletal fossils, but contain common ichnofossils in upper slope beds. Overlapping tongues and channels of lithoclastic-skeletal packstones and grainstones extend seaward from the phylloid algal/Tubiphytes bioherms into the dark-gray slope facies. Proximal backreef facies consist of mainly skeletal-peloidal packstones and wackestones. The Hueco Mountains outlier exposures are important because: (1) they confirm a Late Wolfcampian shelf margin with distinct topographic relief in the southern Orogrande Basin, and (2) they provide an easily accessible field laboratory where Wolfcampian shelf-to-basin facies relationships and shelf margin bioherms can be studied. Wolfcampian bioherms represent a significant stage in the evolutionary history of Late Paleozoic reef communities and form important petroleum reservoirs in the adjacent Permian Basin.

  7. Fluvial and deltaic facies and environments of the late permian back-reef shelves of the Permian Basin of Texas and New Mexico

    SciTech Connect

    Mazzullo, J. )

    1993-02-01

    The Artesia Group is a sequence of carbonates, evaporites, and clastics that was deposited across the back-reef shelves of the Permian Basin during late Permian time. There has been some controversy over the depositional environments of the clastic members of the Artesia Group and the role of sea level fluctuations in their accumulation. However, the results of a regional core study of the Queen Formation of the Artesia Group indicate that they were largely deposited in desert fluvial and deltaic environments during low-stands of sea level. Three fluvial-deltaic facies are recognized within the clastic members of the Queen. The first consists of medium to very find sandstones and silty sandstones with cross-beds, ripple cross-laminae, and planar and wavy laminae. This facies forms wavy sheets that thicken and thin along linear trends, and was deposited in sandy braided streams. The second facies consists of very find to fine sandstones, silty sandstones, and siltstones with ripple cross-laminae, planar and wavy laminae, cross-beds, clay drapes and pedogenetic cutans, as well as siltstones and silty mudstones with haloturbation structures and evaporite nodules. This facies forms thick planar sheets, and was deposited in fluvial sandflats and adjacent fluvial-dominated continental sabkhas. The third facies consists of cyclic deposits of haloturbated silty mudstones that grade into siltstones and very fine sandstones with crossbeds, planar and wavy laminae, haloturbation structures and evaporite nodules. Each cycle forms a lobate body that is bounded by carbonates or evaporites and which was deposited in sheet deltas that formed along the landward margins of a back-reef lagoon.

  8. Exploration potential and variations in shelf plume sandstones, Navarro group (Maestrichtian), east-central Texas

    SciTech Connect

    Patterson, J.E. Jr.; Scott, A.J.

    1984-04-01

    Fine-grained marine sandstones within the Kemp Clay of the Navarro Group (Maestrichtian) of east-central Texas were deposited on a muddy, shallow shelf by migrating sandbars. These sands were transported in traction from deltaic headlands by seaward-deflected coastal/shelf currents. The sand formed thin (3-20 ft; 1-6 m) arcuate belts (shelf sand plumes) which were 17-20 mi (27-32 km) wide and extended 27-30 mi (43-48 km) downdrift and 21-40 mi (34-64 km) onto the shelf. Orientation of the long axes of ridges, formed by the stacking of individual bars within the shelf sand plume, changes (from dip to strike-oriented downdrift) corresponding to the flow directions of the shelf currents. Southwestward, fair-weather reworking of these delta-supplied sands by shelf currents resulted in the down-current stratigraphic climbing of the migrating shelf-bar complexes. Onshore stratigraphic climbing in the landward parts of the plume complexes was related to storm activity. Current patterns and the resulting distribution of sand were influenced by the configuration of the shelf and the topographic relief inherited from previously deposited deltaic/shelf depositional platforms. Three variations of the basic shelf sandstone-plume model were recognized in the study area: (1) a rapidly deposited, immature plume, (2) an abandoned, current-reworked plume, and (3) a storm-modified, onshore-reworked plume. Each of these variants displays unique characteristics which influence their potential as hydrocarbon reservoirs.

  9. Geology and recognition criteria for sandstone uranium deposits in mixed fluvial-shallow marine sedimentary sequences, South Texas. Final report

    SciTech Connect

    Adams, S.S.; Smith, R.B.

    1981-01-01

    Uranium deposits in the South Texas Uranium Region are classical roll-type deposits that formed at the margin of tongues of altered sandstone by the encroachment of oxidizing, uraniferous solutions into reduced aquifers containing pyrite and, in a few cases, carbonaceous plant material. Many of the uranium deposits in South Texas are dissimilar from the roll fronts of the Wyoming basins. The host sands for many of the deposits contain essentially no carbonaceous plant material, only abundant disseminated pyrite. Many of the deposits do not occur at the margin of altered (ferric oxide-bearing) sandstone tongues but rather occur entirely within reduced, pyurite-bearing sandstone. The abundance of pyrite within the sands probably reflects the introduction of H/sub 2/S up along faults from hydrocarbon accumulations at depth. Such introductions before ore formation prepared the sands for roll-front development, whereas post-ore introductions produced re-reduction of portions of the altered tongue, leaving the deposit suspended in reduced sandstone. Evidence from three deposits suggests that ore formation was not accompanied by the introduction of significant amounts of H/sub 2/S.

  10. Secondary natural gas recovery in mature fluvial sandstone reservoirs, Frio Formation, Agua Dulce Field, South Texas

    SciTech Connect

    Ambrose, W.A.; Levey, R.A. ); Vidal, J.M. ); Sippel, M.A. ); Ballard, J.R. ); Coover, D.M. Jr. ); Bloxsom, W.E. )

    1993-09-01

    An approach that integrates detailed geologic, engineering, and petrophysical analyses combined with improved well-log analytical techniques can be used by independent oil and gas companies of successful infield exploration in mature Gulf Coast fields that larger companies may consider uneconomic. In a secondary gas recovery project conducted by the Bureau of Economic Geology and funded by the Gas Research Institute and the U.S. Department of Energy, a potential incremental natural gas resource of 7.7 bcf, of which 4.0 bcf may be technically recoverable, was identified in a 490-ac lease in Agua Dulce field. Five wells in this lease had previously produced 13.7 bcf from Frio reservoirs at depths of 4600-6200 ft. The pay zones occur in heterogeneous fluvial sandstones offset by faults associated with the Vicksburg fault zone. The compartments may each contain up to 1.0 bcf of gas resources with estimates based on previous completions and the recent infield drilling experience of Pintas Creek Oil Company. Uncontacted gas resources occur in thin (typically less than 10 ft) bypassed zones that can be identified through a computed log evaluation that integrates open-hole logs, wireline pressure tests, fluid samples, and cores. At Agua Dulce field, such analysis identified at 4-ft bypassed zone uphole from previously produced reservoirs. This reservoir contained original reservoir pressure and flowed at rates exceeding 1 mmcf/d. The expected ultimate recovery is 0.4 bcf. Methodologies developed in the evaluation of Agua Dulce field can be successfully applied to other mature gas fields in the south Texas Gulf Coast. For example, Stratton and McFaddin are two fields in which the secondary gas recovery project has demonstrated the existence of thin, potentially bypassed zones that can yield significant incremental gas resources, extending the economic life of these fields.

  11. Diagenesis of sandstones at shale contacts and diagenetic heterogeneity, Frio Formation, Texas

    SciTech Connect

    Sullivan, K.B.; McBride, E.F. )

    1991-01-01

    Diagenetic trends near sandstone/shale contacts were studied in 12 cored sequences from four wells between depths of 5200 and 15,700 ft (1585 and 4785 m) to evaluate the heterogeneity of diagenetic processes on a local scale and to evaluate the hypothesis that reactive aqueous fluids and components for cements in sandstones were derived from adjacent shales. The only evidence suggesting that diagenetic components in sandstones were derived from immediately adjacent shales is an increase in chlorite cement in sandstones toward contacts with shale beds for two of three contacts appropriate for study. Secondary pores and cements of quartz, carbonate, and kaolinite do not correlate with proximity to shale beds, but have a preference for sandstones that had relatively high initial porosities and permeabilities. Thus, the flux of formation water and probably long-distance transportation of diagenetic components were more important influences on reservoir quality of sandstones than was the local availability of components. Multiple regression of 22 independent variables indicates that the best predictors of secondary porosity are kaolinite cement and intergranular porosity. Sandstone sequences are extremely heterogeneous in the distribution of total thin section porosity, secondary porosity, and quartz and carbonate cements; in addition, they have significant variations in the abundance of kaolinite and chlorite cements. Mass balance calculations for silica and aluminum indicate silica was imported to and aluminum was exported from the sandstones.

  12. Contrasting evolutionary patterns of Lower Permian shelf and basinal facies, Midland basin, Texas

    SciTech Connect

    Mazzullo, S.J.; Reid, A.M.

    1987-05-01

    The evolution of carbonate and siliciclastic shelf-to-basin depositional systems of the Lower Permian in the Midland basin was influenced by eustatic fluctuations, changing shelf-margin biota, and concurrent tectonism. The development of these systems from Wolfcampian to Leonardian time (28-m.y. duration) involved seven distinct phases that are recognized seismically as third and lesser order cycles. These phases are (1) highstand progradational shelf carbonate packages, separated by low-stand deltaic and basinal shales, deposited during relatively long-term eustatic cycles (early Wolfcampian); the component carbonate systems evolved from ramps to distally steepened ramps associated with nonframe-building algal reefs and grainstones, with little resedimented foreshelf detritus; (2) dominantly carbonate deposition during the middle and early late Wolfcampian, with construction of offlapping (but laterally juxtaposed) progradational shelves with steep platform margins deposited during a lengthy period of stillstand and/or slow submergence; dolomitized platform-margin facies are composed of marine-cemented, sponge-algal reefs and grainstones, with resedimented carbonate megabreccia to micrite channels and lobes in the contiguous shale basin; (3) shelf emergence and erosion during a major late middle(.) to late Wolfcampian lowstand contemporaneous with basinwide tectonism, with mass wastage into the basin of the terminal Wolfcampian platform-margin carbonate section; (4) regional transgression and black shale deposition followed by a repeat of Phase 2 type systems in the latest Wolfcampian to earliest Leonardian but under arid conditions; rapid vertical platform margin accretion by dolomitized, marine-cemented, sponge-algal-coral reefs and grainstones, and deposition of thick foreshelf megabreccia wedges, aprons, channels, and lobes;

  13. Reservoir characteristics of Lower Wilcox Sandstones, Lobo Trend, Webb and Zapata Counties, Texas

    SciTech Connect

    Henke, K.A.

    1985-02-01

    To date, over 340 bcf of gas have been produced from the Lobo sandstones in the Laredo field area at depths of less than 10,000 ft (3050 m). Gas accumulation is controlled by faulting and erosional truncation. The resulting structural complexity has made accurate prediction of reservoir sandstones difficult. Cored sections display repetitive ordered sequences of sedimentary structures and textural and compositional gradations indicative of turbidity-current deposits. The reservoir sandstones were deposited as constructional channels having vertical and lateral variation from channel-fill to channel-margin to overbank deposits. Channel-fill units are 2-10 ft (0.61-3.05 m) thick and composed of AB, AE, and ABE bedsets. Channel-margin units are 1-3 ft (0.31-0.92 m) thick and contain thinner, more complete ABC, ABE and ABCE sequences. Overbank deposits consist of highly bioturbated, thinly interbedded sandstones and shales. Sandstones are feldspathic litharenites that have 15% matrix and 15% calcite cement. Porosities average 16% and permeabilities range from 0.54 to 12 md, decreasing with increased matrix, cement, and bioturbation. The channel-fill sandstones are linear, dip-trending bodies less than 3000 ft (915 m) wide, which bifurcate downdip into distributary channels. High-intensity, small-scale, soft-sediment deformation indicates the sandstones were deposited in an unstable outer-shelf to upper-slope environment. A slumped, dip-trending channel-fill interpretation for the Lobo sandstones provides a mechanism for sediment transport beyond the present downdip limits of the trend.

  14. Maturation of organic matter in Paleocene-Eocene Wilcox group south Texas: relationship to clay diagenesis and sandstone cementation

    SciTech Connect

    Jenden, P.D.; Kaplan, I.R.

    1984-04-01

    Thirty-three mudstone core and cuttings samples ranging in depth of 1.6-4.7 km (5200-15,400 ft) and in temperature from 80/sup 0/ to 210/sup 0/C (175-410/sup 0/F) were obtained from wells in south Texas. The results of closed-system pyrolyses and bitumen and kerogen analyses are related to available data on clay mineralogy and sandstone cement. This study examines the diagenesis of Wilcox organic matter, the migration of hydrocarbons, and the importance of organically derived CO/sub 2/ in sandstone cementation. The samples average 1% TOC, contain type 111 kerogen, and generally show bitumen contents less than or equal to about 150 mg/gC. Modeling indicates that primary migration of methane and light hydrocarbons in aqueous solution is capable of producing giant (greater than or equal to 1 tcf) gas and condensate fields. Because hydrocarbon generation does not occur until after the main stage of illitization, smectite accounts for less than 25% of the total water involved. Pyrolysis experiments indicate that as much as 150 mg/gC CO/sub 2/ may be liberated by Wilcox organic matter during diagenesis to present-day temperatures of 100/sup 0/C (212/sup 0/F). The main zone of oil generation occurs at subsurface temperatures of 95..pi..-125/sup 0/C (203/sup 0/-257/sup 0/F). The timing of these processes suggest that CO/sub 2/ could lay an important role in creating secondary sandstones porosity for hydrocarbon migration. The delta/sup 13/C values indicate that 25% of the carbonate cement present in Wilcox sandstones may originate from decomposition and diagenesis of organic matter.

  15. Carrizo-upper Wilcox depositional systems and their relation to updip oil production in South Texas

    SciTech Connect

    Hamlin, H.S.

    1983-05-01

    In the Rio Grande embayment of S. Texas, the Carrizo-Upper Wilcox interval consists of 2 fluvial- coastal plain depositional systems that grade downdip into several deltaic complexes. The bedload channel system is dominated by laterally coalesced, stacked fluvial channel sandstones. Shales are minor and laterally discontinuous. The mixed alluvial system consists of a more typical suite of coastal plain facies. Channel sandstones tend to be isolated and surrounded by overbank shales. Total-interval isopach patterns, sandstone geometries, and facies distributions indicate that fluvial systems were converging upon the embayment from the west, northwest, and north. Petroleum production in the updip portion of the Carrizo-Upper Wilcox interval is influenced by the distribution of the depositional systems and their component facies. Although most of the traps are structural, the geometries and internal characteristics of the reservoir sandstones are facies-dependent and affect field size and quality.

  16. Relationships of Bexar shale, Hensel sandstone, and Hensel dolomite (basal upper Trinity, Comanchean Cretaceous) in south-central Texas

    SciTech Connect

    Amsbury, D.L.

    1984-04-01

    The Bexar Shale has been considered the offshore equivalent of the Cow Creek Limestone, the overlying Hensel sandstone, or of the disconformity between them in outcropping sections. Cores and outcrops in Comal, Kendall, and northern Bexar Counties preserve calcitic and dolomitic caliche in the top of the Cow Creek Limestone. Above the caliche is 8-16 m(25-50 ft) of laminated or bioturbated, dolomitic siltstone and silty dolomite (Hensel dolomite). Dolomite is euhedral and silt-sized. The lower part contains collophane grains and oyster shells replaced partly by chalcedony. Carbonate grains within the upper part include angular and well-rounded mollusk and echinoid fragments; many are pyritic and coated by glauconite. Terrigenous grains in Hensel dolomite grade upward from silt to coarse subarkose sand from central Texas. In southern Bexar County, about 35 m (115 ft) of silt-, clay-, and calcite-mudstone referable to the Bexar Shale sharply overlie shallow marine Cow Creek Limestone, and grade abruptly upward into about 7 m (23 ft) of Hensel dolomite. Dolomite is overlain by calcarenite of the Glen Rose Formation containing subarkose sand grains. Similar distinctive sand grains occur in well cuttings of basal Glen Rose beds northeastward through Travis County. The Bexar represents a flood of clay-sized sediment from a distant source, spread across the San Marcos arch during a rapid transgression. Slightly younger sand, silt, and local clay of the Hensel sandstone were eroded from central Texas by a few flash floods during a major period of caliche formation in the area.

  17. Strategies for reservoir characterization and identification of incremental recovery opportunities in mature reservoirs in Frio Fluvial-Deltaic sandstones, south Texas: An example from Rincon Field, Starr County. Topical report

    SciTech Connect

    McRae, L.; Holtz, M.; Hentz, T.

    1995-11-01

    Fluvial-deltaic sandstone reservoirs in the United States are being abandoned at high rates, yet they still contain more than 34 billion barrels of unrecovered oil. The mature Oligocene-age fluvial-deltaic reservoirs of the Frio Formation along the Vicksburg Fault Zone in South Texas are typical of this class in that, after more than three decades of production, they still contain 61 percent of the original mobile oil in place, or 1.6 billion barrels. This resource represents a tremendous target for advanced reservoir characterization studies that integrate geological and engineering analysis to locate untapped and incompletely drained reservoir compartments isolated by stratigraphic heterogeneities. The D and E reservoir intervals of Rincon field, Starr County, South Texas, were selected for detailed study to demonstrate the ability of advanced characterization techniques to identify reservoir compartmentalization and locate specific infield reserve-growth opportunities. Reservoir architecture, determined through high-frequency genetic stratigraphy and facies analysis, was integrated with production history and facies-based petrophysical analysis of individual flow units to identify recompletion and geologically targeted infill drilling opportunities. Estimates of original oil in place versus cumulative production in D and E reservoirs suggest that potential reserve growth exceeds 4.5 million barrels. Comparison of reservoir architecture and the distribution of completions in each flow unit indicates a large number of reserve-growth opportunities. Potential reserves can be assigned to each opportunity by constructing an Sooh map of remaining mobile oil, which is the difference between original oil in place and the volumes drained by past completions.

  18. Facies and diagenesis of Triassic (Austrian alpine) and upper Permian (New Mexico-Texas) platform-margin carbonates: a comparison

    SciTech Connect

    Mazzullo, S.J.; Lobitzer, H.

    1988-02-01

    Platform-margin carbonates of the Austrian Middle and basal Upper Triassic (Carnian) (Wettersteinkalk) and Upper Permian (Capitan reef, Guadalupian) are similar in terms of facies development, biota, and syndepositional diagenetic fabrics. These similarities are noteworthy because of their occurrence across the Permian-Triassic boundary, and the fact that these carbonates are distinct from younger (Upper Triassic Dachsteinkalk) depositional systems. The Upper Permian and Middle to basal Upper Triassic were deposited as subdued rimmed platforms with component lagoonal, reef-flat, reef, and fore-reef facies belts. The reef facies appear to represent upper slope marginal mounds, and consist mainly of sponges, solitary corals, Tubiphytes, and various encrusting biota; typically, this facies is pervasively marine cemented. The reef-flat facies consist of similarly lithified biograin-stones deposited in high-energy wave-base zones along the platform margins. By contrast, steep rimmed platforms with massive framework coral buildups and relatively less syndepositional marine cements dominate in Upper Triassic units (e.g., Dachsteinkalk, Steinplatte reef). Proximal fore-reef beds in the Upper Permian and Middle to basal Upper Triassic are characterized by carbonate-clast debris cemented by coarse crystalline carbonate. The precipitation of this cement (grossoolith) may have occurred during early shallow burial of the fore-reef beds. Similar depositional and diagenetic facies are poorly developed in the Upper Triassic, instead being represented mainly by bedded micrites.

  19. Log response as model for production: Deep Wilcox sandstones, Provident City Field, Lavaca County, Texas

    SciTech Connect

    Collins, J.L. )

    1989-09-01

    Log data, plotted on resistivity-porosity crossplots as a means of comparative analysis, defined a water saturation equation. Cutoffs of less than 50% salt water for commercially productive wells, 50-65% salt water for marginal wells, and more than 65% salt water for wet wells are applied using Rw = 0.1, a = 0.7, m = 1.90, and n = 2 in the standard Archie equation. Whole core taken from the 50-65% salt water interval in one producing well shows most of the reservoir porosity to be secondary, with a wide variety of clays suspended in the pore throats. A palinspastic structure map, constructed by omitting late faulting, revealed a simple downthrown rollover anticline. Net feet of section with salt water less than 50% (contoured for each of three S sandstone lobes) defined commercially productive limits of the reservoir and confirmed the timing of hydrocarbon migration into this structure. This definition implies gas migrated into secondary pore spaces that were created just prior to hydrocarbon formation and inhibited precipitation of clays in the main reservoir while off-structure pore throats contain water, gas, and mobile fine material. A recovery factor of 1,720 mcf/ac-foot was calculated for reservoirs with salt water less than 50%.

  20. [X-ray radiography as a method of detailing the analysis of sedimentary facies, based on example of the Cergowa sandstones (Flysch Carpathians)].

    PubMed

    Pszonka, Joanna; Wendorff, Marek; Jucha, Katarzyna; Bartynowska, Karolina; Urbanik, Andrzej

    2013-01-01

    The paper presents the X-ray radiography as a method useful for the visualization of sedimentary structures in macroscopically homogeneous rocks. The radiographic analysis presented here bases on the example the Cergowa turbidite sandstones. The applied technique reveals that some of the apparently homogeneus Cergowa sandstones possess internal sedimentary structure of cross-lamination, which reflects on the sedimentological interpretation of the depositional mechanisms of this rock unit. This is the first application of this method in research on the Carpathian Flysch sedimentation. PMID:23944113

  1. Analysis of Fault Permeability Using Mapping and Flow Modeling, Hickory Sandstone Aquifer, Central Texas

    SciTech Connect

    Nieto Camargo, Jorge E. Jensen, Jerry L.

    2012-09-15

    Reservoir compartments, typical targets for infill well locations, are commonly created by faults that may reduce permeability. A narrow fault may consist of a complex assemblage of deformation elements that result in spatially variable and anisotropic permeabilities. We report on the permeability structure of a km-scale fault sampled through drilling a faulted siliciclastic aquifer in central Texas. Probe and whole-core permeabilities, serial CAT scans, and textural and structural data from the selected core samples are used to understand permeability structure of fault zones and develop predictive models of fault zone permeability. Using numerical flow simulation, it is possible to predict permeability anisotropy associated with faults and evaluate the effect of individual deformation elements in the overall permeability tensor. We found relationships between the permeability of the host rock and those of the highly deformed (HD) fault-elements according to the fault throw. The lateral continuity and predictable permeability of the HD fault elements enhance capability for estimating the effects of subseismic faulting on fluid flow in low-shale reservoirs.

  2. Facies analysis and sequence stratigraphic framework of upper Campanian strata (Neslen and Mount Garfield formations, Bluecastle Tongue of the Castlegate sandstone, and Mancos shale), Eastern Book cliffs, Colorado and Utah

    USGS Publications Warehouse

    Kirschbaum, Mark A.; Hettinger, Robert D.

    2004-01-01

    Facies and sequence-stratigraphic analysis identifies six high-resolution sequences within upper Campanian strata across about 120 miles of the Book Cliffs in western Colorado and eastern Utah. The six sequences are named after prominent sandstone units and include, in ascending order, upper Sego sequence, Neslen sequence, Corcoran sequence, Buck Canyon/lower Cozzette sequence, upper Cozzette sequence, and Cozzette/Rollins sequence. A seventh sequence, the Bluecastle sequence, is present in the extreme western part of the study area. Facies analysis documents deepening- and shallowing- upward successions, parasequence stacking patterns, downlap in subsurface cross sections, facies dislocations, basinward shifts in facies, and truncation of strata.All six sequences display major incision into shoreface deposits of the Sego Sandstone and sandstones of the Corcoran and Cozzette Members of the Mount Garfield Formation. The incised surfaces represent sequence-boundary unconformities that allowed bypass of sediment to lowstand shorelines that are either attached to the older highstand shorelines or are detached from the older highstand shorelines and located southeast of the main study area. The sequence boundary unconformities represent valley incisions that were cut during successive lowstands of relative sea level. The overlying valley-fill deposits generally consist of tidally influenced strata deposited during an overall base level rise. Transgressive surfaces can be traced or projected over, or locally into, estuarine deposits above and landward of their associated shoreface deposits. Maximum flooding surfaces can be traced or projected landward from offshore strata into, or above, coastal-plain deposits. With the exception of the Cozzette/Rollins sequence, the majority of coal-bearing coastal-plain strata was deposited before maximum flooding and is therefore within the transgressive systems tracts. Maximum flooding was followed by strong progradation of

  3. Wilcox sandstone reservoirs in the deep subsurface along the Texas Gulf Coast: their potential for production of geopressured geothermal energy. Report of Investigations No. 117

    SciTech Connect

    Debout, D.G.; Weise, B.R.; Gregory, A.R.; Edwards, M.B.

    1982-01-01

    Regional studies of the lower Eocene Wilcox Group in Texas were conducted to assess the potential for producing heat energy and solution methane from geopressured fluids in the deep-subsurface growth-faulted zone. However, in addition to assembling the necessary data for the geopressured geothermal project, this study has provided regional information of significance to exploration for other resources such as lignite, uranium, oil, and gas. Because the focus of this study was on the geopressured section, emphasis was placed on correlating and mapping those sandstones and shales occurring deeper than about 10,000 ft. The Wilcox and Midway Groups comprise the oldest thick sandstone/shale sequence of the Tertiary of the Gulf Coast. The Wilcox crops out in a band 10 to 20 mi wide located 100 to 200 mi inland from the present-day coastline. The Wilcox sandstones and shales in the outcrop and updip shallow subsurface were deposited primarily in fluvial environments; downdip in the deep subsurface, on the other hand, the Wilcox sediments were deposited in large deltaic systems, some of which were reworked into barrier-bar and strandplain systems. Growth faults developed within the deltaic systems, where they prograded basinward beyond the older, stable Lower Cretaceous shelf margin onto the less stable basinal muds. Continued displacement along these faults during burial resulted in: (1) entrapment of pore fluids within isolated sandstone and shale sequences, and (2) buildup of pore pressure greater than hydrostatic pressure and development of geopressure.

  4. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in frio fluvial-deltaic sandstone reservoirs at South Texas. Annual report, October 1994--October 1995

    SciTech Connect

    Holtz, M.; Knox, P.; McRae, L.

    1996-02-01

    The Frio Fluvial-Deltaic Sandstone oil play of South Texas has produced nearly 1 billion barrels of oil, yet it still contains about 1.6 billion barrels of unrecovered mobile oil and nearly the same amount of residual oil resources. Interwell-scale geologic facise models of Frio Fluvial-deltaic reservoirs are being combined with engineering assessments and geophysical evaluations in order to determine the controls that these characteristics exert on the location and volume or unrecovered mobile and residual oil. Progress in the third year centered on technology transfer. An overview of project tasks is presented.

  5. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in Frio Fluvial-Deltaic Sandstone Reservoirs of South Texas

    SciTech Connect

    McRae, L.E.; Holtz, M.H.; Knox, P.R.

    1995-07-01

    The Frio Fluvial-Deltaic Sandstone Play of South Texas is one example of a mature play where reservoirs are being abandoned at high rates, potentially leaving behind significant unrecovered resources in untapped and incompletely drained reservoirs. Nearly 1 billion barrels of oil have been produced from Frio reservoirs since the 1940`s, yet more than 1.6 BSTB of unrecovered mobile oil is estimated to remain in the play. Frio reservoirs of the South Texas Gulf Coast are being studied to better characterize interwell stratigraphic heterogeneity in fluvial-deltaic depositional systems and determine controls on locations and volumes of unrecovered oil. Engineering data from fields throughout the play trend were evaluated to characterize variability exhibited by these heterogeneous reservoirs and were used as the basis for resource calculations to demonstrate a large additional oil potential remaining within the play. Study areas within two separate fields have been selected in which to apply advanced reservoir characterization techniques. Stratigraphic log correlations, reservoir mapping, core analyses, and evaluation of production data from each field study area have been used to characterize reservoir variability present within a single field. Differences in sandstone depositional styles and production behavior were assessed to identify zones with significant stratigraphic heterogeneity and a high potential for containing unproduced oil. Detailed studies of selected reservoir zones within these two fields are currently in progress.

  6. Effects of depositional facies and diagenesis on calculating petrophysical properties for wireline logs in Permian carbonate reservoirs of west Texas

    SciTech Connect

    Holtz, M.H.; Major, R.P. )

    1994-03-01

    The complex interplay between depositional facies and diagenesis in carbonate rocks presents numerous problems for calculating petrophysical properties from wireline logs. If carbonate reservoirs are divided into flow units of similar depositional and diagenetic textures, empirical equations that apply specifically to that geologically identified flow unit can be developed to accurately measure porosity and water saturation. In Guadalupian and Leonardian reservoirs, carbonate mudstones deposited in subtidal marine settings are predominantly dolomite, although they contain some shale. The shale in these rocks can be detected with gamma-ray logs and empirical equations for calculation of porosity from log must include a gamma-ray component to compensate for the presence of shale. Because porosity in these rocks is dominantly intercrystalline, capillary pressure characteristics are predictable and saturations can be calculated with the Archie equation. Subtidal carbonate packstones and grainstones are composed of dolomite, anhydrite, and gypsum. The matrix acoustic transit times of these three minerals are similar, and acoustic logs are the best tool for measuring porosity. Neutron logs are the least accurate porosity tools if gypsum is present. Photo-electric density logs can distinguish gypsum from anhydrite. Because porosity in these rocks is dominantly interparticle and/or moldic, dual porosity cementation exponent corrections are needed to calculate saturations with the Archie equation, and capillary pressure saturation relationships are variable. Carbonates deposited in tidal-flat environments are generally composed of dolomite, sulfate minerals, and quartz silt, requiring a full suite of open-hole logs to make reliable porosity measurements. Diagenesis influences reservoir mineralogy and pore types. A common style of burial diagenesis in Guadalupian and Leonardian reservoirs is hydration of anhydrite to gypsum and leaching of sulfate cement and dolomite matrix.

  7. Fluvial depositional systems of Carrizo-Upper Wilcox in south Texas

    SciTech Connect

    Hamlin, H.S.

    1983-09-01

    In the Rio Grande embayment of south Texas, the Carrizo-upper Wilcox interval (Eocene) consists of two sand-rich coastal plain fluvial depositional systems that grade basinward into several deltaic complexes. The bedload channel system is dominated by multi-story, multi-lateral, fluvial, channel-fill sandstones. This system is typically > 90% sandstone. Shales are thin and laterally discontinuous, the remnants of abandoned channel fills. Bedload channel sandstones dominate the major fluvial axes and form the depositional framework of the interval. The mixed alluvial system consists of a more typical suite of coastal plain facies. Mixed-load channel-fill sandstones tend to be isolated and surrounded by overbank shales and thin sandstones. Crevasse splay and lacustrine facies occur in the flood-plain area. Total-interval isopach patterns, sandstone geometries, and depositional systems distributions indicate that fluvial sediment input was converging upon the embayment from the west, northwest, and north. Economically, the Carrizo-upper Wilcox of south Texas has a three-fold significance. The updip Carrizo sandstone is a major source of fresh groundwater, includes several large oil fields, and also contains deposits of uranium minerals. The downdip upper Wilcox trend is an area of active hydrocarbon exploration.

  8. Frio sandstone reservoirs in the deep subsurface along the Texas Gulf Coast: their potential for production of geopressured geothermal energy

    SciTech Connect

    Bebout, D.G.; Loucks, R.G.; Gregory, A.R.

    1983-01-01

    Detailed geological, geophysical, and engineering studies conducted on the Frio Formation have delineated a geothermal test well site in the Austin Bayou Prospect which extends over an area of 60 square miles. A total of 800 to 900 feet of sandstone will occur between the depths of 13,500 and 16,500 feet. At leat 30 percent of the sand will have core permeabilities of 20 to 60 millidarcys. Temperature at the top of the sandstone section will be 300/sup 0/F. Water, produced at a rate of 20,000 to 40,000 barrels per day, will probably have to be disposed of by injection into shallower sandstone reservoirs. More than 10 billion barrels of water are in place in these sandstone reservoirs of the Austin Bayou Prospect; there should be approximately 400 billion cubic feet of methane in solution in this water. Only 10 percent of the water and methane (1 billion barrels of water and 40 billion cubic feet of methane) will be produced without reinjection of the waste water into the producing formation. Reservoir simulation studies indicate that 90 percent of the methane can be produced with reinjection. 106 figures.

  9. Albitization of plagioclase crystals in the Stevens sandstone (Miocene), San Joaquin Basin, California, and the Frio Formation (Oligocene), Gulf Coast, Texas. A TEM/AEM study

    SciTech Connect

    Hirt, W.G. ); Wenk, H.R. ); Boles, J.R. )

    1993-06-01

    Conventional Transmission Electron Microscopy (CTEM) and Analytical Electron Microscopy (AEM) studies of partially albitized plagioclase crystals taken from drill cores from the Stevens sandstone (Miocene), San Joaquin, California, and the Frio Formation (Oligocene), Gulf Coast, Texas, reveal that replacement of Ca-rich plagioclase cores by nearly pure albite (Ab[sub 96]-Ab[sub 100]) occurs along submicroscopic ([minus]15 nm wide) en echelon (001) and (110) cleavages. The cleavages are the result of changes in the localized stress regime created by dissolution of adjacent phases. Photomicrographs show albite-lined brittle cleavage crosscutting albitized semibrittle fractures. Such crosscutting relationships can be explained by a reduction in effective stress associated with the albitization process. On a macroscopic scale, this reduction in effective stress implies that the transition from hydrostatic to lithostatic pressure is discontinuous. 30 refs., 7 figs.

  10. Geologic description of the San Andres reservoir facies in the Mabee field

    SciTech Connect

    Miller, K.D. )

    1992-04-01

    The Mabee field is located in Andrews and Martin counties, Texas, approximately 16 mi northwest of Midland in the Permian basin. Production is from the upper Permian San Andres dolomite at an average depth of 4700 ft. The San Andres/Grayburg formations are the most prolific oil-producing formations in the Permian basin, with total production over 10 billion bbl, and an estimated additional 3.8 billion bbl to be recovered by conventional secondary and tertiary methods. The Mabee field has produced over 90 MMBO by primary and secondary methods since its discovery in 1943. A tertiary CO{sub 2} flood will be implemented in 1992. An essential prerequisite to a successful CO{sub 2} project is a detailed reservoir description and facies analysis. Examination of over 5000 ft of core established six major facies in an overall shallowing-upward sequence. The cap rock consists of dense anhydritic dolomites of the supratidal and oncolite facies. Production primarily is from the underlying dolomitized subtidal and ooid facies. Sandstones interfinger with the ooid facies, but are tightly cemented and act as barriers to fluid migration. The lower-most open-marine facies is below the oil/water contact for the field. Reservoir characterization improves the planning and operation of an enhanced recovery project.

  11. Investigation of the Davis Sandstone (Ft. Worth Basin, Texas) as a suitable formation for the GRI Hydraulic Fracture Test Site. Topical report, March 1992

    SciTech Connect

    Collins, E.; Laubach, S.; Dutton, S.; Kukal, G.; Robinson, B.

    1992-03-01

    The concept of the GRI Hydraulic Fracture Test Site (HFTS) was to provide a field laboratory to (1) validate 3-dimensional hydraulic fracture models in tight gas sandstone and (2) develop technology in fracture diagnostics and stimulation. The Davis sandstone in the Ft. Worth Basin, north-central Texas, was initially selected as a viable candidate formation for HFTS research based on the results of a co-op well program initiated with Dallas Production. To gather comprehensive data on a specific site for HFTS research, the S.A. Holditch and Associates Data Well No. 1 was drilled in June 1991. The results of geological, petrophysical and engineering analyses of the co-ops and data well are the basis of the report. These analyses indicate that in northern Parker and southern Wise Counties, Texas, the Davis sediments range from 250 to 350 ft thick. A broadly-continuous, 100-ft thick interval in the upper part of the gross interval comprises the Davis Reservoir. The average permeability of the Davis Reservoir was found to be 0.08 md with an average closure stress of 0.45 psi/ft. The shale barriers above and below the Davis had average closure stress of 0.63 to 0.73 psi/ft and 0.88 to 0.98 psi/ft, respectively. Hydraulic fracture azimuth was found to range from N10 E to N20 E. Drainage area from production analyses was calculated to be 48.7 acres in northwest Parker County. Natural fractures were encountered in the Davis, causing severe drilling problems in Data Well No. 1. Further work in the Davis was therefore suspended.

  12. Determining between-well reservoir architecture in deltaic sandstones using only well data: Oligocene Frio formation, Tijerina-Canales-Blucher field, South Texas

    SciTech Connect

    Knox, P.R.

    1996-09-01

    Accurate prediction of compartment architecture and intra-compartment heterogeneity is necessary to locate and recover the estimated 15 billion barrels of mobile oil remaining in U.S. fluvial-dominated deltaic reservoirs. Complex architecture and rapid lateral variability in such reservoirs complicate subsurface prediction, particularly in mature fields where well logs are the only available subsurface data. A genetic-stratigraphy-based methodology has been developed that improves between-well prediction of deltaic reservoir architecture and, thus, reduces risks associated with infill-drilling. In the area of Tijerina-Canales-Blucher (T-C-B) field, the productive 3rd-order Lower Frio unit was subdivided into eight 4th-order genetic units. Delta-front positions were identified on the basis of regional and subregional cross sections. The 4th-order units (30 to 80 ft thick) were subdivided into two five 5th-order units (10 to 30 ft thick). Log patterns and n sandstone maps were used to identify facies, which include (1) distributary channels (up to 25 ft thick, <1,000 to >8,000 ft wide, and commonly narrower than 40-acre well spacing), (2) mouth bars (up to 15 ft thick, ranging in size from 40 to 640 acres in area, commonly <320 acres), (3) bayfill splays (up to 10 ft thick, 20 to 700 acres in area, and commonly <160 acres), (4) wave-reworked delta fronts (up to 35 ft thick, and >5,000 ft wide), and (5) washover fans (up to 10 ft thick, and 7,000 ft wide). Many reservoir compartments, including the prolific 21-B interval, contain a significant degree of stratigraphic trapping caused by updip pinchout of delta front or washover sandstones or convex-updip segments of meandering distributary channel sandstones. The methodology and results of this study are directly applicable to other Gulf Coast fluvial-deltaic reservoirs in the Frio Formation and Wilcox Group, as well as to deltaic reservoirs throughout the U.S.

  13. Revitalizing a mature oil play: Strategies for finding and producing oil in Frio Fluvial-Deltaic Sandstone reservoirs of South Texas

    SciTech Connect

    Knox, P.R.; Holtz, M.H.; McRae, L.E.

    1996-09-01

    Domestic fluvial-dominated deltaic (FDD) reservoirs contain more than 30 Billion barrels (Bbbl) of remaining oil, more than any other type of reservoir, approximately one-third of which is in danger of permanent loss through premature field abandonments. The U.S. Department of Energy has placed its highest priority on increasing near-term recovery from FDD reservoirs in order to prevent abandonment of this important strategic resource. To aid in this effort, the Bureau of Economic Geology, The University of Texas at Austin, began a 46-month project in October, 1992, to develop and demonstrate advanced methods of reservoir characterization that would more accurately locate remaining volumes of mobile oil that could then be recovered by recompleting existing wells or drilling geologically targeted infill. wells. Reservoirs in two fields within the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas, a mature play which still contains 1.6 Bbbl of mobile oil after producing 1 Bbbl over four decades, were selected as laboratories for developing and testing reservoir characterization techniques. Advanced methods in geology, geophysics, petrophysics, and engineering were integrated to (1) identify probable reservoir architecture and heterogeneity, (2) determine past fluid-flow history, (3) integrate fluid-flow history with reservoir architecture to identify untapped, incompletely drained, and new pool compartments, and (4) identify specific opportunities for near-term reserve growth. To facilitate the success of operators in applying these methods in the Frio play, geologic and reservoir engineering characteristics of all major reservoirs in the play were documented and statistically analyzed. A quantitative quick-look methodology was developed to prioritize reservoirs in terms of reserve-growth potential.

  14. Variations in cementation exponent (m) and fracture porosity, Permian Delaware Mountain Group sandstones, Reeves and Culberson counties, Texas

    SciTech Connect

    Thomerson, M.D.; Arnold, M.D.; Asquith, G.B. )

    1994-03-01

    To calculate accurate volumetric oil reserves in the Permian Delaware Mountain Group, reliable values for cementation exponent (m) are required in addition to the other reservoir parameters. The porosity in these siltstone and very fine-grain sandstone reservoirs is intergranular and therefore the cementation exponent should be approximately 2.0. However, crossplots of core derived porosity vs. the formation resistivity factor (Fr) indicate an average cementation exponent (m) of 1.80. the lower cementation exponent is a result of minor amounts of fracture porosity. Comparison of the Delaware Mountain Group porosity vs. the Fr crossplot with the laboratory data of Rasmus (1987), reveals a similar decrease in Fr with a decrease in porosity due to the presence of a 1% fracture porosity. The lower cementation exponent (1.80) results in the calculation of substantially lower water saturations, which increases the amount of volumetric oil reserves. Analysis of three zones in the Bell Canyon and Cherry Canyon formations of the Delaware Mountain Group using standard methods of calculating water saturation resulted in volumetric oil reserves (based on 40 ac drainage) of 1.37 to 1.42 million bbl. However, using a cementation exponent of 1.80 resulted in volumetric oil reserves of 1.55 million bbl. The 9% to 13% increase in volumetric oil reserves from only three zones in the Bell Canyon and Cherry Canyon formations illustrates the critical importance of combining core analysis with log analysis when doing volumetric reserve calculations.

  15. National Uranium Resource Evaluation: Lawton Quadrangle, Oklahoma and Texas

    SciTech Connect

    Al-Shaieb, Z.; Thomas, R.G.; Stewart, G.F.

    1982-04-01

    Uranium resources of the Lawton Quadrangle, Oklahoma and Texas, were evaluated to a depth of 1500 m using National Uranium Resource Evaluation criteria. Five areas of uranium favorability were delineated. Diagenetically altered, quartzose and sublithic, eolian and marginal-marine sandstones of the Permian Rush Springs Formation overlying the Cement Anticline are favorable for joint-controlled deposits in sandstone, non-channel-controlled peneconcordant deposits, and Texas roll-front deposits. Three areas contain lithologies favorable for channel-controlled peneconcordant deposits: arkosic sandstones and granule conglomerates of the Permian Post Oak Conglomerate south of the Wichita Mountains; subarkosic and sublithic Lower Permian fluvio-deltaic and coastal-plain sandstones of the eastern Red River Valley; and subsurface arkosic, subarkosic, and sublithic alluvial-fan and fan-delta sandstones of the Upper Pennsylvanian-Lower Permian sequence in the eastern Hollis Basin. The coarse-grained facies of the Cambrian Quanah Granite and genetically related aplite and pegmatite dikes in the Wichita Mountains are favorable for orthomagmatic and autometasomatic deposits, respectively.

  16. Diagenetic resetting of Sm-Nd isotope systematics in Wilcox Group sandstones and shales, San Marcos Arch, south-central Texas

    SciTech Connect

    Awwiller, D.N.; Mack, L.E. )

    1989-09-01

    Preliminary Sm-Nd analyses of sandstones and shales from the Wilcox Group (upper Paleocene-lower Eocene) suggest that the whole-rock Sm-Nd signature is changed by diagenesis. Samples are obtained from the San Marcos arch, south-central Texas, at depths ranging from outcrop to 15,000 ft. Samples from above the depth of intense illitization and feldspar reactions (about 10,000 ft) have whole-rock Nd model ages of about 1,500-1,400 Ma, whereas samples buried deeper than 13,000 ft have Nd model ages of about 1,700-1,500 Ma. The similar depositional age of all samples makes change in provenance an unlikely cause of the variation. Diagenetic modification is the only reasonable explanation for the observed differences. Sm and Nd reservoirs within the shale change considerably with progressive diagenesis. Outcrop samples contain subequal concentrations of Sm and Nd in the acid-soluble and silicate fractions. The acid-soluble reservoir in deeper samples contains progressively less Sm and Nd and higher Sm/Nd ratios. In all samples, the acid-soluble Nd is more radiogenic than the Nd in the corresponding silicate fraction; the difference between the two reservoirs increases with depth. Preferential loss of Nd relative to Sm in the silicate reservoir during diagenetic crystallization of illite and albite is the most likely explanation for the observed trend in Nd model age. These data imply that the earlier assumption that no fractionation takes place in the Sm-Nd system during diagenesis is incorrect.

  17. Depositional and diagenetic controls on porosity permeability and oil production in McFarland/Magutex (Queen) reservoirs, Andrews County, west Texas

    SciTech Connect

    Holtz, M.H. )

    1991-03-01

    The McFarland/Magutex Queen reservoir complex lies along the northeastern edge of the Central basin platform in the west Texas Permian basin and produces oil from the Permian Queen Formation. Current production from this complex totals 42 million stock-tank barrels (MMSTB) of an estimated 219 MMSTB of original oil in place, with an estimated 90 MMSTB of remaining mobile oil (RMO). The gross pay interval contains two parasequences consisting of progradational, 30-ft-thick, upward-shoaling facies packages. Facies include shoreface, mixed tidal channel and intertidal flat, and supratidal. Elongate shoreface facies are characterized by poorly consolidated, massive to thinly laminated sandstones. The supratidal facies, which act as permeability barriers, are characterized by algal-laminated dolostone and nodular, laminated, and massive anhydrite containing halite and gypsum pseudomorphs. Highest production and the largest amount of the 90 MMSTB of RMO is associated with the shoreface and tidal-channel facies. Bulk pore volume storage capacity and permeability are also highest within these two facies. Sandstones are arkosic, containing anhydrite and dolomite cements. Accessory minerals are clays, authigenic feldspar, and dolomite. Three main pore types are recognized: interparticle, moldic and intraconstituent, and micropores. Moldic and intraconstituent porosity is associated with leached feldspars and anhydrite cement dissolution. Microporosity is associated with syndepositional, grain-coating corrensite, dissolution-enhanced feldspar cleavage planes, and authigenic multifaceted dolomite. Microporosity derived from clays and dolomite is formed preferentially in tidal-channel and intertidal flat facies.

  18. Evolution of salt structures, East Texas Diapir Province, Part 1: Sedimentary record of Halokinesis

    SciTech Connect

    Seni, S.J.; Jackson, M.P.A.

    1983-08-01

    Post-Aptian (post-112Ma) strata in the East Texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures. Domeinduced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas basin exhibit three stages of growth: pillow, diapir, and post-diapir, each of which affected surrounding strata differently. Pillow growth caused broad uplift of strata over the crest of the pillows; the resulting topographic swell influenced depositional trends and was susceptible to erosion. Fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway field. Post-diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages. Documented facies variations over and around domes at different stages of growth enable prediction of subtle facies-controlled hydrocarbon traps. Facies-controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the East Texas basin.

  19. Evolution of salt structures, East Texas diapir province, part 1: sedimentary record of halokinesis

    SciTech Connect

    Seni, S.J.; Jackson M.P.A.

    1983-08-01

    Post-Aptian (post-112 Ma) strata in the East Texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures. Dome-induced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas basin exhibit three stages of growth: pillow, diapir, and post-diapir, each of which affected surrounding strata differently. Pillow growth caused broad uplift of strata over the crest of the pillows; the resulting topographic swell influenced depositional trends and was susceptible to erosion. Fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway field. Post-diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages. Documented facies variations over and around domes at different stages of growth enable prediction of subtle facies-controlled hydrocarbon traps. Facies-controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the East Texas basin.

  20. Study effects of geopressured-geothermal subsurface environment on elastic properties of Texas Gulf Coast sandstones and shales using well logs, core data, and velocity surveys. Final report

    SciTech Connect

    Gregory, A.R.

    1980-05-01

    Relations between porosity and permeability for the Pleasant Bayou wells were determined from conventional core data. Porosities from the time average equations required compaction correction factors of 1.9 in hydropressured sandstones and 1.0 in geopressured sandstones. Best average prmeabilities in the geopressured zone were found in the primary production interval 14,687 to 14,716 ft (4477 to 4485 m). Average density gradients were 2.106 x 10/sup -3/ and 2.688 x 10/sup -3/ (gm/cm/sup 3/)/100 ft in sandstones and shales respectively. Compressional (P-wave) and shear (S-wave) velocities from the long-spaced sonic log and bulk densities from the formation density log were used to compute in-situ elastic moduli, Poisson's ratio, V/sub p//V/sub s/, and bulk compressibility in two intervals of deep geopressured sandstone and shale in No. 2 Pleasant Bayou. Most computed values of these parameters seem reasonable. Improved accuracy of travel times from the long-spaced sonic log should permit more accurate depth-to-time correlation with seismic data.

  1. Turbidite facies in an ancient subduction complex: Torlesse terrane, New Zealand

    USGS Publications Warehouse

    MacKinnon, T.C.; Howell, D.G.

    1984-01-01

    The Torlesse terrane of New Zealand is an ancient subduction complex consisting of deformed turbidite-facies rocks. These are mainly thick-bedded sandstone (facies B and C) with subordinate mudstone (facies D and E), comparable to inner- and middle-fan deposits of a submarine fan. Strata were deposited in trench-floor and trench-slope settings that received sandy sediment from slope-cutting submarine canyons. The dominance of sandstone suggests that some mudstone may have been selectively subducted. Construction of a detailed sediment dispersal model is not possible because tectonic deformation has largely destroyed original facies relationships and paleocurrent patterns. ?? 1984 Springer-Verlag New York Inc.

  2. Sedimentary Facies of the West Crocker Formation North Kota Kinabalu-Tuaran Area, Sabah, Malaysia

    NASA Astrophysics Data System (ADS)

    Mohamed, Azfar; Hadi Abd Rahman, Abdul; Suhaili Ismail, Mohd

    2016-02-01

    Newly outcrops exposed in the West Crocker Formation have led to the detail sedimentolgical analysis of the formation. Eight sedimentary facies have been recognised in which it was divided into three main groups: (1) sand-dominated facies (F1-F2), (2) poorly- sorted unit mixed sand and mud-dominated facies (F3), and (3) mud-dominated facies (F4-F5). These are: F1- graded sandstone (massive to planar laminated), F2-ripple-cross laminated, wavy and convolute lamination sandstone, F3-chaotic beds of mixed sandstone and mudstone blocks and clasts, F4-lenticular bedded of sandstone, and F5-shale. The studies of the formation has come out that it was deposited in a sand-rich submarine fan with specific location located at (1) inner fan channel-levee complex; (2) mid-fan channelised lobes, and (3) outer fan.

  3. Geoscience/engineering characterization of the interwell environment in carbonate reservoirs based on outcrop analogs, Permian Basin, West Texas and New Mexico-stratigraphic hierarchy and cycle stacking facies distribution, and interwell-scale heterogeneity: Grayburg Formation, New Mexico. Final report

    SciTech Connect

    Barnaby, R.J.; Ward, W.B.; Jennings, J.W. Jr.

    1997-06-01

    The Grayburg Formation (middle Guadalupian) is a major producing interval in the Permian Basin and has yielded more than 2.5 billion barrels of oil in West Texas. Grayburg reservoirs have produced, on average, less than 30 percent of their original oil in place and are undergoing secondary and tertiary recovery. Efficient design of such enhanced recovery programs dictates improved geological models to better understand and predict reservoir heterogeneity imposed by depositional and diagenetic controls. The Grayburg records mixed carbonate-siliciclastic sedimentation on shallow-water platforms that rimmed the Delaware and Midland Basins. Grayburg outcrops in the Guadalupe and Brokeoff Mountains region on the northwest margin of the Delaware Basin present an opportunity to construct a detailed, three-dimensional image of the stratigraphic and facies architecture. This model can be applied towards improved description and characterization of heterogeneity in analogous Grayburg reservoirs. Four orders of stratigraphic hierarchy are recognized in the Grayburg Formation. The Grayburg represents a long-term composite sequence composed of four high-frequency sequences (HFS 1-4). Each HFS contains several composite cycles comprising two or more cycles that define intermediate-scale transgressive-regressive successions. Cycles are the smallest scale upward-shoaling vertical facies successions that can be recognized and correlated across various facies tracts. Cycles thus form the basis for establishing the detailed chronostratigraphic correlations needed to delineate facies heterogeneity.

  4. Application of Advanced Reservoir Characterization, Simulation, and Production Optimization Strategies to Maximize Recovery in Slope and Basin Clastic Reservoirs, West Texas (Delaware Basin)

    SciTech Connect

    Andrew G. Cole; George B. Asquith; Jose I. Guzman; Mark D. Barton; Mohammad A. Malik; Shirley P. Dutton; Sigrid J. Clift

    1998-04-01

    The objective of this Class III project is to demonstrate that detailed reservoir characterization of clastic reservoirs in basinal sandstones of the Delaware Mountain Group in the Delaware Basin of West Texas and New Mexico is a cost-effective way to recover more of the original oil in place by strategic infill-well placement and geologically based enhanced oil recovery. The study focused on the Ford Geraldine unit, which produces from the upper Bell Canyon Formation (Ramsey sandstone). Reservoirs in this and other Delaware Mountain Group fields have low producibility (average recovery <14 percent of the original oil in place) because of a high degree of vertical and lateral heterogeneity caused by depositional processes and post-depositional diagenetic modification. Outcrop analogs were studied to better interpret the depositional processes that formed the reservoirs at the Ford Geraldine unit and to determine the dimensions of reservoir sandstone bodies. Facies relationships and bedding architecture within a single genetic unit exposed in outcrop in Culberson County, Texas, suggest that the sandstones were deposited in a system of channels and levees with attached lobes that initially prograded basinward, aggraded, and then turned around and stepped back toward the shelf. Channel sandstones are 10 to 60 ft thick and 300 to 3,000 ft wide. The flanking levees have a wedge-shaped geometry and are composed of interbedded sandstone and siltstone; thickness varies from 3 to 20 ft and length from several hundred to several thousands of feet. The lobe sandstones are broad lens-shaped bodies; thicknesses range up to 30 ft with aspect ratios (width/thickness) of 100 to 10,000. Lobe sandstones may be interstratified with laminated siltstones.

  5. Facies control on reservoir properties within a barrier island complex, Sparta Formation, Pointe Coupee Parish, Louisiana

    SciTech Connect

    Lemoine, R.C.; Moslow, T.F.; Ferrell, R.E.

    1988-02-01

    Analysis of conventional core, well logs, and petrophysical data has yielded an interpretation of the Sparta B sandstone in south-central Louisiana as a prograding barrier island complex. Four sedimentary facies possess reservoir potential: lower shoreface, upper shoreface, storm washover, and tidal-inlet channel sandstone facies. Distinct porosity and permeability values are associated with each reservoir facies. Predictable porosity and permeability trends associated with the Sparta B sandstone barrier island complex allows for identification of distinct fluid flow units within the sequence. In addition, individual sedimentary facies possess characteristic well log signatures; therefore, the geometry, thickness variability, and lateral continuity of each fluid flow unit can be determined and heterogeneities within the reservoir interval can be resolved.

  6. Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

    USGS Publications Warehouse

    Anderson, P.B.; Chidsey, T.C., Jr.; Ryer, T.A.

    1997-01-01

    East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

  7. Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Sumner, Dawn Y.; Williams, Rebecca M. E.; Schieber, Juergen; Palucis, Marisa C.; Oehler, Dorothy Z.; Mangold, Nicolas; Kah, Linda C.; Gupta, Sanjeev; Grotzinger, John P.; Grant, John A., III; Edgar, Lauren A.; Dietrich, William E.

    2015-01-01

    NASA's Curiosity rover has documented predominantly fluvial sedimentary rocks along its path from the landing site to the toe of the Peace Vallis alluvial fan (0.5 km to the east) and then along its 8 km traverse across Aeolis Palus to the base of Aeolis Mons (Mount Sharp). Lacustrine facies have been identified at the toe of the Peace Vallis fan and in the lowermost geological unit exposed on Aeolis Mons. These two depositional systems provide end members for martian fluvial/alluvial-lacustrine facies models. The Peace Vallis system consisted of an 80 square kilometers alluvial fan with decimeter-thick, laterally continuous fluvial sandstones with few sedimentary structures. The thin lacustrine unit associated with the fan is interpreted as deposited in a small lake associated with fan runoff. In contrast, fluvial facies exposed over most of Curiosity's traverse to Aeolis Mons consist of sandstones with common dune-scale cross stratification (including trough cross stratification), interbedded conglomerates, and rare paleochannels. Along the southwest portion of the traverse, sandstone facies include south-dipping meter-scale clinoforms that are interbedded with finer-grained mudstone facies, interpreted as lacustrine. Sedimentary structures in these deposits are consistent with deltaic deposits. Deltaic deposition is also suggested by the scale of fluvial to lacustrine facies transitions, which occur over greater than 100 m laterally and greater than 10 m vertically. The large scale of the transitions and the predicted thickness of lacustrine deposits based on orbital mapping require deposition in a substantial river-lake system over an extended interval of time. Thus, the lowermost, and oldest, sedimentary rocks in Gale Crater suggest the presence of substantial fluvial flow into a long-lived lake. In contrast, the Peace Vallis alluvial fan onlaps these older deposits and overlies a major unconformity. It is one of the youngest deposits in the crater, and

  8. Geothermal and heavy-oil resources in Texas

    SciTech Connect

    Seni, S.J.; Walter, T.G.

    1994-01-01

    In a five-county area of South Texas, geopressured-geothermal reservoirs in the Paleocene-Eocene Wilcox Group lie below medium- to heavy-oil reservoirs in the Eocene Jackson Group. This fortuitous association suggests the use of geothermal fluids for thermally enhanced oil recovery (TEOR). Geothermal fairways are formed where thick deltaic sandstones are compartmentalized by growth faults. Wilcox geothermal reservoirs in South Texas are present at depths of 11,000 to 15,000 ft (3,350 to 4,570 m) in laterally continuous sandstones 100 to 200 ft (30 to 60 m) thick. Permeability is generally low (typically 1 md), porosity ranges from 12 to 24 percent, and temperature exceeds 250{degrees}F (121{degrees}C). Reservoirs containing medium (20{degrees} to 25{degrees} API gravity) to heavy (10{degrees} to 20{degrees} API gravity) oil are concentrated along the Texas Coastal Plain in the Jackson-Yegua Barrier/Strandplain (Mirando Trend), Cap Rock, and Piercement Salt Dome plays and in the East Texas Basin in Woodbine Fluvial/Deltaic Strandplain and Paluxy Fault Line plays. Injection of hot, moderately fresh to saline brines will improve oil recovery by lowering viscosity and decreasing residual oil saturation. Smectite clay matrix could swell and clog pore throats if injected waters have low salinity. The high temperature of injected fluids will collapse some of the interlayer clays, thus increasing porosity and permeability. Reservoir heterogeneity resulting from facies variation and diagenesis must be considered when siting production and injection wells within the heavy-oil reservoir. The ability of abandoned gas wells to produce sufficient volumes of hot water over the long term will also affect the economics of TEOR.

  9. Process regime variability across growth faults in the Paleogene Lower Wilcox Guadalupe Delta, South Texas Gulf Coast

    NASA Astrophysics Data System (ADS)

    Olariu, Mariana I.; Ambrose, William A.

    2016-07-01

    The Wilcox Group in Texas is a 3000 m thick unit of clastic sediments deposited along the Gulf of Mexico coast during early Paleogene. This study integrates core facies analysis with subsurface well-log correlation to document the sedimentology and stratigraphy of the Lower Wilcox Guadalupe Delta. Core descriptions indicate a transition from wave- and tidally-influenced to wave-dominated deposition. Upward-coarsening facies successions contain current ripples, organic matter, low trace fossil abundance and low diversity, which suggest deposition in a fluvial prodelta to delta front environment. Heterolithic stratification with lenticular, wavy and flaser bedding indicate tidal influence. Pervasively bioturbated sandy mudstones and muddy sandstones with Cruziana ichnofacies and structureless sandstones with Ophiomorpha record deposition in wave-influenced deltas. Tidal channels truncate delta front deposits and display gradational upward-fining facies successions with basal lags and sandy tabular cross-beds passing into heterolithic tidal flats and biologically homogenized mudstones. Growth faults within the lower Wilcox control expanded thickness of sedimentary units (up to 4 times) on the downdip sides of faults. Increased local accommodation due to fault subsidence favors a stronger wave regime on the outer shelf due to unrestricted fetch and water depth. As the shoreline advances during deltaic progradation, successively more sediment is deposited in the downthrown depocenters and reworked along shore by wave processes, resulting in a thick sedimentary unit characterized by repeated stacking of shoreface sequences. Thick and laterally continuous clean sandstone successions in the downthrown compartments represent attractive hydrocarbon reservoirs. As a consequence of the wave dominance and increased accommodation, thick (tens of meters) sandstone-bodies with increased homogeneity and vertical permeability within the stacked shoreface successions are created.

  10. Quantitative analysis of sandstone porosity

    SciTech Connect

    Ferrell, R.E. Jr.; Carpenter, P.K.

    1988-01-01

    A quantitative analysis of changes in porosity associated with sandstone diagenesis was accomplished with digital back-scattered electron image analysis techniques. The volume percent (vol. %) of macroporosity, quartz, clay minerals, feldspar, and other constituents combined with stereological parameters, such as the size and shape of the analyzed features, permitted the determination of cement volumes, the ratio of primary to secondary porosity, and the relative abundance of detrital and authigenic clay minerals. The analyses were produced with a JEOL 733 Superprobe and a TRACOR/NORTHERN 5700 Image Analyzer System. The results provided a numerical evaluation of sedimentological facies controls and diagenetic effects on the permeabilities of potential reservoirs. In a typical application, subtle differences in the diagnetic development of porosity were detected in Wilcox sandstones from central Louisiana. Mechanical compaction of these shoreface sandstones has reduced the porosity to approximately 20%. In most samples with permeabilities greater than 10 md, the measured ratio of macroporosity to microporosity associated with pore-filling kaolinite was 3:1. In other sandstones with lower permeabilities, the measured ratio was higher, but the volume of pore-filling clay was essentially the same. An analysis of the frequency distribution of pore diameters and shapes revealed that the latter samples contained 2-3 vol% of grain-dissolution or moldic porosity. Fluid entry to these large pores was restricted and the clays produced from the grain dissolution products reduced the observed permeability. The image analysis technique provided valuable data for the distinction of productive and nonproductive intervals in this reservoir.

  11. Sequence Stratigraphic Analysis and Facies Architecture of the Cretaceous Mancos Shale on and Near the Jicarilla Apache Indian Reservation, New Mexico-their relation to Sites of Oil Accumulation

    SciTech Connect

    Ridgley, Jennie

    2001-08-21

    The purpose of phase 1 and phase 2 of the Department of Energy funded project Analysis of oil- bearing Cretaceous Sandstone Hydrocarbon Reservoirs, exclusive of the Dakota Sandstone, on the Jicarilla Apache Indian Reservation, New Mexico was to define the facies of the oil producing units within the Mancos Shale and interpret the depositional environments of these facies within a sequence stratigraphic context. The focus of this report will center on (1) redefinition of the area and vertical extent of the ''Gallup sandstone'' or El Vado Sandstone Member of the Mancos Shale, (2) determination of the facies distribution within the ''Gallup sandstone'' and other oil-producing sandstones within the lower Mancos, placing these facies within the overall depositional history of the San Juan Basin, (3) application of the principals of sequence stratigraphy to the depositional units that comprise the Mancos Shale, and (4) evaluation of the structural features on the Reservation as they may control sites of oil accumulation.

  12. Porosity prediction in sandstones using erosional unconformities

    SciTech Connect

    Shanmugam, G.

    1989-03-01

    Erosional unconformities of subaerial origin are created by tectonic uplifts and eustatic sea level fall. Most erosional unconformities developed on sandstones are planes of increased porosity because uplifted sandstones are exposed to undersaturated CO/sub 2/-charged meteoric waters that result in dissolution of unstable framework grains and cements. The chemical weathering of sandstones is intensified in humid regions by the heavy rainfall, soil zones, lush vegetation, and accompanying voluminous production of organic and inorganic acids. Erosional unconformities are considered hydrologically open systems because of abundant supply of fresh meteoric water and relatively unrestricted transport of dissolved constituents away from the site of dissolution, causing a net gain in porosity near unconformities. Thus, porosity in sandstones tends to increase toward overlying unconformities. Such porosity trends have been observed in hydrocarbon-bearing sandstone reservoirs in Alaska, Algeria, Australia, China, Libya, Netherlands, Norwegian North Sea, Norwegian Sea, and Texas. A common attribute of these reservoirs is that they were all subaerially exposed under heavy rainfall conditions. An empirical model has been developed for the Triassic and Jurassic sandstone reservoirs in the Norwegian North Sea on the basis of the observed relationship that shows an increase in porosity in these reservoirs with increasing proximity to the overlying base of Cretaceous unconformity. An important practical attribute of this model is that it allows for the prediction of porosity in the neighboring undrilled areas by recognizing the base of Cretaceous unconformity in seismic reflection profiles and by constructing subcrop maps.

  13. Provenance of Norphlet sandstone, northern Gulf Coast

    SciTech Connect

    Ryan, W.P.; Ward, W.C.; Kuglar, R.L.

    1987-09-01

    The Upper Jurassic Norphlet sandstone of the northern Gulf Coast is predominantly subarkose, with some arkose in the eastern area and sublitharenite and quartzarenite in the western area. Despite great depths of burial and despite feldspar and rock-fragment constituents, diagenesis has not appreciably altered the composition of Norphlet sandstone. Therefore, reconstruction of original composition of Norphlet sandstone presented little difficulty. Variation in detrital modes of the Norphlet suggests compositionally distinct source terranes. Samples from Florida, Alabama, and Mississippi reflect the influence of metamorphic and plutonic rocks of the Appalachian Piedmont Province and of Triassic-Jurassic volcanic rocks. Sandstones in east Texas, northern Louisiana, and southern Arkansas were derived from sedimentary and metasedimentary rocks of the Ouachita system. The Arbuckle Mountains and Llano uplift may have supplied trace amounts of quartzo-feldspathic and volcanic-rock fragments to the extreme western part of the study area. Norphlet sandstones represent a mixture of collision-orogen-derived sediment from the Appalachian and/or Ouachita system and continental-block-derived sediment from paleohighs and uplifts within the Gulf basin. However, Norphlet sandstones plot in the craton-interior and transitional-continental fields on Q-F-L and QM-F-Lt tectonic-provenance diagrams, because of mineralogically mature source rocks, elimination of unstable grains by abrasion and sorting during deposition, and/or sediment mixing from different source terranes.

  14. Sedimentology and genetic stratigraphy of Dean and Spraberry Formations (Permian), Midland basin, Texas

    SciTech Connect

    Handford, C.R.

    1981-09-01

    The Spraberry trend of west Texas, once known as the world's largest uneconomic oil field, will undoubtedly become an increasingly important objective for the development of enhanced oil recovery techniques in fine-grained, low-permeability, low-pressure reservoirs. As the trend expands, facies and stratigraphic data should be integrated into exploration strategies. The Spraberry and Dean Formations may be divided into three genetic sequences, each consisting of several hundred feet of interbedded shale and carbonate overlain by a roughly equal amount of sandstone and siltstone. These sequences record episodes of shelf-margin progradation, deep-water resedimentation of shelf-derived carbonate debris, followed by influxes of terrigenous clastics into the basin by way of feeder channels or submarine canyons, and suspension settling of fine-grained sediment from the water column. Four lithofacies comprise the terrigenous clastics of the Spraberry and Dean Fomations: (1) cross-laminated, massive, and parallel-laminated sandstone, (2) laminated siltstone, (3) bioturbated siltstone, and (4) black, organic-rich shale. Carbonate lithofacies occur mostly in the form of thin-bedded turbidites, slump, and debris-flow deposits. Terrigenous clastic rocks display facies sequences, isopach patterns, and sedimentary structures suggestive of deposition from turbidity currents, and long-lived saline density underflow and interflow currents. Clastic isopach patterns reflect an overall southward thinning of clastics in the Midland basin. Channelized flow and suspension settling were responsible for the formation of elongate fan-shaped accumulations of clastic sediments.

  15. Deep-marine facies models: Implications for hydrocarbon exploration and production

    SciTech Connect

    Shanmugam, G. )

    1991-03-01

    Facies models serve as a generalized conceptual framework for classifying and understanding sedimentary environments. Deep-marine facies models range in scale from a single facies of a turbidite bed (first-order models) to an association of different facies representing an entire submarine fan or a basin-fill complex (third-order models). At present, numerous facies models exist for modern and ancient deep-marine systems with distinct depositional components. These models are based on (1) types of channel (e.g., convergent and divergent channel systems, low-sinuosity and high-sinuosity channel patterns), (2) types of lobes (e.g., suprafan lobes, depositional lobes, fanlobes, ponded lobes), (3) tectonic settings (e.g., active-margin and mature passive-margin fans), (4) eustatic sea-level changes (e.g., lowstand submarine fans and highstand nonfan turbidites), (5) sediment sources (e.g., canyon-fed submarine fan and delta-fed submarine ramp), and (6) bottom-current reworking. It is also clear that not all submarine fans are composed of identical distribution of depositional facies in time and space. Therefore, no single facies model can adequately explain all submarine fans. Submarine fans can and do vary in their size, shape, lithofacies distribution, sand-body geometry, and reservoir quality. Because facies models differ significantly from each other in terms of reservoir properties, caution must be exercised in selecting a particular facies model for a sandstone reservoir.

