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1

Calc-silicate mineralization in active geothermal systems  

SciTech Connect

The detailed study of calc-silicate mineral zones and coexisting phase relations in the Cerro Prieto geothermal system were used as examples for thermodynamic evaluation of phase relations among minerals of variable composition and to calculate the chemical characteristics of hydrothermal solutions compatible with the observed calc-silicate assemblages. In general there is a close correlation between calculated and observed fluid compositions. Calculated fugacities of O{sub 2} at about 320{degrees}C in the Cerro Prieto geothermal system are about five orders of magnitude less than that at the nearby Salton Sea geothermal system. This observation is consistent with the occurrence of Fe{sup 3+} rich epidotes in the latter system and the presence of prehnite at Cerro Prieto.

Bird, D.K.; Schiffman, P.; Elders, W.A.; Williams, A.E.; McDowell, S.D.

1983-01-01

2

Active geothermal systems as natural analogs of HLW repositories  

SciTech Connect

Geologic analogs of long-lived processes in high-level waste (HLW) repositories have been much studied in recent years. However, most of these occurrences either involve natural processes going on today at 25{degree}C, or, if they are concerned with behavior at temperatures similar to the peak temperatures anticipated near HLW canisters, have long since ended. This paper points out the usefulness of studying modern geothermal systems as natural analogs, and to illustrate the concept with a dramatic example, the Salton Sea geothermal system (SSGS).

Elders, W.A.; Williams, A.E.; Cohen, L.H.

1988-01-01

3

Geothermal materials development activities  

SciTech Connect

This ongoing R&D program is a part of the Core Research Category of the Department of Energy/Geothermal Division initiative to accelerate the utilization of geothermal resources. High risk materials problems that if successfully solved will result in significant reductions in well drilling, fluid transport and energy conversion costs, are emphasized. The project has already developed several advanced materials systems that are being used by the geothermal industry and by Northeastern Electric, Gas and Steam Utilities. Specific topics currently being addressed include lightweight C0{sub 2}-resistant well cements, thermally conductive scale and corrosion resistant liner systems, chemical systems for lost circulation control, elastomer-metal bonding systems, and corrosion mitigation at the Geysers. Efforts to enhance the transfer of the technologies developed in these activities to other sectors of the economy are also underway.

Kukacka, L.E.

1993-06-01

4

National Geothermal Data System  

NASA Astrophysics Data System (ADS)

The goal of the U.S. Department of Energy's National Geothermal Data System is to design, build, implement, deploy and populate a national, sustainable, distributed, interoperable network of data and service (application) providers. These providers will develop, collect, serve, and maintain geothermal-relevant data that operates as an integral component of NGDS. As a result the geothermal industry, the public, and policy makers will have access to consistent and reliable data, which in turn, reduces the amount of staff time devoted to finding, retrieving, integrating, and verifying information. With easier access to information, the high cost and risk of geothermal power projects (especially exploration drilling) is reduced. Five separate NGDS projects provide the data support, acquisition, and access to cyber infrastructure necessary to reduce cost and risk of the nation's geothermal energy strategy and US DOE program goals focused on the production and utilization of geothermal energy. The U.S DOE Office of Energy Efficiency and Renewable Energy Geothermal Technologies Program is developing the knowledge and data foundation necessary for discovery and development of large-scale energy production while the Buildings Technology Program is focused on other practical applications such as direct use and residential/commercial ground source heat pumps. The NGDS provides expanded reference and resource data for research and development activities (a subset of the US DOE goals) and includes data from across all fifty states and the nation's leading academic geothermal centers. Thus, the project incorporates not only high-temperature potential but also moderate and low-temperature locations incorporating US DOE's goal of adding more geothermal electricity to the grid. The program, through its development of data integration cyberinfrastructure, will help lead to innovative exploration technologies through increased data availability on geothermal energy capacity. Finally, the project will contribute new data from previously unexplored locations. NGDS is being built using the US Geoscience Information Network (US GIN) data integration framework to promote interoperability across the Earth sciences community and with other emerging data integration and networking efforts.

Anderson, A. F.; Cuyler, D.; Snyder, W. S.; Allison, M. L.; Blackwell, D. D.; Williams, C. F.

2011-12-01

5

Geothermal expansion wellhead system  

Microsoft Academic Search

A geothermal expansion wellhead system is provided which adapts the wellhead and control valves to the casing in the wellbore. The system suspends and seals the casing while expanding and contracting during geothermal operations at temperatures up to 550° F. and above. The system consists of an expansion spool in which there is mounted an expansion mandrel which is secured

1985-01-01

6

Modeling of geothermal systems  

SciTech Connect

During the last decade the use of numerical modeling for geothermal resource evaluation has grown significantly, and new modeling approaches have been developed. In this paper we present a summary of the present status in numerical modeling of geothermal systems, emphasizing recent developments. Different modeling approaches are described and their applicability discussed. The various modeling tasks, including natural-state, exploitation, injection, multi-component and subsidence modeling, are illustrated with geothermal field examples. 99 refs., 14 figs.

Bodvarsson, G.S.; Pruess, K.; Lippmann, M.J.

1985-03-01

7

Hydrothermal mineralogy and fluid inclusions chemistry to understand the roots of active geothermal systems  

NASA Astrophysics Data System (ADS)

An integrated study to link magmatic textures, magmatic mineral compositions, hydrothermal alteration zoning, hydrothermal mineral chemistry, and fluid inclusion compositions has been undertaken to link an intrusive complex and its degassing alteration halo with their surface equivalent in an active geothermal system. Ngatamariki geothermal system, New Zealand, presents a unique feature in the Taupo Volcanic Zone (TVZ). Drilling intercepted an intrusive complex with a high temperature alteration halo similarly to what is observed in magmatic-derived ore deposits. Thus it presents the perfect opportunity to study the magmatic-hydrothermal transition of the TVZ by characterizing the nature of the deep magmatic fluids link to the heat source of the world known geothermal fields. The record of magmatic-hydrothermal fluid-rock interactions preserved at Ngatamariki may be analogous of processes presently occurring at depth beneath TVZ geothermal systems. The intrusive complex consists of over 5 km3 of tonalite, diorite, basalt and aplitic dykes. Evidence of undercooling subsolidus magmatic textures such as myrmekite and skeletal overgrowth are commonly observed and often linked to volatile loss. The fluids released during the crystallization of the intrusive complex are interpreted to be at the origin of the surrounding high temperature alteration halo. Advanced argillic to potassic alteration and high temperature acidic assemblage is associated with high-temperature quartz veining at depth and vuggy silica at the paleo-surface. Major element compositions of the white micas associated with the high temperature halo show a transition from, muscovite to phengite, muscovitic illite away from the intrusion, with a transition to pyrophyllite and/ or topaz, and andalusite characteristic of more acidic conditions. Abundant high-density (up to 59 wt% NaCl eq and homogenization temperatures of 550 degree Celsius and above) coexist with low-density vapor fluid inclusions. This inferred heterogeneous entrapment represents the phase separation condition at the magmatic-hydrothermal conditions. Microthermometry measurements revealed the common presence of CO2, NaCl, KCl and CaCl2 species. Chemical compositions of the trapped fluids represent the closest equivalent of the magmatic fluids exsolving at depth feeding the deep roots of the geothermal fields. This study brings new constraints on the chemical conditions to model deep fluid-rock interactions in active geothermal systems.

Chambefort, I. S.; Dilles, J. H.; Heinrich, C.

2013-12-01

8

Origin and Distribution of Thiophenes and Furans in Gas Discharges from Active Volcanoes and Geothermal Systems  

PubMed Central

The composition of non-methane organic volatile compounds (VOCs) determined in 139 thermal gas discharges from 18 different geothermal and volcanic systems in Italy and Latin America, consists of C2–C20 species pertaining to the alkanes, alkenes, aromatics and O-, S- and N-bearing classes of compounds. Thiophenes and mono-aromatics, especially the methylated species, are strongly enriched in fluids emissions related to hydrothermal systems. Addition of hydrogen sulphide to dienes and electrophilic methylation involving halogenated radicals may be invoked for the formation of these species. On the contrary, the formation of furans, with the only exception of C4H8O, seems to be favoured at oxidizing conditions and relatively high temperatures, although mechanisms similar to those hypothesized for the production of thiophenes can be suggested. Such thermodynamic features are typical of fluid reservoirs feeding high-temperature thermal discharges of volcanoes characterised by strong degassing activity, which are likely affected by conspicuous contribution from a magmatic source. The composition of heteroaromatics in fluids naturally discharged from active volcanoes and geothermal areas can then be considered largely dependent on the interplay between hydrothermal vs. magmatic contributions. This implies that they can be used as useful geochemical tools to be successfully applied in both volcanic monitoring and geothermal prospection. PMID:20480029

Tassi, Franco; Montegrossi, Giordano; Capecchiacci, Francesco; Vaselli, Orlando

2010-01-01

9

Cordon Caulle: an active volcanic-geothermal extensional system of Southern Andes of Chile  

NASA Astrophysics Data System (ADS)

Cordon Caulle (CC; 40.5° S) is an active volcanic-geothermal system of the Southern Volcanic Zone (SVZ; 37°-44°S). Morphologically, the CC system is a 6 km x 13 km volcanic plateau bordered by NW-trending structures, limited by Puyehue Volcano to the SE and by Caldera Nevada Caldera to the NW. While the SVZ is dominantly basaltic, CC is unique in that it has produced a wide compositional spectrum from basalt to rhyolite. The most recent volcanic activity of Puyehue-CC (last 70 ky) is dominantly silicic, including two historic fissure eruptions (1921-1922; 1960) and a recent central eruption from Puyehue Volcano (2011). Abnormally silicic volcanism was formerly attributed to a localized compression and long-term magma residence and differentiation, resulting from the NW orientation of underlying CC structures with respect to a NE-oriented ?1 (linked to regional strike-slip stress state). However, later studies, including examination of morpho-tectonic features; detailed structural analysis of the 1960 eruption (triggered by Mw 9.5 1960 Chilean Earthquake); InSAR deformation and gravity surveys, point to both historic and long-term extension at CC with ?hmax oriented NNW to NW. The pre-2011 (i.e. Puyehue Volcano eruption) geothermal features of CC included boiling hot springs and geysers (Caldera Nevada) and fumaroles (CC and Puyehue Volcano). Both water and gas chemistry surveys were undertaken to assess the source fluid composition and equilibrium temperature. The combination of water and gas geothermometers led to a conceptual model of a stratified geothermal reservoir, with shallow, low-chloride, steam-heated aquifers equilibrated at temperatures between 150°-180°C, overlying a deeper, possibly dominated reservoir with temperatures in excess of 280°C. Gas chemistry also produced the highest He ratios of the SVZ, in agreement with a relatively pure, undiluted magmatic signature and heat source fueling the geothermal system. Other indicators such as N2/Ar ratios indicated two sources of gases: a geothermal source (i.e. associated with benign, neutral geothermal fluids) at the centre of the CC, and a more volcanic-magmatic (i.e. associated with acidic, oxidising fluids) source towards the SE (Puyehue Volcano), in agreement with the presence of an active volcanic system. The combination of silicic volcanism, extension and high-temperature geothermal activity of CC pose some resemblance to high-temperature geothermal systems of the Taupo Volcanic Zone, North Island, New Zealand. In this setting, recent studies show that rifting (i.e. extension) can be a magma-assisted process. In a similar fashion, I hypothesize that a deep (> 2 km), NW-elongate magma reservoir can account for the development of NW-trending structures at CC, and the existence of central volcanism at both ends of the CC.

Sepulveda, F.

2013-05-01

10

Geotherm: the U.S. geological survey geothermal information system  

USGS Publications Warehouse

GEOTHERM is a comprehensive system of public databases and software used to store, locate, and evaluate information on the geology, geochemistry, and hydrology of geothermal systems. Three main databases address the general characteristics of geothermal wells and fields, and the chemical properties of geothermal fluids; the last database is currently the most active. System tasks are divided into four areas: (1) data acquisition and entry, involving data entry via word processors and magnetic tape; (2) quality assurance, including the criteria and standards handbook and front-end data-screening programs; (3) operation, involving database backups and information extraction; and (4) user assistance, preparation of such items as application programs, and a quarterly newsletter. The principal task of GEOTHERM is to provide information and research support for the conduct of national geothermal-resource assessments. The principal users of GEOTHERM are those involved with the Geothermal Research Program of the U.S. Geological Survey. Information in the system is available to the public on request. ?? 1983.

Bliss, J.D.; Rapport, A.

1983-01-01

11

Geothermal Systems for School.  

ERIC Educational Resources Information Center

Describes an award-winning school heating and cooling system in which two energy-efficient technologies, variable-flow pumping and geothermal heat pumps, were combined. The basic system schematic and annual energy use and cost savings statistics are provided. (GR)

Dinse, David H.

1998-01-01

12

Geothermal activities in Central America  

Microsoft Academic Search

The Agency for International Development is funding a new program in energy and minerals for Central America. Geothermal energy is an important component. A country-wide geothermal assessment has started in Honduras, and other assessment activities are in progress or planned for Costa Rica, El Salvador, Guatemala, and Panama. Instrumentation for well logging has been provided to Costa Rica, and a

J. T. Whetten; R. J. Hanold

1985-01-01

13

Active metasomatism in the Cerro Prieto geothermal system, Baja California, Mexico: a telescoped low pressure/temperature metamorphic facies series  

SciTech Connect

In the Cerro Prieto geothermal field, carbonate-cemented, quartzofeldspathic sediments of the Colorado River delta are being actively metasomatized into calc-silicate metamorphic rocks by reaction with alkali chloride brines between 200/sup 0/ and 370/sup 0/C, low fluid and lithostatic pressures, and low oxygen fugacities. Petrologic investigations of drill cores and cutting from over 50 wells in this field identified a prograde series of calc-silicate mineral zones which include as index minerals: wairakite, epidote, prehnite, and clinopyroxene. Associated divariant mineral assemblages are indicative of a very low pressure/temperature metamorphic facies series which encompasses the clay-carbonate, zeolite, greenschist, and amphibolite facies. This hydrothermal metamorphic facies series, which is becoming increasingly recognized in other active geothermal systems, is characterized by temperature-telescoped dehydration and decarbonation mineral equilibria. Its equivalent should now be sought in fossil hydrothermal systems.

Schiffman, P.; Elders, W.A.; Williams, A.E.; McDowell, S.D.; Bird, D.K.

1983-01-01

14

National Geothermal Data System (NGDS)  

DOE Data Explorer

The National Geothermal Data System (NGDS) is a DOE-funded distributed network of databases and data sites. Much of the risk of geothermal energy development is associated with exploring for, confirming and characterizing the available geothermal resources. The overriding purpose of the NGDS is to help mitigate this up-front risk by serving as a central gateway for geothermal and relevant related data as well as a link to distributed data sources. Assessing and categorizing the nation's geothermal resources and consolidating all geothermal data through a publicly accessible data system will support research, stimulate public interest, promote market acceptance and investment, and, in turn, the growth of the geothermal industry. Major participants in the NGDS to date include universities, laboratories, the Arizona Geological Survey and Association of American State Geologists (Arizona Geological Survey, lead), the Geothermal Resources Council, and the U.S. Geological Survey. The Geothermal Energy Association is collaborating with the NGDS to insure that it meets the needs of the geothermal industry.

15

Research drilling in an active geothermal system: Salton Sea Scientific Drilling Project (SSSDP)  

SciTech Connect

In March 1986 a research borehole, designed to study the processes occurring in an active, high-temperature, magmatically driven hydrothermal system, reached a depth of 3.22 km in the Salton Sea geothermal field at the northern end of the Gulf of California. Only 10% of the borehole was cored; however, an integrated set of drill cuttings, wireline logs, and downhole measurements were obtained using high-temperature tools and cables. Similarly, downhole VSP, gravity, and fluid sampling tools were successfully deployed. The borehole penetrates Pleistocene and upper Pliocene lake and delta sediments with minor extrusive and intrusive igneous rocks, all of which are being progressively altered to greenschist facies hornfelses. A flow test of a zone at 1865 m with a temperature of 305/sup 0/C, produced Na, Ca, and K chloride brines containing 24% of dissolved salts. Flows of up to 200 tons/hr of steam and brine were obtained. An even more productive zone, the deepest tested at 3215 m where the temperature was 355/sup 0/C, briefly attained a peak flow of 400 tons/hr during a 48-hour test. However, this test was marred by interference from other flow zones. Although the borehole was shut in after the 7-in. (17.78-cm) diameter liner parted, a comprehensive program of laboratory studies is underway in about 40 different institutions. Results to date have more than met their original goals. In the summer of 1987, field operations will resume and will include extensive reservoir engineering. However, drilling deeper to penetrate the magmatic rocks that underlie the explored hydrothermal system must await future funding.

Elders, W.A.

1987-05-01

16

Geothermal activities in Central America  

SciTech Connect

The Agency for International Development is funding a new program in energy and minerals for Central America. Geothermal energy is an important component. A country-wide geothermal assessment has started in Honduras, and other assessment activities are in progress or planned for Costa Rica, El Salvador, Guatemala, and Panama. Instrumentation for well logging has been provided to Costa Rica, and a self-contained logging truck will be made available for use throughout Central America. An important objective of this program is to involve the private sector in resource development. 4 refs., 3 figs.

Whetten, J.T.; Hanold, R.J.

1985-09-11

17

geothermal salinity control system  

SciTech Connect

Highly saline geothermal brine, such as that produced from the lower geothermal reserve of the Salton Sea geothermal field, is diluted with non-geothermal water of much lower salinity in a mixing zone proximate the high temperature end of a geothermal power plant, and preferably down in the production well just above the production zone, so as to reduce the chloride salt content of the production brine to a level that is at or below the saturated level at reinjection temperatures, thereby preventing any material chloride salt scaling at any location in the plant through reinjection. The permanent cemented-in production casing in the well is protected against the corrosive effects of the hot production brine by means of a removable production liner that is generally coextensive with the casing. Said mixing zone is provided in the lower portion of the liner, and the liner establishes an annulus between it and the casing through which said non-geothermal water flows downwardly to the mixing zone so as to exclude the production brine from contact with the casing.

McCabe, B.C.; Zajac, E.

1985-01-08

18

Investigating Geothermal Activity, Volcanic Systems, and Deep Tectonic Tremor on Akutan Island, Alaska, with Array Seismology  

NASA Astrophysics Data System (ADS)

In addition to hosting one of the most active volcanoes in the Aleutian Arc, Akutan Island, Alaska, is the site of a significant geothermal resource within Hot Springs Bay Valley (HSBV). We deployed 15 broadband (30 s to 50 Hz) seismometers in and around HSBV during July 2012 as part of an effort to establish a baseline for background seismic activity in HSBV prior to geothermal production on the island. The stations recorded data on-site and were retrieved in early September 2012. Additional targets for the array include the tracking of deep tectonic tremor known to occur within the Aleutian subduction zone and the characterization of volcano-tectonic (VT) and deep long period (DLP) earthquakes from Akutan Volcano. Because 13 of the stations in the array sit within an area roughly 1.5 km by 1.5 km, we plan to apply methods based on stacking and beamforming to analyze the waveforms of extended signals lacking clear phase arrivals (e.g., tremor). The average spacing of the seismometers, roughly 350 m, provides sensitivity to frequencies between 2-8 Hz. The stacking process also increases the signal-to-noise ratio of small amplitude signals propagating across the array (e.g., naturally occurring geothermal seismicity). As of August 2012, several episodes of tectonic tremor have been detected in the vicinity of Akutan Island during the array deployment based on recordings from nearby permanent stations operated by the Alaska Volcano Observatory (AVO). This is the first small-aperture array deployed in the Aleutian Islands and the results should serve as a guide for future array deployments along the Aleutian Arc as part of the upcoming EarthScope and GeoPRISMS push into Alaska. We demonstrate the power of array methods based on stacking at Akutan Volcano using a sequence of DLP earthquakes from June 11, 2012 that were recorded on the permanent AVO stations. We locate and characterize the lowest frequency portion of the signals at 0.5 Hz. At these low frequencies, the traditional "sparse" local network at Akutan effectively becomes a small-aperture array relative to the wavelength. We exploit the coherency among the stations and locate the DLPs by using a novel stacking method. The crux of the method involves scanning over all possible source locations and relative polarity combinations between the local stations to find the one that maximizes the stacked power at a well-defined region in the subsurface. As a result, the method is applicable even in the presence of mixed polarities. We discover that two of the stations at Akutan have DLP waveforms with opposite polarities compared to the other stations. Accounting for this polarity variation gives a DLP source location at 10 km depth, to the west-southwest of the Akutan summit caldera. These results give clear evidence for non-isotropic radiation patterns associated with DLPs and show the promise of array methods based on waveform stacking for providing future insights into the origin of volcanic as well as geothermal and tectonic seismicity.

Haney, M. M.; Prejean, S. G.; Ghosh, A.; Power, J. A.; Thurber, C. H.

2012-12-01

19

Computerized international geothermal information systems  

SciTech Connect

The computerized international geothermal energy information system is reviewed. The review covers establishment of the Italy - United States linked data centers by the NATO Committee on Challenges of Modern Society, through a bilateral agreement, and up to the present time. The result of the information exchange project is given as the bibliographic and numerical data available from the data centers. Recommendations for the exchange of computerized geothermal information at the international level are discussed.

Phillips, S.L.; Lawrence, J.D.; Lepman, S.R.

1980-03-01

20

Geothermal systems on the island of Java, Indonesia  

NASA Astrophysics Data System (ADS)

This paper presents an overview of all known geothermal systems on the island of Java by presenting physicochemical data for associated hot springs, cold springs and acid crater lakes. A total of 69 locations were sampled and classified based on their position in either a volcanic complex (volcano-hosted) or a fault zone (fault-hosted). In particular the potential of a magmatic heat source for fault-hosted geothermal systems was investigated. Volcano-hosted geothermal systems had higher HCO3- concentrations and higher Mg/Na ratios than fault-hosted geothermal systems. This geochemical difference is likely due to degassing and subsequent CO2-water reaction in the volcano-hosted systems, which is absent in the fault-hosted geothermal systems. The HCO3 vs. Cl and Mg/Na vs. SO4/Cl systematics indicated that fault-hosted geothermal systems located in the active Quaternary volcanic belt received shallow magmatic fluids, hence should be classified as volcano-hosted geothermal systems. The heat source of fault-hosted geothermal systems located in the old (Tertiary) volcanic belt was investigated by a combination of Li enrichment and calculated reservoir temperatures. There a shallow magmatic heat source was indicated only for the Cilayu and Cisolok geothermal systems. Thus, a deep seated magma was considered to be the heat source for the fault-hosted geothermal systems of Cikundul, Pakenjeng, Parangtritis and Pacitan. In ten of the volcano-hosted geothermal systems, 2H and 18O isotope enrichments were found, but not in any of the fault-hosted geothermal systems. Stable isotope enrichment due to evaporation was recognized in the Kawah Candradimuka and Kawah Sileri, Kawah Hujan and Candi Gedong Songo geothermal systems. A combination of intensive evaporation and magmatic gases input produced very heavy stable isotopes in the hot acid crater lakes of the Kawah Kamojang, Kawah Sikidang and Kawah Putih geothermal systems. The addition of substantial amounts of andesitic water to the geothermal fluid was observed in the Candi Songgoriti, Banyuasin and Pablengan geothermal systems. Contrary to established belief fault-hosted geothermal systems on Java could be considered a potential source for geothermal energy.

Purnomo, Budi Joko; Pichler, Thomas

2014-09-01

21

Evolution of an active magmatic-geothermal system at The Geysers, California  

NASA Astrophysics Data System (ADS)

The Geysers geothermal system initially developed at 1.1 to 1.2 Ma in response to the intrusion of a hypabyssal granitic pluton exceeding 100 km2 in area. The geothermal system, which is developed in Mesozoic metagraywacke and the underlying granite, is currently vapor-dominated and produces only dry steam. Mineralogic, fluid inclusion and isotopic data demonstrate the current vapor-dominated regime evolved from a liquid-dominated system. Within 600 m of the pluton, the rocks were altered to a biotite hornfels that is cut by veins of tourmaline + biotite + actinolite + clinopyroxene + albitic plagioclase. Fluid inclusions trapped in the vein minerals record maximum homogenization temperatures near 380°C and salinities up to 44 wt% NaCl equivalent. With increasing distance from the pluton, the veins are characterized by actinolite + epidote, epidote + chlorite, and finally calcite. Quartz and adularia are commonly observed in these veins. Fluid inclusions trapped at a distance of 1750 m from the intrusion record temperatures up to 305°C and salinities of 5 wt% NaCl equivalent. Whole-rock oxygen isotope data indicates the metagraywacke and granitic reservoir rocks were isotopically exchanged with meteoric water during the liquid dominated phase of the system. The transition from liquid- to vapor-dominated conditions occurred at 0.25 to 0.28 Ma, based on 40Ar/39Ar spectrum dating of adularia. As the liquids boiled off, bladed calcite, chalcedony, quartz and adularia were deposited. Vapor-rich inclusions dominate the fluid inclusion populations of many samples. Low salinity liquid-rich fluid inclusions (0.0 - 0.4 wt% NaCl equivalent), interpreted to consist primarily of steam condensate, suggest that widespread boiling and vapor-dominated convection cells had formed in the upper part of the present-day reservoir by the time temperatures had dropped to approximately 250° - 265°C. Subsequent inflow of relatively cool marginal meteoric waters resulted in the deposition of calcite and the formation of low permeability seals around the reservoir. The present vapor-dominated system at The Geysers consists of two distinct, hydraulically connected steam reservoirs. The upper, normal vapor-dominated reservoir is found throughout the field. Temperatures within this reservoir are isothermal and close to 240°C. The lower high temperature reservoir occurs within the biotite hornfels in the northern half of the field. Measured temperatures follow a conductive gradient and range from about 240°C to 400°C. Pressures are vaporstatic in both reservoirs. The high temperature reservoir in the Northwest Geysers is the youngest part of the system. Here newly formed biotite hornfels is being heated by a recent magmatic intrusion interpreted to have been emplaced between 5,000 and 10,000 y bp. This portion of the deep Northwest reservoir is characterized by low permeabilities and the highest measured temperatures and 3He/4He ratios (~7-9.6Ra) encountered in the field. In contrast to other parts of the system, the biotite hornfels in the Northwest Geysers has not been isotopically exchanged with meteoric water.