  16. Sedimentary Petrography and Facies Analysis at the Shaler Outcrop, Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Edgar, L. A.; Gupta, S.; Rubin, D. M.; Lewis, K. W.; Kocurek, G.; Anderson, R. B.; Bell, J. F.; Dromart, G.; Edgett, K. S.; Grotzinger, J. P.; Hardgrove, C. J.; Kah, L. C.; Leveille, R. J.; Malin, M.; Mangold, N.; Milliken, R.; Minitti, M. E.; Rice, M. S.; Rowland, S. K.; Schieber, J.; Stack, K.; Sumner, D. Y.; Team, M.

    2013-12-01

    The Mars Science Laboratory Curiosity rover has recently completed an investigation of a large fluvial deposit known informally as the Shaler outcrop (~1 m thick). Curiosity acquired data at the Shaler outcrop during sols 120-121 and 309-324. The Shaler outcrop is comprised of cross-bedded coarse-grained sandstones and recessive finer-grained intervals. Shaler is distinguished from the surrounding units by the presence of resistant beds exhibiting decimeter scale trough cross-bedding. Observations using the Mast Cameras, Mars Hand Lens Imager (MAHLI) and ChemCam Remote Micro Imager (RMI) enable the recognition of several distinct facies. MAHLI images were acquired on five distinct rock targets, and RMI images were acquired at 33 different locations. On the basis of grain size, erosional resistance, color, and sedimentary structures, we identify four facies: 1) resistant cross-stratified facies, 2) smooth, fine-grained cross-stratified facies, 3) dark gray, pitted facies, and 4) recessive, vertically fractured facies. Panoramic Mastcam observations reveal facies distributions and associations, and show cross-bedded facies that are similar to those observed at the Rocknest and Bathurst_Inlet locations. MAHLI and RMI images are used to determine the grain size, sorting, rounding and sedimentary fabric of the different facies. High-resolution images also reveal small-scale diagenetic features and sedimentary structures that are used to reconstruct the depositional and diagenetic history.

  17. Sedimentology and reservoir characteristics of tight gas sandstones, Frontier formation, southwestern Wyoming

    SciTech Connect

    Moslow, T.F.; Tillman, R.W.

    1984-04-01

    The lower Frontier Formation, Moxa arch area, southwestern Wyoming, is one of the most prolific gas-producing formations in the Rocky Mountain region. Lower Frontier sediments were deposited as strandplains and coalescing wave-dominated deltas that prograding into the western margin of the Cretaceous interior seaway during the Cenomanian. In this study, sedimentologic, petrologic, and stratigraphic analyses were conducted on cores and logs of Frontier wells from the Whiskey Buttes and Moxa fields. Twelve sedimentary facies have been identified. The most common sequence consists of burrowed to cross-bedded near shore marine (delta-front and inner-shelf) sandstones disconformably overlain by cross-bedded (active) to deformed (abandoned) distributary-channel sandstones and conglomerates. The sequence is capped by delta-plain mudstones and silty sandstones. Tight-gas sandstone reservoir facies are non-homogenous and include crevasse splay, abandoned and active distributary channel, shoreface, foreshore, and inner shelf sandstones. Distributary-channel facies represent 80% of perforated intervals in wells in the southern part of the Moxa area, but only 50% to the north. Channel sandstone bodies are occasionally stacked, occur on the same stratigraphic horizon, and are laterally discontinuous with numerous permeability barriers. Percentage of perforated intervals in upper shoreface and foreshore facies increases from 20% in the south to 50% in the north.

  18. Sedimentology and reservoir characteristics of tight gas sandstones, Frontier formation, southwestern Wyoming

    SciTech Connect

    Moslow, T.F.; Tillman, R.W.

    1984-04-01

    The lower Frontier Formation, Moxa arch area, southwestern Wyoming, is one of the most prolific gas-producing formations in the Rocky Mountain region. Lowr Frontier sediments were deposited as strandplains and coalescing wave-dominated deltas that prograding into the western margin of the Cretaceous interior seaway during the Cenomanian. In this study, sedimentologic, petrologic, and stratigraphic analyses were conducted on cores and logs of Frontier wells from the Whiskey Buttes and Moxa fields. Twelve sedimentary facies have been identified. The most common sequence consists of burrowed to cross-bedded near shore marine (delta-front and inner-shelf) sandstones disconformably overlain by crossbedded (active) to deformed (abandoned) distributary-channel sandstones and conglomerates. The sequence is capped by delta-plain mudstones and silty sandstones. Tight-gas sandstone reservoir facies are nonhomogenous and include crevasse splay, abandoned and active distributary channel, shoreface, foreshore, and inner shelf sandstones. Distributary-channel facies represent 80% of perforated intervals in wells in the southern part of the Moxa area, but only 50% to the north. Channel sandstone bodies are occasionally stacked, occur on the same stratigraphic horizon, and are laterally discontinuous with numerous permeability barriers. Percentage of perforated intervals in upper shoreface and foreshore facies increases from 20% in the south to 50% in the north.

  19. Sedimentation of shelf sandstones in Queen Formation, McFarland and Means fields, central basin platform of Permian basin

    SciTech Connect

    Malicse, A.; Mazzullo, J.; Holley, C.; Mazzullo, S.J.

    1988-01-01

    The Queen Formation is a sequence of carbonates, evaporites, and sandstones of Permian (Guadalupian) age that is found across the subsurface of the Central Basin platform of the Permian basin. The formation is a major hydrocarbon reservoir in this region, and its primary reservoir facies are porous shelf sandstones and dolomites. Cores and well logs from McFarland and Means fields (on the northwest margin of the Central Basin platform) were examined to determine the sedimentary history of the shelf sandstones.

  20. Abandoned oil fields of Texas Gulf Coast

    SciTech Connect

    Dutton, S.P.

    1984-04-01

    One nonconventional oil target in Texas is the oil that remains in abandoned fields, defined as those fields that had no oil or gas production in 1977 and 1982. This target includes oil that has not been tapped by conventional field development because of reservoir heterogeneity and oil in reservoirs that have not been subjected to any secondary or tertiary recovery efforts. A total of 138 abandoned oil fields having individual cumulative production greater than 500,000 bbl are located in the Texas Gulf Coast (railroad Commission of Texas Districts 2, 3, and 4). These 138 onshore fields produced 276 million barrels of oil before being abandoned. Nongiant fields in the Texas Gulf Coast average about 40% ultimate recovery, so these fields probably originally contained about 700 million bbl of oil in place. Therefore, about 424 million bbl of oil remain unrecovered. Reservoirs in these abandoned fields are Tertiary sandstones. The 44 abandoned fields in the upper Texas Gulf Coast (District 3) produced from a wide range of plays; those plays with the largest number of abandoned fields are Yegua and Frio deep-seated domes, Eocene deltaic sandstone, and Frio barrier/strand-plain sandstone. The 19 abandoned fields in the middle Texas Gulf Coast (District 2) produced mainly from Wilcox and Frio fluvial/deltaic sandstones and from Frio and Jackson-Yegua barrier/strand-plain sandstones. The lower Texas Gulf Coast (District 4) contains 75 abandoned fields that produced from Frio fluvial/deltaic and barrier/strand-plain sandstones and from Jackson-Yegua barrier/strand-plain sandstones.

  1. Reservoir characterization and preliminary modeling of deltaic facies, lower Wilcox, Concordia Parish, Louisiana

    SciTech Connect

    Schenewerk, P.; Goddard, D.; Echols, J.

    1994-12-31

    The decline in production in several fields in Concordia Parish, Louisiana, has created interest in the economic feasibility of producing the remaining bypassed oil in the lower Wilcox Group. One of these fields, Bee Brake, has been one of the more prolific oil-producing fields in east-central Louisiana. The producing interval, the Minter sandstones, at a depth of about 6,775 ft typically consists of an upper Bee Brake sandstone and a lower Angelina sandstone. A detailed study of a conventional core in the center of the field reveals a 15-ft-thick Minter interval bounded above and below by sealing shales and lignites of lower delta plain marsh facies. The upper 4-ft-thick Bee Brake is a very fine silty sandstone with characteristics of a small overbank or crevasse splay deposit. The lower 3-ft-thick oil-producing Angelina sandstone consists of very fine and fine sandstone of probable overbank or crevasse facies. Cumulative production from the Angelina is about 1.8 million stock-tank barrels of oil. Special core analysis data (capillary pressure, relative permeability, and waterflood recovery) have been used to develop a simulation model of the two reservoirs in the Minter. This model incorporates the geologic and engineering complexities noted during evaluation of the field area. Operators can use the model results in this field to design an optimal development plan for enhanced recovery.

  2. Organic facies characteristics of the Pliocene coaly units, central Anatolia, Ilgin (Konya / Turkey)

    NASA Astrophysics Data System (ADS)

    Altunsoy, Mehmet; Ozdoğan, Meltem; Ozcelik, Orhan; Ünal, Neslihan

    2015-04-01

    This study aims to determine organic facies characteristics of the Pliocene coaly units in the Ilgın (Konya, Central Anatolia, Turkey) area. Pliocene units (Dursunlu Formation) are composed of sandstone, siltstone, marl, mudstone and coal in the region. Lignite layers where coals are found and has a varying thickness between 100 - 300 m. Organic matter is composed predominantly of terrestrial material, with a minor contribution of algal and amorphous material. Organic matter in these units have generally low hydrogen index (HI) values and high oxygen index (OI) values, mostly characteristics type III kerogen (partly type II kerogen). Organic matters in the samples are immature to marginally mature in terms of organic maturation. Total organic carbon (TOC) values are generally between 0.03 and 51.7 %, but reach 53.4 % in the formation. Tmax values vary between 392 and 433 °C. Organic facies type C, CD and D were identified in the investigated units. C, CD and D facies are related to marl, mudstone and coal lithofacies. These facies are characterized by average values of HI around 102 (equivalent to type II/ III kerogene), TOC around 12.2 %, and an average of S2 of 14.6 mg HC/g of rock. The organic matter is terrestrial, partly oxidized / oxidized / highly oxidized , decomposed and reworked. Organic facies C and CD are the "gas-prone" facies but Organic facies D is nongenerative. Keywords: Central Anatolia, Pliocene, Organic Facies, Ilgın, Coal

  3. Carbonate facies and Landsat imagery of shelf off Belize, central America

    SciTech Connect

    Jordan, C.F. Jr.; Pusey, W.C. III; Belcher, R.C.; Borger, R.L.

    1985-02-01

    A reevaluation of Holocene sediments on the Belize shelf is based on (1) a newly constructed composite of 7 Landsat images, enhanced and registered to form a regional base map, and (2) a Holocene facies map based on a rigorous treatment of compositional and textural parameters for approximately 600 bottom samples. The sediments are mapped in terms usually applied to lithified carbonate rocks, allowing direct comparisons with carbonate facies in the subsurface. By combining Landsat imagery with this facies map, it is possible to point out the following geologic features: (1) major tectonic elements, such as the Maya Mountains, the Yucatan Plateau, several offshore bridges, and 3 large atolls, (2) major physiographic features such as the Belize barrier reef with its reef platform and crest, middle-shelf shoal deposits, middle-shelf patch reefs (including lagoon reefs or rhomboid reefs), (3) Holocene facies patterns with potential reservoir facies of foraminifera-grainstone bars, Halimeda grainstones, and branching-coral, encrusting red-algae boundstones, and (4) nearshore clastics and a sharp transition eastward to carbonate sediments. An understanding of Holocene facies patterns on the Belize shelf is important to the explorationist, because these facies patterns are living examples of exploration fairways and invite comparisons with several petroleum provinces: (1) Cretaceous reefs of Texas, (2) upper Paleozoic skeletal-grainstone bars in west Texas, and (3) Devonian reefs of the Alberta basin.

  4. Sedimentology and cyclicity in the Lower Permian De Chelly sandstone on the Defiance Plateau: Eastern Arizona

    SciTech Connect

    Stanesco, J.D. )

    1991-10-01

    Lithofacies in the De Chelly Sandstone consist of (1) a large-scale trough to tabular- and/or wedge-planar cross-stratified sandstone facies of large-scale eolian dune origin, (2) a small- to medium-scale, trough cross-stratified sandstone also of eolian dune origin, (3) a horizontally stratified, wind-rippled sandstone of sand sheet origin, (4) a wavy, horizontally stratified, wind-rippled sandstone of sabkha origin, and (5) a mud-draped ripple-laminated sandstone of mud-flat origin. The De Chelly Sandstone in the northern Defiance Plateau consists mainly of large-scale dune deposits. Stratigraphic sections in the middle of the plateau are dominated by small- to medium-scale dune and sand sheet deposits whereas those along the southern end of the plateau are composed largely of sabkha and supratidal mud-flat deposits. The lateral distribution of these facies suggests a north-south juxtaposition of central-erg, fore-erg, and mixed sabkha-supratidal depositional environments. Repetitive interbedding of facies in the De Chelly indicates at least twelve depositional cycles in which sabkha and/or supratidal to coastal-plain mud-flats were sequentially overridden by eolian sand sheets and cross-stratified dunes. Lateral and vertical facies relations within the lower and upper members of the De Chelly Sandstone record episodic expansion of the De Chelly erg southward. The comparative abundance of large-scale dune deposits in the upper member suggests that progradation was more extensive during latter stages of deposition. The intervening tongue of Supai Formation and the redbeds that overlie the upper member of the De Chelly at Bonito Canyon document northward transgression of sabkha and supratidal to coastal-plain mud-flat environments. Eolian dune deposition was restricted to the northern Defiance Plateau during deposition of these units.

  5. Upper Strawn (Desmoinesian) carbonte and clastic depositional environments, southeastern King County, Texas

    SciTech Connect

    Boring, T.H. )

    1990-02-01

    The Pennsylvanian upper Strawn Group of southeastern King County, Texas, provides a unique setting to study interactions between coeval carbonate and clastic deposition during the Desmoinesian. One of the most perplexing problems is the relationship of massive Pennsylvanian platform carbonates to shallow-water terrigenous clastic sediments. Within the study area, carbonate facies were deposited along the northern edge of the Knox-Baylor trough on the Spur platform, and terrigenous clastics were carried toward the Midland basin through the Knox-Baylor trough. Based on the analysis of subsurface cores, five carbonate lithofacies and four clastic lithofacies were recognized in southeastern King County, Texas. The distribution and geometry of these lithofacies are related to variations in the rate of subsidence in the Knox-Baylor trough, Pennsylvanian tectonics, deltaic progradation, avulsion, and compaction. The platform carbonates within the northern region of southeastern King County record environments within the carbonate platform complex, including middle platform, outer platform, algal mound, and platform margin. The quartzarenitic sandstones within the southern region of southeastern King County occur in a variety of complex depositional geometries, including distributary-bar fingers, lobate deltas, and offshore bars. Cores of these sandstones represent mainly the uppermost portion of the various sandstone bodies. The upper Strawn Group provides an attractive area for exploration geology. Both carbonates and clastics provide excellent reservoirs from a depth of approximately 5,000-6,000 ft. Total production within the area is over 100 million bbl of oil since the early 1940s. Multiple pay zones within a 600-ft interval also provide an added incentive for exploration. Areas within and around the Knox-Baylor trough deserve a detailed study due to these relatively shallow, unexplored, multiple pay zones.

  6. Source versus depositional controls on sandstone composition in a foreland basin: The El Imperial Formation (Mid Carboniferous-Lower Permian), San Rafael basin, western Argentina

    SciTech Connect

    Espejo, E.S. ); Lopez-Gamundi, O.R. . Frontier Exploration Dept.)

    1994-01-01

    The El Imperial Formation (mid-Carboniferous-Lower Permian) constitutes a progradational sandstone-rich succession deposited in the San Rafael foreland basin of western Argentina. Four facies associations have been identified: a basal glacial marine association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association are represented by prodelta and delta-front shales and subordinate fine sandstones (Facies A), deltaic platform, wave-reworked channel mouth-bar sandstones (Facies B), and fluvial-dominated distributary channel sandstones (Facies C). Analysis of framework grains of sandstone samples from Facies B and C shows two distinct mineral assemblages or petrofacies. The quartzose petrofacies is characterized by high contents of quartz and low percentages of feldspar and lithic grains. The quartzolithic petrofacies shows an increase in labile components, in particular lithic fragments, and a concomitant decrease in quartz. The quartzolithic petrofacies shows a source signature. Average detrital modes of sandstones from this petrofacies are similar to those from overlying fluvial sandstones. All wave-reworked, channel mouth-bar sandstones (Facies B) correspond compositionally to the quartzose petrofacies, whereas detrital modes from the distributary-channel sandstones (Facies C) fall into the quartzolithic petrofacies. This correspondence between depositional environment and petrofacies suggests a strong depositional influence on composition (depositional signature). Abrasion (mechanical breakdown) by wave action in shallow marine environments accounts for the quartz-rich nature and paucity of labile grains in the quartzose petrofacies.

  7. Volcanic Facies of the Lower Jurassic Talkeetna Formation, Iniskin Peninsula to Tuxedni Bay, Alaska Peninsula

    NASA Astrophysics Data System (ADS)

    Bull, K. F.

    2015-12-01

    The Lower Jurassic Talkeetna Formation (Jtk), a >1,000-km-long belt of vol­canic facies within the accreted intra-oceanic Talkeetna Arc has been characterized within the Talkeetna Mountains, but on the Alaska Peninsula Jtk facies have not previously been described in detail. Here we describe facies of the Jtk stretching from the Iniskin Peninsula to Tuxedni Bay. On the Iniskin Peninsula, a high concentration and great thickness of mafic to intermediate lavas, associated autobreccias and hyaloclastites, fluidal-clast breccias and possible pillows are suggestive of one or more submarine effusive eruption centers. Also volumetrically significant are non-stratified polymictic volcaniclastic breccia facies. Minor facies include thinly bedded volcaniclastic sandstone to pebble breccia-conglomerate facies, some of which are shard- and pumice-bearing pyroclastic deposits preserved in thinly bedded deposits, indicative of episodes of explosive volcanism and the eruption-fed nature of some of the deposits. North of Chinitna Bay, coherent facies tend to be thin and relatively small in volume. Volcaniclastic facies provide evidence of subaerial-fluvial deposition, and pyroclastic activity. Thinly bedded, laterally continuous beds locally exhibit cross-laminations, channel fills, normal grading and lenticular beds, and contain plant fossils. Within this sequence is a 10-m-thick pumice breccia containing fossilized logs, underlain by a thin, weakly laminated, pumice- and lithic-bearing volcaniclastic siltstone to sandstone. The log-bearing pumice breccia and the lithic-bearing laminated basal unit represent pyroclastic density current (PDC) facies deposited in a subaerial or possibly shallow aqueous environment. Underlying the PDC deposit are several 30-cm-thick maroon and olive green volcaniclastic fine-grained sandstone and siltstone beds containing channel fills, cross-beds and lenticular beds. Marbles exposed in the contact zone between the intrusions of Alaska

  8. Trace fossils and bioturbation in peritidal facies of the Potsdam-Theresa Formations (Cambrian-Ordovician), Northwest Adirondacks

    SciTech Connect

    Bjerstedt, T.W. ); Erickson, J.M. )

    1989-06-01

    The Cambrian-Ordovician Potsdam Sandstone, Theresa Formation, and Canadian correlatives in the St. Lawrence Lowlands preserve tide-dominated facies during the basal Cambrian transgression. Low intertidal sand flats in the upper Potsdam contain a Skolithos Ichnofacies dominated by Diplocraterion parallelum in clean, herringbone cross-bedded sandstones indicative of high tidal current energy. Wind-wave-driven longshore and tidal currents along a macrotidal coastline were funneled northeast-southwest by Precambrian topographic relief of up to 65 m. This relief is now expressed as the Thousand Islands of New York and Canada. The conformably overlying Theresa Formation preserves a shoaling-upward sequence of mixed clastic-carbonate facies. Shallow subtidal and peritidal facies contain a mixed Skolithos-Cruziana Ichnofacies in sharply alternating lithofacies consisting of gray, intensely bioturbated, poorly sorted calcareous sandstone, and meter-thick, white cross-bedded sandstone. The parallelism between ichnofacies and lithofacies indicates that environmental energy level and persistence rather than water depth controlled trace fossil distribution. Bioturbated sandstones contain a Cruziana ichnofacies of abundant deposit feeders including: Fustiglyphus , Gyrochorte , Neonereites uniserialis , Phycodes flabellum, Planolites beverlyensis, Rosselia socialis, and Teichichnus. Suspension feeders are represented by D. habichi, D. parallelum, Skolithos, Monocraterion, and possibly Palaeophycus tubularis. Scavenging or deposit-feeding arthropods are represented by rare Cruziana furrows. Cross-bedded sandstones contain a Skolithos Ichnofacies of shallow Skolithos and Monocraterion burrows, and an undescribed large epistratal eurypterid( ) trail.

  9. Internal-tide deposits in an Ordovician submarine channel: Previously unrecognized facies

    SciTech Connect

    Gao Zhenzhong; Eriksson, K.A. )

    1991-07-01

    A Middle Ordovician submarine-channel deposit in the southern Appalachians is capped by an interval of fine-grained, predominantly cross-laminated sandstones that are interpreted as internal-tide deposits. Two facies are recognized: (1) bidirectional cross-laminated, very fine grained sandstones, and (2) unidirectional cross-bedded and cross-laminated, medium- to fine-grained sandstones. Facies 1 is dominated by bidirectional cross-laminations that dip both landward and seaward parallel to the paleochannel axis. This facies is related to up-channel and down-channel currents caused by internal tides. Facies 2 has both low-angle, tabular cross-beds and cross-laminations that dip landward. The formative up-channel currents are attributed to superimposition of internal waves on internal tides. The vertical transition from high-concentration gravity-flow deposits to intercalated low-concentration turbidites and internal-tide deposits is related to a rise in sea level that resulted in storage of coarse debris landward of the submarine channel.

  10. Frisco City sandstone: Upper Jurassic play in southern Alabama

    SciTech Connect

    Montgomery, S.L.; Baria, L.R.; Handford, C.R.

    1997-10-01

    The Frisco City sandstone play in southern Alabama is an example of hydrocarbon entrapment on the flanks of basement erosional features, with principal reservoirs occurring in proximal alluvial-fan to marine shoreface facies. Productive fields are developed on four-way closures of complex geometry, with reservoir sandstones showing maximum thickness along the margins of basement highs that are roughly 1.3-5.18 km{sup 2} in size and have 136-151 m of relief. Detailed analysis of sandstone facies indicates a downdip progression from alluvial-fan through wadi, eolian, beach, tidal-flat, and shoreface deposits. A sequence stratigraphic model based on identification of backstepping strata representing successive transgressive events is useful in predicting maximum reservoir occurrence in the vicinity of inselbergs. Reservoir quality in productive sandstones is high, with porosities ranging from 13 to 27% and permeabilities of 50 md to 5 d. Hydrocarbon occurrence is related to the distribution of high-quality source rock in the Smackover Formation and to maturation history.

  11. Facies architecture and depositional environments of the Upper Cretaceous Kaiparowits Formation, southern Utah

    NASA Astrophysics Data System (ADS)

    Roberts, Eric M.

    2007-04-01

    The Kaiparowits Formation is an unusually thick package of Upper Cretaceous (late Campanian) strata exposed in Grand Staircase-Escalante National Monument of southern Utah, USA. The formation was deposited within the rapidly subsiding Cordilleran foreland basin as part of a thick clastic wedge derived from sources in the Sevier orogenic belt, thrust sheets in southeastern Nevada and southern California, and the Mogollon slope in southwestern Arizona. Channel systems in the Kaiparowits Formation shifted from northeastward to southeastward flow over time, and for a short period of time, sea level rise in the Western Interior Seaway resulted in tidally influenced rivers and/or estuarine systems. Thick floodbasin pond deposits, large suspended-load channels, and poorly developed, hydromorphic paleosols dominate the sedimentary record, and all are suggestive of a relatively wet, subhumid alluvial system. This is supported by extremely rapid sediment accumulation rates (41 cm/ka), and high diversity and abundance of aquatic vertebrate and invertebrate fossils. Facies and architectural analysis was performed on the Kaiparowits Formation, resulting in the identification of nine distinct facies associations: 1) intraformational conglomerate, 2) mollusc-shell conglomerate, 3) major tabular sandstone, 4) major lenticular sandstone, 5) minor tabular and lenticular sandstone, 6) finely laminated, calcareous siltstone, 7) inclined heterolithic sandstone and mudstone, 8) sandy mudstone, and 9) carbonaceous mudstone. These facies associations are interpreted as: 1) channel lags, 2) rare channel-hosted storm beds, 3) meandering channels, 4) anastomosing channels, 5) crevasse splays and crevasse channels, 6) lakes, 7) tidally influenced fluvial and/or estuarine channels, 8) mud-dominated floodplains, and 9) swamps and oxbow lakes. Based on this analysis, the formation is subdivided into three informal units, representative of gross changes in alluvial architecture, including facies

  12. Sedimentary facies in submarine canyons

    NASA Astrophysics Data System (ADS)

    Sumner, E.; Paull, C. K.; Gwiazda, R.; Anderson, K.; Lundsten, E. M.; McGann, M.

    2013-12-01

    Submarine canyons are the major conduits by which sediment, pollutants and nutrients are transported from the continental shelf out into the deep sea. The sedimentary facies within these canyons are remarkably poorly understood because it has proven difficult to accurately sample these heterogeneous and bathymetrically complex environments using traditional ship-based coring techniques. This study exploits a suite of over 100 precisely located vibracores collected using remotely operated vehicles in ten canyons along the northern Californian margin, enabling better understanding of the facies that exist within submarine canyons, their distribution, and the processes responsible for their formation. The dataset reveals three major facies types within the submarine canyons: extremely poorly sorted, coarse-grained sands and gravels with complex and indistinct internal grading patterns and abundant floating clasts; classical normally graded thin bedded turbidites; and a variety of fine-grained muddy deposits. Not all facies are observed within individual canyons, in particular coarse-grained deposits occur exclusively in canyons where the canyon head cuts up to the modern day beach, whereas finer grained deposits have a more complex distribution that relates to processes of sediment redistribution on the shelf. Pairs of cores collected within 30 meters elevation of one another reveal that the coarse-grained chaotic deposits are restricted to the basal canyon floor, with finer-grained deposits at higher elevations on the canyon walls. The remarkable heterogeneity of the facies within these sediment cores illustrate that distinctive processes operate locally within the canyon. In the authors' experience the canyon floor facies represent an unusual facies rarely observed in ancient outcrops, which potentially results from the poor preservation of ancient coarse-grained canyon deposits in the geological record.

  13. Organic facies characteristics of the Carboniferous Pamucakyayla Formation, western Taurus, Antalya Nappes, Kemer (Antalya/Turkey)

    NASA Astrophysics Data System (ADS)

    Bertan Gulludag, Cevdet; Altunsoy, Mehmet; Ozcelik, Orhan

    2015-04-01

    The study area is located in the western part of the Taurus Belt (SW Turkey). This region exhibits a complex structure involving two autochthonous units surrounded and imbricated with three allochthonous complexes. Antalya Nappes is a complex tectonic imbricate structure including sedimantary and ultrabasic rocks. In this study, organic facies characteristics of Carboniferous coaly units in the Pamucakyayla region (Kemer, Antalya-Turkey) were examined. The Carboniferous Pamucakyayla Formation, which is characterized by sandstone, claystone, marl and coaly units. This units includes different levels of coal seams in different thicknesses. Organic matter is composed predominantly of woody and amorphous material, with a minor contribution of planty and coaly material. Kerogen in the deposits is type II/III, as indicated by organic petrographic observations and Rock-Eval data. Total organic carbon (TOC) values are generally between 0.01 and 1.44 %, but reach 5.81 % in the formation. Tmax values vary between 446 and 451 °C and indicate mature zone (Based on the value of 0.25 % TOC). Organic facies type BC, C and CD were identified in the investigated units. Organic facies BC is related sandstoneand marl lithofacies. This facis is deposited under an anoxic water column in a fine grained clastics, where rapid deposition creates anoxia in the sediments after deposition. This facies is characterized by average values of HI around 317 (equivalent to type II kerogene), TOC around 0.02 %, and an average of S2 of 0.04 mg HC/g of rock. Organic facies C is related to sandstone, marl and coal lithofacies. This facies is characterized by average values of HI around 176 (equivalent to type III kerogene), TOC around 0.19 %, and an average of S2 of 0.03 mg HC/g of rock. The organic matter is partly oxidized, and terrestrial. Organic facies C is the "gas-prone" facies. Organic facies CD is related to limestone, marl and coal lithofacies. This facies is characterized by average values

  14. Depositional facies, petrofacies, and diagenesis of siliciclastics of Morrow and Springer rocks, Anadarko Basin, Oklahoma

    USGS Publications Warehouse

    Keighin, C. William; Flores, Romeo M.

    1989-01-01

    Investigations of 6,500 ft of core and -100 thin-sectioned core samples from 30 drill holes from the Oklahoma Panhandle to the southeast part of the Anadarko basin, Oklahoma, have led to the recognition of three depositional facies of the Springer and Morrow Formations of Mississippian and Pennsylvanian age, as recognized by geologists working in the subsurface of the Midcontinent region. Lithofacies include (1) fluvial-influenced coastal (FIC), (2) tidal-influenced nearshore (TINS), and (3) mixed, which shows mixed tidal and non-tidal marine influence (MT/NTM). The FIC facies is restricted to down-hole depths of 4,400-8,000 ft; the TINS facies is recognized only between down-hole depths of 4,000 and 18,000 ft. Thin-section study of sandstone indicates that quartz arenite is the most common rock type in both the FIC and TINS facies. Subarkose is present, but not common, in the FIC facies. Sublitharenite is moderately common in the TINS facies. Calcite skeletal fragments, mainly of brachiopods and crinoids, are more abundant in the FJC facies than in the TINS facies. The mixed facies includes quartz arenite, subarkose, and sublitharenite. Iron-bearing carbonate cements are observed in rocks of all three depositional facies. Porosity is typically 12,000 ft. Thin films of bitumen have inhibited the effects of diagenesis in some samples. Fractures are identified in core samples, but are rare in thin sections. Porosity is due primarily to dissolution of glauconite, clays or clayey matrix, and some framework grains, but many dissolution pores are partly or completely filled with various clays, and only microporosity remains.

  15. Petrology and reservoir paragenesis in the Sussex B sandstone of the Upper Cretaceous Cody Shale, House Creek and Porcupine fields, Powder River basin, Wyoming

    SciTech Connect

    Not Available

    1992-01-01

    This book of reservoir paragenesis includes detailed descriptions of the petrology of depositional facies of the Sussex B sandstone of the Sussex Sandstone Member of the Upper Cretaceous Cody Shale in the House Creek and Porcupine fields, Powder River basin, Wyoming.

  16. Petrology and reservoir paragenesis in the Sussex 'B' sandstone of the upper Cretaceous Cody Shale, House Creek and Porcupine Fields, Powder River Basin, Wyoming

    SciTech Connect

    Higley, D.K.

    1991-05-03

    Using petrologic and sedimentologic studies, the paper characterizes the influence of sedimentologic and petrologic variations on reservoir heterogeneity in the Sussex 'B' sandstone in the House Creek and Porcupine fields, Powder River Basin, Wyoming. Effects of authigenic minerals on reservoir properties are described in detail for selected inter-ridge and ridge facies sandstones.

  17. The complex facies architecture and emplacement sequence of a Miocene submarine mega-pillow lava flow system, Muriwai, North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Bear, A. N.; Cas, R. A. F.

    2007-02-01

    The early Miocene Waiatarua Formation at Maori Bay, Muriwai, North Island, New Zealand consists of a complex association of basaltic andesite volcanic facies including entablature-jointed thick massive facies, colonnade-jointed thin massive sheet facies, mega-pillow facies, normal pillow facies and minor associated fragmental facies, including vitric sandstone and breccia interpreted as hyaloclastite and peperite. Field observations suggest that the facies, which form the Waiatarua Formation lava, were emplaced as multiple flow lobes in a single lava flow from one sustained eruption. Magma discharge rate at the vent was high; however magma supply rate to the more distal and lateral portions of the flow, as its surface area increased, varied considerably. Higher magma supply rates produced thick, massive and thin sheet facies, whereas mega-pillow facies and normal pillow facies were produced contemporaneously with the thick and thin massive sheet facies but were restricted to portions of the distal flow subjected to lower magma supply rates. The evolution of the Waiatarua formation lava flow at Maori Bay has been reconstructed from the complex facies architecture. This suggests that the propagation of the lava involved 7 discrete lobes that were emplaced successively.

  18. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in Frio Fluvial-Deltaic reservoirs of South Texas. Technical progress report, April 1, 1994--June 30, 1994

    SciTech Connect

    Tyler, N.; Dutton, S.

    1994-06-30

    Advanced reservoir characterization techniques are being applied to selected reservoirs in the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) trend of South Texas in order to maximize the economic producibility of resources in this mature oil play. More than half of the reservoirs in this depositionally complex play have already been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery methods. This project is developing interwell-scale geological facies models and assessing engineering attributes of Frio fluvial-deltaic reservoirs in selected fields in order to characterize reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. The results of these studies will lead directly to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling. Work during the second project quarter of 1994 focused on continuation of Phase 2 tasks associated with characterizing stratigraphic heterogeneity in selected Frio fluvial-deltaic sandstone reservoirs. Playwide reservoir assessment continued as reservoir engineering data from fields throughout the Frio Fluvial-Deltaic Sandstone trend were grouped within stratigraphic sub-intervals in order to characterize general reservoir heterogeneity, evaluate production behavior, and assess remaining resource potential in middle Frio, lower Frio, and upper Vicksburg reservoir sandstones.

  19. Stochastic reconstruction of sandstones

    PubMed

    Manwart; Torquato; Hilfer

    2000-07-01

    A simulated annealing algorithm is employed to generate a stochastic model for a Berea sandstone and a Fontainebleau sandstone, with each a prescribed two-point probability function, lineal-path function, and "pore size" distribution function, respectively. We find that the temperature decrease of the annealing has to be rather quick to yield isotropic and percolating configurations. A comparison of simple morphological quantities indicates good agreement between the reconstructions and the original sandstones. Also, the mean survival time of a random walker in the pore space is reproduced with good accuracy. However, a more detailed investigation by means of local porosity theory shows that there may be significant differences of the geometrical connectivity between the reconstructed and the experimental samples. PMID:11088546

  20. Eustatic and salt-tectonic controls on sequence development, northern east Texas basin

    SciTech Connect

    Demarest, J.M. II; Ehman, K.D. )

    1990-05-01

    Detailed log and seismic interpretation of the Woodbine/Eagle Ford interval in the vicinity of the Hainesville dome of east Texas resulted in the recognition of salt-tectonic and eustatic controls on depositional patterns. Major cycles of transgression and regression within this interval correspond to eustatic cycles recognized worldwide. The late Cenomanian lowstand resulted in the deposition of fluvial Woodbine sandstones above the marine Maness Shale (93 Ma). Transgressive and highstand marine shales of the Eagle Ford rest above the fluvial Woodbine sands. A late Turonian sequence boundary (90 Ma) separates the highstand shales of the Eagle Ford from the lowstand and transgressive marine sands and shales of the sub-Clarksville. The section is capped by the transgressive Austin Chalk. Between the Woodbine (93 Ma) and the sub-Clarksville (90 Ma), the Hainesville salt dome evolved from a nonpiercement to a piercement salt dome. This evolution of the Hainesville dome caused the area adjacent to the present-day dome to change from a structural high to a rapidly subsiding basin adjacent to the dome. With the rapid loss of salt into the piercement dome around 92 Ma, conditions adjacent to the dome changed from subaerial onlapping of the Woodbine fluvial facies to distal downlapping of the Eagle Ford marine shales into the center of the Hainesville withdrawal syncline. Thus, the detailed timing of salt movement is recorded in the thickness and facies distribution around the salt dome within the context of major global eustatic cycles.

  1. Metamorphic facies map of Alaska

    SciTech Connect

    Dusel-Bacon, C.; O-Rourke, E.F.; Reading, K.E.; Fitch, M.R.; Klute, M.A.

    1985-04-01

    A metamorphic-facies of Alaska has been compiled, following the facies-determination scheme of the Working Group for the Cartography of the Metamorphic Belts of the World. Regionally metamorphosed rocks are divided into facies series where P/T gradients are known and into facies groups where only T is known. Metamorphic rock units also are defined by known or bracketed age(s) of metamorphism. Five regional maps have been prepared at a scale of 1:1,000,000; these maps will provide the basis for a final colored version of the map at a scale of 1:2,500,000. The maps are being prepared by the US Geological Survey in cooperation with the Alaska Division of Geological and Geophysical Surveys. Precambrian metamorphism has been documented on the Seward Peninsula, in the Baird Mountains and the northeastern Kuskokwim Mountains, and in southwestern Alaska. Pre-Ordovician metamorphism affected the rocks in central Alaska and on southern Prince of Wales Island. Mid-Paleozoic metamorphism probably affected the rocks in east-central Alaska. Most of the metamorphic belts in Alaska developed during Mesozoic or early Tertiary time in conjuction with accretion of many terranes. Examples are Jurassic metamorphism in east-central Alaska, Early Cretaceous metamorphism in the southern Brooks Range and along the rim of the Yukon-Kovyukuk basin, and late Cretaceous to early Tertiary metamorphism in the central Alaska Range. Regional thermal metamorphism was associated with multiple episodes of Cretaceous plutonism in southeastern Alaska and with early Tertiary plutonism in the Chugach Mountains. Where possible, metamorphism is related to tectonism. Meeting participants are encouraged to comment on the present version of the metamorphic facies map.

  2. Effects of primary sedimentary processes on reservoir quality of Deep Wilcox (Eocene) sandstones in Fordoche field, Louisiana

    SciTech Connect

    Lemoine, R.C.; Moslow, T.F.; Lowry, P.

    1987-05-01

    The initial discovery and subsequent development of Fordoche field established a Deep Wilcox production trend in south-central Louisiana. Production in the field occurs within five intervals: the W4, W5, W8, W12, and W15 sandstones. The W8 and W12 sandstones are the most prolific. They represent shoreface sequences which formed at or near the shelf margin. Cumulative hydrocarbon production from these sandstones is in excess of 22 million bbl of oil and 151 bcf of gas. Over 1100 ft (335 m) of conventional core from the W8 and W12 sandstones in six wells were analyzed and compared to petrophysical data to effectively characterize reservoir quality. Primary sedimentation patterns (i.e., physical and biogenic sedimentary structures and sequences) are the dominant control on reservoir quality throughout the field. Burrowed to bioturbated (> 75% burrowed) lower shoreface sandstones possess relatively high average porosity values (16.7%); however, permeability values are extremely low (< 0.2 md). Clay-lined burrow walls create numerous permeability barriers which significantly alter fluid flow patterns within this facies. In contrast, massive to burrowed middle shoreface sandstones, although possessing similar average porosity values (19.8%), have substantially higher average permeability values (8.6 md). Within the middle shoreface facies, higher wave energies winnow the fine-grained silts and clays, resulting in the deposition of a clean, well-sorted sandstone. The entire sequence coarsens upward in both grain size and percent sand and is overlain by a thin (3.5 ft; 1.0 m), tightly cemented calcareous sandstone. Average thickness of the middle shoreface facies in Fordoche field is 23 ft (7.0 m) with stacked sequences within the W12 sandstone as thick as 57 ft (17.4 m) of high reservoir quality sandstones.

  3. Porosity development in deep sandstones, Taranaki Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Collen, J. D.; Newman, R. H.

    Reservoir quality in the Taranaki Basin is controlled by both depositional facies and diagenesis. High initial porosities and permeabilities in manyfluvial and littoral sandstones directed fluid flow such that these facies underwater widespread cementation by silica, carbonate and authigenic clays, and later dissolution of carbonates. Current commercial production of hydrocarbons in mainly from secondary, dissolution porosity in sandstones at depths of 1750-3600 m. Recent studies suggest that oil may not be released from terrestrial source rocks in western New Zealand until depths of 5.5 km or more. Knowledge of porosity development at such depths is therefore essential for understanding migration pathways and the controls on hydrocarbon accumulation. Organic species and/or carbon dioxide evolved from kerogen before liquid hydrocarbons are important to the formation of secondary porosity in sandstones by carbonate dissolution. Further, hydrocarbon migration should follow soon after the evolution of these, in order that re-cementation does not occur. High resolution nuclear magnetic resonance (NMR) spectroscopy shows that in western New Zealand basins, the evolution of solvents continues to at least 4 km and may persist almost until the expulsion of liquid hydrocarbons.

  4. Predicting Facies Patterns within Fluvial Channel Belts

    NASA Astrophysics Data System (ADS)

    Willis, B. J.; Sech, R.; Sun, T.; Pyrcz, M.

    2014-12-01

    Reservoirs (aquifers) in fluvial channel belt sandstones can have very different subsurface flow behavior depending on the degree and distribution of internal heterogeneities. Fluvial channel belts are composed of multiple "storeys" formed as individual channel segments increase in sinuosity and then are cut off and abandoned. Heterogeneities are defined by depositional variations across storeys and inter-story connectivity patterns along the channel belt. Although commonly inferred to reflect the formative river pattern (sinuosity & braiding), the spatial arrangement of facies depend most directly on the relative preservation of deposits formed within different areas of the migrating channels and the lateral stacking arrangement of storeys due to style of bend cutoff. Grains are poorly sorted across the inner bank along upstream parts of channel bends and become better sorted laterally in downstream areas adjacent to a deeper thalweg scour. If deposition occurs evenly along the entire inner bank (bar), this grain size pattern leads to an elliptical body in planview with weak vertical grain size trends upstream and more fining-upward trend downstream. As channel bend segments migrate to a greater extent downstream, preserved inner-bank-bar deposits are increasingly dominated by upward-fining deposits and more outer-bank-deposits are preserved ("concave bank" deposits). Although concave bank deposits have highly variable character in different systems, vertical-grainsize trends tend to be weaker in straighter systems dominated by downstream-accretion, and more strongly upward-fining in higher sinuosity systems where these deposits form by eddy accretion or low flow aggradation. River cutoffs of straighter channel segments abandon slowly, leading to more gradual vertical fining. Subsurface heterogeneity prediction requires documentation of shape and character of deposits preserved in different zones within the channel (upstream and downstream inner bank, concave bank

  5. New Ulm field: an example of Cretaceous shelf-slope instability in east Texas

    SciTech Connect

    Pinero, E.

    1984-04-01

    The New Ulm field in Austin County, Texas, is an example of the structural and stratigraphic complexity above the Cretaceous Edwards shelf margin of east Texas. Deep wells and improved seismic data provide documentation of structural patterns and deepwater facies not previously considered in the Gulf Coast reservoir play modeling. Study of the data implies the Late Cretaceous to Eocene section was deposited along a shelf-slope break. Late Cretaceous, pre-Midway sedimentation was affected by structurally induced slope instability, and consequent gravity faulting and slumping resulted in an irregular sea-floor surface. Paleocene Midway sands were carried onto this surface by storm-generated density currents where the uneven topography caused deposition in constructional channels. Continued deposition of the fluvio-deltaic Wilcox on this surface caused faulting and folding by differential compaction. The folds are minor and the faults small and steep, not like the typical large growth faults of the Gulf Coast. Upper Wilcox sediments were progressively less disturbed as the region stabilized. New Ulm field production includes gas from the Midway Formation and oil and gas from the Wilcox Group. Midway reservoirs are stratigraphic, consisting of fluvio-deltaic sandstones within faulted anticlines. This study adds evidence to data describing shelf-slope geology along the Edwards margin. The setting can be a new type of hydrocarbon play in the Gulf Coast.

  6. Groundwater flow, late cementation, and petroleum accumulation the Permian Lyons Sandstone, Denver basin

    SciTech Connect

    Lee, M.K.; Bethke, C.M. )

    1994-02-01

    The gray diagenetic facies of the Permian Lyons Sandstone, associated with all known petroleum accumulations in the formation, formed late in the history of the Denver basin as an alteration product of the formation's red facies. The red facies that makes up most of the sandstone contains iron oxide coating, quartz overgrowths and calcite cements. The gray facies, which occurs locally in the deep basin, is distinguished by pore-filling dolomite and anhydrite cements and by a lack of iron oxide and calcite. The dolomite and anhydrite cements overlie bitumen that was deposited by migrating oil, and hence formed after oil was first generated in the basin, late in the Cretaceous or early in the Tertiary. The isotopic composition of oxygen in the dolomite ranges to such light values that the cement must have formed deep in the basin in the presence of meteoric water. The gray facies likely formed in a regime of groundwater flow resulting from Laramide uplift of the Front Range during the Tertiary. In our model, saline groundwater flowed eastward through the Pennsylvanian Fountain Formation and then upwelled along the basin axis, where is discharged into the Lyons Sandstone. The saline water mixed with more dilute groundwater in the Lyons, driving a reaction that dissolved calcite and, by a common-ion effect, precipitated dolomite and anhydrite. The facies' gray color resulted from reduction of ferric oxide in the presence of migrating oil or the Fountain brine. Underlying source beds by this time had begun to generate petroleum, which migrated by buoyancy into the Lyons. The association of the gray facies with petroleum accumulations can be explained if the Fountain brines discharged across aquitards along the same fractures that transmitted oil. As petroleum accumulated in the Lyons, the newly formed cements prevented continued migration, as is observed in shallower strata, by sealing oil into the reservoirs from which it is produced today. 77 refs., 16 figs., 5 tabs.

  7. Stratigraphy and sedimentology of Kincaid Formation, Midway Group (Paleocene), Upper Rio Grande Embayment, Texas

    SciTech Connect

    Roy, E.C. Jr.

    1984-09-01

    Sedimentary rocks of the Kincaid Formation crop out along the northern and western edges of the Rio Grande Embayment. Siltstones are exposed at the type locality of the Kincaid Formation along the Frio River in Uvalde County, Texas. On the east and south, the Kincaid Formation changes facies to richly fossiliferous carbonate rocks; however, basinward, it grades into a shale facies that contains interbedded units of fine-grained sandstone. At the type locality of the Kincaid Formation, approximately 30 ft (9 m) of massive siltstone grades upward into a very silty limestone unit. Bedding is poorly defined throughout the section, largely the result of intensive bioturbation. The grain size of the siltstone increases upward, ranging from medium to coarse. Clay content in the siltstone decreases upward as the amount of calcareous material increases. The upper 4-6 ft (1.2-1.8 m) may actually be considered a silty limestone. A dramatic facies change is present along the outcrop both east and south of the type section. To the east, the Kincaid Formation is composed of glauconitic and highly fossiliferous limestone. The siltstone present at the type locality thins eastward and is absent less than 20 mi (32 km) away. Eighty miles (130 km) to the south, along the Rio Grande River, approximately 45 ft (14 m) of limestone and shale comprise the Kincaid Formation. These early Paleocene sediments are interpreted to be shallow marine in origin. The siltstone represents a shallow sublittoral shoreface environment whereas the limestones on the east and south were deposited in shallow nearshore environments beyond the reach of clastic deposition.

  8. Silurian and Devonian in Vietnam—Stratigraphy and facies

    NASA Astrophysics Data System (ADS)

    Thanh, Tống Duy; Phương, Tạ Hoàng; Janvier, Philippe; Hùng, Nguyễn Hữu; Cúc, Nguyễn Thị Thu; Dương, Nguyễn Thùy

    2013-09-01

    Silurian and Devonian deposits in Viet Nam are present in several zones and regions, including Quang Ninh, East Bac Bo, and West Bac Bo Zones of the Bac Bo Region, the Dien Bien-Nghe An and Binh Tri Thien Zones of the Viet-Lao Region, and the South Trung Bo, and Western Nam Bo Zones of the South Viet Nam Region (Fig. 1). The main lithological features and faunal composition of the Silurian and Devonian Units in all these zones are briefly described. The Silurian consists of deep-water deposits of the upper parts of the Co To and Tan Mai Formations in the Quang Ninh Zone, the upper parts of the Phu Ngu Formation in the East Bac Bo Zone and the upper parts of the Long Dai and Song Ca Formations in the Viet-Lao Region. Shallow water facies Silurian units containing benthic faunas are more widely distributed, including the upper part of the Sinh Vinh and Bo Hieng Formations in the West Bac Bo Zone, the Kien An Formation in the Quang Ninh Zone, and, in the Viet-Lao Region, the Dai Giang Formation and the upper part of the Tay Trang Formation. No Lower and Middle Devonian deposits indicate deep water facies, but they are characterized by different shallow water facies. Continental to near shore, deltaic facies characterize the Lower Devonian Song Cau Group in the East Bac Bo Zone, the Van Canh Formation in the Quang Ninh Zone, and the A Choc Formation in the Binh Tri Thien Zone. Similar facies also occur in the Givetian Do Son Formation of the Quang Ninh Zone, and the Tan Lap Formation in the East Bac Bo Zone, and consist of coarse terrigenous deposits—cross-bedded conglomerates, sandstone, etc. Most Devonian units are characterized by shallow marine shelf facies. Carbonate and terrigenous-carbonate facies dominate, and terrigenous facies occur in the Lower and Middle Devonian sections in some areas only. The deep-water-like facies is characteriztic for some Upper Devonian formations in the Bac Bo (Bang Ca and Toc Tat Formations) and Viet-Lao Regions (Thien Nhan and

  9. Factors controlling reservoir quality in tertiary sandstones and their significance to geopressured geothermal production. Annual report, May 1, 1979-May 31, 1980

    SciTech Connect

    Loucks, R.G.; Richmann, D.L.; Milliken, K.L.

    1980-07-01

    Differing extents of diagenetic modification is the factor primarily responsible for contrasting regional reservoir quality of Tertiary sandstones from the Upper and Lower Texas Gulf Coast. Detailed comparison of Frio sandstones from the Chocolate Bayou/Danbury Dome area, Brazoria County, and Vicksburg sandstones from the McAllen Ranch Field area, Hidalgo County, reveals that extent of diagenetic modification is most strongly influenced by (1) detrital mineralogy and (2) regional geothermal gradients. Vicksburg sandstones from the McAllen Ranch Field area are less stable, chemically and mechanically, than Frio sandstones from the Chocolate Bayou/Danbury dome area. Vicksburg sandstones are mineralogically immature and contain greater proportions of feldspars and rock fragments than do Frio sandstones. Thr reactive detrital assemblage of Vicksubrg sandstones is highly susceptible to diagenetic modification. Susceptibility is enhanced by higher than normal geothermal gradients in the McAllen Ranch Field area. Thus, consolidation of Vicksburg sandstones began at shallower depth of burial and precipitation of authigenic phases (especially calcite) was more pervasive than in Frio sandstones. Moreover, the late-stage episode of ferroan calcite precipitation that occluded most secondary porosity in Vicksburg sandstones did not occur significantly in Frio sandstones. Therefore, regional reservoir quality of Frio sandstones from Brazoria County is far better than that characterizing Vicksburg sandstones from Hidalgo County, especially at depths suitable for geopressured geothermal energy production.

  10. Ferron sandstone - stratigraphy and reservoir analogs, East-Central Utah

    SciTech Connect

    Anderson, P.B.; Ryer, T.A.; Chidsey, T.C. Jr.

    1996-06-01

    The Ferron Sandstone (Upper Cretaceous) crops out along the west flank of the San Rafael Swell of east-central Utah. Exposures were described on photomosaics to better define the stratigraphy, to enhance facies prediction, and establish rules for reservoir modeling within fluvial-deltaic rocks. Major regressive cycles are recognized as parasequence sets composed of several to many parasequences. Each of the seaward-stepping parasequence sets recognized in the Ferron begins with a rapidly thickening and stratigraphically climbing, wave-modified shoreface. In later stages of progradation, deposition is dominated by river influences. Continued regression of the seaway is recorded in outcrop and shows a complex history of delta lobe progradation, switching, and abandonment. Onlapping and stacking of parasequences creates a collage of potential reservoir sweet spots, baffles, and barriers within a parasequence set. Shoreface and delta-front deposits of the older parasequences are commonly eroded by younger distributary and meanderbelt systems that fed younger parasequences of the parasequence sets. The result is numerous and locally thick channel sandstone bodies incised into shoreface and delta-front deposits. Published studies and recently completed work show that upper shoreface, stream mouth-bar, and channel sandstones constitute the best potential reservoir rocks within the Ferron Sandstone.

  11. CHARACTERIZATION OF SANDSTONE RESERVOIRS FOR ENHANCED OIL RECOVERY: THE PERMIAN UPPER MINNELUSA FORMATION, POWDER RIVER BASIN, WYOMING.

    USGS Publications Warehouse

    Schenk, C.J.; Schmoker, J.W.; Scheffler, J.M.

    1986-01-01

    Upper Minnelusa sandstones form a complex group of reservoirs because of variations in regional setting, sedimentology, and diagenetic alteration. Structural lineaments separate the reservoirs into northern and southern zones. Production in the north is from a single pay sand, and in the south from multi-pay sands due to differential erosion on top of the Upper Minnelusa. The intercalation of eolian dune, interdune, and sabkha sandstones with marine sandstones, carbonates, and anhydrites results in significant reservoir heterogeneity. Diagenetic alterations further enhance heterogeneity, because the degree of cementation and dissolution is partly facies-related.

  12. Texas Fires

    Atmospheric Science Data Center

    2014-05-15

    article title:  Wind-Whipped Fires in East Texas     View Larger Image ... western side of the storm stoked fires throughout eastern Texas, which was already suffering from the worst one-year drought on record ...

  13. Internal geometry, seismic facies, and petroleum potential of canyons and inner fan channels of the Indus submarine fan

    SciTech Connect

    McHargue, T.R.; Webb, J.E.

    1986-02-01

    The Indus Fan, the second largest submarine fan in the world, covers 1,250,000 km/sup 2/ (500,000 mi/sup 2/) and contains sediment more than 7 km (23,000 ft) thick. Multichannel (24-fold) CDP seismic data provide the bases for evaluating the Indus Fan and consist of four seismic facies. Of these, only the high-amplitude, discontinuous (H-D) facies is thought to contain reservoir-quality sandstones. The H-D facies is confined to the axes of leveed channels. Canyon-channel systems that fed the fan in the past can be divided into three zones. The degradational zone is composed of an erosional canyon complex filled by prodelta mud. The transitional zone, located near the canyon mouth, consists of superimposed channels that initially were erosional but eventually aggraded and developed levees. The headward termination of the H-D facies occurs in this zone. The aggradational zone consists of superimposed leveed channels confined solely by their own levees. The proximal termination of the H-D facies near canyon mouths implies the presence of reservoir-quality sandstone surrounded by source/seal mudstone in the transitional zone. This stratigraphic trapping geometry and structural leads may represent a vast, untapped petroleum province.

  14. Facies and facies association of the siliciclastic Brak River and carbonate Gemsbok formations in the Lower Ugab River valley, Namibia, W. Africa

    NASA Astrophysics Data System (ADS)

    Paciullo, F. V. P.; Ribeiro, A.; Trouw, R. A. J.; Passchier, C. W.

    2007-03-01

    The Neoproterozoic Zerrissene Turbidite Complex of central-western Namibia comprises five turbiditic units. From the base to the top they are the Zebrapüts Formation (greywacke and pelite), Brandberg West Formation (marble and pelite), Brak River Formation (greywacke and pelite with dropstones), Gemsbok River Formation (marble and pelite) and Amis River Formation (greywacke and pelites with rare carbonates and quartz-wacke). In the Lower Ugab River valley, five siliciclastic facies were recognised in the Brak River Formation. These are massive and laminated sandstones, classical turbidites (thick- and thin-bedded), mudrock, rare conglomerate and breccia. For the carbonate Gemsbok River Formation four facies were identified including massive non-graded and graded calcarenite, fine grained evenly bedded blue marble and calcareous mudrock. Most of these facies are also present in the other siliciclastic units of the Zerrissene Turbidite Complex as observed in other areas. The vertical facies association of the siliciclastic Brak River Formation is interpreted as representing sheet sand lobe to lobe-fringe palaeoenvironment with the abandonment of siliciclastic deposition at the top of the succession. The vertical facies association of the carbonate Gemsbok Formation is interpreted as the slope apron succession overlain by periplatform facies, suggesting a carbonate slope sedimentation of a prograding depositional shelf margin. If the siliciclastic-carbonate paired succession would represent a lowstand relative sea-level and highstand relative sea-level, respectively, the entire turbidite succession of the Zerrissene Turbidite Complex can be interpreted as three depositional sequences including two paired siliciclastic-carbonate units (Zebrapüts-Brandberg West formations; Brak River-Gemsbok formations) and an incomplete succession without carbonate at the top (Amis River Formation).

  15. Detrital and authigenic clay minerals in lower Morrow Sandstones of eastern New Mexico

    SciTech Connect

    Mazzullo, J.; Mazullo, L.J.

    1984-01-01

    Sandstone reservoirs of the Morrow Formation of southeastern New Mexico are important natural gas reservoirs. Production from this unit is affected by the types and distributions of detrital and authigenic clay minerals present in the rocks. Thus, X-ray diffraction and scanning electron microscopic analyses of samples from the lower Morrow reservoirs were conducted to understand the types, morphologies, petrographic positions, and regional trends of clays in the unit. By far, authigenic kaolinite and chlorite are the major clays present in the lower Morrow sandstone reservoirs. The kaolinite content of the clay fraction of the formation can reach a maximum of 100%, whereas that of chlorite can be as high as 59%. When both are present, authigenic kaolinite and chlorite can effectively reduce much of the permeability of the sandstone reservoirs. Smectite, illite, and mixed-layer smectite-illite are relatively insignificant clays in the lower Morrow, except in certain small areas of the study area, and are largely detrital in origin. The distribution of smectite, illite, and mixed-layer smectite-illite reflects the depositional processes acting in each of the facies of the lower Morrow. These clays are most abundant in immature fluvial-deltai c and basinal sandstones and relatively deficient in reworked marine sandstones. Distribution of authigenic kaolinite and chlorite also mimics the facies pattern, but is not controlled by it. In the lower Morrow, kaolinite increases landward while chlorite increases toward the basinal facies. Successful treatment procedures for reservoir sandstones must differ with the different clay mineral types present.

  16. Fossil facies of the Greater Caspian region

    NASA Astrophysics Data System (ADS)

    Svitoch, A. A.

    2015-05-01

    The Pliocene-Pleistocene marine sediments of the Great Caspian region host various lithological fossil facies, which reflect specific sedimentation conditions caused by different structural-geomorphologic settings, tectonic regimes, climates, and hydrologies. The facies of shelf, epicontinental basins, ingression gulfs and estuaries, intermontane and mountainous basins, and deep-sea depressions form a hierarchy of geological bodies from types to subtypes. Paragenetic associations of fossil facies, which form various series in space and along the section, are typical of marine sediments.

  17. Upper Jurassic and Lower Cretaceous facies relationships in a passive margin basin, western North Atlantic

    SciTech Connect

    Prather, B.E.

    1988-02-01

    Correlation of facies from hydrocarbon-bearing continental and transitional marine sandstones to time-equivalent high-energy shelf-margin carbonates provide insight into hydrocarbon habitats of the Baltimore Canyon basin. These facies occur within a thick (> 10,000 ft) prograded wedge of shelf sediments in this passive margin basin. Wells drilled to test structural closures in shallow-water (< 600 ft) areas of Baltimore Canyon penetrate clastic facies which are time-equivalent to the downdip carbonate facies tested in deep-water wells. Numerous hydrocarbon shows, including a noncommercial gas and gas-condensate accumulation, occur with sandstone units that were deposited in prograding continental/fluvial and transitional marine environments located updip of the Oxfordian/Kimmeridgian carbonate shelf edge. The continental and transitional facies are overlain by a fine-grained deltaic complex which forms a regionally extensive top seal unit. The deltaic complex was deposited during aggradation of the Kimmeridgian through Berriasian shelf-margin carbonates penetrated by the deep-water wells. Deep-water wells (> 5000 ft) drilled off the continental shelf edge to test large structural closures along the downdip termination of the Upper Jurassic/Lower Cretaceous carbonate shelf edge encountered no significant hydrocarbon shows. Reservoir rocks in these wells consist of (1) oolite grainstone which was deposited within a shoal-water complex located at the Aptian shelf edge, and (2) coral-stromatoporoid grainstone and boundstone which formed an aggraded shelf-margin complex located at the Kimmeridgian through Berriasian shelf edge. Structural closures with reservoir and top seals are present in both updip and downdip trends. The absence of hydrocarbon shows in downdip carbonate reservoirs suggests a lack of source rocks available to charge objectives at the shelf margin.

  18. Geometry and reservoir heterogeneity of tertiary sandstones: a guide to reservoir continuity and geothermal resource development

    SciTech Connect

    Morton, R.A.; Ewing, T.E.

    1981-01-01

    External and internal continuity of Tertiary sandstones are controlled by various factors including structural trends, sand body geometry, and the distribution of mineral framework, matrix, and intersticies within the sand body. Except for the limits imposed by faults, these factors are largely inherited from the depositional environment and modified during sandstone compaction and cementation. Sandstone continuity affects energy exploration and production strategies. The strategies range in scope from regional to site-specific and closely parallel a sandstone hierarchy. The hierarchy includes subdivisions ranking from genetically related aquifer systems down to individual reservoirs within a fault-bounded sandstone. Volumes of individual reservoirs are 50% less to 200% more than estimated from conventional geologic mapping. In general, mapped volumes under-estimate actual volumes where faults are nonsealing and overestimate actual volumes where laterally continuous shale breaks cause reductions in porosity and permeability. Gross variations in these pore properties can be predicted on the basis of internal stratification and sandstone facies. Preliminary analyses indicate that large aquifers are found where barrier and strandplain sandstones parallel regional faults or where fluvial (meandering) channels trend normal to regional faults. Within these sand bodies, porosity and permeability are highest in large-scale crossbedded intervals and lowest in contorted, bioturbated, and small-scale ripple cross-laminated intervals.

  19. Hydrocarbon accumulations of Mississippian Berea sandstone in west-central West Virginia

    SciTech Connect

    Cox, D.L. )

    1988-08-01

    The Berea Sandstone is a widely recognized producer of oil and gas in the Appalachian basin. Subsurface mapping, core analysis, and production data from producing wells have been evaluated in west-central West Virginia, where the Berea Sandstone represents a wide range of nearshore and coastal environments. Fluvial system deposits are found in southern Jackson County as channel sands (Gay-Fink) and adjacent deltaic facies. Coastal sediments were deposited to the north as intertidal shoals, tidal flats, and coarse-grained tidal-creek point bars. Marine shelf sands are found to the west.

  20. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in Frio Fluvial-Deltaic reservoirs of south Texas. Technical progress report, April 1, 1996--June 30, 1996

    SciTech Connect

    Tyler, N.; Levey, R.A.

    1996-07-11

    Advanced reservoir characterization techniques have been applied to selected reservoirs in the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) trend of South Texas in order to maximize the economic producibility of resources in this mature oil play. More than half of the reservoirs in this depositionally complex play have already been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery methods. This project has developed interwell-scale geological facies models and has assessed engineering attributes of Frio fluvial-deltaic reservoirs in selected fields in order to characterize reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. Results of these studies led to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling.

  1. Elevated Uranium in Aquifers of the Jacobsville Sandstone

    NASA Astrophysics Data System (ADS)

    Sherman, H.; Gierke, J.

    2003-12-01

    The EPA has announced a new standard for uranium in drinking water of 30 parts per billion (ppb). This maximum contaminant level (MCL) takes effect for community water supplies December 2003. The EPA's ruling has heightened awareness among residential well owners that uranium in drinking water may increase the risk of kidney disease and cancer and has created a need for a quantified, scientific understanding of the occurrence and distribution of uranium isotopes in aquifers. The authors are investigating the occurrence of elevated uranium in northern Michigan aquifers of the Middle Proterozoic Jacobsville sandstone, a red to mottled sequence of sandstones, conglomerates, siltstones and shales deposited as basin fill in the 1.1 Ga Midcontinent rift. Approximately 25% of 300 well water samples tested for isotopic uranium have concentrations above the MCL. Elevated uranium occurrences are distributed throughout the Jacobsville sandstone aquifers stretching across Michigan's Upper Peninsula. However, there is significant variation in well water uranium concentrations (from 0.01 to 190 ppb) and neighboring wells do not necessarily have similar concentrations. The authors are investigating hydrogeologic controls on ground water uranium concentrations in the Jacobsville sandstone, e.g. variations in lithology, mineralogy, groundwater residence time and geochemistry. Approximately 2000' of Jacobsville core from the Amoco St. Amour well was examined in conjunction with the spectral gamma ray log run in the borehole. Spikes in equivalent uranium (eU) concentration from the log are frequently associated with clay and heavy mineral layers in the sandstone core. The lithology and mineralogy of these layers will be determined by analysis of thin sections and x-ray diffraction. A portable spectrometer, model GRS-2000/BL, will be used on the sandstone cliffs along Lake Superior to characterize depositional and lithologic facies of the Jacobsville sandstone in terms of

  2. Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study

    USGS Publications Warehouse

    Suping, P.; Flores, R.M.

    1996-01-01

    Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and converging, coeval fluvial channels laterally juxtaposed with floodplains containing ponds, lakes, and topogenous mires. The mires accumulated thin to thick peat/coal deposits that vary in vertical and lateral distribution between the two study areas. This difference is probably due to attendant sedimentary processes that affected the floodplain environments. The ancestral floodplains of the Modern Pearl River Delta were reworked by combined fluvial and tidal and estuarine processes. In contrast, the floodplains of the Permian Member D were mainly influenced by freshwater fluvial processes. In addition, the thick, laterally extensive coal zones of the Permian Member D may have formed in topogenous mires that developed on abandoned courses of anastomosing fluvial systems. This is typified by Seam 13-1, which is a blanket-like body that thickens to as much as 8 in but also splits into thinner beds. This seam overlies deposits of diverging and converging, coeval fluvial channels of the Sandstone D, and associated overbank-floodplain deposits. The limited areal extent of lenticular Pleistocene peat deposits of the Modern Pearl River Delta is due to their primary accumulation in topogenous mires in the central floodplains that were restricted by contemporaneous anastomosing channels.

  3. Lithological and geochemical facies of Shublik Formation (Triassic), North Slope, Alaska

    SciTech Connect

    Parrish, J.T.

    1985-04-01

    The Shublik Formation is a heterogeneous unit consisting of several distinct facies, including: (1) fossiliferous sandstone or siltstone; (2) glauconitic sandstone or siltstone; (3) siltstone, calcareous mudstone, or limestone with phosphate nodules; and (4) black, calcareous mudstone or black limestone, usually fossilferous. This sequence of lithologies is interpreted as having been deposited along an onshore-offshore (north to south) gradient. Bioturbation of the sediments is variable but generally decreases offshore. Organic carbon increases offshore, and phosphate increases from the paleoshoreline and decreases again farthest offshore. The distribution of glauconite, phosphate, and organic-carbon-rich rock is consistent with the facies expected in a zone that has a well-developed oxygen minimum. Glauconite is consistent with dysoxic conditions, and well-laminated, organic-carbon-rich rock in the offshore facies is consistent with anoxic conditions. High biologic productivity coupled with normal oceanic circulation may have caused the basin's low-oxygen conditions, as indicated by the presence of phosphate nodules and the extreme abundance of bivalves that have been interpreted to be pelagic. Phosphate indicates a high rate of supply of organic matter to the sediment-water interface, where it was mobilized from the organic matter within the anoxic zone, and reprecipitated at the zone's edges. Pelagic bivalves (Monotis and Halobia) are present in such large numbers as to suggest unusually abundant food supply; in addition, their distribution is consistent with mass dills, which are common among fish in zones.

  4. Facies mosaic in a fiord: Carboniferous-Permian Talchir Formation, India

    SciTech Connect

    Bose, P.K.; Mukhopadhyay, G.; Bhattacharya, H.N.

    1988-01-01

    Facies analysis of the basal 37m of the Carboniferous-Permian Talchir Formation is a glacier-fed bedrock trough in Dudhi nala, Bihar, India, provides insight into the pattern of sedimentation of course gravels in a fiord. Rapid transitions between 11 recognized facies, together with their complex organization, random variability in bed thickness, and differences in clast, shape, size, and composition indicate coalescence of fans developed from numerous point sources bordering the elongated trough. Converging slide masses and lodgment tillites on the slopes flanking the trough give way to sediment gravity flow deposits composed of an array of conglomerates (matrix and clast supported with normal, inverse of absence of grading), attendant turbidite sands, and prodelta mud. The rheology of the in-trough flows ranged from plastic laminar to fluidal turbulent in response to flow from slope to floor of the trough. Rapid calving of icebergs during the onset of deglaciation established a wave regime at the mouth of the trough and deposited cross-stratified sandstone replete with dripstones. The impact of large dripstones landing triggered turbidity currents. Continued rise in water level led to eventual preservation of the fan complex under onlapping wave-built shoal facies that grade into a sequence of upward-thinning hummocky cross-stratified sandstone beds virtually devoid of dripstones.

  5. Clinoform geometries, facies distributions, and exploration significance of a Campanian spit, Billings, Montana

    SciTech Connect

    Hanson, M.S. )

    1991-06-01

    A Campanian spit comprised of clinoform-bound sandstone wedges demarcates the base of the Eagle Sandstone along the rim-rocks surrounding Billings, Montana. The spit is connected to the Eagle strandline via a seismically defined northwest-southeast-trending basement fault which cores the Crooked Creek anticline. This recurrently active fault cut perpendicular to the Eagle strandline, localizing a fluviodeltaic headland which delivered an enormous volume of sand to the pendant spit. Detailed facies analysis of outcrop and subsurface data documents a strandline-parallel, southwesterly offlap of the sandstone wedges on the shallow shelf. Facies progressions within and across accretionary wedges define relative sea level movements during the genesis of the spit. Longshore and eddy currents, combined with a slow eustatic rise, forced a southwesterly migration of fine- to medium-grained sand. Spit progradation slowed and was ultimately terminated as the rate of eustatic rise overtook the rate of sediment supply. Spits resulting from similar/fault intersections are excellent exploration targets. The Billings spit spans 180 mi{sup 2} and reaches thickness exceeding 100 ft. A favorable reservoir/trap configuration results from the spit's lensoidal and potentially shale-encased geometry. Exploration for these spits must concentrate seaward and downcurrent of near-perpendicular fault/strand intersections.

  6. Relation between facies, diagenesis, and reservoir quality of Rotliegende reservoirs in north Germany

    SciTech Connect

    David, F.; Gast, R.; Kraft, T. )

    1993-09-01

    In north Germany, the majority of Rotliegende gas fields is confined to an approximately 50 km-wide east-west-orientated belt, which is situated on the gently north-dipping flank of the southern Permian basin. Approximately 400 billion m[sup 3] of natural gas has been found in Rotliegende reservoir sandstones with average porosities of depths ranging from 3500 to 5000 m. Rotliegende deposition was controlled by the Autunian paleo-relief, and arid climate and cyclic transgressions of the desert lake. In general, wadis and large dunefields occur in the hinterland, sebkhas with small isolate dunes and shorelines define the coastal area, and a desert lake occurs to the north. The sandstones deposited in large dunefields contain only minor amounts of illite, anhydrite, and calcite and form good reservoirs. In contrast, the small dunes formed in the sebkha areas were affected by fluctuations of the desert lake groundwaters, causing the infiltration of detrital clay and precipitation of gypsum and calcite. These cements were transformed to illite, anhydrite, and calcite-II during later diagenesis, leading to a significant reduction of the reservoir quality. The best reservoirs occur in the shoreline sandstones because porosity and permeability were preserved by early magnesium-chlorite diagenesis. Since facies controls diagenesis and consequently reservoir quality, mapping of facies also indicates the distribution of reservoir and nonreservoir rocks. This information is used to identify play area and to interpret and calibrate three-dimensional seismic data.

  7. Late Devonian to early carboniferous turbidite facies and basinal development of the Eastern Klamath Mountains, California

    NASA Astrophysics Data System (ADS)

    Watkins, Rodney

    1986-08-01

    The Late Devonian to Early Carboniferous Bragdon Formation, Eastern Klamath Mountains, California, is a thick turbidite sequence deposited as a submarine fan complex within an arc-related basin. Laminated mudstone and less abundant "classical" turbidites comprise most of the lower part of the Bragdon and represent a lower fan environment. Amalgamated beds of normally graded to massive sandstone and pebbly sandstone occur throughout the Bragdon but are most abundant in its upper half, where they are associated with very thick channel-fill beds of pebbly sandstone and conglomerate. The upper half of the Bragdon Formation represents a mid fan to upper fan environment, and it also includes closely interbedded "classical" turbidites interpreted as interchannel or levee deposits. An upper slope facies of bioturbated mudstone with an Early Carboniferous fauna occurs at the top of the formation. Clastic material in the Bragdon Formation indicates little contemporaneous vulcanism and was probably derived from Lower Paleozoic metasediments which were uplifted to the north. Deposition of the Bragdon was initiated by rifting and subsidence of an underlying Middle Devonian arc complex. Infilling of the resulting basin during the Late Devonian and Early Carboniferous is indicated by overlap of turbidite facies across Middle Devonian arc deposits and by an upward stratigraphic trend in the Bragdon from lower fan to upper fan and slope environments.

  8. Correlating organic facies and turbidite facies in a Hoh turbidite sequence (Miocene), Western Olympic Peninsula, Washington

    SciTech Connect

    Grady, M.T.

    1985-02-01

    The distribution of organic facies is a function of the environment of deposition. Within each turbidite facies, diverse depositional regimes are present that affect both the preservation and dispersal and organic matter. Proper identification of turbidite facies can lead to a proper prediction of organic content within a particular turbidite facies or turbidite facies association. The type section of the Brown's Point formation, a turbidite sequence within the Hoh rock assemblage, demonstrates the correlation between organic facies and turbidite facies, as defined by E. Mutti and F. Ricci-Lucchi. Turbidite facies can be matched to organic facies throughout the entire 4000 ft (1220 m) thick vertical section. Outer and middle fan turbidite associations have been analyzed and correlated for organic facies lateral continuity. Distribution of organic carbon concentrations and organic carbon type suggests a dominance of terrestrial input. TAI and R/sub 0/ analyses reflect a marginally mature thermal maturation level (R/sub 0/ = 0.5-0.6). Visual kerogen inspection reveals a mixed to structured kerogen with a predominance of type III/IV over type IV kerogen. Overall, maturation indices suggest a gas source with poor source potential for oil. Individual turbidite facies display a significant relationship to the amount, type, and level of maturation of organic matter present within each facies and facies association. Frontier basin analysis of turbidite sequences can be expedited by proper field identification of turbidite facies and subsequent geochemical analysis of the content, type, and maturation level of the organic matter present within each turbidite facies.

  9. Analysis of glacier facies using satellite techniques

    USGS Publications Warehouse

    Williams, R.S., Jr.; Hall, D.K.; Benson, C.S.

    1991-01-01

    Landsat-derived reflectance is lowest for exposed ice and increases markedly at the transient snow line. Above the slush zone is a gradual increase in near-infrared reflectance as a result of decreasing grain-size of the snow, which characterizes drier snow. Landsat data are useful in measuring the areal extent of the ice facies, the slush zone within the wet-snow facies, the snow facies (combined wet-snow, percolation and dry-snow facies), and the respective position of the transient snow line and the slush limit. In addition, fresh snowfall and/or airborne contaminants, such as soot and tephra, can limit the utility of Landsat data for delineation of the glacier facies in some cases. -from Authors

  10. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-02-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining the paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.

  11. Gravelly to sandy braidplain deposition in the buntsandstein-facies bohdašin formation in northeastern bohemia (Czechoslovakia)

    NASA Astrophysics Data System (ADS)

    Prouza, Vladimír; Tásler, Radko; Valín, Frantisek; Holub, Vlastimil

    The Buntsandstein-facies Bohdaín Formation in Northeastern Bohemia (Czechoslovakia) forms the Lower Triassic part of an extensive sequence of continental red beds of mainly Permian age and is conformably overlying the Upper Permian Bohuslavice Formation. The Bohdaín Formation in Czechoslovakia predominantly crops out in the Intra Sudetic Basin and in the eastern part of the Krkonoe Piedmont Basin. The Buntsandstein-facies red beds are hidden in many places underneath the cover of marine Cenomanian. The Bohdaín Formation is built up of three main lithofacies associations which in ascending order successively comprise polymictic sandstones and conglomerates, feldspathic sandstones and kaolinitic quartzose sandstones. Feldspathic and polymictic sandstones can partially substitute each other, whereas the kaolinitic quartzose sandstones are only present in the uppermost part of the unit. Polymictic sandstones and conglomerates contain gravel-size clasts of biotite gneisses, granitoids, rhyolites, granolites and other medium- to high-grade metamorphic rocks. The feldspathic sandstones either cover the polymictic sandstones and conglomerates or lap on the Upper Permian Bohuslavice Formation, thus pointing to some expansion of the basin. The suite of gravel-size clasts consists of milky quartz, translucent quartz, gneisses, granitoids, metaquartzites and lydites, indicating progressive maturing by advancing unroofing and increasing significance of recycling. The kaolinitic quartzose sandstones represent the climax of amelioration of textural and mineralogical maturity of the sediment material with reaching considerable amounts of monocrystalline quartz and polycrystalline quartzites both in the pebble and sand fraction. The boundary between the Lower Triassic Bohdaín Formation and the Upper Cretaceous is highlighted by numerous burrows within the uppermost layer of the kaolinitic quartzose sandstones which are infilled with glauconitic Cenomanian sand. The

  12. Reservoir characterization of Mesaverde (Campanian) bedload fluvial meanderbelt sandstones, northwestern Colorado

    SciTech Connect

    Jones, J.R. Jr.

    1984-04-01

    Reservoir characterization of Mesaverde meanderbelt sandstones is used to determined directional continuity of permeable zones. A 500-m (1600 ft) wide fluvial meanderbelt in the Mesaverde Group is exposed as laterally continuous 3-10-m (10-33-ft) high sandstone cliffs north of Rangely, Colorado. Forty-eight detailed measured sections through 3 point bar complexes oriented at right angles to the long axis of deposition and 1 complex oriented parallel to deposition were prepared. Sections were tied together by detailed sketches delineating and tracing major bounding surfaces such as scours and clay drapes. These complexes contain 3 to 8 multilateral sandstone packages separated by 5-20 cm (2-8 in.) interbedded siltstone and shale beds. Component facies are point bars, crevasse splays, chute bars, and floodplain/overbank deposits. Two types of lateral accretion surfaces are recognized in the point bar facies. Gently dipping lateral accretions containing fining-upward sandstone packages. Large scale trough cross-bedding at the base grades upward into ripples and plane beds. Steeply dipping lateral accretion surfaces enclose beds characterized by climbing ripple cross laminations. Bounding surfaces draped by shale lags can seal vertically stacked point bars from reservoir communication. Scoured boundaries allow communication in some stacked point bars. Crevasse splays showing climbing ripples form tongues of very fine-grained sandstone which flank point bars. Chute channels commonly cut upper point bar surfaces at their downstream end. Chute facies are upward-fining with small scale troughs and common dewatering structures. Siltstones and shales underlie the point bar complexes and completely encase the meanderbelt system. Bounding surfaces at the base of the complexes are erosional and contain large shale rip-up clasts.

  13. Influence of depositional environment and diagenesis on gas reservoir properties in St. Peter Sandstone, Michigan basin

    SciTech Connect

    Harrison, W.B. III; Turmelle, T.M.; Barnes, D.A.

    1987-05-01

    The St. Peter Sandstone in the Michigan basin subsurface is rapidly becoming a major exploration target for natural gas. This reservoir was first proven with the successful completion of the Dart-Edwards 7-36 (Falmouth field, Missaukee County, Michigan) in 1981. Fifteen fields now are known, with a maximum of three producing wells in any one field. The production from these wells ranges from 1 to more than 10 MMCFGD on choke, with light-gravity condensate production of up to 450 b/d. Depth to the producing intervals ranges from about 7000 ft to more than 11,000 ft. The St. Peter Sandstone is an amalgamated stack of shoreface and shelf sequences more than 1100 ft in thickness in the basin center and thinning to zero at the basin margins. Sandstone composition varies from quartzarenite in the coarser sizes to subarkose and arkose in the finer sizes. Thin salty/shaly lithologies and dolomite-cemented sandstone intervals separate the porous sandstone packages. Two major lithofacies are recognized in the basin: a coarse-grained, well-sorted quartzarenite with various current laminations and a fine-grained, more poorly sorted subarkose and arkose with abundant bioturbation and distinct vertical and horizontal burrows. Reservoir quality is influenced by original depositional and diagenetic fabrics, but there is inversion of permeability and porosity with respect to primary textures in the major lithofacies. The initially highly porous and permeable, well-sorted, coarser facies is now tightly cemented with syntaxial quartz cement, resulting in a low-permeability, poor quality reservoir. The more poorly sorted, finer facies with initially lower permeabilities did not receive significant fluid flux until it passed below the zone of quartz cementation. This facies was cemented with carbonate which has subsequently dissolved to form a major secondary porosity reservoir.

  14. Sparta sandstones: future exploration potential in south-central Louisiana

    SciTech Connect

    Lemoine, R.C.; Moslow, T.F.; Sassen, R.; Ferrell, R.E.

    1989-03-01

    The middle Eocene Sparta Formation is an important exploration objective within the prolific Eocene-Oligocene trend of south-central Louisiana. Cumulative production from 20 multiple-reservoir fields in the trend exceeds 269 million bbl of crude, 50 million bbl of condensate, and 1.5 billion ft/sup 3/ of gas. Additional reservoirs include the lower Eocene Wilcox, upper Eocene Cockfield, and Oligocene Frio Formations. This trend, coincident with the location of the Lower Cretaceous carbonate shelf edge, represents a series of unstable progradational clastic shelf margins. Principal structural traps are rollover anticlines, associated with down-to-the-basin growth faults, and salt domes. Recent Sparta production is associated with progradational barrier island complexes. Storm washover fan sandstones (22% porosity, 324 md permeability), tidal-inlet channel sandstones (20% porosity, 140 md permeability), and upper shoreface sandstones (19% porosity, 113 md permeability) represent the optimum-quality reservoir facies. Organic-rich basinal shales are source rocks for crude oil downdip from production where they are thermally mature. Lateral migration best explains emplacement of hydrocarbons in reservoirs.

  15. Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

    USGS Publications Warehouse

    Castle, J.W.; Byrnes, A.P.

    2005-01-01

    Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 1-6 m (3-20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low S iw (<20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4-12%), lower permeability (0.0007-4 md), thicker transition zones (6-180 m [20-600 ft]), and higher S iw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average < 6%), low permeability (average < 0.02 md), and small pore throats result in large transition zones (30-200 m; 100-650 ft) and high water saturations. The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

  16. Sedimentology of an intra-montane rift-controlled fluvial dominated succession: The Upper Triassic Oukaimeden Sandstone Formation, Central High Atlas, Morocco

    NASA Astrophysics Data System (ADS)

    Fabuel-Perez, I.; Redfern, J.; Hodgetts, D.

    2009-06-01

    Triassic successions in the High Atlas of Marrakech (Morocco) provide excellent outcrop analogues for continental fluvial systems within an intra-montane rift basin and allow the study of facies distribution and controls on deposition. This paper focuses on the analysis of the Oukaimeden Sandstone Formation (F5), a fluvial dominated formation deposited in an active rift setting. Combination of traditional sedimentological field analysis with modern digital data capture techniques (e.g. spectral gamma-ray, LIDAR terrestrial scanner imaging) allows a detailed description and interpretation of the facies. The Oukaimeden Sandstone Formation is composed of channel sandstone bodies alternating with lenticular shaped fluvial bar sandstones and overbank mudstone deposits. Alternating with the fluvial facies, aeolian sandstones and alluvial fan deposits are also observed. Changes in architectural style are used to subdivide the formation into three members. The lower member (Lower Oukaimeden ) was deposited by an ephemeral braided system. The middle member (Middle Oukaimeden) records a change to perennial braided fluvial conditions in response to tectonics combined with a change in climate towards more humid conditions. The upper member (Upper Oukaimeden) is characterized by the return to ephemeral conditions, which combined with the occurrence of aeolian dunes, is interpreted to record increased aridity. The upper part of the member exhibits tidal influence, related to the first marine incursion into the basin. The Oukaimeden Sandstone Formation provide a well documented outcrop example of deposition within an intra-montane setting influenced by a combination of tectonic and climatic controls.

  17. Deep-water facies and petrography of the Galoc clastic unit, offshore Palawan, Philippines (south China Sea)

    SciTech Connect

    Link, M.H.; Helmold, K.P.

    1988-02-01

    The lower Miocene Galoc clastic unit, offshore Palawan, Philippines, is about 500-600 ft thick. The unit overlies the Galoc Limestone and is overlain by the Pelitic Pagasa Formation. The Galoc clastic unit consists of alternating quartzose sandstone, mudstone, and resedimented carbonate deposited at bathyal depths, mainly as turbidites. The deep-water deposits are confined to the axis of a northeast-trending trough in which slope, submarine channel, interchannel, depositional lobe, slump, and basinal facies are recognized. Eroded shallow-marine carbonate lithoclasts are commonly incorporated within the siliciclastic turbidites. The main reservoir sandstones occur in submarine channels and depositional lobes. The sandstones are texturally submature, very fine to medium-grained feldspathic litharenites and subarkoses. The sandstones have detrital modes of Q78:F11:L11 and Qm51:F11:Lt38, with partial modes of the monocrystalline components of Qm82:P13:K5. Lithic fragments include chert, shale, schist, volcanic rock fragments, and minor plutonic rock fragments. Porosity in the better reservoir sandstones ranges from 11 to 25%, and calcite is the dominant cement. Dissolution textures and inhomogeneity of calcite distribution suggest that at least half of the porosity in the sandstones has formed through the leaching of calcite cement and labile framework grains. A source terrain of quartzo-feldspathic sediments and metasediments, chert, volcanics, and acid-intermediate plutonic rocks is visualized.

  18. Log interpretation of shaly sandstones

    SciTech Connect

    Baker, J.F.

    1988-01-01

    The determination of water saturation from electrical resistivity measurements to evaluate the potential of reservoirs is a fundamental tool of the oil industry. Shaly sandstones are difficult to evaluate because clays are conductive and they lower the resistivity of the rock. A review of shaly-sandstone research concerning ''volume-of-shale'' equations reveals three theoretical categories: (1) laminated clay equations, (2) dispersed clay equations, and (3) equations that assume that the effect of the clays on the conductivity measurement is directly related to water saturation. A new model for predicting the relative amounts of laminated and dispersed shales and accounting for their effects according to their abundance can be used for any sandstone, clean or shaly. Equations representing each of the three theoretical categories and the new equation were tested on cored Wilcox sandstones from two wells. Cores were analyzed to determine the volume and distribution of clays and to correlate porosity with the well logs.

  19. Clay mineral diagenesis in Westwater Canyon sandstone member of Morrison Formation, San Juan basin, New Mexico

    SciTech Connect

    Crossey, L.J. )

    1989-09-01

    The Westwater Canyon Sandstone Member and the Brushy Basin and Recapture Shale Members of the Morrison Formation are examined from core located on the southern flank of the San Juan basin, northwestern New Mexico. Clay mineralogy of fine-grained lithologies of the Westwater Canyon Sandstone Member is contrasted with that of coarse-grained lithologies. Two distinct mixed-layer clay populations are present: a high expandable mixed-layer illite/smectite associated with coarse-grained lithologies. Two distinct mixed-layer clay populations are present: a highly expandable mixed-layer illite/smectite associated with coarse-grained units (in addition to chlorite and kaolinite), and an illitic mixed-layer illite/smectite (in some cases ordered and accompanied by traces of chlorite) in the fine-grained units. The expandable component of the mixed-layer clay does not exhibit a trend with depth but is lithology dependent. Coarse-grained samples from the Westwater Canyon Sandstone Member contain numerous mudstone intraclasts. The clay mineralogy of selected clasts has been examined. These lithologic characteristics must be taken into account in interpreting clay mineral diagenesis within the Morrison Formation. Framework grain alternation within the Westwater Canyon Sandstone Member has been linked to lacustrine facies in the overlying Brushy Basin Shale Member. Authigenic clay minerals within the Westwater Canyon Sandstone Member may provide a record of downward-percolating lake fluids. Early diagenetic effects must be recognized in order to interpret the complete diagenetic history of the Westwater Canyon Sandstone Member.

  20. Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)

    NASA Astrophysics Data System (ADS)

    Wolela, A.

    2014-11-01

    Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

  1. Quartz cementation mechanisms between adjacent sandstone and shale in Middle Cambrian, West Lithuania

    NASA Astrophysics Data System (ADS)

    Zhou, Lingli; Friis, Henrik

    2013-04-01

    Quartz is an important cementing material in siliciclastic sandstones that can reduce porosity and permeability severely. For efficiently predicting and extrapolating petrophysical properties such as porosity and permeability, the controls on the occurrence and the degree of quartz cementation need to be better understood. Because it is generally difficult to identify specific sources for quartz cement, many models attempting to explain quartz cementation conclude that external sources of silica are needed to explain the observed quantity of quartz cement, such as the mass transfer between sandstone and shale. Cambrian sandstones in Lithuania have abundant quartz cement which has significant effect on reservoir properties. The detrital quartz grains have been dissolved extensively along the shale-quartz contacts zones, making it a natural laboratory to study the influence of mass transfer between sandstone and shale to quartz cementation on petrophysical properties and reservoir quality. Our Cambrian shale samples in west Lithuania are mainly silty shale or siltstone (sample locations vary from 330 to 2090 m of burial depth). They are composed of quartz, clay and traces of feldspars, sericite, calcite, and pyrite. The clay minerals are mainly illite, with variable content of kaolinite and traces of chlorite. In the sandstone lamina, authigenic illite occurs as pore-filling cement which was composed of fibrous illite; pore-filling kaolinite is generally well crystallized and occurs as hexagonal plates arranged in booklets; quartz overgrowth are obvious in these sandstone laminas, especially in the contact zones between sandstone and shale. Dolomite and pyrite cementation are also present in some sandstone laminas but with few quartz overgrowth. Depositional facies and architecture played an important role in the precipitation of silica. Three different possible sources are distinguished for the quartz overgrowths in the intercalated sandstones: 1) Pressure

  2. Hydropressure tongues within regionally geopressured lower Tuscaloosa sandstone, Tuscaloosa trend, Louisiana

    SciTech Connect

    McCulloh, R.P.; Purcell, M.D.

    1983-01-01

    A regional study of the Tuscaloosa Formation in Louisiana, undertaken to assess geopressured-geothermal potential, revealed lobate, downdip extensions of the hydropressured zone in lower Tuscaloosa massive sandstone facies below the regional top of geopressure. Normal pressure zones within geopressured section were identified by drilling mud weights less than 13 pounds per gallon on electric logs of massive lower Tuscaloosa sandstone, and cross sections demonstrated updip continuity of these zones with the regional hydropressured zone. These hydropressure tongues are permitted by the anomalously high permeabilities reportd from the deep Tuscaloosa trend which have been attributed to both primary and secondary porosity. The hydropressure tongues correspond with lobes of thick net sandstone, principally in Pointe Coupee, East Feliciana, East Baton Rouge, and Livingston Parishes in the central Tuscaloosa trend. Limited control suggests at least one hydropressure tongue in the Chandeleur Sound area to the east.

  3. Distribution, chemistry, isotopic composition and origin of diagenetic carbonates: Magnus Sandstone, North Sea

    SciTech Connect

    Macaulay, C.I.; Haszeldine, R.S. ); Fallick, A.E. )

    1993-01-01

    Diagenetic ferroan carbonates grew in the Upper Jurassic reservoir sandstones of the Magnus oilfield in porewaters which differed in composition across the field. These porewaters remained compositionally different and stratified for at least 35 M.y. Variations in carbonate chemistry across the field are attributable to these porewater variations, which resulted from displacement of marine depositional water from the crest of the field by meteoric water during late Cimmerian subaerial exposure. Original depositional facies and detrital mineralogy strongly influenced diagenetic carbonate distribution. The objective of this paper is twofold: (1) to describe the occurrence of burial diagenetic magnesian siderite and ankerite from the Magnus Sandstone, and (2) to show that variations in the elemental and isotopic geochemistry of siderite and ankerite relate to long-lived variations in the composition of the porewaters in the sandstone during diagenesis.

  4. Facies and petrophysical modelling of a thick lower cretaceous tsunami deposit in E Spain: Up-scaling from sample to outcrop scales

    NASA Astrophysics Data System (ADS)

    Veloso, Fernanda M. L.; Liesa, Carlos L.; Soria, Ana R.; Meléndez, Nieves; Frykman, Peter

    2016-08-01

    The tsunami deposit (up to 3 m thick) of the Cretaceous Camarillas Formation in the Galve sub-basin (eastern Spain) is characterized by a large lateral extent (35 km2) and facies uniformity, consisting in fine to coarse subarkosic-arkosic sandstones. At the scale of outcrop observation, different lithofacies were distinguished and related to sedimentation processes. Sand facies distribution conditioned the facies heterogeneity at both mesoscopic or outcrop scales (10- 1-101 m scale) and sample scale (10- 3-10- 2 m). The sample features were up-scaled to that of a facies model using probability functions and variograms as well as to outcrop-scale data (geometry and size) of facies distribution, and it showed a good correlation with the facies distribution at the outcrop. Porosity is strongly correlated to permeability and the pairs of porosity and permeability values fall into the global hydraulic element (GHEs) 5, so that they can be up-scaled into reservoir models in terms of hydraulic properties. From data analysis, no apparent link between sand sorting and porosity and permeability values was observed. The petrophysical models, which were independent of facies models, were up-scaled taking into account the porosity and permeability values from sample data and the statistical analysis of their distribution along the outcrop. The permeability model was carried out as a function of porosity by applying a linear relation, which simplified the modelling process and discarded permeability uncertainties linked to facies distribution in the deposit. In spite of different source data, the petrophysical models show a distribution of lower and higher values that resembles the facies model. Consequently, our modelling results clearly suggest the link of facies type and their grain size distributions with the petrophysical properties into the deposit. Consistency between facies and petrophysical models and outcrop-scale observations make it possible to extrapolate to other

  5. Cyclic sedimentation, synsedimentary volcanism, microfabrics, and fracture intensity in the Austin Chalk, Texas

    SciTech Connect

    Hovorka, S.D. )

    1992-01-01

    Pelagic depositional environments of the Austin Chalk (Coniacian-Santonian) were influenced by sea-level variation, planktonic productivity, and allochthonous detrital input. Subtle differences in chalk facies influence fracture intensity, therefore imposing stratigraphic variability on hydrologic properties of the Austin Chalk. Variations in fracture intensity may affect ground-water flow through the Superconducting Super Collider (SSC) site south of Dallas in the same way that they influence hydrocarbon production in South Texas. The lower Austin Chalk was deposited during transgression. Glauconitic sandstone is overlain by cyclic chalk containing chalk-filled channels. Meter-thick chalk/marl cycles have frequencies in the Milankovitch spectrum. Marl accumulated during episodes of decreased planktonic productivity. Maximum flooding is indicated by organic-rich marls in the upper part of the Lower Austin Chalk. Shallowing during deposition of the middle and upper Austin Chalk is indicated by increasing abundance of winnowed lag deposits and firm grounds, resulting in increased faunal diversity. Authigenic clay, a product of alteration of volcanic ash codeposited with the chalk and marl, increases ductility in the middle Austin Chalk. The stratigraphic distribution of authigenic clay corresponds to disseminated biotite, quartz, and feldspar phenocrysts in most samples of the middle Austing Chalk. Authigenic clay decreases porosity, influences porosity-permeability relationships, and provides a regionally traceable low SP log response that correlates with low fracture intensity.

  6. ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

    SciTech Connect

    Jennie Ridgley

    2000-05-21

    A goal of the Mesaverde project was to better define the depositional system of the Mesaverde in hopes that it would provide insight to new or by-passed targets for oil exploration. The new, detailed studies of the Mesaverde give us a better understanding of the lateral variability in depositional environments and facies. Recognition of this lateral variability and establishment of the criteria for separating deltaic, strandplain-barrier, and estuarine deposits from each other permit development of better hydrocarbon exploration models, because the sandstone geometry differs in each depositional system. Although these insights will provide better exploration models for gas exploration, it does not appear that they will be instrumental in finding more oil. Oil in the Mesaverde Group is produced from isolated fields on the Chaco slope; only a few wells define each field. Production is from sandstone beds in the upper part of the Point Lookout Sandstone or from individual fluvial channel sandstones in the Menefee. Stratigraphic traps rather than structural traps are more important. Source of the oil in the Menefee and Point Lookout may be from interbedded organic-rich mudstones or coals rather than from the Lewis Shale. The Lewis Shale appears to contain more type III organic matter and, hence, should produce mainly gas. Outcrop studies have not documented oil staining that might point to past oil migration through the sandstones of the Mesaverde. The lack of oil production may be related to the following: (1) lack of abundant organic matter of the type I or II variety in the Lewis Shale needed to produce oil, (2) ineffective migration pathways due to discontinuities in sandstone reservoir geometries, (3) cementation or early formation of gas prior to oil generation that reduced effective permeabilities and served as barriers to updip migration of oil, or (4) erosion of oilbearing reservoirs from the southern part of the basin. Any new production should mimic that of

  7. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-01-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining the paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet.

  8. Palynology and Stratigraphy of the Nubian Sandstone in Libya and Comparison with Egypt

    NASA Astrophysics Data System (ADS)

    Tekbali, Ali; Hlal, Osama

    2013-04-01

    The so-called "Nubian Sandstone" outcrops along a wide area from Algeria to the Red Sea, forming two regressive phases. The lower phase is represented in Egypt by the Basal Clastic Unit, the Desert Rose Unit, the Abu Ballas Formation and the Matruh Shale. In Libya it is represented by the Mesak Sandstone, Sarir Sandstone, Cabao Sandstone and Kiklah Formation. In both countries, these successions are covered by a carbonate sequence, resulting from the Tethyan transgression during the Cenomanian. In Egypt however, the upper regressive phase is represented by the Taref Sandstone which was deposited during a brief period of active progradation, following the Tethyan incursion. This is not observed in Libya. Comparison of palynological studies in Libya with those documented by several authors in Egypt reveals that the "Nubian" facies in Libya were deposited before equivalent facies in Egypt. The Basal Clastic Unit, dated as Hautrauvian-Barremian, may be equivalent, at least to a part of the Neocomian Cabao Sandstone in NW Libya. Jarmah Member of the Mesak Formation in Libya was dated as Berriasian on the basis of Pilosisporites and Trilobosporites. This makes it older than any "Nubian" unit in Egypt. The Matruh Shale was assigned to the Aptian on the basis of Tricolpites, and the Abu Balls Formation 34 as Aptian-Albian on the basis of Tricolpites and Rousisporites radiatus. Whereas, there is no equivalent to the Aptian in NW Libya, the Aptian-Albian of Egypt is similar to Zone 1 of the Kiklah Formation and As Sarir Sandstone, which were dated as early Albian on the basis of Afropollis spp., and Perotriletes pannuceus, an Albian element not recorded in Egypt. The Plant Beds in southwestern Egypt were dated as Cenomanian on the basis of advanced angiosperm pollen. In Libya, equivalent bodies were considered Vraconian, representing the uppermost Albian, because it lacks Cenomanian pollen (e.g. Tricolpites mutabilis). Comparison of local sea-level changes with global sea

  9. Reservoir Characterization and Tectonic Settings of Ahwaz Sandstone Member of the Asmari Formation in the Zagros Mountain, SW of Iran

    NASA Astrophysics Data System (ADS)

    Adabi, M. H.; Sadeghi, A. D.; Hosseini, M.; Moalemi, A.; Lotfpour, A.; Khatibi Mehr, M.; Salehi, M.; Zohdi, A.; Jafarzadeh, M.

    2009-04-01

    The Ahwaz Sandstone Member of the Asmari Formation, the major oil reservoir in Zagros mountain, have been studied to understand the distribution, provenance, tectonic setting and reservoir characteristic of Ahwaz Sandstone intervals as an exploration target. This study was based on petrographic and geochemical analysis of 16 core samples from 13 oilfields in the Dezful Embayment zone, and 2 surface sections (Katula and Khami) in Izeh zone. Petrographic studies of 400 thin sections and geochemical analysis indicated that sandstones consist of quartzarenite (Khami surface section), sublitharenite ( Katula surface section) and subarkose (subsurface sections). The modal analysis of medium size and well sorted samples show a recycled orogen (Katula outcrop) and craton (Khami and subsurface sections) tectonic setting. The parent rocks for Ahwaz Sandstone, based on petrographic point counting suggest a low to medium grade metamorphic and plutonic source. Petrographic and grain size analysis indicate a shallow shoreline to barrier bar environments. Heavy minerals in sandstones have mostly plutonic source and abundance of stable heavy mineral, along with well rounded and high sphericity, support stable cratonic source for subsurface sections and Khami surface section. However, in Katula section, heavy minerals have metamorphic source. Facies map illustrated that siliciclastic sediments in Asmari Formation during Rupelian time comes from south-west and north west of the study area. During Chattian, sand distribution reaches to the maximum level and sediments arrived from south-west, north-west and also north-east of the study area. In Aquitanian, sandstones sourced from two areas of south-west and north-west. In Burdigalian stage, sandstone sourced only from south and south-west. These sandstones have limited distributions. Tectonic settings based on geochemical analysis, plotted on discrimination diagrams, suggest that passive continental margin. These sandstones were

  10. Tectonic and eustatic controls on facies distribution in the middle of upper Jurassic, Viking Graben, Norwegian North Sea

    SciTech Connect

    Sneider, J.S.; Vail, P.R. ); De Clarens, P. )

    1993-09-01

    The Middle of Upper Jurassic in the Viking Graben area was deposited during an overall transgression. From the lower Toarcian to the base of the cretaceous, there are seven 2nd-order (3-5 m.y.) transgressive-regressive (T/R) facies cycles that are related to regional tectonic events. These cycles dominate facies distribution, appear synchronous, and can be correlated throughout the study area. Local tectonics and sediment supply can modify these cycles. Local tectonics, sediment supply, and position in the T/R facies cycles control development of 3rd-order (0.5-3 m.y.) cycles. Where sediment supply is low, 3rd-order sequences are poorly developed. During a 2nd-order regression, shelfal areas and local highs are often eroded. Third-order sequences have well developed lowstands system-Y tracts (LST) and poorly developed transgressive systems tracts (TST). During 2nd-order transgressions, 3rd-order sequences have enhanced TST, starved HST, and poorly developed LST. Thick, stacked, shoreface sandstones may develop in the TST on terraces or on gently dipping slopes if sediment supply is high. The base of these sequences often shows an abrupt basinward shift in facies followed by backstepping facies. turbidites develop during 3rd-order lowstands when there is a steeply dipping slope and high sediment supply, but their distribution is more limited.

  11. Facies transition and depositional architecture of the Late Eocene tide-dominated delta in northern coast of Birket Qarun, Fayum, Egypt

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Zaki A.

    2016-07-01

    Late Eocene successions in the Fayum Depression display notable facies transition from open-marine to brackish-marine realms. Stratigraphic and sedimentologic characteristics of the depositional facies are integrated with ichnological data for the recognition of four facies associations (FA1 to FA4). The transition from open-marine sandstones (FA1) to the brackish-marine deposits (FA2) heralds a transgressive - regressive dislocation. The shallowing- and coarsening-upward progradation from the basal prodelta mudstone-dominated facies (FA2a) to deltafront heterolithics (FA2b) and sandstone facies (FA2c) are overlain by finning-upward delta plain deposits which are expressed by the delta plain mudstone (FA2d) and erosive-based distributary channel fills (FA4). Prodelta/deltfront deposits of FA2 are arranged in thinning- and coarsening-upward parasequences which are stacked in a shallowing-upward progressive cycle. Shallow-marine fossiliferous sandstones (FA3) mark the basal part of each parasequence. Stratigraphic and depositional architectures reflect a tide-dominated delta rather than an estuarine and incised valley (IV) model. This can be evinced by the progressive facies architecture, absence of basal regional incision or a subaerial unconformity and the stratigraphic position above a maximum flooding surface (MFS), in addition to the presence of multiple tidally-influenced distributary channels. Stratigraphic and depositional characteristics of the suggested model resemble those of modern tide-dominated deltaic systems. Accordingly, this model contributes to our understanding of the depositional models for analogous brackish-marine environments, particularly tide-dominated deltas in the rock record.

  12. Sequence stratigraphy and depositional facies of the Silurian-Devonian interval of the northern Permian basin

    SciTech Connect

    Canter, K.L.; Geesaman, R.C. ); Wheeler, D. )

    1992-04-01

    The Silurian and Devonian intervals of the northern Central Basin platform area of west Texas and southeastern New Mexico include the Fusselman, Wristen, and Thirtyone formations and the Woodford Shale. The carbonate-rich Fusselman, Wristen, and Thirtyone formations record a transition from ramp to platform deposition. Oolite grainstones of the lower Fusselman Formation were deposited in a ramp setting during an Upper Ordovician/Lower Silurian transgression. The overlying crinoid packstones and grainstones represent shoals that developed along a break in slope separating the evolving platform from a southward-dipping starved basin. By the close of Fusselman deposition, the platform was well developed, with shallow peridtidal mudstones and wackestones, and high-energy grainstones deposited as near-parallel facies tracts over the platform area. The platform system became fully developed during the deposition of the Wristen Formation. Porous dolomitic peridtidal and platform margin facies grade downdip into nonporous, limy and argillaceous open-shelf facies. Platform facies are typified by numerous shallowing-upward parasequences that terminated at subaerial exposure surfaces. The rocks of the Lower Devonian Thirtyone Formation were deposited as a wedge that onlaps the exposed Silurian platform margin. This formation contains a porous, chert-rich, lowstand deposit; a transgressive disconformity; and variably porous, grain-rich highstand deposits representing an overall sea level rise. A major unconformity marks the contact between the karsted upper surface of the Thirtyone Formation and the overlying organic-rich, anoxic Woodford Shale.

  13. Assessing Biogenecity of Stromatolites: Return to the Facies

    NASA Astrophysics Data System (ADS)

    Shapiro, R. S.; Jameson, S.; Rutter, A.; McCarthy, K.; Planavsky, N. J.; Severson, M.

    2013-12-01

    The discovery of richly microfossiliferous cherty stromatolites near Schreiber and Kakabeka Falls, Ontario, in the 1.9 Ga Gunflint Iron Formation, firmly established the field of pre-Cambrian paleontology. In the half-century since this discovery, paradigm shifts in the ecology of the microfossils as well as the utility of stromatolites as biological markers has caused a re-evaluation of our understanding of the pre-Cambrian fossil record. This research summarizes facies evaluation of the two stromatolite marker beds in the Gunflint-correlative Biwabik Iron Formation of Minnesota. The centimeter-scale microstratigraphy of cores drilled through the central and eastern Mesabi Iron Range was coupled with field descriptions of outcrops and mines in both the Biwabik and Gunflint iron formations. Eight lithologic facies associated with the stromatolites are identified: A) Pebble conglomerate clasts ranging in size of 0.5-3 cm, syneresis cracks, and septarian nodules with medium to coarse grain matrix; B) siltstone with subparallel sub-mm to 5 cm magnetitic and non-magnetic bands; C) stromatolitic boundstone comprising stratiform, pseudocolumnar, domal, undulatory, flat-laminated, dendritic, columnar, and mico-digitate forms and oncoids 0.5 to 2 cm diameter; D) grainstone with medium to coarse siliceous and carbonate ooids and peloids; E) massive green crystalline beds with bands of magnetite, quartz, calcite, disseminated pyrite and localized ankerite; F) autobreccicated fabric of 0.3 to 10 mm clasts; G) medium to coarse sandstone; H) quartzite. Correlation between 11 cores near Hoyt Lakes and 9 cores through the basal stromatolite layer at the MinnTac Mine near Virginia revealed that stromatolites formed both on conglomerate and medium quartz sandstone. Multiple forms of stromatolite may occur in a vertical succession (flat-laminated to undulatory to psuedocolumnar to columnar) or a core may be dominated by one type, typically columnar-stratiform. Where stromatolites do

  14. Texas Greenup

    NASA Technical Reports Server (NTRS)

    2007-01-01

    June 2007 was one of the wettest Junes on record for the state of Texas. Starting in late May, a string of low-pressure systems settled in over the U.S. Southern Plains and unleashed weeks of heavy to torrential rain. During the final week of June, much of Texas, Oklahoma, and Kansas received more than 330 percent of their average rainfall, said the National Climatic Data Center. The widespread heavy rain brought deadly floods to the entire region. On July 6, the Associated Press reported that every major river basin in Texas was at flood stage, an event that had not occurred since 1957. In addition to causing floods, the rains stimulated plant growth. The grassy, often arid, plains and plateaus of northern Mexico (bottom left), Texas (center), and New Mexico (top, left of center) burst to life with dense vegetation as this vegetation anomaly image shows. Regions where plants were growing more quickly or fuller than average are green, while areas where growth is below average are brown. Most of Texas is green, with a concentrated deep green, almost black, spot where vegetation growth was greatest. This area of western Texas is where the Pecos River flows out of New Mexico and heads southeast to the Rio Grande. In the darkest areas, vegetation was more than 100 percent above average. The brown spots in northeastern Texas and Oklahoma (top, right of center) may be areas where persistent clouds or water on the ground are hiding the plants from the satellite's view. Plants may also be growing less than average if swamped by too much rain. The image was made with data collected by the SPOT satellite between June 11 and June 20, 2007. NASA imagery created by Jesse Allen, Earth Observatory, using SPOT data provided courtesy of the USDA Foreign Agricultural Service and processed by Jennifer Small and Assaf Anyamba of the GIMMS Group at NASA GSFC.

  15. Multidisciplinary studies on ancient sandstone quarries of Western Sardinia (Italy).

    NASA Astrophysics Data System (ADS)

    Grillo, Silvana Maria; Del Vais, Carla; Naitza, Stefano

    2013-04-01

    , Oristano, Santa Giusta). They are prevailing fine-medium grained carbonate sandstones, and subordinate coarse sandstones and micro-conglomerates, variably cemented. In the studied areas, stratigraphic sequences grade from coarser facies of marine environment to fine-grained aeolian deposits, marked by cross-stratification. The Quaternary sedimentary sequence rests on Miocene limestones and clays, and on Plio-Pleistocene basalts. On optical microscopy, sandstones show grain-supported texture, with abundant carbonate bioclasts, intraclasts and algal nodules, with quartz, feldspars and fragments of granitoids, quartzites, volcanics. Grainsize in sandstone sequences progressively decreases towards the top, corresponding to an increase of fine bioclastic components. Terrigenous components change from the northernmost outcrops (Is Arutas quarries), where clasts of granitoid origin are dominant, to the southern outcrops (San Giovanni di Sinis quarries), which show a more marked compositional heterogeneity, with frequent volcanic feldspars and lithoclasts. The calcitic cement also shows distinct variations, both along the stratigraphic sequence and at areal scale, between the sparitic type and the micro/cryptocrystalline type. First evidences on samples from Tharros city walls indicate that sandstone blocks may come, almost in part, from the quarries of San Giovanni di Sinis that, consequently, could have started to work during the Punic age. Other evidences in the area, however, indicate that quarrying activities in Sinis continued well over the Ancient times, presumably including all the Middle Ages.

  16. Mid-Eocene alluvial-lacustrine succession at Gebel El-Goza El-Hamra (Shabrawet area, NE Eastern Desert, Egypt): Facies analysis, sequence stratigraphy and paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Wanas, H. A.; Sallam, E.; Zobaa, M. K.; Li, X.

    2015-11-01

    This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet Area, NE Eastern Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and shallow lacustrine systems. The floodplain-dominated alluvial facies (45 m thick) is composed mainly of carbonate nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated, planner cross-bedded, fine- to medium-grained sandstone bodies interlayered within mudstone reflect sheet flood deposits. The mudrocks associated with paleosols represent distal floodplain deposits. The shallow lacustrine facies (15 m thick) is made up of an alternation of marlstone, micritic limestone, dolostone and mudrock beds with charophytes and small gastropods. Both the alluvial and lacustrine facies show evidence of macro-and micro-pedogenic features. Pollen assemblages, stable δ18O and δ13C isotopes, and paleopedogenic features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian. The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Low- and High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of the alluvial facies reflect a LAST. Mudrock and silty claystone facies (distal floodplain deposits) of the upper part of alluvial facies and its overlying lacustrine facies correspond to a HAST. The LAST, HAST and SB were formed during different accommodation-to-sediment supply (A

  17. Factors controlling reservoir quality in tertiary sandstones and their significance to geopressured geothermal production

    SciTech Connect

    Loucks, R.G.; Richmann, D.L.; Milliken, K.L.

    1981-01-01

    Variable intensity of diagenesis is the factor primarily responsible for contrasting regional reservoir quality of Tertiary sandstones from the upper and lower Texas coast. Detailed comparison of Frio sandstone from the Chocolate Bayou/Danbury Dome area, Brazoria County, and Vicksburg sandstones from the McAllen Ranch Field area, Hidalgo County, reveals that extent of diagenetic modification is most strongly influenced by (1) detrital mineralogy and (2) regional geothermal gradients. The regional reservoir quality of Frio sandstones from Brazoria County is far better than that characterizing Vicksburg sandstones from Hidalgo County, especially at depths suitable for geopressured geothermal energy production. However, in predicting reservoir quality on a site-specific basis, locally variable factors such as relative proportions for porosity types, pore geometry as related to permeability, and local depositional environment must also be considered. Even in an area of regionally favorable reservoir quality, such local factors can significantly affect reservoir quality and, hence, the geothermal production potential of a specific sandstone unit.

  18. Tide-influenced sedimentary environments and facies

    SciTech Connect

    De Boer, P.L.; Van Gelder, A.; Nio, S.D.

    1988-01-01

    This volume contains examples of recent as well as fossil tide-influenced sedimentary facies. Studies of recent tidal processes and sediments provide an insight into the way in which tidal facies and sequences develop, and into the processes which are active. The studies performed on fossil rocks give information on one-to-one scale model experiments that have been executed by nature both relatively recently and in the distant past. In this work, the parallel presentation of papers on recent and fossil examples of tide-influenced sedimentary facies and environments follows the philosophy of comparative sedimentology, aiming at an understanding of both the past and the present, with the aim also, of forecasting future developments.

  19. Facies distribution, depositional environment, and petrophysical features of the Sharawra Formation, Old Qusaiba Village, Central Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Abbas, Muhammad Asif; Kaminski, Michael; Umran Dogan, A.

    2016-04-01

    moderate-scale transgressive episodes, while the thin shale interbeds in the middle and upper part of the Sharawra Formation represent small-scale transgressions. Overall, the Sharawra Formation contains a series of repetitive transgressive and regressive events and has been interpreted as a pro-deltaic deposit in previous studies. In the present study, the lowermost sandstone thickly bedded facies lie within the transition zone environment. The siltstone facies and the horizontally stratified facies show a middle shore face environment. The middle shore face environment is present locally. The bioturbation in the uppermost facies is indicative of the upper shore face environment. The porosity values do not vary much, as the average porosity for the sandstone facies is about 15%, for the siltstones it ranges about 7%. The permeability is variable throughout the formation, the values range from 50 to 300 md. Although sandstone has a good porosity and permeability, the siltstone facies exhibit poor petrophysical characteristics. In terms of reservoir characterization, the mineralogical mature, moderately well sorted top most sandstone facies, with appreciable porosity and permeability can be considered as a potential reservoir rock. This study has provided a base for future quantitative studies in this important formation in the area.

  20. Operation Sandstone: 1948. Technical report

    SciTech Connect

    Berkhouse, L.H.; Hallowell, J.H.; McMullan, F.W.; Davis, S.E.; Jones, C.B.

    1983-12-19

    SANDSTONE was a three-detonation atmospheric nuclear weapon test series conducted during the spring of 1948 at Enewetak Atoll in the Marshall Islands. Report emphasis is on the radiological safety of the personnel. Available records on personnel exposure are summarized.

  1. A New Classification of Sandstone.

    ERIC Educational Resources Information Center

    Brewer, Roger Clay; And Others

    1990-01-01

    Introduced is a sandstone classification scheme intended for use with thin-sections and hand specimens. Detailed is a step-by-step classification scheme. A graphic presentation of the scheme is presented. This method is compared with other existing schemes. (CW)

  2. A multistorey sandstone complex in the Himalayan Foreland Basin, NW Himalaya, India

    NASA Astrophysics Data System (ADS)

    Kumar, Rohtash; Sangode, Satish J.; Ghosh, Sumit K.

    2004-07-01

    Ten parallel stratigraphic sections (1500-1800 m thick) spread over an area of >400 km 2 in Dehra Dun sub-basin (DSB) of the Himalayan Foreland Belt (HFB) were studied to understand the anatomy of one of the largest (900-1200 m thick) fluviatile Multistorey Sandstone Complexes (MSC) of the world using fluvial geometry, compositional data and magnetic fabrics over a magnetostratigraphically controlled master section. The multistorey sandstone complex, between 10-5 Ma representing the Middle Siwalik sub-Group, comprises of grey, medium- to fine-grained lithic arenites to lithic greywacke and records tectonic and/or climatic episodes. Three main facies associations are recognised: sandstone-mudstone, sandstone, and conglomerate-sandstone that represent fluvial fan deposit. Palaeocurrent data show radial palaeoflow pattern with major palaeodrainage towards the southern quadrant. The magnetic fabric studies suggest three major tectonic pulses. The first pulse at ˜8.7 Ma resulted in the development of major depocenter for the MSC, the second pulse at ˜7.65 Ma enhanced the sedimentation and progradation, while the third pulse at ˜6.5 Ma records overlapping earlier fluvial fan by another coarse grained piedmont alluvial fan. Thrust movement in the northern fold belt, basement lineaments and rate of basin subsidence controlled the lateral and vertical facies distribution and palaeodrainage. The sedimentation pattern of the multistorey complex is characterised by mainly sheet flood deposits of laterally avulsing unconfined braided rivers and resembles to the modern megafan sedimentation in the Ganga Basin to the south.

  3. Sedimentary facies and environmental ichnology of a ?Permian playa-lake complex in western Argentina

    USGS Publications Warehouse

    Zhang, G.; Buatois, L.A.; Mangano, M.G.; Acenolaza, F.G.

    1998-01-01

    A moderately diverse arthropod icnofauna occurs in ?Permian ephemeral lacustrine deposits of the Paganzo Basin that crop out at Bordo Atravesado, Cuesta de Miranda, western Argentina. Sedimentary successions are interpreted as having accumulated in a playa-lake complex. Deposits include three sedimentary facies: (A) laminated siltstone and mudstone: (B) current-rippled cross-laminated very fine grained sandstone: and (C) climbing and wave-rippled cross-laminated fine-grained sandstone deposited by sheet floods under wave influence in the playa-lake complex. Analysis of facies sequences suggests that repeated vertical facies associations result from transgressive regressive episodes of variable time spans. The Bordo Atravesado ichnofauna includes Cruziana problematica, Diplocraterion isp., cf. Diplopadichnus biformis, Kouphichnium? isp., Merostomichnites aicunai, Mirandaichnium famatinense, Monomorphichnus lineatus, Palaeophyeus tubularis, Umfolozia sinuosa and Umfolozia ef. U. longula. The assemblage is largely dominated by arthropod trackways and represents an example of the Scoyenia ichnofacies. Trace fossils are mostly preserved as hypichnial ridges on the soles of facies C beds, being comparatively rare in facies A and B. Ichnofossil preservation was linked to rapid influx of sand via sheet floods entering into the lake. Four taphonomic variants (types 1-4) are recognized, each determined by substrate consistency and time averaging. Type 1 is recorded by the presence of low density assemblages consisting of poorly defined trackways, which suggests that arthropods crawled in soft, probably slightly subaqueous substrates. Type 2 is represented by low to moderate density suites that include sharply defined trackways commonly associated with mud cracks, suggesting that the tracemakers inhabited a firm, desiccated lacustrine substrate. Type 3 displays features of types 1 and 2 and represents palimpsestic bedding surfaces, resulting from the overprint of terrestrial

  4. Facies architecture in a fluvial-deltaic sequence, upper Crooked Fork Group (Pennsylvanian), Tennessee and Kentucky

    SciTech Connect

    Barden, M.J.

    1989-03-01

    The upper Crooked Fork Group on the Cumberland plateau in northeastern Tennessee and southeastern Kentucky includes the Wartburg Sandstone (Corbin of Kentucky) and surrounding fine-grained strata of the Breathitt Formation below the Poplar Creek Coal. Detailed study of outcrops employs lateral profiles and architectural element analysis. Examination of bounding surfaces within and between elements indicates a sixfold hierarchy based on areal extent and geometry. The Wartburg Sandstone consists largely of three-dimensional macroform bar complexes. Foreset macroform elements predominate, with minor lateral accretion elements present and no apparent internal cyclicity. The channelized base of the Wartburg, predominance of large-scale planar and trough cross-stratification, low paleocurrent variance, and presence of soft-sediment deformation elements and massive sandstone elements with large mudstone intraclasts suggest a low-sinuosity fluvial setting. Strata overlying the Wartburg display fine-grained lateral accretion elements and associated overbank-fines. This suggests an upward change in fluvial style in the upper Crooked Fork Group from a predominantly coarse-grained low-sinuosity setting to a fine-grained high-sinuosity setting. The abundance of downstream and lateral accretion elements, plant debris, rooting, and thin discontinuous coals; paucity of burrows and bioturbation; and presence of thin marine horizons combined with the facies architecture suggest a channelized depositional setting with some marine influence, indicative of fluvial or fluvial-dominated deltaic deposits.

  5. Facies composition calculated from the sonic, neutron, and density log suite, upper part of the Minnelusa Formation, Powder River basin, Wyoming

    USGS Publications Warehouse

    Schmoker, J.W.; Schenk, C.J.

    1988-01-01

    Sandstones and dolomites of the Permian upper part of the Minnelusa Formation are treated here as four-component systems consisting of fluid-filled pore space, quartz, dolomite, and anhydrite. Response equations of sonic, neutron, and density logs form a system of four simultaneous equations. With four equations and four unknowns, the composition of upper Minnelusa facies is defined by the three-log suite and can be calculated by solving a 4 ?? 4 matrix. Such calculations of facies composition help in establishing subsurface correlations and yield information on the diagenesis and physical character of upper Minnelusa sandstones and dolomites. Applications of composition calculations are illustrated by examples drawn from the area of the West Mellott field (T52N, R68W), where the upper Minnelusa is at depths of about 7000 ft (2100m). -from Authors

  6. Reservoir heterogeneity in the middle Frio Formation: Case studies in Stratton and Agua Dulce fields, Nueces County, Texas

    SciTech Connect

    Kerr, D.R. )

    1990-09-01

    Selected middle Frio (Oligocene) reservoirs of Stratton field and the contiguous Agua Dulce field are being studied as part of a Gas Research Institute/Department of Energy/State of Texas cosponsored program designed to improve reserve growth in mature gas fields. Over the past four decades, Stratton has produced 2.0 tcf of gas from 113 middle Frio reservoirs, and Agua Dulce has produced 1.6 tcf from 116 reservoirs. Recent drilling and workover activities, however, suggest the presence of additional untapped or bypassed middle Frio reservoirs. Four reservoirs, the E18/6,020-ft, E21/6,050-ft, E31/6,100-ft, and E41/Bertram, were evaluated over a 13,000-acre tract that includes areas adjacent to both fields. The middle Frio is composed of sand-rich channel-fill and splay deposits interstratified with floodplain mudstones, all forming part of the Gueydan fluvial system. Channel-fill deposits are 30 ({plus minus}15) ft thick and 2,500 ({plus minus}500) ft wide. Splay deposits are up to 30 ft thick proximal to channels and extend as much as 2 mi from channels. Channel-fill and associated splay sandstones are reservoir facies (porosity 20%; permeability = 10s to 100s md); floodplain mudstones and levee sandy mudstones are barriers to flow facies separating individual reservoirs vertically and laterally. The E41/Bertram reservoir is an example of a laterally stacked channel system deposited during relatively slow aggradation. This reservoir includes sand-on-sand contacts and is composed of mostly leaky compartments. The E 18/6,020-ft, E21/6,050-ft, and E31/6,100ft reservoirs are examples of vertically stacked channel systems reflecting higher rates of aggradation. Vertically stacked architectures are more favorable for isolated compartments and therefore are better candidates for infield reserve growth.

  7. Mississippian facies relationships, eastern Anadarko basin, Oklahoma

    SciTech Connect

    Peace, H.W. ); Forgotson, J.M. )

    1991-08-01

    Mississippian strata in the eastern Anadarko basin record a gradual deepening of the basin. Late and post-Mississippian tectonism (Wichita and Arbuckle orogenies) fragmented the single large basin into the series of paired basins and uplifts recognized in the southern half of Oklahoma today. Lower Mississippian isopach and facies trends (Sycamore and Caney Formations) indicate that basinal strike in the study area (southeastern Anadarko basin) was predominantly east-west. Depositional environment interpretations made for Lower Mississippian strata suggest that the basin was partially sediment starved and exhibited a low shelf-to-basin gradient. Upper Mississippian isopach and facies trends suggest that basinal strike within the study area shifted from dominantly east-west to dominantly northwest-southeast due to Late Mississippian and Early Pennsylvanian uplift along the Nemaha ridge. Within the study area, the Chester Formation, composed of gray to dove-gray shales with interbedded limestones deposited on a carbonate shelf, thins depositionally into the basin and is thinnest at its facies boundary with the Springer Group and the upper portion of the Caney Formation. As basin subsidence rates accelerated, the southern edge of the Chester carbonate shelf was progressively drowned, causing a backstepping of the Chester Formation calcareous shale and carbonate facies. Springer Group sands and black shales transgressed northward over the drowned Chester Formation shelf.

  8. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  9. Deltaic deposits of the Upper Cretaceous Dad Sandstone Member of the Lewis Shale, south-central Wyoming

    SciTech Connect

    Perman, R.C.

    1987-01-01

    The Dad Sandstone Member is a prograding unit of sandstone and minor mudstone that separates upper and lower shale members of the Lewis Shale. Outcrops of this Maestrichtian-age unit have been examined in south-central Wyoming along the eastern margin of the Great Divide basin north of Rawlins, and in the Hanna basin to the east. These outcrops form two groups with very different characteristics, including thickness of sandstone and interbedded mudstone units, sedimentary structures, and fossils. In the western part of the area studied, the Dad Sandstone is interpreted to represent progradation in the lower delta-front region of the Sheridan delta that existed to the northwest. In the eastern portion of the study area the Dad Sandstone probably represents upper shoreface facies of interdistributary barrier bars. These deposits may be related to either the Sheridan delta to the north, or a north-trending uplift to the south. The Dad Sandstone in the eastern part of the study area is probably slightly younger than in the western part of the study area.

  10. Architecture and facies pattern of a sublacustrine fan, Jharia Basin, India

    NASA Astrophysics Data System (ADS)

    Dasgupta, Prabir

    2002-05-01

    . Isolated channel-fills show lateral uniformity in facies pattern while confluent channels produced laterally variable composite facies association with a distinct zone of interference. Lensoid mass flow deposits with distinct upslope slide scarps represent the event of slope failure as a result of cannibalisation during low water stand. These slide lenses are present in different levels in association with either the sandstone aprons or the channel-fills showing high degree of randomness in their order of appearance. The consistently developed round-bottomed geometry of the channels and the nature of channel-fills strongly advocate in favour of their subaqueous origin. Absence of any subaerial character within the sandstone aprons also suggests their emplacement under subaqueous condition. The thick stacks of channel-fill sandbodies were developed as a consequence of vertical channel aggradation under continued hangingwall subsidence, and the upward declining trend in vertical aggradation suggests gradual fall in the rate of this subsidence. Subsequently, the whole block subsided and went under deepwater condition due to lacustrine transgression and the fan was buried under deepwater carbonaceous shale.

  11. Depositional environments of Schuler Formation (Cotton Valley Sands), Upshur County, Texas

    SciTech Connect

    Kast, J.A.

    1983-03-01

    Exploration for tight gas (FERC Section 107) production from the Schuler Formation (Cotton Valley sands) has provided recent data for the recognition of the lower Schuler (Shongaloo member) shoreface facies and delineation of the upper Schuler (Dorcheat member) delta plain complex in Upshur County. Shoreface facies within the lower Schuler have a typical funnel-shaped log pattern (coarsening-upward clastic). In core, the corresponding coarsening-upward sequence grades from offshore to upper shoreface facies. Upper offshore sediments are dominated by a heavily bioturbated and intercalated sandstone/shale sequence with numerous trace fossils, escape traces, and shell debris. Associated facies overlying the upper shoreface are lagoonal. Subaerially exposed mottled red and green siltsone and red mudstone show evidence of root penetration and are interpreted as coastal plain to tidal flat. The marsh deposits (green siltstones and red mudstones) gradationally interbed with a subtidal lagoonal facies containing dark gray, fossiliferous, argillaceous, limestone containing oysters, echinoid fragments, and annelid worm tubes. In an effort to tie the limited core data (4 wells) to a countywide environmental interpretation, sand percent interval slice maps were constructed above and below the ubiquitous subtidal lagoonal marker. These maps and core data in the lower Schuler delineate a strike-oriented, linear clastic shoreline (ENEWSW). Within Upshur County, lower Schuler sediments were deposited as interdeltaic, shoreface facies. The upper member is characterized by a dip-oriented sandstone trend interpreted as an aggradational delta plain complex associated with the Lone Oak delta system.

  12. Recent Developments in Facies Models for Siliciclastic Sediments.

    ERIC Educational Resources Information Center

    Miall, Andrew D.

    1982-01-01

    Discusses theory of facies models (attempts to synthesize/generalize information about depositional environments), strengths/weaknesses of facies modelling, recent advances in facies models for siliciclastic sediments (focusing on fluvial, lacustrine, eolian and glacial environments, clastic shorelines and continental shelves, and clastic…

  13. Enigmatic eight-meter trace fossils in the Lower Pennsylvanian Lee sandstone, central Appalachian basin, Tennessee

    USGS Publications Warehouse

    Wnuk, C.; Maberry, J.O.

    1990-01-01

    Enigmatic tubular trace fossils up to eight meters long occur in the Lower Pennsylvanian Middlesboro Member of the Lee Formation. Two morphotypes occur: type 1 trace fossils are plain, smooth, vertical, nonbranching, parallel-walled, tubular structures, type 2 trace fossils branch, have walls with faint vertical striations, regularly or irregularly spaced nodes, and funnel-shaped terminations. Sandstone casts filling type 2 structures have helical spiral morphology, and, in rare individuals, faint meniscate fills have been observed. Both trace-fossil morphotypes have poorly cemented wall linings containing framboidal pyrite, amorphous carbon, quartz sand, and poorly preserved fecal material. The trace fossils occur in a massive, structureless, channel-form sandstone, originating at the contact between a channel lag and the overlying massive fill representing a barrier island transgressing an estuarine facies. Origin of these structures is uncertain. -from Authors

  14. Formation and origin of tuffaceous sandstones from IODP Expedition 322, Nankai Trough

    NASA Astrophysics Data System (ADS)

    Kutterolf, S.; Schindlbeck, J. C.; Freundt, A.; Scudder, R. P.; Pickering, K. T.; Labanieh, S.; Naruse, H.; Underwood, M.; Wu, H.

    2011-12-01

    During IODP Expedition 322 one major new discovery was an interval of tuffaceous and volcaniclastic sandstones, which has been defined as the middle Shikoku Basin facies. This lithologic Unit II is late Miocene (>7.07 to ~9.0 Ma) in age and can be divided into two subunits by the abundance of volcanic glass shards, mineral and/or lithic contents, and bulk-rock XRF data. The upper subunit IIA consists of moderately lithified and bioturbated silty claystone including three 1 to 10 meter thick interbeds of tuffaceous sandstones containing 35 to 60 vol% pyroclasts. The tuffaceous sandstone packages are build up by one to three density-graded units with lithic fragments and minerals enriched at the base and pumice clasts (remnants) accumulated at the top, interpreted as turbidity current deposits. Major and trace element glass-shard compositions in each sandstone package either have homogeneous composition or define a well-constrained compositional variation trend, implying that each package derived from a single pyroclastic deposit or a single eruptive event as opposed to gravity currents resulting from collapse of large, heterogeneous slope sections. Moreover, glass compositions show that the tuffaceous sandstones all came from a similar source region either at the Izu Bonin rear arc or the Japanese mainland. Magmatic compositions at both regions would be compatible with the moderate K2O concentrations (2 to 3.5 wt%), but high Ba/Zr, Zr/Nb and La/Sm ratios of the glass shards favors the latter one; the Izu Bonin arc can be excluded as a source due to generally lower potassium concentrations. The high incompatible trace element contents of the glasses suggest a source region where the mantle source of magmas lies below continental crust. Therefore, the Japanese mainland seems to be the most likely provenance for the tuffaceous sandstones found ~ 350 km away in the Shikoku Basin.

  15. Sedimentology, petrology, and gas potential of the Brallier Formation: upper Devonian turbidite facies of the Central and Southern Appalachians

    SciTech Connect

    Lundegard, P.D.; Samuels, N.D.; Pryor, W.A.

    1980-03-01

    The Upper Devonian Brallier Formation of the central and southern Appalachian basin is a regressive sequence of siltstone turbidites interbedded with mudstones, claystones, and shales. It reaches 1000 meters in thickness and overlies basinal mudrocks and underlies deltaic sandstones and mudrocks. Facies and paleocurrent analyses indicate differences between the depositional system of the Brallier Formation and those of modern submarine fans and ancient Alpine flysch-type sequences. The Brallier system is of finer grain size and lower flow intensity. In addition, the stratigraphic transition from turbidites to deltaic sediments is gradual and differs in its facies succession from the deposits of the proximal parts of modern submarine fans. Such features as massive and pebbly sandstones, conglomerates, debris flows, and massive slump structures are absent from this transition. Paleocurrents are uniformly to the west at right angles to basin isopach, which is atypical of ancient turbidite systems. This suggests that turbidity currents had multiple point sources. The petrography and paleocurrents of the Brallier Formation indicate an eastern source of sedimentary and low-grade metasedimentary rocks with modern relief and rainfall. The depositional system of the Brallier Formation is interpreted as a series of small ephemeral turbidite lobes of low flow intensity which coalesced in time to produce a laterally extensive wedge. The lobes were fed by deltas rather than submarine canyons or upper fan channel systems. This study shows that the present-day turbidite facies model, based mainly on modern submarine fans and ancient Alpine flysch-type sequences, does not adequately describe prodeltaic turbidite systems such as the Brallier Formation. Thickly bedded siltstone bundles are common features of the Brallier Formation and are probably its best gas reservoir facies, especially when fracture porosity is well developed.

  16. Facies in stratigraphy: from 'terrains' to 'terranes'.

    USGS Publications Warehouse

    Nelson, C.M.

    1985-01-01

    Concepts of lateral variation in sedimentary rocks and fossil assemblages developed in France from the 1760s; the definitive definition of facies was provided in 1838 by the Swiss geologist Amanz Gressly (1814-65) in his detailed field study of the eastern Jura. His maps and cross-sections of variations in Jurassic and Triassic rocks are illustrated. He believed that variations reflected environmental conditions, as in modern seas, and would eventually permit former depths to be reconstructed. Gressly studied at Strasbourg under Voltz and Thurmann: he collaborated with L.Agassiz, E.Desor and C.Vogt. His work influenced German and French geologists and provided a basis for interpretations of the Alps. But the facies concept was not deeply rooted in American geology until around 1884 (H.S.Williams) and in Britain and Russia until around 1900. I.S.Evans

  17. Architectural analysis of a Triassic fluvial system: The Sherwood Sandstone of the East Midlands Shelf, UK

    NASA Astrophysics Data System (ADS)

    Wakefield, Oliver J. W.; Hough, Edward; Peatfield, Alex W.

    2015-08-01

    The Sherwood Sandstone Group of the northeast UK (East Midlands Shelf) has hitherto never been studied in detail to ascertain its palaeoenvironment of deposition, largely because it is poorly exposed. As such, this paper aims to provide the first modern sedimentological interpretation of the Sherwood Sandstone in the east of England based on a field outcrop at the disused quarry at Styrrup. This is in stark contrast to the western parts of England where the Sherwood Sandstone is well exposed and offshore in the North Sea Basin where it is represented by a substantial library of core material where it is also relatively well understood. The outcrop at Styrrup Quarry allows contrasts to be made with the style and expression of the Sherwood Sandstone between eastern and western England. Specifically, this highlights differences around the variation in fluvial discharge (between lowstand and highstand) and the absence of aeolian facies types. It is interpreted that these differences relate to discharge variations between ephemeral and perennial systems with a perennial model proposed for Styrrup Quarry. This model draws upon inferences of additional water input from more local areas, likely topographic uplands of the London-Brabant and Pennine Highs which supplement the primary source of the Variscan Mountains in France with additional water and sediment.

  18. The Manciano Sandstone: a shoreface deposit of Miocene basins of the Northern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Martini, I. P.; Cascella, A.; Rau, A.

    1995-09-01

    Well exposed, diamond-line cut, quarry-exposures of the Manciano Sandstone allow a detailed analysis of sandy, fossiliferous, nearshore deposits of the shelf of the Northern Apennines. The Manciano Sandstone is characterized by medium to very coarse, washed, fairly well sorted, lithic sandstone, with thin interlayers of sandy conglomerates. It displays two principal, rhythmically alternating sandy facies: (a) slightly burrowed (mostly Macaronichnus, Ophiomorpha, Skolithos) units, trough cross-bedded, locally showing possible tidal bundles with few whole Scutella (echinoid) shells reworked on foresets, or occasional large-scale (approximately 2 m) planar cross-bedded, bar-accretion units; and (b) slightly finer, darker-coloured reddish-brown sandstone units, heavily bioturbated ( Cruziana-Skolithos) ichnofauna) representing slightly more sheltered settings. Large oysters are present in near-living position in a few thin layers and, more commonly, as reworked, comminuted fragments in sandy layers. Many calcareous pebbles and oyster fragments are bored. Other fossils consist of echinoids ( Scutella), some balanids and reworked foraminifera and bryozoa. The Manciano sands were deposited primarily in a wave-dominated shoreface, containing migrating bars/ridges and affected by wave-induced, possibly tidal-enhanced currents. This tidal influence confirms the opening of the Miocene Apenninic Sea to oceans, both the developing Atlantic Ocean to the west and, through a long, narrow seaway, the Asian portion of the Tethys Sea to the east.