Moore, J. N.; Walters, M.

2012-12-01

22

Modeling brine-rock interactions in an enhanced geothermal system deep fractured reservoir at Soultz-Sous-Forets (France): a joint approach using two geochemical codes: frachem and toughreact  

E-print Network

other geothermal system), integration of these simulationsGeothermal reservoir, brine, granite, secondary minerals, numerical codes, simulation,high-salinity geothermal fluid. FRACHEM SIMULATIONS Activity

Andre, Laurent; Spycher, Nicolas; Xu, Tianfu; Vuataz, Francois-D.; Pruess, Karsten.

2006-01-01

23

NATIONAL GEOTHERMAL DATA SYSTEM (NGDS) GEOTHERMAL DATA DOMAIN: ASSESSMENT OF GEOTHERMAL COMMUNITY DATA NEEDS  

SciTech Connect

To satisfy the critical need for geothermal data to ad- vance geothermal energy as a viable renewable ener- gy contender, the U.S. Department of Energy is in- vesting in the development of the National Geother- mal Data System (NGDS). This paper outlines efforts among geothermal data providers nationwide to sup- ply cutting edge geo-informatics. NGDS geothermal data acquisition, delivery, and methodology are dis- cussed. In particular, this paper addresses the various types of data required to effectively assess geother- mal energy potential and why simple links to existing data are insufficient. To create a platform for ready access by all geothermal stakeholders, the NGDS in- cludes a work plan that addresses data assets and re- sources of interest to users, a survey of data provid- ers, data content models, and how data will be ex- changed and promoted, as well as lessons learned within the geothermal community.

Anderson, Arlene [United States Department of Energy; Blackwell, David [Southern Methodist University; Chickering, Cathy [Southern Methodist University; Boyd, Toni [Oregon Institute of Technology; Horne, Roland [Stanford University; MacKenzie, Matthew [Uberity Technology Corporation; Moore, Joseph [University of Utah; Nickull, Duane [Uberity Technology Corporation; Richard, Stephen [Arizona Geological survey; Shevenell, Lisa A. [University of Nevada, Reno

2013-01-01

24

Recent geothermal reservoir engineering activities at Lawrence Berkeley Laboratory  

SciTech Connect

This paper briefly describes the most recent activities in reservoir engineering for the geothermal group of Lawrence Berkeley Laboratory (LBL). The primary emphasis of the geothermal program of LBL is dedicated to reservoir engineering including theoretical investigations, the development and application of mathematical models, and field studies. The objectives of these activities are to develop and validate methods and instruments which will be utilized in the determination of the parameters of geothermal systems, and the identification and evaluation of the importance of the distinct processes which occur in reservoirs. The ultimate goal of the program is the development of state of the art technologies which characterize geothermal reservoirs and evaluate their productive capacity and longevity.

Lippmann, M.J.; Bodvarsson, G.S.; Benson, S.M.; Pruess, K.

1987-09-01

25

Monitoring Biological Activity at Geothermal Power Plants  

SciTech Connect

The economic impact of microbial growth in geothermal power plants has been estimated to be as high as $500,000 annually for a 100 MWe plant. Many methods are available to monitor biological activity at these facilities; however, very few plants have any on-line monitoring program in place. Metal coupon, selective culturing (MPN), total organic carbon (TOC), adenosine triphosphate (ATP), respirometry, phospholipid fatty acid (PLFA), and denaturing gradient gel electrophoresis (DGGE) characterizations have been conducted using water samples collected from geothermal plants located in California and Utah. In addition, the on-line performance of a commercial electrochemical monitor, the BIoGEORGE?, has been evaluated during extended deployments at geothermal facilities. This report provides a review of these techniques, presents data on their application from laboratory and field studies, and discusses their value in characterizing and monitoring biological activities at geothermal power plants.

Peter Pryfogle

2005-09-01

26

Active metasomatism in the Cerro Prieto geothermal system, Baja California, Mexico: a telescoped low-pressure, low-temperature metamorphic facies series  

SciTech Connect

In the Cerro Prieto geothermal field, carbonate-cemented, quartzofeldspathic sediments of the Colorado River delta are being actively metasomatized into calc-silicate metamorphic rocks by reaction with alkali chloride brines between 200 and 370 C, at low fluid and lithostatic pressures and low oxygen fugacities. Their petrologic investigations of drill cores and cuttings from more than 50 wells in this field identified a prograde series of zones that include as index minerals wairakite, epidote, prehnite, and clinopyroxene. Associated divariant mineral assemblages are indicate of a very low pressure, low-temperature metamorphic facies series spanning the clay-carbonate, zeolite, greenschist, and amphibolite facies. This hydrothermal facies series, which is now recognized in other active geothermal systems, is characterized by temperature-telescoped dehydration and decarbonation. Its equivalent can now be sought in fossil hydrothermal systems.

Schiffman, P.; Elders, W.A.; Williams, A.E.; McDowell, S.D.; Bird, D.K.

1984-01-01

27

Enhanced Geothermal Systems (EGS) R&D Program, Status Report: Foreign Research on Enhanced Geothermal Systems  

SciTech Connect

This report reviews enhanced geothermal systems (EGS) research outside the United States. The term ''enhanced geothermal systems'' refers to the use of advanced technology to extract heat energy from underground in areas with higher than average heat flow but where the natural permeability or fluid content is limited. EGS covers the spectrum of geothermal resources from low permeability hydrothermal to hot dry rock.

McLarty, Lynn; Entingh, Daniel

2000-09-29

28

Fine-grained clay fraction (,0.2 {mu}m): An interesting tool to approach the present thermal and permeability state in active geothermal systems  

SciTech Connect

We have investigated by X-ray diffraction the very fine grained secondary minerals (< 0.2 {micro}m) developed in geothermal systems, in relation with their present thermal and permeability state. Because the smallest particles are the most reactive part of a rock, they are the youngest mineral phases of the geothermal fields. This study has been performed on two active geothermal fields: Milos field, Greece (130 < T < 320 C) and Chipilapa field, Salvador (90 < T < 215 C). In the Milos field, the mineralogical composition of the < 0.2 {micro}m clay fraction observed in the reservoir strongly differs from the overlying altered metamorphic schists in the presence of abundant quantities of saponite and talc/saponite interstratified minerals at unusually high temperature. These phases are considered to be kinetically control-led ''metastable'' minerals which rapidly evolve towards actinolite and talc for present temperatures higher than 300 C. Their occurrence is a good indicator of discharge in highly permeable zones. In the geothermal field of Chipilapa, the mineralogical composition of the < 0.2 {micro}m clay fractions fairly agrees with the temperatures presently measured in the wells, whereas several discrepancies may be pointed out from the compositions of coarser clay fractions (< 5 {micro}m) which contain minerals inherited from higher temperature stages. Permeable zones may be evidenced from an increase of expandable components in the interstratified minerals and a decrease of the coherent domain of the unexpandable clay particles (chlorite).

Patrier, P.; Papapanagiotou, P.; Beaufort, D.; Traineau, H.; Bril, H.

1992-01-01

29

Small geothermal electric systems for remote powering  

SciTech Connect

This report describes conditions and costs at which quite small (100 to 1,000 kilowatt) geothermal systems could be used for off-grid powering at remote locations. This is a first step in a larger process of determining locations and conditions at which markets for such systems could be developed. The results suggest that small geothermal systems offer substantial economic and environmental advantages for powering off-grid towns and villages. Geothermal power is most likely to be economic if the system size is 300 kW or greater, down to reservoir temperatures of 100{degree}C. For system sizes smaller than 300 kW, the economics can be favorable if the reservoir temperature is about 120{degree}C or above. Important markets include sites remote from grids in many developing and developed countries. Estimates of geothermal resources in many developing countries are shown.

Entingh, Daniel J.; Easwaran, Eyob.; McLarty, Lynn

1994-08-08

30

Residential space heating cost: Geothermal vs conventional systems  

Microsoft Academic Search

Operating characteristics and economics of several representative space heating systems are analyzed. Analyses are based on the use of geothermal water at temperatures as low as 120 F in forced air systems and 140 F in baseboard convection and radiant floor panel systems. The baseboard convection system is the most economical type of geothermal space heating system when geothermal water

I. A. Engen

1978-01-01

31

Performance of deep geothermal energy systems  

NASA Astrophysics Data System (ADS)

Geothermal energy is an important source of clean and renewable energy. This project deals with the study of deep geothermal power plants for the generation of electricity. The design involves the extraction of heat from the Earth and its conversion into electricity. This is performed by allowing fluid deep into the Earth where it gets heated due to the surrounding rock. The fluid gets vaporized and returns to the surface in a heat pipe. Finally, the energy of the fluid is converted into electricity using turbine or organic rankine cycle (ORC). The main feature of the system is the employment of side channels to increase the amount of thermal energy extracted. A finite difference computer model is developed to solve the heat transport equation. The numerical model was employed to evaluate the performance of the design. The major goal was to optimize the output power as a function of parameters such as thermal diffusivity of the rock, depth of the main well, number and length of lateral channels. The sustainable lifetime of the system for a target output power of 2 MW has been calculated for deep geothermal systems with drilling depths of 8000 and 10000 meters, and a financial analysis has been performed to evaluate the economic feasibility of the system for a practical range of geothermal parameters. Results show promising an outlook for deep geothermal systems for practical applications.

Manikonda, Nikhil

32

The interplay between fault-fracture networks activity, fluid flow and mineralization in the Andes: A case study in the Tolhuaca geothermal system, southern Chile  

NASA Astrophysics Data System (ADS)

The nature of the interplay between active tectonics and fluid flow is a key feature to better understand the chemical evolution of fluids in geothermal and hydrothermal systems. The prominent hydrothermal, tectonic and volcanic activity of the Southern Andes volcanic zone (SVZ) makes it one of the best natural laboratories to address this issue. In the northern termination of the Liquińe-Ofqui Fault System (LOFS), tectonic and volcanic processes interact to define the geothermal field of Tolhuaca. The objective of our current research is to assess the nature of the interplay between brittle deformation and chemical evolution of fluids and mineral paragenesis. Tol-1 is a vertical 1.080 m deep borehole which could yield relevant information regarding the evolution of the Tolhuaca geothermal system. The methodology to achieve our objective includes the structural and geochemical analysis of oriented faults, fault-veins and veins -former pathways- in the core. Structural mapping at the regional scale will help to identify the main structural system, which accommodates the regional stresses, and promotes fluid migration, accumulation and arrest. Fluid inclusions analysis by microthermometry, LA-ICP-MS and Raman spectroscopy will allow a better understanding of the feedback between the fluid flow episodes and the mineralization. More than 120 structural measurements of faults, veins and fault-veins were performed (strike, dip, rake -when available-). Forty seven samples were taken for thin & fluid inclusions sections. Detailed mapping of structures including dip and kinematic indicators from mineral sealing was synthesized in a structural log of Tol-1 core. Our preliminary results show that there is a strong correlation between abundance of structures and rock type. Lava intervals exhibit more intense fracturing and veining than tuff and volcaniclastic intervals. In the upper 300 m of the core, structures are primarily steeply dipping with a dominant normal sense of displacement (some dextral component). Below a cataclastic zone at 300 m, structures are more variable in dip and sense of motion, with some reverse faults. Fluid inclusions petrography reveals the periodically feedback between fault-fractures networks activation and mineral mineralization sealing the conduits for fluid flow.

Sanchez, P.; Perez-Flores, P.; Reich, M.; Arancibia, G.; Cembrano, J. M.

2013-05-01

33

National Geothermal Data System (NGDS) Geothermal Data: Community Requirements and Information Engineering  

SciTech Connect

To satisfy the critical need for geothermal data to advance geothermal energy as a viable renewable energy contender, the U.S. Department of Energy is investing in the development of the National Geothermal Data System (NGDS). This paper outlines efforts among geothermal data providers nationwide to supply cutting edge geo-informatics. NGDS geothermal data acquisition, delivery, and methodology are discussed. In particular, this paper addresses the various types of data required to effectively assess geothermal energy potential and why simple links to existing data are insufficient. To create a platform for ready access by all geothermal stakeholders, the NGDS includes a work plan that addresses data assets and resources of interest to users, a survey of data providers, data content models, and how data will be exchanged and promoted, as well as lessons learned within the geothermal community.

Anderson, Arlene [United States Department of Energy; Blackwell, David [Southern Methodist University; Chickering, Cathy [Southern Methodist University; Boyd, Toni [Oregon Institute of Technology; Horne, Roland [Stanford University; MacKenzie, Matthew [Uberity Technology Corporation; Moore, Joseph [University of Utah; Nickull, Duane [Uberity Technology Corporation; Richard, Stephen [Arizona Geological survey; Shevenell, Lisa A. [University of Nevada, Reno

2013-10-01

34

Near-Surface CO2 Monitoring And Analysis To Detect Hidden Geothermal Systems  

E-print Network

be similar. SIMULATIONS MIGRATION OF GEOTHERMAL CO 2 Wehidden geothermal reservoirs using numerical simulation.geothermal systems and has moderate solubility in water. We carried out numerical simulations

Lewicki, Jennifer L.; Oldenburg, Curtis M.

2005-01-01

35

Exploration of geothermal systems using hyperspectral thermal infrared remote sensing  

NASA Astrophysics Data System (ADS)

Visible near infrared (VNIR), short-wave infrared (SWIR), and thermal infrared (TIR) remote sensing has long been used for geothermal exploration. Specific focus on the TIR region (8-12 ?m) has resulted in major-rock-forming mineral classes being identified and their areal percentages to be more easily mapped due in part to the linear mixing behavior of TIR emission. To understand the mineral compositional and thermal distribution of active geothermal surfaces systems, hyperspectral TIR data from the Spatially Enhanced Broadband Array Spectrograph System (SEBASS) airborne sensor were acquired over the Salton Sea, CA geothermal fields by The Aerospace Corporation on March 26, 2009 and April 6, 2010. SEBASS collects 128 wavelength channels at ~ 1 m spatial resolution. Such high resolution data are rarely available for this type of scientific analysis and enabled the identification of rare mineral assemblages associated with the geothermally-active areas. One surface unit with a unique spectrum, believed to be a magnesium sulfate of unknown hydration state, was identified for the first time in the SEBASS data. The abundance and distribution of this mineral varied between 2009 and 2010 likely due to the precipitation conditions. Data obtained by the SEBASS sensor were also regressed to the 32 channel spectral resolution of the Mineral and Gas Identifier (MAGI) airborne sensor in order to test sensitivity limits. At this lower spectral resolution, all surface minerals were still effectively identified and therefore validated data at MAGI resolution are still very effective for accurate surface compositional mapping. A similar approach used at active geothermal areas in other semi-arid regions around the world has the potential to better characterize transient mineralogy, identify "indicators minerals", understand the influence of surface and ground water, and ultimately to locate new geothermal targets for future exploration. Furthermore, new Mineral and Gas Identification (MAGI) data serve as an excellent precursor for future spaceborne TIR data such as the system proposed for the Hyperspectral Infrared Imager (HyspIRI) instrument.

Reath, Kevin A.; Ramsey, Michael S.

2013-09-01

36

Geothermal down well pumping system  

Microsoft Academic Search

A key technical problem in the exploitation of hot water geothermal energy resources is down-well pumping to inhibit mineral precipitation, improve thermal efficiency, and enhance flow. A novel approach to this problem involves the use of a small fraction of the thermal energy of the well water to boil and super-heat a clean feedwater flow in a down-hole exchanger adjacent

H. B. Matthews; W. D. McBee

1974-01-01

37

Active hydrothermal metamorphism in the Cerro Prieto geothermal system, Baja California, Mexico: a telescoped low P/T facies series. [Abstract only  

SciTech Connect

In the Cerro Prieto geothermal system, carbonate-cemented, quartzo-feldspathic sediments of the Colorado River delta are being actively recrystallized into calc-silicate metamorphic rocks through intense fluid/rock interaction with alkali chloride brine (1.5 x 10/sup 4/ ppM TDS) at temperatures between 200/sup 0/ and 370/sup 0/C, fluid pressures <0.25 Kb, lithostatic pressures <1.0 Kb, and oxygen fugacities close to the QFM buffer. Petrologic investigations of cuttings and core from more than 50 wells in this field reveal a prograde series of calc-silicate mineral zones with index metamorphic minerals: wairakite (wr), epidote (ep), prehnite (pr), and calcic clinopyrosene (cpx). The compositions of these and other key phases: wr (Ca/Ca + Na + K + 0.97), ep (Fe/Fe + Al/sup vi/ = 0.11 to 0.31), pr (Fe/Fe + Al/sup vi/ = 0.01 to 0.28), cps (close to Wo/sub 50/ and Mg/Mg + Fe + Mn = 0.23 to 0.90), actinolite (0.20 Al/sup iv//15 cations and Mg/Mg + Fe + Mn = 0.67 to 0.82), biotite (Mg/Mg + Fe + Mn = 0.58 to 0.87) and microcline (Or/sub 96 to 100/) reflect recrystallization under low fluid pressures, relatively low f/sub O/sub 2//, and varying brine compositions. Divariant mineral assemblages in this system comprise a very low P/T facies series encompassing the clay-carbonate, zeolite, greenschist, and amphibolite facies and reflect equilibrium occurring in response to both increasing temperature and decreasing CO/sub 2/ pressure. Similar facies series, characterized by telescoped devolatization mineral reactions, are becoming increasingly recognized in other active geothermal systems above 300/sup 0/C. However, close analogues in the fossil geologic record are as yet unidentified.

Schiffman, P. (Univ. of California, Riverside); Elders, W.A.; Williams, A.E.; McDowell, S.D.; Bird, D.K.

1983-03-01

38

Convective heat transport in geothermal systems  

SciTech Connect

Most geothermal systems under exploitation for direct use or electrical power production are of the hydrothermal type, where heat is transferred essentially by convection in the reservoir, conduction being secondary. In geothermal systems, buoyancy effects are generally important, but often the fluid and heat flow patterns are largely controlled by geologic features (e.g., faults, fractures, continuity of layers) and location of recharge and discharge zones. During exploitation, these flow patterns can drastically change in response to pressure and temperature declines, and changes in recharge/discharge patterns. Convective circulation models of several geothermal systems, before and after start of fluid production, are described, with emphasis on different characteristics of the systems and the effects of exploitation on their evolution. Convective heat transport in geothermal fields is discussed, taking into consideration (1) major geologic features; (2) temperature-dependent rock and fluid properties; (3) fracture- versus porous-medium characteristics; (4) single- versus two-phase reservoir systems; and (5) the presence of noncondensible gases.

Lippmann, M.J.; Bodvarsson, G.S.

1986-08-01

39

Induced seismicity associated with enhanced geothermal system  

SciTech Connect

Enhanced Geothermal Systems (EGS) offer the potential to significantly add to the world energy inventory. As with any development of new technology, some aspects of the technology has been accepted by the general public, but some have not yet been accepted and await further clarification before such acceptance is possible. One of the issues associated with EGS is the role of microseismicity during the creation of the underground reservoir and the subsequent extraction of the energy. The primary objectives of this white paper are to present an up-to-date review of the state of knowledge about induced seismicity during the creation and operation of enhanced geothermal systems, and to point out the gaps in knowledge that if addressed will allow an improved understanding of the mechanisms generating the events as well as serve as a basis to develop successful protocols for monitoring and addressing community issues associated with such induced seismicity. The information was collected though literature searches as well as convening three workshops to gather information from a wide audience. Although microseismicity has been associated with the development of production and injection operations in a variety of geothermal regions, there have been no or few adverse physical effects on the operations or on surrounding communities. Still, there is public concern over the possible amount and magnitude of the seismicity associated with current and future EGS operations. It is pointed out that microseismicity has been successfully dealt with in a variety of non-geothermal as well as geothermal environments. Several case histories are also presented to illustrate a variety of technical and public acceptance issues. It is concluded that EGS Induced seismicity need not pose any threat to the development of geothermal resources if community issues are properly handled. In fact, induced seismicity provides benefits because it can be used as a monitoring tool to understand the effectiveness of the EGS operations and shed light on the mechanics of the reservoir.

Majer, Ernest; Majer, Ernest L.; Baria, Roy; Stark, Mitch; Oates, Stephen; Bommer, Julian; Smith, Bill; Asanuma, Hiroshi

2006-09-26

40

Geothermal hot water recovery process and system  

Microsoft Academic Search

An improved process and system for recovering high-temperature hot water ; from a geothermal supply is described. Equipment is described for reducing the ; pressure at the well head, flashing the hot water to steam to elevate a two-phase ; mixture of steam and hot water through the casing aasembly. Such flashing is ; accompanied by the evolution of substantially

Kuwada

1974-01-01

41

A new classification scheme for deep geothermal systems based on geologic controls  

NASA Astrophysics Data System (ADS)

A key element in the characterization, assessment and development of geothermal energy systems is the resource classification. Throughout the past 30 years many classifications and definitions were published mainly based on temperature and thermodynamic properties. In the past classification systems, temperature has been the essential measure of the quality of the resource and geothermal systems have been divided into three different temperature (or enthalpy) classes: low-temperature, moderate-temperature and high-temperature. There are, however, no uniform temperature ranges for these classes. It is still a key requirement of a geothermal classification that resource assessment provides logical and consistent frameworks simplified enough to communicate important aspects of geothermal energy potential to both non-experts and general public. One possible solution may be to avoid classifying geothermal resources by temperature and simply state the range of temperatures at the individual site. Due to technological development, in particular in EGS (Enhanced Geothermal Systems or Engineered Geothermal Systems; both terms are considered synonymously in this thesis) technology, currently there are more geothermal systems potentially economic than 30 years ago. An alternative possibility is to classify geothermal energy systems by their geologic setting. Understanding and characterizing the geologic controls on geothermal systems has been an ongoing focus on different scales from plate tectonics to local tectonics/structural geology. In fact, the geologic setting has a fundamental influence on the potential temperature, on the fluid composition, the reservoir characteristics and whether the system is a predominantly convective or conductive system. The key element in this new classification for geothermal systems is the recognition that a geothermal system is part of a geological system. The structural geological and plate tectonic setting has a fundamental influence on the characteristics of a geothermal system. The thermal regime and heat flow, hydrogeologic regime, fluid dynamics, fluid chemistry, faults and fractures, stress regime, and lithological sequence are controlled by the plate tectonic framework, hence critical for understanding the geothermal system. It is important to identify if the geothermal system is located at active plate boundaries or in intracontinental tectonically quiescent settings and thus how it relates to both active volcanism and active tectonics.

Moeck, I.

2012-04-01

42

Use of U and Th Decay-Series Disequilibrium to Characterize Geothermal Systems: An Example from the Coso Geothermal System  

NASA Astrophysics Data System (ADS)

Uranium and thorium decay series isotopes were measured in fluids and solids in the Coso geothermal system to assess the utility and constrain the limitations of the radioisotopic approach to the investigation of rock-water interaction. Fluid radioisotope measurements indicate substantial kilometer-scale variability in chemistry. Between 1988 and 1990, radium isotope activity ratios indicate temporal variability, which is exhibited by apparent mixing relationships observed as a function of time for single wells. Activity ratios of Ra-224/Ra-226 and Ra- 228/Ra-226, and the processes that contribute and remove these radionuclide to and from the fluids, constrain residence times of fluids and may help constrain fluid velocities in the geothermal system. Activity ratios of Ra- 224/Ra-226 > ten were measured. In groundwater and geothermal systems ratios of Ra-224/Ra-226 > ten are limited to zones of thermal upwelling or very young (days to weeks) waters in mountainous areas. Rn-222 results indicate that radon is also an effective tracer for steam velocities within the geothermal system. Analysis of carbon dioxide and Rn-222 data indicates that the residence time of steam (time since separation from the liquid) is short (probably less than four days). Estimates of fluid velocities derived from Rn-222 and radium isotopic measurements are within an order of magnitude of velocities derived from a fluorescein tracer test. Both Rn-222 and Ra-224 activities are higher in single-phase fluids in the northwest as compared to the southeast, indicating a higher rock-surface-area/water-volume ratio in the northwest. Thus, measurements of short-lived radioisotopes and gaseous phase constituents can constrain processes and characteristics of geothermal systems that are usually difficult to constrain (e.g., surface area/volume, residence times). The NRC staff views expressed herein are preliminary and do not constitute a final judgment or determination of the matters addressed or of the acceptability of a license application for a geologic repository at Yucca Mountain.

Leslie, B. W.; Hammond, D.

2007-12-01

43

Geothermal Resource Analysis and Structure of Basin and Range Systems, Especially Dixie Valley Geothermal Field, Nevada  

SciTech Connect

Publish new thermal and drill data from the Dizie Valley Geothermal Field that affect evaluation of Basin and Range Geothermal Resources in a very major and positive way. Completed new geophysical surveys of Dizie Valley including gravity and aeromagnetics and integrated the geophysical, seismic, geological and drilling data at Dizie Valley into local and regional geologic models. Developed natural state mass and energy transport fluid flow models of generic Basin and Range systems based on Dizie Valley data that help to understand the nature of large scale constraints on the location and characteristics of the geothermal systems. Documented a relation between natural heat loss for geothermal and electrical power production potential and determined heat flow for 27 different geothermal systems. Prepared data set for generation of a new geothermal map of North American including industry data totaling over 25,000 points in the US alone.

David Blackwell; Kenneth Wisian; Maria Richards; Mark Leidig; Richard Smith; Jason McKenna

2003-08-14

44

Materials selection guidelines for geothermal energy utilization systems  

SciTech Connect

This manual includes geothermal fluid chemistry, corrosion test data, and materials operating experience. Systems using geothermal energy in El Salvador, Iceland, Italy, Japan, Mexico, New Zealand, and the United States are described. The manual provides materials selection guidelines for surface equipment of future geothermal energy systems. The key chemical species that are significant in determining corrosiveness of geothermal fluids are identified. The utilization modes of geothermal energy are defined as well as the various physical fluid parameters that affect corrosiveness. Both detailed and summarized results of materials performance tests and applicable operating experiences from forty sites throughout the world are presented. The application of various non-metal materials in geothermal environments are discussed. Included in appendices are: corrosion behavior of specific alloy classes in geothermal fluids, corrosion in seawater desalination plants, worldwide geothermal power production, DOE-sponsored utilization projects, plant availability, relative costs of alloys, and composition of alloys. (MHR)

Ellis, P.F. II; Conover, M.F.