  19. Mediterranean Miocene carbonates: facies models and diagenesis

    SciTech Connect

    Esteban, M.E.

    1987-11-01

    Miocene carbonates can bridge the gap between Holocene and older carbonate sequences, thus enhancing understanding of depositional and diagenetic patterns. Miocene carbonates can bridge this gap because of their similarity to Holocene counterparts and the ease of using these carbonates to reconstruct tectonic, paleogeographic, and paleoclimatic settings. In the Mediterranean, the Miocene provides a superb set of exposures and a wide variety of facies models in different geologic settings.

  20. Supercritical CO2 Migration under Cross-Bedded Structures: Outcrop Analog from the Jurassic Navajo Sandstone

    NASA Astrophysics Data System (ADS)

    Lee, S.; Allen, J.; Han, W.; Lu, C.; McPherson, B. J.

    2011-12-01

    Jurassic aeolian sandstones (e.g. Navajo and White Rim Sandstones) on the Colorado Plateau of Utah have been considered potential sinks for geologic CO2 sequestration due to their regional lateral continuity, thickness, high porosity and permeability, presence of seal strata and proximity to large point sources of anthropogenic CO2. However, aeolian deposits usually exhibit inherent internal complexities induced by migrating bedforms of different sizes and their resulting bounding surfaces. Therefore, CO2 plume migration in such complex media should be well defined and successively linked in models for better characterization of the plume behavior. Based on an outcrop analog of the upper Navajo Sandstone in the western flank of the San Rafael Swell, Utah, we identified five different bedform types with dune and interdune facies to represent the spatial continuity of lithofacies units. Using generated 3D geometrical facies patterns of cross-bedded structures in the Navajo Sandstone, we performed numerical simulations to understand the detailed behavior of CO2 plume migration under the different cross-bedded bedforms. Our numerical simulation results indicate that cross-bedded structures (bedform types) play an important role on governing the rate and directionality of CO2 migration, resulting in changes of imbibition processes of CO2. CO2 migration tends to follow wind ripple laminations and reactivation surfaces updip. Our results suggest that geologically-based upscaling of CO2 migration is crucial in cross-bedded formations as part of reservoir or basin scale models. Furthermore, comparative modeling studies between 3D models and 2D cross-sections extracted from 3D models showed the significant three-dimensional interplay in a cross-bedded structure and the need to correctly capture the geologic heterogeneity to predict realistic CO2 plume behavior. Our outcrop analog approach presented in this study also demonstrates an alternative method for assessing geologic

  1. A paleogeographic model for the sandstone members of the Imo Shale, south-eastern Nigeria

    NASA Astrophysics Data System (ADS)

    Ekwenye, O. C.; Nichols, G. J.; Collinson, M.; Nwajide, C. S.; Obi, G. C.

    2014-08-01

    A new interpretation of the Palaeocene to Eocene strata of SE Nigeria has been developed based on field facies analysis and borehole data from the area. The area is considered to have been a tidally-dominated shelf setting which underwent a series of changes in sea level during the deposition of the Imo Shale. An initial transgression led to the deposition of a widespread marine shale unit that is interpreted as an offshore succession. This was followed by an influx of sands that are texturally mature, coarse to fine-grained that show large-scale cross-stratification with dip angles of between 15° and 25°. These are interpreted as the deposits of large sandwaves on a tidally-dominated shelf. Transport direction determined by the dominant large scale cross beds indicate a north-westerly transport direction. The presence of illite and nontronite clay mineral types in the offshore shales typically suggest marine environment whereas the occurrence of kaolinite which indicates terrestrial influence. A shale bed above the sand wave unit is overlain by wave-ripple cross-laminated sandstone considered to have formed in an upper shoreface setting. An overlying fossiliferous shale with a restricted fauna and shell lag is interpreted as having been formed in a lagoon with restricted circulation. The progradational succession is capped by a return to deeper water facies comprising a mixed carbonate-siliciclastic succession. This includes mudstone with limestone layers, calcareous sandstone with fossiliferous marl beds, fossiliferous and bioturbated sandstone. These beds represent a relative sea level rise on the shelf, accompanied by a decrease in siliciclastic input. This data provides a new conceptual model for the paleogeographic evolution of the sandstone member of the Imo Shale.

  2. SEQUENCE STRATIGRAPHIC ANALYSIS AND FACIES ARCHITECTURE OF THE CRETACEOUS MANCOS SHALE ON AND NEAR THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO-THEIR RELATION TO SITES OF OIL ACCUMULATION

    SciTech Connect

    Jennie Ridgley

    2000-03-31

    Oil distribution in the lower part of the Mancos Shale seems to be mainly controlled by fractures and by sandier facies that are dolomite-cemented. Structure in the area of the Jicarilla Apache Indian Reservation consists of the broad northwest- to southeast-trending Chaco slope, the deep central basin, and the monocline that forms the eastern boundary of the San Juan Basin. Superimposed on the regional structure are broad low-amplitude folds. Fractures seem best developed in the areas of these folds. Using sequence stratigraphic principals, the lower part of the Mancos Shale has been subdivided into four main regressive and transgressive components. These include facies that are the basinal time equivalents to the Gallup Sandstone, an overlying interbedded sandstone and shale sequence time equivalent to the transgressive Mulatto Tongue of the Mancos Shale, the El Vado Sandstone Member which is time equivalent to part of the Dalton Sandstone, and an unnamed interbedded sandstone and shale succession time equivalent to the regressive Dalton Sandstone and transgressive Hosta Tongue of the Mesaverde Group. Facies time equivalent to the Gallup Sandstone underlie an unconformity of regional extent. These facies are gradually truncated from south to north across the Reservation. The best potential for additional oil resources in these facies is in the southern part of the Reservation where the top sandier part of these facies is preserved. The overlying unnamed wedge of transgressive rocks produces some oil but is underexplored, except for sandstones equivalent to the Tocito Sandstone. This wedge of rocks is divided into from two to five units. The highest sand content in this wedge occurs where each of the four subdivisions above the Tocito terminates to the south and is overstepped by the next youngest unit. These terminal areas should offer the best targets for future oil exploration. The El Vado Sandstone Member overlies the transgressive wedge. It produces most of

  3. Petrophysical characteristics and fluid flow zones in the Buntsandstein sandstones reservoir according well cores and outcrop analysis (Upper Rhine Graben, France)

    NASA Astrophysics Data System (ADS)

    Sébastien, H.; Géraud, Y.; Diraison, M.; Dezayes, C.

    2012-04-01

    Buntsandstein Sandstones (Lower Triassic), located in the Upper Rhine Graben, appears as an easy target for geothermal exploitation. This sedimentary reservoir links more or less permeable argillaceous sandstones intersected by many major faults to the regional thermal anomaly. Petrophysical analysis (permeability, porosity, thermal conductivity, P-wave velocity), performed on cores from several boreholes and samples from several outcrops in the Vosgian Mountain, drive us to characterise fluid and heat transfer capability of the different sedimentary facies present in the Buntsandstein sandstones. First data from well cores analysis indicate that the more permeable and porous (respectively >100mD & >15%) facies are the Playa Lake and fluvial and aeolian sand-sheet, and the fluvial-aeolian marginal erg, whereas the more common facies, the braided rivers within arid alluvial plain, presents permeability <10mD and porosity <10%. Thermal conductivities present high heterogeneities and values range between 1 and 5 W/m/K and their detailed analysis according a new proposed method, drive us to determine fluid flow at formation scale: major fault drive hot fluid flow and feed permeable levels. Second, outcrop analysis allows us to analysis fracturation dispersion and petrophysical modifications induced by fracture and fault in the sandstone series. Barite and quartz precipitation in fracture indicate us fracture orientation and position, compare to major fault position, in which fluid flow has occurs. All data acquired allow us to build a schematic geological block model: this block represent the Buntsandstein sandstone reservoir at depth with the different facies, above the Palaeozoic Granit and below the Muschelkalk limestones, intersecting by faults according the regional major azimuth. According each particular direction the particular fracturation is raised according outcrop data. This bloc points the major zones in which fluid circulation occurs.

  4. Emplacement processes of tuffaceous sandstones at IODP Site C0011B, Nankai Trough, derived from modal analysis

    NASA Astrophysics Data System (ADS)

    Schindlbeck, J. C.; Kutterolf, S.; Freundt, A.

    2011-12-01

    Tuffaceous sandstones are characterized by their high amount (25 to 75%) of pyroclasts in their modal composition. During IODP Expedition 322 three interbeds of tuffaceous sandstones have been found within a moderately lithified and bioturbated silty claystone sequence in the late Miocene (>7.07 to ~9.0 Ma) upper part of the middle Shikoku Basin facies. Of the three sandstones, units 1 and 2 are single beds whereas unit 3 is composed of three beds. Modal analyses of 29 sandstone thin sections reveal systematic vertical changes within each bed. Generally low-density pyroclasts are enriched at the top (50-60 vol%) of each sandstone bed whereas dense lithic components (25-30 vol%) and minerals (25-30 vol%) are enriched at the bottom. The vertically varying abundance of various types of lithic fragments (sedimentary, volcanoclastic and metamorphic) suggests that these have also been segregated according to their respective densities. The highest amount of fine-grained matrix glass is found in the middle of each bed. Pumice and lithic fragments in the middle and upper parts of the sandstone beds carry ash coatings. For sandstone package 3, in contrast to 1 and 2, core pictures and thin section analyses indicate a subdivision in three units showing the same significant variations in top to bottom enrichment. This suggests three sedimentation events following each other in short time intervals. Glass and mineral chemistry of each sandstone bed show no significant vertical variations. Specifically the matrix glass-shard major element compositions are identical to the pumice clast composition in each tuffaceous sandstone bed. The compositions of amphibole and pyroxene crystals differ only slightly between the sandstone packages. Application of the Ridolfi et al. (2009) thermobarometric calculations to amphiboles of sandstone packages 1 and 2 suggests that each of these was derived from a volcanic system comprising both a deep and a shallow magma reservoir. Thickness and

  5. Adaptive Conditioning of Multiple-Point Geostatistical Facies Simulation to Flow Data with Facies Probability Maps

    NASA Astrophysics Data System (ADS)

    Khodabakhshi, M.; Jafarpour, B.

    2013-12-01

    Characterization of complex geologic patterns that create preferential flow paths in certain reservoir systems requires higher-order geostatistical modeling techniques. Multipoint statistics (MPS) provides a flexible grid-based approach for simulating such complex geologic patterns from a conceptual prior model known as a training image (TI). In this approach, a stationary TI that encodes the higher-order spatial statistics of the expected geologic patterns is used to represent the shape and connectivity of the underlying lithofacies. While MPS is quite powerful for describing complex geologic facies connectivity, the nonlinear and complex relation between the flow data and facies distribution makes flow data conditioning quite challenging. We propose an adaptive technique for conditioning facies simulation from a prior TI to nonlinear flow data. Non-adaptive strategies for conditioning facies simulation to flow data can involves many forward flow model solutions that can be computationally very demanding. To improve the conditioning efficiency, we develop an adaptive sampling approach through a data feedback mechanism based on the sampling history. In this approach, after a short period of sampling burn-in time where unconditional samples are generated and passed through an acceptance/rejection test, an ensemble of accepted samples is identified and used to generate a facies probability map. This facies probability map contains the common features of the accepted samples and provides conditioning information about facies occurrence in each grid block, which is used to guide the conditional facies simulation process. As the sampling progresses, the initial probability map is updated according to the collective information about the facies distribution in the chain of accepted samples to increase the acceptance rate and efficiency of the conditioning. This conditioning process can be viewed as an optimization approach where each new sample is proposed based on the

  6. DRAFT LANDSAT DATA MOSAIC: MONTGOMERY COUNTY, TEXAS; HARRIS COUNTY, TEXAS; FORT BEND COUNTY, TEXAS; BRAZORIA COUNTY, TEXAS; GALVESTON COUNTY, TEXAS

    EPA Science Inventory

    This is a draft Landsat Data Mosaic, which contains remote sensing information for Montgomery County, Texas Harris County, Texas Fort Bend County, Texas Brazoria County, Texas Galveston County, and Texas Imagery dates on the following dates: October 6, 1999 and September 29, 200...

  7. Measuring and predicting reservoir heterogeneity in complex deposystems: The fluvial-deltaic Big Injun sandstone in West Virginia

    SciTech Connect

    Patchen, D.G.; Hohn, M.E.; Aminian, K.; Donaldson, A.; Shumaker, R.; Wilson, T.

    1993-04-01

    The purpose of this research is to develop techniques to measure and predict heterogeneities in oil reservoirs that are the products of complex deposystems. The unit chosen for study is the Lower Mississippian Big Injun sandstone, a prolific oil producer (nearly 60 fields) in West Virginia. This research effort has been designed and is being implemented as an integrated effort involving stratigraphy, structural geology, petrology, seismic study, petroleum engineering, modeling and geostatistics. Sandstone bodies are being mapped within their regional depositional systems, and then sandstone bodies are being classified in a scheme of relative heterogeneity to determine heterogeneity across depositional systems. Facies changes are being mapped within given reservoirs, and the environments of deposition responsible for each facies are being interpreted to predict the inherent relative heterogeneity of each facies. Structural variations will be correlated both with production, where the availability of production data will permit, and with variations in geologic and engineering parameters that affect production. A reliable seismic model of the Big Injun reservoirs in Granny Creek field is being developed to help interpret physical heterogeneity in that field. Pore types are being described and related to permeability, fluid flow and diagenesis, and petrographic data are being integrated with facies and depositional environments to develop a technique to use diagenesis as a predictive tool in future reservoir development. Another objective in the Big Injun study is to determine the effect of heterogeneity on fluid flow and efficient hydrocarbon recovery in order to improve reservoir management. Graphical methods will be applied to Big Injun production data and new geostatistical methods will be developed to detect regional trends in heterogeneity.

  8. Diagenetic Patterns of the Cretaceous Baseline Sandstone, Southern Nevada: Implications for Controls on Iron-Oxide Cementation and Coloration

    NASA Astrophysics Data System (ADS)

    Duncan, C. J.; Chan, M. A.

    2015-12-01

    The Cretaceous Baseline Sandstone of the Sevier foreland basin deposits in southern Nevada exhibits intense diagenetic iron-oxide coloration and bleaching, and contains abundant cemented masses. The Baseline Formation is ~1 km thick with three alluvial to fluvial members: the basal White (Kbw) Member, overlain by coeval Red (Kbr) and Overton Conglomerate (Kbo) Members. Iron-oxide diagenetic features occur in two broad classes: 1) bedding parallel coloration facies of diffuse to banded red, pink, purple, white, to yellow colors; and 2) concretionary facies of heavily cemented horizons, pods/lenses, spherical to spheroidal concretions, boxworks, pipes, and irregular concretion forms. A distinctive geometry is the occurrence of large (~1 m diameter) spherical "beach ball" concretions within the Kbr. Preliminary mapping of diagenetic features shows that concretionary facies are more common within a ~125 m interval near the bottom of Kbw, and within the lower ~125 m of Kbr. Intense coloration changes are present throughout Kbw but occur only in the lowermost ~150 m of Kbr. In the Kbw, concretionary forms commonly occur in stratigraphic intervals of fine-grained sandstone, siltstone, and mudstone lithologies, whereas cemented masses are much less common in stratigraphic intervals composed of medium-grained sandstone and conglomerate lithologies. Additionally, both Kbw and Kbr Members exhibit rare examples of wood fragments in the center of iron-oxide concretions, suggesting the importance of organics as nucleation sites for precipitation. The distribution of complex and overprinted diagenetic patterns indicates nested scales of processes involving iron-oxide dissolution, mobilization, and precipitation. Overall stratigraphic architecture influenced formation-scale patterns, but specific lithologies and textures influenced the type and distribution of diagenetic facies at outcrop scales, and organic content encouraged cementation at grain-scales.

  9. Facies, Stratigraphic and Depositional Model of the Sediments in the Abrolhos Archipelago (Bahia, BRAZIL)

    NASA Astrophysics Data System (ADS)

    Matte, R. R.; Zambonato, E. E.

    2012-04-01

    Located in the Mucuri Basin on the continental shelf of southern Bahia state, northeast Brazil, about 70 km from the city of Caravelas,the Abrolhos archipelago is made up of five islands; Santa Barbara, Redonda, Siriba, Guarita and Sueste. The exhumed sediments in the Abrolhos archipelago are a rare record of the turbidite systems which fill the Brazilian Atlantic Basin, and are probably an unprecedented example of a plataform turbidite system (Dr. Mutti, personal communication). Despite the limited area, the outcrops display a wide facies variation produced by different depositional processes, and also allow for the observation of the layer geometries. Associated with such sedimentary rocks, the Abrolhos Volcanic Complex belongs stratigraphically to the Abrolhos Formation. These igneous rocks were dated by the Ar / Ar method, with ages ranging from 60 to 40 My, placing such Volcanic Complex between the Paleocene and Eocene. The sedimentary section is best exposed in the Santa Barbara and Redonda islands and altogether it is 70 m thick. The measured vertical sections show a good stratigraphic correlation between the rocks of the western portion of the first island and those of Redonda Island. However, there is no correlation between the eastern and western portions of Santa Barbara Island, since they are very likely interrupted by the igneous intrusion and possibly by faulting. The sedimentary stack consists of deposits with alternated regressive and transgressive episodes interpreted as high frequency sequences. The coarse facies, sandstones and conglomerates, with abrupt or erosive bases record regressive phases. On the other hand, finer sandstones and siltstones facies, which are partly bioturbated, correspond to phases of a little sediment supply. In the central and eastern portions of Santa Barbara Island, there is a trend of progradational stacking, while both in the western portion of Santa Barbara and in Redonda islands an agradational trend is observed

  10. Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

    NASA Astrophysics Data System (ADS)

    Lin, Botao; Jin, Yan; Pang, Huiwen; Cerato, Amy B.

    2016-04-01

    The success of steam-assisted gravity drainage (SAGD) is strongly dependent on the formation of a homogeneous and highly permeable zone in the land-facies Karamay oil sand reservoirs. To accomplish this, hydraulic fracturing is applied through controlled water injection to a pair of horizontal wells to create a dilation zone between the dual wells. The mechanical response of the reservoirs during this injection process, however, has remained unclear for the land-facies oil sand that has a loosely packed structure. This research conducted triaxial, permeability and scanning electron microscopy (SEM) tests on the field-collected oil sand samples. The tests evaluated the influences of the field temperature, confining stress and injection pressure on the dilation mechanisms as shear dilation and tensile parting during injection. To account for petrophysical heterogeneity, five reservoir rocks including regular oil sand, mud-rich oil sand, bitumen-rich oil sand, mudstone and sandstone were investigated. It was found that the permeability evolution in the oil sand samples subjected to shear dilation closely followed the porosity and microcrack evolutions in the shear bands. In contrast, the mudstone and sandstone samples developed distinct shear planes, which formed preferred permeation paths. Tensile parting expanded the pore space and increased the permeability of all the samples in various degrees. Based on this analysis, it is concluded that the range of injection propagation in the pay zone determines the overall quality of hydraulic fracturing, while the injection pressure must be carefully controlled. A region in a reservoir has little dilation upon injection if it remains unsaturated. Moreover, a cooling of the injected water can strengthen the dilation potential of a reservoir. Finally, it is suggested that the numerical modeling of water injection in the Karamay oil sand reservoirs must take into account the volumetric plastic strain in hydrostatic loading.

  11. Tuffaceous sandstones at Site C0011B, Nankai Trough: Sources and emplacement processes

    NASA Astrophysics Data System (ADS)

    Kutterolf, S.; Scudder, R. P.; Freundt, A.; Labanieh, S.; Naruse, H.; Pickering, K. T.; Underwood, M.; Wu, H.; Saito, S.; Kubo, Y.; Iodp Expedition 322 Scientists

    2010-12-01

    During IODP Expedition 322 at the Nankai Trough, sediments down to the lower Miocene have been drilled, which allows us to constrain the physical, compositional and structural characteristics of the subduction input into the seismogenic zone. One major new discovery was an interval of tuffaceous and volcaniclastic sandstones, which we defined as the middle Shikoku Basin facies. Core, LWD logging and seismic data indicate a channel-fill geometry of the sand body, and transport and deposition probably occurred in the distal part of a submarine fan. This lithologic Unit II is late Miocene (>7.07 to ~9.0 Ma) in age and can be divided into two subunits by the abundance of volcanic glass shards, mineral and/or lithic contents, and bulk-rock XRF data. Subunit IIA consists of moderately lithified bioturbated silty claystone with interbeds of tuffaceous sandstone containing 25 to 75 vol% volcanic glass. Major and trace element glass compositions show that the tuffaceous sandstones all came from a similar source region, probably located along the northeast margin of the Shikoku Basin. Relatively low K concentrations indicate source areas at the Izu-Bonin rear arc (Low K facies of Straub 2003). Chemical variations within the single sandstone packages can be attributed to 1) alteration effects (depletion of Mg, Si, Ca, Fe, Ti, and total oxides and increase of Al and K), and 2) a continuous chemical variation in the glass shard compositions of single depositional units, which reflects the tapping of a source of compositionally zoned tephras. The fact that glass shards in each sandstone either have homogeneous composition or define a well-constrained compositional variation trend argues for spatially restricted source areas as opposed to gravity currents resulting, for example, from collapse of large slope sections. The assemblage of lithic components (unimodal volcanic lithic fragments), the vesicularity (amount and vesicle texture) of pumices, and the deposit structure

  12. Diagenetic capping of carbonate reservoir facies

    SciTech Connect

    Lighty, R.G.

    1984-04-01

    The diagenetic model proposed involves the effect of submarine cementation on previously lithified carbonates, such as submerged relict shelf-margin buildups (e.g., drowned reefs, ooid shoals) or previously subaerially exposed formations (e.g., dune ridges) that were submerged by later sea level rise. These deposits generally have pronounced topographic relief (visible on seismic), good reservoir geometries, and high internal porosity of either primary or secondary origin. Petrologic studies on examples of both of these situations, a submerged early Holocene barrier reef off Florida and a 175-km (110-m) long submerged Pleistocene eolian ridge in the Bahamas, show that their exposed surface and uppermost facies (0.1 m, or 0.3 ft, below top) are further infilled and cemented, creating an extensively lithified, low porosity/low permeability zone or diagenetic cap rock. Quantitative mineralogic studies of occluding cements reveal an exponential reduction in porosity while moving upward into the seal zone. Submarine cements effectively infill and form a surficial permeability barrier that acts to impede further diagenesis and porosity reduction within underlying potential reservoir facies. To form this diagenetic seal only requires that the original carbonate buildup be resubmerged for some brief period of time prior to subsequent burial by sediments. If buildup accumulation later resumes without intermediate sediment burial, a common stratigraphic situation, the diagenetic seal would represent a disconformity separating two similar facies. The early formation of a diagenetic cap rock lends support to models of early hydrocarbon migration and emplacement. Prediction and recognition of submarine diagenetic seals will aid in exploration and development of obvious buildup reservoirs as well as subtle intraformational traps.

  13. Prima facie questions in quantum gravity

    NASA Astrophysics Data System (ADS)

    Isham, C. J.

    The long history of the study of quantum gravity has thrown up a complex web of ideas and approaches. The aim of this article is to unravel this web a little by analysing some of the {\\em prima facie\\/} questions that can be asked of almost any approach to quantum gravity and whose answers assist in classifying the different schemes. Particular emphasis is placed on (i) the role of background conceptual and technical structure; (ii) the role of spacetime diffeomorphisms; and (iii) the problem of time.

  14. A critical compilation of 1,500 large onshore gas reservoirs in Texas Gulf Coast and East Texas

    SciTech Connect

    Kosters, E.C.; Finley, R.J.; Tyler, N.

    1988-01-01

    About 1,500 gas reservoirs in the Texas Gulf Coast and east Texas have a cumulative production of at least 10 bcf. The Gulf Coast contains nearly 90% of these reservoirs. One-third of all reservoirs have produced more than 30 bcf, and another 10% have produced more than 100 bcf. In the Gulf Coast, total production from the greater than 30 bcf reservoirs is 66 to 75% of the cumulative production of all greater than 10 bcf reservoirs, the Oligocene Frio Formation accounting for about 55% of reservoirs and cumulative production. In east Texas, the greater than 30 bcf reservoirs represent 75 to 80% of the cumulative production. Reservoirs are segregated into plays, each identified on the basis of structural and depositional setting, trapping mechanism, and lithology. In the Gulf Coast, 33 gas plays, including 20 subplays, are defined. East Texas contains 12 plays with 7 subplays. Important gas plays occurs in multiple formations in each region. Fluviodeltaic sandstones of the upper Vicksburg and lower Frio Formations, overlying the south Texas Vicksburg fault zone, form the most prolific play of both regions. Other important Tertiary plays are south Texas upper Wilcox shelf-edge deltaic and reworked shallow marine sandstones, deltaic Yegua sandstones in the Houston salt basin, and Miocene stream-plain reservoirs in the central coastal region. Play designation enhances understanding of critical geologic and engineering parameters and is crucial to increasing effectiveness in exploration and production. Future detailed development studies of representative reservoirs within important plays will help define reservoir behavior, allow predictions of potential ultimate recovery, and where applicable, aid in suggesting appropriate recovery enhancement techniques such as infill drilling and recompletion of bypassed zones.

  15. The Lower Cretaceous Chouf Sandstone of Lebanon: Tracking Caledonian tectonism in a Tethyan sediment

    NASA Astrophysics Data System (ADS)

    Asmar, Chloé; Schneider, David A.; Grasemann, Bernhard; Nader, Fadi H.; Tari, Gabor

    2014-05-01

    The Chouf Sandstone is a clastic rock sequence within the Cretaceous succession of Lebanon. Generally, the formation consists of shales, sandstones and shallow water, low-energy limestones with local volcanic horizons and lignites. The typical Chouf Sandstone is dominated by monocrystalline quartz (85-95%) indicating well-sorted sandstone deposited in fluvial to deltaic/littoral environments. The thickness of the Chouf Sandstone is variable, ranging from just a few meters to almost 700 m thick showing prominent lateral facies changes locally. Isopach maps of the Chouf Sandstone reveal systematic variations which could be interpreted as the result of deposition in extensional half-grabens at the margin of a large basin. The overlying Lower Cretaceous neritic carbonate formations do not record any major thickness variations and therefore the Chouf Sandstone may be interpreted as a Lower Cretaceous syn-rift clastic sequence. LA-ICPMS U-Pb geochronology was conducted on detrital zircons from the Chouf Sandstone sampled along the Qartaba Anticline (Mount Lebanon). With the exception of a few Archean outliers, the resulted ages fell into three broad populations: i) a small Paleoproterozoic population, ii) a Grenvillian population, and iii) a Pan-African population (575-650 Ma). One single zircon is slightly younger then the Pan-African population, yielding a 206Pb/238U age of 491 ± 5 Ma. Zircon (U-Th)/He dating on the same samples records cooling through a nominal closure temperature of 180°C and yields Late Ordovician to Early Silurian ages (440-465 Ma), regressed from triplicates of zircon from seven samples across the anticline. Typically, the youngest detrital age that is obtained by U-Pb geochronology, represents a maximum estimate for the depositional age. However, in our study the ca. 490 Ma zircon U-Pb age is interpreted as the age of primary deposition in an Early Paleozoic basin. Combined with the zircon (U-Th)/He cooling ages, our data may suggest the

  16. Stratigraphy and environmental significance of continental Triassic rock of Texas

    SciTech Connect

    Gawloski, T.

    1983-03-01

    The continental Triassic rocks of Texas are represented by four distinct but similar rock groups that exist both in outcrop and in the subsurface and include the Eagle Mills Formation (south-central and northeast Texas), Sycamore Formation (central Texas), Dockum Group (west Texas), and Bissett Formation (southwest Texas). They are clearly terrigenous in nature derived principally from older Paleozoic sedimentary rocks. The rock groups are composed in part or entirely of mudstone, siltstone, medium to coarse-grained sandstone, and pebble to boulder conglomerate (intrabasinal and extrabasinal). The sediments were deposited in alluvial fans, braided and meandering streams, lobate deltas, fan deltas, and lakes. The coarse sandstone and conglomerate are the products of high-energy, short-duration depositional events. Sedimentation was greatly affected by alternating climatic conditions that produced changes in base level, water depth, and lake area as well as the type of streams that flowed into the depositional basins. The character of the rock groups strongly suggests semi-arid to arid deposition typical of the low latitude desert regions of today. Thus, the rocks comprising the Eagle Mills, Sycamore, Dockum, and Bissett Formations appear to be products of continental clastic deposition during a major semi-arid to arid climatic episode, such as that of late Triassic time.

  17. Silicate facies iron-formation of the Egbe-Isanlu Palaeoproterozoic schist belt, southwest Nigeria

    NASA Astrophysics Data System (ADS)

    Annor, A. E.; Olobaniyi, S. B.; Mücke, A.

    1997-02-01

    Field, petrological, mineralogical and geochemical data on the Egbe-Isanlu Palaeoproterozoic schist belt are presented, high-lighting the main features of a silicate facies iron-formation, which hitherto had been described as a metamorphosed, impure sandstone. The iron-formation is relatively thin (max. 15 m) and concordantly interbedded with schistose, semi-pelitic, amphibolitic and talcose host rocks, with which it shares a common polyphase tectonometamorphic history. The last of these is the Pan-African overprint, during which time the iron-formation was locally silicified. The main constituent minerals are garnet (almandine-spessartine solid solution), amphibole (Mn and Ca bearing grunerite-cummingtonite solid solution), quartz and ilmenite. Magnetite was not observed. Geochemical data show that the iron-formation and metasediments are of different origins. The silicate facies iron-formation of Isanlu belongs to the Algoma-type and was derived by the metamorphism of a volcano-exhalative-sedimentary protolith, probably during Eburnian times.

  18. Lacustrine and paludine facies: Cretaceous Baum Limestone, south-central Oklahoma

    SciTech Connect

    Balkan, E.D.; Elmore, R.D.

    1983-03-01

    The Lower Cretaceous Baum Limestone in the Arbuckle Mountains of south-central Oklahoma was deposited in lacustrine and paludine settings near the Cretaceous shoreline. The unit rests unconformably on folded Pennsylvanian rocks and is overlain by and grades into the Paluxy Formation, a sandstone deposit with numerous Ophiomorpha burrows. The lacustrine lithofacies include the following: (1) massive micrite containing charophyte fragments and ostracodes; (2) intraformational conglomerate composed of rounded micrite clasts in a micritic matrix; (3) rounded peloids and coated peloids; (4) laminated micrite; and (5) conglomerate composed of clasts derived from Paleozoic rocks within a micritic matrix. Disintegration of charophytes that grew in the littoral zone of the lake produced the massive micrite. Intraformational conglomerates and peloids represent reworking of massive micrite whereas the other conglomerates represent fluvial influx. Features found within the paludine facies include: (1) brecciated micritic limestone that probably formed as a result of shrinking and swelling due to an oscillating phreatic water table; (2) subspherical nodules of micrite (peds) separated by red shale (plasma) that represent pedogenic alteration of exposed lacustrine mud; and (3) subcylindrial columns composed of micritic limestone representing root-casts. These paludine features formed as a result of pedogenic processes in a marsh that rimmed the shallow lake where the lacustrine facies accumulated.

  19. Origin of middle Silurian Keefer sandstone, east-central Appalachian basin

    SciTech Connect

    Meyer, S.C.; Textoris, D.A.; Dennison, J.M.

    1988-08-01

    The Keefer Sandstone of northeastern West Virginia and western Maryland was deposited in back-barrier, barrier-island, and marine shelf environments along a prograding, storm-dominated, mesotidal coastline of probable low wave energy. Back-barrier sediments were deposited in tidal-flat and lagoonal environments. Barrier-island sediments are dominated by cross-bedded sandstones deposited in deep, laterally migrating tidal inlets. Erosion accompanying the passage of a migrating tidal inlet usually resulted in the removal of underyling shoreface and shelf sands, so that tidal-inlet sandstones commonly lie with a markedly erosive contact on subtidal shales of the underlying Rose Hill Formation. Sand was transported to the shelf from the coastline by downwelling, storm-generated currents. Chamosite ooids formed in gently agitated waters immediately below fair-weather wave base. Outcrops to the east, which preserve back-barrier and barrier-island lithofacies, record a single basinward progradation of the shoreline. However, outcrops farther west, which preserve finer grained sandstone, shale, and limestone shelf lithofacies, document four progradational events in stacked coarsening-upward sequences. Each is typically capped by transgressive sandstones, commonly hematite ooid-bearing, which mark episodes of coastal retreat. Retreat occurred through shoreface and nearshore erosion. Chamosite ooids were transported basinward during coastal retreat and altered to hematite prior to burial. Transgressive shelf sands contain abundant coarse sand eroded from tidal-inlet deposits. Deposition of the Keefer was a response to a decrease in rate of eustatic sea level rise, or a decrease in basin subsidence rate. This was followed by deposition of the transgressive basin facies of the Rochester Shale.

  20. Facies analysis of Nile delta continental shelf sediments off Egypt

    NASA Astrophysics Data System (ADS)

    Frihy, Omran E.; Gamai, Ibrahim H.

    This study evaluates the texture and coarse fraction composition of 108 bottom samples from the Nile delta continental shelf. In total 19 petrological variables were considered for each of the samples, and Q-mode factor analysis of the textural and mineralogical variables yielded 4 factors (facies groups): Facies I. Fine and very fine sands, light minerals, heavy minerals and 'glauconite', extending from the shoreline to the inner shelf and decreasing away from the shoreline. Facies II. Silty sand rich in biogenic components occupies the entire outer shelf and its contiguous lower terraces. Facies III. Mud (silt plus clay), mica and 'glauconite', covering the middle shelf and the upper terraces. Facies IV. Fine to coarse-grained sediments and 'glauconite', locally distributed along the coast off lake ldku, Burullus headland, and Damietta promontory and El Gamil. The configuration patterns of facies I (delta-front), facies III (prodelta) and facies IV (distributary mouth bar or progradational coastal sand) help identify delta lobes related to former distributary branches of the Nile river (Canopic, Saitic, Sebennitic, Atribic and Mendisian). The 4 facies-forming shelf sediments have resulted from sediment dynamics, sea-level fluctuation and differences in sediment input and provenance.

  1. Application of actualistic models to unravel primary volcanic control on sedimentation (Taveyanne Sandstones, Oligocene Northalpine Foreland Basin)

    NASA Astrophysics Data System (ADS)

    Di Capua, Andrea; Groppelli, Gianluca

    2016-05-01

    This work is focused on the Taveyanne Sandstones (Grés de Taveyanne), an Oligocene volcaniclastic turbidite sequence cropping out in the Northern Alpine Molassa between SE France and Central Switzerland, with the aim to investigate the temporal relationship between volcanic activity and sediment supply. Detailed stratigraphic, sedimentological, and petrographic (XRD analyses on mudstones and point counts on sandstones) studies conducted on three sections (Col de l'Oulette and Flaine in SE France, Taveyanne in SW Switzerland) allow a discrimination of three main facies, among which only one is extremely enriched in volcaniclastic detritus and characterized by features similar to those of disaggregated pyroclastic density current deposits. The other two facies are characterized by variable to no volcanic detritus but supplied by crystalline and sedimentary detritus. Such sediment trends are similar to those of modern, volcanically controlled source-to-sink systems. This allows a reinterpretation of the Taveyanne Sandstones as a syn-volcanic turbidite system, episodically supplied by large amounts of volcanic detritus, which periodically modified the drainage paths. Moreover, the well-known temporal and spatial persistence of such modifications in modern settings leads to conciliate the syn-volcanic supply with the location of the volcanic centers in the internal part of the Alps, without invoking particular climatic and tectonic conditions controlling foreland sedimentation.

  2. Facies architecture of basin-margin units in time and space: Lower to Middle Miocene Sivas Basin, Turkey

    NASA Astrophysics Data System (ADS)

    Çiner, A.; Kosun, E.

    2003-04-01

    The Miocene Sivas Basin is located within a collision zone, forming one of the largest basins in Central Turkey that developed unconformably on a foundered Paleozoic-Mesozoic basement and Eocene-Oligocene deposits. The time and space relationships of sedimentary environments and depositional evolution of Lower to Middle Miocene rocks exposed between Zara and Hafik towns is studied. A 4 km thick continuous section is subdivided into the Agilkaya and Egribucak Formations. Each formation shows an overall fining upward trend and contains three members. Although a complete section is present at the western part (near Hafik) of the basin, to the east the uppermost two members (near Zara) are absent. The lower members of both formations are composed of fluvial sheet-sandstone and red mudstone that migrate laterally on a flood basin within a semi-arid fan system. In the Agilkaya Formation that crops out near Zara, alluvial fans composed of red-pink volcanic pebbles are also present. The middle members are composed of bedded to massive gypsum and red-green mudstone of a coastal and/or continental sabkha environment. While the massive gypsum beds reach several 10’s of m in Hafik area, near Zara, they are only few m thick and alternate with green mudstones. In Hafik, bedded gypsums are intercalated with lagoonal dolomitic limestone and bituminous shale in the Agilkaya Formation and with fluvial red-pink sandstone-red mudstone in the Egribucak Formation. The upper members are made up of fossiliferous mudstone and discontinuous sandy limestone beds with gutter casts, HCS, and 3-D ripples. They indicate storm-induced sedimentation in a shallow marine setting. The disorganized accumulations of ostreid and cerithiid shells, interpreted as coquina bars, are the products of storm generated reworking processes in brackish environments. Rapid vertical and horizontal facies changes and the facies associations in both formations reflect the locally subsiding nature of this molassic

  3. Practical characterization of eolian reservoirs for development: Nugget Sandstone, Utah—Wyoming thrust belt

    NASA Astrophysics Data System (ADS)

    Lindquist, Sandra J.

    1988-04-01

    The Jurassic eolian Nugget Sandstone of the Utah-Wyoming thrust belt is a texturally heterogeneous formation with anisotropic reservoir inherited primarily from the depositional environment. Original reservoir quality has been reduced somewhat by cementation and slightly enhanced by dissolution. Low-permeability, gouge-filled micro-faults compartmentalize the formation, whereas intermittently open fractures provide effective permeability paths locally. Where productive, the Nugget Sandstone ranges from approximately 800 to 1050 ft (244-320 m) thick at subsurface depths of 7500 to 15,000 ft (2286-4572 m). Porosity ranges from several percent to 25%, and permeability covers five orders of magnitude from hundredths of milliDarcies to Darcies. Some Nugget reservoirs are fully charged with hydrocarbons. Different stratification types have unique depositional textures, primary and diagenetic mineralogies, and deformational fabrics resulting in characteristic porosity, permeability, permeability directionality, and pore geometry attributes. Such characteristics can be determined from core analysis, mercury injection, nuclear magnetic resonance, conventional log, dipmeter and production data. Nugget dune deposits (good reservoir facies) primarily consist of grainflow and wind-ripple cross-strata, the former of which have the better reservoir quality and the lesser heterogeneity in bedding texture. High-permeability facies are commonly affected by local quartz and nodular carbonate cementation, chlorite (and lesser illite) precipitation, and minor framework and cement dissolution. Gouge-filled micro-faults are the predominant deformational overprint. Interdune, sand-sheet, and other water-associated deposits (poor reservoir facies) are characterized by low-angle wind-ripple laminae and more irregular bedding, some of which is associated with damp or wet conditions. Water-associated Nugget stratification generally contains the finest grained depositional textures and has the

  4. Facies analysis and sequence stratigraphy of the Cenomanian-Turonian mixed siliciclastic-carbonate sediments in west Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Anan, Tarek I.

    2014-06-01

    The unconformity bounded Cenomanian-Turonian succession in west Sinai is subdivided into three formations: the Raha, Abu Qada, and Wata. These rock units were deposited in a mixed siliciclastic-carbonate system on a ramp setting. The studied ramp only includes inner and mid-ramp facies, whereas the outer ramp facies occurs in northern Sinai. Four sequence boundaries (SB) were recognized in the studied formations due to the presence of subaerial exposure or flooding events in the facies stacking pattern. The first and last sequence boundaries (SB1 and SB4) might be considered as Type 1 sequence boundary attributable to the presence of widespread erosion. It is difficult to determine type of the second and third sequence boundaries (SB2 and SB3) because of their minor unconformity and minimal erosion. Determination of systems tracts within the Wata Formation is debatable owing to the action of dolomitization that has destroyed both original components and sedimentary structures. The lowstand systems tracts of the recorded sequences are characterized by sandstones, siltstones, and sandy shales, while fossiliferous shale and limestone with oysters prevailed during sea level rise. The highstand systems tracts are generally characterized by shallow intertidal and subtidal deposits that are made up of abundant oyster wackestones with benthic foraminifera and ostracods.

  5. Pyrite-illite veins in basin-margin facies: evidence for detrital mineral control on pore-fluid evolution

    SciTech Connect

    Bloch, J.D.; Bhattacharyya, D.P.

    1986-05-01

    Diagenesis of the Upper Cambrian Lamotte Sandstone includes the formation of euhedral, predominantly cubic pyrite, and 1M and 2M illite as veins in association with extensive quartz dissolution. The illite in these veins is well crystallized and distinct from pore-filling illite found in the same deposit. The veins occur only in shallow marine-deposited quartzarenites that overlie or are adjacent to basin-margin alluvial fan deposits composed primarily of lithic arenite. Detrital K-feldspar (in volcanic rock fragments) and iron-bearing minerals, particularly biotite, are abundant in the lithic arenites. No apparent source for the sulfur can be identified within the Lamotte Sandstone. Therefore, the authors propose that sulfur-bearing compactional or thermobaric fluids from adjacent basinal facies provided the necessary sulfur for pyrite formation. The migration of these fluids through the lithic arenite, from which iron, potassium, aluminum, and silica were derived, resulted in pyrite and illite deposition in the adjacent quartzarenites. The increased alkalinity and elevated temperature of these fluids resulted in the extensive quartz dissolution. The absence of these pyrite-illite veins in similar quartzarenites basinward of the fan deposits suggests a detrital mineral control on the evolution of these fluids as they migrated through the Lamotte Sandstone. Further, the formation of illite as opposed to kaolinite indicates that these fluids were finally alkaline.

  6. National Uranium Resource Evaluation: Beaumont Quadrangle, Texas

    SciTech Connect

    Henke, J.S.; Joyner, T.M.; Levy, S.S.

    1982-07-01

    The Beaumont Quadrangle, Texas, was evaluated to a depth of 1500 m to identify environments and define areas favorable for the occurrence of uranium deposits. These favorable areas were delineated according to criteria established for the National Uranium Resource Evaluation project funded by the US Department of Energy. Study of the surface geology included interpretation and field followup of hydrogeochemical and stream-sediment reconnaissance data and interpretation and field followup of airborne radiometric data available in the quadrangle area. The surface study was concluded with a carborne scintillometer survey in which scintillometer readings were recorded and outcrop samples were taken, described, and analyzed for uranium content. Subsurface units were evaluated by construction and interpretation of contour structure, isopach, and net-sandstone maps. One environment is identified in this quadrangle as favorable for Texas roll-type uranium deposits in fluvial sandstones of the Oakville-Fleming Formation, Catahoula Formation, and Yegua Formation and in deltaic sediments of the Jackson Group. All other geologic units in the quadrangle are evaluated as unfavorable except the Queen City Formation, which remains unevaluated due to the lack of data.

  7. Intersecting faults and sandstone stratigraphy at the Cerro Prieto geothermal field

    SciTech Connect

    Vonder Haar, S.; Howard, J.H.

    1980-02-01

    The northwest-southeast trending Cerro Prieto fault is part of a major regional lineament that extends into Sonaro and has characteristics of both a wrench fault and an oceanic transform fault. The distribution of lithologies and temperature within the field was studied by comparing data from well cuttings, cores, well logs, and geochemical analyses. Across the earliest developed portion of the field, in particular along a 1.25-km northeast-southwest section from well M-9 to M-10, interesting correlations emerge that indicate a relationship among lithology, microfracturing, and temperature distribution. In the upper portion of Reservoir A of this stratigraphic section, between 1200 and 1400 m, the percentage of sandstones ranges from 20 to 55. Temperatures are 225/sup 0/ to 275/sup 0/C based on well logs, calcite isotope maxima, and Na-K-Ca indices. The study shows that an isothermal high in this vicinity corresponds to the lowest total percentage of sandstones. Scanning electron microphotographs of well cores and cuttings from sandstone and shale units reveal clogging, mineral dissolution, and mineral precipitation along microfractures. The working hypothesis is that these sandy shale and siltstone facies are most amenable to increased microfracturing and, in turn, such microfracturing allows for higher temperature fluid to rise to shallower depths in the reservoir.

  8. Aux Vases Sandstone diagenesis: Implications for hydrocarbon recovery from southern Illinois reservoirs

    SciTech Connect

    Seyler, B.D.; Beaty, D.S.; Huff, B.G. )

    1991-03-01

    The Aux Vases Sandstone (Mississippian) is a problematic yet productive reservoir in the Illinois basin. The Aux Vases Formation was deposited in a mixed siliciclastic-carbonate offshore environment. Hydrocarbon reservoirs are dominantly elongate sandstone bodies interpreted as subtidal facies within a prograding tidally influenced deposystem. Oil saturated zones, in most cases, are composed of fine-grained, cross-bedded, friable, feldspathic quartz sandstone. Resistivity logs, even from productive wells, are typically characterized by unusually low resistivities (2-4 ohms) that lead to high calculated water saturations. X-ray diffraction, SEM/EDS, and thin section studies were used to analyze diagenetic processes that may affect hydrocarbon production in several Aux Vases reservoirs. Diagenetic processes common to the field studied include: (1) early calcite cementation occluding primary porosity and inhibiting compaction, (2) dissolution of feldspar grains to form authigenic clay, (3) dissolution of early calcite cement, (4) diagenesis of detrital clay minerals into new authigenic clay minerals, and (5) multiple stages of quartz overgrowths that reduce porosity. Commonly used drilling and completion practices may adversely affect reservoir quality by reacting with diagenetic products. Loosening of the fine mineral fraction that causes migration of fines and swelling of expandable clay minerals are examples of this type of damage. Knowledge of reservoir mineralogy and diagenesis may influence drilling and completion practices and affect selection of secondary and tertiary recovery methods.

  9. National Uranium Resource Evaluation: Marfa Quadrangle, Texas

    SciTech Connect

    Henry, C D; Duex, T W; Wilbert, W P

    1982-09-01

    The uranium favorability of the Marfa 1/sup 0/ by 2/sup 0/ Quadrangle, Texas, was evaluated in accordance with criteria established for the National Uranium Resource Evaluation. Surface and subsurface studies, to a 1500 m (5000 ft) depth, and chemical, petrologic, hydrogeochemical, and airborne radiometric data were employed. The entire quadrangle is in the Basin and Range Province and is characterized by Tertiary silicic volcanic rocks overlying mainly Cretaceous carbonate rocks and sandstones. Strand-plain sandstones of the Upper Cretaceous San Carlos Formation and El Picacho Formation possess many favorable characteristics and are tentatively judged as favorable for sandstone-type deposits. The Tertiary Buckshot Ignimbrite contains uranium mineralization at the Mammoth Mine. This deposit may be an example of the hydroauthigenic class; alternatively, it may have formed by reduction of uranium-bearing ground water produced during diagenesis of tuffaceous sediments of the Vieja Group. Although the presence of the deposit indicates favorability, the uncertainty in the process that formed the mineralization makes delineation of a favorable environment or area difficult. The Allen intrusions are favorable for authigenic deposits. Basin fill in several bolsons possesses characteristics that suggest favorability but which are classified as unevaluated because of insufficient data. All Precambrian, Paleozoic, other Mesozoic, and other Cenozoic environments are unfavorable.

  10. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies.

    PubMed

    Stegen, James C; Konopka, Allan; McKinley, James P; Murray, Chris; Lin, Xueju; Miller, Micah D; Kennedy, David W; Miller, Erin A; Resch, Charles T; Fredrickson, Jim K

    2016-01-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies-oxidized, reduced, and transition-within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness-the number of microbial taxa-was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions. PMID:27469056

  11. Statistics and Title VII Proof: Prima Facie Case and Rebuttal.

    ERIC Educational Resources Information Center

    Whitten, David

    1978-01-01

    The method and means by which statistics can raise a prima facie case of Title VII violation are analyzed. A standard is identified that can be applied to determine whether a statistical disparity is sufficient to shift the burden to the employer to rebut a prima facie case of discrimination. (LBH)

  12. Trace fossils and sedimentary facies from a Late Cambrian-Early Ordovician tide-dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions

    USGS Publications Warehouse

    Mangano, M.G.; Buatois, L.A.; Acenolaza, G.F.

    1996-01-01

    The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick-bedded planar cross-stratified quartzose sandstones (A), thin-bedded planar cross-stratified quartzose sandstones and mudstones (B), wave-rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from facies A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide-dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C. The Cruziana ichnocoenosis is preserved on the soles of thin-bedded planar cross-stratified quartzose sandstones (facies B). This ichnocoenosis consists of Conostichus isp., Cruziana omanica, C. semiplicata, C. cf. tortworthi, Cruziana isp. Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarius, R. latus, and R. isp. The occurrence of Cruziana semiplicata, C. omanica, C. cf. tortworthi, and Rusophycus latus supports a Late Cambrian-Tremadoc age. Slabbing of Cruziana shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of Rusophycus isp. that most likely represent trilobite nesting burrows. The Cruziana ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting. The Skolithos ichnocoenosis is represented by high to low density vertical burrows of Skolithos linearis, which extend downwards to the quartzose sandstone soles of facies B and cross the Cruziana ichnocoenosis. The

  13. An overview of the Cretaceous stratigraphy and facies development of the Yazd Block, western Central Iran

    NASA Astrophysics Data System (ADS)

    Wilmsen, Markus; Fürsich, Franz Theodor; Majidifard, Mahmoud Reza

    2015-04-01

    The Cretaceous successions of the Yazd Block, the western of three structural blocks of the Central-East Iranian Microcontinent (CEIM), have been studied using an integrated approach of litho-, bio- and sequence stratigraphy associated with litho-, bio- and microfacies analyses. The Cretaceous System of that area is in excess of 5 km thick and a generalized relative sea-level curve can be inferred from the facies and thickness development. This curve can be subdivided into two transgressive-regressive megacycles (TRMs), separated by a major tectonic unconformity in the Upper Turonian. TRM 1 comprises the Early Cretaceous to Middle Turonian, TRM 2 the Coniacian to Maastrichtian. TRM 1 starts with up to 1500-m-thick conglomerates and sandstones covering Palaeozoic-Triassic basement rocks, metasediments, or Upper Jurassic-lowermost Cretaceous granites. The basal tectonic unconformity, related to the Late Cimmerian event (Jurassic-Cretaceous boundary interval), shows a pronounced palaeo-relief that is levelled by the basal siliciclastic formations. Sparse biostratigraphic data from calcareous intercalations in the upper part of these strata indicate a Hauterivian to Barremian age. The Aptian facies development is marked by the onlap of thick-bedded, micritic carbonates with abundant orbitolinid foraminifera and rudists representing a large-scale shallow-marine carbonate platform system that fringed the Yazd Block in the north and west. These platforms are up to 1000 m thick and drowned during the middle to Late Aptian, followed by up to 1500-m-thick basinal marly sediments of Late Aptian to mid-Late Albian ages, representing the maximum relative sea-level during TRM 1. During the latest Albian-Middle Turonian, a gradual shallowing is indicated by progradation of shallow-water skeletal limestones separated by marl tongues, representing a carbonate ramp system. Strata of TRM 2 overlie older units along a regional angular unconformity and indicate tectonic stability and

  14. Facies distribution, heterogeneity study and numerical 3D modeling of a multilayered Rhaetian-Lower Cretaceous aquifer succession in the Höllviken Halfgraben, SW Skåne, Sweden - assessment of suitability for storage of CO2

    NASA Astrophysics Data System (ADS)

    Erlström, M.; Niemi, A.; Lindström, S.; Gunnarsson, N.; Daher, S. Bou

    2012-04-01

    Several variably thick sandstone beds are found within a 200-300 m thick Rhaetian-Lower Cretaceous succession in the Höllviken Halfgraben. Many of these are considered as potential aquifers for geothermal energy and possibly also for CO2 storage. One of the challenges in evaluating this potential lies within the task to assess the frequency and distribution patterns of the sandstone units in the multilayered succession. For this purpose biostratigraphic analyses, lithofacies investigations and numerical modeling have been conducted. The main part of the investigated succession along the margins of the Danish Basin, including the Höllviken Halfgraben reflects a highly dynamic coastline, which along with differential subsidence, and possible multiple sediment sources has resulted in a difficulty to correlate lithological units between boreholes. Four main lithofacies, of which one is fine-grained sandstone, are identified by use geophysical wire line logs and a few cored reference boreholes. The gradual transition between the identified lithofacies implies a genetic relation between the different facies, related to relative sea level fluctuation coupled with tectonic activity. This has, thus, yielded high degree of heterogeneity regarding distribution and frequency of the different facies. The four defined facies can be assigned to a tide dominated deltaic setting, which could further be divided into sub-environements based on proximity to the shoreline. There are only 2-3 sandstone units which have a regional distribution and that can be defined from a sequence stratigraphic analysis and correlated by use of the biostratigraphic results. The majority of beds have, however a local interfingering distribution pattern. A frequency study of the different facies in five wells indicate that the sandstone facies is more common adjacent to the bounding fault zones, thus indicating syndepositional surrounding highs generating eroded clastics entering the H

  15. Tubiphytes-archaeolithoporella-girvanella reefal facies in Permian buildup, Mino terrane, central Japan

    NASA Astrophysics Data System (ADS)

    Sano, Hiroyoshi; Horibo, Kenji; Kumamoto, Yasuko

    1990-10-01

    The Lower to Middle Permian Okumino buildup of the Mino terrane, central Japan, formed a carbonate cap on a seamount which was sitting in an open-ocean realm. Microscopic examination reveals considerable amounts of Tubiphytes, Archaeolithoporella, and Girvanella in these rocks. These low laminar encrusting organisms together with cystopore bryozoa and syndepositional radial-fibrous cements formed bindstones. The bindstones are interpreted as having formed wave-resistant algal reefal mounds on the marginal terrace of the Okumino buildup which also has the lagoonal flat, sand bar or shoal, and foreslope facies. The Okumino buildup is closer in its biotic association of major encrusting organisms to the Trogkofel buildup in southern Alps than to the Capitan Reef Complex in New Mexico and Texas. The similarity implies that Tubiphytes and Archaeolithoporella were the most predominant and significant rock-forming encrusting organisms in Early to early Middle Permian times.

  16. Shoreline depositional environments of Glen Rose Formation (lower Cretaceous) in type area, Somervell and Hood Counties, Texas

    SciTech Connect

    Bergan, G.R.

    1988-09-01

    The studied interval of the Glen Rose Formation (Aptian-Albian) comprises a clastic-to-carbonate sequence, which was deposited in a seaward-fining tidal flat-salt marsh complex. Eight distinct facies were identified, including the calcareous sandstone, calcareous shale, bivalve shale, oyster shale, transitional terrigenous-carbonate, dolomite, bioclastic packstone-grainstone, and shell-fragment wackestone facies. These facies were deposited in sand flats; small fluvial creeks; an ecologically complex, mud-dominated intertidal flat; and a subtidal, nearshore lagoon. Thin bioclastic packstone-grainstones and dolomites of the high energy intertidal and supratidal environments regularly interrupt the terrigenous clastic facies. Abundant nearshore features include salt-tolerant land plants, dinosaur tracks, desiccation cracks, and localized concentrations of evaporites. A warm semi-arid to arid climate is indicated. This sequence is interpreted as being comparable to the Holocene salt marshes on Sapelo Island, Georgia, based on similar lithofacies, sedimentary structures, and biological components.

  17. New insights into the provenance of Saudi Arabian Palaeozoic sandstones from heavy mineral analysis and single-grain geochemistry

    NASA Astrophysics Data System (ADS)

    Bassis, Alexander; Hinderer, Matthias; Meinhold, Guido

    2016-03-01

    Saudi Arabian Palaeozoic siliciclastics cover a stratigraphic range from the Cambrian to the Permian. They crop out along the eastern margin of the Arabian Shield and are comprised of highly mature sandstones. Their heavy mineral assemblage reflects their mineralogical maturity and is dominated by the ultra-stable phases zircon, tourmaline and rutile. Less stable accessories are apatite, staurolite and garnet. Standard heavy mineral analysis of samples from two study areas in central/northern (Tabuk area) and southern (Wajid area) Saudi Arabia reveals distinct changes in provenance. Cambrian-Ordovician sandstones are first-cycle sediments, probably sourced from the 'Pan-African' basement. The overlying Hirnantian glaciogenic deposits consist of recycled Cambrian-Ordovician material. Devonian-Permian sandstones show a significant influx of fresh basement material, as attested by an increase of meta-stable heavy minerals. Single-grain geochemical analysis of rutile and garnet has proven to be a powerful supplementary technique. Rutile varietal studies reveal distinct differences in host rock lithologies between the two study areas: the Tabuk area contains predominantly felsic rutiles, whereas the Wajid area has more mafic input. Zr-in-rutile thermometry identified granulite-facies detritus in the lower Palaeozoic of the Tabuk area and has the potential to further define source areas. The distribution patterns of garnet host rock lithologies are remarkably similar in both study areas. They are dominated by amphibolite-facies metasediments and intermediate to felsic igneous rocks. Garnets derived from granulite-facies metasediments, which are scarce in the Arabian-Nubian Shield, also occur. Possible source rocks for high-grade garnets can be found in Yemen or farther south in the Mozambique Belt.

  18. Texas Heart Institute

    MedlinePlus

    ... Join us! James T. Willerson MD Cardiovascular Seminar Texas Heart Institute Journal Scientific Publications Library & Learning Resources ... Education 12th Annual Diabetes Symposium September 17, 2016 Texas Heart Institute Program Director: Mandeep Bajaj, MD Clinical ...

  19. Multiscale heterogeneity characterization of tidal channel, tidal delta and foreshore facies, Almond Formation outcrops, Rock Springs uplift, Wyoming

    SciTech Connect

    Schatzinger, R.A.; Tomutsa, L.

    1997-08-01

    In order to accurately predict fluid flow within a reservoir, variability in the rock properties at all scales relevant to the specific depositional environment needs to be taken into account. The present work describes rock variability at scales from hundreds of meters (facies level) to millimeters (laminae) based on outcrop studies of the Almond Formation. Tidal channel, tidal delta and foreshore facies were sampled on the eastern flank of the Rock Springs uplift, southeast of Rock Springs, Wyoming. The Almond Fm. was deposited as part of a mesotidal Upper Cretaceous transgressive systems tract within the greater Green River Basin. Bedding style, lithology, lateral extent of beds of bedsets, bed thickness, amount and distribution of depositional clay matrix, bioturbation and grain sorting provide controls on sandstone properties that may vary more than an order of magnitude within and between depositional facies in outcrops of the Almond Formation. These features can be mapped on the scale of an outcrop. The products of diagenesis such as the relative timing of carbonate cement, scale of cemented zones, continuity of cemented zones, selectively leached framework grains, lateral variability of compaction of sedimentary rock fragments, and the resultant pore structure play an equally important, although less predictable role in determining rock property heterogeneity. A knowledge of the spatial distribution of the products of diagenesis such as calcite cement or compaction is critical to modeling variation even within a single facies in the Almond Fin. because diagenesis can enhance or reduce primary (depositional) rock property heterogeneity. Application of outcrop heterogeneity models to the subsurface is greatly hindered by differences in diagenesis between the two settings. The measurements upon which this study is based were performed both on drilled outcrop plugs and on blocks.

  20. "Sydney sandstone": Heritage Stone from Australia

    NASA Astrophysics Data System (ADS)

    Cooper, Barry; Kramar, Sabina

    2014-05-01

    Sydney is Australia's oldest city being founded in 1788. The city was fortunate to be established on an extensive and a relatively undeformed layer of lithified quartz sandstone of Triassic age that has proved to be an ideal building stone. The stone has been long identified by geologists as the Hawkesbury Sandstone. On the other hand the term "Sydney sandstone" has also been widely used over a long period, even to the extent of being utilised as the title of published books, so its formal designation as a heritage stone will immediately formalise this term. The oldest international usage is believed to be its use in the construction of the Stone Store at Kerikeri, New Zealand (1832-1836). In the late 19th century, public buildings such as hospitals, court houses as well as the prominent Sydney Town Hall, Sydney General Post Office, Art Gallery of New South Wales, State Library of New South Wales as well as numerous schools, churches, office building buildings, University, hotels, houses, retaining walls were all constructed using Sydney sandstone. Innumerable sculptures utilising the gold-coloured stone also embellished the city ranging from decorative friezes and capitals on building to significant monuments. Also in the late 19th and early 20th century, Sydney sandstone was used for major construction in most other major Australian cities especially Melbourne, Adelaide and Brisbane to the extent that complaints were expressed that suitable local stone materials were being neglected. Quarrying of Sydney sandstone continues today. In 2000 it was recorded noted that there were 33 significant operating Sydney sandstone quarries including aggregate and dimension stone operations. In addition sandstone continues to be sourced today from construction sites across the city area. Today major dimension stone producers (eg Gosford Quarries) sell Sydney sandstone not only into the Sydney market but also on national and international markets as cladding and paving products

  1. Microstructure of deformed graywacke sandstones

    SciTech Connect

    Dengler, L.A.

    1980-03-05

    Microsctures in low-permeability graywacke sandstones were studied by optical and scanning electron microscopy (SEM). SEM specimens were prepared by ion-bombardment of thick polished samples. The undeformed rock contains grains in a matrix composed primarily of authigenic chlorite and kaolinite. Chlorite platelets are randomly arranged in face-to-edge relation to one another. Kaolinite occurs as pseudohexagonal crystals stacked face-to-face in pore filling books. Uniaxial-stress experiments covered a range of confining pressures from .1 to 600 MPa. Below 50 MPa confining pressure, intergranular fracturing occurs within the fault zone and near the sample's cylindrical surface. Between 100 and 300 MPa confining pressure, fault zones contain highly fractured grains, gauge and slickensides on grain surfaces. At 600 MPa, the sample contains a diffuse shear zone of highly fractured grains and no well-defined fault. In all samples, the distribution of microcracks is heterogeneous. Different clay minerals exhibit different modes of deformation. Chlorite structure responds to applied stress by compaction, reducing both pore size and volume. Chlorite platelets are plastically deformed in even the least strained samples. Kaolinite does not deform plastically in any of the samples examined. Deformation of kaolinite is restricted to toppling of the book structure. Dilatant crack growth was studied in two samples unloaded prior to failure. Uniaxially-strained samples deform primarily along grain boundaries, producing intergranular cracks and realignment of chlorite platelets. Intragranular crack density is linearly related to axial-strain, although grains are less fractured than in uniaxially-stressed samples tested at equivalent mean pressures. Cracks are rarely longer than a grain diameter. Nuclear-explosively deformed samples were recovered after the Rio Blanco gas stimulation experiment. (JGB)

  2. TENET: Texas Education Network.

    ERIC Educational Resources Information Center

    Stout, Connie

    The Texas Education Agency sought to create an enhanced electronic communications network (TENET) capable of transmitting information among and between the members of the public education system in Texas. They contracted with the Texas Higher Education Network (THEnet), an existing distributed network which is an NSF (National Science Foundation)…

  3. Treasured Texas Theaters

    ERIC Educational Resources Information Center

    Horton, Anita

    2012-01-01

    Dallas artist Jon Flaming's deep love of Texas is evident in his paintings and sculpture. Although he has created one sculptural Texas theater, his work primarily showcases old Texas barbershops, vacant homes, and gas stations. In this article, the author describes how her students, inspired by Flaming's works, created three-dimensional historical…

  4. East Texas Storytellers.

    ERIC Educational Resources Information Center

    Anderson, Brandi, Ed.

    1987-01-01

    Written and published by the students at Gary High School, Gary, Texas, "Loblolly Magazine" is published twice a year. Issues are frequently devoted to a distant theme. The theme of this issue, "East Texas Storytellers," attempts to capture some of the local color and regional history of eastern Texas. The first article, "Timothy Griffith, Master…

  5. Tidal-bundle sequences in the Jordan Sandstone (Upper Cambrian), southeastern Minnesota, U.S.A.: Evidence for tides along inboard shorelines of the Sauk Epicontinental Sea

    USGS Publications Warehouse

    Tape, C.H.; Cowan, Clinton A.; Runkel, Anthony C.

    2003-01-01

    This study documents for the first time tidal bundling in a lower Paleozoic sheet sandstone from the cratonic interior of North America, providing insights into the hydrodynamics of ancient epicontinental seas. The Jordan Sandstone (Upper Cambrian) in the Upper Mississippi Valley contains large-scale planar tabular cross-sets with tidal-bundle sequences, which were analyzed in detail at an exceptional exposure. Tidal-bundle sequences (neap-spring-neap cycles) were delineated by foreset thickening-thinning patterns and composite shale drapes, the latter of which represent accumulations of mud during the neap tides of neap-spring-neap tidal cycles. Fourier analysis of the bundle thickness data from the 26 measurable bundle sequences revealed cycles ranging from 15 to 34 bundles per sequence, which suggests a semidiurnal or mixed tidal system along this part of the Late Cambrian shoreline. We extend the tidal interpretation to widespread occurrences of the same facies in outcrops of lesser quality, where the facies is recognizable but too few bundles are exposed for tidal cycles to be measured. By doing so, this study shows that tidally generated deposits have a significant geographic and temporal extent in Upper Cambrian strata of central mid-continent North America. The deposition and preservation of tidal facies was related to the intermittent development of shoreline embayments during transgressions. The tidally dominated deposits filled ravined topographies that were repeatedly developed on the updip parts of the shoreface. Resulting coastal geomorphologies, accompanied perhaps by larger-scale changes in basinal conditions and/or configuration, led to changes in depositional conditions from wave-dominated to tide-dominated. Outcrops of the Jordan Sandstone tidal facies in the Upper Mississippi Valley represent the farthest inboard recorded transmission of ocean-generated tides in the Laurentian epicontinental seas, demonstrating that tidal currents were

  6. Depostional systems, provenance, and sequence stratigraphy, Carter and [open quotes]Millerella[close quotes] sandstones of northeast Mississippi

    SciTech Connect

    Cleaves, A.W. II )

    1993-09-01

    The subsurface [open quotes]Millerella[close quotes] and Carter sandstones (middle Chesterian) of the Black Warrior basin represent the highest units of the thick Muldon clastics deltaic facies tract. Lowstand marine conditions during Carter deposition allowed for southeastwardly progradation of five distinct deltaic lobe complexes onto the stable northern shelf of the basin. With each of these lobes, both an [open quotes]A[close quotes] (upper) and a [open quotes]B[close quotes] (lower) reservoir unit can be identified. The [open quotes]B[close quotes] sandstone produces from delta-front sheet sands, channel-mouth bars, and possible bar fingers of river-dominated deltas. The more prolific [open quotes]A[close quotes] subdivision contains reservoirs in upper delta-plain point bars, crevasse splays, and distributary channel fills. The most easterly of the lobes, preserved in the Bean's Ferry field of Itawamba County, comprises an amalgamated valley-fill facies that removed a maximum of 250 ft (76 m) of lower Bangor platform carbonates. In contrast, the [open quotes]Millerella[close quotes] sandstone is a series of unconnected pods that formed as marine-reworked sand bodies during a eustatic rise in sea level. The average detrital sand grain composition for four cores taken in Monroe County is 94.7% monocrystalline quartz, 2.9% polycrystalline quartz, 1.6% albite feldspar, 0.1% low-rank metamorphic rock fragments, 0.5 chert, and 0.2% muscovite. These data indicate that neither the Ozark uplift nor the Ouachita orogen could have acted as the principal source area for the Carter and [open quotes]Millerella[close quotes] sandstones. More likely, the sedimentary-igneous terrains along the northern margin of the Illinois basin served this function. A major eustatic lowstand brought this mineralogically mature sediment across the Illinois basin through incised valleys to the northern self of the Black Warrior basin.

  7. A sequence stratigraphic study of the Tangaroa Sandstone, Taranaki Basin, New Zealand

    SciTech Connect

    Gresko, M.D.; Jordan, D.W.; Thompson, P.R. )

    1990-05-01

    Seismic sequence interpretation of the Tangaroa Sandstone, combined with detailed biostratigraphic analysis, well log interpretation, and core descriptions, confirm the Tangaroa as a late Eocene-early Oligocene, sand-rich, submarine fan complex within the Taranaki basin of northwest New Zealand. The Tangaroa Sandstone is underlain by deep-water shales (Eocene Kaiata Formation) and overlain by a thick deep-water limestone (Oligocene Te Kuiti Formation), and typically consists of two, 25-150-m-thick vertically stacked sandstones, separated by a thin (8 m) limestone. Seismic isochron thickness maps of the Tangaroa interval display a fan-shaped geometry. Internal seismic facies are dominated by erosional channels and progradational wedges. The erosional channels, to 1-5 km wide and approximately 70-150 m thick, are interpreted as upper to mid-fan feeder channels. Thin progradational wedges are located basinward of the channels. Paleobathymetic data, based on micropaleontology, indicate a shelf-to-deep-water genesis of the Tangaroa. Conventional core data suggest that the Tangaroa comprises fine- to coarse-grained clastics that were deposited by debris flows, liquefied flows, and turbidites. Using seismic sequence techniques, verified by biostratigraphic control, the Tangaroa Sandstone is subdivided into two sequences: the Lower Tangaroa sequence and the Upper Tangaroa sequence, which formed during two distinct relative lowstands in sea level. The intervening limestone and the overlying Te Kuiti Limestone, apparently were deposited during periods of relative highstands in sea level. The Eocene Oligocene boundary is located in the thin limestone of the Lower Tangaroa sequence.