1981-01-01

45

Utah State Prison Geothermal System  

SciTech Connect

A geothermal space heating project was recently completed at the Utah State Prison complex at Crystal Hot Springs located near Murray, Utah. The project was initiated in 1978 as a joint U.S. Department of Energy and State of Utah project. Geologic and geophysical investigations initiated in 1979 consist of surface geologic mapping and aeromagnetic and detailed gravity surveys. This exploration program along with several shallow thermal-gradient holes provided the structural details for a subsequent exploration drilling program. The exploration drilling program involved deepening an existing well (SF-1) to 500 ft (150 m) and drilling a new hole (USP/TH-1) to 1000 ft (300 m) to test the extent of the thermal anomaly. Well SF-1 intersected 175)2)F(79)2)C) temperatures in a low permeable quartzite, and well USP/TH-1 intersected highly fractured quartzite in the lower section of the well. A temperature reversal was noted in USP/TH-1 below 700 ft (213 m) with a maximum temperature of 175)2)F(79)2)C) occurring in the zone from 300 to 700 ft (90 to 215 m). Flow testing of USP/TH-1 indicated the well would flow at 1000 gpm with a sustained flow of 400 gpm at a 3.5 psi drawdown over the heating season. Testing also indicated interference with other nearby wells and thermal springs. Fluid production for space heating of the prison facilities took place during the winter of 1983-84. This production will give more data to refine the calculations of reservoir producibility and provide information on the economics of utilizing geothermal fluids for space heating.

Mink, L.R.

1984-07-01

46

Geothermal system meets space heating requirements  

SciTech Connect

The Department of Veterans Affairs (VA) Medical center was built on the site of the former Fort Boise. Ten of the 21 buildings that comprise the Medical Center are holdovers from the Fort Boise era, including the 1850s vintage boiler plant and plumbing shop, which previously served as the Idaho territorial jail. Historically, steam for heating, humidification, sterilization, cooking and other uses was generated in a central boiler plant and piped to the various buildings by an underground distribution network. In the early 1980s, the VA began planning to replace the boilers and parts of the piping network that had been in service for nearly 70 years. Because the Medical Center was located near a geothermal water source, it was decided to use the geothermal energy wherever possible. Drilling for the geothermal production well began in August 1983. Testing of the well indicated that it would yield a flow of 1,100 gpm (69 L/s) at 160{degrees}F (71{degrees}C). Engineering calculations indicated that this flow could accommodate all of the space heating and domestic hot water heating needs of the Medical Center. This paper reports that, because the geothermal water supply would consist of a single pump in a single well and because this was a healthcare facility, a backup heat system was required. The obvious choice was the existing boiler plant.

Not Available

1992-03-01

47

Tracing Injection Fluids in Engineered Geothermal Systems  

NASA Astrophysics Data System (ADS)

The reinjection of produced fluids is crucial to the effective management of geothermal reservoirs, since it provides a mechanism for maintaining reservoir pressures while allowing for the disposal of a toxic byproduct. Tracers are essential to the proper location of injection wells since they are the only known tool for reliably characterizing the flow patterns of recirculated fluids. If injection wells are placed too close to production wells, then reinjected fluids do not have sufficient residence time to extract heat from the reservoir and premature thermal breakthrough results. If injection wells are placed too far away, then the reservoir risks unacceptable pressure loss. Several thermally stable compounds from a family of very detectable fluorescent organic compounds (the naphthalene sulfonates) were characterized and found to be effective for use as geothermal tracers. Through batch-autoclave reactions, their Arrhenius pseudo-first-order decay-rate constants were determined. An analytical method was developed that allows for the laboratory determination of concentrations in the low parts-per-trillion range. Field experiments in numerous geothermal reservoirs throughout the world have confirmed the laboratory findings. Whereas conservative tracers such as the naphthalene sulfonates are effective tools for indicating interwell flow patterns and for measuring reservoir pore volumes, 'reactive' tracers can be used to constrain fracture surface area, which is the effective area for heat extraction. This is especially important for engineered geothermal system (EGS) wells, since reactive tracers can be used to measure fracture surface area immediately after drilling and while the well stimulation equipment is still on site. The reactive properties of these tracers that can be exploited to constrain fracture surface area are reversible sorption, contrasting diffusivity, and thermal decay. Laboratory batch- and flow-reactor experiments in combination with numerical simulation studies have served to identify candidate compounds for use as reactive tracers. An emerging class of materials that show promise for use as geothermal and EGS tracers are colloidal nanocrystals (quantum dots). These are semiconductor particles that fluoresce as a function of particle size. Preliminary laboratory experimentation has demonstrated that these thermally stable, water-soluble particles can serve as conservative tracers for geothermal applications. Likewise, they show promise as potential reactive tracers, since their surfaces can be modified to be reversibly sorptive and their diameters are sufficiently large to allow for contrasts in diffusivity with solute tracers.

Rose, P. E.; Leecaster, K.; Mella, M.; Ayling, B.; Bartl, M. H.

2011-12-01

48

ELVIS: Multi-Electrolyte Aqueous Activity Model for Geothermal Solutions  

NASA Astrophysics Data System (ADS)

High temperature, pressure, and fluid salinities render geochemical modeling of fluid-rock interactions in Enhanced Geothermal Systems a demanding task. Accurate prediction of fluid-mineral equilibria strongly depends on the availability of thermodynamic data and activity models. Typically, the Pitzer activity model is applied for geothermal fluids. A drawback of this model is the large number of parameters required to account for temperature and pressure dependencies, which significantly reduces computational efficiency of reactive transport simulations. In addition, most available parameterizations are valid only at vapor-saturated conditions. As an alternative we implemented the EUNIQUAC local composition model [2] that needs substantially fewer fitting parameters. However, the current EUNIQUAC model design does not include provision for high temperature (>150°C) applications and lacks a formulation for pressure dependence. Therefore, its application to geothermal conditions requires a re-formulation and re-fitting of the model. We developed a new tool termed GEMSFIT that allows generic fitting of activity models (for aqueous electrolyte and non-electrolyte solutions) and equations of state implemented in our geochemical equilibrium solver GEM-Selektor (http://gems.web.psi.ch). GEMSFIT combines a PostgreSQL database for storing and managing the datasets of experimental measurements and interaction parameters, the parallelized genetic algorithm toolbox of MATLAB° for the parameter fitting, and an interface to the numerical kernel of GEM-Selektor to access activity models and perform chemical equilibrium calculations. Benchmarking of the partly re-parameterized EUNIQUAC model against Pitzer revealed that the former is less accurate, which can result in incorrect predictions of mineral precipitation/dissolution. Consequently, we modified the EUNIQUAC model and concurrently introduced a pressure dependence to be able to fit experimental data over wide ranges of pressure, temperature, and composition. The new model, called ELVIS, combines an electrostatic framework developed by Helgeson and coworkers [1] with non- electrostatic concepts derived from the EUNIQUAC model [2]. ELVIS has significantly less fitting parameters than the Pitzer approach, but is sufficiently accurate in predicting mineral solubility within experimental error. Results of first parameterizations of ELVIS to geothermal solutions (dilute to concentrated brines from ambient conditions to ~300°C and ~800bars) will be presented. [1] Helgeson, H. H., Kirkham, D. H., Flowers, G. C. (1981), Am. J. Sc. 281, 1249-1516. [2] Thomsen, K., Rasmussen, P., Gani, R. (1996), Chem. Eng. Sc. 51, 3675-3683.

Hingerl, F. F.; Wagner, T.; Driesner, T.; Kulik, D. A.; Kosakowski, G.

2011-12-01

49

National Geothermal Data System: Transforming the Discovery, Access, and Analytics of Data for Geothermal Exploration  

SciTech Connect

Compendium of Papers from the 38th Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California February 11-13, 2013 The National Geothermal Data System (NGDS) is a distributed, interoperable network of data collected from state geological surveys across all fifty states and the nation’s leading academic geothermal centers. The system serves as a platform for sharing consistent, reliable, geothermal-relevant technical data with users of all types, while supplying tools relevant for their work. As aggregated data supports new scientific findings, this content-rich linked data ultimately broadens the pool of knowledge available to promote discovery and development of commercial-scale geothermal energy production. Most of the up-front risks associated with geothermal development stem from exploration and characterization of subsurface resources. Wider access to distributed data will, therefore, result in lower costs for geothermal development. NGDS is on track to become fully operational by 2014 and will provide a platform for custom applications for accessing geothermal relevant data in the U.S. and abroad. It is being built on the U.S. Geoscience Information Network (USGIN) data integration framework to promote interoperability across the Earth sciences community. The basic structure of the NGDS employs state-of-the art informatics to advance geothermal knowledge. The following four papers comprising this Open-File Report are a compendium of presentations, from the 38th Annual Workshop on Geothermal Reservoir Engineering, taking place February 11-13, 2013 at Stanford University, Stanford, California. “NGDS Geothermal Data Domain: Assessment of Geothermal Community Data Needs,” outlines the efforts of a set of nationwide data providers to supply data for the NGDS. In particular, data acquisition, delivery, and methodology are discussed. The paper addresses the various types of data and metadata required and why simple links to existing data are insufficient for promoting geothermal exploration. Authors of this paper are Arlene Anderson, US DOE Geothermal Technologies Office, David Blackwell, Southern Methodist University (SMU), Cathy Chickering (SMU), Toni Boyd, Oregon Institute of Technology’s GeoHeat Center, Roland Horne, Stanford University, Matthew MacKenzie, Uberity, Joe Moore, University of Utah, Duane Nickull, Uberity, Stephen Richard, Arizona Geological Survey, and Lisa Shevenell, University of Nevada, Reno. “NGDS User Centered Design: Meeting the Needs of the Geothermal Community,” discusses the user- centered design approach taken in the development of a user interface solution for the NGDS. The development process is research based, highly collaborative, and incorporates state-of-the-art practices to ensure a quality user interface for the widest and greatest utility. Authors of this paper are Harold Blackman, Boise State University, Suzanne Boyd, Anthro-Tech, Kim Patten, Arizona Geological Survey, and Sam Zheng, Siemens Corporate Research. “Fueling Innovation and Adoption by Sharing Data on the DOE Geothermal Data Repository Node on the National Geothermal Data System,” describes the motivation behind the development of the Geothermal Data Repository (GDR) and its role in the NGDS. This includes the benefits of using the GDR to share geothermal data of all types and DOE’s data submission process. Authors of this paper are Jon Weers, National Renewable Energy Laboratory and Arlene Anderson, US DOE Geothermal Technologies Office. Finally, “Developing the NGDS Adoption of CKAN for Domestic & International Data Deployment,” provides an overview of the “Node-In-A-Box” software package designed to provide data consumers with a highly functional interface to access the system, and to ease the burden on data providers who wish to publish data in the system. It is important to note that this software package constitutes a reference implementation and that the NGDS architecture is based on open standards, which means other server software can make resources available, a

Patten, Kim [Arizona Geological Survey

2013-05-01

50

Geothermal Systems of the Yellowstone Caldera Field Trip Guide  

SciTech Connect

Geothermal studies are proceedings on two fronts in the West Yellowstone area. High-temperature resources for the generation of electricity are being sought in the Island Park area, and lower temperatures resources for direct applications, primarily space heating, are being explored for near the town of West Yellowstone. Potential electric geothermal development in the Island Park area has been the subject of widespread publicity over fears of damage to thermal features in Yellowstone Park. At the time of writing this guide, companies have applied for geothermal leases in the Island Park area, but these leases have not yet been granted by the US Forest Service. The Senate is now discussing a bill that would regulate geothermal development in Island Park; outcome of this debate will determine the course of action on the lease applications. The Island Park area was the site of two cycles of caldera activity, with major eruptions at 2.0 and 1.2 million years ago. The US Geological Survey estimates that 16,850 x 10{sup 18} joules of energy may remain in the system. Geothermal resources suitable for direct applications are being sought in the West Yellowstone vicinity by the Montana Bureau of Mines and Geology, under funding from the US Department of Energy. West Yellowstone has a mean annual temperature of 1-2 C. Research thus far suggests that basement rocks in the vicinity are at a depth of about 600 m and are probably similar to the rocks exposed north of Hebgen Lake, where Precambrian, Paleozoic and Mesozoic rocks have been mapped. A few sites with anomalously warm water have been identified near the town. Work is continuing on this project.

Foley, Duncan; Neilson, Dennis L.; Nichols, Clayton R.

1980-09-08

51

Active and Fossil Geothermal Activity at Lake Chapala, Mexico  

NASA Astrophysics Data System (ADS)

Geothermal systems are very abundant in the tectonically active zones of the earth's crust and the Citala rift, where Lake Chapala is located, is not the exception. The Lake Chapala basin is characterized by its paleo- and actual geothermal activity that includes: thermal springs, fossil sinter deposits and hydrothermal petroleum manifestations. Thermal springs occur both inside and outside the lake. The spring water in out-shore thermal springs around Lake Chapala is carbonate (Medina-Heredia A, 1986). To the NE area is San Luis Agua Caliente (69°C; ~ 240 mg L-1 [HCO3]1) in the NW at Jocotepec (36°C; ~263mg L-1 [HCO3]-); in the South we find Tuxcueca and Tizap n El Alto (30°C; 193 mg L-1 [HCO3]-). However, there is an exception, the spring water at the San Juan Cosal sector (North), which is sulfate (64-83°C; ~479 mg L-1, [SO4]-2). Examples of in-shore thermal springs are "Los Gorgos" (near South shore) and "El Fuerte" (near East shore and temporary "out-shore" because of actual severe drought); the characterisation of water of this in-shore sites is in progress. On the SE shore and five km NW from Regules village, outcrops a carbonate deposit named "La Calera". This carbonate fossil sinter outcrops 2 km in E-W direction and 600 m in N-S direction and overlays andesitic rock. With a thickness of approximately 5m and a roughly horizontal attitude, the carbonated sinter material is characterized by both massive and banded structure. When massive, it is colored in yellow brownish and grey and elsewhere it shows a pseudo-brecciated structure and when banded, alternated of yellow and dark millimetre bands can be seen; is characterized by vuggy porosity and silica (quartz and chalcedony) vein lets. Under microscope a pseudo-micritic texture is observed; vugs coated by iron oxides, are filled with calcite, and/or quartz, chalcedony and clay minerals. Six samples of carbonate of "La Calera" deposit were analysed for their stable isotopes (LODC-UParis VI). From ? 13CPDB values we have two set of data: one near zero (-8.03 to -8.69 \\permil) that means a no contribution of organic carbon and other with low values (-0.35 to -0.75 \\permil) meaning an important contribution of organic carbon; from very low ? 18OPDB values (-8.5 to -0.27 \\permil) we deduced a precipitation in meteoric water with a temperature deposition higher than the surface that matchs with an hydrothermal origin. Mineralogy was confirmed by XRD diffractometry. Near the sub-lacustrine spring "Los Gorgos" there are some small land spots which look like islands (<3-4 m2) made of solid bitumen and which are linked to the bottom of the lake. Because of these hydrocarbon manifestations the company Petróleos Mexicanos drilled (2,348 m deep), without success, an oil exploration well (L˘pez-Ramos, 1979). The characterisation of this solid bitumen is in progress.

Zârate-del Vall, P.

2002-12-01

52

Roosevelt Hot Springs geothermal system, Utah - case study  

Microsoft Academic Search

The Roosevelt Hot Springs geothermal system has been undergoing intensive exploration since 1974 and has been used as a natural laboratory for the development and testing of geothermal exploration methods by research organizations. This paper summarizes the geological, geophysical, and geochemistry data which have been collected since 1974, and presents a retrospective strategy describing the most effective means of exploration

H. P. Ross; D. L. Nielson; J. N. Moore

1982-01-01

53

Application of direct contact heat exchangers in geothermal systems  

Microsoft Academic Search

Two applications of direct-contact heat exchangers (DCHs) used in geothermal systems are examined. The first type of DCH is applied to a binary cycle where a secondary fluid is vaporized in contact with the brine (direct contact evaporator). The second type of DCH is applied to a geothermal power plant operating on water vapor only (direct contact condenser); in this

I. Oliker

1977-01-01

54

Boise geothermal system, western Snake River plain, Idaho  

Microsoft Academic Search

The Boise geothermal system lies in an area of high heat flow along the northern margin of the western Snake River plain. Exploratory drilling for petroleum and geothermal water, seismic reflection profiling, and regional gravity data permit construction of a detailed structure section across the western plain. A faulted acoustic basement of volcanic rocks lies at depths of 2400 to

S. H. Wood; W. L. Burnham

1984-01-01

55

Residential Vertical Geothermal Heat Pump System Models: Calibration to Data  

Microsoft Academic Search

A detailed component-based simulation model of a geothermal heat pump system has been calibrated to monitored data taken from a family housing unit located at Fort Polk, Louisiana. The simulation model represents the housing unit, geothermal heat pump, ground heat exchanger, thermostat, blower, and ground-loop pump. Each of these component models was 'tuned' to better match the measured data from

Jeff W. Thornton; T. P. McDowell; John A Shonder; Patrick Hughes; D. Pahud; G. Hellstrom

1997-01-01

56

Hydrogeological investigations on Balçova geothermal system in Turkey  

Microsoft Academic Search

The Balçova geothermal system is situated within the confines of Izmir City, Turkey. It is located along the Izmir Fault zone, trending E–W. It has formed a hot water reservoir that is currently exploited for district heating of the nearby Balçova-Narlidere area. Geoscientific studies on the area around the Balçova geothermal field indicate that regional tectonics coupled with a major

Umran Serpen

2004-01-01

57

Monitoring well systems in geothermal areas  

NASA Astrophysics Data System (ADS)

The ability to monitor the injection of spent geothermal fluids at reasonable cost might be greatly improved by use of multiple-completion techniques. Several such techniques, identified through contact with a broad range of experts from the groundwater and petroleum industries, are evaluated relative to application in the typical geologic and hydrologic conditions of the Basin and Range Province of the Western United States. Three basic monitor well designs are suggested for collection of pressure and temperature data: Single standpipe, multiple standpipe, and closed-system piezometers. The single standpipe piezometer is recommended for use at depths less than 152 m (500 ft); several can be clustered in one area to provide information on vertical flow conditions. At depths greater than 152 m (500 ft), the multiple-completion standpipe and closed-system piezometers are likely to be more cost effective.

Lofgren, B. E.; Orourke, J.; Sterrett, R.; Thackston, J.; Fain, D.

1981-01-01

58

United Nations geothermal activities in developing countries  

SciTech Connect

The United Nations implements technical cooperation projects in developing countries through its Department of Technical Cooperation for Development (DTCD). The DTCD is mandated to explore for and develop natural resources (water, minerals, and relevant infrastructure) and energy - both conventional and new and renewable energy sources. To date, the United Nations has been involved in over 30 geothermal exploration projects (completed or underway) in 20 developing countries: 8 in Africa (Djibouti, Ethiopia, Kenya, Madagascar); 8 in Asia (China, India, Jordan, Philippines, Thailand); 9 in Latin America (Bolivia, Chile, El Salvador, Honduras, Mexico, Nicaragua, Panama) and 6 in Europe (Greece, Romania, Turkey, Yugoslavia). Today, the DTCD has seven UNDP geothermal projects in 6 developing countries. Four of these (Bolivia, China, Honduras, and Kenya) are major exploration projects whose formulation and execution has been possible thanks to the generous contributions under cost-sharing arrangements from the government of Italy. These four projects are summarized.

Beredjick, N.

1987-07-01

59

GEOTHERM Data Set  

DOE Data Explorer

GEOTHERM is a comprehensive system of public databases and software used to store, locate, and evaluate information on the geology, geochemistry, and hydrology of geothermal systems. Three main databases address the general characteristics of geothermal wells and fields, and the chemical properties of geothermal fluids; the last database is currently the most active. System tasks are divided into four areas: (1) data acquisition and entry, involving data entry via word processors and magnetic tape; (2) quality assurance, including the criteria and standards handbook and front-end data-screening programs; (3) operation, involving database backups and information extraction; and (4) user assistance, preparation of such items as application programs, and a quarterly newsletter. The principal task of GEOTHERM is to provide information and research support for the conduct of national geothermal-resource assessments. The principal users of GEOTHERM are those involved with the Geothermal Research Program of the U.S. Geological Survey.

Jacob DeAngelo

60

Mapping temperature and radiant geothermal heat flux anomalies in the Yellowstone geothermal system using ASTER thermal infrared data  

USGS Publications Warehouse

The purpose of this work was to use satellite-based thermal infrared (TIR) remote sensing data to measure, map, and monitor geothermal activity within the Yellowstone geothermal area to help meet the missions of both the U.S. Geological Survey Yellowstone Volcano Observatory and the Yellowstone National Park Geology Program. Specifically, the goals were to: 1) address the challenges of remotely characterizing the spatially and temporally dynamic thermal features in Yellowstone by using nighttime TIR data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and 2) estimate the temperature, geothermal radiant emittance, and radiant geothermal heat flux (GHF) for Yellowstone’s thermal areas (both Park wide and for individual thermal areas). ASTER TIR data (90-m pixels) acquired at night during January and February, 2010, were used to estimate surface temperature, radiant emittance, and radiant GHF from all of Yellowstone’s thermal features, produce thermal anomaly maps, and update field-based maps of thermal areas. A background subtraction technique was used to isolate the geothermal component of TIR radiance from thermal radiance due to insolation. A lower limit for the Yellowstone’s total radiant GHF was established at ~2.0 GW, which is ~30-45% of the heat flux estimated through geochemical (Cl-flux) methods. Additionally, about 5 km2 was added to the geodatabase of mapped thermal areas. This work provides a framework for future satellite-based thermal monitoring at Yellowstone as well as exploration of other volcanic / geothermal systems on a global scale.

Vaughan, R. Greg; Lowenstern, Jacob B.; Keszthelyi, Laszlo P.; Jaworowski, Cheryl; Heasler, Henry

2012-01-01

61

Evaluation of Geothermal Heat Pump Systems under Various Conditions  

NASA Astrophysics Data System (ADS)

Experimental and numerical test were accomplished to evaluate the relations between the geothermal system and the hydrogeological condition. Sand tank experiment was designed. Combinations of different gradients and temperature gradients were applied for testing the real-time monitoring performance. Numerical modeling results were compared with the experimental data. Water injection-system imitating open- and closed-loop geothermal heat pumps were applied to estimate the change of the distribution of ambient groundwater temperature. The experimental results of different settings were used to estimate the effects of shallow depth geothermal energy utilization on the groundwater system.

Lee, S.; Bae, G.; Lee, K.

2006-12-01

62

Design, construction and evaluation of a simulated geothermal flow system  

SciTech Connect

A system was designed and built to simulate the flow from a geothermal well. The simulated flow will be used to power a Lysholm engine, the performance of which will then be evaluated for different simulated geothermal flows. Two main subjects are covered: 1) the design, construction and evaluation of the behavior of the system that simulates the geothermal flow; included in that topic is a discussion of the probable behavior of the Lysholm engine when it is put into operation, and 2) the investigation of the use of dynamic modeling techniques to determine whether they can provide a suitable means for predicting the behavior of the system.

Mackanic, J.C.

1980-07-28

63

MODELLING OF THE OHAAKI GEOTHERMAL SYSTEM  

Microsoft Academic Search

The Ohaaki Geothermal field is situated in the Taupo Volcanic Zone of New Zealand. It was the second geothermal field in New Zealand to be developed and is used primarily for electricity generation. Wells were first drilled in the Ohaaki field during the early 1960's. After a period of well testing following drilling, there was a long period of field

Juliet Newson; Michael O'Sullivan

64

Geothermal wells: A forecast of drilling activity  

NASA Astrophysics Data System (ADS)

Numbers and problems for geothermal wells expected to be drilled in the United States between 1981 and 2000 AD are forecasted. The 3800 wells forecasted for major electric powr projects (totaling 6 GWe of capacity) are categorized by type (production, etc.), and by location (The Geysers, etc.). 6000 wells are forecasted for direct heat projects (totaling 0.02 Quads per year). Equations are developed for forecasting the number of wells, and data is presented. Drilling and completion problems in The Geysers, The Imperial Valley, Roosevelt Hot Springs, the Valles Caldera, northern Nevada, Klamath Falls, Reno, Alaska, and Pagosa Springs are discussed. Likely areas for near term direct heat projects are identified.

Brown, G. L.; Mansure, A. J.; Miewald, J. N.

1981-07-01

65

Double-diffusive convection in geothermal systems: the salton sea, California, geothermal system as a likely candidate  

USGS Publications Warehouse

Much has been published about double-diffusive convection as a mechanism for explaining variations in composition and temperature within all-liquid natural systems. However, relatively little is known about the applicability of this phenomenon within the heterogeneous rocks of currently active geothermal systems where primary porosity may control fluid flow in some places and fractures may control it in others. The main appeal of double-diffusive convection within hydrothermal systems is-that it is a mechanism that may allow efficient transfer of heat mainly by convection, while at the same time maintaining vertical and lateral salinity gradients. The Salton Sea geothermal system exhibits the following reservoir characteristics: (1) decreasing salinity and temperature from bottom to top and center toward the sides, (2) a very high heat flow from the top of the system that seems to require a major component of convective transfer of heat within the chemically stratified main reservoir, and (3) a relatively uniform density of the reservoir fluid throughout the system at all combinations of subsurface temperature, pressure, and salinity. Double-diffusive convection can account for these characteristics very nicely whereas other previously suggested models appear to account either for the thermal structure or for the salinity variations, but not both. Hydrologists, reservoir engineers, and particularly geochemists should consider the possibility and consequences of double-diffusive convection when formulating models of hydrothermal processes, and of the response of reservoirs to testing and production. ?? 1990.

Fournier, R.O.

1990-01-01

66

Mantle Helium and Carbon Isotopes in Separation Creek Geothermal Springs, Three Sisters Area, Central Oregon: Evidence for Renewed Volcanic Activity or a Long Term Steady State System?  

USGS Publications Warehouse

Here we present the helium and carbon isotope results from the initial study of a fluid chemistry-monitoring program started in the summer of 2001 near the South Sister volcano in central Oregon. The Separation Creek area which is several miles due west of the volcano is the locus of strong crustal uplift currently occurring at a rate of 4-5 cm/yr (Wicks, et. al., 2001).Helium [RC/RA = 7.44 and 8.61 RA (RC/R A = (3He/4He)sample-. air corrected/(3He/4He)air))] and carbon (??13C = -11.59 to -9.03??? vs PDB) isotope data and CO2/3He (5 and 9 ?? 109) show that bubbling cold springs in the Separation Creek area near South Sister volcano carry a strong mantle signal, indicating the presence of fresh basaltic magma in the volcanic plumbing system. There is no evidence though, to directly relate this signal to the crustal uplift that is currently taking place in the area, which started in 1998. The geothermal system in the area is apparently much longer lived and shows no significant changes in chemistry compared to data from the early 1990s. Hot springs in the area, which are relatively far removed from the volcanic edifice, do not carry a strong mantle signal in helium isotope ratios (2.79 to 5.08 RA), unlike the cold springs, and also do not show any significant changes in helium isotope ratios compared to literature data for the same springs of over two decades ago. The cold springs of the Separation Creek area form a very diffuse but significant low temperature geothermal system, that should, due to its close vicinity to the center of up uplift, be more sensitive to changes in the deeper volcanic plumbing system than the far removed hot springs and therefore require much more study and consideration when dealing with volcano monitoring in the Cascade range or possibly with geothermal exploration in general.

Van Soest, M. C.; Kennedy, B.M.; Evans, W.C.; Mariner, R.H.

2002-01-01

67

Isotope Transport and Exchange within the Coso Geothermal System  

NASA Astrophysics Data System (ADS)

We are investigating the plumbing of the Coso geothermal system and the nearby Coso Hot Springs using finite element models of single-phase, variable-density fluid flow, conductive-convective heat transfer, fluid-rock isotope exchange, and groundwater residence times. Using detailed seismic reflection data and geologic mapping, we constructed a regional cross-sectional model that extends laterally from the Sierra Nevada to Wildhorse Mesa, west of the Argus Range. The base of the model terminates at the brittle-ductile transition zone. A sensitivity study was conducted using the model to explore the interaction between local and mountain front recharge, the effects of spatial variations in heat flow, and the role of permeable faults in controlling fluid circulation patterns. The model is constrained by present day bore hole temperature surveys, fluid inclusion temperatures, fluid-rock isotopic alteration patterns, and hot spring activity. While the results are non-unique, the analysis permits us to bracket the likely ranges of permeabilities and heat flow conditions that are consistent with observed data. Our findings suggest that active faults and seismogenic zones in and around the Coso geothermal area have much higher permeability and reactive surface areas than far field crustal rocks such as those in the Sierra Nevada. The Coso Wash fault zone must extend down to brittle- ductile transition zone depths of about 4 km in order for modeled results to match the observed hot spring activity.

Person, M.; Cohen, D.; Sabin, A.; Unruhn, J.; Gable, C.; Zyvoloski, G.; Monastero, F.

2006-12-01

68

Geophysical signatures of volcano-hosted geothermal systems.  

E-print Network

??Geophysical signatures of volcano-hosted geothermal systems in Indonesia are com-piled and synthesized. Parameters include electrical resistivity, seismicity, downhole logging, and pressure/temperature data; temperature and pressure… (more)

Raharjo, Imam Baru

2012-01-01

69

Investigation of Induced Seismicity from a Geothermal System, Neal Hot Springs, Eastern Oregon  

NASA Astrophysics Data System (ADS)

Newly acquired geophysical data from an eleven-seismometer network surrounding the Neal Hot Springs (NHS) Geothermal Power Plant in eastern Oregon was analyzed for induced seismicity and geothermal fluid flow. Major faults associated with the Oregon-Idaho Graben and the western Snake River Plain provides pathways for deep geothermal fluid flow for the NHS hot-water system. Our short-period seismic stations, can detect regional events not in published earthquake catalogs. These stations have been collecting seismic data from the initiation of the geothermal system's development through fluid injection tests this past summer. Background seismic values were acquired before plant production to measure natural geothermal fluid activity, but no natural fluid flow seismicity was identified. Two local events located less than 10 km to the northeast of NHS along with a catalogued, 2.8 M regional event 200 km away were identified in the data set, verifying the sensitivity and capability of the passive seismic network to capture events that were to occur at NHS. We monitored seismic activity from production and development with 4-8 hour durations for the past 15 months. We identify repeated signals at approximately 2 Hz that likely represent fluid injection or drilling cycles. However, induced earthquakes were not identified during production activities. The lack of microseismic events could be the result of the shallow depth of the geothermal resource, approximately 850 m below the earth surface. Future studies include a receiver function analysis to determine crustal boundaries beneath NHS, along with further monitoring of induced seismicity due to geothermal fluid flow as the geothermal power plant comes online.

Brenn, G. R.; Liberty, L. M.; Van Wijk, K.; Shaltry, D.; Colwell, C.

2012-12-01

70

Investigation of geothermal energy technologies and gas turbine hybrid systems  

SciTech Connect

This paper presents a preliminary study of the technical and economic feasibilities of integrating gas turbine systems into geothermal technologies. Levelized cost analysis employing revenue requirement approach was used to measure the economic feasibility of the geothermal and gas turbine hybrids at different geothermal sites. Twelve geothermal resource areas were included in this study; Brawley, CA, Coso Hot Springs, CA, Dixie Valley, NV, East Mesa, CA, Glass Mountain, CA, Heber, CA, Mono-Long Valley, CA, Salton Sea, CA, Stillwater, NV, Surprise Valley, CA, Vale, OR, and Wabuska, NV. The geothermal power generation technologies included in this study were air-cooled subcritical binary, condensate-cooled dual flash, and gas turbine hybrids of these two technologies. Geothermal/gas turbine concepts can be cost-effective at many geothermal resource areas. This study indicated that integrating gas turbine systems using GE LM2500 with binary cycles is potentially more cost effective than stand alone binary power plants in low temperature resource areas such as East Mesa, CA, Heber, CA, Stillwater, NV, Vale, OR and Wabuska, NV. In addition, this study showed that dual flash/gas turbine hybrid power plants maybe considered for higher temperature resources with high O&M costs.

Tiangco, V.; McCluer, P.; Hughes, E.

1996-12-31

71

Magnetotelluric imaging of the Reporoa geothermal system in New Zealand  

NASA Astrophysics Data System (ADS)

The Reporoa geothermal area is located in a caldera on the eastern side of the Taupo Volcanic Zone in the North Island of New Zealand. For the last 40 years scientists have argued whether Reporoa is an independent geothermal system or just an outflow structure of the Waiotapu geothermal system to the north. Due to its location and possible connection to the Waiotapu geothermal system, which is a protected system and a big tourist attraction, the Reporoa system needs to be well characterised before commercial exploitation can be considered. Early DC resistivity surveys yielded information to depths of about 1 km, but were unable to resolve which, if either, of the two competing models was correct. In this project we electrically image much deeper structures beneath the Reporoa geothermal area in order to understand better this system. MT is a passive geophysical exploration tool that utilises naturally-occurring, time-varying electromagnetic (EM) fields recorded on the surface to determine spatial variations in subsurface electrical resistivity. Temperature, porosity and fluid content, as well as hydrothermal alteration processes, have significant effects on patterns of subsurface electrical resistivity. Therefore, MT is well suited to image the different parts of a geothermal system, and is accordingly the most utilized geophysical imaging technique in geothermal research. For this study close to 100 broadband Magnetotelluric (MT) measurements, acquired during several separate surveys over a 3 year period, were analysed and modelled. Station spacing varied from 500 m to 2 km forming a grid over the study area. The maximum depth of investigation for this study, which is a function of the subsurface resistivity and the maximum period of measurement (100 s), is of the order of several kilometres. This paper will describe the data acquired and models derived. Preliminary results from this study indicate both an outflow structure from Waiotapu at shallow depths and an independent geothermal upflow at depth.

Walter, Christina; Jones, Alan G.; Ryan, Graham A.

2013-04-01

72

Monitoring well systems in geothermal areas  

SciTech Connect

The ability to monitor the injection of spent geothermal fluids at reasonable cost might be greatly improved by use of multiple-completion techniques. Several such techniques, identified through contact with a broad range of experts from the groundwater and petroleum industries, are evaluated relative to application in the typical geologic and hydrologic conditions of the Basin and Range Province of the Western United States. Three basic monitor well designs are suggested for collection of pressure and temperature data: Single standpipe, multiple standpipe, and closed-system piezometers. A fourth design, monitor well/injection well dual completions, is determined to be inadvisable. Also, while it is recognized that water quality data is equally important, designs to allow water sampling greatly increase costs of construction, and so such designs are not included in this review. The single standpipe piezometer is recommended for use at depths less than 152 m (500 ft); several can be clustered in one area to provide information on vertical flow conditions. At depths greater than 152 m (500 ft), the multiple-completion standpipe and closed-system piezometers are likely to be more cost effective. Unique conditions at each monitor well site may necessitate consideration of the single standpipe piezometer even for deeper completions.

Lofgren, B.E.; O'Rourke, J.; Sterrett, R.; Thackston, J.; Fain, D.

1982-03-01

73

A problem posed by vapour-dominated geothermal systems  

Microsoft Academic Search

Vapor-dominated geothermal systems present an apparently extraordinary physical phenomenon - a layer of water lying stably on a body of steam. The first geothermal exploitation at Lardarello, Italy, was in such an area. An analysis of the gravitational stability of water over steam in a porous medium is presented here. This shows that the near-surface condensate layer of a vapor-dominated

G. Schubert; J. M. Straus; M. A. Grant

1980-01-01

74

Enhanced Geothermal Systems (EGS) R&D Program  

SciTech Connect

The purpose of this workshop was to develop technical background facts necessary for planning continued research and development of Enhanced Geothermal Systems (EGS). EGS are geothermal reservoirs that require improvement of their permeability or fluid contents in order to achieve economic energy production. The initial focus of this R&D program is devising and testing means to extract additional economic energy from marginal volumes of hydrothermal reservoirs that are already producing commercial energy. By mid-1999, the evolution of the EGS R&D Program, begun in FY 1988 by the U.S. Department of Energy (DOE), reached the stage where considerable expertise had to be brought to bear on what technical goals should be pursued. The main purpose of this Workshop was to do that. The Workshop was sponsored by the Office of Geothermal Technologies of the Department of Energy. Its purpose and timing were endorsed by the EGS National Coordinating Committee, through which the EGS R&D Program receives guidance from members of the U.S. geothermal industry. Section 1.0 of this report documents the EGS R&D Program Review Session. There, managers and researchers described the goals and activities of the program. Recent experience with injection at The Geysers and analysis of downhole conditions at Dixie Valley highlighted this session. Section 2.0 contains a number of technical presentations that were invited or volunteered to illuminate important technical and economic facts and opportunities for research. The emphasis here was on fi.acture creation, detection, and analysis. Section 3.0 documents the initial general discussions of the participants. Important topics that emerged were: Specificity of defined projects, Optimizing cost effectiveness, Main technical areas to work on, Overlaps between EGS and Reservoir Technology R&D areas, Relationship of microseismic events to hydraulic fractures, and Defining criteria for prioritizing research thrusts. Sections 4.0 and 5.0 report the meat of the Workshop. Section 4.0 describes the nomination and clarification of technical thrusts, and Section 5.0 reports the results of prioritizing those thrusts via voting by the participants. Section 6.0 contains two discussions conducted after the work on research thrusts. The topics were ''Simulation'' and ''Stimulation''. A number of technical points that emerged here provide important guidance for both practical field work on EGS systems and for research.

Entingh, Daniel J.

1999-08-18

75

Geothermics 35 (2006) 368408 Tectonic and magmatic evolution of the active  

E-print Network

Geothermics 35 (2006) 368­408 Tectonic and magmatic evolution of the active volcanic front in El Salvador: insight into the Berl´in and Ahuachap´an geothermal areas Samuele Agostinia,, Giacomo Cortia products, at least during the Plio-Quaternary. Detailed analyses within the geothermal fields of Berl

Doglioni, Carlo

76

Ground Source Heat Pumps - Geothermal Energy for Anyone, Anywhere: Current Worldwide Activity  

Microsoft Academic Search

At WGC 1995 in Florence a paper was presented that brought to the attention of the worldwide geothermal community the increasing activity in geothermal heat pumps. With increasing pressures for reductions in building energy consumption and rising targets for reductions in CO2 emissions from buildings, the drivers for installing geothermal heat pumps are all going in the right direction. An

R. Curtis; J. Lund; B. Sanner; L. Rybach; G. Hellström

77

Thermodynamic analysis of a hybrid geothermal heat pump system  

Microsoft Academic Search

A thermodynamic analysis of a hybrid geothermal heat pump system is carried out. Mass, energy, and exergy balances are applied to the system, which has a cooling tower as a heat rejection unit, and system performance is evaluated in terms of coefficient of performance and exergy efficiency. The heating coefficient of performance for the overall system is found to be

Luthfi I. Lubis; Mehmet Kanoglu; Ibrahim Dincer; Marc A. Rosen

2011-01-01

78

Campi Flegrei Deep Drilling Project and geothermal activities in Campania Region (Southern Italy)  

NASA Astrophysics Data System (ADS)

The Campanian volcanic area has a huge geothermal potential (Carlino et al., 2012), similar to the Larderello-Radicondoli-Amiata region, in Tuscany (Italy), which has been the first site in the World exploited for electric production. Recently, the Campi Flegrei Deep Drilling Project (CFDDP), sponsored by ICDP and devoted to understand and mitigate the extreme volcanic risk in the area, has also risen new interest for geothermal exploration in several areas of Italy. Following the new Italian regulations which favour and incentivise innovative pilot power plants with zero emission, several geothermal projects have started in the Campania Region, characterized by strict cooperation among large to small industries, Universities and public Research Centers. INGV department of Naples (Osservatorio Vesuviano) has the technical/scientific leadership of such initiatives. Most of such projects are coordinated in the framework of the Regional District for Energy, in which a large part is represented by geothermal resource. Leading geothermal projects in the area include 'FORIO' pilot plant project, aimed to build two small (5 MWe each one) power plants in the Ischia island and two projects aimed to build pilot power plants in the Agnano-Fuorigrotta area in the city of Naples, at the easternmost part of Campi Flegrei caldera. One of the Campi Flegrei projects, 'SCARFOGLIO', is aimed to build a 5 MWe geothermal power plant in the Agnano area, whereas the 'START' project has the goal to build a tri-generation power plant in the Fuorigrotta area, fed mainly by geothermal source improved by solar termodynamic and bio-mass. Meanwhile such projects enter the field work operational phase, the pilot hole drilling of the CFDDP project, recently completed, represents an important experience for several operational aspects, which should contitute an example to be followed by the next geothermal activities in the area. It has been furthermore a source of valuable data for geothermal characterization of the Agnano-Fuorigrotta area, despite its mainly volcanological goals. In particular, the drilling site was equipped with dense and multidisciplinary continuous monitoring systems, an example to follow anyway to assure the minimum impact on such densely urbanised areas. Furthermore, innovative leak-off experiments mainly aimed to permeability and strength/stress measurements have been developed and tested. Such tests show permeability values before water injection between 10-14 and 10-15 m2 and, moreover, put in evidence a significant local increase of permeability obtained at the end of the injection experiment.

De Natale, Giuseppe; Troise, Claudia; Troiano, Antonio; Giulia Di Giuseppe, Maria; Mormone, Angela; Carlino, Stefano; Somma, Renato; Tramelli, Anna; Vertechi, Enrico; Sangianantoni, Agata; Piochi, Monica

2013-04-01

79

Investigation of a fossil geothermal system, Hamblin-Cleopatra Volcano, Clark County, Nevada. Final technical report  

SciTech Connect

The Hamblin-Cleopatra volcano, selected for study because erosion and fault displacement have exposed the entire volcanic succession, the intrusive core, a radial dike systems, and sedimentary and volcanic rocks that predate and postdate the volcano, was investigated to estimate the proportions of igneous materials forming lava flows, pyroclastic deposits, intrusive bodies, and reworked debris. Chemical changes in the magma throughout the active period of the volcano were documented. The geothermal system active within the pile after activity ceased was reconstructed. (ACR)

Barker, D.S.

1986-07-28

80

Chemistry and Materials in Geothermal Systems.  

National Technical Information Service (NTIS)

The development of a geothermal fluid, from its origin as meteoric water precipitating on the earth's surface, as it flows through the soils and rocks of geological formations, to the point where it returns to the surface as a hot spring, geyser, well, et...

R. L. Miller

1979-01-01

81

Monitoring well systems in geothermal areas  

Microsoft Academic Search

The ability to monitor the injection of spent geothermal fluids at reasonable cost might be greatly improved by use of multiple-completion techniques. Several such techniques, identified through contact with a broad range of experts from the groundwater and petroleum industries, are evaluated relative to application in the typical geologic and hydrologic conditions of the Basin and Range Province of the

B. E. Lofgren; J. Orourke; R. Sterrett; J. Thackston; D. Fain

1981-01-01

82

Monitoring well systems in geothermal areas  

Microsoft Academic Search

The ability to monitor the injection of spent geothermal fluids at reasonable cost might be greatly improved by use of multiple-completion techniques. Several such techniques, identified through contact with a broad range of experts from the groundwater and petroleum industries, are evaluated relative to application in the typical geologic and hydrologic conditions of the Basin and Range Province of the

B. E. Lofgren; J. ORourke; R. Sterrett; J. Thackston; D. Fain

1982-01-01

83

Geothermal direct applications hardware systems development and testing. 1979 summary report  

SciTech Connect

Activities performed during calendar year 1979 for the hardware system development and testing task are presented. The fluidized bed technology was applied to the drying of potato by-products and to the exchange of heat to air in the space heating experiment. Geothermal water was flashed to steam and also used as the prime energy source in the steam distillation of peppermint oil. Geothermal water temperatures as low as 112.8/sup 0/C were utilized to distill alcohol from sugar beet juice, and lower temperature water provided air conditioning through an absorption air conditioning system. These experiments are discussed.

Keller, J.G.

1980-03-01

84

A market survey of geothermal wellhead power generation systems  

NASA Technical Reports Server (NTRS)

The market potential for a portable geothermal wellhead power conversion device is assessed. Major study objectives included identifying the most promising applications for such a system, the potential impediments confronting their industrialization, and the various government actions needed to overcome these impediments. The heart of the study was a series of structured interviews with key decision-making individual in the various disciplines of the geothermal community. In addition, some technical and economic analyses of a candidate system were performed to support the feasibility of the basic concept.

Leeds, M. W.

1978-01-01

85

Recommendations of the workshop on advanced geothermal drilling systems  

SciTech Connect

At the request of the U.S. Department of Energy, Office of Geothermal Technologies, Sandia National Laboratories convened a group of drilling experts in Berkeley, CA, on April 15-16, 1997, to discuss advanced geothermal drilling systems. The objective of the workshop was to develop one or more conceptual designs for an advanced geothermal drilling system that meets all of the criteria necessary to drill a model geothermal well. The drilling process was divided into ten essential functions. Each function was examined, and discussions were held on the conventional methods used to accomplish each function and the problems commonly encountered. Alternative methods of performing each function were then listed and evaluated by the group. Alternative methods considered feasible or at least worth further investigation were identified, while methods considered impractical or not potentially cost-saving were eliminated from further discussion. This report summarizes the recommendations of the workshop participants. For each of the ten functions, the conventional methods, common problems, and recommended alternative technologies and methods are listed. Each recommended alternative is discussed, and a description is given of the process by which this information will be used by the U.S. DOE to develop an advanced geothermal drilling research program.

Glowka, D.A.

1997-12-01

86

Mathematical modeling of the behavior of geothermal systems under exploitation  

SciTech Connect

Analytical and numerical methods have been used in this investigation to model the behavior of geothermal systems under exploitation. The work is divided into three parts: (1) development of a numerical code, (2) theoretical studies of geothermal systems, and (3) field applications. A new single-phase three-dimensional simulator, capable of solving heat and mass flow problems in a saturated, heterogeneous porous or fractured medium has been developed. The simulator uses the integrated finite difference method for formulating the governing equations and an efficient sparse solver for the solution of the linearized equations. In the theoretical studies, various reservoir engineering problems have been examined. These include (a) well-test analysis, (b) exploitation strategies, (c) injection into fractured rocks, and (d) fault-charged geothermal reservoirs.

Bodvarsson, G.S.

1982-01-01

87

Groundwater Monitoring and Engineered Geothermal Systems: The Newberry EGS Demonstration  

NASA Astrophysics Data System (ADS)

Engineered Geothermal Systems (EGS) represent the next generation of geothermal energy development. Stimulation of multiple zones within a single geothermal reservoir could significantly reduce the cost of geothermal energy production. Newberry Volcano in central Oregon represents an ideal location for EGS research and development. As such, the goals of the Newberry EGS Demonstration, operated by AltaRock Energy, Inc., include stimulation of a multiple-zone EGS reservoir, testing of single-well tracers and a demonstration of EGS reservoir viability through flow-back and circulation tests. A shallow, local aquifer supplied the approximately 41,630 m3 (11 million gals) of water used during stimulation of NWG 55-29, a deep geothermal well on the western flank of Newberry Volcano. Protection of the local aquifer is of primary importance to both the Newberry EGS Demonstration and the public. As part of the Demonstration, AltaRock Energy, Inc. has developed and implemented a groundwater monitoring plan to characterize the geochemistry of the local aquifer before, during and after stimulation. Background geochemical conditions were established prior to stimulation of NWG 55-29, which was completed in 2012. Nine sites were chosen for groundwater monitoring. These include the water supply well used during stimulation of NWG 55-29, three monitoring wells, three domestic water wells and two hot seeps located in the Newberry Caldera. Together, these nine monitoring sites represent up-, down- and cross-gradient locations. Groundwater samples are analyzed for 25 chemical constituents, stable isotopes, and geothermal tracers used during stimulation. In addition, water level data is collected at three monitoring sites in order to better characterize the effects of stimulation on the shallow aquifer. To date, no significant geochemical changes and no geothermal tracers have been detected in groundwater samples from these monitoring sites. The Newberry EGS Demonstration groundwater monitoring program is currently on-going.

Grasso, K.; Cladouhos, T. T.; Garrison, G.

2013-12-01

88

Structural compartmentalisation of a geothermal system, the Torre Alfina field (central Italy)  

NASA Astrophysics Data System (ADS)

Recent surging of renewed industrial interest in the exploration of low and medium enthalpy geothermal fields makes the accurate assessment of the geothermal potential essential to minimise uncertainties during both exploration and exploitation. The Torre Alfina field is a case of abandoned, but promising, geothermal field of central Italy where the roles of the internal structural setting and of the recharge areas on the hydrothermal circulation are largely unconstrained. In this paper, field structural data integrated with geomorphic lineament analysis document the occurrence of post-orogenic deformation structures controlling the compartmentalisation of the Torre Alfina geothermal field. Strike-slip and subordinate normal fault systems (with associated network fractures) cut and dislocate the internal architecture of the reservoir and prevent its hydraulic connection with Mount Cetona, considered to be the recharge area and where hydrothermal manifestation, including travertine deposition, occurs. 230Th/234U radiometric dating of superposed travertine units gives 200, 120 and 90 ka respectively, inferred to correspond to the age of the fossil hydrothermal circulation during tectonic activity. The results have been used for illustrating a new geological conceptual model for the Torre Alfina area where the geothermal system is composed of different compartments. Tectonic structures define the main boundaries between compartments, helping the understanding of why productive and non-productive wells were found in apparently similar structural settings within the Torre Alfina field.

Vignaroli, Gianluca; Pinton, Annamaria; De Benedetti, Arnaldo A.; Giordano, Guido; Rossetti, Federico; Soligo, Michele; Berardi, Gabriele

2013-11-01

89

Recent Development of HFR Geothermal Reservoir System in Australia  

NASA Astrophysics Data System (ADS)

Since the 1970's, a number of research programmes have worked towards developing Hot Dry Rock technology (HDR) for geothermal energy which has been renamed as Hot Fractured Rock (HFR) in Australia. The HFR energy resource has the potential to supply base-load power with no greenhouse gas emissions. This paper will introduce the recent development of HFR geothermal reservoir system in Australia and focus on our related outcomes on numerical software development and field site operation as follows: (1). Geodynamics Limited is continuing to develop a world-class, high-grade geothermal energy resource contained in high temperature granites beneath the Cooper Basin in NE South Australia, which represents the largest known geothermal resource in the world and has the potential to supply 1000's MWe of low cost power to the national grid. The first deep well has reached a depth of over 4,400m, with temperatures exceeding 250şC. Subsequent to drilling the well, a hydraulic stimulation programme resulted in the development of a large underground heat exchanger(reservoir). The encountered conditions of the hot granite are more favourable than expected. The economic feasibility of extracting heat from this reservoir will be established through a circulation test at 4,500m with the drilling of the production well. (2) Geothermal reservoir system as above involves the thermal, fluid and mechanical behaviour of geo-materials and natural seismic events, and potential geological perturbations to the geothermal reservoir. With the ARC Linkage grant, a 3D finite element based computational model and software for simulating a multi-scale highly coupled thermo-hydro-mechanical geo-mechanical system on the parallel supercomputer are being developed and preliminarily applied to analyze the Cooper Basin based on the available filed site data as above.

Xing, H.; Wyborn, D.; Xu, H.; Yin, C.; Mora, P.