  8. Geometric and sedimentologic characteristic of Mid-Miocene lowstand reservoir sandstones, offshore northwest Java, Indonesia

    SciTech Connect

    Lowry, P.; Kusumanegara, Y.; Warman, S.

    1996-12-31

    Numerous reservoirs in the Upper Cibulakan Formation (Mid-Miocene) of the Offshore Northwest Java shelf occur in sharp-based sandbodies that range from less than 1 m up to 10 m in thickness. Well-log derived net-sand isopach and seismic amplitude maps of these sandbodies depict elongate features, that are 1-2 km wide and 5-8 km long. The orientation of the longest axis of these sandbodies is predominantly north-south. Conventional cores reveal that these sandbodies are burrowed to completely bioturbated sandstones. Common trace fossils associated with these sandbodies include Ophiomorpha, Teichichnus and Thalassinoides. The lower contact of these sands is typically sharp and is commonly associated with a Glossifungites surface and siderite mud clasts. Overlying and underlying mudstones are relatively devoid of burrowing. Benthonic foraminifera assemblages within these mudstones indicate inner to outer neritic conditions in a relatively restricted marine setting. The upper contact of these sandstones is gradational over a 0.5 to 1m interval. Sandbodies of the same age and similar facies were observed in outcrops in onshore west Java. Here, they can be observed to pinch out over a distance of 500 m. The lower bounding contact appears discordant with underlying interbedded sandstones and mudstones. Several of the sandstones contain abundant accumulations of the large, open marine, benthonic foraminifera Cycloclypeus and Lepidocyclina. Occasionally the concentration of these large foraminifera form limestones within the sharp-based sandbodies. These bioclastic deposits commonly exhibit planar-tabular and trough cross-stratification. The sandbodies are interpreted as having been emplaced during relative falls in sea-level within a large Mid-Miocene embayment. Our understanding of their geometry and sedimentologic characteristics is leading to a more effective exploitation strategy for these sandbodies in the Offshore Northwest Java area.

  9. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

    PubMed Central

    Stegen, James C.; Konopka, Allan; McKinley, James P.; Murray, Chris; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-01-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness—the number of microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions. PMID:27469056

  10. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

    NASA Astrophysics Data System (ADS)

    Stegen, James C.; Konopka, Allan; McKinley, James P.; Murray, Chris; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-07-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness—the number of microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions.

  11. Seismic facies interpretation of Mesozoic sequences, Shiwandashan basin, China

    SciTech Connect

    Leu, Leikuang; Armentrout, J.M.; Faz, J.J. )

    1991-03-01

    Integration of outcrop and subsurface geologic data with seismic facies analysis identified three exploration plays in Shiwandashan basin, southeastern China: Triassic Submarine Fan: Elongate-mounded packages of variable amplitude, discontinuous, nonparallel reflections occur basinward of the slope and are downlapped by prograding slope clinoforms. This facies is undrilled. Basin modeling suggests the mounded seismic facies correlates with outcrops of Triassic marine siliclastic turbidites which grade laterally into basinal mudstone/limestone couplets. Triassic Shelf Carbonates: Localized, high amplitude parallel reflections occur in a retrograde succession at the top of the Triassic prograding clinoform. These high amplitude seismic facies are calibrated with drilled carbonate facies and are correlated with outcrops of upper Triassic shelf and shelf-edge reefs that contain two generations of migrated hydrocarbons. Jurassic Fan Deltas: Thick northeast-southwest bidirectional downlapping hummocks of variable amplitude reflections and intersecting northwest downlapping clinoforms form large mounds and grade laterally to moderately continuous parallel reflections. The hummocky-clinoform mound facies is calibrated by drilled, poorly sorted conglomerates and correlates with outcrops of a Jurassic synrift basin-fill succession. These Jurassic rocks are interpreted as fan-deltas grading laterally to sandy fluvial and shaley lacustrine facies. The geochemical data suggest a potential gas-prone play for the Triassic submarine fans and potential oil-prone play for the stratigraphically shallower Triassic shelf and shelf-edge reefs. The Jurassic fan delta play drilled tight with no hydrocarbons.

  12. Statewide summary for Texas

    USGS Publications Warehouse

    Handley, Lawrence R.; Spear, Kathryn A.; Gibeaut, Jim; Thatcher, Cindy

    2014-01-01

    Seafood landed at Texas ports valued $240 million in 2011, and recreational saltwater fishing alone provided nearly 17,000 jobs (Texas GLO, 2013). Fishes directly dependent upon wetland habitats include multiple shrimp species, blue crab, eastern oyster, black drum, flounder, sheepshead, and snapper. Texas has the highest number of hunters, anglers, and hunting expenditures in the nation (U.S. Fish and Wildlife Service, 2012). Hunting yields $2.3 billion for the state, and recreational fishing yields $3.2 billion. Texas is the top birding destination in the Nation. Tourism in Texas generates $7.5 billion for the state, and wildlife viewing generates $2.9 billion.

  13. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in Frio fluvial-deltaic reservoirs of South Texas. Technical progress report, July 1--September 30, 1995

    SciTech Connect

    Tyler, N.; Levey, R.A.

    1995-10-10

    Advanced reservoir characterization techniques are being applied to selected reservoirs in the Frio fluvial-deltaic sandstone trend in order to maximize the economic producibility of resources in this mature oil play. More than half of the reservoirs in this play have already been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery methods. This project is developing interwell-scale geological facies models and assessing engineering attributes of reservoirs in selected fields in order to characterize reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. Phase 1 consisted of reservoir selection and initial framework characterization. Phase 2 involved advanced characterization to delineate incremental resource opportunities. Subtasks included volumetric assessments of untapped and incompletely drained oil along with an analysis of specific targets for recompletion and strategic infill drilling. The third phase of the project consists of documentation of Phase 2 results, technology transfer, and the extrapolation of specific results from reservoirs in this study to other heterogeneous fluvial-deltaic reservoirs within and beyond the Frio play in South Texas. Project work during this quarter consisted of (1) documentation of Phase 2 tasks associated with the delineation of untapped and incompletely drained reservoir compartments and new pool reservoirs in selected Frio fluvial-deltaic sandstone intervals in Rincon and Tijerina-Canales-Blucher fields, as well as (2) Phase 3 tasks related to the transfer of the technologies to industry that aided in delineation.

  14. Surface energy characterization of sandstone rocks

    NASA Astrophysics Data System (ADS)

    Arsalan, Naveed; Palayangoda, Sujeewa S.; Burnett, Daniel J.; Buiting, Johannes J.; Nguyen, Quoc P.

    2013-08-01

    The fundamental forces of adhesion are responsible for the spreading of fluids such as crude oil/brine on the reservoir rock surface. These physico-chemical interactions determine the surface energetics of a reservoir and thus their wetting phenomena. Inverse Gas Chromatography (IGC) is introduced to characterize the surface energy of sandstones (Ottawa sand and Berea sandstone). The surface chemistry of the sandstone rocks is further elucidated using X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) techniques. The behavior of the polar and non-polar interaction forces was investigated at varying water coverage and at different temperatures. The results indicated that in general as the water coverage increased, the Lifshitz-van der Waals component of surface energy decreased to nearly that of the bulk water, while the acid-base component also showed a decreasing trend. The Lifshitz-van der Waals component of surface energy always decreased with increase in temperature, while the acid-base properties showed contrasting trends in line with changes in surface chemistry of the sandstones, due to the change in temperature. Finally, the wetting properties arising in reservoir sandstones were related to the surface chemistry of the reservoir fluids and their interactions with the reservoir rock surface.

  15. New Perspectives on the Old Red Sandstone

    NASA Astrophysics Data System (ADS)

    Miall, Andrew D.

    The Old Red Sandstone is amongst the most distinctive and well-known stratigraphic units in the British Isles. It is mainly of Devonian age; in fact, its lower boundary was used to define the base of the Devonian until relatively recently and it was called "Old" back in the nineteenth century to distinguish it from a superficially similar succession of Triassic age named the New Red Sandstone. The Old Red Sandstone has long been known to be a non-marine syntectonic to post-tectonic deposit associated with the Caledonian Orogeny One of the most famous outcrops of the red sandstone is at Siccar Point in northeast England at one of several outcrops named "Hutton's unconformity" where it lies, with marked angularity on Silurian lithic sandstones and shales. It was at these outcrops, toward the end of the eigthteenth century that James Hutton first came to understand the meaning of angular unconformities as structures representing vast amounts of missing time during which major upheavals of the Earth's crust occurred.

  16. Quaternary alluvial deposits of Wadi Gaza in the middle of the Gaza Strip (Palestine): Facies, granulometric characteristics, and their paleoflow direction

    NASA Astrophysics Data System (ADS)

    Ubeid, Khalid Fathi

    2016-06-01

    The Quaternary rocks of the Gaza Strip mainly consist of clastic sedimentary rocks. In Wadi Gaza, the outcropping rocks consist of brownish fine-grained deposits, sandstones, and conglomerates. The deposits have been studied from a genetic point of view, and six facies have been described: (i) graded clast-supported conglomerates, (ii) cross-bedded clast-supported conglomerates, (iii) sandy matrix conglomerates, (iv) cross-laminated medium-grained sandstones, (v) graded coarse-grained sandstones, and (vi) massive sandstones. The field work observations and granulometric analysis show that the sphericity of the grains increase toward the west, where its value ranges from ∼0.64 in the east to ∼0.70 in the west. In addition, the grain forms tend to be disc shape in the east, whereas they tend to be disc-to spheroid shape in the west, and they become well rounded to well sorted toward the west. Moreover, the features, geometry, and spatial relationship among these facies suggest that the Wadi Gaza was meandering wadi fed from Beir Sheva and the Northern Negev in the southeast of Gaza Strip through Wadi Al Shallala and Wadi Sheneq and from Hebron mountains in the West Bank at the east through Wadi Al Shari'a alluvials. Within the Gaza Strip, paleocurrent data ranges from 210° to 310°, indicating a mean a paleoflow direction to the W (276°) and a median value about 275°. The sedimentary rocks in the Wadi Gaza are considered to be deposited in two periods of climate conditions: the coarse-grained rocks were deposited during the period of wet condition before 12.4 ka age, whereas the eolinite fine-grained rocks were deposited during semiarid climate conditions which are younger in age than 12.4 ka.

  17. Stratigraphy and depositional environment of nonmarine facies of Frontier Formation, Eastern Pioneer Mountains, southwestern Montana

    USGS Publications Warehouse

    Dyman, T.S.; Tysdal, R.G.

    1998-01-01

    The Upper Cretaceous Frontier Formation in the eastern Pioneer Mountains of southwestern Montana was deposited in nonmarine environments west of the Western Interior Seaway within the Cordilleran foreland basin. These rocks have been assigned to the Frontier because they contain lithologies typical of the Frontier in the region even though they are entirely nonmarine and are thicker than the correlative marine Frontier to the east. The Frontier in the eastern Pioneer Mountains is underlain by the Vaughn Member of the Blackleaf Formation, but the upper part of the Frontier has been eroded and locally is overlain by rocks of Tertiary age. Geologic mapping was conducted and four sections were measured and described to determine facies, thickness variations, and depositional environments. In the eastern Pioneer Mountains study area, the Frontier ranges in thickness from about 1200 ft (366 m) in the south to more than 3400 ft (1036 m) in the north\\. Frontier strata in the study area cannot be readily subdivided into mappable units, but two broadly-defined informal lithic units are described. The lower unit contains yellow-brown weathering siltstone, mudstone, and fine-grained quartz-rich sandstone, and is about 250 ft (76 m) thick. The upper unit is composed of yellow-brown to dark-gray siltstone and mudstone, quartz- and chert-rich sandstone, conglomeratic sandstone, and limestone, and is more than 2100 ft (640 m) thick in one measured section. The lower contact of the Frontier is placed at the top of a porcellanite bed that is associated with maroon mudstone and siltstone, limestone, and calcareous dark-gray shale in the underlying Vaughn Member of the Blackleaf Formation. The porcellanite bed directly overlies the highest maroon mudstone-siltstone bed of the upper Vaughn. The Frontier Formation in the eastern Pioneer Mountains was deposited on a broad delta plain dominated by fine-grained sediments. Sandstones exhibit characteristics of anastomosing fluvial channels

  18. Read Across Texas! 2002 Texas Reading Club Manual.

    ERIC Educational Resources Information Center

    Edgmon, Missy; Ferate-Soto, Paolo; Foley, Lelana; Hager, Tina; Heard, Adriana; Ingham, Donna; Lopez, Nohemi; McMahon, Dorothy; Meyer, Sally; Parrish, Leila; Rodriguez-Gibbs, Josefina; Moreyra-Torres, Maricela; Travis, Gayle; Welch, Willy

    The goal of the Texas Reading Club is to encourage the children of Texas to become library users and lifelong readers. This manual was created for the 2002 Texas Reading Club, a program of the Texas State Library and Archives Commission. The theme, "Read Across Texas!" invites children to explore the history, geography, and culture of Texas…

  19. Seismic Response of Carbonate Cemented Sandstones

    NASA Astrophysics Data System (ADS)

    Dutta, T.; Mukerji, T.; Mavko, G.

    2007-12-01

    This study focuses on how carbonate cementation precipitated at the key sequence stratigraphic surfaces impact the seismic impedance. Our goals are two-fold: (1) to identify the sedimentological variations within carbonate- cemented sandstones and (2) to quantify their effects on P-impedance. To accomplish this goal, we identify the relationship between carbonate cementation and key stratigraphic surfaces, such as, the incision surfaces and the flooding surfaces. Next, we use effective medium models to quantify the impact of sediment parameters on P- impedance. We find that the carbonate cemented sandstones are extremely heterogeneous in nature, even within a depth interval of 60 meter in our study area offshore Equatorial Guinea, West Africa. Their grain-size, sorting, mineralogy, clay-content, amount of cement and degree of leaching vary considerably. We identify two distinct clusters of data in the P-impedance vs. porosity plane. The carbonate cemented sandstones from the base of incision are usually associated with lower shaliness, lower porosity and higher P-impedance. On the contrary, data from the top of flooding surfaces exhibit higher shaliness, higher porosity and lower P-impedance. The contact cement model fails to predict the trend shown by the later cluster of data. The predictions using the constant cement model with 1% constant carbonate cement, and the modified stiffsand model with 15% critical porosity agree reasonably well with the data. Furthermore, we find that the modified differential effective media model with 40% percolation porosity, and Berryman's self consistent model with 20% percolation porosity fit P- impedance vs. porosity trend of the carbonated cemented sandstones. In conclusion, the carbonate cements are different than the siliciclastic cements in terms of sedimentological parameters, and the commonly used rock physics model for quartz cemented sandstones are not always suitable to predict P-impedance vs. porosity trends for the

  20. Eolian sabkha sandstones in the Nugget Sandstone (Jurassic), Vernal area, Utah

    SciTech Connect

    Schenk, C.J.; Peterson, F. )

    1991-06-01

    The Jurassic Nugget Sandstone in the Vernal, Utah, area is characterized by thick (up to 25 m) sets of cross-stratified eolian dune sandstone separated by either erosional planar bounding surfaces or thin (mostly < 3 m) sandstones interpreted as sabkha sandstones. Structures in Nugget sabkha sandstones are predominantly wavy or irregular bedding and thin, remnant sets of dune cross-strata consisting of eolian ripple and avalanche strata. The types of sedimentary structures and erosional features in Nugget sabkha sandstones indicate a close relationship between sand deposition and erosion and fluctuations in the local water table. Thin, remnant eolian dune sets are common in Nugget sabkha sandstones. The remnant sets form when dunes migrating across a sabkha are partially wetted as the water table rises slightly (on a scale of tens of centimeters); the lower part of the dune with wetted sand remains on the sabkha as the rest of the dune continues to migrate. Typically, ripple strata of the dune apron and the toes of avalanche strata are preserved in dune remnants. The avalanche strata, being slightly coarser grained, are preferentially deflated, leaving microtopography. This topography is commonly filled in with ripple strata that form as dry sand again blows across the sabkha. Stacked sets of remnant dunes separated by erosional surfaces illustrate the control of sand deposition on eolian sabkhas by the local water table.

  1. Sedimentary facies of alluvial fan deposits, Death Valley, California

    SciTech Connect

    Middleton, G.V. )

    1992-01-01

    Fans in Death Valley include both diamicts and bedded gravels. Seven facies may be recognized. The diamicts include: (1) matrix-rich, coarse wackestones; (2) thin, matrix-rich, fine wackestones, that may show grading; (3) matrix-poor, coarse packstones, transitional to wackestones. The bedded facies include: (4) weakly bedded, poorly sorted packstones or grainstones, that show patchy imbrication, and cut-and-fill structures; (5) packed, imbricated cobble lenses, generally interbedded in facies 4; (6) distinctly bedded gravels, that are better bedded, finer and better sorted, and show better imbrication than facies 4, but still do not show clear separation of sand and gravel beds; (7) backfill cross-bedded gravels. Sand beds are not seen in fan deposits. Sand is present in eolian deposits, as plane-laminated, back-eddy deposits in Death Valley Wash, and as laminated or rippled sand in the Amargosa River. The most remarkable features of the fan deposits are the very weak segregation of sand and gravel, and the complete absence of any lower flow-regime structures produced by ripples or dunes. During floods, the slope of fan and even large wash surfaces is steep enough to produce upper flow regimes. There are also very few trends in facies abundance down fans: most fans in Death Valley itself are not strongly dominated by debris flow deposits (diamicts). The facies characteristics of a given fan vary little from proximal to distal regions, but may differ strongly from the facies seen in adjacent fans. Ancient deposits that show clear segregation of gravel from cross-bedded sand beds, or strong proximal to distal facies transitions, must have been deposited in environments quite different from Death Valley.

  2. [FEATURES MORPHOLOGICAL PICTURE FACIES ORAL LIQUID IN PREGNANT].

    PubMed

    Iakovets, O V

    2015-01-01

    The features of morphological picture facies oral fluid of pregnant women with intact periodontal inflammatory diseases periodontal tissues. Results of the study were compared with the clinical picture. The features of morphological picture of the oral liquid with a healthy non-pregnant and periodontal inflammatory periodontal diseases in pregnant women. Revealed signs of inflammation markers in oral fluid facies in inflammatory processes in periodontal tissues. PMID:27089718

  3. PROBLEMS AND METHODOLOGY OF THE PETROLOGIC ANALYSIS OF COAL FACIES.

    USGS Publications Warehouse

    Chao, Edward C.T.

    1983-01-01

    This condensed synthesis gives a broad outline of the methodology of coal facies analysis, procedures for constructing sedimentation and geochemical formation curves, and micro- and macrostratigraphic analysis. The hypothetical coal bed profile has a 3-fold cycle of material characteristics. Based on studies of other similar profiles of the same coal bed, and on field studies of the sedimentary rock types and their facies interpretation, one can assume that the 3-fold subdivision is of regional significance.

  4. Delayed onset sandstone pneumoconiosis: a case report

    SciTech Connect

    Symanski, H.

    1981-01-01

    An unusual case of silicosis is described in a worker who inhaled the dust of pure silica while working in a sandstone quarry. The exposure lasted only eight years. In 1980, 45 years after exposure ceased, severe clinical manifestations of silicosis appeared for the first time. The chest X-ray showed a pneumoconiosis A 2mn/A2 Mn Cor, em, hilus, based on the International Classification of Geneva, 1958. A diagnosis of sandstone pneumoconiosis was made. The case is one further example of late-occurring disease appearing after a latency of several decades.

  5. Prediction of reservoir quality and porosity basement in sandstones of the Pakawau and Kapuni groups, Taranaki basin, New Zealand - Preliminary results

    SciTech Connect

    Bloch, S.; Helmold, K.P. )

    1990-05-01

    Vitrinite reflectance porosity and porosity permeability relationships were established in 12 wells during a preliminary investigation of arkosic sandstones of the Pakawau and Kapuni groups (Late Cretaceous through Eocene) in the Taranaki basin of New Zealand. These relationships were used in conjunction with geohistory analysis to determine the economic basement and to predict porosity and permeability in the sandstones prior to drilling. Medium- to coarse-grained Kapuni and Pakawau sandstones, at vitrinite reflectance values of 0.65-0.70% R{sub 0} and higher, are not expected to have porosities and permeabilities greater than 10% and 1 md, respectively. Results obtained from a subsequently drilled well confirmed the validity of this approach. Meaningful reservoir quality predictions can be obtained only if (1) the lithological characteristics of the sandstones are accurately predicted from facies analysis, (2) the realistic input parameters, based on seismic stratigraphy and regional geologic interpretations, are used in basin modeling, and (3) the sandstones were not affected by hydrothermal activity associated with regional volcanism.

  6. Palynostratigraphy and sedimentary facies of Middle Miocene fluvial deposits of the Amazonas Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Dino, Rodolfo; Soares, Emílio Alberto Amaral; Antonioli, Luzia; Riccomini, Claudio; Nogueira, Afonso César Rodrigues

    2012-03-01

    Palynostratigraphic and sedimentary facies analyses were made on sedimentary deposits from the left bank of the Solimões River, southwest of Manaus, State of Amazonas, Brazil. These provided the age-dating and subdivision of a post-Cretaceous stratigraphic succession in the Amazonas Basin. The Novo Remanso Formation is subdivided into upper and lower units, and delineated by discontinuous surfaces at its top and bottom. The formation consists primarily of sandstones and minor mudstones and conglomerates, reflecting fluvial channel, point bar and floodplain facies of a fluvial meandering paleosystem. Fairly well-preserved palynoflora was recovered from four palynologically productive samples collected in a local irregular concentration of gray clay deposits, rich in organic material and fossilized wood, at the top of the Novo Remanso Formation upper unit. The palynoflora is dominated by terrestrial spores and pollen grains, and is characterized by abundant angiosperm pollen grains ( Tricolpites, Grimsdalea, Perisyncolporites, Tricolporites and Malvacearumpollis). Trilete spores are almost as abundant as the angiosperm pollen, and are represented mainly by the genera Deltoidospora, Verrutriletes, and Hamulatisporis. Gymnosperm pollen is scarce. The presence of the index species Grimsdalea magnaclavata Germeraad et al. (1968) indicates that these deposits belong to the Middle Miocene homonymous palynozone (Lorente, 1986; Hoorn, 1993; Jaramillo et al., 2011). Sedimentological characteristics (poorly sorted, angular to sub-angular, fine to very-coarse quartz sands facies) are typical of the Novo Remanso Formation upper part. These are associated with a paleoflow to the NE-E and SE-E, and with an entirely lowland-derived palinofloristic content with no Andean ferns and gymnosperms representatives. All together, this suggests a cratonic origin for this Middle Miocene fluvial paleosystem, which was probably born in the Purus Arch eastern flank and areas surrounding the

  7. Fluvial architecture of the buntsandstein-facies redbeds in the middle to upper triassic (Ladinian-Norian) of the southeastern edge of the Iberian Meseta (Southern Spain)

    NASA Astrophysics Data System (ADS)

    Fernández, Juan; Dabrio, Cristino

    In the southeastern edge of the Iberian Meseta in Southern Spain, fluvial continental Buntsandstein-facies red beds of Middle to Upper Triassic (Ladinian — Norian) age unconformably overlie the folded and eroded Hercynian basement. The Betic Belts consist of an internal metamorphosed part and an external sedimentary zone containing the Triassic deposits, with the latter seam being in turn divided into the Prebetic Zone with continental to shallow marine facies and the Subbetic Zone with pelagic facies. The Buntsandstein-facies red bed series is vertically split into three main facies associations: alluvial fans and pebbly braided rivers (conglomerates and sandstones), low-sinuosity proximal and distal sandy braided rivers (sandstones and mudstones) and coastal evaporitic sabkha (mudstones, marls and gypsum). Alluvial-fan and pebbly braided river sediments occur at the base of the sequence and cover the palaeorelief of the pre-Triassic morphology. The inner fan zone is characterized by debris-flows or mud-flows, the mid fan zone is dominated by sheet floods, and the outer fan zone is governed by stream flood and stream flow passing into pebbly braided rivers in front of the fans. With transition from restricted alluvial fans to an open braidplain, the pebbly rivers soon evolve both vertically and horizontally into sandy stream networks consisting of channels and floodplains. The channel facies comprises sheet-type and ribbon-type sandstone layers. The sheets form complexes up to 15 m and more thickness due to amalgamation by multilateral coalescence and multivertical stacking of individual genetical units. In the lower part of the series, the number of channels is rather high suggesting a non-hierarchical channel pattern where high- and low-sinuosity rivers coexist. The middle portion reflects a smaller number of very large channels thus indicating an amelioration of the hierarchical pattern. The upper part consists of variegated sabkha plain mudstones and

  8. Fine-Grained Turbidites: Facies, Attributes and Process Implications

    NASA Astrophysics Data System (ADS)

    Stow, Dorrik; Omoniyi, Bayonle

    2016-04-01

    Within turbidite systems, fine-grained sediments are still the poor relation and sport several contrasting facies models linked to process of deposition. These are volumetrically the dominant facies in deepwater and, from a resource perspective, they form important marginal and tight reservoirs, and have great potential for unconventional shale gas, source rocks and seals. They are also significant hosts of metals and rare earth elements. Based on a large number of studies of modern, ancient and subsurface systems, including 1000s of metres of section logging, we define the principal genetic elements of fine-grained deepwater facies, present a new synthesis of facies models and their sedimentary attributes. The principal architectural elements include: non-channelised slope-aprons, channel-fill, channel levee and overbank, turbidite lobes, mass-transport deposits, contourite drifts, basin sheets and drapes. These comprise a variable intercalation of fine-grained facies - thin-bedded and very thin-bedded turbidites, contourites, hemipelagites and pelagites - and associated coarse-grained facies. Characteristic attributes used to discriminate between these different elements are: facies and facies associations; sand-shale ratio, sand and shale geometry and dimensions, sand connectivity; sediment texture and small-scale sedimentary structures; sediment fabric and microfabric; and small-scale vertical sequences of bed thickness. To some extent, we can relate facies and attribute characteristics to different depositional environments. We identify four distinct facies models: (a) silt-laminated mud turbidites, (b) siliciclastic mud turbidites, (c) carbonate mud turbidites, (d) disorganized silty-mud turbidites, and (e) hemiturbidites. Within the grainsize-velocity matrix turbidite plot, these all fall within the region of mean size < 0.063mm, maximum grainsize (one percentile) <0.2mm, and depositional velocity 0.1-0.5 m/s. Silt-laminated turbidites and many mud

  9. Build-and-fill sequences: How subtle paleotopography affects 3-D heterogeneity of potential reservoir facies

    USGS Publications Warehouse

    McKirahan, J.R.; Goldstein, R.H.; Franseen, E.K.

    2005-01-01

    This study analyzes the three-dimensional variability of a 20-meter-thick section of Pennsylvanian (Missourian) strata over a 600 km2 area of northeastern Kansas, USA. It hypothesizes that sea-level changes interact with subtle variations in paleotopography to influence the heterogeneity of potential reservoir systems in mixed carbonate-silidclastic systems, commonly produdng build-and-fill sequences. For this analysis, ten lithofacies were identified: (1) phylloid algal boundstone-packstone, (2) skeletal wackestone-packstone, (3) peloidal, skeletal packstone, (4) sandy, skeletal grainstone-packstone, (5) oolite grainstone-packstone, (6) Osagia-brachiopod packstone, (7) fossiliferous siltstone, (8) lenticular bedded-laminated siltstone and fine sandstone, (9) organic-rich mudstone and coal, and (10) massive mudstone. Each facies can be related to depositional environment and base-level changes to develop a sequence stratigraphy consisting of three sequence boundaries and two flooding surfaces. Within this framework, eighteen localities are used to develop a threedimensional framework of the stratigraphy and paleotopography. The studied strata illustrate the model of "build-and-fill". In this example, phylloid algal mounds produce initial relief, and many of the later carbonate and silidclastic deposits are focused into subtle paleotopographic lows, responding to factors related to energy, source, and accommodation, eventually filling the paleotopography. After initial buildup of the phylloid algal mounds, marine and nonmarine siliciclastics, with characteristics of both deltaic lobes and valley fills, were focused into low areas between mounds. After a sea-level rise, oolitic carbonates formed on highs and phylloid algal facies accumulated in lows. A shift in the source direction of siliciclastics resulted from flooding or filling of preexisting paleotopographic lows. Fine-grained silidclastics were concentrated in paleotopographic low areas and resulted in clay

  10. Fractures and stresses in Bone Spring sandstones

    SciTech Connect

    Lorenz, J.C.; Warpinski, N.R.; Sattler, A.R.; Northrop, D.A.

    1990-09-01

    This project is a collaboration between Sandia National Laboratories and Harvey E. Yates Company being conducted under the auspices of the Oil Recovery Technology Partnership. The project seeks to apply perspectives related to the effects of natural fractures, stress, and sedimentology to the simulation and production of low-permeability gas reservoirs to low-permeability oil reservoirs as typified by the Bone Spring sandstones of the Permian Basin, southeast New Mexico. This report presents the results and analysis obtained in 1989 from 233 ft of oriented core, comprehensive suite of logs, various in situ stress measurements, and detailed well tests conducted in conjunction with the drilling of two development wells. Natural fractures were observed in core and logs in the interbed carbonates, but there was no direct evidence of fractures in the sandstones. However, production tests of the sandstones indicated permeabilities and behavior typical of a dual porosity reservoir. A general northeast trend for the maximum principal horizontal stress was observed in an elastic strain recovery measurements and in strikes of drilling-induced fractures; this direction is subparallel to the principal fracture trend observed in the interbed carbonates. Many of the results presented are believed to be new information for the Bone Spring sandstones. 57 figs., 18 tabs.

  11. Eccentricity and precession forced cyclicity in the Upper Silurian Williamsport Sandstone Member of the Wills Creek Formation

    SciTech Connect

    Shelton, S.D.; Anderson, E.J. . Dept. of Geology)

    1993-03-01

    The Williamsport Sandstone Member, located at the base of the Wills Creek Formation, contains a complete 5th order sequence, traceable for more than 100 kilometers. This 5th order sequence is initiated with a massive iron-rich sandstone unit. The upper iron-rich sand of the Williamsport Member marks the beginning of the next 5th order sequence. The first 5th order rock cycle, interpreted as the product of the 100 k.y. Milankovitch eccentricity cycle, is divisible into five meter-scale 6th order precessional cycles (PACs). At Cedar Cliff, Maryland, the lithology of each of the five 6th order cycles is distinct. The first cycle (.8m thick) is a massive iron-rich sandstone. The second cycle (.75m thick) is an argillaceous nodular micrite. The third cycle (.75m thick) consists totally of thin-bedded quartz sandstone. The fourth cycle (2m thick) is represented by bedded limestones that thicken upward. The fifth cycle (.6m thick) is very thin-bedded to nodular limestone. This 5th order sequence and most of its internal cyclic elements can be traced over 100 kilometers to Mount Union, Pennsylvania where its facies are largely non-marine. Detailed correlation of these 6th order cycles reveals that the uppermost PAC is missing at Cumberland and Mount Union. At these localities, the prominent iron bed of the next 5th order sequence rests unconformably on the fourth PAC in the sequence. The fifth 6th order cycle was either not deposited or removed by erosion at these proximal localities. The laterally traceable hierarchic cyclic structure in the Williamsport Sandstone is consistent with the Milankovitch forcing model and provides a detailed stratigraphic basis for analysis of lateral patterns of cyclic accumulation in the late Silurian of the central Appalachians.

  12. Emplacement of sandstone intrusions during contractional tectonics

    NASA Astrophysics Data System (ADS)

    Palladino, Giuseppe; Grippa, Antonio; Bureau, Denis; Alsop, G. Ian; Hurst, Andrew

    2016-08-01

    Sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure. However, the contribution provided by horizontal compressive stress to the build-up in overpressure, and the resulting emplacement of sand injection complexes, is still to be substantiated by robust field observations. An opportunity to address this issue occurs in Central California where a large volume of sandstone intrusions record regionally-persistent supra-lithostatic pore-pressure. Detailed fieldwork allows sandstone-filled thrusts to be recognized and, for the first time, permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the Great Valley Basin. Fluidized sand was extensively injected along thrust surfaces, and also fills local dilatant cavities linked to thrusting. The main aims of this paper are to provide detailed descriptions of the newly recognized syn-tectonic injections, and describe detailed cross-cutting relationships with earlier sandstone injection complexes in the study area. Finally, an evolutionary model consisting of three phases of sand injection is provided. In this model, sand injection is linked to contractional tectonic episodes affecting the western side of the Great Valley Basin during the Early-Middle Cenozoic. This study demonstrates that sand injections, driven by fluid overpressure, may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation. It is shown that different generations of sand injection can develop in the same area under the control of different stress regimes, linked to the evolving mountain chain.

  13. Late tertiary and quaternary fluvial deposits in the Mesilla and Hueco bolsons, El Paso area, Texas

    NASA Astrophysics Data System (ADS)

    Stuart, Charles J.; Willingham, Daniel L.

    1984-03-01

    The late Tertiary to Quaternary Fort Hancock and Camp Rice Formations fill several extensional basins of the southern Rio Grande Rift. Interior drainage and central playa lakes characterize most of these rift basins. However, sedimentation in two basins located in the central part of the southern rift, the Mesilla and Hueco bolsons, was also greatly influenced by a northern segment of the ancestral Rio Grande river system. During the late Pliocene, a large-scale stream system entered the north end of the Mesilla bolson and deposited a south-sloping fluvial plain that overwhelmed playa lake and bolson-margin areas. The fluvial plain subsequently advanced across the eastern or southeastern margins of the Mesilla bolson then inundated a playa lake in the adjacent Hueco bolson. The Fort Hancock Formation was deposited during fluvial inundation of the bolsons. Four lithofacies of the Fort Hancock Formation are recognized: claystone, mudstone and sandstone, channelized sandstone, and conglomerate. The conglomerate and claystone facies were deposited in bolson-margin and playa depositional environments, respectively. The channelized sandstone facies formed the proximal fluvial plain of the ancestral Rio Grande system. The mudstone and sandstone facies formed in both playa-margin and distal fluvial-plain environments. By the middle Pleistocene, a major drainage basin south of the Hueco bolson, which formed the southern segment of the ancestral Rio Grande system, extended northward into the Hueco and Mesilla bolsons. At this time, the Rio Grande system was entirely integrated from southern Colorado to the Gulf of Mexico. Pebbly, coarse sand transported through this channel system formed the middle Pleistocene Camp Rice Formation.

  14. Facies comparison of autochthonous and allochthonous Permian and Triassic units, north-central Brooks Range, Alaska

    SciTech Connect

    Adams, K.E.

    1985-04-01

    Eight stratigraphic sections of Permian and Triassic rocks have been studied over a 30 km by 150 km area in the Endicott and Philip Smith Mountains of the central Brooks Range. Six of the sections are located on the Endicott Mountains allochthon, and the remaining two are parautochthonous columns in the Mount Doonerak area. The sections record a facies transition between the autochthonous Sadlerochit Group and Shublik Formation of the northeastern Brooks Range and the characteristically siliceous rocks of the allochthonous Siksikpuk and Otuk formations of the western Brooks Range. Laterally continuous and bioturbated beds of fine-grained sandstone, siltstone, and shale dominantly compose the Permian sequence, whereas the Triassic rocks consist of black shales, thin rhythmically bedded siliceous mudstones, and fossiliferous limestones. When the allochthonous sections are restored to a position south of the Mount Doonerak area, a general shallowing trend from southwest to northwest becomes evident within the reconstructed marine basin. To the south and west, the Permian sediments show a marked increase in silica content, with the occurrence of barite and a corresponding decrease in the thickness of the basal, coarser grained clastics. The Triassic formations also document an increase in silica and the presence of barite to the south and west, while becoming significantly sooty and phosphatic to the north and east. Ongoing petrographic and micropaleontologic studies of the field data will clarify these general paleogeographic relationships.

  15. Basin Dynamics and Sedimentary Infilling of Miocene Sandstone Reservoir Systems In Eastern Tunisian African Margin

    NASA Astrophysics Data System (ADS)

    Bédir, Mourad; Khomsi, Sami

    2015-04-01

    Most of hydrocarbon accumulations and aquifers within the Cap Bon, Gulf of Hammamet and Sahel basins in eastern tunisian foreland are reservoired within the Upper Miocene Birsa and Saouaf sandstones and shales Formations. In the gulf of Hammamet, these sandstones constitutes oil and gas fields and are exploited on anticline highs and described as varying from shoreface to shallow marine and typically exhibit excellent reservoir quality of 30% to 35% porosity and good permeability from 500 to 1100 md. In addition, the fracturing of faults enhanced the reservoir quality potential. In contrary, the same hydrocarbon reservoirs are important hydrogeologic ones in the Cap Bon and Sahel basins with huge amount of hundred millions of cubic meters of water only partially exploited. Integrated wire line logging correlations, seismic sequence stratigraphic, tectonics and outcrop geologic analogue studies had permitted to highlight the basin structuring and sedimentary environments of sequence deposits infilling of the reservoir distribution between high platforms to subsiding graben and syncline basins bounded by deep-seated transtensive and transpressive flower faults. Seven third order sequence deposits limited by downlap prograding and onlap/toplap aggrading/retrograding system tracts extend along the eastern margin around the three basins by facies and thickness variances. System tracts exhibit around high horst and graben a channelized and levee infillings extending from 100 meters to more than a kilometer of width. They present a stacked single story and multistory channels types showing space lateral and vertical migrations along NE-SW, E-W and N-S directions. Paleogeographic depositional reservoir fair maps distribution highlight deltaic horst domain with floodplain and incised valley of fluvial amalgamed and braided sandstones distributary channels that occupy the high folded horsts. Whereas folded horst-graben and syncline borders domain of Shelf prodelta are

  16. Putative domal microbial structures in fluvial siliciclastic facies of the Mesoproterozoic (1.09 Ga) Copper Harbor Conglomerate, Upper Peninsula of Michigan, USA.

    PubMed

    Wilmeth, Dylan T; Dornbos, Stephen Q; Isbell, John L; Czaja, Andrew D

    2014-01-01

    The Copper Harbor Conglomerate is a Mesoproterozoic (1.09 Ga) freshwater sedimentary sequence that outcrops in the Upper Peninsula of Michigan. The formation was deposited during infilling of the failed Midcontinent Rift and contains fluvial, lacustrine, and alluvial fan facies. This study describes and analyzes the formation of small domal structures preserved in fluvial sandstone facies within the lower portion of the formation. These domal structures range from millimeters to several centimeters in diameter and height, and are preserved in convex epirelief on fine-grained sandstone beds. The structures have a pustulose texture and a patchy distribution on bedding planes. Slabs containing the structures were collected in the field and analyzed in the laboratory through inspection of cut slabs, petrographic thin sections, X-radiographs, and RAMAN spectroscopy. Results of these analyses reveal that the domal structures often contain weak, wavy horizontal bedding and laminae, and lack any vertical structures. These results support a biogenic origin of the domal structures instead of through abiogenic processes such as loading, sand volcanoes, or adhesion warts. These structures are akin to what were traditionally labeled as 'sand stromatolites', but are now known as 'domal sand structures'. Along with previous descriptions of carbonate stromatolites, organic-rich paleosols, and microbial sand structures, our findings provide further evidence that mat-forming microbial communities thrived in the late Mesoproterozoic freshwater systems of the Midcontinent Rift. PMID:24325309

  17. Reservoir heterogeneity in Carboniferous sandstone of the Black Warrior basin. Final report

    SciTech Connect

    Kugler, R.L.; Pashin, J.C.; Carroll, R.E.; Irvin, G.D.; Moore, H.E.

    1994-04-01

    Although oil production in the Black Warrior basin of Alabama is declining, additional oil may be produced through improved recovery strategies, such as waterflooding, chemical injection, strategic well placement, and infill drilling. High-quality characterization of reservoirs in the Black Warrior basin is necessary to utilize advanced technology to recover additional oil and to avoid premature abandonment of fields. This report documents controls on the distribution and producibility of oil from heterogeneous Carboniferous reservoirs in the Black Warrior basin of Alabama. The first part of the report summarizes the structural and depositional evolution of the Black Warrior basin and establishes the geochemical characteristics of hydrocarbon source rocks and oil in the basin. This second part characterizes facies heterogeneity and petrologic and petrophysical properties of Carter and Millerella sandstone reservoirs. This is followed by a summary of oil production in the Black Warrior basin and an evaluation of seven improved-recovery projects in Alabama. In the final part, controls on the producibility of oil from sandstone reservoirs are discussed in terms of a scale-dependent heterogeneity classification.

  18. Reservoir heterogeneity in carboniferous sandstone of the Black Warrior basin. Final report

    SciTech Connect

    Kugler, R.L.; Pashin, J.C.; Carroll, R.E.; Irvin, G.D.; Moore, H.E.

    1994-06-01

    Although oil production in the Black Warrior basin of Alabama is declining, additional oil may be produced through improved recovery strategies, such as waterflooding, chemical injection, strategic well placement, and infill drilling. High-quality characterization of reservoirs in the Black Warrior basin is necessary to utilize advanced technology to recover additional oil and to avoid premature abandonment of fields. This report documents controls on the distribution and producibility of oil from heterogeneous Carboniferous reservoirs in the Black Warrior basin of Alabama. The first part of the report summarizes the structural and depositional evolution of the Black Warrior basin and establishes the geochemical characteristics of hydrocarbon source rocks and oil in the basin. This second part characterizes facies heterogeneity and petrologic and petrophysical properties of Carter and Millerella sandstone reservoirs. This is followed by a summary of oil production in the Black Warrior basin and an evaluation of seven improved-recovery projects in Alabama. In the final part, controls on the producibility of oil from sandstone reservoirs are discussed in terms of a scale-dependent heterogeneity classification.

  19. Facies-controlled reservoir properties in ramp-fan and slope-apron deposits, Miocene Puente Formation, Los Angeles basin

    SciTech Connect

    Lyons, K.T.; Geving, R.L.; Suchecki, R.K.

    1989-03-01

    The Miocene Puente Formation in outcrops of the eastern Los Angeles basin is interpreted as a succession of slope-apron and ramp-fan deposits that accumulated in a prism-rise wedge. The principal depositional components of this dominantly base-of-slope and ramp system are ramp-fan channels and lobes, and slope-channel and slope-apron channel/interchannel deposits. Facies-specific textural, compositional, and diagenetic attributes observed in thin section assist in the classification of depositional facies. Specifically, occurrence of carbonate cement, clay mineralogy, and abundance of organic material vary as a function of component facies architecture of the depositional system. Slope and ramp-fan channel-fill sandstones are characterized by pervasive carbonate cements, including poikilotopic and fine-grained calcite, fine-grained and baroque dolomite, and minor siderite. Diagenetic clays predate carbonate cements, and dolomite predates coarser, void-filling calcite. Ramp-fan lobe and interchannel deposits are carbonate free but are rich in detrital clay and organic matter. Diagenetic clays include mixed-layer illite/smectite and kaolinite. Sediments deposited in slope-apron channel fill are virtually cement free except for small amounts of authigenic illite/smectite. Slope-apron interchannel deposits are characterized by high content of organic matter and clay-rich matrix. Potential reservoir characteristics, such as grain size, sorting, and abundance of depositional clay matrix, are related to the primary sedimentary properties of depositional architectural components in the ramp-fan and slope-apron system. Additional diagenetic modifications, without consideration of compaction, were controlled by precipitation reactions associated with fluid flow along pathways related to the depositional architectural framework.

  20. Searching for facies indicators in ground penetrating radar data

    NASA Astrophysics Data System (ADS)

    Moysey, S.; Knight, R.; Brunner, D.; Endres, T.

    2004-05-01

    Developing an accurate conceptual model of subsurface spatial heterogeneity is a critical step in producing reliable predictions of hydrogeologic processes. One approach to this problem is to divide the subsurface into distinct geologic units or facies. Obtaining a realistic facies model in complex geologic environments, however, can be impossible using well-based data alone. Therefore, alternative data that have the potential to sample large volumes of the subsurface, such as ground penetrating radar (GPR) reflection images, can be valuable tools to aid in facies characterization. GPR images provide a record of the interactions between an electromagnetic wave and subsurface heterogeneity. Due to the complexity of the processes encoded in this image, it cannot be considered a direct `image' of the subsurface. As a result, building a facies model from GPR data typically requires expert interpretation. Manual interpretations have the disadvantages of being highly labor intensive, subjective, and qualitative. Unsupervised classification techniques, such as clustering algorithms and neural networks, have the potential to overcome these disadvantages. It is currently unclear, however, whether these automated approaches can be used to obtain facies classifications that are consistent with expert interpretations or geologic reality. In particular, it is uncertain whether there are key elements, or attributes, of a radar image that can be used as primary indicators for different facies. To address these questions, we compare the facies classifications obtained by expert interpretation to those obtained using K-means clustering for GPR data obtained from the Whiteman's Creek watershed in southern Ontario, Canada. The automated classification was performed once using instantaneous attributes, such as envelope, phase, and frequency, and again using structural attributes, which are related to the geometric arrangement of reflectors in the subsurface. In this example, the

  1. Diagenesis and cement fabric of gas reservoirs in the Oligocene Vicksburg Formation, McAllen Ranch Field, Hidalgo County, Texas

    SciTech Connect

    Langford, R.P.; Lynch, F.L. )

    1990-09-01

    McAllen Ranch field produces natural gas from 12 deep, overpressured sandstone packages, each interpreted to be the deposit of a prograding shelf-edge delta. One hundred and sixty thin sections from 350 ft of core were petrographically described. The sandstones are feldspathic litharenites containing subequal proportions of volcanic rock fragments (VRF), feldspar, and quartz grains. Grain size ranges from very fine to coarse sand. Porosity is mostly secondary, having formed through dissolution of VRF and feldspar grains. There are four major diagenetic facies (portions of core that can be grouped by the predominance of one diagenetic cement and similar appearance in hand specimen): (1) calcite cemented; (2) chlorite cemented, tight; (3) chlorite cemented, porous; and (4) quartz overgrowths, porous. The calcite-cemented facies predominates in very fine grained sandstones and siltstones and encroaches into adjoining sandstones irrespective of grain size. Sparry calcite filled all available pores and replaced some feldspar. Core permeabilities are generally less than 0.01 md, and porosities range from 7 to 15%. Authigenic clay (predominantly chlorite) generally cements sands intermediate in grain size between those cemented by calcite and those cemented by quartz. Two types of diagenetic clay fabric are interbedded, forming distinct alternating bands 0.1 in. to 3 ft thick. Gray, tightly chlorite-cemented bands are macroscopically and microscopically distinct from green, porous chlorite-cemented bands. In the tightly chlorite-cemented facies, permeabilities are less than 0.3 md, and porosities range from 8 to 16%. Small plates of chlorite fill interparticle pores, and secondary pores are rare. In the porous chlorite-cemented facies, dissolution of framework grains and chlorite cement increased porosity, and a second chlorite cement was precipitated. Core permeability ranges from 0.1 to 1 md, and porosities range from 15 to 20%.

  2. Lower Eocene carbonate facies of Egypt: paleogeographic and tectonic implications

    SciTech Connect

    Garrison, R.E.

    1983-03-01

    The northern Arabo-Nubian craton witnessed a major Late Cretaceous-early Tertiary marine transgression that culminated in the deposition of widespread shelf-sea carbonates during Early Eocene (Ypresian) time. Outer shelf facies characterize exposures in central Egypt (Assiut, Luxor, Kharga), and are composed primarily of rhythmically interbedded chalk and micritic limestone with minor intercalated marine hardgrounds. To the south (Kurkur-Dungul), these fine-grained lithologies give way to inner shelf foraminiferal wackestones and grainstones, typical Tethyan Nummulitic facies. Missing in southern Egypt is the restricted dolomitic evaporitic facies predicted by the Irwin model and observed in the lower Eocene of the Sirte basin to the west and the Arabian Platform to the east. Comparing the areal distribution of these lower Eocene carbonates to coeval facies developed across the remained of northern Africa and Arabia reveals the presence of a broad marine embayment which extended through central and eastern Egypt into northern Sudan during Ypresian time. The widespread subsidence that resulted in the development of this features may have been an effect of regional crustal attenuation preceding the rifting of the Red Sea. Concomitant with this regional subsidence were localized uplift and extensional block faulting in the vicinity of the incipient Red Sea rift (the Safaga-Quseir coastal plain). Here, lower Eocene carbonate facies are indicative of shallow water platforms developed on horst blocks, and deeper water, turbidite-fed basins in intervening grabens.

  3. Eruption processes and facies architecture of the Orion Central kimberlite volcanic complex, Fort à la Corne, Saskatchewan; kimberlite mass flow deposits in a sedimentary basin

    NASA Astrophysics Data System (ADS)

    Pittari, A.; Cas, R. A. F.; Lefebvre, N.; Robey, J.; Kurszlaukis, S.; Webb, K.

    2008-06-01

    The Fort à la Corne diamondiferous kimberlite field consists of at least 70 bodies of volcaniclastic kimberlite, hosted within a contemporaneous non-volcanic sedimentary succession. This study of the three-dimensional stratigraphy and facies architecture across the Orion Central kimberlite volcanic complex highlights the variations in upper and extra-vent processes. The sedimentary succession consists of continental to marginal marine quartz sandstones and mudstones, overlain by marginal to deep marine dark mudstone and muddy sandstones and siltstones. Relatively thin conformable volcaniclastic kimberlite packages are interbedded throughout the host rock stratigraphy. Extremely thick (up to at least 211 m thick) discordant to concordant, volcaniclastic packages/series, infill at least three elongate northwest-trending craters (145A, 145B and 219 craters), and contain laterally equivalent conformable extra-crater deposits bound by marine mudstones, indicative of a prevailing dominantly marine environment. The volcaniclastic deposits within the 145A and 145B craters, respectively, are separated by a considerable hiatus, whereas the deposit infilling the 219 crater was formed around the same time as 145B crater deposit. Multiple depositional units of massive to stratified, olivine-rich sand- to pebble-sized volcaniclastic facies infill craters and were emplaced by megaturbidite pulses fed by crystal-rich eruption fountains, which interacted with the crater relief. Stacked, normally graded, thick to very thick bedded matrix-supported olivine-rich facies characterized by brief depositional breaks between some beds represent syn- to post-eruptive turbidite pulses associated with the early eruptive event in the 145A crater. Thin layers of light grey kimberlitic mudstone underlie, or occur near the base of and above the main volcaniclastic packages associated with the 145B and 219 eruptions. Crater-infilling volcaniclastic deposits were later reworked by storm induced

  4. Preservation of anomalously high porosity in deeply buried sandstones by grain-coating chlorite: Examples from the Norwegian Continental Shelf

    SciTech Connect

    Ehrenberg, S.N. )

    1993-07-01

    Five Lower to Middle Jurassic sandstone reservoirs from the Norwegian sector provide examples of deep porosity preservation caused by grain-coating, authigenic chlorite. Wide porosity variations in clean sandstones correlate with an abundance of grain-coating chlorite and consequent inhibition of quarts cementation. Maximum porosities tend to decrease with increasing depth but generally are 10-15% higher than would be predicted from regional trends of mean porosity vs. depth. It is proposed in this paper that the high chlorite content of the porous zones reflects syndepositional concentration of Fe-rich marine clays analogous to minerals of the modern verdine facies. Fe-clay mineralization would have been localized where Fe-rich river water was discharged into the sea. The syndepositional clays were transformed during burial diagenesis into grain coatings of radially oriented chlorite crystals. Petrographic relationships indicate that these coatings grew mainly before the beginning of quartz cementation and feldspar grain dissolution (probably within the first 2 km of burial) but after grain contacts had become adjusted by mechanical compaction. The Norwegian examples demonstrate that a wide range of nearshore marine sand-body types is susceptible to chlorite mineralization. The distribution of anomalous porosity and the proportion of the net sand affected depend upon sedimentary facies architecture and the pattern of discharge of Fe-rich river water during sand deposition. This phenomenon can be critically important for hydrocarbon exploration because it can provide good reservoir quality at depths far below the [open quotes]economic basement[close quotes] originally defined on the basis of sandstones lacking chlorite coatings. 58 refs., 25 figs., 1 tab.

  5. Reservoir uncertainty, Precambrian topography, and carbon sequestration in the Mt. Simon Sandstone, Illinois Basin

    USGS Publications Warehouse

    Leetaru, H.E.; McBride, J.H.

    2009-01-01

    Sequestration sites are evaluated by studying the local geological structure and confirming the presence of both a reservoir facies and an impermeable seal not breached by significant faulting. The Cambrian Mt. Simon Sandstone is a blanket sandstone that underlies large parts of Midwest United States and is this region's most significant carbon sequestration reservoir. An assessment of the geological structure of any Mt. Simon sequestration site must also include knowledge of the paleotopography prior to deposition. Understanding Precambrian paleotopography is critical in estimating reservoir thickness and quality. Regional outcrop and borehole mapping of the Mt. Simon in conjunction with mapping seismic reflection data can facilitate the prediction of basement highs. Any potential site must, at the minimum, have seismic reflection data, calibrated with drill-hole information, to evaluate the presence of Precambrian topography and alleviate some of the uncertainty surrounding the thickness or possible absence of the Mt. Simon at a particular sequestration site. The Mt. Simon is thought to commonly overlie Precambrian basement granitic or rhyolitic rocks. In places, at least about 549 m (1800 ft) of topographic relief on the top of the basement surface prior to Mt. Simon deposition was observed. The Mt. Simon reservoir sandstone is thin or not present where basement is topographically high, whereas the low areas can have thick Mt. Simon. The paleotopography on the basement and its correlation to Mt. Simon thickness have been observed at both outcrops and in the subsurface from the states of Illinois, Ohio, Wisconsin, and Missouri. ?? 2009. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  6. Sedimentology, diagenesis, and trapping style, Chesterian Tar Springs sandstone at Inman Field, Gallatin County, Illinois

    SciTech Connect

    Morse, D.G.

    1996-09-01

    The Tar Springs Sandstone in southern Illinois is often over-looked as a pay, yet it can be a prolific producer. The Inman Field, discovered in 1940, produces from several cyclic Chesterian sandstones from structural-stratigraphic traps in the Wabash Valley Fault System of southeastern Illinois. The oil was sourced from the Devonian New Albany Shale and apparently migrated vertically along the Wabash Valley faults to its present location, thus charging many of the Chesterian and lower Pennsylvanian sands in the field. The Tar Springs Sandstone produces from stacked distributary channel sand reservoirs up to 125 feet thick which have cut up to 40 feet into laterally equivalent non-reservoir, delta-fringe facies and the underlying Glen Dean Limestone. The reservoir sands are well-sorted, fine- to medium-grained quartz arenites with less than 5% feldspar and chert. Quartz grains have quartz overgrowths. Feldspar grains are clouded in thin-section and show pronounced etching and dissolution in SEM. Diagenetic kaolinite and small amounts of illite and magnesium-rich chlorite occur in intergranular pores. Sparry, iron-rich dolomite or ankerite that fills pores in irregular millimeter-size patches, occupies up to 10% of the reservoir rock. Typical reservoir porosity ranges from 16 to 19 percent and permeability ranges from 60 to 700 md. By contrast non-reservoir delta-fringe sands typically have porosities of 6 to 12 percent and permeabilities of 1 to 20 md. Delta-fringe Tar Springs shales act as impermeable lateral and vertical seals, aiding in stratigraphic trapping.

  7. Earthquake history of Texas

    USGS Publications Warehouse

    von Hake, C. A.

    1977-01-01

    Seventeen earthquakes, intensity V or greater, have centered in Texas since 1882, when the first shock was reported. The strongest earthquake, a maximum intensity VIII, was in western Texas in 1931 and was felt over 1 165 000 km 2. Three shocks in the Panhandle region in 1925, 1936, and 1943 were widely felt. 

  8. Fireball Over Texas

    NASA Video Gallery

    Video of the fireball seen over Texas this morning (12/7/12); it was taken by a NASA camera located near Mayhill, New Mexico. It is very unusual for us to see a meteor all the way across Texas. The...

  9. Delineation of geological facies from poorly differentiated data

    SciTech Connect

    Wohlberg, Brendt; Tartakovsky, Daniel

    2008-01-01

    The ability to delineate geologic facies and to estima.te their properties from sparse data is essential for modeling physical and biochemical processes occurring in the 'ubsurface. If such data are poorly differentiated, this challcnrring task is complicated further by the absence of a clear distinction between different hydrofacies even at locations where data. are available. vVe consider three alt mative approaches for analysis of poorly differentiated data: a k-means clU!:iterinrr algorithm, an expectation-maximization algorithm, and a minimum-variance algorithm. Two distinct synthetically generated geological settings are used to r:tnalyze the ability of these algorithmti to as ign accurately the membership of such data in a given geologic facies. On average, the minimum-variance algorithm provides a more robust p rformance than its two counterparts and when combined with a nearest-neighbor algorithm, it also yields the most accurate reconstruction of the boundaries between the facies.

  10. Jonah field, sublette county, Wyoming: Gas production from overpressured Upper Cretaceous Lance sandstones of the Green River basin

    USGS Publications Warehouse

    Montgomery, S.L.; Robinson, J.W.

    1997-01-01

    Jonah field, located in the northwestern Green River basin, Wyoming, produces gas from overpressured fluvial channel sandstones of the Upper Cretaceous Lance Formation. Reservoirs exist in isolated and amalgamated channel facies 10-100 ft (3-30 m) thick and 150-4000 ft (45-1210 m) wide, deposited by meandering and braided streams. Compositional and paleocurrent studies indicate these streams flowed eastward and had their source area in highlands associated with the Wyoming-Idaho thrust belt to the west. Productive sandstones at Jonah have been divided into five pay intervals, only one of which (Jonah interval) displays continuity across most of the field. Porosities in clean, productive sandstones range from 8 to 12%, with core permeabilities of .01-0.9 md (millidarcys) and in-situ permeabilities as low as 3-20 ??d (microdarcys), as determined by pressure buildup analyses. Structurally, the field is bounded by faults that have partly controlled the level of overpressuring. This level is 2500 ft (758 m) higher at Jonah field than in surrounding parts of the basin, extending to the top part of the Lance Formation. The field was discovered in 1975, but only in the 1990s did the area become fully commercial, due to improvements in fracture stimulation techniques. Recent advances in this area have further increased recoverable reserves and serve as a potential example for future development of tight gas sands elsewhere in the Rocky Mountain region.

  11. Madison Group (Mississippian) reservoir facies of Williston Basin, North Dakota

    SciTech Connect

    Lindsay, R.F.

    1985-02-01

    Twenty-seven oil fields producing from the Mission Canyon Limestone and Charles Formation (Madison Group) were studied: 1) along the eastern basin margin (Bluell, Sherwood, Mohall, Glenburn, Haas, and Chola fields), 2) northeast of Nesson anticline (Foothills, North Black Slough, South Black Slough, Rival, Lignite, and Flaxton), 3) along Nesson anticline (North Tioga, Tioga, Beaver Lodge, Capa, Hoffland, Charlson, Hawkeye, Blue Buttes, Antelope, and Clear Creek), and 4) south of the basin center (Lone Butte, Little Knife, Big Stick, Fryburg, and Medora). Mission Canyon reservoirs along the eastern margin are in several shoaling-upward carbonate to anhydrite cycles of pisolitic packstone or grainstone buildups. South of the basin center, only a single shoaling-upward sequence is present, with dolomitized, mostly restructed-marine skeletal wackstone to pelletal wackstone or packstone reservoir facies. Nesson anticline, between these 2 areas, contains a single shoaling-upward sequence without an anhydrite cap. In northern Nesson anticline, Mission Canyon reservoir facies are oolitic-pisolitic, intraclastic wackestone or grainstone buildups or open-marine skeletal packstone or grainstone. Both limestones and dolostones are productive in southern Nesson anticline. Limestone reservoir facies are transitional, open to restricted-marine slightly intraclastic, skeletal wackestone or packstone facies. Dolostone reservoir facies are restricted-marine mudstone to skeletal mudstone and pelletal wackestone or packstone. Northeast of the Nesson anticline, production is from oolitic to pisolitic packstone or grainstone buildups in the Rival subinterval and from restricted-marine, dolomitized spiculitic mudstone in the Midale subinterval (base of Charles Formation). In the northern Nesson anticline, Rival reservoir facies are offshore open to restricted-marine, skeletal, intraclastic, pelletal wackestone and/or packstones.

  12. A locally adaptive kernel regression method for facies delineation

    NASA Astrophysics Data System (ADS)

    Fernàndez-Garcia, D.; Barahona-Palomo, M.; Henri, C. V.; Sanchez-Vila, X.

    2015-12-01

    Facies delineation is defined as the separation of geological units with distinct intrinsic characteristics (grain size, hydraulic conductivity, mineralogical composition). A major challenge in this area stems from the fact that only a few scattered pieces of hydrogeological information are available to delineate geological facies. Several methods to delineate facies are available in the literature, ranging from those based only on existing hard data, to those including secondary data or external knowledge about sedimentological patterns. This paper describes a methodology to use kernel regression methods as an effective tool for facies delineation. The method uses both the spatial and the actual sampled values to produce, for each individual hard data point, a locally adaptive steering kernel function, self-adjusting the principal directions of the local anisotropic kernels to the direction of highest local spatial correlation. The method is shown to outperform the nearest neighbor classification method in a number of synthetic aquifers whenever the available number of hard data is small and randomly distributed in space. In the case of exhaustive sampling, the steering kernel regression method converges to the true solution. Simulations ran in a suite of synthetic examples are used to explore the selection of kernel parameters in typical field settings. It is shown that, in practice, a rule of thumb can be used to obtain suboptimal results. The performance of the method is demonstrated to significantly improve when external information regarding facies proportions is incorporated. Remarkably, the method allows for a reasonable reconstruction of the facies connectivity patterns, shown in terms of breakthrough curves performance.

  13. Microfacies and depositional environment of the Word Formation (Permian) Glass Mountains, Texas

    SciTech Connect

    Rathjen, J.D. . Dept. of Geological Sciences)

    1993-02-01

    The Word Formation (Permian) crops out in the Glass Mountains of West Texas. The Word is composed of clastics in the southwest, carbonates in the northeast, and a transitional zone of alternating carbonates and clastics separating the two extreme facies. Sediment thickness ranges from 457 meters in the southwest to 91 meters in the northeast. Measured sections and petrographic data have identified six microfacies from the transitional and eastern facies of the Word. These are southwest to northeast: (1) Peloidal Packstones, (2) Bioclastic Wackestones/Packstones, (3) Whole Fossil Wackestones/Packstones, (4) Bioturbated Wackestones, (5) Fusulinid-Crinoid Packstones, and from the eastern facies, (6) Dolostones. Petrographic data indicate that a shallow water lagoonal environment existed in the southwest. This lagoonal environment grades into a more fossiliferous normal marine environment toward the northeast. In the northeast, a very shallow water shelf environment existed which was periodically subaerially exposed, dolomitizing the sediments.

  14. True triaxial testing of Castlegate sandstone.

    SciTech Connect

    Ingraham, M. D.; Holcomb, David Joseph; Issen, Kathleen A.

    2010-03-01

    Deformation bands in high porosity sandstone are an important geological feature for geologists and petroleum engineers; however, their formation is not fully understood. Axisymmetric compression, the common test for this material, is not sufficient to fully evaluate localization criteria. This study seeks to investigate the influence of the second principal stress on the failure and the formation of deformation bands in Castlegate sandstone. Experimental results from tests run in the axisymmetric compression stress state, as well as a stress state between axisymmetric compression and pure shear will be presented. Samples are tested using a custom triaxial testing rig at Sandia National Laboratories capable of applying stresses up to 400 MPa. Acoustic emissions are used to locate deformation bands should they not be visible on the specimen exterior. It is suspected that the second invariant of stress has a strong contribution to the failure mode and band formation. These results could have significant bearing on petroleum extraction as well as carbon dioxide sequestration.

  15. Preserving Native American petroglyphs on porous sandstone

    USGS Publications Warehouse

    Grisafe, D.A.

    1996-01-01

    A new method of chemical treatment is proposed to improve the durability of soft, porous sandstones onto which Native American petroglyphs have been carved. Cores of Dakota Sandstone from the Faris Cave site, located along the Smoky Hill River in Ellsworth County, Kansas, were treated with ethyl silicate dissolved in a lightweight ketone carrier, and some cores were subsequently treated with a combination of ethyl silicate and silane using the same solvent. Measurement of the resulting physical properties, when compared to untreated cores, indicate the treatments substantially increased the compressive strength and freeze-thaw resistance of the stone without discoloring the stone or completely sealing the pore system. The treatment increases the durability of the stone and provides a method for preserving the petroglyphs at the site. After treating test panels at the site, the petroglyphs were treated in like manner.

  16. Radionuclide transport in sandstones with WIPP brine

    SciTech Connect

    Weed, H.C.; Bazan, F.; Fontanilla, J.; Garrison, J.; Rego, J.; Winslow, A.M.

    1981-02-01

    Retardation factors (R) have been measured for the transport of /sup 3/H, /sup 95m/Tc, and /sup 85/Sr in WIPP brine using St. Peter, Berea, Kayenta, and San Felipe sandstone cores. If tritium is assumed to have R=1, /sup 95m/Tc has R=1.0 to 1.3 and therefore is essentially not retarded. Strontium-85 has R = 1.0 to 1.3 on St. Peter, Berea, and Kayenta, but R=3 on San Felipe. This is attributed to sorption on the matrix material of San Felipe, which has 45 volume % matrix compared with 1 to 10 volume % for the others. Retardation factors (R/sub s/) for /sup 85/Sr calculated from static sorption measurements are unity for all the sandstones. Therefore, the static and transport results for /sup 85/Sr disagree in the case of San Felipe, but agree for St. Peter, Berea, and Kayenta.

  17. Control On Fluid Flow Properties In Sandstone: Interactions Between Diagenesis Processes And Fracture Corridors

    NASA Astrophysics Data System (ADS)

    Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca

    2016-04-01

    During the development of a fault zone, processes occur at different scales: secondary faults and fractures development in the damage zone while "diagenetic" processes, i.e: fluid rock interaction at the grains size scale, contribute to modify the matrix features. Spatial distribution of these processes is clearly controlled by microstructural transformations induced by fractured corridors and their location. Understanding flowing properties in the associated damage zone contributes to the better modeling of the fluid flow in faulted and fractured reservoirs which could be oil, gas or water bearing. The Lower Triassic Buntsandstein sandstones outcrop of Cleebourg is located in the Hochwald Horst affected by a major NNE-SSW striking fault, and the structure globally dips with 30° toward Rhenish Fault (Upper Rhine Graben main western border fault). The study of the outcrop aims to decipher the fluid-flow scheme and interactions between fracture network and diagenetic features distribution in the damage zone of a fault, located close to major faulted areas, through field and laboratories petrophysical measurements (permeability, thermic conductivity), and samples microstructural and diagenetical descriptions. The outcrop is structurally divided into a 14 meters thick fault core, surrounded by 5 meters thick transition zones, and damage zone of minimum thickness of 40 meters (total thickness unknown, due to the limits of the outcrop). Damage zone includes three fractured corridors, perpendicular to bedding and from 2 to 5 meters thick. Results presented here were acquired in 2 different layers with similar lithology but only on damage zone samples. In entire damage zone, porosity results and thin section description allow to distinguish two different facies: • Fa1 Intermediate porous (porosity of 12%) sandstone with major illite cement and clay content up to 20% (detrital and diagenetic); • Fa2 High porous (porosity >15%) sandstone with quartz feeding

  18. Petrophysical properties and 3D block model of Buntsandstein Sandstones reservoir (Upper Rhine Graben)

    NASA Astrophysics Data System (ADS)

    Sébastien, Haffen; Yves, Géraud; Marc, Diraison; Chrystel, Dezayes

    2013-04-01

    Buntsandstein sandstones (upper Permian to middle Triassic), located in the Upper Rhine Graben, appear as an easy target for geothermal exploitation: this reservoir links more or less permeable argillaceous sandstones, intersected by many major faults, to the regional thermal anomaly. In this context, we propose a conceptual geological 3-D block model of the Buntsandstein reservoir which could be used as a guide for future regional geothermal exploration or exploitation. This block presents the Buntsandstein sandstones reservoir at depth with different sedimentary facies (braided rivers, playa lake and fluvio-aeolian), above the Palaeozoic Granit and below the Muschelkalk limestones, intersecting by faults oriented according regional major azimuths: (1) ≈N020°E, corresponding to Rhenish faults and (2) ≈N060°E (or ≈N130°E) corresponding to Hercynian reactivated faults. Petrophysical properties of the reservoir are both controlled by matrix and faults/fractures characteristics. (1) Matrix properties (porosity, permeability, thermal conductivity, Pwaves velocity) have been determined from petrophysical measurements performed on cores of 15 borehole, mainly on borehole EPS1 (Soultz-sous-Forêts, France), continuously cored through Buntsandstein; (2) from thermal gradient analyses based on thermal conductivity measurements on core samples and also from borehole temperature logs run in the same borehole. This last approach allows locating fluid flow and thus permeability at reservoir scale. The flow paths appear as a composite network controlled by 'sedimentary' permeability on one hand and by 'fracture' permeability on the other. Fracturing associated with major fault zones provide pathways for the upward flowing fluids to connect with stratigraphic levels characterized by high matrix permeability and no impermeable macroscopic layers. This is why the Playa Lake and Fluvio-aeolian marginal erg facies provide a reservoir connected to a deep hot fluid source

  19. Does Neglecting Facies Structure Obscure the Underlying Fractal Descriptions of Natural Heterogeneity: Levy Versus Gaussian Behavior of Increment Ln(K).