2006-12-01

90

Tectonic and Structural Controls of Geothermal Activity in the Great Basin Region, Western USA  

NASA Astrophysics Data System (ADS)

We are conducting a thorough inventory of structural settings of geothermal systems (>400 total) in the extensional to transtensional Great Basin region of the western USA. Most of the geothermal systems in this region are not related to upper crustal magmatism and thus regional tectonic and local structural controls are the most critical factors controlling the locations of the geothermal activity. A system of NW-striking dextral faults known as the Walker Lane accommodates ~20% of the North American-Pacific plate motion in the western Great Basin and is intimately linked to N- to NNE-striking normal fault systems throughout the region. Overall, geothermal systems are concentrated in areas with the highest strain rates within or proximal to the eastern and western margins of the Great Basin, with the high temperature systems clustering in transtensional areas of highest strain rate in the northwestern Great Basin. Enhanced extension in the northwestern Great Basin probably results from the northwestward termination of the Walker Lane and the concomitant transfer of dextral shear into west-northwest directed extension, thus producing a broad transtensional region. The capacity of geothermal power plants also correlates with strain rates, with the largest (hundreds of megawatts) along the Walker Lane or San Andreas fault system, where strain rates range from 10-100 nanostrain/yr to 1,000 nanostrain/yr, respectively. Lesser systems (tens of megawatts) reside in the Basin and Range (outside the Walker Lane), where local strain rates are typically < 10 nanostrain/yr. Of the 250+ geothermal fields catalogued, step-overs or relay ramps in normal fault zones serve as the most favorable setting, hosting ~32% of the systems. Such areas have multiple, overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) intersections between normal faults and strike-slip or oblique-slip faults (27%), where multiple minor faults connect major structures and fluids can flow readily through highly fractured, dilational quadrants, and b) normal fault terminations or tip-lines (22%), where horse-tailing generates closely-spaced faults and increased permeability. Other settings include accommodation zones (i.e., belts of intermeshing, oppositely dipping normal faults; 8%), major range-front faults (5-6%), and pull-aparts in strike-slip faults (4%). In addition, Quaternary faults lie within or near most systems. The relative scarcity of geothermal systems along displacement-maxima of major normal faults may be due to reduced permeability in thick zones of clay gouge and periodic release of stress in major earthquakes. Step-overs, terminations, intersections, and accommodation zones correspond to long-term, critically stressed areas, where fluid pathways are more likely to remain open in networks of closely-spaced, breccia-dominated fractures. These findings may help guide future exploration efforts, especially for blind geothermal systems, which probably comprise the bulk of the geothermal resources in the Great Basin.

Faulds, J. E.; Hinz, N.; Kreemer, C. W.

2012-12-01

91

Dual-temperature Kalina cycle for geothermal-solar hybrid power systems  

E-print Network

This thesis analyzes the thermodynamics of a power system coupling two renewable heat sources: low-temperature geothermal and a high-temperature solar. The process, referred to as a dual-temperature geothermal-solar Kalina ...

Boghossian, John G

2011-01-01

92

Modeling and analysis of hybrid geothermal-solar thermal energy conversion systems  

E-print Network

Innovative solar-geothermal hybrid energy conversion systems were developed for low enthalpy geothermal resources augmented with solar energy. The goal is to find cost-effective hybrid power cycles that take advantage of ...

Greenhut, Andrew David

2010-01-01

93

Towards the Design of Effective Engineered Geothermal Systems  

NASA Astrophysics Data System (ADS)

Stimulation of a potential engineered geothermal systems (EGS) reservoir by fluid pressurization -and hydraulic fracturing - is affected significantly by several factors including, the in situ state of stress; pre-existing natural fractures and fracture systems in the rock mass, disposition and mechanical properties of the fractures; and rock mass permeability as influenced by the stimulation process. Little information on these critical variables is available in advance of stimulation, so that design of stimulation treatments involves considerable uncertainty. Significant advances are being made in numerical modeling for application to engineering of these and similarly complex subsurface systems. It is now possible, for example, to examine how uncertainty and lack of knowledge of various factors, such as those mentioned above, affect the overall uncertainty of an actual stimulation. Numerical modeling of fracture systems has made significant advances and is being applied by the authors to indicate the influence of the factors described above, and how associated uncertainties may affect the outcome of practical fracturing programs. It is essential that numerical studies be complemented by geophysical observations. Micro-seismic activity and P and S wave velocity changes during and after stimulation are valuable tools to assist in verifying model predictions and development of a better overall understanding of the process of hydraulic fracturing on the field scale. Fundamental studies supported by laboratory investigations can also contribute significantly to improved understanding. Results of progress to date from such studies will be discussed.

Pettitt, W.; Damjanac, B.; Detournay-Piette, C.; Cundall, P. A.; Riahi, A.; Fairhurst, C.

2012-12-01

94

Fluid origin, gas fluxes and plumbing system in the sediment-hosted Salton Sea Geothermal System (California, USA)  

E-print Network

Fluid origin, gas fluxes and plumbing system in the sediment-hosted Salton Sea Geothermal System Available online 12 June 2011 Keywords: Salton Sea Geothermal System hydrothermal seeps gas and water geochemistry flux measurements mantle The Salton Sea Geothermal System (California) is an easily accessible

Svensen, Henrik

95

COTHERM: Geophysical Modeling of High Enthalpy Geothermal Systems  

NASA Astrophysics Data System (ADS)

In recent years geothermal heating and electricity generation have become an attractive alternative energy resource, especially natural high enthalpy geothermal systems such as in Iceland. However, the financial risk of installing and operating geothermal power plants is still high and more needs to be known about the geothermal processes and state of the reservoir in the subsurface. A powerful tool for probing the underground system structure is provided by geophysical techniques, which are able to detect flow paths and fracture systems without drilling. It has been amply demonstrated that small-scale features can be well imaged at shallow depths, but only gross structures can be delineated for depths of several kilometers, where most high enthalpy systems are located. Therefore a major goal of our study is to improve geophysical mapping strategies by multi-method geophysical simulations and synthetic data inversions, to better resolve structures at greater depth, characterize the reservoir and monitor any changes within it. The investigation forms part of project COTHERM - COmbined hydrological, geochemical and geophysical modeling of geoTHERMal systems - in which a holistic and synergistic approach is being adopted to achieve multidisciplinary cooperation and mutual benefit. The geophysical simulations are being performed in combination with hydrothermal fluid flow modeling and chemical fluid rock interaction modeling, to provide realistic constraints on lithology, pressure, temperature and fluid conditions of the subsurface. Two sites in Iceland have been selected for the study, Krafla and Reykjanes. As a starting point for the geophysical modeling, we seek to establish petrophysical relations, connecting rock properties and reservoir conditions with geophysical parameters such as seismic wave speed, attenuation, electrical conductivity and magnetic susceptibility with a main focus on seismic properties. Therefore, we follow a comprehensive approach involving three components: (1) A literature study to find relevant, existing theoretical models, (2) laboratory determinations to confirm their validity for Icelandic rocks of interest and (3) a field campaign to obtain in-situ, shallow rock properties from seismic and resistivity tomography surveys over a fossilized and exhumed geothermal system. Theoretical models describing physical behavior for rocks with strong inhomogeneities, complex pore structure and complicated fluid-rock interaction mechanisms are often poorly constrained and require the knowledge about a wide range of parameters that are difficult to quantify. Therefore we calibrate the theoretical models by laboratory measurements on samples of rocks, forming magmatic geothermal reservoirs. Since the samples used in the laboratory are limited in size, and laboratory equipment operates at much higher frequency than the instruments used in the field, the results need to be up-scaled from the laboratory scale to field scale. This is not a simple process and entails many uncertainties.

Grab, Melchior; Maurer, Hansruedi; Greenhalgh, Stewart

2014-05-01

96

Methanotrophic activity and bacterial diversity in volcanic-geothermal soils at Pantelleria island (Italy)  

NASA Astrophysics Data System (ADS)

Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic/geothermal soils are source of methane, but also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission was previously estimated in about 2.5 t a-1. Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values up to 950 ng g-1 dry soil h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile and the maximum methane consumption was measured in the top-soil layer but values > 100 ng g-1 h-1 were maintained up to a depth of 15 cm. The highest consumption rate was measured at 37 °C, but a still recognizable consumption at 80 °C (> 20 ng g-1 h-1) was recorded. In order to estimate the bacterial diversity, total soil DNA was extracted from Favara Grande and analysed using a Temporal Temperature Gradient gel Electrophoresis (TTGE) analysis of the amplified bacterial 16S rRNA gene. The three soil samples were probed by PCR using standard proteobacterial primers and newly designed verrucomicrobial primers targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected in sites FAV2 and FAV3, but not in FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site FAV2 pointed out a high diversity of gammaproteobacterial methanotrophs distantly related to Methylococcus/Methylothermus genera and the presence of the newly discovered acido-thermophilic methanotrophs Verrucomicrobia. Alphaproteobacteria of the genus Methylocystis were isolated from enrichment cultures, under a methane containing atmosphere at 37 °C. The isolates grow at pH 3.5-8 and temperatures of 18-45 °C, and show a methane oxidation rate of ~ 450 ?mol mol-1 h-1. Soils from Favara Grande showed the largest diversity of methanotrophic bacteria until now detected in a geothermal soil. While methanotrophic Verrucomicrobia are reported to dominate highly acidic geothermal sites, our results suggest that slightly acidic soils, in high enthalpy geothermal systems, host a more diverse group of both culturable and uncultivated methanotrophs.

Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

2014-04-01

97

Methanotrophic activity and diversity of methanotrophs in volcanic geothermal soils at Pantelleria (Italy)  

NASA Astrophysics Data System (ADS)

Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic or geothermal soils are not only a source of methane, but are also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria (Italy), Favara Grande, whose total methane emission was previously estimated at about 2.5 Mg a-1 (t a-1). Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values of up to 59.2 nmol g-1 soil d.w. h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile, the maximum methane consumption was measured in the top-soil layer, and values greater than 6.23 nmol g-1 h-1 were still detected up to a depth of 13 cm. The highest consumption rate was measured at 37 °C, but a still detectable consumption at 80 °C (> 1.25 nmol g-1 h-1) was recorded. The soil total DNA extracted from the three samples was probed by Polymerase Chain Reaction (PCR) using standard proteobacterial primers and newly designed verrucomicrobial primers, targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected at sites FAV2 and FAV3, but not at FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site (FAV2) pointed to a high diversity of gammaproteobacterial methanotrophs, distantly related to Methylocaldum-Metylococcus genera, and the presence of the newly discovered acido-thermophilic Verrucomicrobia methanotrophs. Alphaproteobacteria of the genus Methylocystis were isolated from enrichment cultures under a methane-containing atmosphere at 37 °C. The isolates grow at a pH range of 3.5 to 8 and temperatures of 18-45 °C, and consume 160 nmol of CH4 h-1 mL-1 of culture. Soils from Favara Grande showed the largest diversity of methanotrophic bacteria detected until now in a geothermal soil. While methanotrophic Verrucomicrobia are reported as dominating highly acidic geothermal sites, our results suggest that slightly acidic soils, in high-enthalpy geothermal systems, host a more diverse group of both culturable and uncultivated methanotrophs.

Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

2014-10-01

98

Structural Orientations Adjacent to Some Colorado Geothermal Systems  

SciTech Connect

Citation Information: Originator: Geothermal Development Associates, Reno, Nevada Publication Date: 2012 Title: Structural Data Edition: First Publication Information: Publication Place: Reno Nevada Publisher: Geothermal Development Associates, Reno, Nevada Description: Structural orientations (fractures, joints, faults, lineaments, bedding orientations, etc.) were collected with a standard Brunton compass during routine field examinations of geothermal phenomena in Colorado. Often multiple orientations were taken from one outcrop. Care was taken to ensure outcrops were "in place". Point data was collected with a hand-held GPS unit. The structural data is presented both as standard quadrant measurements and in format suitable for ESRI symbology Spatial Domain: Extent: Top: 4491528.924999 m Left: 207137.983196 m Right: 432462.310324 m Bottom: 4117211.772001 m Contact Information: Contact Organization: Geothermal Development Associates, Reno, Nevada Contact Person: Richard “Rick” Zehner Address: 3740 Barron Way City: Reno State: NV Postal Code: 89511 Country: USA Contact Telephone: 775-737-7806 Spatial Reference Information: Coordinate System: Universal Transverse Mercator (UTM) WGS’1984 Zone 13N False Easting: 500000.00000000 False Northing: 0.00000000 Central Meridian: -105.00000000 Scale Factor: 0.99960000 Latitude of Origin: 0.00000000 Linear Unit: Meter Datum: World Geodetic System 1984 (WGS ’1984) Prime Meridian: Greenwich Angular Unit: Degree Digital Form: Format Name: Shape file

Richard

2012-02-01

99

Modeling Studies of Geothermal Systems with a Free Water Surface  

SciTech Connect

Numerical simulators developed for geothermal reservoir engineering applications generally only consider systems which are saturated with liquid water and/or steam. However, most geothermal fields are in hydraulic communicatino with shallow ground water aquifers having free surface (water level), so that production or injection operations will cause movement of the surface, and of the air in the pore spaces above the water level. In some geothermal fields the water level is located hundreds of meters below the surface (e.g. Olkaria, Kenya; Bjornsson, 1978), so that an extensive so that an extensive unsaturated zone is present. In other the caprock may be very leaky or nonexistent [e.g., Klamath Falls, oregon (Sammel, 1976)]; Cerro Prieto, Mexico; (Grant et al., 1984) in which case ther eis good hydraulic communication between the geothermal reservoir and the shallow unconfined aquifers. Thus, there is a need to explore the effect of shallow free-surface aquifers on reservoir behavior during production or injection operations. In a free-surface aquifer the water table moves depending upon the rate of recharge or discharge. This results in a high overall storativity; typically two orders of magnitude higher than that of compressed liquid systems, but one or two orders of magnitude lower than that for liquid-steam reservoirs. As a consequence, various data analysis methods developed for compressed liquid aquifers (such as conventional well test analysis methods) are not applicable to aquifer with a free surface.

Bodvarsson, Gudmundur S.; Pruess, K.

1983-12-15

100

Life-cycle analysis results for geothermal systems in comparison to other power systems: Part II.  

SciTech Connect

A study has been conducted on the material demand and life-cycle energy and emissions performance of power-generating technologies in addition to those reported in Part I of this series. The additional technologies included concentrated solar power, integrated gasification combined cycle, and a fossil/renewable (termed hybrid) geothermal technology, more specifically, co-produced gas and electric power plants from geo-pressured gas and electric (GPGE) sites. For the latter, two cases were considered: gas and electricity export and electricity-only export. Also modeled were cement, steel and diesel fuel requirements for drilling geothermal wells as a function of well depth. The impact of the construction activities in the building of plants was also estimated. The results of this study are consistent with previously reported trends found in Part I of this series. Among all the technologies considered, fossil combustion-based power plants have the lowest material demand for their construction and composition. On the other hand, conventional fossil-based power technologies have the highest greenhouse gas (GHG) emissions, followed by the hybrid and then two of the renewable power systems, namely hydrothermal flash power and biomass-based combustion power. GHG emissions from U.S. geothermal flash plants were also discussed, estimates provided, and data needs identified. Of the GPGE scenarios modeled, the all-electric scenario had the highest GHG emissions. Similar trends were found for other combustion emissions.

Sullivan, J.L.; Clark, C.E.; Yuan, L.; Han, J.; Wang, M. (Energy Systems)

2012-02-08

101

Experimental evaluation of a non-azeotropic working fluid for geothermal heat pump system  

Microsoft Academic Search

Geothermal energy resources are found in many countries. A reasonable and efficient utilization of these resources has been a worldwide concern. The application of geothermal heat pump systems (GHPS) can help increase the efficiency of using geothermal energy and reduce the thermal pollution to the earth surface. However, this is only possible with a proper working fluid. In this paper,

L. Zhao

2004-01-01

102

COTHERM: Modelling fluid-rock interactions in Icelandic geothermal systems  

NASA Astrophysics Data System (ADS)

Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced geothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. We model the mineralogical and porosity evolution of Icelandic geothermal systems with 1D and 2D reactive transport models. These geothermal systems are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. The shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. We investigate two contrasting geothermal systems: Krafla, for which the water recharge consists of meteoritic water; and Reykjanes, for which the water recharge mainly consists of seawater. The initial rock composition is a fresh basalt. We use the GEM-Selektor geochemical modeling package [1] for calculation of kinetically controlled mineral equilibria between the rock and the ingression water. We consider basalt minerals dissolution kinetics according to Palandri & Kharaka [2]. Reactive surface areas are assumed to be geometric surface areas, and are corrected using a spherical-particle surface/mass relationship. For secondary minerals, we consider the partial equilibrium assuming that the primary mineral dissolution is slow, and the secondary mineral precipitation is fast. Comparison of our modeling results with the mineralogical assemblages observed in the field by Gudmundsson & Arnorsson [3] and by Icelandic partners of the COTHERM project suggests that the concept of partial equilibrium with instantaneous precipitation of secondary minerals is not sufficient to satisfactorily describe the experimental data. Considering kinetic controls also for secondary minerals appears as indispensable to properly describe the geothermal system evolution using a reactive transport modelling approach [4]. [1] Kulik D.A., Wagner T., Dmytrieva S.V., Kosakowski G., Hingerl F.F., Chudnenko K.V., Berner U., 2013. GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Computational Geosciences 17, 1-24. http://gems.web.psi.ch. [2] Palandri, J.L., Kharaka, Y.K., 2004. A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modelling. U.S.Geological Survey, Menlo Park, CA, pp. 1-64. [3] Gudmundsson B.T., Arnorsson S., 2005. Secondary mineral-fluid equilibria in the Krafla and Namafjall geothermal systems, Iceland. Applied Geochememistry 20, 1607-1625. [4] Kosakowski, G., & Watanabe, N., 2013. OpenGeoSys-Gem: A numerical tool for calculating geochemical and porosity changes in saturated and partially saturated media. Physics and Chemistry of the Earth, Parts A/B/C. doi:10.1016/j.pce.2013.11.008

Thien, Bruno; Kosakowski, Georg; Kulik, Dmitrii

2014-05-01

103

Numerical modeling of geothermal systems with applications to Krafla, Iceland and Olkaria, Kenya  

SciTech Connect

The use of numerical models for the evaluation of the generating potential of high temperature geothermal fields has increased rapidly in recent years. In the present paper a unified numerical approach to the modeling of geothermal systems is discussed and the results of recent modeling of the Krafla geothermal field in Iceland and the Olkaria, Kenya, are described. Emphasis is placed on describing the methodology using examples from the two geothermal fields.

Bodvarsson, G.S.

1987-08-01

104

Numerical modeling of geothermal groundwater flow in karst aquifer system in eastern Weibei, Shaanxi Province, China  

Microsoft Academic Search

The quantitative assessment of geothermal water resources is important to the exploitation and utilization of geothermal resources.\\u000a In the geothermal water systems the density of groundwater changes with the temperature, therefore the variations in hydraulic\\u000a heads and temperatures are very complicated. A three-dimensional density-dependent model coupling the groundwater flow and\\u000a heat transport is established and used to simulate the geothermal

Ming Li; GuoMin Li; Liao Yang; XueYa Dang; ChunHu Zhao; GuangCai Hou; MaoSheng Zhang

2007-01-01

105

Geothermal Resource Analysis and Structure of Basin and Range Systems, Especially Dixie Valley Geothermal Field, Nevada.  

National Technical Information Service (NTIS)

The following chapters in this report summarize the research completed over the 3 years of this DOE contract. Articles were published in the Geothermal Resources Council Bulletin, GRC Transactions, the Stanford Geothermal Reservoir Engineering Workshops, ...

D. D. Blackwell, K. W. Wisian, M. C. Richards, M. Leidig, R. Smith, J. McKenna

2003-01-01

106

One-dimensional model of vapor-dominated geothermal systems  

Microsoft Academic Search

A one-dimensional model of vapor-dominated geothermal systems in the natural state is developed in order to study the ranges of the heat and mass transport and flow resistance at which a system is capable of existing in the vapor-dominated state. The model consists of a near-surface condensate layer lying above a two-phase counterflow region with rising steam and descending water

J. M. Straus; Gerald Schubert

1981-01-01

107

I\\/S and C\\/S mixed layers, some indicators of recent physical-chemical changes in active geothermal systems: The case study of Chipilapa (El Salvador)  

Microsoft Academic Search

I\\/S and C\\/S mixed layers from the geothermal field;\\u000aof Chipilapa (El Salvador) have been studied in;\\u000adetails in order to reevaluate their potential use as;\\u000aindicator of the thermodynamic conditions in which;\\u000athey were formed. It is funded that overprinting of;\\u000aclay bearing alteration stages is common. For a given;\\u000aalteration stage, the spatial variation of I\\/S and C\\/S;

D. Beaufort; P. Papapanagiotou; P. patrier; A. M. Fouillac; H. Traineau

1996-01-01

108

Engineered Geothermal Systems Energy Return On Energy Investment  

SciTech Connect

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. Too often comparisons of energy systems use â??efficiencyâ?ť when EROI would be more appropriate. For geothermal electric power generation, EROI is determined by the electricity delivered to the consumer compared to the energy consumed to construct, operate, and decommission the facility. Critical factors in determining the EROI of Engineered Geothermal Systems (EGS) are examined in this work. These include the input energy embodied into the system. Embodied energy includes the energy contained in the materials, as well as, that consumed in each stage of manufacturing from mining the raw materials to assembling the finished system. Also critical are the system boundaries and value of the energy â?? heat is not as valuable as electrical energy. The EROI of an EGS depends upon a number of factors that are currently unknown, for example what will be typical EGS well productivity, as well as, reservoir depth, temperature, and temperature decline rate. Thus the approach developed is to consider these factors as parameters determining EROI as a function of number of wells needed. Since the energy needed to construct a geothermal well is a function of depth, results are provided as a function of well depth. Parametric determination of EGS EROI is calculated using existing information on EGS and US Department of Energy (DOE) targets and is compared to the â??minimumâ?ť EROI an energy production system should have to be an asset rather than a liability.

Mansure, A J

2012-12-10

109

Environmental impacts of open loop geothermal system on groundwater  

NASA Astrophysics Data System (ADS)

Application of renewable energies such as sunlight, wind, rain, tides, waves and geothermal heat has gradually increased to reduce emission of CO2 which is supplied from combustion of fossil fuel. The geothermal energy of various renewable energies has benefit to be used to cooling and heating systems and has good energy efficiency compared with other renewable energies. However, open loop system of geothermal heat pump system has possibility that various environmental problems are induced because the system directly uses groundwater to exchange heat. This study was performed to collect data from many documents such as papers and reports and to summarize environmental impacts for application of open loop system. The environmental impacts are classified into change of hydrogeological factors such as water temperature, redox condition, EC, change of microbial species, well contamination and depletion of groundwater. The change of hydrogeological factors can induce new geological processes such as dissolution and precipitation of some minerals. For examples, increase of water temperature can change pH and Eh. These variations can change saturation index of some minerals. Therefore, dissolution and precipitation of some minerals such as quartz and carbonate species and compounds including Fe and Mn can induce a collapse and a clogging of well. The well contamination and depletion of groundwater can reduce available groundwater resources. These environmental impacts will be different in each region because hydrogeological properties and scale, operation period and kind of the system. Therefore, appropriate responses will be considered for each environmental impact. Also, sufficient study will be conducted to reduce the environmental impacts and to improve geothermal energy efficiency during the period that a open loop system is operated. This work was supported by the Energy Efficiency and Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20123040110010).

Kwon, Koo-Sang; Park, Youngyun; Yun, Sang Woong; Lee, Jin-Yong

2013-04-01

110

GEOLOGIC SETTING OF THE CHENA HOT SPRINGS GEOTHERMAL SYSTEM, ALASKA  

Microsoft Academic Search

A belt of moderate-temperature geothermal activity runs east-west across central Alaska. Chena Hot Springs (CHS) is one of several Interior Alaskan hot springs in or near 55 Ma granites within Paleozoic metamorphic rocks. CHS is located within the CHS pluton, a composite body of quartz diorite, tonalite, granodiorite, and granite of both mid-Cretaceous and Early Tertiary ages. 40Ar\\/39Ar step heat

Amanda Kolker; Rainer Newberry; Jessica Larsen; Paul Layer; Patrick Stepp

2007-01-01

111

Natural analogs for enhanced heat recovery from geothermal systems  

SciTech Connect

High-temperature hydrothermal systems are physically and chemically zoned with depth. The energy input is from a magmatic zone, intruded by igneous bodies, that may also contribute variable amounts of magmatic fluid to the system. The heat source is directly overlain by a section of rocks, that due to their elevated temperature, respond to stress in a ductile fashion. The ductile zone is, in turn, overlain by a section of rocks that respond to stress in a brittle fashion, where water is able to circulate through fractures (the geothermal reservoir) and will be termed the hydrothermal circulation zone. Ancient and modern high-temperature geothermal systems show a predictable sequence of evolutionary events affecting these stratified zones. Metamorphic core complexes are uplifts, formed in highly extended terrains, that expose fossil brittle-ductile transition zones. Formerly ductile rocks have had brittle fractures superimposed on them, and meteoric hydrothermal systems are associated with the brittle fracturing. Porphyry copper deposits typically evolve from magmatic to meteoric hydrothermal systems. At the Larderello geothermal system, the brittle- ductile transition has been mapped using reflection seismology, and the zone has been penetrated by the San Pompeo 2 well where temperatures >420°C were encountered. Although neo-granitic dikes have been penetrated by drilling in the Larderello area, the brittle- ductile transition is largely above the inferred plutonic heat source. In the Geysers system, in contrast, the present steam system has been superimposed on young plutonic rocks and the inferred brittle-ductile transition is present at a depth of about 4.7 km within the plutonic rocks. As hydrothermal reservoirs are depleted, or surface facilities are restricted by environmental considerations, interest will turn to the deeper portions of known systems. Japan already has an aggressive program to develop Deep-seated and Magma-Ambient resources. This program, as well as others that develop methods for the mining of heat past the stage of primary production, will be termed Enhanced Heat Recovery (EHR). Examples of the evolution of natural systems suggest the methods by which deep geothermal systems can be exploited. The key to the exploitation of deep geothermal systems is successful injection of water into rocks above the brittle-ductile transition, producing steam, cooling the rocks and driving the brittle-ductile transition to deeper levels. Under this scenario, injection wells may be more expensive and require more thoughtful planning than production wells.

Nielson, Dennis L.

1996-01-24

112

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Final report, March 1, 1979-September 30, 1984  

SciTech Connect

This final report documents the Navarro College geothermal use project, which is one of nineteen direct-use geothermal projects funded principally by DOE. The six-year project encompassed a broad range of technical, institutional, and economic activities including: resource and environmental assessment; well drilling and completion; system design, construction, and monitoring; economic analysis; and public awareness programs. Some of the project conclusions are that: (1) the 130/sup 0/F Central Texas geothermal resource can support additional geothermal development; (2) private sector economic incentives currently exist which encourage commercial development of this geothermal resource; (3) potential uses for this geothermal resource include water and space heating, aquacultural and agricultural heating uses, and fruit and vegetable dehydration; (4) high maintenance costs arising from the geofluids' scaling and corrosion characteristics can be avoided through proper analysis and design.

Smith, K.

1984-09-01

113

Geothermal district heating system feasibility analysis, Thermopolis, Wyoming  

SciTech Connect

The purpose of this study is to determine the technical and economic feasibility of constructing and operating a district heating system to serve the residential, commercial, and public sectors in Thermopolis. The project geothermal resource assessment, based on reviews of existing information and data, indicated that substantial hot water resources likely exist in the Rose Dome region 10 miles northeast of Thermopolis, and with quantities capable of supporting the proposed geothermal uses. Preliminary engineering designs were developed to serve the space heating and hot water heating demands for buildings in the Thermopolis-East Thermopolis town service area. The heating district design is based on indirect geothermal heat supply and includes production wells, transmission lines, heat exchanger units, and the closed loop distribution and collection system necessary to serve the individual customers. Three options are presented for disposal of the cooled waters-reinjection, river disposal, and agricultural reuse. The preliminary engineering effort indicates the proposed system is technically feasible. The design is sized to serve 1545 residences, 190 businesses, and 24 public buildings. The peak design meets a demand of 128.2 million Btu at production rates of 6400 gpm.

Goering, S.W.; Garing, K.L.; Coury, G.; Mickley, M.C.

1982-04-26

114

High Temperature Components of Magma-Related Geothermal Systems: An Experimental and Theoretical Approach  

SciTech Connect

This summarizes select components of a multi-faceted study of high temperature magmatic fluid behavior in shallow, silicic, volcano-plutonic geothermal systems. This work built on a foundation provided by DOE-supported advances made in our lab in understanding the physics and chemistry of the addition of HCI and other chlorides into the high temperature regions of geothermal systems. The emphasis of this project was to produce a model of the bolatile contributions from felsic magmatic systems to geothermal systems

Philip A. Candela; Philip M. Piccoli

2004-03-15

115

Enthalpy transients in fractured two-phase geothermal systems  

SciTech Connect

Numerical modeling techniques are used to study the changes in flowing enthalpy of fluids produced from a well completed in a fractured two-phase geothermal reservoir. Complex interactions between different fracture and porous matrix parameters control the enthalpy transients. The results show that the flowing enthalpy is most sensitive to the characteristics of the relative permeability curves, the magnitude of the matrix permeability and the effective fracture porosity. Other parameters such as the thermal conductivity and fracture spacing also significantly affect the flowing enthalpy. In spite of the complex phenomena associated with enthalpy transients in fractured two-phase systems, it is possible to infer useful information about the producing geothermal reservoirs from field data. 15 refs., 13 figs., 2 tabs.

Lippmann, M.J.; Bodvarsson, G.S.; Gaulke, S.W.

1985-03-01

116

Natural analogs for enhanced heat recovery from geothermal systems  

SciTech Connect

High-temperature hydrothermal systems are physically and chemically zoned with depth. The energy input is from a magmatic zone, intruded by igneous bodies, that may also contribute variable amounts of magmatic fluid to the system. The heat source is directly overlain by a section of rocks, that due to their elevated temperature, respond to stress in a ductile fashion. The ductile zone is, in turn, overlain by a section of rocks that respond to stress in a brittle fashion, where water is able to circulate through fractures (the geothermal reservoir) and will be termed the hydrothermal circulation zone. Ancient and modern high-temperature geothermal systems show a predictable sequence of evolutionary events affecting these stratified zones. Metamorphic core complexes are uplifts, formed in highly extended terrains, that expose fossil brittle-ductile transition zones. Formerly ductile rocks have had brittle fractures superimposed on them, and meteoric hydrothermal systems are associated with the brittle fracturing. Porphyry copper deposits typically evolve from magmatic to meteoric hydrothermal systems. At the Larderello geothermal system, the brittle-ductile transition has been mapped using reflection seismology, and the zone has been penetrated by the San Pompeo 2 well where temperatures >420{degrees}C were encountered. Although neo-granitic dikes have been penetrated by drilling in the Larderello area, the brittle-ductile transition is largely above the inferred plutonic heat source. In the Geysers system, in contrast, the present steam system has been superimposed on young plutonic rocks and the inferred brittle-ductile transition is present at a depth of about 4.7 km within the plutonic rocks. As hydrothermal reservoirs are depleted, or surface facilities are restricted by environmental considerations, interest will turn to the deeper portions of known systems. Japan already has an aggressive program to develop Deep-Seated and Magma-Ambient resources.

Nielson, D.L. [Univ. of Utah, Salt Lake City, UT (United States)

1996-12-31

117

Off peak geothermal heat pump storage system  

SciTech Connect

The basic design of a system installed in the Columbus, Ohio Zoo is described. The distribution system is described in detail. The control system is microprocessor controlled, with about 50 monitoring points. Preliminary evaluations have indicated that the system can operate with an overall coefficient of performance in excess of 3.5. 1 figure.

Drake, M.S.

1986-03-01

118

Geothermal energy program overview  

NASA Astrophysics Data System (ADS)

The mission of the Geothermal Energy Program is to develop the science and technology necessary for tapping our nation's tremendous heat energy sources contained within the Earth. Geothermal energy is a domestic energy source that can produce clean, reliable, cost-effective heat and electricity for our nation's energy needs. Geothermal energy - the heat of the Earth - is one of our nation's most abundant energy resources. In fact, geothermal energy represents nearly 40 percent of the total U.S. energy resource base and already provides an important contribution to our nation's energy needs. Geothermal energy systems can provide clean, reliable, cost-effective energy for our nation's industries, businesses, and homes in the form of heat and electricity. The U.S. Department of Energy's (DOE) Geothermal Energy Program sponsors research aimed at developing the science and technology necessary for utilizing this resource more fully. Geothermal energy originates from the Earth's interior. The hottest fluids and rocks at accessible depths are associated with recent volcanic activity in the western states. In some places, heat comes to the surface as natural hot water or steam, which have been used since prehistoric times for cooking and bathing. Today, wells convey the heat from deep in the Earth to electric generators, factories, farms, and homes. The competitiveness of power generation with lower quality hydrothermal fluids, geopressured brines, hot dry rock, and magma (the four types of geothermal energy), still depends on the technical advancements sought by DOE's Geothermal Energy Program.

1991-12-01

119

I/S and C/S mixed layers, some indicators of recent physical-chemical changes in active geothermal systems: The case study of Chipilapa (El Salvador)  

SciTech Connect

I/S and C/S mixed layers from the geothermal field of Chipilapa (El Salvador) have been studied in details in order to reevaluate their potential use as indicator of the thermodynamic conditions in which they were formed. It is funded that overprinting of clay bearing alteration stages is common. For a given alteration stage, the spatial variation of I/S and C/S mixed layer ininerals is controlled by kinetics of mixed layer transformation and not only by temperature. Clay geo-thermometers cannot give reliable results because the present crystal-chemical states of the I/S and C/S mixed layers is not their initial state, it was aquired during the overall hydrothermal history which post dated the nucleation of smectitic clay material at high temperature. Occurrences of smectites or smectite-rich mixed layers at high temperature in reservoirs is a promising guide for reconstruct the zones in which boiling or mixing of non isotherinal fluids occurred very recently or still presently.

Beaufort, D.; Papapanagiotou, P.; patrier, P.; Fouillac, A.M.; Traineau, H.

1996-01-24

120

Energy Return On Investment of Engineered Geothermal Systems Data  

DOE Data Explorer

EROI is a ratio of the energy delivered to the consumer to the energy consumed to build, operate, and decommission the facility. EROI is important in assessing the viability of energy alternatives. Currently EROI analyses of geothermal energy are either out-of-date, of uncertain methodology, or presented online with little supporting documentation. This data set is a collection of files documenting data used to calculate the Energy Return On Investment (EROI) of Engineered Geothermal Systems (EGS) and erratum to publications prior to the final report. Final report is available from the OSTI web site (http://www.osti.gov/geothermal/). Data in this collections includes the well designs used, input parameters for GETEM, a discussion of the energy needed to haul materials to the drill site, the baseline mud program, and a summary of the energy needed to drill each of the well designs. EROI is the ratio of the energy delivered to the customer to the energy consumed to construct, operate, and decommission the facility. Whereas efficiency is the ratio of the energy delivered to the customer to the energy extracted from the reservoir.

Chip Mansure

121

Hydrocarbon anomaly in soil gas as near-surface expressions of upflows and outflows in geothermal systems  

SciTech Connect

A variety of hydrocarbons, C1 - C12, have been found in volcanic gases (fumarolic) and in geothermal waters and gases. The hydrocarbons are thought to have come from products of pyrolysis of kerogen in sedimentary rocks or they could be fed into the geothermal system by the recharging waters which may contain dissolved hydrocarbons or hydrocarbons extracted by the waters from the rocks. In the hot geothermal zone, 300°+ C, many of these hydrocarbons are in their critical state. It is thought that they move upwards due to buoyancy and flux up with the upflowing geothermal fluids in the upflow zones together with the magmatic gases. Permeability which could be provided by faults, fissures, mini and micro fractures are thought to provide pathways for the upward flux. A sensitive technique (Petrex) utilizing passive integrative adsorption of the hydrocarbons in soil gas on activated charcoal followed by desorption and analysis of the hydrocarbons by direct introduction mass spectrometry allows mapping of the anomalous areas. Surveys for geothermal resources conducted in Japan and in Indonesia show that the hydrocarbon anomaly occur over known fields and over areas strongly suspected of geothermal potential. The hydrocarbons found and identified were n-paraffins (C7-C9) and aromatics (C7-C8). Detection of permeable, i.e. active or open faults, parts of older faults which have been reactivated, e.g. by younger intersecting faults, and the area surrounding these faulted and permeable region is possible. The mechanism leading to the appearance of the hydrocarbon in the soil gas over upflow zones of the geothermal reservoir is proposed. The paraffins seems to be better pathfinders for the location of upflows than the aromatics. However the aromatics may, under certain circumstances, give better indications of the direction of the outflow of the geothermal system. It is thought that an upflow zone can be defined when conditions exist where the recharging waters containing the hydrocarbons feed into the geothermal kitchen. The existence of open and active faults, fissures, mini and micro fractures allow sufficient permeability for the gases to flux up and express themselves at the surface as hydrocarbon anomaly in the soil gas. When any of the requirements is absent, i.e. in the absence of the recharging waters, hydrocarbons, temperature, or permeability, no anomaly can be expected. It assumes a dynamic convective system, i.e. recharging waters, upflow and outflow. The anomalies however can define to a certain extent, regions of geothermal upflow, buoyant transport of gases, and frequently down-gradient of cooling waters.

Ong, H.L.; Higashihara, M.; Klusman, R.W.; Voorhees, K.J.; Pudjianto, R.; Ong, J

1996-01-24

122

Seismic ambient noise study at Bouillante geothermal system, French Antilles  

NASA Astrophysics Data System (ADS)

Seismic ambient noise analyses have been shown to be able to image structural features of the crust and to monitor underground changes of seismic wave ground velocity. We present results of cross-correlation techniques at Bouillante geothermal field, French Antilles, the largest French high-enthalpy geothermal system exploited for electrical power from 3 collocated productive wells. Two power plants generate electricity and fluid extraction rate varies with time and wells are sometimes closed for equipment maintenance. Under the support of the French Environment and Energy Management Agency (ADEME) and the French Research Agency (ANR), BRGM has been analyzing seismic data from a network comprising 5 broadband seismological stations set-up at Bouillante area since 2004. Amongst the large number of earthquakes recorded, we show that no single earthquake could be related to the fluid exploitation. Instead, they are due to the intense regional seismicity. Despite the small number of stations, surface wave travel times computed from ambient noise cross-correlation for about a year suggest that the velocity structure is consistent with the conceptual model of hot (250°C) and permeable (fractured) geothermal reservoir of Bouillante. We show at several instances that changes of the fluid extraction rate have spatial and temporal slight perturbations on medium wave velocity. For example, when the production stops for maintenance, velocity increases by several percent and with larger amplitude at stations within 1 km distance from the production wells and lower amplitudes (by more than 50 %) at stations further than 2 km from the production wells. In addition, we note that velocity perturbations have a delay of at most 1 day at further stations. We discuss several mechanisms to explain those observations like pressure and stress variations in the geothermal system. The results suggest that the inferred velocity changes, owing the fine sensibility of the inter-correlation method, do not produce stress changes strong enough to trigger micro-seismicity in the Bouillante area. The perturbation (e.g., due to phase change in the hot fluid, change in porosity and fracture closure) would propagate through the fracture system with a speed depending on its structural features. More observations using additional stations would allow us to increase our knowledge of the velocity structure around the geothermal field and understand physical mechanisms behind those controlled perturbations.

Jousset, Philippe; Bitri, Adnan; Loiseau, Justine; Bouchot, Vincent

2010-05-01

123

Layered Thermohaline Convection in Hypersaline GeothermalSystems  

SciTech Connect

Thermohaline convection occurs in hypersaline geothermal systems due to thermal and salinity effects on liquid density. Because of its importance in oceanography, thermohaline convection in viscous liquids has received more attention than thermohaline convection in porous media. The fingered and layered convection patterns observed in viscous liquid thermohaline convection have been hypothesized to occur also in porous media. However, the extension of convective dynamics from viscous liquid systems to porous media systems is complicated by the presence of the solid matrix in porous media. The solid grains cause thermal retardation, hydrodynamic dispersion, and permeability effects. We present simulations of thermohaline convection in model systems based on the Salton Sea Geothermal System, California, that serve to point out the general dynamics of porous media thermohaline convection in the diffusive regime, and the effects of porosity and permeability, in particular. We use the TOUGH2 simulator with residual formulation and fully coupled solution technique for solving the strongly coupled equations governing thermohaline convection in porous media. We incorporate a model for brine density that takes into account the effects of NaCl and CaCl2. Simulations show that in forced convection, the increased pore velocity and thermal retardation in low-porosity regions enhances brine transport relative to heat transport. In thermohaline convection, the heat and brine transport are strongly coupled and enhanced transport of brine over heat cannot occur because buoyancy caused by heat and brine together drive the flow. Random permeability heterogeneity has a limited effect if the scale of flow is much larger than the scale of permeability heterogeneity. For the system studied here, layered thermohaline convection persists for more than one million years for a variety of initial conditions. Our simulations suggest that layered thermohaline convection is possible in hypersaline geothermal systems provided the vertical permeability is smaller than the horizontal permeability, as is likely in sedimentary basins such as the Salton Trough. Layered thermohaline convection can explain many of the observations made at the Salton Sea Geothermal System over the years.

Oldenburg, Curtis M.; Pruess, Karsten

1997-01-05

124

Oblique-to-the-orogen fault systems and it causal relationship with volcanism and geothermal activity in Central Southern Chile: Insights on ENE and NW regional lineaments  

NASA Astrophysics Data System (ADS)

Major crustal faults systems at convergent margins are commonly organized into margin-parallel, high-strain domains that appear to be continuous over hundreds of kilometers. This major architecture shapes the structural grain of a given mountain belt and is thought to represent the long-term record of its deformation history. However, second-order transverse structures, cross-cutting the orogen main structural grain, also are common. In the Andes they play a key role in the tectonic, magmatic and hydrothermal history. Although the relevance of these oblique-to-the-orogen structures is widely recognized, little is known regarding their nature, kinematics and timing and also their long and short-term tectono-magmatic role. The present work address the tectono-magmatic significance of WNW and ENE-striking basement structures, through a combination of field geology and geophysics. Our working hypothesis is that WNW and ENE-striking structures correspond to long-lived fault zones that play a fundamental tectono-magmatic role in Andean evolution. They have accommodated part of the upper plate deformation arising from the ~ ENE-WNW-trending shortening and -at the same time- they have provided episodic pathways for magma and hydrothermal fluid transport in the lithosphere. Furthermore, we speculate that because WNW-striking fault zones are severely misoriented with respect to the prevailing stress field, they reactivate under supra-lithostatic fluid pressures. ENE-striking faults, in turn, are favorably oriented and do not require supra-lithostatic fluid pressures to reactivate. The problem is being tackled by selecting two outstanding case studies in the Andes of Central Chile: the ENE-oriented Tatara-San Pedro-Pellado volcanic complex - Laguna del Maule volcanic field alignment (TPMA) and the WNW-oriented Cortaderas-Chillán lineament (CChL). Observations on satellite images combined with preliminary field studies suggest that WNW-striking faults and ENE striking faults show sinistral-reverse and dextral-normal displacement respectively. Both systems crosscut each other and their activity is younger than Late Pleistocene. Furthermore, Late Pleistocene mafic dikes, vein systems and fault-controlled fumaroles appear to be synkinematic with both transverse crustal faults.

Sielfeld, G.; Cembrano, J. M.

2013-12-01

125

National Geothermal Data System: State Geological Survey Contributions to Date  

NASA Astrophysics Data System (ADS)

In collaboration with the Association of American State Geologists the Arizona Geological Survey is leading the effort to bring legacy geothermal data to the U.S. Department of Energy's National Geothermal Data System (NGDS). NGDS is a national, sustainable, distributed, interoperable network of data and service (application) providers entering its final stages of development. Once completed the geothermal industry, the public, and policy makers will have access to consistent and reliable data, which in turn, reduces the amount of staff time devoted to finding, retrieving, integrating, and verifying information. With easier access to information, the high cost and risk of geothermal power projects (especially exploration drilling) is reduced. This presentation focuses on the scientific and data integration methodology as well as State Geological Survey contributions to date. The NGDS is built using the U.S. Geoscience Information Network (USGIN) data integration framework to promote interoperability across the Earth sciences community and with other emerging data integration and networking efforts. Core to the USGIN concept is that of data provenance; by allowing data providers to maintain and house their data. After concluding the second year of the project, we have nearly 800 datasets representing over 2 million data points from the state geological surveys. A new AASG specific search catalog based on popular internet search formats enables end users to more easily find and identify geothermal resources in a specific region. Sixteen states, including a consortium of Great Basin states, have initiated new field data collection for submission to the NGDS. The new field data includes data from at least 21 newly drilled thermal gradient holes in previously unexplored areas. Most of the datasets provided to the NGDS are being portrayed as Open Geospatial Consortium (OGC) Web Map Services (WMS) and Web Feature Services (WFS), meaning that the data is compatible with a variety of visualization software. Web services are ideal for the NGDS data for a number of reasons including that they preserve data ownership in that they are read only and new services can be deployed to meet new requirements without modifying existing applications.

Patten, K.; Allison, M. L.; Richard, S. M.; Clark, R.; Love, D.; Coleman, C.; Caudill, C.; Matti, J.; Musil, L.; Day, J.; Chen, G.

2012-12-01

126

Induced seismicity at the Paralana Enhanced Geothermal System, South Australia  

NASA Astrophysics Data System (ADS)

Induced seismicity is generally associated with geothermal exploitations through different mechanisms like pore-pressure increase, temperature or chemical changes. The locations and source parameters of microearthquakes are increasingly used as a tool to monitor the response of the reservoir subjected to fluid stimulations. However, our understanding of the relationship between induced seismicity and exploration parameters remains limited, notably because it depends on local and regional geological conditions (stress field, rocks properties, extent of fault and fractures …). In order to make correct interpretation, precise characterization of the geothermal site is then essential. For example, a wrong velocity model will lead to an erroneous earthquake location, particularly in the absence of calibration shots. Similarly, many converted phases could be generated within a complex media, increasing the difficulty to pick phases correctly. We present here our results on the characterization of a geothermal site, Paralana, in South Australia using complementary passive and active seismic methods. The project aims to exploit natural heating from a radiogenic basement. A ~4000 m deep well was stimulated during 5 days in July 2011. More than 7000 microearthquakes were induced and recorded by a network composed of 20 stations (boreholes and surface stations). Automatic methods allowed us to process consistently the large amount of data. A minimum of 25 events per hour were detected from the beginning of the injection, increasing almost conjunctly with flow rate. The maximum seismicity rate reached 100 events per hour, the last day of injection. Active seismic methods were applied to build a 3D velocity model and used to improve the earthquake locations that finally cluster at the bottom of the well. Furthermore, to define the origin of an unknown phase, 3D ray-tracing modeling was systematically applied to test different scenarios. Actual results show that in term of arrival time, these phases most likely correspond to S-to-P converted waves on some interfaces at depth.

Albaric, J.; Langet, N.; Hasting, M.; Oye, V.; Lecomte, I.; Messeiller, M.; Iranpour, K.; Reid, P.; Llanos, E. M.

2012-04-01

127

Assessing the role of ancient and active geothermal systems in oil-reservoir evolution in the eastern Basin and Range province, western USA. Annual progress report, June 1, 1992--May 31, 1993  

SciTech Connect

Results of our research on the oil fields of the Basin and Range province of the western USA continue to support the following concept: Convecting, moderate-temperature geothermal systems in this region have fostered and in some cases critically influenced the generation, migration, and entrapment of oil. At one Basin-Range field (Grant Canyon), oil-bearing and aqueous fluid inclusions in late-stage hydrothermal quartz were entrapped at temperatures comparable to those now prevailing at reservoir depths (120--130{degrees}C); apparent salinities of the aqueous varieties match closely the actual salinity of the modern, dilute oil-field waters. The inclusion-bearing quartz has the oxygen-isotopic signature for precipitation of the mineral at contemporary temperatures from modern reservoir waters. Measured and fluid-inclusion temperatures define near-coincident isothermal profiles through the oil-reservoir interval, a phenomenon suggesting ongoing heat and mass transfer. These findings are consistent with a model whereby a still-active, convectively circulating, meteoric-hydrothermal system: (1) enhanced porosity in the reservoir rock through dissolution of carbonate; (2) hydrothermally sealed reservoir margins; (3) transported oil to the reservoirs from a deep source of unknown size and configuration; and (4) possibly accelerated source-rock maturation through an increase in the local thermal budget. Grant Canyon and other Basin-Range oil fields are similar to the oil-bearing, Carlin-type, sediment-hosted, disseminated gold deposits of the nearby Alligator Ridge district. The oil fields could represent either weakly mineralized analogues of these deposits, or perhaps an incipient phase in their evolution.

Hulen, J.B.

1993-07-01

128

Long-term predictions of minewater geothermal systems heat resources  

NASA Astrophysics Data System (ADS)

Abandoned underground mines usually flood due to the natural rise of the water table. In most cases the process is relatively slow giving the mine water time to equilibrate thermally with the the surrounding rock massif. Typical mine water temperature is too low to be used for direct heating, but is well suited to be combined with heat pumps. For example, heat extracted from the mine can be used during winter for space heating, while the process could be reversed during summer to provide space cooling. Altough not yet widely spread, the use of low temperature geothermal energy from abandoned mines has already been implemented in the Netherlands, Spain, USA, Germany and the UK. Reliable reservoir modelling is crucial to predict how geothermal minewater systems will react to predefined exploitation schemes and to define the energy potential and development strategy of a large-scale geothermal - cold/heat storage mine water systems. However, most numerical reservoir modelling software are developed for typical environments, such as porous media (a.o. many codes developed for petroleum reservoirs or groundwater formations) and cannot be applied to mine systems. Indeed, mines are atypical environments that encompass different types of flow, namely porous media flow, fracture flow and open pipe flow usually described with different modelling codes. Ideally, 3D models accounting for the subsurface geometry, geology, hydrogeology, thermal aspects and flooding history of the mine as well as long-term effects of heat extraction should be used. A new modelling approach is proposed here to predict the long-term behaviour of Minewater geothermal systems in a reactive and reliable manner. The simulation method integrates concepts for heat and mass transport through various media (e.g., back-filled areas, fractured rock, fault zones). As a base, the standard software EPANET2 (Rossman 1999; 2000) was used. Additional equations for describing heat flow through the mine (both through open pipes and from the rock massif) have been implemented. Among others, parametric methods are used to bypass some shortcomings in the physical models used for the subsurface. The advantage is that the complete geometry of the mine workings can be integrated and that computing is fast enough to allow implementing and testing several scenarios (e.g. contributions from fault zones, different assumptions about the actual status of shafts, drifts and mined out areas) in an efficient way (Ferket et al., 2011). EPANET allows to incorporate the full complexity of the subsurface mine structure. As a result, the flooded mine is considered as a network of pipes, each with a custom-defined diameter, length and roughness.

Harcout-Menou, Virginie; de ridder, fjo; laenen, ben; ferket, helga

2014-05-01

129

The geothermal fields of the Kenya rift  

NASA Astrophysics Data System (ADS)

From the standpoint of geothermal energy, Kenya's resources are due to the presence of the Kenya rift which is part of the East African rift system. Geological, geophysical and geothermal studies indicate that Neogene volcanic activity has led to the presence of near surface heat generating sources. Geothermal fields of the Kenya rift occur in two types of environments. The main geothermal fields are associated with Quaternary volcanoes. The second type is associated with fissures that are related to active fault zones. In either case, these fields are dissected by numerous rift faults that give rise to a number of geothermal springs and fumaroles.

Riaroh, Don; Okoth, William

1994-09-01

130

Parametric Analysis of the Factors Controlling the Costs of Sedimentary Geothermal Systems - Preliminary Results (Poster)  

SciTech Connect

Parametric analysis of the factors controlling the costs of sedimentary geothermal systems was carried out using a modified version of the Geothermal Electricity Technology Evaluation Model (GETEM). The sedimentary system modeled assumed production from and injection into a single sedimentary formation.

Augustine, C.

2013-10-01

131

Dynamics of hydrothermal seeps from the Salton Sea geothermal system (California, USA) constrained by temperature monitoring  

E-print Network

Dynamics of hydrothermal seeps from the Salton Sea geothermal system (California, USA) constrained-, and petroleum-bearing seeps are part of the Salton Sea geothermal system (SSGS) in southern California. Carbon. Polteau, S. Planke, and Y. Y. Podladchikov (2009), Dynamics of hydrothermal seeps from the Salton Sea

Svensen, Henrik

132

Marketing the Klamath Falls Geothermal District Heating system  

SciTech Connect

The Klamath Falls Geothermal District Heating system was completed in 1981 and, until 1992, there was no formal marketing plan for the system. This lack of marketing and the system history of poor availability combined to reduce or eliminate interest in connecting on the part of local building owners and it served only the original 14 government buildings connected at start up. The revenue from these buildings, however, did not cover the entire cost of operating the system. As a result, the city was faced with a difficult decision - develop the revenue required to make the system self-supporting or shut it down. As a result, a marketing strategy for the system was developed. A flat rate was developed in which the rate is negotiable, but for most customers approximates 50% of the gas bill. In addition, the flat rate reduced customer retrofit costs because it is not necessary to buy a meter. Finally, the flat rate is a guaranteed value for the first 10 years of the contract. To reduce retrofit costs, the new marketing plan eliminates the requirement for a customer heat exchanger. New customers are now connected directly into the distribution system with district loop water used as the building heating medium. The state operates two programs which have been used in the marketing plan. The first of these is available only to taxable entities and is referred to as the Business Energy Tax Credit (BETC). This program offers business a 35% tax credit on the costs associated with connection to the geothermal district heat system (retrofit, design, permits, etc.). The second state program is the Small Energy Loan Program (SELP). This program will loan the entire cost of the energy project to the customer. The new marketing strategy for the Klamath Falls system has concentrated on offering the customer an attractive and easy to understand rate structure, reduced retrofit cost and complexity for this building along with an attractive package of financing and tax credits. 1 tab.