    NASA Astrophysics Data System (ADS)

    Molz, F. J.

    2002-12-01

    display Gaussian behavior in the relevant delta[Ln(K)] PDFs, and that the Levy-like model has resulted, at least in part, due to mixing data from different facies. Three sets of data that support this viewpoint are presented and discussed, one from an alluvial fan, a second from an eolian sandstone, and the third from a bioturbated, near-shore sandstone. Possible limitations of the working hypothesis are discussed also.

  20. Isotopic fractionation of uranium in sandstone

    USGS Publications Warehouse

    Rosholt, J.N.; Shields, W.R.; Garner, E.L.

    1963-01-01

    Relatively unoxidized black uranium ores from sandstone deposits in the western United States show deviations in the uranium-235 to uranium-234 ratio throughout a range from 40 percent excess uranium-234 to 40 percent deficient uranium-234 with respect to a reference uranium-235 to uranium-234 ratio. The deficient uranium-234 is leached preferentially to uranium-238 and the excess uranium-234 is believed to result from deposition of uranium-234 enriched in solutions from leached deposits.

  1. Potential non-tertiary additional oil recovery from heterogeneous submarine-fan reservoirs, Spraberry-Benedum field, Midland basin, Texas

    SciTech Connect

    Guevara, E.H.; Worrall, J.G.; Walter, T.

    1987-05-01

    The Spraberry-Benedum field is a multipay, solution-gas drive, combined structural-stratigraphic trap. It contains approximately 200 million bbl of original oil in place and has been waterflooded since 1967. Producing intervals are in the Spraberry formation (Permian, Leonardian), which in this area consists of mixed-sediment submarine-fan deposits (upper and lower Spraberry) and basin-plain facies (middle Spraberry). Principal oil reservoirs, with 12% average porosity and permeabilities of less than 1 md, occur in the lower and upper Spraberry. They consist of naturally fractured, very fine-grained sandstones and coarse siltstones of braided and meandering, peripheral channels and associated outer fan facies. Complex facies architecture results in highly heterogeneous reservoirs. Oil accumulations are layered because basin-plain shales vertically separate submarine-fan reservoirs, and they are laterally compartmentalized due to the channelization of reservoir rocks. Production trends locally parallel to facies trends indicate that recovery is influenced by reservoir stratigraphy. Well locations, based only on structural position and fracture orientation, commonly do not conform to the axes of belts of greatest sandstone-siltstone thickness, which contain the best reservoirs. Furthermore, completion intervals do not systematically tap both lower and upper Spraberry reservoirs. Ultimate recovery will be improved by aggressive development programs aimed at producing from poorly drained traps created by reservoir heterogeneities. Recompletion and deepening of wells, strategic infill drilling, and injection patterns in such programs should be based on detailed reservoir stratigraphy, in addition to structure and fracture data.

  2. National uranium resource evaluation: San Antonio Quadrangle, Texas

    SciTech Connect

    Greimel, T.C.; Ambrose, M.L.

    1982-04-01

    The San Antonio Quadrangle, Texas, was evaluated to a depth of 1500 m to identify environments and define areas favorable for the occurrence of uranium deposits. The areas were delineated according to criteria established by the National Uranium Resource Evaluation program funded by the United States Department of Energy. Surface studies included investigations of uranium occurrences described in the literature, location of aerial radiometric anomalies, outcrop investigation, and followup of hydrogeochemical and stream-sediment reconnaissance data. Selected geologic units were evaluated in the subsurface using electric and gamma-ray well logs that were used to construct subsurface maps and cross sections. The environment favorable for Texas roll-type sandstone deposits is present in eleven areas in the Queen City and Carrizo Formations and the Wilcox Group. Six geologic units remain unevaluated. All other geologic units in this quadrangle are considered unfavorable.

  3. National Uranium Resource Evaluation: Laredo Quadrangle, Texas

    SciTech Connect

    Cherepon, A.J.; Stauber, A.J.

    1982-08-01

    The Laredo Quadrangle, Texas, was evaluated to a depth of 1500 m to identify environments and delineate areas favorable for the occurrence of uranium deposits. The areas were delineated in accordance with criteria established by the National Uranium Resource Evaluation program sponsored by the US Department of Energy. Surface studies included investigations of uranium occurrences described in the literature, location of aerial radiometric anomalies, outcrop studies, and followup of hydrogeochemical and stream-sediment reconnaissance data. Subsurface evaluation of selected geologic units was accomplished by using electric and gamma-ray well logs to construct maps and cross sections. An environment favorable for Texas roll-type sandstone uranium deposits is identified in 62 areas in the Goliad, Oakville, Catahoula, Frio, and Whitsett Formations. The Midway Group; the Reklaw, Weches, Cook Mountain, Caddell, Wellborn, Manning, Vicksburg, and Anahuac Formations; the Chusa Member of the Catahoula Formation; the Fleming, Uvalde, Lissie, and Beaumont Formations; and river-terrace deposits and deposits of recent age are considered unfavorable. The Yegua, Sparta, Laredo, and Queen City Formations; the El Pico Clay; the Bigford and Carrizo Formations; the Wilcox Group; and the Escondido, Olmos, and San Miguel Formations were examined but not evaluated.

  4. Synkinematic quartz cementation in partially open fractures in sandstones

    NASA Astrophysics Data System (ADS)

    Ukar, Estibalitz; Laubach, Stephen E.; Fall, Andras; Eichhubl, Peter

    2014-05-01

    Faults and networks of naturally open fractures can provide open conduits for fluid flow, and may play a significant role in hydrocarbon recovery, hydrogeology, and CO2 sequestration. However, sandstone fracture systems are commonly infilled, at least to some degree, by quartz cement, which can stiffen and occlude fractures. Such cement deposits can systematically reduce the overall permeability enhancement due to open fractures (by reducing open fracture length) and result in permeability anisotropies. Thus, it is important to identify the factors that control the precipitation of quartz in fractures in order to identify potential fluid conduits under the present-day stress field. In many sandstones, quartz nucleates syntaxially on quartz grain or cement substrate of the fracture wall, and extends between fracture walls only locally, forming pillars or bridges. Scanning electron microscope cathodoluminescence (SEM-CL) images reveal that the core of these bridges are made up of bands of broken and resealed cement containing wall-parallel fluid inclusion planes. The fluid inclusion-rich core is usually surrounded by a layer of inclusion-poor clear quartz that comprises the lateral cement. Such crack-seal textures indicate that this phase was precipitating while the fractures were actively opening (synkinematic growth). Rapid quartz accumulation is generally believed to require temperatures of 80°C or more. Fluid inclusion thermometry and Raman spectroscopy of two-phase aqueous fluid-inclusions trapped in crack-seal bands may be used to track the P-T-X evolution of pore fluids during fracture opening and crack-seal cementation of quartz. Quartz cement bridges across opening mode fractures in the Cretaceous Travis Peak Formation of the tectonically quiescent East Texas Basin indicate individual fractures opened over a 48 m.y. time span at rates of 16-23 µm/m.y. Similarly, the Upper Cretaceous Mesaverde Group in the Piceance Basin, Colorado contains fractures that

  5. Petrology and palaeoenvironmental significance of authigenic iron-rich clays, carbonates and apatite in the Claiborne Group, Middle Eocene, NE Texas

    NASA Astrophysics Data System (ADS)

    Huggett, J. M.; Gale, A. S.; McCarty, D.

    2010-07-01

    The Claiborne Group (Eocene) in North East Texas consists of clayey sandstones and mudrocks, both with variable proportions of dark green to brown clay pellets deposited in a marginal to open marine setting on the Gulf Coast margin. The composition of concretionary carbonate and clay pellets, from 5 localities, has been investigated using a wide variety of analytical techniques. Our palaeontological, sedimentological, C/S and stable isotope data support an interpretation of marginal marine facies with limited freshwater input, for the Claiborne Group. Dark green (mature) pellets are predominantly associated with transgressive, bioturbated, marine sediments. From the Weches Formation through to the youngest Crockett Formation there is a trend from pellets composed mostly of dark green serpentine-rich mixed layer clay to those of mostly brown (immature) nontronite-rich mixed layer clay. The serpentine is intermediate between odinite and berthierine and may have been originally odinite that has undergone partial transformation to berthierine. Pellet maturity apparently corresponds with the degree of winnowing and sedimentation rate. It does not appear to correspond with global temperature fluctuations, though the serpentine-rich rather than glauconite-rich composition may do. Siderite cement, mostly in the form of concretions, post-dates the iron-rich clay pellets and pre-dates calcite cement. Carbonate and apatite concretions show a wide range of mineral cement textures, reflecting variation in sedimentary environment and early diagenetic processes. Based on water temperatures derived from verneriacardia bivalves a precipitation temperature of 20 °C is assumed for the concretionary siderite. Using this temperature we surmise that the siderite precipitated from marine pore waters with intermittent meteoric water mixing.

  6. Grampian high-pressure-granulite-facies metamorphism of the Slishwood Division, NW Ireland and its enigmatic eclogite-facies precursor

    NASA Astrophysics Data System (ADS)

    Daly, J. S.; Flowerdew, M. J.; Whitehouse, M. J.

    2012-04-01

    The Slishwood Division of NW Ireland is located along the SW margin of the Grampian belt, whose metamorphism and deformation is generally attributed to the collision of outboard magmatic arcs with the Laurentian continental margin during the c. 470 Ma Grampian Orogeny. The unusual metamorphic history of the Slishwood Division (with eclogite-facies and later high-pressure-granulite-facies assemblages) is a unique feature of the Grampian belt and has long been regarded as evidence for pre-Caledonian tectonism, possibly of Grenvillian age. Detrital zircon U-Pb dating of Slishwood Division metasediments shows that they were deposited after c. 926 Ma, ruling out a Grenville event. A maximum age for the eclogite-facies event is provided by a U-Pb zircon age of 596 ± 6 Ma for a suite of metabasite intrusives, which exhibit varying degrees of decompression from eclogite- to high pressure granulite-facies or amphibolite-facies assemblages accompanied by the development of migmatitic leucosomes. Zircons in these leucosomes yield U-Pb zircon ages of c. 470 Ma identical to metamorphic zircons in a relatively dry partially decompressed eclogite. Following polyphase deformation, migmatitic leucosomes in metasediments crystallized under high pressure granulite-facies conditions during sinistral transtension. Dating these leucosomes has been challenging because the majority of zircons within them are inherited and generally only thin (< 15 μm) euhedral magmatic zircon overgrowths are present. Careful targeting with the ion microprobe yields U-Pb ages of c. 470 Ma, consistent with a U-Pb zircon age of c. 470 Ma from a cross-cutting granite pegmatite. In addition the high pressure granulite facies mineral fabrics are cut by tonalite bodies also dated at 470 Ma (ref. 1). Based on these results, we interpret the Slishwood Division as a Neoproterozoic metasedimentary sequence deposited after c. 926 Ma on what became a microcontinental fragment that detached from Laurentia during the

  7. Recent sedimentary facies in interdistributary basin, Mississippi delta

    SciTech Connect

    Hi, I.Y.; Kosters, E.; Moslow, T.F.

    1986-05-01

    Five sedimentary facies have been recognized from 23 vibracores in an abandoned interdistributary basin of the St. Bernard delta lobe, 15 km southeast of New Orleans. They are: (1) detrital clays containing shell fragments and lenticular laminations, interpreted as a bay facies; (2) laminated to massive-appearing, fine grained sandbeds averaging 10-20 cm in thickness, of possible overbank or crevasse splay origin; (3) thinly interbedded, parallel laminated and ripple laminated, sandy and clayey silts forming 50 to 70-cm-thick sequences that increase in clay content upwards, interpreted as flood events during overbank deposition; (4) extensively rooted detrital clays with less than 10% organic matter as disseminated plan material, representing a transitional, brackish-to-saline marsh facies; (5) organic-rich clays (35-75% organic matter) and peats (> 75% organic matter), interpreted as marsh and swamp facies. Major depositional environments observed on the present deltaic plain include irregular-shaped lakes, distributary channels, natural levees, overbank splays, small meandering channels, oyster reefs, and swamp, brackish and saline marshes.

  8. Mechanical stratigraphy of deep-water sandstones: insights from a multisciplinary field and laboratory study

    NASA Astrophysics Data System (ADS)

    Agosta, Fabrizio; di Celma, Claudio; Tondi, Emanuele; Corradetti, Amerigo; Cantalamessa, Gino

    2010-05-01

    Turbidite sandstones found in deep-water fold-and-thrust belts are increasingly exploited as hydrocarbon reservoirs. Within these rocks, the fluid flow is profoundly affected by the complex interaction between primary sedimentological and stratigraphic attributes (i.e, facies, layering, reservoir quality, stacking patterns, bed connectivity and lateral extent) and fracture characteristics (i.e., length, spacing, distribution, orientation, connectivity). Unfortunately, most of these features are at, or below, the resolution of conventional seismic datasets and, for this reason, their identification and localization represent one of the fundamental challenges facing exploration, appraisal and production of the sandstone reservoirs. In this respect, whereas considerable effort has been afforded to a characterization of the sedimentological and stratigraphic aspects of sandstones, detailed analysis of fractures in this type of successions has received significantly less attention. In this work, we combine field and laboratory analyses to assess the possible mechanical control exerted by the rock properties (grain size, intergranualr porosity, and Young modulus), as well as the influence of bed thickness, on joint density in turbidite sandstones. Joints are mode-I fractures occurring parallel to the greatest principle stress axis, which solve opening displacement and do not show evidence of shearing and enhance the values of total porosity forming preferential hydraulic conduits for fluid flow. Within layered rocks, commonly, joints form perpendicular to bedding due to overburden or exhumation. The empirical relation between joint spacing and bed thickness, documented in the field by many authors, has been mechanically related to the stress perturbation taking place around joints during their formation. Furthermore, close correlations between joint density and rock properties have been already established. In this present contribution, we focus on the bed

  9. Sylvatic trichinellosis in Texas.

    PubMed

    Pence, D B; La Rosa, G; Mancini Barbieri, F; Amati, M; Casulli, A; Pozio, E

    2001-06-01

    There are no published reports of domestic or sylvatic trichinellosis in Texas. The aim of the present survey was to determine the presence of Trichinella species in selected representative species of potential wildlife reservoirs in southern Texas. In 1998-99, tongues of 211 wild mammals were collected in southern Texas: 154 coyotes (Canis latrans), three bobcats (Lynx rufus), 32 racoons (Procyon lotor), 13 opossum (Didelphis marsupialis), four ocelots (Leopardus pardalis) and five wild boars (Sus scrofa). Presence of Trichinella sp. larvae was investigated by artificial digestion and larvae of positive samples were identified at the species level by a multiple-polymerase chain reaction analysis. Nine (5.8%) coyotes had trichinellosis; in the muscles of seven of these coyotes, the larvae were identified as Trichinella murrelli. This is the first report of sylvatic trichinellosis in Texas. PMID:11484391

  10. Scope and construction of a gas and oil atlas series of the Gulf of Mexico: Examples from Texas offshore lower Miocene plays

    SciTech Connect

    Seni, S.J.; Desselle, B.A.; Standen, A.

    1994-12-31

    An atlas series about the offshore northern Gulf of Mexico will group gas and oil reservoirs into subregional plays and will display reservoir data on a computerized geographical information system. The atlas series will provide critically compiled reservoir engineering data to help the private sector explore and develop hydrocarbons and to help the public sector analyze the hydrocarbon endowment in this basin. In this report, we cover aspects of the play-analysis procedure and provide specific examples of lower Miocene plays from the upper Texas coast and Federal Outer Continental Shelf (OCS). Play analysis emphasizes using broad classes of structural style, depositional style and environments, and defining attributes to group reservoirs into plays. To date, we have identified 4 Oligocene and 25 Miocene plays in Texas State offshore waters and 115 plays in the Federal OCS. Texas State offshore plays are gas prone (cumulative production 3.7 TcF) and are preferentially trapped in rollover anticlines. Miocene plays include submarine-fan Lenticulina sandstones; progradational Dicorbis b., Siphonina d., Marginulina a., and Lenticulina sandstones; transgressive sandstones associated with a barrier-bar system in the Matagorda Area; and transgressive Amphistegina B sandstones. Particularly productive gas-prone plays are progradational Sihonina d. deltas in the High Island Area and progradational Marginulia a. shelf and deltaic sandstones in the Matagorda Island and Brazos Areas.

  11. Paluxy of the Central Basin-East Texas

    SciTech Connect

    Presley, M.W. )

    1993-09-01

    The Paluxy Formation (Lower Cretaceous) has been a consistent sandstone exploration objective in the central East Texas basin, occurring at moderate depths on the order of 5000-8000 ft with oil in reservoirs with good permeability and porosity and reserves in the range of 200,000 to 500,000 bbl per well. Since the 1940s, the pace of Paluxy field discovery has been steady, generally a new field or two every one or two years, and there is every reason to believe that there is continued potential for the Paluxy in the future. The central part of the East Texas basin, in Smith County and adjacent areas, has complex structure with numerous salt domes and intervening sediment wedges (turtles) that formed during movement of the salt. Paluxy oil and gas in this area occurs mainly in combination structural-stratigraphic traps along normal faults that cut turtles. Major exploration trends in the central basin include (1) the Lindale turtle with a number of widely spaced fields, generally with only a few wells but with relatively good per-well reserves, (2) the Tyler turtle with the largest fields and some of the most prolific Paluxy production in the central basin, (3) the Flint and Irene turtles with relatively thin sandstones and modest production, (4) the Lane Chapel turtle with some exciting new Paluxy discoveries, and (5) the rim areas of salt domes.

  12. Sedimentological, biogeochemical and mineralogical facies of Northern and Central Western Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Spagnoli, Federico; Dinelli, Enrico; Giordano, Patrizia; Marcaccio, Marco; Zaffagnini, Fabio; Frascari, Franca

    2014-11-01

    The aim of this work was to identify sedimentary facies, i.e. facies having similar biogeochemical, mineralogical and sedimentological properties, in present and recent fine sediments of the Northern and Central Adriatic Sea with their spatial and temporal variations. Further aims were to identify the transportation, dispersion and sedimentation processes and provenance areas of sediments belonging to the facies. A Q-mode factor analysis of mineralogical, granulometric, geochemical (major and trace elements) and biochemical (organic carbon and total nitrogen) properties of surficial and sub-surficial sediments sampled in the PRISMA 1 Project has been used to identify the sedimentary facies. On the whole, four facies were identified: 1) Padanic Facies, made up of fine siliciclastic sediments which reach the Adriatic Sea mainly from the Po River and are distributed by the Adriatic hydrodynamic in a parallel belt off the Italian coast. Southward, this facies gradually mixes with sediments from the Apennine rivers and with biogenic autochthonous particulate; 2) Dolomitic Facies, made up of dolomitic sediments coming from the eastern Alps. This facies is predominant north of the Po River outfalls and it mixes with Padanic Facies sediments in front of the Po River delta; 3) Mn-carbonate Facies, made up of very fine sediments, rich in coccolithophores and secondary Mn-oxy-hydroxides resulting from the reworking of surficial fine sediments in shallow areas and subsequent deposition in deeper areas; 4) Residual Facies, made up of coarse siliciclastic sediments and heavy minerals resulting from the action of waves and coastal currents; this facies is present mainly in inshore areas. The zoning of the facies, resulting from this study, will make possible the identification, through further investigation, on a greater scale, of more accurate facies borders and the recognition of sub-facies, resulting from secondary or weaker biogeochemical processes.

  13. Acoustic Facies Analysis of Side-Scan Sonar Data

    NASA Astrophysics Data System (ADS)

    Dwan, Fa Shu

    Acoustic facies analysis methods have allowed the generation of system-independent values for the quantitative seafloor acoustic parameter, backscattering strength, from GLORIA and (TAMU) ^2 side-scan sonar data. The resulting acoustic facies parameters enable quantitative comparisons of data collected by different sonar systems, data from different environments, and measurements made with survey geometries. Backscattering strength values were extracted from the sonar amplitude data by inversion based on the sonar equation. Image processing products reveal seafloor features and patterns of relative intensity. To quantitatively compare data collected at different times or by different systems, and to ground truth-measurements and geoacoustic models, quantitative corrections must be made on any given data set for system source level, beam pattern, time-varying gain, processing gain, transmission loss, absorption, insonified area contribution, and grazing angle effects. In the sonar equation, backscattering strength is the sonar parameter which is directly related to seafloor properties. The GLORIA data used in this study are from the edge of a distal lobe of the Monterey Fan. An interfingered region of strong and weak seafloor signal returns from a flat seafloor region provides an ideal data set for this study. Inversion of imagery data from the region allows the quantitative definition of different acoustic facies. The (TAMU) ^2 data used are from a calibration site near the Green Canyon area of the Gulf of Mexico. Acoustic facies analysis techniques were implemented to generate statistical information for acoustic facies based on the estimates of backscattering strength. The backscattering strength values have been compared with Lambert's Law and other functions to parameterize the description of the acoustic facies. The resulting Lambertian constant values range from -26 dB to -36 dB. A modified Lambert relationship, which consists of both intercept and slope

  14. Bob West field: Extending upper Wilcox production in south Texas

    SciTech Connect

    Montgomery, S.L.

    1997-05-01

    Discovered in 1990 near the southern limit of the upper Wilcox gas-producing trend in south Texas, Bob West field is the largest pool to date in this trend, with probable reserves of up to 1 Tcf. The field produces from seven major sandstone {open_quotes}packages,{close_quotes} comprising 27 individual reservoirs and distributed over 3500 productive acres. The sandstones represent either fluvial/deltaic deposits or delta-margin barrier bar and strand-plain sediments. Porosities range up to 20%, but permeabilities are low, commonly less than 1.5 md. Artificial stimulation is therefore required to establish commercial rates of production. Bob West lies on a faulted anticline between two major growth-fault structures, with several stages of structural development evident. Such development has directly affected sandstone thickness. Rates of production are higher at Bob West than at other upper Wilcox fields due to commingling of zones, large-scale fracture treatments, and directional drilling. Discovery at Bob West has significant implications for renewed exploration in this part of the upper Wilcox gas trend.

  15. Depositional facies, environments and sequence stratigraphic interpretation of the Middle Triassic-Lower Cretaceous (pre-Late Albian) succession in Arif El-Naga anticline, northeast Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    El-Azabi, M. H.; El-Araby, A.

    2005-01-01

    The Middle Triassic-Lower Cretaceous (pre-Late Albian) succession of Arif El-Naga anticline comprises various distinctive facies and environments that are connected with eustatic relative sea-level changes, local/regional tectonism, variable sediment influx and base-level changes. It displays six unconformity-bounded depositional sequences. The Triassic deposits are divided into a lower clastic facies (early Middle Triassic sequence) and an upper carbonate unit (late Middle- and latest Middle/early Late Triassic sequences). The early Middle Triassic sequence consists of sandstone with shale/mudstone interbeds that formed under variable regimes, ranging from braided fluvial, lower shoreface to beach foreshore. The marine part of this sequence marks retrogradational and progradational parasequences of transgressive- and highstand systems tract deposits respectively. Deposition has taken place under warm semi-arid climate and a steady supply of clastics. The late Middle- and latest Middle/early Late Triassic sequences are carbonate facies developed on an extensive shallow marine shelf under dry-warm climate. The late Middle Triassic sequence includes retrogradational shallow subtidal oyster rudstone and progradational lower intertidal lime-mudstone parasequences that define the transgressive- and highstand systems tracts respectively. It terminates with upper intertidal oncolitic packstone with bored upper surface. The next latest Middle/early Late Triassic sequence is marked by lime-mudstone, packstone/grainstone and algal stromatolitic bindstone with minor shale/mudstone. These lower intertidal/shallow subtidal deposits of a transgressive-systems tract are followed upward by progradational highstand lower intertidal lime-mudstone deposits. The overlying Jurassic deposits encompass two different sequences. The Lower Jurassic sequence is made up of intercalating lower intertidal lime-mudstone and wave-dominated beach foreshore sandstone which formed during a short

  16. Killian's photographs: "Facies dolorosa", the countenance of pain.

    PubMed

    Luger, Veronika; Feistle, Frank; Feistle, Gerhard; Feistle, Jörg

    2016-07-01

    The book "Facies dolorosa" by Hans Killian, first published in 1934 and later in 1956 and 1967 as extended and annotated versions, comprises ~ 70 photographs depicting facial expressions of patients suffering from various diseases. The photographs in black and white are analyzed and annotated by the author with the purpose of providing clinicians, and especially young doctors, with an insight into the medical and scientific value of facial expression of pain in the diagnosis, staging, and prognosis of severe disease. This historical review of a book no longer in print is part of a 2016 commemorative publication marking the 60th anniversary of the publication of the "Facies dolorosa" by Dustri Medical and Scientific Publications, Munich, Germany and Rockledge, USA. PMID:27191769

  17. Lateral facies variations in hydromagmatic pyroclastic deposits at Linosa, Italy

    NASA Astrophysics Data System (ADS)

    Lajoie, J.; Lanzafame, G.; Rossi, P. L.; Tranne, C. A.

    1992-12-01

    The Linosa volcano, less than a million years old, located in the Sicilian Channel, is formed by a series of coalescing tuff cones, tuff rings, spatter cones, and lava flows among which the Fossa Cappellano produced a succession of surges (the "Fossa Cappellano 2" deposits). Which travelled up to 1225 m. The lapilli and coarse ashes in the deposits are generally mud-coated, accretionary lapilli are common, and the tuffs are frequently vesiculated suggesting that the surges responsible for the deposits were wet. The continuous lateral exposures, from the interior of the Fossa to the extreme edge of the island, show facies evolving in the direction of transport from a massive, in the most proximal section to one dominated by cross-laminated beds in the most distal section, passing by a parallel-laminated (plane bed) facies. In each facies, mean bed thickness, and grain size decrease regularly down current. In the cross-laminated facies, mega-ripple wavelength and amplitude decrease in the direction of transport. In the coarser sizes there is a significant increase in the direction of transport of the lower-density scoriae coupled with a decrease of the non-vesiculated lithics. In the finer sizes, there is a significant increase in relative abundance, of the lower-density feldspar crystals relative to the Fe-Mg crystals. The composition, texture, and primary structure variations of the Fossa deposits are identical to those observed in turbidite sequences, and are similar to the characteristics observed in dry surge deposits recently described from Korea. They are interpreted similarly in terms of decreasing flow power in the direction of transport.

  18. The Texas Twin Project

    PubMed Central

    Harden, K. Paige; Tucker-Drob, Elliot M.; Tackett, Jennifer L.

    2013-01-01

    Socioeconomic position, racial/ethnic minority status, and other characteristics of the macro-environment may be important moderators of genetic influence on a wide array of psychosocial outcomes. Designed to maximize representation of low socioeconomic status families and racial/ethnic minorities, the Texas Twin Project is an on-going study of school-age twins (preschool through 12th grade) enrolled in public schools in the Austin, Texas and Houston, Texas metropolitan areas. School rosters are used to identify twin families from a target population with sizable populations of African-American (18%), Hispanic / Latino (48%), and non-Hispanic White (27%) children and adolescents, over half of whom meet U.S. guidelines for classification as economically disadvantaged. Initial efforts have focused on a large-scale, family-based survey study involving both parent and child reports of personality, psychopathology, physical health, academic interests, parent-child relationships, and aspects of the home environment. In addition, the Texas Twin Project is the basis for an in-laboratory study of adolescent decision-making, delinquency, and substance use. Future directions include geographic expansion of the sample to the entire state of Texas (with a population of over 25 million people) and genotyping of participating twins. PMID:23111007

  19. Pre-Pliocene history and depositional facies, Nile Delta, Egypt

    SciTech Connect

    Harms, J.C.; Wray, J.L.

    1988-08-01

    The Nile delta area has a long history of subsidence and deposition that is inferred to extend back to Jurassic or earlier times. Depositional environments, rates of subsidence, and structural events are quite varied during this time span. Deposition was dominated by platform-to-basin carbonate facies from Jurassic to Eocene time and by detrital sediments from the Oligocene onward. Deposits are truly deltaic, in the sense of representing focused deposition at the shoreline by a large integrated river, only from latest Miocene time onward. A probable transition from continental to oceanic crust typical of the southern Mediterranean margin is overlain in the delta area by Mesozoic platform carbonates that appear to change in seismic data northward into slope and basinal facies. This platform margin, which trends east-west through the central delta, is reflected in later stratigraphic and structural characteristics; very thick Tertiary deposits, bathyal facies of Oligocene to Pliocene age, and large rotated fault blocks of Miocene strata occur only north of this margin.

  20. Facies Analysis and b-Value for Operationally Induced Microseismicity

    NASA Astrophysics Data System (ADS)

    Eaton, D. W. S.; Davidsen, J.; Maghsoudi, S.

    2015-12-01

    Operationally induced microseismicity reveals brittle failure processes that occur during hydraulic fracturing stimulation of a rockmass. The b-value of the magnitude-frequency distribution is commonly used to characterize the relative abundance of high- to low-magnitude events. In contrast to earthquake fault systems with b ~ 1, microseismicity that is directly associated with hydraulic fracturing is typically characterized by b > 1.5. Recent studies show that such unusually high b-values may be primarily controlled by scaling properties of mechanical bed thickness within the treatment zone, since the occurrence of fracture arrest at bedding boundaries gives rise to stratabound fracture networks. Stress variations also influence the b-value. These concepts provide a framework for microseismic facies analysis, a novel approach for interpretation of microseismicity that facilitates delineation of lithofacies units and stress compartments for characterization of unconventional reservoirs. Microseismic facies units are recognized on the basis of clustering analysis and recognition of distinct sets of microseismic attributes, which include b-value (and other magnitude statistics), duration, transience, seismic moment density and seismic moment release rate in addition to commonly reported characteristics of azimuth and dimensions. A case study is presented, in which microseismic facies analysis is applied to characterize an unconventional reservoir.

  1. Comparison of four approaches to a rock facies classification problem

    USGS Publications Warehouse

    Dubois, M.K.; Bohling, G.C.; Chakrabarti, S.

    2007-01-01

    In this study, seven classifiers based on four different approaches were tested in a rock facies classification problem: classical parametric methods using Bayes' rule, and non-parametric methods using fuzzy logic, k-nearest neighbor, and feed forward-back propagating artificial neural network. Determining the most effective classifier for geologic facies prediction in wells without cores in the Panoma gas field, in Southwest Kansas, was the objective. Study data include 3600 samples with known rock facies class (from core) with each sample having either four or five measured properties (wire-line log curves), and two derived geologic properties (geologic constraining variables). The sample set was divided into two subsets, one for training and one for testing the ability of the trained classifier to correctly assign classes. Artificial neural networks clearly outperformed all other classifiers and are effective tools for this particular classification problem. Classical parametric models were inadequate due to the nature of the predictor variables (high dimensional and not linearly correlated), and feature space of the classes (overlapping). The other non-parametric methods tested, k-nearest neighbor and fuzzy logic, would need considerable improvement to match the neural network effectiveness, but further work, possibly combining certain aspects of the three non-parametric methods, may be justified. ?? 2006 Elsevier Ltd. All rights reserved.

  2. Diagenesis of the Almond sandstone in the Washakie Basin

    SciTech Connect

    Yin, Peigui; Liu, Jie; Surdam, C.R. . Dept. of Geology and Geophysics)

    1992-01-01

    The marginal marine and nonmarine Almond sandstones are mostly sublitharenite, litharenite, and lithic arkose. The sandstones are fine-to very-fine-grained, and are well-sorted. The framework composition, authigenic minerals, and porosity and permeability distributions in the Almond sandstones are different below and above 8,000 feet, resulting in a variation in hydrocarbon reservoir types. The shallow conventional reservoirs are permeable, producing both liquid oil and gas, whereas the deep gas-bearing sandstones are very tight and overpressured. Porosity of the shallow Almond sandstones have been significantly enhanced by dissolution of the feldspar grains and lithic fragments. Quartz overgrowth cement and authigenic clay rims have occluded most of the intergranular pores, as well as the previously leached pores. The Almond sandstones have been buried deeper than their present depths. The sandstones in each part of the Washakie Basin have experienced different uplift and subsidence. Reconstruction of the burial history and diagenetic modeling are essential steps for understanding the diagenetic evolution of the Almond sandstones.

  3. Porosity-permeability trends, Sparta B Sandstones (Eocene), Fordoche field, Pointe Coupee Parish, Louisiana

    SciTech Connect

    Krutak, P.R. )

    1991-03-01

    Fordoche field, Pointe Coupee Parish, Louisiana (44 wells) contains at least ten hydrocarbon-bearing zones. Major reserves of bypassed oil probably exist in the shallowest reservoir, Sparta B, estimated to contain {approximately}5.6 mm STB OIP and 2.0 bcf GIP. Sparta B pay thicknesses average 15 ft with 24.7% porosities and 200 md permeabilities. Other averages include: 7,980 PSI BHP (abnormal range), 228F BHT, 2,075 PSIG bubble point pressure, gas-oil ratio 500 SCF/bbl, oil gravities 40-44 API. Petrographic, SEM, and EDX study of 20 thin sections from these units discloses the following down-core trends and petrofacies: (1) high porosity (20-25%)-permeability (250-500+ md), fine- to very fine-grained quartzarenites whose pore throats average about 10 microns comprise the storm washover deposits. Vermicular chlorite begins to occlude porosity near the bottom of this unit (11,338.25 ft); (2) pore throats of 10-20 microns occur in quartzarenitic, upper shoreface sandstones that display slightly lower porosity and permeability than overlying units. Kaolinite and chlorite begin to occlude porosity in this facies (11,346.00 ft and 11,347.50 ft); calcite completely occludes porosity at 11,350.46 ft; (3) lower shoreface sandstones are increasingly organic, mostly very fine sand size. Organic lamellae parallel to bedding are characteristic with pore throats in the 10-15 micron-size range; chlorite and calcite occlude porosity at 11,360.50 ft and 11,365.00 ft, respectively; (4) inner shelf lithologies are very fine-grained, highly organic, micaceous, poorly sorted quartzarenites with virtually no permeability. Pore throats are small ({approximately}10 microns). Biotite occludes porosity at 11,374.67 ft, muscovite at 11,375.79 ft.

  4. Depositional and diagenetic variability within the Cambrian Mount Simon Sandstone: Implications for carbon dioxide sequestration

    USGS Publications Warehouse

    Bowen, B.B.; Ochoa, R.I.; Wilkens, N.D.; Brophy, J.; Lovell, T.R.; Fischietto, N.; Medina, C.R.; Rupp, J.A.

    2011-01-01

    The Cambrian Mount Simon Sandstone is the major target reservoir for ongoing geologic carbon dioxide (CO2) sequestration demonstrations throughout the midwest United States. The potential CO2 reservoir capacity, reactivity, and ultimate fate of injected CO2 depend on textural and compositional properties determined by depositional and diagenetic histories that vary vertically and laterally across the formation. Effective and efficient prediction and use of the available pore space requires detailed knowledge of the depositional and diagenetic textures and mineralogy, how these variables control the petrophysical character of the reservoir, and how they vary spatially. Here, we summarize the reservoir characteristics of the Mount Simon Sandstone based on examination of geophysical logs, cores, cuttings, and analysis of more than 150 thin sections. These samples represent different parts of the formation and depth ranges of more than 9000 ft (>2743 m) across the Illinois Basin and surrounding areas. This work demonstrates that overall reservoir quality and, specifically, porosity do not exhibit a simple relationship with depth, but vary both laterally and with depth because of changes in the primary depositional facies, framework composition (i.e., feldspar concentration), and diverse diagenetic modifications. Diagenetic processes that have been significant in modifying the reservoir include formation of iron oxide grain coatings, chemical compaction, feldspar precipitation and dissolution, multiple generations of quartz overgrowth cementation, clay mineral precipitation, and iron oxide cementation. These variables provide important inputs for calculating CO2 capacity potential, modeling reactivity, and are also an important baseline for comparisons after CO2 injection. Copyright ??2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  5. Hydrological modelling in sandstone rocks watershed

    NASA Astrophysics Data System (ADS)

    Ponížilová, Iva; Unucka, Jan

    2015-04-01

    The contribution is focused on the modelling of surface and subsurface runoff in the Ploučnice basin. The used rainfall-runoff model is HEC-HMS comprising of the method of SCS CN curves and a recession method. The geological subsurface consisting of sandstone is characterised by reduced surface runoff and, on the contrary, it contributes to subsurface runoff. The aim of this paper is comparison of the rate of influence of sandstone on reducing surface runoff. The recession method for subsurface runoff was used to determine the subsurface runoff. The HEC-HMS model allows semi- and fully distributed approaches to schematisation of the watershed and rainfall situations. To determine the volume of runoff the method of SCS CN curves is used, which results depend on hydrological conditions of the soils. The rainfall-runoff model assuming selection of so-called methods of event of the SCS-CN type is used to determine the hydrograph and peak flow rate based on simulation of surface runoff in precipitation exceeding the infiltration capacity of the soil. The recession method is used to solve the baseflow (subsurface) runoff. The method is based on the separation of hydrograph to direct runoff and subsurface or baseflow runoff. The study area for the simulation of runoff using the method of SCS CN curves to determine the hydrological transformation is the Ploučnice basin. The Ploučnice is a hydrologically significant river in the northern part of the Czech Republic, it is a right tributary of the Elbe river with a total basin area of 1.194 km2. The average value of CN curves for the Ploučnice basin is 72. The geological structure of the Ploučnice basin is predominantly formed by Mesozoic sandstone. Despite significant initial loss of rainfall the basin response to the causal rainfall was demonstrated by a rapid rise of the surface runoff from the watershed and reached culmination flow. Basically, only surface runoff occures in the catchment during the initial phase of

  6. Brittle and compaction creep in porous sandstone

    NASA Astrophysics Data System (ADS)

    Heap, Michael; Brantut, Nicolas; Baud, Patrick; Meredith, Philip

    2015-04-01

    Strain localisation in the Earth's crust occurs at all scales, from the fracture of grains at the microscale to crustal-scale faulting. Over the last fifty years, laboratory rock deformation studies have exposed the variety of deformation mechanisms and failure modes of rock. Broadly speaking, rock failure can be described as either dilatant (brittle) or compactive. While dilatant failure in porous sandstones is manifest as shear fracturing, their failure in the compactant regime can be characterised by either distributed cataclastic flow or the formation of localised compaction bands. To better understand the time-dependency of strain localisation (shear fracturing and compaction band growth), we performed triaxial deformation experiments on water-saturated Bleurswiller sandstone (porosity = 24%) under a constant stress (creep) in the dilatant and compactive regimes, with particular focus on time-dependent compaction band formation in the compactive regime. Our experiments show that inelastic strain accumulates at a constant stress in the brittle and compactive regimes leading to the development of shear fractures and compaction bands, respectively. While creep in the dilatant regime is characterised by an increase in porosity and, ultimately, an acceleration in axial strain to shear failure (as observed in previous studies), compaction creep is characterised by a reduction in porosity and a gradual deceleration in axial strain. The overall deceleration in axial strain, AE activity, and porosity change during creep compaction is punctuated by excursions interpreted as the formation of compaction bands. The growth rate of compaction bands formed during creep is lower as the applied differential stress, and hence background creep strain rate, is decreased, although the inelastic strain required for a compaction band remains constant over strain rates spanning several orders of magnitude. We find that, despite the large differences in strain rate and growth rate

  7. Texas Almanac, 2002-2003.

    ERIC Educational Resources Information Center

    Ramos, Mary G., Ed.

    The 61st edition of the "Texas Almanac" has a reputation as the definitive source for Texas information since 1857. It contains details of the Census 2000 official population count, including statewide, county and town counts, plus an analysis of the numbers by experts at Texas's State Data Center. It includes information about politics,…

  8. Transforming Developmental Education in Texas

    ERIC Educational Resources Information Center

    Journal of Developmental Education, 2014

    2014-01-01

    In recent years, with support from the Texas Legislature, the Texas Higher Education Coordinating Board has funded various developmental education initiatives, including research and evaluation efforts, to help Texas public institutions of higher education provide more effective programs and services to underprepared students. Based on evaluation…

  9. Facies analysis of yedoma thermokarst lakes on the northern Seward Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Farquharson, Louise; Anthony, Katey Walter; Bigelow, Nancy; Edwards, Mary; Grosse, Guido

    2016-07-01

    Thermokarst lakes develop as a result of the thaw and collapse of ice-rich, permanently frozen ground (permafrost). Of particular sedimentological importance are thermokarst lakes forming in late Pleistocene icy silt (yedoma), which dramatically alter the land surface by lowering surface elevation and redistributing upland sediment into lower basins. Our study provides the first description of yedoma thermokarst lake sedimentology based on the cross-basin sampling of an existing lake. We present lake sediment facies descriptions based on data from sediment cores from two thermokarst lakes of medium depth, Claudi and Jaeger (informal names), which formed in previously non thermokarst-affected upland yedoma on the northern Seward Peninsula, Alaska. We identify four prominent facies using sedimentological, biogeochemical, and macrofossil indicators: a massive silt lacking aquatic macrofossils and other aquatic indicators situated below a sub-lacustrine unconformity (Facies 1); two basal deposits: interbedded organic silt and chaotic silt (Facies 2-3); and a silt-rich mud (Facies 4). Facies 1 is interpreted as yedoma that has thawed during lake formation. Facies 3 formed adjacent to the margin due to thaw and collapse events from the lake shore. Material from Facies 3 was reworked by wave action to form Facies 2 in a medium energy margin environment. Facies 4 formed in a lower energy environment toward the lake basin center. This facies classification and description should enhance our ability (i) to interpret the spatial and temporal development of lakes and (ii) to reconstruct long-term patterns of landscape change.

  10. Provenance of sandstones in the Golconda terrane, north central Nevada

    SciTech Connect

    Jones, E.A. )

    1991-02-01

    The upper Paleozoic Golconda terrane of north-central Nevada is a composite of several structurally bounded subterranes made of clastic, volcanic, and carbonate rocks. The clastic rocks provide important clues for the interpretation of the provenance and paleogeographic settings of the different lithologic assemblages found in these subterranes. Two petrographically distinct sandstones are identified in the Golconda terrane in the Osgood Mountains and the Hot springs Range of north-central Nevada. The sandstone of the Mississippian Farrel Canyon Formation, part of the Dry Hills subterrane, is characterized by quartzose and sedimentary and lithic-rich clasts with a small feldspar component. in contrast, the sandstone of the Permian Poverty Peak (II) subterrane is a silty quartzarenite with no lithic component, and a very limited feldspar component. The sandstone of the Farrel Canyon Formation is similar to nonvolcanic sandstones reported from elsewhere in the Golconda terrane. Modal data reflect a provenance of a recycled orogen and permit the interpretation that it could have been derived from the antler orogen as has been proposed for other sandstones of the golconda terrane. The sandstone of the Poverty Peak (II) subterrane is more mature than any of the other sandstones in either the Golconda terrane, the Antler overlap sequence, or the Antler foreland basin sequence. Modal data put the Poverty Peak (II) sandstone in the continental block provenance category. The distinct extrabasinal provenances represented in these different sandstones support the idea that the Golconda basin was made up of complex paleogeographic settings, which included multiple sources of extrabasinal sediment.

  11. Facies architecture and diagenesis of Belgian Late Frasnian carbonate mounds

    NASA Astrophysics Data System (ADS)

    Boulvain, Frédéric

    2001-12-01

    Late Frasnian Petit-Mont Member carbonate mounds occur in the southern part of the Dinant Synclinorium and in the Philippeville Anticline (SW Belgium). These mounds are 30 to 80 m thick and 100 to 250 m in diameter. They are embedded in shale, nodular shale and argillaceous limestone. Based on facies mapping of 14 buildups and related off-mound sediments, these mounds typically started from below the photic and storm wave base zones and builtup into shallow water environments. Above an argillaceous limestone substrate, the first carbonate mound facies consists of spiculitic wackestone with stromatactis (PM1), which becomes progressively enriched in crinoids and corals (PM2), then in peloids, stromatoporoids and cyanobacteria (PM3). PM4 consists of algal-coral-peloid wackestone and packstone with green algae and thick algal coatings. A core of algal and microbial bindstone (PM5) sporadically occurs within large mounds. The uppermost part of these mounds may show a recurrence of facies PM2 and PM1. PM1 to PM3 are coloured red by hematite derived from microaerophilic iron bacteria; PM4 and PM5 are grey. The transition from the aphotic to the cyanobacterial photic zone is recorded in the succession PM2-PM3; the transition from the cyanobacterial to the green algal photic zone is recorded by PM3-PM5. Storm wave base was reached within PM3 and fair-weather wave base within PM5. This paleobathymetric interpretation suggests a depth of 100-150 m during initial establishment of PM1. Three types of mounds can be distinguished on the basis of geometry and facies architecture: (1) "Les Bulants"-type mounds display a continuous vertical facies succession (PM2-3-4-5) and low relief; (2) although exhibiting the same facies succession as "Les Bulants", "Les Wayons"-type mounds show a distinct relief with steep flanks and bioclastic talus; (3) "St.-Rémy" mounds consist exclusively of PM1 and PM2, bioclastic flank deposits are not observed. From (1) to (3), these mound types

  12. High-resolution facies analysis and sequence stratigraphy of fluvio-deltaic depositional systems in tectonically-active basins (Jean Baptiste Lamarck Medal)

    NASA Astrophysics Data System (ADS)

    Mutti, E.

    2012-04-01

    In ancient tectonically-active basins fed by relatively small and high-gradient rivers, both marine and lacustrine fluvio-deltaic systems display similar vertical stacking patterns which are primarily controlled by high-frequency variations of sediment flux to the basin. These variations are superimposed over higher-order cycles of tectonic uplift and relative quiescence recorded by changes in the source areas, basin configuration and overall style of sedimentation.Spectacular examples of these cyclically stacked successions crop out in the upper Cretaceous and Paleogene deposits of the south-central Pyrenean foreland basin. Similar stacking patterns are also common in other basins (e.g., the Jurassic-Cretaceous Nequen basin, Argentina and the Tertiary Piedmont Basin, northwestern Italy). Sediment flux to the sea controls the high-frequency stacking pattern of ancient fluvio-deltaic depositional systems through cyclic variations in flow efficiency which is mainly a function of the magnitude and sediment concentration of river outflows during floods. These variations result in periods of inertia- and friction-dominated jet flows followed by periods during which fluvial activity dramatically decreases. These cyclic variations, which are ultimately controlled by climate and baselevelchanges (Milankowitch cycles), are recorded by m- to dam-thick facies successions that can be interpreted as the basic "building block" (in sequence-stratigraphic parlance) of larger-scale depositional sequences. Inertia-dominated periods are characterized by large-volume highly erosive hyperpycnal flows typically containing abundant skeletal debris and mudstone clasts. These flows bypass river mouths and carry sand tonearshore and shelfal regions forming m-thick packets of tabular graded sandstone beds with HCS alternating with muddier facies. These sandstones, which extend up to several km in shelfal regions and grade distally into prodeltaic sediments, are a typical and volumetrically

  13. Determination of pressure solution shortening in sandstones

    NASA Astrophysics Data System (ADS)

    Onasch, Charles M.

    1993-11-01

    A new method for the determination of pressure solution shortening in sandstones uses the geometry of grain-to-grain interpenetrations and grains truncated against solution surfaces. These features are used to construct plots from which the magnitude and direction of the pressure solution shortening can be determined. Using simulated pressure solution deformation of artificial and natural grain populations, the new method is shown to correctly assess a variety of coaxial and non-coaxial shortenings. Although primarily intended to determine shortening, the method can also quantify extension related to growth of beards or overgrowths during pressure solution. Application of the method to naturally deformed quartz arenite samples shows that pressure solution shortening of up to 26% occurred during compaction and 22% during layer-parallel shortening.

  14. Dilatant hardening of fluid-saturated sandstone

    NASA Astrophysics Data System (ADS)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  15. Deformation and fracture of Berea sandstone

    NASA Astrophysics Data System (ADS)

    Bernabe, Yves; Brace, W. F.

    Samples of Berea sandstone were deformed to failure at different values of the confining pressure, Pc (from 10 to 250 MPa), and the pore pressure, Pp (from 0 to 130 MPa), at different strain rates and with pore fluids of different viscosities. Axial stress and strain were recorded in all tests. In addition, volumetric strain was measured in tests run at a strain rate of 2×10-5 s-1. The microstructure of several deformed samples was observed using the SEM. When the pore fluid was distilled water, the tests were performed in truly drained conditions at all strain rates. Results indicated that Pc and Pp had roughly opposite effects. With increasing Pc-Pp the samples showed a smooth transition from localized brittle fracture to uniformly distributed cataclastic flow. The data collected agreed well with a theoretical model in which strain localization is considered as an instability in the material constitutive relations. In Berea sandstone the stabilizing mechanism appeared to be the compaction caused by fragmentation of grains and the rearrangement of these fragments in the preexisting pore space. When the pore fluid was a highly viscous silicone fluid and the strain rate was 2×10-3 s-1, the sample behavior was not consistent with truly drained conditions. In the brittle regime a decrease in pore pressure within the sample due to dilation produced dilatancy-hardening. The samples deformed in the ductile regime, on the other hand, showed a loss of strength and signs of embrittlement. This weakening/embrittiement was caused by an increase in pore pressure within the sample due to compaction.

  16. Wettability Behavior of Crude Oil-Silica Nanofluids-Sandstone Systems

    NASA Astrophysics Data System (ADS)

    Bai, Lingyun; Li, Chunyan; Pales, Ashley; Huibers, Britta; Ladner, David; Daigle, Hugh; Darnault, Christophe

    2016-04-01

    Mobilizing and recovering crude oils from geological formations is critical for the management and exploitation of petroleum reservoirs. Nanoparticles, with their unique physico-chemical properties can increase the efficiency of enhanced oil recovery (EOR) by decreasing interfacial tension (IFT) between the oil and aqueous phase systems, and altering rock wettability. Our research examines the potential use of nanoparticles as a means of EOR by studying the influence of silicon oxide (SIO2) nanoparticles on the wettability and interfacial tension of different crude oil-silica nanofluids-sandstone systems. We designed nanofluid treatments to manipulate changes in wettability of Berea and Boise sandstones simulating petroleum reservoir. Experiments were performed to measure the IFT and wettability involving different concentrations of nanoparticles with and without the addition of surfactant to determine which nanofluids produced the most favorable wettability changes for optimal EOR with light crude oil (e.g., West Texas, API: 40), medium crude oil (Prudhoe Bay, API: 28), and heavy crude oil (e.g., Lloydminster, API: 20). We investigated the addition of Tween 20 nonionic surfactant to the nanoparticle dispersions - made from SiO2 nanoparticles - that allows the optimum mobility in porous media through optimization of interfacial tension (IFT) and contact angle, and conducted tests. Batch studies were conducted to measure the IFT and wettability of the nanofluids of different range of nanoparticle concentrations (0-0.1 wt. %) in different reservoir conditions, i.e. brine and brine-surfactant systems made with 5% brine and 2CMC of Tween 20 nonionic surfactants. The dynamic behavior of IFT was monitored using a pendant drop method. Five percent brine-nanoparticle systems containing 0.001 and 0.01 wt.% of nanoparticles resulted in a significant decrease of IFT for light and medium crude oils, while the highest decrease of IFT for heavy crude oil was observed with 0.1 wt

  17. Contractional deformation of porous sandstone: Insights from the Aztec Sandstone, SE Nevada, USA

    NASA Astrophysics Data System (ADS)

    Fossen, Haakon; Zuluaga, Luisa F.; Ballas, Gregory; Soliva, Roger; Rotevatn, Atle

    2015-05-01

    Contractional deformation of highly porous sandstones is poorly explored, as compared to extensional deformation of such sedimentary rocks. In this work we explore the highly porous Aztec Sandstone in the footwall to the Muddy Mountain thrust in SE Nevada, which contains several types of deformation bands in the Buffington tectonic window: 1) Distributed centimeter-thick shear-enhanced compaction bands (SECBs) and 2) rare pure compaction bands (PCBs) in the most porous parts of the sandstone, cut by 3) thin cataclastic shear-dominated bands (CSBs) with local slip surfaces. Geometric and kinematic analysis of the SECBs, the PCBs and most of the CSBs shows that they formed during ∼E-W (∼100) shortening, consistent with thrusting related to the Cretaceous to early Paleogene Sevier orogeny of the North American Cordilleran thrust system. Based on stress path modeling, we suggest that the compactional bands (PCBs and SECBs) formed during contraction at relatively shallow burial depths, before or at early stages of emplacement of the Muddy Mountains thrust sheet. The younger cataclastic shear bands (CSBs, category 3), also related to E-W Sevier thrusting, are thinner and show larger shear offsets and thus more intense cataclasis, consistent with the initiation of cataclastic shear bands in somewhat less porous materials. Observations made in this work support earlier suggestions that contraction lead to more distributed band populations than what is commonly found in the extensional regime, and that shear-enhanced compaction bands are widespread only where porosity (and permeability) is high.

  18. Tornado from Texas.

    ERIC Educational Resources Information Center

    Vail, Kathleen

    1996-01-01

    Santa Fe School Superintendent Yvonne Gonzales, the "Texas Tornado," was hired to fix a 40% student-dropout rate and a white/Hispanic gap in achievement test scores. Gonzales is an avid integrationist; relies on humor, appeasement, and persuasion tactics; and has alienated some school employees by increasing central office administrators. (MLH)

  19. Texas Irrigation Situation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The irrigation situation in Texas is an interaction between hydrology and water policies. In 2012, according to National Agricultural Statistical Service (NASS) four High Plains counties, Gainesville, Yoakum, Terry and Cochran, accounted for approximately 60% of the 150,000 acres of peanut productio...

  20. NARSTO Texas Final Report

    Atmospheric Science Data Center

    2013-03-06

    Final Report for the Texas PM2.5 Sampling and Analysis Study (March 11, ... Tropp,et al, 1998     NOTE: The Final Report is separated into the following PDF files: Section 1: ... Mass and Chemical Composition (PDF) Section 5: Summary, Conclusions, and Recommendations and Section 6 Bibliography (PDF) ...

  1. East Texas Quilts.

    ERIC Educational Resources Information Center

    Whiteside, Karen, Ed.

    1986-01-01

    Patchwork quilting is an original folk art in the United States. Pilgrims first used worn out scraps of cloth to make bed covers in an age of scarcity. Featured here are stories on East Texas Quilts, their origins, the love and hard work which goes into the making of a quilt (Ira Barr and others). The techniques needed to construct a quilt are…

  2. West Texas State University.

    ERIC Educational Resources Information Center

    Roach, Ed D.

    1988-01-01

    Threats in the external environment, the arrival of a planning-oriented new president, and new regional reaccreditation criteria prompted West Texas State University to undertake a successful strategic planning venture. Leadership must focus strategic planning in a manner that recognizes the decentralized and collegial elements present in higher…

  3. ECOREGION DELINEATION IN TEXAS

    EPA Science Inventory

    Level III ecoregions are being refined and subdivided into level IV for the state of Texas. This work is consistent with ecoregion revision and subdivision that has been completed or is on-going in 37 of the conterminous United States. The two-year project is collaborative, inv...

  4. Texas Hunter Education Manual.

    ERIC Educational Resources Information Center

    Hall, Steve

    This handbook serves as a reference for the mandatory hunter education course in Texas. The "Introduction" explains hunter education's goal to produce safe, knowledgeable, responsible, and informed hunters. It also gives information related to hunting opportunities, administration, and management. Chapter 2, "Our Hunting Heritage," gives a…

  5. The Woodlands, Texas.

    ERIC Educational Resources Information Center

    McHaney, Larry J.; Bernhardt, Jerry

    1988-01-01

    The authors describe the "central project" concept for implementing technology education while addressing education reform. The central project is a topic around which students, teachers, administrators, and the community focus their energies as a team. At McCullough High School (Texas), the central project involved design and development of a…

  6. Texas and SREB

    ERIC Educational Resources Information Center

    Southern Regional Education Board (SREB), 2009

    2009-01-01

    The Southern Regional Education Board (SREB) is a nonprofit organization that works collaboratively with Texas and 15 other member states to improve education at every level--from pre-K to postdoctoral study--through many effective programs and initiatives. SREB's "Challenge to Lead" Goals for Education, which call for the region to lead the…

  7. Trouble at Texas Southern

    ERIC Educational Resources Information Center

    Asquith, Christina

    2006-01-01

    On the night of December 4, 2004, a Texas Southern University (TSU) student named Ashley Sloan was gunned down near campus, struck in the temple by a bullet after leaving a party with her friends. The murder prompted an outpouring of accusations concerning poor campus security. For many Houstonians, the shooting raised old fears of the…

  8. Outdoor Education in Texas.

    ERIC Educational Resources Information Center

    Myers, Ray H.

    In Dallas in 1970, high school outdoor education began as a cocurricular woods and waters boys' club sponsored by a community sportsman. Within one year, it grew into a fully accredited, coeducational, academic course with a curriculum devoted to the study of wildlife in Texas, ecology, conservation, hunting, firearm safety, fishing, boating and…

  9. Texas-Oklahoma

    Atmospheric Science Data Center

    2014-05-15

    article title:  Texas-Oklahoma Border     ... important resources for farming, ranching, public drinking water, hydroelectric power, and recreation. Both originate in New Mexico and ... NASA's Goddard Space Flight Center, Greenbelt, MD. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science ...

  10. The Texas Formula System.

    ERIC Educational Resources Information Center

    Steen, Ralph W.; And Others

    Explained and illustrated is the formula funding system used for colleges and universities in Texas. This system is considerably more complicated than the formulas used in other states. Data for institutions in the state system for fiscal 1978 are presented; actual appropriations are used rather than requests, and formula-produced amounts are…

  11. Wind powering America - Texas

    SciTech Connect

    O'Dell, K.

    2000-04-13

    This fact sheet contains a description of the wind energy resources in the state of Texas and the state's efforts to develop wind energy production, green power, and net metering programs. The fact sheet also includes a list of contacts for those interested in obtaining more information.

  12. Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in Frio Fluvial-Deltaic reservoirs of South Texas. Technical progress report, October 1, 1993--December 31, 1993

    SciTech Connect

    Tyler, N

    1993-12-31

    Advanced reservoir characterization techniques are being applied to selected reservoirs in the Frio Fluvial-Deltaic Sandstone (Vicksburg Fault Zone) trend of South Texas in order to maximize the economic producibility of resources in this mature oil play. More than half of the reservoirs in this depositionally complex play have already been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define untapped, incompletely drained, and new pool reservoirs as suitable targets for near-term recovery methods. This project is developing interwell-scale geological facies models and assessing engineering attributes of Frio fluvial-deltaic reservoirs in selected fields in order to characterize reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. The results of these studies will lead directly to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling. Project objectives are divided into three major phases. Phase I, reservoir selection and initial framework characterization, consisted of the initial tasks of screening fields within the play to select representative reservoirs that have a large remaining oil resource and are in danger of premature abandonment and performing initial characterization studies on selected reservoirs to identify the potential in untapped, incompletely drained, and new pool reservoirs. Phase 11 will involve advanced characterization of selected reservoirs to delineate incremental resource opportunities. Subtasks here include the volumetric assessments of untapped and incompletely drained oil along with an analysis of specific targets for recompletion and strategic infill drilling.

  13. Sodium-hydroxide solution treatment on sandstone cores

    SciTech Connect

    Lee, S.J.

    1984-01-01

    This research was performed to study the effect of sodium hydroxide solution on the sandstone core samples and to develop a method whereby the permeability of the samples could be increased by the injection of sodium hydroxide solution. This work should provide the first step in developing a technique that can be used in the stimulation of oil and gas wells. A series of tests was conducted in which sodium hydroxide solution with concentrations ranging from 0.25 N to 2.00 N was injected into a number of Berea sandstone cores. The tests were conducted at room temperature and at 180{degree}F. In some cases the core sample were damaged by the injection of fresh water which resulted in a marked reduction in the permeability of the cores prior to the injection of sodium hydroxide solution. Based on laboratory testing with measurements of uniaxial compressive strength, SEM examination and X-ray analysis, it was found that sodium hydroxide interacted with sandstone to promote (1) partial dissolution of the sandstone minerals; (2) sandstone weight loss; (3) increased porosity; (4) weakening of the sandstone cores; and (5) changes in permeability. The interaction increased with increasing temperature and increasing sodium hydroxide concentration. However, at concentrations higher than 1.00 N, the degree of increase in permeability was not as large even though the sandstone weight loss and the increase in porosity did increase.

  14. Dinoflagellate species and organic facies evidence of marine transgression and regression in the atlantic coastal plain

    USGS Publications Warehouse

    Habib, D.; Miller, J.A.

    1989-01-01

    Palynological evidence is used to date and interpret depositional environments of sediments of Campanian, Maestrichtian and early Danian ages cored in three wells from South Carolina and Georgia. The evidence is usefil for distinguishing environments which lithofacies evidence indicates a range from nonmarine to coastal to inner neritic shallow shelf. Numerous dinoflagellate species and an organic facies defined abundant amoprphous debris (amorphous debris facies) distinguish shallow shelf sediments deposited during marine transgression. The nearshore amorphous debris facies of late Campanian age consists of heterogenous assemblages dominated by Palaeohystrichophora infusorioides Deflandre or Hystrichosphaerina varians (May). The farther offshore amorphous debris facies of late early Maestrichtian to late Maestrichtian age consists of heterogenous assemblages dominated by Glaphyrocysta retiintexta (Cookson) and/or Areoligera medusettiformis (Wetzel). The larger number of dinoflagellate species in the offshore facies represents the maximum transgression detected in the investigated interval. A multiple occurrence datum defined by the combination of first appearance, klast appearances and sole occurrence of dinoflagellate species at the base of each interval distinguished by the amorphous debris facies provides the first evidence of marine transgression. Relatively small organic residues consisting of intertinite and few or no palynomorphs define the inertinite facies in nonmarine deltaic and in coastal (lagoonal, tidal flat, interdistributary bary) sediments. Dinocyt{star, open}s are absent in the nonmarine sediments and are represented by few species and few specimens in the coastal inertinite faceis. A third organic facies (vascular tissue facies) is defined by the abundance of land plant tissue. Sporomorph species, including those of the Normapolles pollen group and of pteridophyte spores, comprise a large proportion of the total palynomorph flora in the

  15. Seismicity of west Texas

    SciTech Connect

    Dumas, D.B.

    1981-01-01

    A four year seismic study has found the Basin and Range province of west Texas and the adjacent area of Mexico to be more seismically active then than heretofore known. A University of Texas five station seismic array around the Marfa Basin has located or detected approximately 800 local and regional earthquakes with S-P times of less than 30 sec. A crustal model for the Basin and Range is derived from natural and artificial sources and contains four layers having velocities of 3.60, 4.93, 6.11, and 6.60 km/sec, respectively, overlying a mantle of 8.37 km/sec. A moderate level of seismic activity has been detected near Van Horn, in the Marfa Basin, and along the Texas-Mexico border between latitudes 30 and 31/sup 0/N. Five earthquake sequences were recorded, two near the Texas-Mexico border and three in the Marfa Basin. Four of these sequences showed quiescent periods in foreshock activity preceding the main shock. On the eastern side of the Marfa Basin a diffuse linear seismic zone may represent an unmapped fault, striking N 50/sup 0/W that coincides with Muehlberger's proposed eastern boundary of Basin and Range faulting. A new epicenter for the Valentine, Texas earthquake of August 16, 1931 has been relocated instrumentally at the northern end of this diffuse zone. Regional and local teleseismic P-wave arrival time anomalies observed for the nearby Gnome underground nuclear explosion of 1961 are used to determine station corrections and thus to locate the new 1931 epicenter at 3.69/sup 0/N, 104.57/sup 0/W. Several estimates of magnitude (m/sub b/) based on intensity data range from 5.6 to 6.4. Fault-plane and composite fault-plane solutions support Muehlberger's hypothesis that the Basin and Range is undergoing extension in a SW-NE direction.

  16. Catalogue of Texas spiders.

    PubMed

    Dean, David Allen

    2016-01-01

    This catalogue lists 1,084 species of spiders (three identified to genus only) in 311 genera from 53 families currently recorded from Texas and is based on the "Bibliography of Texas Spiders" published by Bea Vogel in 1970. The online list of species can be found at http://pecanspiders.tamu.edu/spidersoftexas.htm. Many taxonomic revisions have since been published, particularly in the families Araneidae, Gnaphosidae and Leptonetidae. Many genera in other families have been revised. The Anyphaenidae, Ctenidae, Hahniidae, Nesticidae, Sicariidae and Tetragnathidae were also revised. Several families have been added and others split up. Several genera of Corinnidae were transferred to Phrurolithidae and Trachelidae. Two genera from Miturgidae were transferred to Eutichuridae. Zoridae was synonymized under Miturgidae. A single species formerly in Amaurobiidae is now in the Family Amphinectidae. Some trapdoor spiders in the family Ctenizidae have been transferred to Euctenizidae. Gertsch and Mulaik started a list of Texas spiders in 1940. In a letter from Willis J. Gertsch dated October 20, 1982, he stated "Years ago a first listing of the Texas fauna was published by me based largely on Stanley Mulaik material, but it had to be abandoned because of other tasks." This paper is a compendium of the spiders of Texas with distribution, habitat, collecting method and other data available from revisions and collections. This includes many records and unpublished data (including data from three unpublished studies). One of these studies included 16,000 adult spiders belonging to 177 species in 29 families. All specimens in that study were measured and results are in the appendix. Hidalgo County has 340 species recorded with Brazos County at 323 and Travis County at 314 species. These reflect the amount of collecting in the area. PMID:27103878

  17. Catalogue of Texas spiders

    PubMed Central

    Dean, David Allen

    2016-01-01

    Abstract This catalogue lists 1,084 species of spiders (three identified to genus only) in 311 genera from 53 families currently recorded from Texas and is based on the “Bibliography of Texas Spiders” published by Bea Vogel in 1970. The online list of species can be found at http://pecanspiders.tamu.edu/spidersoftexas.htm. Many taxonomic revisions have since been published, particularly in the families Araneidae, Gnaphosidae and Leptonetidae. Many genera in other families have been revised. The Anyphaenidae, Ctenidae, Hahniidae, Nesticidae, Sicariidae and Tetragnathidae were also revised. Several families have been added and others split up. Several genera of Corinnidae were transferred to Phrurolithidae and Trachelidae. Two genera from Miturgidae were transferred to Eutichuridae. Zoridae was synonymized under Miturgidae. A single species formerly in Amaurobiidae is now in the Family Amphinectidae. Some trapdoor spiders in the family Ctenizidae have been transferred to Euctenizidae. Gertsch and Mulaik started a list of Texas spiders in 1940. In a letter from Willis J. Gertsch dated October 20, 1982, he stated “Years ago a first listing of the Texas fauna was published by me based largely on Stanley Mulaik material, but it had to be abandoned because of other tasks.” This paper is a compendium of the spiders of Texas with distribution, habitat, collecting method and other data available from revisions and collections. This includes many records and unpublished data (including data from three unpublished studies). One of these studies included 16,000 adult spiders belonging to 177 species in 29 families. All specimens in that study were measured and results are in the appendix. Hidalgo County has 340 species recorded with Brazos County at 323 and Travis County at 314 species. These reflect the amount of collecting in the area. PMID:27103878

  18. Sequence stratigraphic re-interpretation of [open quotes]stray[close quotes] sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

    SciTech Connect

    Hampson, G.J.; Howell, J.A.; Flint, S.S. )

    1996-01-01

    The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ([open quotes]Mancos B[close quotes]) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these [open quotes]stray[close quotes] sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discrete stratigraphic levels, thereby defining incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface [open quotes]Mancos B[close quotes] gas reservoir sandstones.

  19. Sequence stratigraphic re-interpretation of {open_quotes}stray{close_quotes} sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

    SciTech Connect

    Hampson, G.J.; Howell, J.A.; Flint, S.S.

    1996-12-31

    The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ({open_quotes}Mancos B{close_quotes}) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these {open_quotes}stray{close_quotes} sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discrete stratigraphic levels, thereby defining incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface {open_quotes}Mancos B{close_quotes} gas reservoir sandstones.