Rafferty, K. (Geo-Heat Center, Klamath Falls, OR (United States))

1993-08-01

133

Proceedings of a Topical Meeting On Small Scale Geothermal Power Plants and Geothermal Power Plant Projects  

SciTech Connect

These proceedings describe the workshop of the Topical Meeting on Small Scale Geothermal Power Plants and Geothermal Power Plant Projects. The projects covered include binary power plants, rotary separator, screw expander power plants, modular wellhead power plants, inflow turbines, and the EPRI hybrid power system. Active projects versus geothermal power projects were described. In addition, a simple approach to estimating effects of fluid deliverability on geothermal power cost is described starting on page 119. (DJE-2005)

None

1986-02-12

134

A geochemical reconnaissance of the Alid volcanic center and geothermal system, Danakil depression, Eritrea  

USGS Publications Warehouse

Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of ~10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of approx. 10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.

Lowenstern, J. B.; Janik, C. J.; Fournier, R. O.; Tesfai, T.; Duffield, W. A.; Clynne, M. A.; Smith, J. G.; Woldegiorgis, L.; Weldemariam, K.; Kahsai, G.

1999-01-01

135

Development of geothermal logging systems in the United States  

SciTech Connect

Logging technologies developed for hydrocarbon resource evaluation have not migrated into geothermal applications even though data so obtained would strengthen reservoir characterization efforts. Two causative issues have impeded progress: (1) there is a general lack of vetted, high-temperature instrumentation, and (2) the interpretation of log data generated in a geothermal formation is in its infancy. Memory-logging tools provide a path around the first obstacle by providing quality data at a low cost. These tools feature on-board computers that process and store data, and newer systems may be programmed to make decisions. Since memory tools are completely self-contained, they are readily deployed using the slick line found on most drilling locations. They have proven to be rugged, and a minimum training program is required for operator personnel. Present tools measure properties such as temperature and pressure, and the development of noise, deviation, and fluid conductivity logs based on existing hardware is relatively easy. A more complex geochemical tool aimed at a quantitative analysis of (potassium, uranium and thorium) is in the calibration phase, and it is expandable into all nuclear measurements common in the hydrocarbon industry. A fluid sampling tool is in the design phase. All tools are designed for operation at conditions exceeding 400 C, and for deployment in the slim holes produced by mining-coring operations. Partnerships are being formed between the geothermal industry and scientific drilling programs to define and develop inversion algorithms relating raw tool data to more pertinent information. These cooperative efforts depend upon quality guidelines such as those under development within the international Ocean Drilling Program.

Lysne, P.

1994-04-01

136

Sperry Low Temperature Geothermal Conversion System, Phase 1 and Phase 2. Volume 3: Systems description  

NASA Astrophysics Data System (ADS)

The major fraction of hydrothermal resources with the prospect of economic usefulness for the generation of electricity are in the 300(0)F to 425(0)F temperature range. Cost effective conversion of the geothermal energy to electricity requires new ideas to improve conversion efficiency, enhance brine flow, reduce plant costs, increase plant availability, and shorten the time between investment and return. The problems addressed are those inherent in the geothermal environment, in the binary fluid cycle, in the difficulty of efficiently converting the energy of a low temperature resource, and in geothermal economics some of these problems are explained. The energy expended by the down hole pump; the difficulty in designing reliable down hole equipment; fouling of heat exchanger surfaces by geothermal fluids; the unavailability of condenser cooling water at most geothermal sites; the large portion of the available energy used by the feed pump in a binary system; the pinch effect, a loss in available energy in transferring heat from water to an organic fluid; flow losses in fluids that carry only a small amount of useful energy to begin with; high heat exchanger costs, the lower the temperature interval of the cycle, the higher the heat exchanger costs in $/kW; the complexity and cost of the many auxiliary elements of proposed geothermal plants; and the unfortunate cash flow vs. investment curve caused by the many years of investment required to bring a field into production before any income is realized.

Matthews, H. B.

137

Alteration mineralogy of the Dixie Valley geothermal system, Nevada  

SciTech Connect

Petrographic studies along the Stillwater fault zone in Dixie Valley, Nevada document a variety of overlapping alteration assemblages that represent different physical and chemical conditions. At depth in the northern portion of the Dixie Valley geothermal field, wairakite, illite-smectite, and chalcedonic quartz are present in the hanging wall where measured, static and flowing temperatures are close to 248{degrees}C. Although the presence of wairakite is consistent with the observed temperatures, both the illite-smectite and chalcedonic quartz suggest lower temperature conditions. In outcrop, samples from the footwall of the Stillwater fault contain quartz, kaolin, smectite, dolomite, biotite, and epidote. Crosscutting relationships indicate that quartz and kaolin postdate formation of older biotite and epidote veins. The superposition of lower temperature assemblages (kaolin, dolomite, smectite) upon higher temperature minerals (biotite, epidote) characterizes the alteration in the footwall, whereas, the superposition of higher temperature minerals (wairakite) upon lower temperature phases (chalcedonic quartz, illite-smectite) is characteristic of the alteration in the geothermal reservoir within the hanging wall. This retrograde and prograde progression of alteration should be expected along this active normal fault as the footwall is uplifted and exhumed through time, and simultaneously, the hanging wall is down dropped.

Lutz, S.J.; Moore, J.N.; Benoit, D.

1996-12-31

138

Modeling studies of geothermal systems with a free water surface  

SciTech Connect

A numerical simulator was developed for the modeling of air-steam-water systems. The simulator was applied to various problems involving injection into or production from a geothermal reservoir in hydraulic communication with a shallow free-surface aquifer. First, a one-dimensional column problem is considered and the water level movement during exploitation is studied using different capillary pressure functions. Second, a two-dimensional radial model is used to study and compare reservoir depletion for cases with and without a free-surface aquifer. Finally, the contamination of a shallow free-surface aquifer due to cold water injection is investigated. The primary aim of these studies is to obtain an understanding of the response of a reservoir in hydraulic communication with a unconfined aquifer during exploitation or injection and to determine under which circumstances conventional modeling techniques (fully saturated systems) can be applied to such systems.

Bodvarsson, G.S.; Pruess, K.

1983-12-01

139

Laboratory testing and modeling to evaluate perfluorocarbon compounds as tracers in geothermal systems  

SciTech Connect

The thermal stability and adsorption characteristics of three perfluorinated hydrocarbon compounds were evaluated under geothermal conditions to determine the potential to use these compounds as conservative or thermally-degrading tracers in Engineered (or Enhanced) Geothermal Systems (EGS). The three compounds tested were perfluorodimethyl-cyclobutane (PDCB), perfluoromethylcyclohexane (PMCH), and perfluorotrimethylcyclohexane (PTCH), which are collectively referred to as perfluorinated tracers, or PFTs. Two sets of duplicate tests were conducted in batch mode in gold-bag reactors, with one pair of reactors charged with a synthetic geothermal brine containing the PFTs and a second pair was charged with the brine-PFT mixture plus a mineral assemblage chosen to be representative of activated fractures in an EGS reservoir. A fifth reactor was charged with deionized water containing the three PFTs. The experiments were conducted at {approx}100 bar, with temperatures ranging from 230 C to 300 C. Semi-analytical and numerical modeling was also conducted to show how the PFTs could be used in conjunction with other tracers to interrogate surface area to volume ratios and temperature profiles in EGS reservoirs. Both single-well and cross-hole tracer tests are simulated to illustrate how different suites of tracers could be used to accomplish these objectives. The single-well tests are especially attractive for EGS applications because they allow the effectiveness of a stimulation to be evaluated without drilling a second well.

Reimus, Paul W [Los Alamos National Laboratory

2011-01-21

140

Geobotanical characterization of a geothermal system using hyperspectral imagery: Long Valley Caldera, CA  

SciTech Connect

We have analyzed hyperspectral Airborne Visible-Infrared Imaging System (AVIRIS) imagery taken in September of 1992 in Long Valley Caldera, CA, a geothermally active region expressed surficially by hot springs and fumaroles. Geological and vegetation mapping are attempted through spectral classification of imagery. Particular hot spring areas in the caldera are targeted for analysis. The data is analyzed for unique geobotanical patterns in the vicinity of hot springs as well as gross identification of dominant plant and mineral species. Spectra used for the classifications come from a vegetation spectral library created for plant species found to be associated with geothermal processes. This library takes into account the seasonality of vegetation by including spectra for species on a monthly basis. Geological spectra are taken from JPL and USGS mineral libraries. Preliminary classifications of hot spring areas indicate some success in mineral identification and less successful vegetation species identification. The small spatial extent of individual plants demands either sub-pixel analysis or increased spatial resolution of imagery. Future work will also include preliminary analysis of a hyperspectral thermal imagery dataset and a multitemporal air photo dataset. The combination of these remotely sensed datasets for Long Valley will yield a valuable product for geothermal exploration efforts in other regions.

Carter, M R; Cochran, S A; Martini, B A; Pickles, W L; Potts, D C; Priest, R E; Silver, E A; Wayne, B A; White, W T

1998-12-01

141

Application of the computer code TOUGH2 to the simulation of supercritical conditions in geothermal systems  

Microsoft Academic Search

At the high pressures and temperatures found in deep geothermal systems, supercritical conditions can occur. Current numerical geothermal simulators are either not capable of modelling these conditions, or can do so only at significantly reduced computation speed. This paper describes modifications to the TOUGH2 simulator to extend its applicability. It employs the updated IAPWS-97 thermodynamic formulation, and uses density and

Adrian E. Croucher; Michael J. O’Sullivan

2008-01-01

142

Lithium isotopes in island arc geothermal systems: Guadeloupe, Martinique (French West Indies) and experimental approach  

E-print Network

Lithium isotopes in island arc geothermal systems: Guadeloupe, Martinique (French West Indies and the Diamant areas). The lithium isotopic signatures of the geothermal fluids collected from deep reservoirs during formation of Li- bearing secondary minerals by the uptake of lithium into the alteration minerals

Boyer, Edmond

143

Comparing FRACHEM and SHEMAT for the modelling of brine-rock interactions in Enhanced Geothermal Systems  

Microsoft Academic Search

Coupled numerical simulations of heat transfer, fluid flow and chemical reactions in geothermal systems are complex because of the highly heterogeneous geology, high temperatures, elevated pressures and often high salinity of the formation fluids. Codes such as FRACHEM and SHEMAT have been developed to forecast the long-term evolution of exploited geothermal reservoirs in order to determine how fluid circulation within

Portier Sandrine; Kühn Michael; Vuataz François-David

144

The application of unmanned aerial systems (UAS) in geophysical investigations of geothermal systems  

NASA Astrophysics Data System (ADS)

Investigations of geothermal systems typically involve ground-based geological and geophysical studies in order to map structures that control and facilitate fluid flow. The spatial extent of ground-based investigations can be limited, however, by surficial hot springs, dense foliage, and roadless or private lands. This can result in data gaps in key areas, particularly around active hydrothermal springs. Manned aircraft can provide access to these areas and can yield broad and uniform data coverage, but high-resolution surveys are costly and relatively inflexible to changes in the survey specifications that may arise as data are collected. Unmanned aerial systems (UAS) are well suited for conducting these surveys, but until recently, various factors (scientific instrumentation requirements, platform limitations, and size of the survey area) have required the use of large UAS platforms, rendering unmanned aerial surveys unsuitable for most investigations. We have developed and tested a new cesium magnetometer system to collect magnetic data using two different small-platform UAS that overcomes many of the challenges described above. We are deploying this new system in Surprise Valley, CA, to study the area's active geothermal field. Surprise Valley is ideally suited to testing UAS due to its low population density, accessible airspace, and broad playa that provides ample opportunity to safely land the aircraft. In combination with gravity and topographic data, magnetic data are particularly useful for identifying buried, intra-basin structures, especially in areas such as Surprise Valley where highly magnetic, dense mafic volcanic rocks are interbedded with and faulted against less magnetic, less dense sedimentary rock. While high-resolution gravity data must be collected at point locations on the ground, high-resolution magnetic data can be obtained by UAS that provide continuous coverage. Once acquired, the magnetic data obtained by the UAS will be combined with high-resolution airborne lidar data in order to correlate subsurface structures with subtle surface features, to identify possible conduits for, or barriers to, geothermal fluid circulation. Our September 2012 mission will deploy NASA's SIERRA UAS platform to perform a reconnaissance survey of the entire valley. Results from ground and flight tests indicate that magnetic "noise" from the SIERRA platform is low, and can be effectively compensated to provide data comparable with high-resolution commercial methods. A second mission will be flown in summer 2013 using the SWIFT platform, which will analyze data from its onboard sensors to continuously optimize its flight path in real-time to autonomously investigate regions of interest such as steep magnetic gradients or abrupt changes in anomaly amplitudes and wavelengths. The SWIFT also has the advantage that it can be flown as a glider, further reducing magnetic noise of the platform arising from the engine. This innovative use of UAS and intelligent automation in geophysical investigations offers the ability to obtain higher-resolution and more comprehensive and targeted data at a lower cost than is presently possible, expanding our ability to explore a wide variety of geothermal systems.

Glen, J. M.; Egger, A. E.; Ippolito, C.; Phelps, G. A.; Berthold, R.; Lee, R.; Spritzer, J. M.; Tchernychev, M.

2012-12-01

145

Phase relations and adiabats in boiling seafloor geothermal systems  

USGS Publications Warehouse

Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

Bischoff, J. L.; Pitzer, K. S.

1985-01-01

146

Geochemical exploration of a promissory Enhanced Geothermal System (EGS): the Acoculco caldera, Mexico.  

NASA Astrophysics Data System (ADS)

The Acoculco caldera (Puebla, Mexico) has been identified by the Mexican Federal Electricity Company (in Spanish 'Comisión Federal de Electricidad', CFE) as a potential Enhanced Geothermal System (EGS) candidate. Two exploration wells were drilled and promising temperatures of ~300° C have been measured at a depth of 2000 m with a geothermal gradient of 11oC/100m, which is three times higher than the baseline gradient measured within the Trans-Mexican Volcanic Belt. As usually observed in Hot Dry Rock systems, thermal manifestations in surface are scarce and consist in low-temperature bubbling springs and soil degassing. The goals of this study were to identify the origin of these fluids, to estimate the soil degassing rate and to explore new areas for a future detailed exploration and drilling activities. Water and gas samples were collected for chemical and isotopic analysis (?18O, ?D, 3He/4He, 13C, 15N) and a multi-gas (CO2, CH4, H2S) soil survey was carried out using the accumulation chamber method. Springs' compositions indicate a meteoric origin and the dissolution of CO2 and H2S-rich gases, while gas compositions reveal a MORB-type origin mixed with some arc-type contribution. Gas geothermometry results are similar to temperatures measured during well drilling (260° C-300° C). Amongst all measured CO2 fluxes, only 5% (mean: 5543 g m-2 day-1) show typical geothermal values, while the remaining fluxes are low and correspond to biogenic degassing (mean: 18 g m-2 day-1). The low degassing rate of the geothermal system is a consequence of the intense hydrothermal alteration observed in the upper 800 m of the system which acts as an impermeable caprock. Highest measured CO2 fluxes (above > 600 g m-2 day-1) have corresponding CH4/CO2 flux ratios similar to mass ratios of sampled gases, which suggest an advective fluid transport. To represent field conditions, a numerical model was also applied to simulate the migration of CO2 towards the surface through a shallow aquifer under fully saturated conditions. By changing some of the aquifer properties (i.e., depth, permeability and porosity), it was found how geothermal CO2 fluxes can show values similar to a biogenic background flux. Future field work at Acoculco will include ?13C analysis together with soil flux measurements for a better discrimination of the degassing origin, and a thinner flux measurement grid will be defined for a better detection of any possible gas flux anomaly.

Peiffer, Loic; Romero, Ruben Bernard; Pérez-Zarate, Daniel; Guevara, Mirna; Santoyo Gutiérrez, Edgar

2014-05-01

147

Post-orogenetic magmatic activity and related geothermal resources in Southern Tuscany, Italy  

SciTech Connect

A wide area of central Italy, located along the Tyrrhenian coast, is characterized by recent magmatic activity, regional uplifting and abundant thermal manifestations. The area, which includes southern Tuscan and parts of northern Latium, is bounded to the north by the Arno River valley, to the east by the Chiana valley and Lake Trasimeno, to the south by the Tiber valley and to the west by the important normal fault system controlling the Tyrrhenian coast. The area is also well-known for the frequent occurrences of young mineral deposits and the presence of abundant high enthalpy geothermal resources: the dry-seam fields of Larderello and Mt. Amiata, among the largest in the world, with a present electric installed capacity of 459 MW (1984). The understanding of the origin of these phenomena and of the processes which led to the formation of the natural resource characterizing the area (geothermal, mineral etc.), might represent a valuable exploration tool and lead to a further expansion of present exploitation.

Merla, A.

1986-01-01

148

Locating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data  

SciTech Connect

Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is {approx} 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/s, which is sandwiched between two half spaces with relatively higher velocities (P wave velocity 5.60 km/s, and S wave velocity 3.20 km/s). zones having vertical or nearly vertical dipping fault planes.

SGP-TR-150-16

1995-01-26

149

Active Management of Integrated Geothermal-CO2 Storage Reservoirs in Sedimentary Formations  

SciTech Connect

Active Management of Integrated Geothermal–CO2 Storage Reservoirs in Sedimentary Formations: An Approach to Improve Energy Recovery and Mitigate Risk: FY1 Final Report The purpose of phase 1 is to determine the feasibility of integrating geologic CO2 storage (GCS) with geothermal energy production. Phase 1 includes reservoir analyses to determine injector/producer well schemes that balance the generation of economically useful flow rates at the producers with the need to manage reservoir overpressure to reduce the risks associated with overpressure, such as induced seismicity and CO2 leakage to overlying aquifers. Based on a range of well schemes, techno-economic analyses of the levelized cost of electricity (LCOE) are conducted to determine the economic benefits of integrating GCS with geothermal energy production. In addition to considering CO2 injection, reservoir analyses are conducted for nitrogen (N2) injection to investigate the potential benefits of incorporating N2 injection with integrated geothermal-GCS, as well as the use of N2 injection as a potential pressure-support and working-fluid option. Phase 1 includes preliminary environmental risk assessments of integrated geothermal-GCS, with the focus on managing reservoir overpressure. Phase 1 also includes an economic survey of pipeline costs, which will be applied in Phase 2 to the analysis of CO2 conveyance costs for techno-economics analyses of integrated geothermal-GCS reservoir sites. Phase 1 also includes a geospatial GIS survey of potential integrated geothermal-GCS reservoir sites, which will be used in Phase 2 to conduct sweet-spot analyses that determine where promising geothermal resources are co-located in sedimentary settings conducive to safe CO2 storage, as well as being in adequate proximity to large stationary CO2 sources.

Thomas A. Buscheck

2012-01-01

150

Characterization of hot dry rock geothermal energy extraction systems  

NASA Astrophysics Data System (ADS)

The engineering of heat exchange systems by which geothermal heat can be efficiently extracted from hot impermeable rocks is studied. The system currently under investigation at Fenton Hill, New Mexico consists of a network of large fractures created through the hydraulic pressurization of a well penetrating hot basement rocks and subsequently intersected by a second well drilled to form a flow-thru system. Cool water pumped into the fractures through one well, once heated in the reservoir, returns to the surface through the second well, is cooled, and then recirculated. While much is known about the performance parameters of the fracture network from short-term flow tests, little is understood concerning the spatial dimensions and geometrical relationship of individual fractures comprising the network. Ultimately, the success one has in estimating the long-term performance of such a system where commercialization is an issue, and in engineering future systems with optimal performance, depends on the success in characterizing the flow-thru fracture networks.

Albright, J. N.; Newton, C. A.

1981-04-01

151

Importance of Hydrogeological Conditions on Open-loop Geothermal System  

NASA Astrophysics Data System (ADS)

The open-loop geothermal system has been known as an eco-friendly, energy-saving, and cost-efficient alternative for the cooling and heating of buildings with directly using the relatively stable temperature of groundwater. Thus, hydrogeological properties of aquifer, such as hydraulic conductivity and storage, must be important in the system application. The study site is located near Han-river, Korea, and because of the well-developed alluvium it might be a typical site appropriate to this system requiring an amount of groundwater. In this study, the first objective of numerical experiments was to find the best distributions of pumping and injection wells suitable to the hydrogeological conditions of the site for the efficient and sustainable system operation. The aquifer has a gravel layer at 15m depth below the ground surface and the river and the agricultural field, which may be a potential contaminant source, are located at the west and east sides, respectively. Under the general conditions that the regional groundwater flows from the east to the river, the locally reversed well distribution, locating the pumping well at upgradient and the injection well at downgradient of the regional flow, was most sustainable. The gravel layer with high hydraulic conductivity caused a little drawdown despite of an amount of pumping and allowed to stably reinject the used groundwater in all the cases, but it provided a passage transferring the injected heat to the pumping well quickly, particularly in the cases locating the injection well at the upgradient. This thermal interference was more severe in the cases of the short distance between the wells. The high conductive layer is also a reason that the seasonal role conversion of wells for the aquifer thermal energy storage was ineffective in this site. Furthermore, the well distribution vertical to the regional groundwater flow was stable, but not best, and, thus, it may be a good choice in the conditions that the regional groundwater flow direction has often been changed. Any effects of the seasonal river temperature variation and contaminant sources were not found on the wells because of the well screen installed at only the relatively deep gravel layer. Finally, it was evaluated whether if these results are valid in a homogeneous aquifer with the full screen of wells and the aquifer having a sediment layer with high hydraulic conductivity at a shallow depth, which are also typical aquifers near river. All the results concluded that it is essential to investigate and understand the site-specific hydrogeological conditions for the successful application of open-loop geothermal system.

Park, D.; Bae, G.; Kim, S.; Lee, K.

2013-12-01

152

Geothermal System at 21{degrees}N, East Pacific Rise: Physical Limits on Geothermal Fluid and Role of Adiabatic Expansion.  

PubMed

Pressure-volume-temperature relations for water at the depth of the magma chamber at 21 degrees N on the East Pacific Rise suggest that the maximum subsurface temperature of the geothermal fluid is about 420 degrees C. Both the chemistry of the discharging fluid and thermal balance considerations indicate that the effective water/rock ratios in the geothermal system are between 7 and 16. Such low ratios preclude effective metal transport at temperatures below 350 degrees C, but metal solubilization at 400 degrees C and above is effective even at such low ratios. It is proposed that the 420 degrees C fluid ascends essentially adiabatically and in the process expands, cools, and precipitates metal sulfides within the upper few hundred meters of the sea floor and on the sea floor itself. PMID:17779617

Bischoff, J L

1980-03-28

153

GEOGRAPHIC INFORMATION SYSTEMS IN MANAGING OF TERRITORIAL RESOURCES: AN EXAMPLE FOR THE SABATINI GEOTHERMAL SYSTEM (CENTRAL ITALY)  

Microsoft Academic Search

Geographic Information System (GIS) is very important tool in managing the interdisciplinary researches and territorial resources. GIS integrates data for capturing, managing, analyzing, and displaying all forms of geographically referenced information. They can represent a scientific and social benefit. Here we present an application of GIS to a potentially exploitable geothermal area. The geothermal resource can be used either indirectly

M. Procesi; D. Cinti; P. Poncia; D. de Rita

2009-01-01

154

Design and Development of Geothermal Cooling System for Composite Climatic Zone in India  

NASA Astrophysics Data System (ADS)

The tropical climate buildings use about 70 % of operating energy for cooling of built environment. In composite climatic zone like Nagpur, Maharashtra, India several electro-mechanical cooling appliances viz., evaporative coolers, air conditioners, etc. are used. Application of geothermal cooling system is a very apt option for saving energy and reducing emission when compared to conventional cooling techniques. In the present work design methodology of geothermal cooling system is broadly elaborated and is applied to a case study of an educational building located in composite climate. The application of conventional and geothermal cooling systems is compared in terms of energy consumption. It is found that geothermal cooling system saves around 90 % of electricity as compared to air conditioner and 100 % of water as compared to evaporative coolers. This approach can further be extended for larger applications that will reduce consumption of energy and water in buildings.

Ralegaonkar, R.; Kamath, M. V.; Dakwale, V. A.

2014-08-01

155

Hydrothermal spallation drilling and advanced energy conversion technologies for Engineered Geothermal Systems  

E-print Network

The purpose of this research was to study the various factors affecting the economic and technical feasibility of Engineered Geothermal Systems, with a special emphasis on advanced drilling technologies. The first part of ...

Augustine, Chad R

2009-01-01

156

On the production behavior of enhanced geothermal systems with CO2 as working fluid  

E-print Network

Simulation of mineral precipitation and dissolution in the 5-km deep enhanced geothermalgeothermal systems (EGS), heat transmission, thermal breakthrough, CO 2 storage, numerical simulation.simulation of injectivity effects of mineral scaling and clay swelling in a fractured geothermal

Pruess, K.

2008-01-01

157

Design, fabrication, delivery, operation and maintenance of a geothermal power conversion system  

NASA Technical Reports Server (NTRS)

The design, fabrication, delivery, operation and maintenance of an Hydrothermal Power Company 1250 KVA geothermal power conversion system using a helical screw expander as the prime mover is described. Hydrostatic and acceptance testing are discussed.

1980-01-01

158

Method for inhibiting silica precipitation and scaling in geothermal flow systems  

DOEpatents

A method for inhibiting silica scaling and precipitation in geothermal flow systems by on-line injection of low concentrations of cationic nitrogen-containing compounds, particularly polymeric imines, polymeric amines, and quaternary ammonium compounds is described.