  20. Analysis of Critical Permeabilty, Capillary Pressure and Electrical Properties for Mesaverde Tight Gas Sandstones from Western U.S. Basins

    SciTech Connect

    Alan Byrnes; Robert Cluff; John Webb; John Victorine; Ken Stalder; Daniel Osburn; Andrew Knoderer; Owen Metheny; Troy Hommertzheim; Joshua Byrnes; Daniel Krygowski; Stefani Whittaker

    2008-06-30

    Although prediction of future natural gas supply is complicated by uncertainty in such variables as demand, liquefied natural gas supply price and availability, coalbed methane and gas shale development rate, and pipeline availability, all U.S. Energy Information Administration gas supply estimates to date have predicted that Unconventional gas sources will be the dominant source of U.S. natural gas supply for at least the next two decades (Fig. 1.1; the period of estimation). Among the Unconventional gas supply sources, Tight Gas Sandstones (TGS) will represent 50-70% of the Unconventional gas supply in this time period (Fig. 1.2). Rocky Mountain TGS are estimated to be approximately 70% of the total TGS resource base (USEIA, 2005) and the Mesaverde Group (Mesaverde) sandstones represent the principal gas productive sandstone unit in the largest Western U.S. TGS basins including the basins that are the focus of this study (Washakie, Uinta, Piceance, northern Greater Green River, Wind River, Powder River). Industry assessment of the regional gas resource, projection of future gas supply, and exploration programs require an understanding of reservoir properties and accurate tools for formation evaluation. The goal of this study is to provide petrophysical formation evaluation tools related to relative permeability, capillary pressure, electrical properties and algorithms for wireline log analysis. Detailed and accurate moveable gas-in-place resource assessment is most critical in marginal gas plays and there is need for quantitative tools for definition of limits on gas producibility due to technology and rock physics and for defining water saturation. The results of this study address fundamental questions concerning: (1) gas storage; (2) gas flow; (3) capillary pressure; (4) electrical properties; (5) facies and upscaling issues; (6) wireline log interpretation algorithms; and (7) providing a web-accessible database of advanced rock properties. The following text

  1. Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir.

    SciTech Connect

    Allison, M.L.

    1997-07-01

    The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial- deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project. Two activities continued this quarter as part of the geological and petrophysical characterization of the fluvial-deltaic Ferron Sandstone: (1) evaluation of the Ivie Creek case-study area and (2) technology transfer. The Ivie Creek case-study evaluation work during the quarter focused on the two parasequence sets, the Kf-1 and Kf-2, in the lower Ferron Sandstone. This work included: (1) clinoform characterization, (2) parasequence characterization from elevation and isopach maps, and (3) three-dimensional facies modeling. Scaled photomosaic panels from the Ivie Creek amphitheater (south-facing outcrop belt) and Quitchupah Canyon (Fig. 1) provide a deterministic framework for two apparent-dip cross sections. These panels along with other photomosaic coverage and data from five drill holes, ten stratigraphic sections, and 22 permeability transacts (Fig. 1), acquired during two field seasons, provided the necessary information for this geologic evaluation and creation of the models to be used

  2. Illinois basin. Overlooked Renault sandstone becomes a prime target

    SciTech Connect

    Gannon, L.

    1982-09-01

    Posey County is probably the most active area of exploration in S. Indiana right now. The Renault sandstone, an oil-prolific formation of Mississippian age has been virtually overlooked by operators for decades. Operators in Posey County are enjoying tremendous success in the renault sandstone. Its future as a primary target will depend greatly on its continued sucess. It could thrive for years to come, or it could be played out within a short time. However, one thing remains certain - interest will continue as long as oil flows and the Renault sandstone will rank high among primary target formation when 1982 statistics are released next year.

  3. Facies analysis and depositional environment of the Ames Marine Member of the Conemaugh Group in the Appalachian Basin

    SciTech Connect

    Al-Qayim, B.A.

    1983-01-01

    The lithologic and paleontological aspects for fifty localities of the Ames Marine Member were examined. The regional stratigraphic reconstruction shows that it is variably composed of limestone and shale, and often associated with a thin basal coal seam. A generalized, composite stratigraphic section of the Ames Member consists of the following units from top to bottom: the Grafton Sandstone, Nonmarine Shale, Upper Ames Shale, Upper Ames Limestone, Middle Ames Shale, Lower Ames Limestone, Lower Ames Shale, Ames Coal, Nonmarine Silty Shale, and Harlem Coal. Harlem coal is commonly the basal coal in Ohio, and the Ames Coal is common in Pennsylvania and West Virginia. Insoluble residue analysis of 223 samples shows that quartz and glauconite are the major and significant residues. The major petrographic components of the Ames rocks are bioclastic grains of echinoderm, brachiopods, molluscs, bryozoa, and foraminifera in a matrix variably composed of clay and calcium carbonate. A quantitative microfacies study applying factor and cluster analysis reveals five basin-wide biofacies and four lithofacies reflecting a gradient from shoreline to an offshore position. The areal and vertical distribution of the different facies reflects the transgression-regression history of the Ames Cycle. A uniform slow eustatic rise of sea level with an early rapid transgression was responsible for the deposition of most of the Ames marine section. The small, upper, underdeveloped regressive section suggests a rapid regression by active prograding deltaic deposits which rapidly terminated the marine conditions over most the the Appalachian Basin.

  4. Chromite in Lower Pennsylvanian Nuttall sandstone from West Virginia - Possible Blue Ridge province source

    SciTech Connect

    O'Connor, J.T. )

    1989-08-01

    Detrital chromite grains from heavy mineral separates of three samples of the Lower Pennsylvanian Nuttall Sandstone Member of the New River Formation were examined by use of a reflected-light petrographic microscope, a scanning electron microscope, and an electron microprobe. Some textures observed microscopically in the chromite grains are similar to those in chromite grains in dunite from the Blue Ridge province of North Carolina that has undergone regional metamorphism. Additional exsolution features are also observed in the chromites of this study. The major-oxide compositions of the detrital chromite grains vary more widely than those of the chromites of the Blue Ridge, possibly due to a larger sampling base. The detrital grain compositions (Cr/(Cr + Al), Mg/(Mg + Fe{sup +2})) plot near the fields of the Blue Ridge chromites, although the appearance of both more aluminum-rich and magnesium-poor compositions possibly indicate a higher facies of metamorphism than the Blue Ridge samples studied to date.

  5. Muddy and dolomitic rip-up clasts in Triassic fluvial sandstones: Origin and impact on potential reservoir properties (Argana Basin, Morocco)

    NASA Astrophysics Data System (ADS)

    Henares, Saturnina; Arribas, Jose; Cultrone, Giuseppe; Viseras, Cesar

    2016-06-01

    The significance of rip-up clasts as sandstone framework grains is frequently neglected in the literature being considered as accessory components in bulk sandstone composition. However, this study highlights the great value of muddy and dolomitic rip-up clast occurrence as: (a) information source about low preservation potential from floodplain deposits and (b) key element controlling host sandstone diagenetic evolution and thus ultimate reservoir quality. High-resolution petrographic analysis on Triassic fluvial sandstones from Argana Basin (T6 and T7/T8 units) highlights the significance of different types of rip-up clasts as intrabasinal framework components of continental sediments from arid climates. On the basis of their composition and ductility, three main types are distinguished: (a) muddy rip-up clasts, (b) dolomitic muddy rip-up clasts and (c) dolomite crystalline rip-up clasts. Spatial distribution of different types is strongly facies-related according to grain size. Origin of rip-up clasts is related to erosion of coeval phreatic dolocretes, in different development stages, and associated muddy floodplain sediments. Cloudy cores with abundant inclusions and clear outer rims of dolomite crystals suggest a first replacive and a subsequent displacive growth, respectively. Dolomite crystals are almost stoichiometric. This composition is very similar to that of early sandstone dolomite cement, supporting phreatic dolocretes as dolomite origin in both situations. Sandstone diagenesis is dominated by mechanical compaction and dolomite cementation. A direct correlation exists between: (1) muddy rip-up clast abundance and early reduction of primary porosity by compaction with irreversible loss of intergranular volume (IGV); and (2) occurrence of dolomitic rip-up clasts and dolomite cement nucleation in host sandstone, occluding adjacent pores but preserving IGV. Both processes affect reservoir quality by generation of vertical and 3D fluid flow baffles and

  6. The role of diagenetic studies in flow-unit modeling: San Andres formation, Yoakum County, Texas

    SciTech Connect

    Henderson, S. )

    1994-03-01

    The Permian San Andres Formation represents one of the most prolific hydrocarbon-producing intervals of the Permian basin. Dolostone lithofacies intercalated with thin evaporites accommodate highly compartmentalized reservoirs resulting from complex depositional and diagenetic histories. This compartmentalization often facilitates the use of these reservoirs in flow-unit studies. Perhaps more important than the relationship of productive intervals to depositional facies is the degree to which diagenetic processes have influenced reservoir properties. Detailed petrographic evaluation of the reservoir in question, though often overlooked, should be an integral part of flow-unit studies. Once a diagenetic sequence is established, the information may be incorporated in to the facies model to better understand how to subdivide the reservoir. Such an investigation has been conducted on the San Andres Formation in Reeves field of southeastern Yoakum County, Texas. Here, multistage diagenetic overprints are superimposed on depositional facies that vary in degree of lateral extent, thereby complicating the geometries of individual productive zones within the reservoir. Analysis of the reservoir reveals that Reeves San Andres sediments were subjected to dominant diagenetic processes, including dolomitization and sulfate implacement, both of which are major factors in porosity preservation, and a variety of minor processes that have had little effect on reservoir quality. The recognition of diagenetic facies, and understanding of the processes that have created them, and identification of the implications of these processes on reservoir properties is a vital part of any flow-unit study.

  7. Geochemistry of Eagle Ford group source rocks and oils from the first shot field area, Texas

    USGS Publications Warehouse

    Edman, Janell D.; Pitman, Janet K.

    2010-01-01

    Total organic carbon, Rock-Eval pyrolysis, and vitrinite reflectance analyses performed on Eagle Ford Group core and cuttings samples from the First Shot field area, Texas demonstrate these samples have sufficient quantity, quality, and maturity of organic matter to have generated oil. Furthermore, gas chromatography and biomarker analyses performed on Eagle Ford Group oils and source rock extracts as well as weight percent sulfur analyses on the oils indicate the source rock facies for most of the oils are fairly similar. Specifically, these source rock facies vary in lithology from shales to marls, contain elevated levels of sulfur, and were deposited in a marine environment under anoxic conditions. It is these First Shot Eagle Ford source facies that have generated the oils in the First Shot Field. However, in contrast to the generally similar source rock facies and organic matter, maturity varies from early oil window to late oil window in the study area, and these maturity variations have a pronounced effect on both the source rock and oil characteristics. Finally, most of the oils appear to have been generated locally and have not experienced long distance migration. 

  8. Subsurface Glen Rose reef trend in east Texas and west-central Louisiana

    SciTech Connect

    Adams, G.S.

    1983-03-01

    The subsurface Glen Rose reef trend in east Texas and west-central Louisiana (Lower Cretaceous Comanchean) is a regressive carbonate complex deposited on a broad shallow water shelf. The Glen Rose reef trend can be differentiated into two separate reef tracts that prograded seaward over a slowly subsiding shelf. It remains to be seen whether the Glen Rose reefs are actual framework reefs or mounds of transported material. Reef facies include poorly sorted caprinidcoral grainstones, moderately sorted peloid and oncolite packstones and grainstones, and well-sorted, very fine grained skeletal grainstones. Coated grains, abraded skeletal fragments, scoured bedding surfaces, and minor cross-beds are evidence for deposition of the reef facies in a high-energy shoal setting. The reefal buildups grade laterally into low-energy shallow water wackestones and mudstones containing toucasids, orbitolinids, and serpulid burrows. Porosities associated with the reefal buildups appear facies controlled. Caprinid-coral packstones and grainstones exhibit intraparticle, moldic, and vuggy porosities of 10 to 15%. Pinpoint microporosity of 5 to 10% are found within the finegrained skeletal grainstones. Fracture porosity enhances permeability in several facies. Moldic and vuggy porosity types are generally secondary whereas intraparticle porosity may be preserved primary. Coarse equant calcite commonly occludes intraparticle, moldic, vuggy, and fracture porosities. Dolomitization within the reef limestones may have acted to create or preserve porosities. Poor production from the Glen Rose reef trend has been attributed to the lack of structural closure.

  9. Acoustic facies of Holocene megaturbidites in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Rebesco, M.; Della Vedova, B.; Cernobori, L.; Aloisi, G.

    2000-09-01

    The acoustic facies of Holocene megaturbidites in the central-western abyssal plains of the Eastern Mediterranean Sea is analysed, combining core lithology and synthetic seismograms produced on the basis of P-wave velocity profiles derived by multi-sensor core logging (from a core in the Western Herodotous Trough). The acoustic facies of the megaturbidite is divided in two layers: (1) an upper, transparent, low velocity layer, corresponding to structureless mud; (2) a lower, highly reflective, high velocity layer, corresponding to the graded sandy base. Correlation with sub-bottom profiler data allowed us to estimate in about 21-23 m the maximum total thickness of the two-layer megaturbidite in the Ionian Abyssal Plain. These results demonstrate that thicknesses traditionally computed on the basis of the acoustically transparent layer alone may produce a relevant underestimation of the total volume of the deposit. The total volume of the megaturbidite, extending over the Ionian and Sirte Abyssal Plains including the western Herodotous Trough, is therefore estimated in about 162±10 km 3.

  10. Blueschist-facies metamorphism related to regional thrust faulting

    USGS Publications Warehouse

    Blake, M.C., Jr.; Irwin, W.P.; Coleman, R.G.

    1969-01-01

    Rocks of the blueschist (glaucophane schist) facies occur throughout the world in narrow tectonic belts associated with ultramafic rocks. In the Coast Range province of California, blueschist rocks are devloped in the eugeosynclinal Franciscan Formation of Late Mesozoic age. The blueschist rocks form a narrow belt for more than 800 km along the eastern margin of this province and commonly are separated from rocks of an overlying thrust plate by serpentinite. Increasing metamorphism upward toward the thrust fault is indicated mineralogically by a transition from pumpellyite to lawsonite and texturally by a transition from metagraywacke to schist. The blueschist metamorphism probably occurred during thrusting in a zone of anomalously high water pressure in the lower plate along the sole of the thrust fault. This tectonic mode of origin for blueschist differs from the generally accepted hypothesis involving extreme depth of burial. Other belts of blueschist-facies rocks, including the Sanbagawa belt of Japan, the marginal synclinal belt of New Zealand, and the blueschist-ultramafic belts of Venezuela, Kamchatka, Ural mountains, and New Caledonia have similar geologic relations and might be explained in the same manner. ?? 1969.

  11. Ejecta Dynamics during Hypervelocity Impacts into Dry and Wet Sandstone

    NASA Astrophysics Data System (ADS)

    Hoerth, T.; Schäfer, F.; Thoma, K.; Poelchau, M.; Kenkmann, T.; Deutsch, A.

    2011-03-01

    Hypervelocity impact experiments into dry and water saturated porous Seeberger sandstone were conducted at the two-stage light gas accelerator at the Ernst-Mach-Institute (EMI) and the ejecta dynamics were analyzed.

  12. Experimental Impact Cratering into Sandstone: A MEMIN-Progress Report

    NASA Astrophysics Data System (ADS)

    Poelchau, M. H.; Deutsch, A.; Kenkmann, T.; Hoerth, T.; Schäfer, F.; Thoma, K.; Memin Team

    2011-03-01

    The MEMIN Project is currently focused on impact experiments into sandstone. First results are presented here, including the evaluation of high-speed cameras, ejecta catchment devices, crater morphology, and chemical projectile-target interaction.

  13. Modeling CO2 distribution in a heterogeneous sandstone reservoir: the Johansen Formation, northern North Sea

    NASA Astrophysics Data System (ADS)

    Sundal, Anja; Miri, Rohaldin; Petter Nystuen, Johan; Dypvik, Henning; Aagaard, Per

    2013-04-01

    The last few years there has been broad attention towards finding permanent storage options for CO2. The Norwegian continental margin holds great potential for storage in saline aquifers. Common for many of these reservoir candidates, however, is that geological data are sparse relative to thoroughly mapped hydrocarbon reservoirs in the region. Scenario modeling provides a method for estimating reservoir performances for potential CO2 storage sites and for testing injection strategies. This approach is particularly useful in the evaluation of uncertainties related to reservoir properties and geometry. In this study we have tested the effect of geological heterogeneities in the Johansen Formation, which is a laterally extensive sandstone and saline aquifer at burial depths of 2 - 4 km, proposed as a suitable candidate for CO2 storage by Norwegian authorities. The central parts of the Johansen Formation are underlying the operating hydrocarbon field Troll. In order not to interfere with ongoing gas production, a potential CO2 injection well should be located at a safe distance from the gas reservoir, which consequently implies areas presently without well control. From 3D seismic data, prediction of spatial extent of sandstone is possible to a certain degree, whereas intra-reservoir flow baffles such as draping mudstone beds and calcite cemented layers are below seismic resolution. The number and lateral extent of flow baffles, as well as porosity- and permeability distributions are dependent of sedimentary facies and diagenesis. The interpretation of depositional environment and burial history is thus of crucial importance. A suite of scenario models was established for a potential injection area south of the Troll field. The model grids where made in Petrel based on our interpretations of seismic data, wire line logs, core and cuttings samples. Using Eclipse 300 the distribution of CO2 is modeled for different geological settings; with and without the presence of

  14. Pressure sensitivity of low permeability sandstones

    USGS Publications Warehouse

    Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.

    1987-01-01

    Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.

  15. Attenuation of Landfill Leachate In Unsaturated Sandstone

    NASA Astrophysics Data System (ADS)

    Butler, A. P.; Brook, C.; Godley, A.; Lewin, K.; Young, C. P.

    Landfill leachate emanating from old "dilute and disperse" sites represents a potential (and in many cases actual) threat to the integrity of groundwater. Indeed, this concern has been included in EU legislation (80/86/EEC), where key contaminants (e.g. ammonia, various toxic organic compounds and heavy metals) are explicitly highlighted in terms of their impact on groundwater. In the UK, whilst there are a substantial number of unlined landfills sited on major aquifers, many of these are in locations where there is a substantial unsaturated zone. Thus, there exists the opportunity for the modification and attenuation of contaminants prior to it encountering the water table. An understanding of likely changes in leachate content and concentrations at such sites will enable a more comprehensive assessment of the potential risks and liabilities posed by such sites to be evaluated. The Burntstump landfill, situated 8 km north of Nottingham (UK), is sited on an outcrop of Sherwood sandstone. The fine friable sand has been quarried since the 1960s and the excavated volume used to store municipal waste. Filling at the site commenced in the mid 1970s and originally was unlined. In 1978 the first of what was to become a series of boreholes was installed within an area of roughly 5 m radius over one of the original waste cells. Cores of the waste and underlying sandstone were extracted and analysed for a range of physical and chemical parameters. The most recent set of analyses were obtained in 2000. The series of investigations therefore provide an important record of leachate migration and modification through the unsaturated zone for over twenty years. The progression of the leachate front is clearly delineated by the chloride concentration profile with an average velocity of around 1.6 m.yr-1. Combining this value with an average (and reasonably uniform) measured moisture content of about 7% gives a mean inter-granular specific discharge of 110 mm.yr-1. An interesting

  16. Salt and ice crystallisation in porous sandstones

    NASA Astrophysics Data System (ADS)

    Ruedrich, Joerg; Siegesmund, Siegfried

    2007-03-01

    Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing scientific research done during the past century has shown that there are numerous parameters that have an influence on the weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally, laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation, and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings can help to understand the damaging mechanisms.

  17. Uranium migration through intact sandstone cores

    NASA Astrophysics Data System (ADS)

    Read, D.; Lawless, T. A.; Sims, R. J.; Butter, K. R.

    1993-06-01

    Uranium is often considered to be a mobile radioelement in the natural environment owing to its tendency to form stable complexes with a number of aqueous anions, particularly in oxidising milieu. A series of infiltration experiments were devised to investigate this migration behaviour under rigidly controlled laboratory conditions. Intact cores of Permo-Triassic Clashach Sandstone were pre-equilibrated with synthetic groundwater solutions and continuous flow-through of uranium monitored together with pH and concentrations of other ions. Prior to performing each experiment a simulation was carried out using a one-dimensional coupled chemical transport code, encompassing a thermodynamic description of the electrical double layer. These calculations together with electron microscopy indicated the potential role played by iron oxyhydroxide grain coatings in retarding the uranium plume. Thus, a second series of experiments was initiated on pre-acidified cores from which all surface exposed iron had been removed, allowing an assessment of the retention capacity of non-ferric components. Taken together, the data clearly illustrate the strong affinity of aqueous uranium species for natural surfaces even under strongly oxidising conditions. The success of the model in predicting a priori the dominant trends in uranium migration behaviour is encouraging and may aid in prioritising analytical requirements for investigations in more complex geochemical situations than those studied here.

  18. High resolution reservoir architecture of late Jurassic Haynesville ramp carbonates in the Gladewater field, East Texas Salt Basin

    SciTech Connect

    Goldhammer, R.K.

    1996-12-31

    The East Texas Salt Basin contains numerous gas fields within Upper Jurassic Haynesville ramp-complex reservoirs. A sequenced-keyed, high-resolution zonation scheme was developed for the Haynesville Formation in Gladewater field by integrating core description, well-log, seismic, porosity and permeability data. The Haynesville at Gladewater represents a high-energy ramp system, localized on paleotopographic highs induced by diapirism of Callovian Age Salt (Louann). Ramp crest grainstones serve as reservoirs. We have mapped the distribution of reservoir facies within a hierarchy of upward-shallowing parasequences grouped into low-frequency sequences. The vertical stacking patterns of parasequences and sequences reflect the interplay of eustasy, sediment accumulation patterns, and local subsidence (including salt movement and compaction). In this study we draw on regional relations from analogous, Jurassic systems in Mexico to constrain the stratigraphic architecture, age model, and facies model. Additionally, salt-cored Holocene, grain-rich shoals from the Persian Gulf provide excellent facies analogs. The result is a new high-resolution analysis of reservoir architecture at a parasequence scale that links reservoir facies to depositional facies. The new stratigraphy scheme demonstrates that different geographic portions of the field have markedly distinct reservoir intervals, both in terms of total pay and the sequence-stratigraphic interval within which it occurs. Results from this study are used to evaluate infill drill well potential, in well planning, for updating reservoir models, and in refining field reserve estimates.

  19. High resolution reservoir architecture of late Jurassic Haynesville ramp carbonates in the Gladewater field, East Texas Salt Basin

    SciTech Connect

    Goldhammer, R.K. )

    1996-01-01

    The East Texas Salt Basin contains numerous gas fields within Upper Jurassic Haynesville ramp-complex reservoirs. A sequenced-keyed, high-resolution zonation scheme was developed for the Haynesville Formation in Gladewater field by integrating core description, well-log, seismic, porosity and permeability data. The Haynesville at Gladewater represents a high-energy ramp system, localized on paleotopographic highs induced by diapirism of Callovian Age Salt (Louann). Ramp crest grainstones serve as reservoirs. We have mapped the distribution of reservoir facies within a hierarchy of upward-shallowing parasequences grouped into low-frequency sequences. The vertical stacking patterns of parasequences and sequences reflect the interplay of eustasy, sediment accumulation patterns, and local subsidence (including salt movement and compaction). In this study we draw on regional relations from analogous, Jurassic systems in Mexico to constrain the stratigraphic architecture, age model, and facies model. Additionally, salt-cored Holocene, grain-rich shoals from the Persian Gulf provide excellent facies analogs. The result is a new high-resolution analysis of reservoir architecture at a parasequence scale that links reservoir facies to depositional facies. The new stratigraphy scheme demonstrates that different geographic portions of the field have markedly distinct reservoir intervals, both in terms of total pay and the sequence-stratigraphic interval within which it occurs. Results from this study are used to evaluate infill drill well potential, in well planning, for updating reservoir models, and in refining field reserve estimates.

  20. Medicolegal hell in Texas.

    PubMed

    Korcok, M

    1995-10-01

    In the "war zones" of Texas, lawyers use billboards, television commercials and Yellow Page advertisements to announce their availability to help the "unjustly injured," and medicolegal lawsuits are as common as the rain that sweeps in from the nearby Gulf of Mexico. Almost 75% of the suits are dismissed without award or settlement, since many are plainly frivolous. However, even these can mean torment for physicians, who have to hire lawyers, answer charges, collect paperwork, take time off work for depositions and consultations, and then worry about how insurers will react the next time premiums are due--even if they are cleared. Texas estimates that defensive medicine practised because of legal fears costs the state at least $702 million annually, spending that is bound to continue as long as one lawsuit is filed annually for every 5.3 doctors in the state. PMID:7553498

  1. San Antonio, Texas, USA

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This sharp, cloud free view of San Antonio, Texas (29.5N, 98.5W) illustrates the classic pattern of western cities. The city has a late nineteenth century Anglo grid pattern overlaid onto an earlier, less regular Hispanic settlement. A well marked central business district having streets laid out north/south and east/west is surrounded by blocks of suburban homes and small businesses set between the older colonial radial transportation routes.

  2. Corpus Christi, Texas

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This near vertical view of the south Texas coast shows the city of Corpus Christi (28.0N, 97.0W) and Corpus Christi Bay. Mustang Island and the Gulf of Mexico are seen in the Southeast corner of the view. The Nueces River flows into the bay from the west. The light toned squiggly lines in Corpus Christi Bay are mud trails caused by shrimp boats dragging their nets along the shallow bottom of the bay.

  3. Stable isotope (C and N) and sedimentary facies analyses of the Cantwell Formation, Denali National Park, Alaska as indicators of Maastrichtian paleoenvironment

    NASA Astrophysics Data System (ADS)

    Salazar Jaramillo, S.; Fowell, S. J.; Wooller, M. J.; Mccarthy, P. J.; Benowitz, J.

    2012-12-01

    Sedimentary facies and stable isotope analyses of Lower Cantwell Formation outcrops on the East Fork of the Toklat River in Denali National Park, Alaska, reveal a correlation between positive δ13C excursions and carbonaceous facies. 238U/206Pb zircon dating of a bentonite layer from our measured sections yields a crystallization age of 69.5 ± 0.69 Ma, indicating that dinosaur tracks identified in this part of the Cantwell Formation are of early Maastrichtian age. This date establishes the coeval nature of dinosaur bones from the Prince Creek Formation on Alaska's North Slope, allows reconstruction of Late Cretaceous climate gradients, and brackets the age of the Lower Cantwell-Upper Cantwell unconformity (~69 Ma to ~60 Ma) linked to the final docking of the Wrangell Composite Terrane. The Late Cretaceous Cantwell Formation is composed of nonmarine sandstone, siltstone, shale, carbonaceous mudstone and, locally, weakly developed paleosols. Facies associations are interpreted as levees, crevasse channels, crevasse splays, and floodplains, which were part of an anastomosed river system. δ13C, δ15N, C/N and TOC values of bulk organic matter were measured in order to reconstruct the local paleoenvironment and facilitate chemostratigraphic correlation with dinosaur-bearing strata on Alaska's North Slope. C/N ratios fall between 5 and 33, indicating that the organic matter is likely comprised of terrestrial plants and lacustrine algae. Throughout the 123 m section, δ13C values of bulk organic matter from sandstone, siltstone, and shale range between -27.1 and -24.9‰. Wood fragments and bulk organic samples from carbonaceous mudstone have higher TOC values and more positive δ13C values, ranging from -24.1 to -22.4‰. Positive δ13C excursions could reflect one or a combination of: 1) changes in composition of the vegetation (e.g., conifers vs. more mixed organic matter); 2) changes in sources of organic material (lacustrine vs. terrestrial); 3) changes in past

  4. Depositional environments of Pottsville sandstones and conglomerates in Alabama

    SciTech Connect

    Demirpolat, S. )

    1988-08-01

    The Pennsylvanian Pottsville Formation in the Cahaba Basin, Alabama, is structurally in the Cahaba synclinorium in the Appalachian fold and thrust belt. The formation consists of a sequence of conglomerates, sandstones, siltstones, mudstones, and coals, more than 3 km thick. The sandstones are well cemented (with silica) and/or square textured. Polymictic conglomerates are present in the middle and upper parts (Straven and post-Straven). The conglomerates contain pebbles and cobbles of quartz, metamorphic rocks, and sedimentary rocks up to 25 cm in diameter, and thus differ from conglomeratic sandstone in the Shades Sandstone Member, which contains only small and well-rounded white quartz pebbles. These first and second cycle (or multicycle), sheared, pocked, and half-round pebbles were cut by faulting and ground against each other after deposition. Sheared and pocked pebbles typically develop where sand matrix is not abundant; single pebbles floating in sandstone rarely show these fractures. Over 2,000 measured pebble imbrications indicate that sandstone members are in large part marine and probably were deposited on a beach and/or migrating shoals. Cross-beds suggest primary and secondary transport directions to the northwest and southwest, respectively. Study of Pennsylvanian paleowind patterns (relative to the continental position and orientation) and of symmetric and asymmetric ripple marks suggests that paleotransport was to the northwest and that the shoreline was oriented northeast-southwest. Crossplots of neutron vs. density logs yield an average of 4-5% porosity for these quartzites.

  5. Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Ming, D. W.; Yen, A. S.; Rampe, E. B.; Grotzinger, J. P.; Blake, D. F.; Bristow, T. F.; Chipera, S. J.; Downs, R.; Morris, R. V.; Morrison, S. M.; Vaniman, D. T.; Gellert, R.; Sutter, B.; Treiman, A. H.

    2016-01-01

    The Mars Science Laboratory rover Curiosity has been exploring sedimentary deposits in Gale crater since August 2012. The rover has traversed up section through approx.100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation lies unconformable over a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Mineralogy of the unaltered Stimson sandstone consists of plagioclase feldspar, pyroxenes, and magnetite with minor abundances of hematite, and Ca-sulfates (anhydrite, bassanite). Unaltered sandstone has a composition similar to the average Mars crustal composition. Alteration "halos" occur adjacent to fractures in the Stimson. Fluids passing through these fractures have altered the chemistry and mineralogy of the sandstone. Silicon and S enrichments and depletions in Al, Fe, Mg, Na, K, Ni and Mn suggest aqueous alteration in an open hydrologic system. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes, but less abundant in the altered compared to the unaltered Stimson sandstone and lower pyroxene/plagioclase feldspar. The mineralogy and geochemistry of the altered sandstone suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

  6. Elements of high constructive deltaic sedimentation, lower Frio Formation, Brazoria County, Texas

    SciTech Connect

    Tyler, N.; Han, J.H.

    1982-01-01

    The lower Frio Formation in eastern Brazoria County, upper Texas Gulf Coast, was deposited in a high constructive deltaic environment in the Houston delta system. Constructive elements of the stacked, elongate to lobate deltas that were intersected in core are storm induced delta front splays, delta front slump deposits, and distributary mouth bar, distributary channel and delta plain assemblages. Reworked and winnowed abandonment facies that are volumetrically insignificant relative to constructive elements are subdivided into a crossbedded shoreface-foreshore subfacies and a fine grained cyclic sequence of storm deposits on the lower shoreface that represent a distal abandonment subfacies. Micropaleontological evidence indicates that deposition of constructive and abandonment facies took place in water depths of less than 120 feet.

  7. Depositional facies and Hohokam settlement patterns of Holocene alluvial fans, N. Tucson Basin, Arizona

    SciTech Connect

    Field, J.J.

    1985-01-01

    The distribution of depositional facies on eight Holocene alluvial fans of varying dimensions is used to evaluate prehistoric Hohokam agricultural settlement patterns. Two facies are recognized: channel gravelly sand facies and overbank silty sand facies. No debris flow deposits occur. The channel facies is characterized by relatively well sorted stratified sands and gravels with common heavy mineral laminations. Overbank facies deposits are massive and very poorly sorted due to heavy bioturbation. Lithostratigraphic profiles from backhoe trenches and sediment size analysis document headward migration of depositional facies which results in fining upward sequences. Each sequence is a channel fan lobe with an underlying coarse grained channel sand which fines to overbank silty sands. Lateral and vertical variations in facies distributions show that depositional processes are affected by drainage basin area (fan size) and distance from fan head. Gravelly channel sands dominate at the headward portions of the fan and are more pervasive on large fans; overbank silty sands are ubiquitous at fan toes and approach closer to the fan head of smaller alluvial fans. When depositional facies are considered as records of water flow over an alluvial surface, the farming potential of each fan can be analyzed. Depositional models of alluvial fan sedimentation provide the basis for understanding Hohokam settlement patterns on active alluvial surfaces.

  8. Abandoned Texas oil fields

    SciTech Connect

    Not Available

    1980-12-01

    Data for Texas abandoned oil fields were primarily derived from two sources: (1) Texas Railroad Commission (TRRC), and (2) Dwight's ENERGYDATA. For purposes of this report, abandoned oil fields are defined as those fields that had no production during 1977. The TRRC OILMASTER computer tapes were used to identify these abandoned oil fields. The tapes also provided data on formation depth, gravity of oil production, location (both district and county), discovery date, and the cumulative production of the field since its discovery. In all, the computer tapes identified 9211 abandoned fields, most of which had less than 250,000 barrel cumulative production. This report focuses on the 676 abandoned onshore Texas oil fields that had cumulative production of over 250,000 barrels. The Dwight's ENERGYDATA computer tapes provided production histories for approximately two-thirds of the larger fields abandoned in 1966 and thereafter. Fields which ceased production prior to 1966 will show no production history nor abandonment date in this report. The Department of Energy hopes the general availability of these data will catalyze the private sector recovery of this unproduced resource.

  9. Application of Advanced Reservoir Characterization, Simulation, and Production Optimization Strategies to Maximize Recovery in Slope and Basin Clastic Reservoirs, West Texas (Delaware Basin), Class III

    SciTech Connect

    Dutton, Shirley P.; Flanders, William A.; Mendez, Daniel L.

    2001-05-08

    The objective of this Class 3 project was demonstrate that detailed reservoir characterization of slope and basin clastic reservoirs in sandstone's of the Delaware Mountain Group in the Delaware Basin of West Texas and New Mexico is a cost effective way to recover oil more economically through geologically based field development. This project was focused on East Ford field, a Delaware Mountain Group field that produced from the upper Bell Canyon Formation (Ramsey sandstone). The field, discovered in 9160, is operated by Oral Petco, Inc., as the East Ford unit. A CO2 flood was being conducted in the unit, and this flood is the Phase 2 demonstration for the project.

  10. Application of Advanced Reservoir Characterization, Simulation, and Production Optimization Strategies to Maximize Recovery in Slope and Basin Clastic Reservoirs, West Texas (Delaware Basin), Class III

    SciTech Connect

    Dutton, Shirley P.; Flanders, William A.

    2001-11-04

    The objective of this Class III project was demonstrate that reservoir characterization and enhanced oil recovery (EOR) by CO2 flood can increase production from slope and basin clastic reservoirs in sandstones of the Delaware Mountain Group in the Delaware Basin of West Texas and New Mexico. Phase 1 of the project, reservoir characterization, focused on Geraldine Ford and East Ford fields, which are Delaware Mountain Group fields that produce from the upper Bell Canyon Formation (Ramsey sandstone). The demonstration phase of the project was a CO2 flood conducted in East Ford field, which is operated by Orla Petco, Inc., as the East Ford unit.

  11. Facies and depositional architecture according to a jet efflux model of a late Paleozoic tidewater grounding-line system from the Itararé Group (Paraná Basin), southern Brazil

    NASA Astrophysics Data System (ADS)

    Aquino, Carolina Danielski; Buso, Victoria Valdez; Faccini, Ubiratan Ferrucio; Milana, Juan Pablo; Paim, Paulo Sergio Gomes

    2016-04-01

    During the Late Paleozoic, the Gondwana supercontinent was affected by multiple glacial and deglacial episodes known as "The Late Paleozoic Ice Age" (LPIA). In Brazil, the evidence of this episode is recorded mainly by widespread glacial deposits preserved in the Paraná Basin that contain the most extensive record of glaciation (Itararé Group) in Gondwana. The Pennsylvanian to early Permian glaciogenic deposits of the Itararé Group (Paraná Basin) are widely known and cover an extensive area in southern Brazil. In the Doutor Pedrinho area (Santa Catarina state, southern Brazil), three glacial cycles of glacier advance and retreat were described. The focus of this article is to detail the base of the second glacial episodes or Sequence II. The entire sequence records a deglacial system tract that is represented by a proximal glacial grounding-line system covered by marine mudstones and shales associated with a rapid flooding of the proglacial area. This study deals with the ice proximal grounding-line systems herein interpreted according to lab model named plane-wall jet with jump. Detailed facies analysis allowed the identification of several facies ranging from boulder-rich conglomerates to fine-grained sandstones. No fine-grained deposits such as siltstone or shale were recorded. According to this model, the deposits are a product of a supercritical plane-wall outflow jet that changes to a subcritical jet downflow from a hydraulic jump. The hydraulic jump forms an important energy boundary that is indicated by an abrupt change in grain size and cut-and-fill structures that occur at the middle-fan. The sedimentary facies and facies associations show a downflow trend that can be subdivided into three distinct stages of flow development: (1) a zone of flow establishment (ZFE), (2) a zone of transition (ZFT), and (3) an established zone (ZEF). The proximal discharge is characterized by hyperconcentrated-to-concentrated flow due to the high energy and sediment

  12. Depositional sequence stratigraphy and architecture of the cretaceous ferron sandstone: Implications for coal and coalbed methane resources - A field excursion

    USGS Publications Warehouse

    Garrison, J.R., Jr.; Van Den, Bergh, T. C. V.; Barker, C.E.; Tabet, D.E.

    1997-01-01

    This Field Excursion will visit outcrops of the fluvial-deltaic Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale, known as the Last Chance delta or Upper Ferron Sandstone. This field guide and the field stops will outline the architecture and depositional sequence stratigraphy of the Upper Ferron Sandstone clastic wedge and explore the stratigraphic positions and compositions of major coal zones. The implications of the architecture and stratigraphy of the Ferron fluvial-deltaic complex for coal and coalbed methane resources will be discussed. Early works suggested that the southwesterly derived deltaic deposits of the the upper Ferron Sandstone clastic wedge were a Type-2 third-order depositional sequence, informally called the Ferron Sequence. These works suggested that the Ferron Sequence is separated by a type-2 sequence boundary from the underlying 3rd-order Hyatti Sequence, which has its sediment source from the northwest. Within the 3rd-order depositional sequence, the deltaic events of the Ferron clastic wedge, recognized as parasequence sets, appear to be stacked into progradational, aggradational, and retrogradational patterns reflecting a generally decreasing sediment supply during an overall slow sea-level rise. The architecture of both near-marine facies and non-marine fluvial facies exhibit well defined trends in response to this decrease in available sediment. Recent studies have concluded that, unless coincident with a depositional sequence boundary, regionally extensive coal zones occur at the tops of the parasequence sets within the Ferron clastic wedge. These coal zones consist of coal seams and their laterally equivalent fissile carbonaceous shales, mudstones, and siltstones, paleosols, and flood plain mudstones. Although the compositions of coal zones vary along depositional dip, the presence of these laterally extensive stratigraphic horizons, above parasequence sets, provides a means of correlating and defining the tops

  13. Geologic and Engineering Characterization of East Ford Field, Reeves County, Texas

    SciTech Connect

    Dutton, Shirley P.; Flanders, William A.; Guzman, Jose I.; Zirczy, Helena

    1999-08-16

    The objective of this Class III project is to demonstrate that detailed reservoir characterization of slope and basin clastic reservoirs in sandstones of the Delaware Mountain Group in the Delaware Basin of West Texas and New Mexico is a cost-effective way to recover a higher percentage of the original oil in place through geologically based field development. The project focused on reservoir characterization of the East Ford unit, a representative Delaware Mountain Group field that produces from the upper Bell Canyon Formation (Ramsey Sandstone). The field, discovered in 1960, is operated by Oral Petco, Inc., as the East Ford unit: it contained an estimated 18.4 million barrels (MMbbl) of original oil in place.

  14. Dynamic triggering during rupture nucleation in sandstone

    NASA Astrophysics Data System (ADS)

    Schubnel, Alexandre; Chanard, Kristel; Latour, Soumaya; Petrelis, François; Hatano, Takahiro; Mair, Karen; Vinciguerra, Sergio

    2016-04-01

    Fluid induced stress perturbations in the crust at seismogenic depths can be caused by various sources, such as deglaciation unloading, magmatic intrusion or fluid injection and withdrawal. Numbers of studies have robustly shown their link to earthquake triggering. However, the role of small periodic stress variations induced by solid earth and oceanic tides or seasonal hydrology in the seismic cycle, of the order of a few kPa, remains unclear. Indeed, the existence or absence of correlation between these loading phenomena and earthquakes have been equally proposed in the literature. To investigate this question, we performed a set of triaxial deformation experiments on porous water-saturated Fontainebleau sandstones. Rock samples were loaded by the combined action of steps of constant stress (creep), intended to simulate tectonic loading and small sinusoidal pore pressure variations with a range of amplitudes, analogous to tides or seasonal loading. All tests were conducted at a regulated temperature of 35C and a constant 35 MPa confining pressure. Our experimental results show that (1) pore pressure oscillations do not seem to influence the deformation rate at which the rock fails, (2) they correlate with acoustic emissions. Even more interestingly, we observe a progressive increase of the correlation coefficient in time as the rock approaches failure. The correlation coefficient is also sensitive to the amplitude of pore pressure oscillations as larger oscillations produce higher correlation levels. Finally, we show that, in the last hours of creep before failure, acoustic emissions occur significantly more when the pore pressure is at its lowest. This suggest that the correlation of small stress perturbations and acoustic emissions depend on the state stress of a rock and the amplitude of the perturbations and that emissions occur more likely when cracks are unclamped.

  15. Biogenic caliches in Texas: The role of organisms and effect of climate

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Chafetz, Henry S.

    2009-12-01

    Biogenic constituents are ubiquitous and abundant in the caliches of Texas. Investigation of 51 caliche profiles on various host strata (alluvium, limestone, igneous rocks, etc.) across approximately 900 km of Texas from subhumid east to arid west has shown that 43 of these profiles exhibit prominent biogenic constituents. These profiles exhibit significant differences in thickness (varying from centimeters to meters) and maturity (varying from I to VI). All of the different caliche facies are composed of low-Mg calcite. Biogenic features generally occur in the upper part of the profiles, including the uppermost portion of massive caliche horizons, platy horizons, laminar crusts, and pisoids. The main biogenic caliche facies include rhizoliths (calcified root structures), stromatolite-like laminar crusts, and coated grains. Compared to the abiogenic massive micritic to microsparitic calcite groundmass, biogenic constituents are morphologically distinct. These biogenic constituents are composed of several microscopic mineral components, including calcified filaments, needle fiber calcite (e.g., single crystalline needles and needle pairs, triangular crystals, and polycrystalline chains of rhombohedrons), spherulites, micro-rods, and nano-spheres. A large number of calcified root cellular structures and micro-organisms, e.g., fungal filaments, actinomycetes, and rod-like bacteria, are also present. Plant roots as well as soil biota produce distinctive structures and also enhance lithification by inducing calcite precipitation in the caliches, i.e., biologically controlled or influenced processes. Host strata did not significantly influence the abundance nor type of biogenic features in the caliches. In contrast, climate had an evident effect on the development of biogenic constituents in these caliches in terms of the amount as well as type. The thickness of laminar crusts and grain coatings and the abundance of biotic constituents within those facies decrease as the

  16. Alisitos Formation calcareous facies - Early Cretaceous episode of tectonic calm

    SciTech Connect

    Suarez-Vidal, F.

    1986-04-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of Baja California bounding the Peninsula Range batholith. Lithologically, this formation is formed by volcanic breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic barrier reef behind an island arc. Such conditions pertained south of the Agua Blanca fault and extended to El Arco, Baja California. Based on field observation and petrologic analysis in the Alisitos limestone, an attempt has been made to re-create the environmental condition in the Punta China and San Fernando, Baja California, sites.

  17. Sedimentary Facies Analysis Using AVIRIS Data: A Geophysical Inverse Problem

    NASA Technical Reports Server (NTRS)

    Boardmann, Joe W.; Goetz, Alexander F. H.

    1990-01-01

    AVIRIS data can be used to quantitatively analyze and map sedimentary lithofacies. The observed radiance spectra can be reduced to 'apparent reflectance' spectra by topographic and reflectance characterization of several field sites within the image. These apparent reflectance spectra correspond to the true reflectance at each pixel, multiplied by an unknown illumination factor (ranging in value from zero to one). The spatial abundance patterns of spectrally defined lithofacies and the unknown illumination factors can be simultaneously derived using constrained linear spectral unmixing methods. Estimates of the minimum uncertainty in the final results (due to noise, instrument resolutions, degree of illumination and mixing systematics) can be made by forward and inverse modeling. Specific facies studies in the Rattlesnake Hills region of Wyoming illustrate the successful application of these methods.

  18. Alisitos Formation, calcareous facies: Early Cretaceous episode of tectonic calm

    SciTech Connect

    Suarez-Vidal, F.

    1986-07-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of the peninsula of Baja California bounding the Peninsular Range batholith. Lithologically, this formation is formed by volcanic-breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during the tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic reef barrier, behind an island arc. Such conditions existed south of the Agua Blanca fault and extended to El Arco, Baja California. Based upon field observations and petrological analysis of the Alisitos limestone, an attempt is made to recreate the environmental condition in the Punta China and San Fernando, Baja California, sites.

  19. Post-granulite facies fluid infiltration in the Adirondack Mountains

    SciTech Connect

    Morrison, J.; Valley, J.W.

    1988-06-01

    Granulite facies lithologies from the Adirondack Mountains of New York contain alteration assemblages composed dominantly of calcite +/- chlorite +/- sericite. These assemblages document fluid infiltration at middle to upper crustal levels. Cathodoluminescence of samples from the Marcy anorthosite massif indicates that the late fluid infiltration is more widespread than initially indicated by transmitted-light petrography alone. Samples that appear unaltered in transmitted light show extensive anastomosing veins of calcite (< 0.05 mm wide) along grain boundaries, in crosscutting fractures, and along mineral cleavages. The presence of the retrograde calcite documents paleopermeability in crystalline rocks and is related to the formation of high-density CO/sub 2/-rich fluid inclusions. Recognition of this process has important implications for studies of granulite genesis and the geophysical properties of the crust.

  20. Prima facie evidence against spin-two Higgs impostors

    NASA Astrophysics Data System (ADS)

    Ellis, John; Sanz, Verónica; You, Tevong

    2013-10-01

    The new particle X recently discovered by the ATLAS and CMS Collaborations is widely expected to have spin zero, but this remains to be determined. The leading alternative is that X has spin two, presumably with graviton-like couplings. We show that measurements of the X particle to pairs of vector bosons constrain such scenarios. In particular, a graviton-like Higgs impostor in scenarios with a warped extra dimension of AdS type is prima facie excluded, principally because they predict too small a ratio between the X couplings to WW and ZZ, compared with that to photons. The data also disfavour universal couplings to pairs of photons and gluons, which would be predicted in a large class of graviton-like models.

  1. Solar Hot Water for Motor Inn--Texas City, Texas

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Final report describes solar domestic-hot-water heater installation at LaQuinta Motor Inn, Texas City, Texas which furnished 63% of total hot-water load of new 98-unit inn. Report presents a description of system, drawings and photographs of collectors, operations and maintenance instructions, manufacturers' specifications for pumps, and an engineer's report on performance.

  2. Influence of carbonate facies on fault zone architecture

    NASA Astrophysics Data System (ADS)

    Michie, E. A. H.; Haines, T. J.; Healy, D.; Neilson, J. E.; Timms, N. E.; Wibberley, C. A. J.

    2014-08-01

    Normal faults on Malta were studied to analyse fault propagation and evolution in different carbonate facies. Deformation of carbonate facies is controlled by strength, particle size and pore structure. Different deformation styles influence the damage characteristics surrounding faults, and therefore the fault zone architecture. The carbonates were divided into grain- and micrite-dominated carbonate lithofacies. Stronger grain-dominated carbonates show localised deformation, whereas weaker micrite-dominated carbonates show distributed deformation. The weaker micrite-dominated carbonates overlie stronger grain-dominated carbonates, creating a mechanical stratigraphy. A different architecture of damage, the ‘Fracture Splay Zone’ (FSZ), is produced within micrite-dominated carbonates due to this mechanical stratigraphy. Strain accumulates at the point of juxtaposition between the stronger grain-dominated carbonates in the footwall block and the weaker micrite-dominated carbonates in the hanging wall block. New slip surfaces nucleate and grow from these points, developing an asymmetric fault damage zone segment. The development of more slip surfaces within a single fault zone forms a zone of intense deformation, bound between two slip surfaces within the micrite-dominated carbonate lithofacies (i.e., the FSZ). Rather than localisation onto a single slip surface, allowing formation of a continuous fault core, the deformation will be dispersed along several slip surfaces. The dispersed deformation can create a highly permeable zone, rather than a baffle/seal, in the micrite-dominated carbonate lithofacies. The formation of a Fracture Splay Zone will therefore affect the sealing potential of the fault zone. The FSZ, by contrast, is not observed in the majority of the grain-dominated carbonates.

  3. Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton

    SciTech Connect

    van Houten, F.B.

    1980-06-01

    Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing distribution, facies, and thickness of relevant sequences are adequate for the three northern basins only. High detrital influx near the end of Jurassic time and in mid-Cretaceous time produced regressive nubian facies composed largely of low-sinuosity stream and fahdelta deposits. In the west and southwest the Ghadames, Murzuk, and Kufra basins were filled with a few hundred meters of detritus after long-continued earlier Mesozoic aggradation. In northern Egypt the regressive sequence succeeded earlier Mesozoic marine sedimentation; in the Sirte and Southern basins correlative deposits accumulated on Precambrian and Variscan terranes after earlier Mesozoic uplift and erosion. Waning of detrital influx into southern Tunisia and adjacent Libya in the west and into Israel in the east initiated an Albian to early Cenomanian transgression of Tethys. By late Cenomanian time it had flooded the entire cratonic margin, and spread southward into the Murzuk and Southern basins, as well as onto the Arabo-Nubian shield. Latest Jurassic-earliest Cretaceous, mid-Cretaceous, and Late Cretaceous transgressions across northeastern Africa recorded in these sequences may reflect worldwide eustatic sea-level rises. In contrast, renewed large supply of detritus during each regression and a comparable subsidence history of intracratonic and marginal basins imply regional tectonic control. 6 figures.

  4. Biostratigraphy of Albian-Cenomanian boundary in Texas and implications for middle Cretaceous stratigraphy elsewhere in North America

    SciTech Connect

    Stein, J.A.; Ravn, R.L.; Wood, G.D. )

    1987-02-01

    On the basis of comparison of ammonite zonations in Texas and western Europe, the Albian-Cenomanian boundary in Texas is placed in the lower part of the Grayson Formation of the Washita Group. This position contrasts with the Comanchean-Gulfian Series boundary, normally placed at the top of the Washita Group. Comparison of polynomorphs from the Grayson and associated strata with those of other North American middle Cretaceous units reveals inconsistencies in the designations of Albian ages in other areas. Spore-pollen assemblages from the subsurface Dantzler Formation in Mississippi and Louisiana (previously considered Albian) include age-diagnostic taxa characteristic of the Maness and lower Woodbine formations (Cenomanian) in Texas. The Albian-Cenomanian boundary therefore occurs at a major unconformity between the Dantzler and underlying Fredericksburg Group, rather than at the unconformable top of the Dantzler, below Tuscaloosa Group sandstones. Palynology also indicates correlation of the type Dakota Formation of Nebraska and Iowa to the Cenomanian Maness-Woodbine in Texas, overlying the major middle Cretaceous unconformity. In northern Arizona, the Dakota Sandstone contains a Cenomanian assemblage similar to that of the type Dakota, but in Wyoming and Colorado, units traditionally referred to the Dakota Group (e.g., Muddy formation) are clearly Albian in age, and lie below the middle Cretaceous unconformity. These correlations shed new light on the sedimentary and stratigraphic relationships of unconformities and lithologic units in the middle Cretaceous of central and western North America.

  5. Overview: Research Funding in Texas

    ERIC Educational Resources Information Center

    Texas Higher Education Coordinating Board, 2009

    2009-01-01

    Obtaining more federal funds is the expressed research goal in "Closing the Gaps by 2015." It states: By 2015, increase the level of federal science and engineering research and development obligations to Texas institutions to 6.5 percent of obligations to higher education institutions across the nation. In 2006, Texas institutions of higher…

  6. Texas Education Miracle No Mirage.

    ERIC Educational Resources Information Center

    Greene, Jay P.

    2000-01-01

    Defends the significant increases seen in Texas student achievement during the 1990s, addressing attacks on the validity of these improvements. Supports the governor's emphasis on accountability testing because of its positive results, concluding that the Texas Assessment of Academic Skills holds students and schools accountable and provides…

  7. Rice blast disease in Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice is an important agricultural commodity in Texas, with an economic impact of more than $1 billion annually. Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases in rice. Texas Rice Belt provides a warm, humid climate favorable for the infection and reproduction of M....

  8. Alternative Teacher Certification in Texas.

    ERIC Educational Resources Information Center

    Texas Education Agency, Austin.

    This publication describes alternative teacher certification programs in Texas that train interns who are generally mature, mid-career individuals. The document is organized into seven sections: (1) "Alternative Certification in Texas" discusses the history and background of the programs including legislation, the first alternative teacher…

  9. Texas Coastal Cleanup Report, 1986.

    ERIC Educational Resources Information Center

    O'Hara, Kathryn; And Others

    During the 1986 Coastweek, a national event dedicated to improvement of the marine environment, a large beach cleanup was organized on the Texas coast. The goals of the cleanup were to create public awareness of the problems caused by marine debris, and to collect data on the types and quantities of debris found on the Texas coastline. The…

  10. Tertiary age for upper Nubian sandstone formation, central Sudan

    SciTech Connect

    Prasad, G.; Lejal-Nicol, A.; Vaudois-Mieja, N.

    1986-02-01

    In central and northern Sudan, oil exploration is now active in the basins containing sediments of the Nubian Sandstone Formation. On the evidence of planned pipeline construction, significant volumes of oil appear to have been discovered in southwestern Sudan. A newly discovered flora from the upper Nubian Sandstone Formation near Khartoum in central Sudan is Tertiary in age. The flora is well preserved, and comprises leaves, flowers, and fruits, many not yet described. At the generic level, they are comparable to forms that are known fro the Eocene to Miocene. Aquatic plants indicate a lacustrine paleoenvironment; humid tropical forests thrived on the lakeshores. The Nubian Sandstone Formation of Sudan had been considered to be entirely of Cretaceous age; this new flora shifts the upper boundary into the Tertiary. The Tertiary Hudi Chert, found in scattered outcrops in the region of Atbara, was considered to overlie the Nubian Sandstone Formation. The authors suggest that the Hudi Chert is partly age equivalent to the Tertiary upper Nubian Sandstone at Jebel Mudaha.

  11. Numerical analysis of sandstone composition, provenance, and paleogeography

    SciTech Connect

    Smosma, R.; Bruner, K.R.; Burns, A.

    1999-09-01

    Cretaceous deltaic sandstones of the National Petroleum Reserve in Alaska exhibit an extreme variability in their mineral makeup. A series of numerical techniques, however, provides some order to the petrographic characteristics of these complex rocks. Ten mineral constituents occur in the sandstones, including quartz, chert, feldspar, mica, and organic matter, plus rock fragments of volcanics, carbonates, shale, phyllite, and schist. A mixing coefficient quantities the degree of heterogeneity in each sample. Hierarchical cluster analysis then groups sandstones on the basis of similarities among all ten mineral components--in the Alaskan example, six groupings characterized mainly by the different rock fragments. Multidimensional scaling shows how the clusters relate to one another and arranges them along compositional gradients--two trends in Alaska based on varying proportions of metamorphic/volcanic and shale/carbonate rock fragments. The resulting sandstone clusters and petrographic gradients can be mapped across the study area and compared with the stratigraphic section. This study confirms the presence of three different source areas that provided diverse sediment to the Cretaceous deltas as well as the general transport directions and distances. In addition, the sand composition is shown to have changed over time, probably related to erosional unroofing in the source areas. This combination of multivariate-analysis techniques proves to be a powerful tool, revealing subtle spatial and temporal relationships among the sandstones and allowing one to enhance provenance and paleogeographic conclusions made from compositional data.

  12. Development of Shear Banding in Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Riedel, J. J.; Labuz, J. F.

    2004-05-01

    Closed-loop, servo-controlled testing was used to investigate the development of shear failure in Berea sandstone under low confining pressure. The experiments were performed with the University of Minnesota Plane-Strain Apparatus, designed to allow the failure plane to propagate in an unrestricted manner. Deformation was imposed into the strain softening regime and controlled so that the specimens remained intact. Thin-section microscopy provided direct observation in, adjacent to, and around the tip of the rupture zone. The shear band appeared to initiate near a stress concentration, either the corner of the specimen or, when present, an imperfection (3 mm diameter hole) introduced into the specimen. Intragranular microcracking was the dominant observable failure mechanism. The intensity of grain cracking was greatest near the initiation point and decreased as the failure surface was traced towards the tip. Areas of high crack density also appeared to have the greatest amount of grain size reduction and there seemed to be a larger amount of pore space. In areas where intragranular microcracks were distinguishable, (e.g. near the tip of the rupture zone), microcracks showed very little or no shear displacement, suggesting the features were not reoriented after formation. Microcrack orientations showed a dominant direction of -16 degrees from the maximum principal stress direction and -26 degrees from the failure surface. A numerical imaging technique was developed to provide an efficient means for analyzing the relative porosity of epoxy-impregnated thin-sections. The code was set up to receive a digital image (*.bmp), where three parameters (R, G, and B) describe the color of each pixel. The intensity of the R channel consistently defined the boundary of grain and pore space and was used to differentiate blue pore space from the white grains composing the matrix. Porosity increase within the rupture zone was 3-4 grain diameters wide. An absence of notable

  13. Ionic surface electrical conductivity in sandstone

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Meredith, Philip G.; Sammonds, Peter R.; Murrell, Stanley A. F.

    1994-11-01

    Recent analyses of complex conductivity measurements have indicated that high-frequency dispersions encountered in rocks saturated with low-salinity fluids are due to ionic surface conduction and that the form of these dispersions may be dependent upon the nature of the pore and crack surfaces within the rock (Ruffet et al., 1991). Unfortunately, the mechanisms of surface conduction are not well understood, and no model based on rigorous physical principles exists. This paper is split into two parts: an experimental section followed by the development of a theoretical description of adsorption of ions onto mineral surfaces. We have made complex conductivity measurements upon samples of sandstone saturated with a range of different types and concentrations of aqueous solution with a frequency range of 20 Hz to 1 MHz. The frequency dependence of complex conductivity was analyzed using the empirical model of Cole and Cole (1941). The 'fractal' surface models of Le Mehaute and Crepy (1983), Po Zen Wong (1987), the Ruffet el at. (1991) were used to calculate apparent fractal pore surface dimensions for samples saturated with different solution types and concentrations. These showed a pronounced decrease of apparent fractal surface dimension with decreasing electrolyte concentration and a decrease of apparent fractal dimension with increasing relative ionic radius of the dominant cation in solution. A model for ionic surface concentration (ISCOM I) has been developed as the first step in producing a rigorous physicochemical model of surface conduction in quartz-dominated rocks. The results from ISCOM I show that quartz surfaces are overwhelmingly dominated by adsorbed Na(+) when saturated with NaCl solutions of salinities and pH found in actual geological situations. ISCOM I also shows that the concentration threshold for dominance of surface conduction over bulk conduction is aided by depletion of ions from the bulk fluid as a result of their adsorption onto the mineral

  14. Depositional setting and vertebrate biostratigraphy of the Triassic Dockum Group of Texas

    NASA Astrophysics Data System (ADS)

    Lehman, Thomas; Chatterjee, Sankar

    2005-06-01

    Triassic strata of the Dockum Group in Texas comprise two major upward-fining alluvial-lacustrine depositional sequences. The two sequences are represented by the (1) Santa Rosa-Tecovas, and (2) Trujillo-Cooper Canyon Formations. The second sequence is much thicker than the first, and occupies a greater geographic part of the Dockum basin. Each sequence of alluvial and lacustrine sediment accumulation is characterized by sediment derivation from a different source terrain. The unconformable relationship between the two depositional sequences, the change in mineralogical composition and presumed source areas between these units, differences in paleocurrent orientation between units, and evidence for intervening episodes of local deformation indicate that the sequences are of tectonic origin. These strata are not the product of a single sediment dispersal system, such as the centripetally-drained lacustrine delta complex previously envisioned for the Dockum basin. Both Dockum sequences are comprised largely of two typical alluvial facies associations; stream channel facies, and overbank flood-plain facies, that are similar to those described in nearly all fluvial deposits. In addition, the Dockum Group contains a peculiar lacustrine facies that accumulated in local flood-plain depressions, and probably resulted from subsidence over areas of subsurface salt dissolution. Vertebrate fossil assemblages are found in all three Dockum facies associations. Five fossiliferous sites in the Dockum are discussed in the context of these three depositional settings. The Dockum tetrapod diversity is reviewed in a hierarchical phylogeny with remarks on the history of collection, stratigraphic distribution of genera, and their taxonomic status. The stratigraphic ranges of tetrapod taxa do not support the recently proposed successive Otischalkian, Adamanian, Revueltian, and Apachean biochrons within the Dockum Group. Instead, a few index fossils provide a broad framework for

  15. Lignite occurrence in relation to depositional facies, Eocene Wilcox group, Sabine uplift area, east Texas - regional and local comparative studies

    SciTech Connect

    Ambrose, M.L.; Jackson, M.L.W.; Kaiser, W.R.; Fly, D.J.

    1984-04-01

    Lignite occurrence was related to sandbody geometry in two subsurface studies: a 12-county regional study and a local study of the Trawick gas field area, north-central Nacogdoches County. For both studies, the Wilcox Group was informally divided into lower progradational (deltaic) and upper aggradational (fluvial) units. The local study utilized closely spaced data to investigate a more detailed Wilcox stratigraphy. The most continuous lignite-bearing zone lies at the transition between lower and upper Wilcox strata. Mapping of lignite occurrence in both studies shows this zone to be coincident with distributary channels indicative of delta-plain settings. Lignites and laterally equivalent muds rest on platforms of sandy sediments. Initiation of peat accumulation in interdistributary basins, with upward and subsequent lateral development as blanket peat, is inferred from the local study. Thickness and most laterally extensive seams occur in Shelby and Panola Counties on the flanks of major delta lobes. Thick upper Wilcox lignites (> 5 ft, 1.5 m) occur regionally between major fluvial channel sand belts and cap 30 to 40-ft (9 to 12-m) upward-coarsening sequences (crevasse splays.). These lignites are surface-mined in Panola and Harrison Counties at Martin Lake and Darco. Westward, in northern Cherokee County, our drilling shows thick lignites (up to 11 ft, 3.4 m) have limited lateral extent in channel sand belt areas. Similarly, the local study lies within a major sand belt; small interchannel basins limit lateral continuity of lignites.

  16. Case history - installation of high volume pumping equipment in Talco Field, Texas

    SciTech Connect

    Rose, J.D.

    1982-01-01

    The work presents a case history study of Exxon's high volume artificial lift program at Talco Field in Franklin and Titus Counties, Texas. The field produces heavy crude oil from the Paluxy sandstone at an approximate depth of 4200 ft. Discussion includes (1) screening parameters used to optimized selection of high volume artificial lift equipment; (2) representative production flowstreams to quantify the additional recovery expected; (3) analysis of incremental expenses and costs associated with electric submersible pumps and large capacity beam pumping units; and (4) case production histories and operational problems encountered.

  17. Feldspar diagenesis in the Frio Formation, Brazoria County, Texas Gulf Coast

    SciTech Connect

    Land, L.S.; Milliken, K.L.

    1981-07-01

    Tremendous quantities of detrital feldspar have been dissolved or albitized below about 14000 ft (4267 m) in the Frio Formation (Oligocene), Chocolate Bayou Field, Brazoria County, Texas. Some sandstones no longer contain any unmodified detrital feldspar grains. Material transfer involved in these reactions is immense, affecting at least 15% of the rock volume. Thus, albitization has important implications for several other diagenetic processes that involve feldspars or their components. These processes include formation of secondary porosity, precipitation of quartz and carbonate cements, and the evolution of Na-Ca-Cl formation water.

  18. A depositional model for late Jurassic Reef Building in the East Texas Basin

    SciTech Connect

    Norwood, E.M. ); Brinton, L. )

    1996-01-01

    The authors propose a depositional setting for the Upper Jurassic reef facies occurring at the upper Cotton Valley Lime, (Gilmer) sequence boundary in the East Texas Basin. The development of uncommonly thick, microbially bound reefal buildups positioned near the western margin of the basin was controlled by sea-level variations and gravity faulting, suggested to be concurrent. Gas bearing reefs occur as isolated features along faulted margins and have been successfully located using 3-D seismic. Reefs of this type and age appear to be rare in their occurrence worldwide. Structurally generated circumstances facilitated margin bypass of terrigenous clastics shed from the north and west. Protection from clastic influx contributed to conditions required for development of the 400 feet of reefal buildup penetrated by the Marathon Oil Company Poth No. 1 during early 1993. Core from this well provides insight into character, composition, and depositional setting of reefs along the western flank of the East Texas Basin during Late Jurassic time.

  19. A depositional model for late Jurassic Reef Building in the East Texas Basin

    SciTech Connect

    Norwood, E.M.; Brinton, L.

    1996-12-31

    The authors propose a depositional setting for the Upper Jurassic reef facies occurring at the upper Cotton Valley Lime, (Gilmer) sequence boundary in the East Texas Basin. The development of uncommonly thick, microbially bound reefal buildups positioned near the western margin of the basin was controlled by sea-level variations and gravity faulting, suggested to be concurrent. Gas bearing reefs occur as isolated features along faulted margins and have been successfully located using 3-D seismic. Reefs of this type and age appear to be rare in their occurrence worldwide. Structurally generated circumstances facilitated margin bypass of terrigenous clastics shed from the north and west. Protection from clastic influx contributed to conditions required for development of the 400 feet of reefal buildup penetrated by the Marathon Oil Company Poth No. 1 during early 1993. Core from this well provides insight into character, composition, and depositional setting of reefs along the western flank of the East Texas Basin during Late Jurassic time.

  20. Spatial Persistence of Macropores and Authigenic Clays in a Reservoir Sandstone: Implications for Enhanced Oil Recovery and CO2 Storage

    NASA Astrophysics Data System (ADS)

    Dewers, T. A.

    2015-12-01

    Multiphase flow in clay-rich sandstone reservoirs is important to enhanced oil recovery (EOR) and the geologic storage of CO2. Understanding geologic controls on pore structure allows for better identification of lithofacies that can contain, storage, and/or transmit hydrocarbons and CO2, and may result in better designs for EOR-CO2 storage. We examine three-dimensional pore structure and connectivity of sandstone samples from the Farnsworth Unit, Texas, the site of a combined EOR-CO2 storage project by the Southwest Regional Partnership on Carbon Sequestration (SWP). We employ a unique set of methods, including: robotic serial polishing and reflected-light imaging for digital pore-structure reconstruction; electron microscopy; laser scanning confocal microscopy; mercury intrusion-extrusion porosimetry; and relative permeability and capillary pressure measurements using CO2 and synthetic formation fluid. Our results link pore size distributions, topology of porosity and clay-rich phases, and spatial persistence of connected flow paths to multiphase flow behavior. The authors gratefully acknowledge the U.S. Department of Energy's National Energy Technology Laboratory for sponsoring this project through the SWP under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  1. Geologic Sequestration of CO2 and Associated H2S and SO2 in Bedded Sandstone-Shale Sequences

    NASA Astrophysics Data System (ADS)

    Xu, T.; Apps, J. A.; Pruess, K.

    2003-12-01

    The injection of CO2 and associated acid gases such as H2S and SO2 into deep sedimentary aquifers is a means by which net anthropogenic atmospheric emissions of greenhouse gases might be reduced. Aquifer host rock aluminosilicate minerals alter very slowly under ambient conditions and their study is not amenable to laboratory experiment. We therefore developed a numerical model to investigate the fate of CO2 and other acid gases in bedded sandstone-shale sequences using hydrogeologic properties and mineral compositions characteristic of Texas Gulf Coast sediments. The simulations were performed using the reactive fluid flow and geochemical transport code, TOUGHREACT, to analyze mass transfer between sandstone and shale layers, the consequent immobilization of gases through mineral precipitation, and the impact of co-contaminated H2S and SO2 gases on CO2 sequestration. The gas sequestration capacity by both aqueous and mineral phases was evaluated. Porosity changes due to mineral dissolution and precipitation were also monitored. The simulations provide useful insights into potential sequestration processes, and their controlling conditions and parameters during long-term containment of acid gases in deep sedimentary formations.

  2. The Texas We Create: State of Texas Children 2012--Texas KIDS COUNT Annual Data Book

    ERIC Educational Resources Information Center

    Deviney, Frances; Hattemer, Kori

    2012-01-01

    The 2012 data book explores how our kids have fared during the last decade--some outcomes are positive, some negative. But positive or negative outcomes for kids don't just happen. They are the inevitable results of effective or failed policy choices. The State of Texas Children 2012 combines data and policy to tell the story of Texas kids. It's…

  3. A Lower Ordovician sponge/algal facies in the southern United States and its counterparts elsewhere in North America

    SciTech Connect

    Alberstadt, L. ); Repetski, J.E. )

    1989-06-01

    Subsurface Ordovician rocks in the Black Warrior Basin, Mississippi Embayment, and the eastern part of the Arkoma Basin reflect a different depositional history than coeval rocks exposed in the Nashville Basin, Ozark Dome, and southern Appalachians. The succession consists of four informal lithologic units. From top to bottom these are: (1) Stones River limestones, (2) upper dolostone, (3) sponge/algal limestones characterized by the presence of Nuia, and (4) lower dolostone. Of these, the sponge/algal limestone unit is the most atypical. It has a conspicuous biotic assemblage which can be recognized petrographically in well cuttings. The diagnostic fossil allochems are: sponges, sponge spicules, Nuia, Girvanella, and Sphaerocodium. Conodonts from the sponge/algal limestones are probably entirely Early Ordovician (Canadian) and include cold- and deep-water species found in the North Atlantic Province, whereas those in the overlying dolostones represent exclusively warm-water, shelf environments. The conodonts in the Black Warrior Basin suggest that an unconformity between Lower and Middle Ordovician carbonates (Knox unconformity) does not exist in much of that region. The sponge/algal limestones represent a different facies than their coeval shelf rocks in the interior of the continent. The limestone contains a distinctive biotic assemblage recognized in Lower Ordovician rocks in Newfoundland, in the Arbuckle and Wichita mountains of Oklahoma, in West Texas, and in the Great Basin of Nevada and Utah.

  4. Fast evolving conduits in clay-bonded sandstone: Characterization, erosion processes and significance for the origin of sandstone landforms

    NASA Astrophysics Data System (ADS)

    Bruthans, Jiri; Svetlik, Daniel; Soukup, Jan; Schweigstillova, Jana; Valek, Jan; Sedlackova, Marketa; Mayo, Alan L.

    2012-12-01

    In Strelec Quarry, the Czech Republic, an underground conduit network > 300 m long with a volume of ~ 104 m3 and a catchment of 7 km2 developed over 5 years by groundwater flow in Cretaceous marine quartz sandstone. Similar landforms at natural exposures (conduits, slot canyons, undercuts) are stabilized by case hardening and have stopped evolving. The quarry offers a unique opportunity to study conduit evolution in sandstone at local to regional scales, from the initial stage to maturity, and to characterize the erosion processes which may form natural landforms prior to stabilization. A new technique was developed to distinguish erodible and non-erodible sandstone surfaces. Based on measurements of relative erodibility, drilling resistance, ambient and water-saturated tensile strength (TS) at natural and quarry exposures three distinct kinds of surfaces were found. 1) Erodible sandstone exposed at ~ 60% of surfaces in quarry. This sandstone loses as much as 99% of TS when saturated. 2) Sub-vertical fracture surfaces that are non-erodible already prior to exposure at ground surface and which keep considerable TS if saturated. 3) Case hardened surfaces that start to form after exposure. In favorable conditions they became non-erodible and reach the full TS in just 6 years. An increase in the hydraulic gradient from ~ 0.005 to > 0.02 triggered conduit evolution, based on long-term monitoring of water table in 18 wells and inflows to the quarry. Rapidly evolving major conduits are characterized by a channel gradient of ~ 0.01, a flow velocity ~ 40 cm/s and sediment concentration ~ 10 g/l. Flow in openings with a discharge 1 ml/s and hydraulic gradient > 0.05 exceeds the erosion threshold and initiates piping. In the first phase of conduit evolution, fast concentrated flow mobilizes erodible sandstone between sets of parallel fractures in the shallow phreatic zone. In the second phase the conduit opening mainly expands vertically upward into the vadose zone by mass

  5. Chapter 2. Assessment of undiscovered conventional oil and gas resources--Upper Jurassic-Lower Cretaceous Cotton Valley group, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

    USGS Publications Warehouse

    Dyman, T.S.; Condon, S.M.

    2006-01-01

    The Jurassic Smackover Interior Salt Basins Total Petroleum System is defined for this assessment to include (1) Upper Jurassic Smackover Formation carbonates and calcareous shales and (2) Upper Jurassic and Lower Cretaceous Cotton Valley Group organic-rich shales. The Jurassic Smackover Interior Salt Basins Total Petroleum System includes four conventional Cotton Valley assessment units: Cotton Valley Blanket Sandstone Gas (AU 50490201), Cotton Valley Massive Sandstone Gas (AU 50490202), Cotton Valley Updip Oil and Gas (AU 50490203), and Cotton Valley Hypothetical Updip Oil (AU 50490204). Together, these four assessment units are estimated to contain a mean undiscovered conventional resource of 29.81 million barrels of oil, 605.03 billion cubic feet of gas, and 19.00 million barrels of natural gas liquids. The Cotton Valley Group represents the first major influx of clastic sediment into the ancestral Gulf of Mexico. Major depocenters were located in south-central Mississippi, along the Louisiana-Mississippi border, and in northeast Texas. Reservoir properties and production characteristics were used to identify two Cotton Valley Group sandstone trends across northern Louisiana and east Texas: a high-permeability blanket-sandstone trend and a downdip, low-permeability massive-sandstone trend. Pressure gradients throughout most of both trends are normal, which is characteristic of conventional rather than continuous basin-center gas accumulations. Indications that accumulations in this trend are conventional rather than continuous include (1) gas-water contacts in at least seven fields across the blanket-sandstone trend, (2) relatively high reservoir permeabilities, and (3) high gas-production rates without fracture stimulation. Permeability is sufficiently low in the massive-sandstone trend that gas-water transition zones are vertically extensive and gas-water contacts are poorly defined. The interpreted presence of gas-water contacts within the Cotton Valley

  6. Plane shock wave studies of Westerly granite and Nugget sandstone

    SciTech Connect

    Larson, D.B.; Anderson, G.D.

    1980-12-01

    Plane shock wave experiments were performed by using a light-gas gun on dry and water-saturated Westerly granite and dry Nugget sandstone. Changes in the slopes of the shock velocity versus particle velocity curves at 2 to 3 GPa and 1 to 2 GPa for dry granite and for dry sandstone, respectively, are attributed to the onset of pore collapse. However, there is little apparent loss of shear strength in either dry rock over the stress range of the experiments (i.e., 9.3 GPa in Westerly granite and 9.2 GPa in Nugget sandstone). Agreement between the shock wave data and quasistatic, uniaxial strain data for the dry rock implies the absence of rate-dependence in uniaxial strain. The shock data on saturated granite agree well with those for dry granite, thus suggesting there was no loss in shear strength as a result of pore pressure buildup.

  7. Effective Thermal Conductivity Modeling of Sandstones: SVM Framework Analysis

    NASA Astrophysics Data System (ADS)

    Rostami, Alireza; Masoudi, Mohammad; Ghaderi-Ardakani, Alireza; Arabloo, Milad; Amani, Mahmood

    2016-06-01

    Among the most significant physical characteristics of porous media, the effective thermal conductivity (ETC) is used for estimating the thermal enhanced oil recovery process efficiency, hydrocarbon reservoir thermal design, and numerical simulation. This paper reports the implementation of an innovative least square support vector machine (LS-SVM) algorithm for the development of enhanced model capable of predicting the ETCs of dry sandstones. By means of several statistical parameters, the validity of the presented model was evaluated. The prediction of the developed model for determining the ETCs of dry sandstones was in excellent agreement with the reported data with a coefficient of determination value ({R}2) of 0.983 and an average absolute relative deviation of 0.35 %. Results from present research show that the proposed LS-SVM model is robust, reliable, and efficient in calculating the ETCs of sandstones.

  8. ``Tear drop pattern'' potash deposits in lacustrine facies

    NASA Astrophysics Data System (ADS)

    Sun, Dapeng

    1990-03-01

    It is well known that there are two patterns of potash deposition in lacustrine facies: “tear drop pattern” (the Dabsan saline lake is a typical example) and “bull's eye pattern”. Potash-forming in tear drop pattern is still continuing. The 2,678 m A. S. L. lake in the middle of the Qarhan playa in the Qaidam Basin covers an area of 210 km2, and has an average depth of 0.39 m. Its MgCl2 type surface brine is 280 340 g/l in salinity and mainly consists of Na, K, Mg and Cl. As a rule, the potash deposits occur as evaporite distributed in tear drop pattern at the northern and northeastern lakeshore zones. They mostly consist of carnallite and halite, occasionally sylvite. The deposition is very unstable and controlled principally by the varying supply of deposit materials from the Golmud River in the south. The potash deposits were formed when concentration of the surface brine reached a certain degree in the main evaporating season. Their forming process followed some crystalization paths in the phase diagram for the Na, K, Mg/Cl H2O equilibrium system. Such a sedimentary model of potash deposits in the lacustrine facies is relatively common in nature. Under the extremely arid climate, differential concentration of the nonhomogeneous potassium-rich surface brine produced the potash deposits. Qarhan Salt Lake also had the same pattern of potash depositions and so, in a sense, the Dabsan saline lake is the continuation of the Qarhan salt lake in terms of potash formation. Schmalz (1970) put forward two distributive patterns for evaporite: “tear drop pattern” and “bull's eye pattern”. These patterns exist in both marine and continental salt-bearing basins (including recent salt lakes), and are controlled by the conditions of physical geography, hydrogeology, sedimentology and climatology of each basin. In his works (Sun, 1981; 1984; 1986; 1988) on the origins of potash deposits, the author always referred to them as two models of potash formation. The

  9. National uranium resource evaluation: McAllen and Brownsville Quadrangles, Texas

    SciTech Connect

    Charepon, A J; Stauber, A J

    1982-06-01

    The McAllen and Brownsville Quadrangles, Texas, were evaluated to a depth of 1500 m to identify geologic environments and delineate areas favorable for uranium deposits. The environments were selected according to criteria established for the National Uranium Resource Evaluation program. Surface studies included investigations of uranium occurrences described in the literature, of locations of aerial radiometric anomalies, of surface exposures, and of locations of anomalous hydrogeochemical and stream-sediment reconnaissance data and collation of information on uranium exploration. Subsurface evaluation of selected geologic units was accomplished by using electric and gamma-ray well logs to construct maps and construct maps and cross sections. In the McAllen Quadrangle, an environment favorable for Texas roll-type sandstone uranium deposits is identified in 36 areas in the Goliad, Fleming-Oakville, Catahoula-Frio, and Whitsett Formations. All other units in both quadrangles are considered unfavorable.

  10. Petrocalcic paleosols, Hensel (Gillespie) Sand, Gillespie County, Texas

    SciTech Connect

    Wolff, E.C. ); Jones, J.O. . Geology Dept.); Amsbury, D.L.

    1993-02-01

    Paleocalcretes are common in all sediment types of the Hensel Sand in Gillespie County, Texas. Calcretes in mudstone are nodular, grading from rhizoconcretions to total replacement. In sandstone the paleosols tend to form undulating hardpans having cracked upper surfaces. Massive calcretes in basal conglomerates have greatly reduced the original permeability, restricting groundwater flow. Hensel Sand overlies upper Precambrian to Middle Pennsylvanian rocks; displacive crystallization of the calcitic globules and fibers was able to lift and displace 1m2 to 2m2 blocks of flaggy Upper Cambrian limestone in to spectacular teepee structures. Gillespie Sand is that portion of the basal Cretaceous Hensel Sand that stratigraphically overlies the middle Glen Rose Salenia/Corbula beds', and underlies upper Glen Rose or basal Fredericksburg rocks. It formed as non-marine valley fill during prolonged, episodic marine transgression. This study documents ubiquitous calcrete development in Central Texas during the lower part of the Middle Albian State; calcretes are now known from the Lower Aptian (Sycamore Sand) through the Middle Albian (Paluxy and upper Antlers Sands). A seasonal arid to semi-arid climate is indicated for at least 5 million years.

  11. Texas Gains on NAEP: Points of Light?

    ERIC Educational Resources Information Center

    Camilli, Gregory

    2000-01-01

    Places the 1992-1996 gain in mathematics scores from Texas on the National Assessment of Educational Progress (NAEP) from fourth to eighth grades, asserting that the so-called miracle in Texas looks much like the median elsewhere. Texas ranks 17th among the 35 states and 2 districts with NAEP scores for the period, but Texas is no worse than most…

  12. Water supply and needs for West Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This presentation focused on the water supplies and needs of West Texas, Texas High Plains. Groundwater is the most commonly used water resources on the Texas High Plains, with withdrawals from the Ogallala Aquifer dominating. The saturation thickness of the Ogallala Aquifer in Texas is such that t...

  13. 21 CFR 808.93 - Texas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Texas. 808.93 Section 808.93 Food and Drugs FOOD... and Local Exemptions § 808.93 Texas. (a) The following Texas medical device requirement is enforceable... that, in enforcing this requirement, Texas apply the definition of “used hearing aid” in §...

  14. 21 CFR 808.93 - Texas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Texas. 808.93 Section 808.93 Food and Drugs FOOD... and Local Exemptions § 808.93 Texas. (a) The following Texas medical device requirement is enforceable... that, in enforcing this requirement, Texas apply the definition of “used hearing aid” in §...

  15. 21 CFR 808.93 - Texas.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Texas. 808.93 Section 808.93 Food and Drugs FOOD... and Local Exemptions § 808.93 Texas. (a) The following Texas medical device requirement is enforceable... that, in enforcing this requirement, Texas apply the definition of “used hearing aid” in §...

  16. Texas Affordable Baccalaureate Program: A Collaboration between the Texas Higher Education Coordinating Board, South Texas College, and Texas A&M University-Commerce. CBE Case Study

    ERIC Educational Resources Information Center

    Klein-Collins, Rebecca; Glancey, Kathleen

    2015-01-01

    This case study is part of a series on newer competency-based degree programs that have been emerging in recent years. In January 2014, the Texas Higher Education Coordinating Board (THECB), South Texas College (STC), and Texas A&M University-Commerce (A&M Commerce) launched the Texas Affordable Baccalaureate Program, the state's first…

  17. 21 CFR 808.93 - Texas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Texas. 808.93 Section 808.93 Food and Drugs FOOD... and Local Exemptions § 808.93 Texas. (a) The following Texas medical device requirement is enforceable... that, in enforcing this requirement, Texas apply the definition of “used hearing aid” in §...

  18. Charter Schools in Texas: An Overview

    ERIC Educational Resources Information Center

    Penning, Francisco; Slate, John R.

    2011-01-01

    In this article we analyzed the literature regarding charter schools in the State of Texas. We specifically examined the evolution of the charter school movement in Texas. Moreover, data regarding the effectiveness/ineffectiveness of charter schools in Texas were discussed. Our overview of Texas charter schools, given their widespread presence in…

  19. 21 CFR 808.93 - Texas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Texas. 808.93 Section 808.93 Food and Drugs FOOD... and Local Exemptions § 808.93 Texas. (a) The following Texas medical device requirement is enforceable... that, in enforcing this requirement, Texas apply the definition of “used hearing aid” in §...

  20. TEXAS MIGRANT LABOR, THE 1964 MIGRATION.

    ERIC Educational Resources Information Center

    Good Neighbor Commission of Texas, Austin.

    THE MAJORITY OF TEXAS MIGRANTS LIVE IN SOUTH TEXAS AND APPROXIMATELY 95 PERCENT OF THEM ARE OF MEXICAN EXTRACTION. MOST OF THE OTHER FIVE PERCENT ARE EAST TEXAS NEGROES. THE MECHANIZATION OF COTTON HARVESTING AND THE EXPIRATION OF THE "BRACERO PROGRAM" IN 1964 HAVE CAUSED MORE TEXAS MIGRANTS TO SEEK EMPLOYMENT OUTSIDE OF THE STATE. DURING 1964,…

  1. Joint inversion of geophysical data using petrophysical clustering and facies deformation wth the level set technique

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2015-12-01

    Geological expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical datasets. The merging of such information can result in more realistic solution in the distribution of the model parameters, reducing ipse facto the non-uniqueness of the inverse problem. We consider two level of heterogeneities: facies, described by facies boundaries and heteroegenities inside each facies determined by a correlogram. In this presentation, we pose the geophysical inverse problem in terms of Gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geological cross-section, including the definition of spatial boundaries for the geological facies. The petrophysical relationship problem is formulated as a regression problem upon each facies. The inversion of the geophysical data is performed in a Bayesian framework. We demonstrate the usefulness of this strategy using a first synthetic case for which we perform a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface. The joint inversion is used to recover the density and resistivity distributions of the subsurface. In a second step, we consider the possibility that the facies boundaries are deformable and their shapes are inverted as well. We use the level set approach to perform such deformation preserving prior topological properties of the facies throughout the inversion. With the help of prior facies petrophysical relationships and topological characteristic of each facies, we make posterior inference about multiple geophysical tomograms based on their corresponding geophysical data misfits. The method is applied to a second synthetic case showing that we can recover the heterogeneities inside the facies, the mean values for the petrophysical properties, and, to some extent, the facies boundaries using the 2D joint inversion of

  2. Microbial contamination of two urban sandstone aquifers in the UK.

    PubMed

    Powell, Karen L; Taylor, Richard G; Cronin, Aidan A; Barrett, Mike H; Pedley, Steve; Sellwood, Jane; Trowsdale, Sam A; Lerner, David N

    2003-01-01

    Development of urban groundwater has historically been constrained by concerns about its quality. Rising urban water tables and overabstraction from rural aquifers in the UK have led to a renewed interest in urban groundwater, particularly the possibility of finding water of acceptable quality at depth. This study assessed the microbial quality of groundwater collected from depth-specific intervals over a 15-month period within the Permo-Triassic Sherwood Sandstone aquifers underlying the cities of Nottingham and Birmingham. Sewage-derived bacteria (thermotolerant coliforms, faecal streptococci and sulphite-reducing clostridia) and viruses (enteroviruses, Norwalk-like viruses, coliphage) were regularly detected to depths of 60 m in the unconfined sandstone and to a depth of 91 m in the confined sandstone. Microbial concentrations varied temporally and spatially but increased frequency of contamination with depth coincided with geological heterogeneities such as fissures and mudstone bands. Significantly, detection of Norwalk-like viruses and Coxsackievirus B4 in groundwater corresponded with seasonal variations in virus discharge to the sewer system. The observation of low levels of sewage-derived microbial contaminants at depth in the Triassic Sandstone aquifer is explained by the movement of infinitesimal proportions of bulk (macroscopic) groundwater flow along preferential pathways (e.g., fissures, bedding planes). The existence of very high microbial populations at source (raw sewage) and their extremely low detection limits at the receptor (multilevel piezometer) enable these statistically extreme (microscopic) flows to be traced. Rapid penetration of microbial contaminants into sandstone aquifers, not previously reported, highlights the vulnerability of sandstone aquifers to microbial contamination. PMID:12502063

  3. Diagenetic pathways for sandstones: The role of initial composition

    SciTech Connect

    Harris, N.B.

    1995-09-01

    The initial composition of a clastic section is critical in determining the diagenetic reactions that a sandstone will undergo during burial, reactions which strongly influence its reservoir properties. The role of initial composition is illustrated for Middle Jurassic sandstones of northwest Europe (including the Brent sandstone of the North Sea) and Tertiary sandstones of the Gulf of Mexico. The composition of the former evolves from arkose to quartz arenite, with massive dissolution first of plagioclase and subsequently K-feldspar. As the bulk composition changes, the suite of clay minerals changes from kaolinite-dominated to illite-dominated, suite of clay minerals changes from kaolinite-dominated to illite-dominated, typically accompanied by a pronounced decrease in permeability. The Gulf of Mexico sandstones are also initially arkoses. Their composition, however, evolves toward a mixture of quartz and compositionally pure albite. Kaolinite remains the dominant authigenic clay within the sandstones; however detrital clays change from a Na-rich, smectitic mixed layer clay to a K-rich, illitic mixed layer clay. The contrasting diagenetic pathways result from differing mineralogy in the clastic section. The smectite-rich mudstones in the Gulf of Mexico provide a powerful sink for potassium and source of sodium. The resulting low potassium activity results in K-feldspar dissolution; it also prevents illite formation, while high sodium activity stabilizes albite. The Middle Jurassic clastic section in northwest Europe contains relatively little smectite, thus lacks the potassium sink and sodium source. Sodium activity is low, so plagioclases preferentially dissolve. K-feldspars also dissolve, but the potassium here is available for illite formation.

  4. Upper Wilcox Rosita delta system of south Texas: growth-faulted shelf-edge deltas

    SciTech Connect

    Edwards, M.B.

    1981-01-01

    The Rosita delta system, a heretofore unrecognized, major depositional system preserved in the deep upper Wilcox of south Texas, was delineated by detailed correlation of approximately 500 well logs. The Rosita delta system comprises at least three delta complexes, each of which can be traced up to tens of miles along strike and up to approximately 15 mi (24 km) downdip. Basinward, across the growth-fault zone, each delta complex thickens from about 600 ft (180 m) to more than 3000 ft (900 m). The growth faults were activated by progradation of deltas over unstable prodelta-slope muds at the contemporary shelf margin. The three upper Wilcox delta complexes studied in detail are, from oldest to youngest, the Duval, Zapata, and Live Oak deltas, named for the counties in which they are centered. Each complex consists of several lobes, some of which can be traced across the deep zones where the thickness increases by as much as tenfold owing to progradation over active growth faults. Characteristic coarsening-upward progradational units are interpreted from electric log patterns to include prodelta shales, delta-front sandstones, distributary channel and channel-mouth bar sandstones, and interdistributary shales and sandstones. Appreciable variability in sandstone distribution in the deltas may reflect changing importance of fluvial versus marine currents in distributing sediment along the delta front. However, all of the deltas prograded abruptly toward the shelf margin. The gulfward extent of these delta complexes is unknown, and it is concluded that appreciable quantities of sandstone remain to be explored in the deep subsurface of the trend.

  5. Upper Cretaceous molluscan record along a transect from Virden, New Mexico, to Del Rio, Texas

    USGS Publications Warehouse

    Cobban, W.A.; Hook, S.C.; McKinney, K.C.

    2008-01-01

    Updated age assignments and new collections of molluscan fossils from lower Cenomanian through upper Campanian strata in Texas permit a much refined biostratigraphic correlation with the rocks of New Mexico and the Western Interior. Generic names of many Late Cretaceous ammonites and inoceramid bivalves from Texas are updated to permit this correlation. Strata correlated in the west-to-east transect include the lower Cenomanian Beartooth Quartzite and Sarten Sandstone of southwest New Mexico, and the Eagle Mountains Formation, Del Rio Clay, Buda Limestone, and. basal beds of the Chispa Summit, Ojinaga, and Boquillas Formations of the Texas-Mexico border area. Middle Cenomanian strata are lacking in southwestern New Mexico but are present in the lower parts of the Chispa Summit and Boquillas Formations in southwest Texas. Upper Cenomanian and lower Turonian rocks are present at many localities in New Mexico and Texas in the Mancos Shale and Chispa Summit, Ojinaga, and Boquillas Formations. Middle Turonian and younger rocks seem to be entirely nonmarine in southwestern New Mexico, but they are marine in the Rio Grande area in the Chispa. Summit, Ojinaga, and Boquillas Formations. The upper part of the Chispa Summit and Boquillas contain late Turonian fossils. Rocks of Coniacian and Santonian age are present high in the Chispa Summit, Ojinaga, and Boquillas Formations, and in the lower part of the Austin. The San Carlos, Aguja, Pen, and Austin Formations contain fossils of Campanian age. Fossils representing at least 38 Upper Cretaceous ammonite zones are present along the transect. Collections made in recent years in southwestern New Mexico and at Sierra de Cristo Rey just west of downtown El Paso, Texas, have been well treated and do not need revision. Taxonomic names and zonations published in the pre-1970 literature on the Rio Grande area of Texas have been updated. New fossil collections from the Big Bend National Park, Texas, allow for a much refined correlation

  6. A new bee species that excavates sandstone nests.

    PubMed

    Orr, Michael C; Griswold, Terry; Pitts, James P; Parker, Frank D

    2016-09-12

    Humanity has long been fascinated by animals with apparently unfavorable lifestyles [1]. Nesting habits are especially important because they can limit where organisms live, thereby driving population, community, and even ecosystem dynamics [2]. The question arises, then, why bees nest in active termite mounds [3] or on the rim of degassing volcanoes, seemingly preferring such hardship [4]. Here, we present a new bee species that excavates sandstone nests, Anthophora (Anthophoroides) pueblo Orr (described in Supplemental Information, published with this article online), despite the challenges already inherent to desert life. Ultimately, the benefits of nesting in sandstone appear to outweigh the associated costs in this system. PMID:27623257

  7. Natural and Laboratory-Induced Compaction Bands in Aztec Sandstone

    NASA Astrophysics Data System (ADS)

    Haimson, B. C.; Lee, H.

    2002-12-01

    The Aztec sandstone used in this research is from the Valley of Fire State Park area, Nevada. This Jurassic aeolian sandstone is extremely weak (uniaxial compressive strength of 1-2 MPa); porosity averages 26%; grains are subrounded and have a bimodal size distribution (0.1 mm and 0.5 mm); its mineral composition (K. Sternlof, personal comm.) is 93% quartz, 5% k-spar, and 2% kaolinite, Fe carbonate and others; grain bonding is primarily through suturing. Sternlof et al. (EOS, November, 2001) observed substantial exposure of mainly compactive deformation bands in the Aztec sandstone. We studied an SEM image of a compaction band found in a hand sample of the Aztec sandstone. We also conducted a drilling test in a 130x130x180 mm prismatic specimen subjected to a preset far-field true triaxial stress condition (\\sigmah = 15 MPa, \\sigmav = 25 MPa, \\sigmaH = 40 MPa). Drilling of a 20 mm dia. vertical hole created a long fracture-like thin tabular breakout along the \\sigmah springline and perpendicular to \\sigmaH direction. SEM analysis of the zones ahead of the breakout tips revealed narrow bands of presumed debonded intact grains interspersed with grain fragments. We infer that the fragments were formed from multiple splitting or crushing of compacted grains in the band of high compressive stress concentration developed along the \\sigmah springline. SEM images away from the breakout tip surroundings showed no such fragments. SEM study of the natural compaction band showed a similar arrangement of mainly intact grains surrounded by grain fragments. Using the Optimas optical software package, we found the percentage of pore area within the band ahead of the breakout tips to average 17%; outside of this zone it was 23%. In the natural compaction band pore area occupied 8.5% of the band; in the host rock adjacent to the compaction band it averaged 19%. These readings strongly suggest porosity reduction due to compaction in both cases. The close resemblance between the

  8. Hydrogeology of the Potsdam Sandstone in northern New York

    USGS Publications Warehouse

    Williams, John H.; Reynolds, Richard J.; Franzi, David A.; Romanowicz, Edwin A.; Paillet, Frederick L.

    2010-01-01

    The Potsdam Sandstone of Cambrian age forms a transboundary aquifer that extends across northern New York and into southern Quebec. The Potsdam Sandstone is a gently dipping sequence of arkose, subarkose, and orthoquartzite that unconformably overlies Precambrian metamorphic bedrock. The Potsdam irregularly grades upward over a thickness of 450 m from a heterogeneous feldspathic and argillaceous rock to a homogeneous, quartz-rich and matrix-poor rock. The hydrogeological framework of the Potsdam Sandstone was investigated through an analysis of records from 1,500 wells and geophysical logs from 40 wells, and through compilation of GIS coverages of bedrock and surficial geology, examination of bedrock cores, and construction of hydrogeological sections. The upper several metres of the sandstone typically is weathered and fractured and, where saturated, readily transmits groundwater. Bedding-related fractures in the sandstone commonly form sub-horizontal flow zones of relatively high transmissivity. The vertical distribution of sub-horizontal flow zones is variable; spacings of less than 10 m are common. Transmissivity of individual flow zones may be more than 100 m2/d but typically is less than 10 m2/d. High angle fractures, including joints and faults, locally provide vertical hydraulic connection between flow zones. Hydraulic head gradients in the aquifer commonly are downward; a laterally extensive series of sub-horizontal flow zones serve as drains for the groundwater flow system. Vertical hydraulic head differences between shallow and deep flow zones range from 1 m to more than 20 m. The maximum head differences are in recharge areas upgradient from the area where the Chateauguay and Chazy Rivers, and their tributaries, have cut into till and bedrock. Till overlies the sandstone in much of the study area; its thickness is generally greatest in the western part, where it may exceed 50 m. A discontinuous belt of bedrock pavements stripped of glacial drift extends

  9. Improvement in facies discrimination using multiple seismic attributes for permeability modelling of the Athabasca Oil Sands, Canada

    NASA Astrophysics Data System (ADS)

    Kashihara, Koji; Tsuji, Takashi

    2010-02-01

    This study was conducted to develop a reservoir modelling workflow to reproduce the heterogeneous distribution of effective permeability that impacts on the performance of SAGD (Steam Assisted Gravity Drainage), the in-situ bitumen recovery technique in the Athabasca Oil Sands. Lithologic facies distribution is the main cause of the heterogeneity in bitumen reservoirs in the study area. The target formation consists of sand with mudstone facies in a fluvial-to-estuary channel system, where the mudstone interrupts fluid flow and reduces effective permeability. In this study, the lithologic facies is classified into three classes having different characteristics of effective permeability, depending on the shapes of mudstones. The reservoir modelling workflow of this study consists of two main modules; facies modelling and permeability modelling. The facies modelling provides an identification of the three lithologic facies, using a stochastic approach, which mainly control the effective permeability. The permeability modelling populates mudstone volume fraction first, then transforms it into effective permeability. A series of flow simulations applied to mini-models of the lithologic facies obtains the transformation functions of the mudstone volume fraction into the effective permeability. Seismic data contribute to the facies modelling via providing prior probability of facies, which is incorporated in the facies models by geostatistical techniques. In particular, this study employs a probabilistic neural network utilising multiple seismic attributes in facies prediction that improves the prior probability of facies. The result of using the improved prior probability in facies modelling is compared to the conventional method using a single seismic attribute to demonstrate the improvement in the facies discrimination. Using P-wave velocity in combination with density in the multiple seismic attributes is the essence of the improved facies discrimination. This paper

  10. Source facies and oil families of the Malay Basin, Malaysia

    SciTech Connect

    Creaney, S.; Hussein, A.H. ); Curry, D.J.; Bohacs, K.M. ); Hassan, R. )

    1994-07-01

    The Malay Basin consists of a number of separate petroleum systems, driven exclusively by nonmarine source rocks. These systems range from lower Oligocene to middle Miocene and show a progression from lacustrine-dominated source facies in the lower Oligocene to lower Miocene section to coastal plain/delta plain coal-related sources in the lower to middle Miocene section. Two lacustrine sources are recognized in the older section, and multiple source/reservoir pairs are recognized in the younger coaly section. The lacustrine sources can be recognized using well-log analysis combined with detailed core and sidewall core sampling. Chemically, they are characterized by low pristane/phytane ratios, low oleanane contents, and a general absence of resin-derived terpanes. These sources have TOCs in the 1.0-4.0% range and hydrogen indices of up to 750. In contrast, the coal-related sources are chemically distinct with pristane/phytane ratios of up to 8, very high oleanane contents, and often abundant resinous compounds. All these sources are generally overmature in the basin center and immature toward the basin margin. The oils sourced from all sources in the Malay Basin are generally low in sulfur and of very high economic value. Detailed biomarker analysis of the oils in the Malay Basin has allowed the recognition of families associated with the above sources and demonstrated that oil migration has been largely strata parallel with little cross-stratal mixing of families.

  11. Nature and origin of fluids in granulite facies metamorphism

    NASA Technical Reports Server (NTRS)

    Newton, R. C.

    1988-01-01

    The various models for the nature and origin of fluids in granulite facies metamorphism were summarized. Field and petrologic evidence exists for both fluid-absent and fluid-present deep crustal metamorphism. The South Indian granulite province is often cited as a fluid-rich example. The fluids must have been low in H2O and thus high in CO2. Deep crustal and subcrustal sources of CO2 are as yet unproven possibilities. There is much recent discussion of the possible ways in which deep crustal melts and fluids could have interacted in granulite metamorphism. Possible explanations for the characteristically low activity of H2O associated with granulite terranes were discussed. Granulites of the Adirondacks, New York, show evidence for vapor-absent conditions, and thus appear different from those of South India, for which CO2 streaming was proposed. Several features, such as the presence of high-density CO2 fluid inclusions, that may be misleading as evidence for CO2-saturated conditions during metamorphism, were discussed.

  12. Middle Eocene seagrass facies from Apennine carbonate platforms (Italy)

    NASA Astrophysics Data System (ADS)

    Tomassetti, Laura; Benedetti, Andrea; Brandano, Marco

    2016-04-01

    Two stratigraphic sections located in the Latium-Abruzzi (Monte Porchio, Central Apennines, Central Italy) and in the Apulian carbonate platform (S. Cesarea-Torre Tiggiano, Salento, Southern Italy) were measured and sampled to document the sedimentological characteristic and the faunistic assemblages of Middle Eocene seagrass deposits. The faunistic assemblages are dominated by porcellaneous foraminifera Orbitolites, Alveolina, Idalina, Spiroloculina, Quinqueloculina, Triloculina and abundant hooked-shaped gypsinids, associated with hooked red algae and green algae Halimeda. Fabiania, rotaliids and textulariids as well as nummulitids are subordinated. The samples were assigned to Lutetian (SBZ13-16) according to the occurrence of Nummulites cf. lehneri, Alveolina ex. gr. elliptica, Idalina berthelini, Orbitolites complanatus, Slovenites decastroi and Medocia blayensis. At Santa Cesarea reticulate nummulites occur in association with Alveolina spp. and Halkyardia minima marking the lower Bartonian (SBZ17). Three main facies associations have been recognised: I) larger porcellaneous foraminiferal grainstones with orbitolitids and alveolinids deposited into high-energy shallow-water settings influenced by wave processes that reworked the sediments associated with a seagrass; II) grainstone to packstone with small porcellaneous foraminifera and abundant permanently-attached gypsinids deposited in a more protected (e.g., small embayment) in situ vegetated environment; III) bioclastic packstone with parautochthonous material reworked from the seagrass by rip currents and accumulated into rip channels in a slightly deeper environment. The biotic assemblages suggest that the depositional environment is consistent with tropical to subtropical vegetated environments within oligotrophic conditions.

  13. Nature and origin of fluids in granulite facies metamorphism

    NASA Astrophysics Data System (ADS)

    Newton, R. C.

    The various models for the nature and origin of fluids in granulite facies metamorphism were summarized. Field and petrologic evidence exists for both fluid-absent and fluid-present deep crustal metamorphism. The South Indian granulite province is often cited as a fluid-rich example. The fluids must have been low in H2O and thus high in CO2. Deep crustal and subcrustal sources of CO2 are as yet unproven possibilities. There is much recent discussion of the possible ways in which deep crustal melts and fluids could have interacted in granulite metamorphism. Possible explanations for the characteristically low activity of H2O associated with granulite terranes were discussed. Granulites of the Adirondacks, New York, show evidence for vapor-absent conditions, and thus appear different from those of South India, for which CO2 streaming was proposed. Several features, such as the presence of high-density CO2 fluid inclusions, that may be misleading as evidence for CO2-saturated conditions during metamorphism, were discussed.

  14. Early Tertiary subsidence and sedimentary facies - Northern Sirte Basin, Libya

    SciTech Connect

    Gumati, Y.D.; Kanes, W.H.

    1985-12-01

    The subsidence curves and subsidence rate curves for the Sirte basin, constructed from the stratigraphic record, show that subsidence was continuous throughout Late Cretaceous and Tertiary times, reaching a maximum during the Paleocene and Eocene, when a major reactivation of faults occurred. Shales and carbonates were deposited during all of the Late Cretaceous and Tertiary. Abrupt lateral facies changes occur from the platform areas toward the deeper troughs along with steep downdip thickening. The absence of upper Paleozoic and lower Mesozoic sediments suggests that the area was domed, faulted, and eroded during the late Mesozoic. As a result of crustal extension during the Paleocene, a marked lithologic and structural change occurred. The Heira Shale succeeded the Kalash Limestone in the Marada trough. Reactivation of the earlier faults, accompanied by an increase in the sediment supply from the south, caused these lower Paleocene shales to cover the entire area, with the exception of the old highs where carbonate deposition continued. An intercalation of shales and carbonates provides a sensitive indicator of change of depth and sediment type. 14 figures.

  15. Early Tertiary subsidence and sedimentary facies - northern Sirte Basin, Libya

    SciTech Connect

    Gumati, Y.D.; Kanes, W.H.

    1985-01-01

    The subsidence curves and subsidence rate curves for the Sirte basin, constructed from the stratigraphic record, show that subsidence was continuous throughout Late Cretaceous and Tertiary times, reaching a maximum during the Paleocene and Eocene, when a major reactivation of faults occurred. Shales and carbonates were deposited during all of the Late Cretaceous and Tertiary. Abrupt lateral facies changes occur from the platform areas toward the deeper troughs along with steep downdip thickening. These conditions were probably assisted by contemporaneous faulting along structurally weak hinge lines where the dominant structural elements are normal step faults. The absence of upper Paleozoic and lower Mesozoic sediments suggests that the area was domed, faulted, and eroded during the late Mesozoic. As a result of crustal extension during the Paleocene, a marked lithologic and structural change occurred. The Heira Shale succeeded the Kalash Limestone in the Marada trough. Reactivation of the earlier faults, accompanied by an increase in the sediment supply from the south, caused these lower Paleocene shales to cover the entire area, with the exception of the old highs where carbonate deposition continued. An intercalation of shales and carbonates provides a sensitive indicator of change of depth and sediment type.

  16. Depositional facies and diagenetic history of Trenton Limestone in northern Indiana

    SciTech Connect

    Fara, D.R.; Keith, B.D.

    1984-12-01

    Subsurface cores were studied petrographically to determine the facies and diagenetic history of the Trenton Limestone on a regional scale in northern Indiana. The Trenton Limestone is a yellowish olive-gray fossiliferous limestone, which is replaced by a light-gray dolostone in northern Indiana. Facies composing the Trenton are: 1) bryozoan-echinoderm packstone, 2) bryozoan-echinoderm grainstone, 3) bryozoan packstone to wackestone, 4) lime mudstone, and 5) dolostone. The bryozoan-echinoderm packstone is the major facies. Coarse-grained (1-4 mm) grainstones are typically 1 ft (30 cm) thick, have abrupt bases, and become muddy upward. They are considered storm deposits. Hardgrounds occur throughout the limestone facies, but they are most numerous toward the base. These facies indicate deposition below wave base, interrupted by periods of high energy during storms. Fossiliferous white and gray chert nodules are scattered throughout the unit. Also found in the limestone facies are prevalent stylolites and microstylolites, an indication of chemical compaction. The dolostone facies consists of coarsely crystalline (0.4 mm) idiotopic dolomite. Pyrite is associated with the dolomite. Porosity, found only in the dolostone, is discontinuous and characterized as intercrystalline, vuggy, and moldic. Porous zones are commonly oil stained or have been plugged by poikilotopic selentic gypsum. Minor amounts of celestite are found as cavity fillings.

  17. Imaging Sand Bars using 3D GPR in an Outcrop Reservoir Analog: Cretaceous Ferron Sandstone, South-East Utah

    NASA Astrophysics Data System (ADS)

    Aziz, A. S.; Stewart, R. R.; Ullah, M. S.; Bhattacharya, J.

    2015-12-01

    Outcrop analog studies provide crucial information on geometry and facies patterns to improve the understanding of the complex subsurface reservoir architecture for enhanced oil recovery (EOR) planning during field development. Ground-penetrating radar (GPR) has greatly facilitated analog outcrop study progress by bridging the gap in image resolution between seismic and well data. A 3D GPR survey was conducted to visualize architectural elements of friction-dominated distributary mouth bars within proximal delta front deposits in Cretaceous Ferron Sandstone at the top of the Notom Delta in south-east Utah. Sensors and Software's Noggin 250 MHz system was used over a 25 m x 15 m grid. We employed a spatial sampling of 0.5 m for the inline (dip direction) and 1.5 m for the crossline (strike direction). Standard processing flows including time-zero correction, dewow, gain, background subtraction and 2D migration were used to increase the signal-to-noise ratio. Formation velocity estimates from the hyperbola matching yielded 0.131 m/ns which is comparable to the literature velocity of about 0.125 m/ns. The calculated average dielectric constant (directly related to volumetric water content) is 5.2 matches unsaturated sandstone. The depth of GPR penetration is limited to approximately 3 m - likely due to the compaction/carbonate cementation in the rock and interbedded layers of finer-grained material contributing to higher attenuation of the GPR signal. The vertical resolution is about 0.125 m, enabling the imaging of the dune-scale cross sets (15-20 cm thickness). Calculation of the medium porosity via an adapted Wyllie Time Average equation yields 7.8 % which is consistent with the average porosity (5-10%) obtained from the literature. Bedding diagrams from local cliff exposures in the previous studies show gently NE dipping accretion of single large foresets that were interpreted as small-scale unit bars, the amalgamation of which resulted in the progradation of

  18. Tectonic implications of facies patterns, Lower Permian Dry Mountain trough, east-central Nevada

    SciTech Connect

    Gallegos, D.M.; Snyder, W.S.; Spinosa, C. )

    1991-02-01

    Paleozoic tectonism is indicated by a study of a west-east facies analysis transect across the northern portion of the Lower Permian Dry Mountain trough (DMT). In an attempt to characterize the Early Permian basin-filling sequences, three broadly recognizable facies packages have been identified across the DMT: the western margin facies and the central basin facies of the DMT and an eastern shelf facies. In the western margin facies of the basin, pulses of tectonic activity are recorded at McCloud Spring in the Sulphur Springs Range. Here, shallow open-marine carbonate overlies eroded Vinini Formation and, in turn, is unconformably overlain by basinal marine carbonate. An unconformity also marks the contact with the overriding prograding coarse clastic facies. These abrupt transitions suggest the sediments were deposited in a tectonically active area where they preservation of Waltherian sequences is unlikely to occur. Similarly abrupt transitions are evident in the western part of the central basin facies. At Portuguese Springs n the Diamond Range, a thin basal marine conglomerate delineates Lower Permian sedimentation over the Pennsylvanian Ely Formation. Coarsening-upward basinal carbonate strata of pelagic, hemipelagic, and turbidite components overlie the basal conglomerate. this progression of sediments is unconformably overlain by a subaerial sequence of coarse clastic deposits. Within the eastern part of the central basin facies in the Maverick Spring Range, the Lower Permian sediments are open-marine siltstone, wackestone, packstone, and grainstone. The sediments are assigned to a gradually sloping ramp, indicating the effects of tectonism on this margin of the basin were subdued.

  19. Modeling Oligo-Miocence channel sands (Dezful Embayment, SW Iran): an integrated facies classification workflow

    NASA Astrophysics Data System (ADS)

    Heydari, Mostafa; Maddahi, Iradj; Moradpour, Mehran; Esmaeilpour, Sajjad

    2014-08-01

    This study has been conducted on Mansuri onshore oilfield located in Dezful Embayment, south-west Iran. One of the hydrocarbon-bearing formations is a Oligo-Miocene Asmari formation—the most prolific Iranian reservoir rock. Like many other oilfields in the area, the trap in this field is deemed structural (anticline), formed during the collision of the Arabian plate with the Iranian plate and the folding of Neotethys deposits with a NW-SE trend. This study integrates three different quantitative studies from geology, geophysics and petrophysics disciplines to quantitate ‘the qualitative study of seismic facies analysis based on trace shapes and 3D multi-attribute clustering’. First, stratigraphic sequences and seismic detectable facies were derived at one well location using the available high resolution core facies analysis and depositional environment assessment reports. Paleo and petrophysical logs from other wells were subsequently used for the extrapolation of stratigraphic sequences interpreted at the first well. Utilizing lithology discrimination obtained by wire-line log interpretation, facies were extrapolated to all wells in the area. Seismic 3D attribute analysis and seismic facies classification established a 3D facies volume accordingly, which was finally calibrated to geological facies at well locations. The ultimate extracted facies-guided geobody shows that good reservoir-quality channel sands have accumulated with NW/SE elongation at the ridge of the structure. As a result, this type of geometry has created a stratigraphic/structural hydrocarbon trap in this oilfield. Moreover, seismic facies analysis shows that buried channels do not parallel the predominant Arabian plate-originated channels (with SW-NE trends) in SW Zagros and are locally swerved in this area.

  20. The making of a sandstone colossus: Tectonically and climatically induced flushing of 'Nubian' sands in the Early Paleozoic

    NASA Astrophysics Data System (ADS)

    Luthi, Stefan M.; Hagadorn, James W.; Donselaar, Marinus E.

    2013-04-01

    Massive 'Nubian' sandstones of Cambro-Ordovician age drape most of the Arabian and northern African tectonic plates and preserve a sensitive record of how continental margins evolve under greenhouse conditions. These strata also contain important aquifers, petroleum reservoirs, and archaeological monuments such as Petra, and they were formed by a geologically sudden and long-lasting influx of >500,000 km3 of predominantly quartz sand. The cause and timing of this continent-scale sedimentation event were so far unknown. Here we constrain the depositional history of these strata and hypothesize that poleward migration of the Gondwanan supercontinent out of the horse latitudes caused a five-fold increase in sedimentation rates and buildup of one of the largest epicratonic sand wedges in earth history. Geohistorical sedimentation and subsidence modeling of these sandstones is presented, based on sedimentologic, biostratigraphic, basement paleotopographic, facies, and tectonic dip analyses of a well-preserved paleoslope-axial transect of 542-462 million-year-old strata in Jordan. This region experienced a ~25 m/Ma increase in sedimentation rate over ~30 Ma, concomitant with near-equilibrium plate subsidence response. Sedimentary rocks in the studied sequences exhibit coeval compositional variations that suggest a change in sedimentation style from immature to ultramature clastics. Our results are internally consistent with movement of a continent from an arid subtropical high toward a wet subpolar low, which would have caused widespread flushing of hypermature sands sourced from the interior of the African-Nubian Shield toward the continent margin.

  1. Asymmetric crying facies with microcephaly and mental retardation. An autosomal dominant syndrome with variable expressivity.

    PubMed

    Silengo, M C; Bell, G L; Biagioli, M; Guala, A; Bianco, R; Strandoni, P; De Sario, P N; Franceschini, P

    1986-12-01

    An infant boy with asymmetric crying facies, microcephaly, developmental retardation and failure to thrive is reported. His two siblings died in the newborn period because of complex congenital heart defects. The mother and the maternal grandmother have asymmetric crying facies, microcephaly and normal intelligence. A maternal aunt has severe physical and mental retardation, facial asymmetry, microcephaly, and cleft palate. This family allows an expansion of the spectrum of malformations associated with asymmetric crying facies and suggests autosomal dominant inheritance with variable expressivity. PMID:3815881

  2. Continuity and internal properties of Gulf Coast sandstones and their implications for geopressured fluid production

    SciTech Connect

    Morton, R.A.; Ewing, T.E.; Tyler, N.

    1983-01-01

    The intrinsic properties of the genetic sandstone units that typify many geopressured geothermal aquifers and hydrocarbon reservoirs in the Gulf Coast region were systematically investigated classified, and differentiated. The following topics are coverd: structural and stratigraphic limits of sandstone reservoirs, characteristics and dimensions of Gulf Coast sandstones; fault-compartment areas; comparison of production and geologic estimates of aquifer fluid volume; geologic setting and reservoir characteristics, Wells of Opportunity; internal properties of sandstones; and implications for geopressured fluid production. (MHR)

  3. Stratigraphy and correlation of Upper Triassic strata between west Texas and eastern New Mexico

    SciTech Connect

    Lucas, S.G. ); Anderson, O.J. )

    1992-04-01

    Lithostratigraphy and vertebrate biochronology allow precise correlation of Upper Triassic strata between west Texas and eastern New Mexico. Upper Triassic strata are well exposed in west Texas from Oldham to Scurry counties, and are assigned to the Dockum Formation of the Chinle Group. Fossil vertebrates from the Camp Springs and Tecovas Members are of late Carnian age, whereas those from the Copper Member are of early Norian age. Upper Triassic strata in east-central New Mexico, across the Llano Estacado from the west Texas outcrops, correlate as follows: Camper Springs = lower Santa Rose; Tecovas = upper Santa Rosa/Garita Creek; Trujillo = Trujillo ('Cuervo'); Cooper = lower Bull Canyon. Upper Triassic strata in southeastern New Mexico and in Howard and adjacent counties in Texas are the lower Santa Rosa/Camper Springs overlain by mudstones and sandstones that contain late Carnian vertebrates and are informally termed upper member of Dockum Formation. Available data refute several long-held ideas about the Upper Triassic of west Texas. These data demonstrate that: (1) there is a pervasive unconformity at the base of the Dockum Formation that represents much of Triassic time; (2) the Trujillo Member is not correlative with the Santa Rosa of eastern New Mexico: Trujillo is a medial Dockum unit, whereas Santa Rosa is at the base of the Upper Triassic section; (3) very little Dockum mudrock was deposited in lakes; and (4) Dockum rivers flowed almost exclusively to the north, northwest, and west, so there was no closed depositional basin in west Texas during the Late Triassic.

  4. Dalhart Texas 1972-2011

    NASA Video Gallery

    A water-rich polka dot pattern takes over the traditional rectangular patchwork of fields in this 40 year sequence of Landsat images of the dry Texas panhandle near the town of Dalhart. In this ser...

  5. 20. Detail of sandstone pier under north line of trusses ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. Detail of sandstone pier under north line of trusses showing granite pier cap (darker stone) which supports the vertical strut. View to east. - Selby Avenue Bridge, Spanning Short Line Railways track at Selby Avenue between Hamline & Snelling Avenues, Saint Paul, Ramsey County, MN

  6. Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions

    NASA Astrophysics Data System (ADS)

    Shalev, Eyal; Lyakhovsky, Vladimir; Ougier-Simonin, Audrey; Hamiel, Yariv; Zhu, Wenlu

    2014-05-01

    Sandstones display non-linear and inelastic behaviour such as hysteresis when subjected to cyclic loading. We present three hydrostatic compaction experiments with multiple loading-unloading cycles on Berea and Darley Dale sandstones and explain their hysteretic behaviour using non-linear inelastic compaction and dilation. Each experiment included eight to nine loading-unloading cycles with increasing maximum pressure in each subsequent cycle. Different pressure-volumetric strain relations during loading and unloading were observed. During the first cycles, under relatively low pressures, not all of the volumetric strain is recovered at the end of each cycle whereas at the last cycles, under relatively high pressures, the strain is recovered and the pressure-volumetric strain hysteresis loops are closed. The observed pressure-volumetric strain relations are non-linear and the effective bulk modulus of the sandstones changes between cycles. Observations are modelled with two inelastic deformation processes: irreversible compaction caused by changes in grain packing and recoverable compaction associated with grain contact adhesion, frictional sliding on grains or frictional sliding on cracks. The irreversible compaction is suggested to reflect rearrangement of grains into a more compact mode as the maximum pressure increases. Our model describes the `inelastic compaction envelope' in which sandstone sample will follow during hydrostatic loading. Irreversible compaction occurs when pressure is greater than a threshold value defined by the `inelastic compaction envelope'.

  7. A complex investigation of building sandstones from Saxony (Germany)

    SciTech Connect

    Goetze, Jens Siedel, Heiner

    2007-11-15

    The present paper provides a methodology for the investigation and characterization of building sandstones. This analytical scheme was designed for distinguishing mature arenites, which in general show very similar properties and are difficult to distinguish. This is shown for Cretaceous sandstones from various occurrences in Saxony (Germany), which have been used for centuries as building materials. The procedure is mainly based on the combination of macroscopic rock description, thin section polarizing microscopy (phase composition, texture, grain-size distribution) and cathodoluminescence (CL) microscopy (quartz types, feldspar and kaolinite content) coupled with image analysis, scanning electron microscopy (accessories, pore cement, diagenetic grain surface features), and analysis of pore space data. Sometimes, additional data from X-ray diffraction or chemical analyses (major and trace elements) can be used. Especially in the case of quartz rich arenites, CL is a powerful tool for provenance analysis. The detailed analysis of sandstone material in most cases allows us to assign historically used building material to a specific sandstone occurrence. These results are important for both interpreting the weathering behaviour of the building material and the conservation, reconstruction and stone replacement of historical monuments.

  8. Organic matter and sandstone-type uranium deposits: a primer

    USGS Publications Warehouse

    Leventhal, Joel S.

    1979-01-01

    Organic material is intimately associated with sandstone-type uranium deposits in the western United States.. This report gives details of the types of organic matter and their possible role in producing a uranium deposit. These steps include mobilization of uranium from igneous rocks, transportation from the surface, concentration by organic matter, reduction by organic matter, and preservation of the uranium deposit.

  9. Negative feedback between stress and erosion: origin of sandstone landforms

    NASA Astrophysics Data System (ADS)

    Bruthans, Jiri; Soukup, Jan; Vaculikova, Jana; Filippi, Michal; Schweigstillova, Jana; Mayo, Alan; Masin, David; Kletetschka, Gunther; Rihosek, Jaroslav

    2015-04-01

    Weathering and erosion of sandstone produces spectacular landforms such as arches, alcoves, pedestal rocks and pillars. The effect of gravity loading stress has been overlooked or assumed to increase the landform's weathering rate. Here we show by physical and numerical modeling, and field observations of locked sands and sandstones that an increase in stress within the landform reduces weathering and erosion. Material with insufficient loading is rapidly removed by weathering process and the remaining load bearing landform structure is protected by the fabric interlocking mechanism. As the landform evolves the increased stress inhibits erosion from raindrop impact, flowing water and slaking, and retards surface retreat caused by salt and frost weathering. Planar discontinuities in sandstone and negative feedback between stress and weathering/erosion processes are sufficient conditions to create above-mentioned landforms. Our experiments are able to reproduce natural shapes including arches, alcoves, pedestal rocks and pillars using landform material and mimicking natural processes. The proposed negative feedback mechanism is supported by a numerical model of stress pattern in landforms. We conclude that stress field is the primary control of the shape evolution of sandstone landforms.

  10. Epilithic lichens in the Beacon sandstone formation, Victoria Land, Antarctica

    NASA Technical Reports Server (NTRS)

    Hale, M. E.; Friedmann, E. I. (Principal Investigator)

    1987-01-01

    The epilithic lichen flora on the Beacon sandstone formation in Victoria Land consists of seven species: Acarospora gwynnii Dodge & Rudolph, Buellia grisea Dodge & Baker, B. pallida Dodge & Baker, Carbonea capsulata (Dodge & Baker) Hale comb. nov., Lecanora fuscobrunnea Dodge & Baker, Lecidea cancriformis Dodge & Baker, and L. siplei Dodge & Baker. The typification of the species is given along with descriptions and distribution in Antarctica.

  11. A "Fossil Vadose Zone" from the Triassic Cooper Canyon Formation (Dockum Group) of West Texas

    NASA Astrophysics Data System (ADS)

    Holt, R. M.; Hughes, E.; Hubbell, J. M.; Grisak, G.; Cook, S.; Pickens, J.; Griffith, B. C.

    2008-12-01

    Hydrogeologic investigations at a proposed low-level radioactive waste disposal facility in Andrews County, Texas, have revealed evidence of a "fossil vadose zone" present within the redbeds of the Cooper Canyon Formation. The Cooper Canyon Formation is the uppermost stratigraphic unit in the Triassic Dockum Group in the study area and consists of very low permeability claystone and mudstone with several areally extensive siltstone/sandstone interbeds. Piezometers installed within two of the siltstone/sandstone zones show that water levels can rise up to about 20 m above the top of the zones and that uppermost of these zones is locally unsaturated. Waters in these zones have radiometric age dates of about 16,000 years. Recently twelve boreholes were drilled into the Cooper Canyon, cored, and sampled for in situ water potential (the sum of the matric and osmotic potential) and other hydraulic properties including moisture content, porosity, electrical conductivity of a saturated paste (EC), and chloride content. Water potential and saturation data show that Cooper Canyon mudstones are unsaturated to depths greater than 110 m with water potentials typically ranging from -2 MPa to -5 MPa. Very low water potentials (less than -1 MPa) occur within 0.1 m to 1 m of the upper and lower contacts of the siltstone/sandstone zones. Hydraulic gradients are outward from the siltstone/sandstone zones, and water potential values in the mudstones show one or more minima. These conditions preclude vertical flow between the land surface and underlying units and between siltstone/sandstone zones. The average air-entry pressure for Cooper Canyon rocks is about -1 MPa, and water saturation averages 83%. Chloride concentration profiles show a strong bulge in the sediments and rocks above the Cooper Canyon suggesting that very little Holocene recharge has reached the redbeds. Chloride concentrations within the siltstone/sandstone zones are higher than the surrounding mudstones, indicating

  12. Lower and middle Guadalupian shelf carbonates, eastern margin of Central Basin platform, Permian basin, west Texas

    SciTech Connect

    Ward, R.F.; Chalcraft, R.G.

    1988-01-01

    Lower and middle Guadalupian shelf carbonates serve as the reservoir for a nearly continuous band of oil fields extending 100 mi along the eastern margin of the Central Basin platform of west Texas. Approximately 5 billion bbl of oil have been produced from stratigraphic-structural traps within the Upper Permian (Gaudalupian Series) dolomites of the San Andrea and Grayburg Formations in Upton, Crane, Ector, Pecos, and Andrews Counties, Texas. The San Andrea and Grayburg Formations are cyclical shallowing-upward carbonate sequences of open shelf through sabkha facies whose depositional strike parallels the eastern margin of the Central Basin platform. Porosity and permeability of reservoir rock are governed by diagenetic processes such as dolomitization, anhydrite porosity occlusion, leaching, silicification, and authigenic clay formation. Self sediments are primarily burrowed wackestones and packstones that locally contain pelletal, skeletal, and ooid grainstones. Typical subtidal shelf sediments are capped by algal-laminated dolomite, nodular anhydritic dolomite, and bedded anhydrite. The fauna is normally sparse and dominated by foraminifera and algae. Less common faunal components include pelecypods, crinoids, sponges, Bryozoa, brachiopods, gastropods, and coral that are associated with the development of small scattered patch reefs. Lowering the sea level during the early Guadalpian initiated basinward progradation of San Andres carbonate facies with hydrocarbon reservoirs best developed in shallow self fusulinid wackestones to packstone and oolitic grainstone. Reservoir dolomites of the Grayburg formation are present east of San Andres fields with optimal reservoir properties occurring near the San Andreas outer shelf margin.

  13. Depositional systems and Karst geology of the Ellenburger group (lower ordovician), subsurface West Texas

    SciTech Connect

    Kerans, C.

    1990-01-01

    The Ellenburger Group of Texas contains estimated reserves of 1.15 billion barrels of oil and 2.2 billion barrels of oil equivalent. Despite its economic significance, comparatively little is known about the subsurface Ellenburger in West Texas; thus, this book presents a regional model of Ellenburger deposition and diagenesis. Using associations of lithologies and sedimentary structures observed in core, the author identified six depositional systems in the Ellenburger: fan delta-marginal marine, lower tidal flat, high-energy restricted shelf, low-energy restricted shelf, upper tidal flat, and open shallow water shelf. Diagenesis was dominated by three major styles of dolomitization: very fine crystalline dolomite (5-20 {mu}m), in tidal-flat facies; fine to medium crystalline dolomite (20-100 {mu}m), widespread in all facies; and coarse crystalline replacement mosaic dolomite and saddle dolomite cement, which formed in a burial setting after pre-Simpson karst formation and before Pennsylvanian faulting, uplift, and erosion. Other diagenetic events were karst-related dissolution episodes associated with repeated uplift and exposure and subsequent dedolomitization of the Ellenburger platform.

  14. Microstructural evolution of garnet in a greenschist facies transpression zone

    NASA Astrophysics Data System (ADS)

    Massey, M. A.; Prior, D. J.; Moecher, D. P.

    2007-12-01

    Natural observations, laboratory experiments, and theoretical modeling support the interpretation of Grt plasticity in the lower crust and upper mantle; however, these processes are thought to be of little importance in shallow to middle crustal levels. Multiple textural varieties of Grt from the western boundary (Mt. Dumplin high strain zone) of an upper greenschist facies dextral transpression zone in southern New England, USA, display mesoscopic and microscopic evidence of syn-tectonic deformation and recrystallization. These microstructures were examined further by optical microscopy, electron probe microanalysis, orientation contrast imaging (OCI), and automated electron backscatter diffraction (EBSD) in order to understand possible low-grade deformation mechanisms and their significance. The N-S-striking shear zone dips steeply W, the mylonitic foliation is defined by aligned Ms- Chl-Rt, layers of Qtz and fine-grained Grt; Qtz-Chl-Ms and fine-grained Grt aggregates define lineations that plunge moderately SW. S-C-C¡¦ fabrics, asymmetric folds and porphyroclasts (delta- and sigma-type) are well developed on foliation-normal/lineation-parallel planes, and display sinistral kinematics; surfaces normal to foliation and normal to lineation exhibit strong asymmetries that indicate normal motion. Pre-tectonic mineral parageneses consist of St pseudomorphed by Chl-Ms-Ctd, Als pseudomorphed by Ms, and coarse-grained Grt and Ab porphyroclasts with associated asymmetric tails. Grt is manifest as three types: 1) equant Grt porphyroclasts; 2) elongate Grt aggregates consisting of 50-100 Ým equant Grt porphyroblasts; 3) type 1-type 2 transitional Grt morphology. Elemental x-ray mapping of Ca and Mn reveals at least two periods of growth in Grt types 1 and 3, and one period of growth in type 2 that correlates with type 1 and 3 rims; Mg is completely homogenized. Detailed mapping of type 3 Grt cores reveals ¡¥fractured¡¦ Ca-enriched cores ¡¥healed¡¦ with Ca

  15. An experimental study of iron release from red sandstones

    NASA Astrophysics Data System (ADS)

    Purser, Gemma; Rochelle, Christopher; Rushton, Jeremy; Pearce, Jonathan

    2014-05-01

    An experimental study has been conducted to better understand the features of a natural CO2 -rich system at Saltwash Graben, Utah, USA. This site is associated with numerous CO2 rich springs linked to faults and fractures. In this area, a key feature of the red Entrada sandstone formation is the presence of significant rock bleaching (iron reduction and mobilisation) that occurs subparallel to bedding, typically at the base of large sandstone units and adjacent to some subvertical fractures. The difference in total iron content between the bleached and unbleached sandstones is very small, with the bleached sandstone containing slightly less total iron. In contrast to widely-reported regional bleaching, attributed to hydrocarbon accumulations towards structural crests, it has been suggested that the bleaching may be associated with the presence of modern day CO2 in the area and we sought to test this. Laboratory experiments were conducted to assess reaction processes that may have caused the observed iron reduction and mobilisation. Fixed volume batch reactors, containing either small cores of red or bleached sandstone were exposed to representative local ground waters (a dilute or a saline fluid), which were pressurised with either CO2 or N2 (the latter as a control) to 50 bar and placed inside an oven at 40° C to simulate subsurface conditions . The experiments ran for up to nine months with fluids being sampled periodically, though solids were only analysed once experiments were completed. Very little reaction was found to occur in the presence of CO2. It seems possible therefore that the modern CO2 rich fluids were not the cause of the sandstone bleaching. The study therefore assessed how the presence of reducing agents such as methane (CH4) and hydrogen sulphide (H2S) may result in the bleaching of the bulk sandstone. H2S was introduced into the experiments as a breakdown product of thioacetamide (0.1% v/v fluid containing thioacetamide was added to the

  16. Comparative thermometry on pelitic rocks and marbles of the Llano uplift, Texas

    SciTech Connect

    Letargo, C.M.R.; Lamb, W.M. . Dept. of Geology)

    1992-01-01

    The Llano Uplift in central Texas is a Grenville-aged metamorphic complex consisting of amphibolite facies assemblages whose development has been attributed to the emplacement of granite plutons between 1.0--1.1 Ga. Temperatures have been obtained from garnet-biotite, garnet-ilmenite, and calcite-dolomite pairs as well as from various silicate equilibria. Application of these geothermometers yield consistent results and are thus indicative of peak conditions attending the amphibolite facies metamorphism. Temperature determined using garnet-biotite and garnet-ilmenite thermometry compare favorably with calcite-dolomite temperatures obtained from marbles in contact with granite plutons in the southeastern part of the uplift. The highest calcite-dolomite temperatures of [approximately]600 C are obtained from marbles containing an isobarically invariant assemblage consisting of calcite + dolomite + diopside + tremolite + forsterite. At pressures of 2--3 kbar, this isobarically invariant assemblage will be stable at a temperature range of [approximately]600--650 C. Also in close proximity to granites in the southeast uplift is the assemblage muscovite + quartz + k-feldspar + sillimanite [approximately] andalusite which indicate T 650 C and P 2.5 kbar. Assemblages consisting of garnet + sillimanite + quartz + plagioclase (GASP) and garnet + rutile + ilmenite + plagioclase + quartz (GRIPS) are currently being studied to provide additional constraints on pressures of amphibolite facies metamorphism.

  17. Burrow-generated false facies and phantom sequences

    SciTech Connect

    Wanless, H.R.; Tagett, M.

    1986-05-01

    Callianassa (=Ophiomorpha) and other burrowers deeply rework shallow marine sequences. Through in-situ reworking, they create false sedimentary facies and stratigraphic sequences. Callianassa's key to effectiveness is that it expels sand and mud from burrow excavations but concentrates coarse material at the base of the burrow complex. Coarse material can be derived by falling into the burrow entrance, by reworking the existing sediment sequence, or by a combination of both. Examples come from shallow marine carbonate environments of south Florida and the Turks and Caicos Islands, British West Indies. Many mudbanks in south Florida are formed as stacks of layered mudstone units 20-100 cm thick. Between events, seagrasses may recolonize, and a burrowing benthic community may repopulate the substrate. The layered mudstone beneath older areas of mudbank flats can gradually be converted to a bioturbated skeletal wackestone by the deep burrowing community. Burrowing also causes mixing of faunal assemblages. On Caicos Bank, an extensive carbonate tidal flat (3-4 m thick) is slowly being transgressed. About 1 m of tidal-flat sequence is eroded at the shoreline. The remaining 2-3 m could be preserved as part of the transgressive sequence. Callianassa burrowing, however, quickly reworks the sequence, replacing tidal-flat sands and muds with marine peloidal and skeletal sediment. Within 100 m of the shoreline, the only evidence of the tidal-flat sequence is a concentration of high-spired gastropods in Calliannassa burrows at the base of the Holocene sequence and a few patches of tidal-flat sediment that burrowers missed. What looks like a basal transgressive lag is in fact a biogenic concentrate from in-situ reworking of a now phantom sequence.

  18. Anthropogenic effects on sedimentary facies in Lake Baldeney, West Germany

    NASA Astrophysics Data System (ADS)

    Neumann-Mahlkau, Peter; Niehaus, Heinz Theo

    1983-12-01

    Analysis of well logs of Lake Baldeney, a reservoir of the Ruhr River, yields four facies factors that reflect the effect of anthropogenic processes on the sediment. First, the sedimentation rate is directly related to the subsidence caused by mining. The extent of the subsidence was such that the sediment load of the river could not compensate for the sinking of the lake bottom. Discharged sediment filled about one-fifth of the basin within 40 years. In certain areas of the basin the sedimentation rate reached up to 10 cm per year. Second, the grain-size distribution of the sediment was influenced by long-term and short-term events. During the subsidence, grain-size distribution remained relatively constant. The destruction of the Möhne River dam during World War II resulted in the presence of an extremely large grain size as evidenced by the so-called Möhnelage. The filling of the lake after 1961 was accompanied by a continual increase in medium grain size. Third, until 1975, the mode of the lake sediment reflects the effect of mining in the vicinity of the lake. High coal content can be traced to its origin. The introduction of modern production processes, modernization of coal dressing, and hydraulic hauling is documented in the sediment. Finally, the heavy metal content of the sediment corresponds to the industrial development in the drainage area the Ruhr River. The accumulation of Cd reached an extreme concentration, exceeding the natural content by a thousand times. Variation in concentration reflects an increase in industrial production, as well as measures undertaken to restore water quality.

  19. Complex facies relationships and regional stratigraphy of the Mississippian Ste. Genevieve, Paoli, and Aux Vases Formations, Illinois basin: A major hydrocarbon-producing interval

    SciTech Connect

    Cole, R.D.; Nelson, W.J. )

    1993-03-01

    The Mississippian Ste. Genevieve and Paoli Limestones and sandstones of the Aux Vases Formation are lateral facies of one another. This interpretation is based on comprehensive investigations of outcrops, and selected cores, samples of well cuttings, and geophysical logs conducted over a period of four years. Both units exhibit similar sedimentological characteristics and represent open marine, shallow subtidal, and intertidal environments. The presence of low-angle cross-laminae, ripple- and plane-laminae, climbing ripples, and ooid shoals suggest most deposition occurred under low energy conditions. Lenticular, channel-like scour and fill structures that contain both fine-grained quartz sand and abraded, disarticulated fossil fragments indicate localized higher energy deposition. The authors studies indicate that siliciclastic vs. carbonate deposition was controlled strictly by available sediment, and not by regressive (siliciclastic) and transgressive (carbonate) events, as inferred by previous workers. This conclusion is based on lateral facies relationships, and the supplant