Harrar, J.E.; Lorensen, L.E.; Locke, F.E.

1980-06-13

159

Design, fabrication, delivery, operation and maintenance of a geothermal power conversion system. final report  

SciTech Connect

The design, fabrication, delivery, operation and maintenance of an Hydrothermal Power Company 1250 KVA geothermal power conversion system using a helical screw expander as the prime mover is described. Hydrostatic and acceptance testing are discussed.

Not Available

1980-12-01

160

Design, fabrication, delivery, operation and maintenance of a geothermal power conversion system  

NASA Astrophysics Data System (ADS)

The design, fabrication, delivery, operation and maintenance of an Hydrothermal Power Company 1250 KVA geothermal power conversion system using a helical screw expander as the prime mover is described. Hydrostatic and acceptance testing are discussed.

1980-12-01

161

Design and Development of Geothermal Cooling System for Composite Climatic Zone in India  

NASA Astrophysics Data System (ADS)

The tropical climate buildings use about 70 % of operating energy for cooling of built environment. In composite climatic zone like Nagpur, Maharashtra, India several electro-mechanical cooling appliances viz., evaporative coolers, air conditioners, etc. are used. Application of geothermal cooling system is a very apt option for saving energy and reducing emission when compared to conventional cooling techniques. In the present work design methodology of geothermal cooling system is broadly elaborated and is applied to a case study of an educational building located in composite climate. The application of conventional and geothermal cooling systems is compared in terms of energy consumption. It is found that geothermal cooling system saves around 90 % of electricity as compared to air conditioner and 100 % of water as compared to evaporative coolers. This approach can further be extended for larger applications that will reduce consumption of energy and water in buildings.

Ralegaonkar, R.; Kamath, M. V.; Dakwale, V. A.

2014-09-01

162

Clay alteration of volcaniclastic material in a submarine geothermal system, Bay of Plenty, New Zealand  

NASA Astrophysics Data System (ADS)

The Calypso Hydrothermal Vent Field (CHVF) is located along an offshore extension of the Taupo Volcanic Zone (TVZ), an area of abundant volcanism and geothermal activity on the North Island of New Zealand. The field occurs within a northeast-trending submarine depression on the continental shelf approximately 10-15 km southwest of the White Island volcano in the Bay of Plenty. The graben has been partially filled by tephra from regional subaerial volcanic eruptions, and active hydrothermal venting occurs at several locations along its length. The vents occur at water depths of 160 to 190 m and have temperatures up to 201 °C. Recovered samples from the vent field include variably cemented and veined volcaniclastic sediments containing an assemblage of clay minerals, amorphous silica, barite, As-Sb-Hg sulfides, and abundant native sulfur. The volcanic glass has been altered primarily to montmorillonite and mixed-layer illite-montmorillonite; illite, and possibly minor talc and mixed-layer chlorite-smectite or chlorite-vermiculite are also present. A hydrothermal versus diagenetic origin for the smectite is indicated by the presence of both illite and mixed-layer clays and by the correlation between the abundance of clay minerals and the abundance of native sulfur in the samples. The mineralization and alteration of the volcanic host rocks are similar to that observed in near-neutral pH geothermal systems on land in the TVZ (e.g., Broadlands-Ohaaki). However, the clay minerals in the CHVF have a higher concentration of Mg in the dioctahedral layer and a higher interlayer Na content than clay minerals from Broadlands-Ohaaki, reflecting the higher concentrations of Mg and Na in seawater compared to meteoric water. Minerals formed at very low pH (e.g., kaolinite and alunite), typical of steam-heated acid-sulfate type alteration in the TVZ geothermal environment, were not found. Mixing with seawater likely prevented the formation of such low-pH mineral assemblages. The occurrence of illite and mixed-layer illite-smectite close to the seafloor in the CHVF, rather than at depth as in the Broadlands system, is interpreted to reflect the higher pressures associated with submarine venting. This allows hotter fluids to be discharged before they boil, and thus minerals that are encountered mainly at depth in subaerial geothermal systems can form close to the seafloor.

Hocking, Michael W. A.; Hannington, Mark D.; Percival, Jeanne B.; Stoffers, Peter; Schwarz-Schampera, Ulrich; de Ronde, C. E. J.

2010-04-01

163

Geochemical studies of the geothermal systems in Kenya: II. The Majimoto geothermal field  

NASA Astrophysics Data System (ADS)

The Majimoto geothermal field discharges at the boundary between metamorphic schists and gneisses of Precambrian age, and Pleistocene volcanic ashes. The waters are near neutral, low salinity waters. Calculated reservoir temperatures are about 90°C. Oxygen and hydrogen isotopes indicate that the thermal waters are meteoric in origin. The field is suitable for development for uses in spa therapy, crop drying, milk pasteurisation, leather processing and house warming.

Tole, Mwakio P.

1992-04-01

164

Geothermal Reservoir Dynamics - TOUGHREACT  

SciTech Connect

This project has been active for several years and has focused on developing, enhancing and applying mathematical modeling capabilities for fractured geothermal systems. The emphasis of our work has recently shifted towards enhanced geothermal systems (EGS) and hot dry rock (HDR), and FY05 is the first year that the DOE-AOP actually lists this project under Enhanced Geothermal Systems. Our overall purpose is to develop new engineering tools and a better understanding of the coupling between fluid flow, heat transfer, chemical reactions, and rock-mechanical deformation, to demonstrate new EGS technology through field applications, and to make technical information and computer programs available for field applications. The objectives of this project are to: (1) Improve fundamental understanding and engineering methods for geothermal systems, primarily focusing on EGS and HDR systems and on critical issues in geothermal systems that are difficult to produce. (2) Improve techniques for characterizing reservoir conditions and processes through new modeling and monitoring techniques based on ''active'' tracers and coupled processes. (3) Improve techniques for targeting injection towards specific engineering objectives, including maintaining and controlling injectivity, controlling non-condensable and corrosive gases, avoiding scale formation, and optimizing energy recovery. Seek opportunities for field testing and applying new technologies, and work with industrial partners and other research organizations.

Pruess, Karsten; Xu, Tianfu; Shan, Chao; Zhang, Yingqi; Wu,Yu-Shu; Sonnenthal, Eric; Spycher, Nicolas; Rutqvist, Jonny; Zhang,Guoxiang; Kennedy, Mack

2005-03-15

165

Stable isotope studies of some low enthalpy geothermal systems in Kenya  

NASA Astrophysics Data System (ADS)

Oxygen and hydrogen isotope compositions of some low enthalpy geothermal systems in Kenya have been determined. Plots on ? 18O versus ?D diagrams show that the compositions do not deviate appreciably from local meteoric water values. This would indicate that local meteoric waters are heated at depth and rise to the surface without much interaction with the country rocks. This is interpreted to be the case for the geothermal systems at Majimoto and Narosura, which have salinities of less than 350 ppm TDS and calculated reservoir temperatures of less than 110°C. The geothermal systems at Kapedo and Homa mountain which have high salinities (> 2 000 ppm TDS) and relatively higher calculated reservoir temperatures (> 150° C) are interpreted to have been operating for long periods of time, such that the rocks through which the present day geothermal waters are circulating have attained isotopic equilibrium with local meteoric waters.

Tole, Mwakio P.

166

Hybrid Cooling Systems for Low-Temperature Geothermal Power Production  

SciTech Connect

This paper describes the identification and evaluation of methods by which the net power output of an air-cooled geothermal power plant can be enhanced during hot ambient conditions with a minimal amount of water use.

Ashwood, A.; Bharathan, D.

2011-03-01

167

Enhanced Geothermal Systems (EGS) R&D Program: Monitoring EGS-Related Research  

SciTech Connect

This report reviews technologies that could be applicable to Enhanced Geothermal Systems development. EGS covers the spectrum of geothermal resources from hydrothermal to hot dry rock. We monitored recent and ongoing research, as reported in the technical literature, that would be useful in expanding current and future geothermal fields. The literature review was supplemented by input obtained through contacts with researchers throughout the United States. Technologies are emerging that have exceptional promise for finding fractures in nonhomogeneous rock, especially during and after episodes of stimulation to enhance natural permeability.

McLarty, Lynn; Entingh, Daniel; Carwile, Clifton

2000-09-29

168

Geochemical characterisation of hydrothermally altered ignimbrites in active geothermal fields from the central Taupo Volcanic Zone, New Zealand  

Microsoft Academic Search

Three subsurface ignimbrites at the active Orakeikorako geothermal field can be distinguished from one another despite their having been hydrothermally altered. They can also be recognised in drillcores from five other geothermal fields up to 18 km distant from Orakeikorako. “Fingerprinting” of the three Quaternary ignimbrites was attempted by comparing their petrographic, mineralogical and chemical compositions. Analyses of 43 samples

G. Bignall; P. R. L. Browne; P. R. Kyle

1996-01-01

169

The geothermal program at Lawrence Berkeley Laboratory  

SciTech Connect

The main purpose of the geothermal program at Lawrence Berkeley Laboratory is to develop, improve and validate methods and instrumentation to: (1) determine geothermal reservoir parameters; (2) detect and characterize reservoir fractures and boundaries; and (3) identify and evaluate the importance of reservoir processes. The ultimate objective of the program, which includes field, theoretical and modeling activities, is to advance the state-of-the-art for characterizing geothermal systems and evaluating their productive capacity and longevity under commercial exploitation.

Lippmann, M.J.

1987-06-01

170

The LBL geothermal reservoir technology program  

SciTech Connect

The main objective of the DOE/GD-funded Geothermal Reservoir Technology Program at Lawrence Berkeley Laboratory is the development and testing of new and improved methods and tools needed by industry in its effort to delineate, characterize, evaluate, and exploit hydrothermal systems for geothermal energy. This paper summarizes the recent and ongoing field, laboratory, and theoretical research activities being conducted as part of the Geothermal Reservoir Technology Program. 28 refs., 4 figs.

Lippmann, M.J.

1991-03-01

171

Energy Returned On Investment of Engineered Geothermal Systems Annual Report FY2010  

SciTech Connect

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. EROI analyses of geothermal energy are either out of date or presented online with little supporting documentation. Often comparisons of energy systems inappropriately use 'efficiency' when EROI would be more appropriate. For geothermal electric power generation, EROI is determined by the electric energy delivered to the consumer compared to the energy consumed to build, operate, and decommission the facility.

Mansure, A.J.

2010-12-31

172

The volcanic and geothermally active Campi Flegrei caldera: an integrated multidisciplinary image of its buried structure  

NASA Astrophysics Data System (ADS)

The Campi Flegrei caldera in southern Italy is one of the greatest geohazard areas on Earth. Evidence of an active magmatic and geothermal system is provided by ongoing ground uplift, with volcano-tectonic and long-period (LP) seismicity, the persistent degassing of ~1500 tonnes of CO2 per day, the presence of hot fumaroles at temperatures of 90-150 °C, brine-rich aquifers (with total dissolved solids up to 33 g l-1) and high thermal gradients in the crust (with temperatures reaching 420 °C at 3,050 m b.s.l.). Since the 1940s, more than 100 exploratory boreholes have been drilled in the area to depths of 80-3,100 m by the Azienda Geologica Italiana Petroli (AGIP) and the Societŕ Anonima Forze Endogene Napoletane (SAFEN). To date, however, no systematic reanalysis of the drilling data has been carried out, and the buried volcanic structure has not been updated using the most recent scientific results and previous findings. By integrating unpublished data from the AGIP and SAFEN reports with published information from geological, volcanological, petrological, petrophysical and geophysical studies, this paper presents an improved picture of the Campi Flegrei caldera that will be useful for volcanic hazard assessment and mitigation in the Naples area and for future research planning. The results suggest that intra-caldera activity has been influenced by how the magmatic system at depths greater than about 4 km has determined the transfer of magma, volatiles, and heat to the overlying geothermal system and, ultimately, to the surface. In particular, intriguing is that the most volcanically active central-eastern sector of the caldera, which is subject to intense bradyseismic ground movement and gas emission, coincides with a structurally delimited subsurface rock volume characterized by an uprising of the 100 °C isotherm, a deep water supply to the shallower aquifer, the early disappearance of secondary calcite, LP seismicity and high seismic S-wave attenuation. In this area, we also document evidence of repeated injection at depths of c. 1.5-3.0 km of isolated and small-volume batches of magma, where occurred their crystallization and degassing. Shallow intrusions and degassing of magma are thus identified as two of the key processes that drive unrest in Campi Flegrei.

Piochi, M.; Kilburn, C. R. J.; Di Vito, M. A.; Mormone, A.; Tramelli, A.; Troise, C.; De Natale, G.

2014-03-01

173

Preliminary assessment of the geothermal system of the Tiris volcanic area, East Java, Indonesia.  

NASA Astrophysics Data System (ADS)

Indonesia, with 15 % of the world's active volcanoes, hosts a total estimated geothermal potential of 27000 MW of which 1197 MWe in 2011 have been installed. Exploration of magmatic remote areas is therefore important. Our investigation area is located at the volcano Lamongan, Tiris East Java, Indonesia, which is part of the modern Sunda Arc Region, characterized by extensional regime. The average ground water temperature in the area ranges between 27 and 29 ° C and the warm springs between 35 - 45 ° C, evidencing a geothermal potential of the area. Numerous maars and cindered cones have been located and studied here, some of them with a NW - SE lineament similar to the Tiris fault (only observed in satellite images). In this first exploration stage we characterized the geochemistry of the springs and investigated the petrology of the rocks. They were analyzed in terms of mineral composition (optical microscopy and electron microprobe) and major element composition (X-ray fluorescence). The samples have a typical basaltic - basaltic andesite composition, with abundant plagioclase with An65 up to An90, as well as olivine and pyroxene. The plagioclase crystals are several mm large, twinned and show no hydrothermal alteration. The fluid chemistry was determined in term of cation and anion concentration with Inductively Coupled Plasma Mass Spectrometry. The chemistry of geothermal waters provides specific information about the deep of the fluids in geothermal system and the discharge location. The concentrations of Na+, Ca2+, Li+, B3+ and Cl- suggest that the water of the Lamongan area derive from sea water intrusions. The high permeable pyroclastites, overlain by lower permeable basalt - andesitic basalt, observed in the field, may have channeled the sea water from the coast to the Tiris area. A structural lineament, NW - SE, may control the water intrusion, as the lineament of the springs confirms. The high HCO3-concentration in the fluid samples, as no carbonate rocks are known in the area, must derive from another source (magma chamber?). The occurrence of pyroclastites overlain by andesite suggests the presence of a concealed layer. This could be responsible for capturing SO42- accounting to the HCO3- excess of the springs, located in the outflow zone of the system. Acknowledgements We thank the German Federal Ministry for Education and Research (BMBF) for funding this German project under the grant 03G0753A. We would also like to thank Iris Pieper for the ICP water analyses at the TU Berlin, and DINAS ESDM, Surabaya, Indonesia for their support in the field campaigns.

Deon, F.; Moeck, I.; Sheytt, T.; Jaya, M. S.

2012-04-01

174

Real-time fracture monitoring in Engineered Geothermal Systems with seismic waves  

SciTech Connect

As proposed, the main effort in this project is the development of software capable of performing real-time monitoring of micro-seismic activity recorded by an array of sensors deployed around an EGS. The main milestones are defined by the development of software to perform the following tasks: • Real-time micro-earthquake detection and location • Real-time detection of shear-wave splitting • Delayed-time inversion of shear-wave splitting These algorithms, which are discussed in detail in this report, make possible the automatic and real-time monitoring of subsurface fracture systems in geothermal fields from data collected by an array of seismic sensors. Shear wave splitting (SWS) is parameterized in terms of the polarization of the fast shear wave and the time delay between the fast and slow shear waves, which are automatically measured and stored. The measured parameters are then combined with previously measured SWS parameters at the same station and used to invert for the orientation (strike and dip) and intensity of cracks under that station. In addition, this grant allowed the collection of seismic data from several geothermal regions in the US (Coso) and Iceland (Hengill) to use in the development and testing of the software.

Jose A. Rial; Jonathan Lees

2009-03-31

175

Assessment of the Geothermal System Near Stanley, Idaho  

SciTech Connect

The City of Stanley, Idaho (population 63) is situated in the Salmon River valley of the central Idaho highlands. Due to its location and elevation (6270 feet amsl) it is one of the coldest locales in the continental U.S., on average experiencing frost 290 days of the year as well as 60 days of below zero (oF) temperatures. Because of high snowfall (76 inches on average) and the fact that it is at the terminus of its rural grid, the city also frequently endures extended power outages during the winter. To evaluate its options for reducing heating costs and possible local power generation, the city obtained a rural development grant from the USDA and commissioned a feasibility study through author Roy Mink to determine whether a comprehensive site characterization and/or test drilling program was warranted. Geoscience students and faculty at Idaho State University (ISU), together with scientists from the Idaho Geological Survey (IGS) and Idaho National Laboratory (INL) conducted three field data collection campaigns between June, 2011 and November, 2012 with the assistance of author Beckwith who arranged for food, lodging and local property access throughout the field campaigns. Some of the information collected by ISU and the IGS were compiled by author Mink and Boise State University in a series of progress reports (Makovsky et al., 2011a, b, c, d). This communication summarizes all of the data collected by ISU including data that were compiled as part of the IGS’s effort for the National Geothermal Data System’s (NGDS) data compilation project funded by the Department of Energy and coordinated by the Arizona Geological Survey.

Trent Armstrong; John Welhan; Mike McCurry

2012-06-01

176

Modeling of a deep-seated geothermal system near Tianjin, China.  

PubMed

A geothermal field is located in deep-seated basement aquifers in the northeastern part of the North China Plain near Tianjin, China. Carbonate rocks of Ordovician and Middle and Upper Proterozoic age on the Cangxian Uplift are capable of yielding 960 to 4200 m3/d of 57 degrees C to 96 degrees C water to wells from a depth of more than 1000 m. A three-dimensional nonisothermal numerical model was used to simulate and predict the spatial and temporal evolution of pressure and temperature in the geothermal system. The density of the geothermal water, which appears in the governing equations, can be expressed as a linear function of pressure, temperature, and total dissolved solids. A term describing the exchange of heat between water and rock is incorporated in the governing heat transport equation. Conductive heat flow from surrounding formations can be considered among the boundary conditions. Recent data of geothermal water production from the system were used for a first calibration of the numerical model. The calibrated model was used to predict the future changes in pressure and temperature of the geothermal water caused by two pumping schemes. The modeling results indicate that both pressure and temperature have a tendency to decrease with time and pumping. The current withdrawal rates and a pumping period of five months followed by a shut-off period of seven months are helpful in minimizing the degradation of the geothermal resource potential in the area. PMID:11341010

Xun, Z; Mingyou, C; Weiming, Z; Minglang, L

2001-01-01

177

Investigation of hydrogeochemical properties of the Hüdai (Afyon-Sand?kl?) geothermal systems, SW Turkey  

NASA Astrophysics Data System (ADS)

Sand?kl?-Hüdai geothermal field is one of the geothermal systems in Afyon and environ, located approximately 40 km southwest of Afyon. The study area consists of volcanic, sedimentary and metamorphic rocks. Kestel greenschist formation of Paleozoic age forms the basement rock in the area while quartzite which is a member of the Kestel greenschist formation serves as the reservoir rock of Sand?kl?-Hüdai geothermal system. Geothermal waters from the study area are classified as Na-SO4-HCO3 type waters. The waters plot along SO4-HCO3 end of the Cl-SO4-HCO3 triangle diagram suggesting same origin for the geothermal waters. ? 18O and ?D isotope ratios of the Sand?kl? waters plot along the continental meteoric water line, indicating meteoric waters that were unaffected by evaporation. The tritium values imply that the fluids were deep circulating and recharged from older waters. Furthermore, oversaturation of the geothermal fluids with quartz confirms these findings showing long time residence of these groundwaters.

Demer, Selma (Altinkale); Memi?, Ümit; Özgür, Nevzat

2013-08-01

178

Stress corrosion cracking of stainless steels in geothermal systems  

SciTech Connect

A failure analysis was made with an austenitic stainless steel, YUS 170, pipe installed close to a flush tank of the field exposure test apparatus at Onikobe geothermal wells in Japan. The pipe eventually experienced severe leakage of geothermal fluids from the top side of the laid pipe within 2 weeks operation. The cracks initiated underneath thick deposits and propagated toward thickness direction transgranularly. The analysis of the deposits, corrosion products and fractographic observation have indicated that chloride stress corrosion cracking is responsible for the leakage. This study suggests that the condensation of salts on steel surfaces may cause serious corrosion problems in addition to those in flowing geothermal fluids. The replacement of YUS 170 by Low C-19 Cr-2Mo ferritic stainless steel, YUS 190, has resulted in no stress corrosion cracking for more than 8 months in the same environmental conditions.

Murata, T.; Sato, E.; Hosoi, Y.

1982-01-01

179

Creation of an Enhanced Geothermal System through Hydraulic and Thermal Stimulation  

SciTech Connect

This report describes a 10-year DOE-funded project to design, characterize and create an Engineered Geothermal System (EGS) through a combination of hydraulic, thermal and chemical stimulation techniques. Volume 1 describes a four-year Phase 1 campaign, which focused on the east compartment of the Coso geothermal field. It includes a description of the geomechanical, geophysical, hydraulic, and geochemical studies that were conducted to characterize the reservoir in anticipation of the hydraulic stimulation experiment. Phase 1 ended prematurely when the drill bit intersected a very permeable fault zone during the redrilling of target stimulation well 34-9RD2. A hydraulic stimulation was inadvertently achieved, however, since the flow of drill mud from the well into the formation created an earthquake swarm near the wellbore that was recorded, located, analyzed and interpreted by project seismologists. Upon completion of Phase 1, the project shifted focus to a new target well, which was located within the southwest compartment of the Coso geothermal field. Volume 2 describes the Phase 2 studies on the geomechanical, geophysical, hydraulic, and geochemical aspects of the reservoir in and around target-stimulation well 46A-19RD, which is the deepest and hottest well ever drilled at Coso. Its total measured depth exceeding 12,000 ft. It spite of its great depth, this well is largely impermeable below a depth of about 9,000 ft, thus providing an excellent target for stimulation. In order to prepare 46A-19RD for stimulation, however, it was necessary to pull the slotted liner. This proved to be unachievable under the budget allocated by the Coso Operating Company partners, and this aspect of the project was abandoned, ending the program at Coso. The program then shifted to the EGS project at Desert Peak, which had a goal similar to the one at Coso of creating an EGS on the periphery of an existing geothermal reservoir. Volume 3 describes the activities that the Coso team contributed to the Desert Peak project, focusing largely on a geomechanical investigation of the Desert Peak reservoir, tracer testing between injectors 21-2 and 22-22 and the field�������¢����������������s main producers, and the chemical stimulation of target well 27-15.

Rose, Peter Eugene [Energy and Geoscience Institute at the University of Utah

2013-04-15

180

Creation of an Enhanced Geothermal System through Hydraulic and Thermal Stimulation  

SciTech Connect

This report describes a 10-year DOE-funded project to design, characterize and create an Engineered Geothermal System (EGS) through a combination of hydraulic, thermal and chemical stimulation techniques. Volume 1 describes a four-year Phase 1 campaign, which focused on the east compartment of the Coso geothermal field. It includes a description of the geomechanical, geophysical, hydraulic, and geochemical studies that were conducted to characterize the reservoir in anticipation of the hydraulic stimulation experiment. Phase 1 ended prematurely when the drill bit intersected a very permeable fault zone during the redrilling of target stimulation well 34-9RD2. A hydraulic stimulation was inadvertently achieved, however, since the flow of drill mud from the well into the formation created an earthquake swarm near the wellbore that was recorded, located, analyzed and interpreted by project seismologists. Upon completion of Phase 1, the project shifted focus to a new target well, which was located within the southwest compartment of the Coso geothermal field. Volume 2 describes the Phase 2 studies on the geomechanical, geophysical, hydraulic, and geochemical aspects of the reservoir in and around target-stimulation well 46A-19RD, which is the deepest and hottest well ever drilled at Coso. Its total measured depth exceeding 12,000 ft. It spite of its great depth, this well is largely impermeable below a depth of about 9,000 ft, thus providing an excellent target for stimulation. In order to prepare 46A-19RD for stimulation, however, it was necessary to pull the slotted liner. This proved to be unachievable under the budget allocated by the Coso Operating Company partners, and this aspect of the project was abandoned, ending the program at Coso. The program then shifted to the EGS project at Desert Peak, which had a goal similar to the one at Coso of creating an EGS on the periphery of an existing geothermal reservoir. Volume 3 describes the activities that the Coso team contributed to the Desert Peak project, focusing largely on a geomechanical investigation of the Desert Peak reservoir, tracer testing between injectors 21-2 and 22-22 and the field�s main producers, and the chemical stimulation of target well 27-15.

Rose, Peter Eugene [Energy and Geoscience Institute at the Univerity of Utah

2013-04-15

181

Chemistry of gases associated with geothermal activity and volcanism in Iceland: A review  

NASA Astrophysics Data System (ADS)

The concentrations of CO2, H2S, and H2 in geothermal reservoir fluids in Iceland are fixed by equilibria with alteration minerals. CH4 concentrations are typically very low, and gas-gas equilibria involving CO2, H2, and CH4 are generally not closely approached. In some geothermal systems the N2 is atmospheric only, but a magmatic N2 contribution is significant in others. N2/Ar ratios lie mostly between that of the atmosphere (85) and the N2/Ar ratio in cold water in contact with the atmosphere (37). Fluids with a strong magmatic N2 contribution have N2/Ar ratios of 40-60. During several volcanic eruptions in Iceland, magmatic gases have emerged at the surface beyond the eruptive vents and mixed with surrounding groundwaters. CO and H2 can be detected closest to the vent, but only CO2 is detected at greater distances. During the present volcanic episode at Krafla, fugitive constituents have been transported into the geothermal reservoir from the underlying magma chamber. Probably most of the carbon and sulphur in altered rocks of high-temperature geothermal systems have been derived from degassing magma bodies.

Arnórsson, StefáN.

1986-11-01

182

The Role of Boron-Chloride and Noble Gas Isotope Ratios in TVZ Geothermal Systems  

SciTech Connect

The model of the geothermal system in which deep circulating groundwater containing noble gases, at air saturated water concentrations, mixes with hot fluids of mantle origin at depth, is extended to include the effect of interaction of the ascending fluid with both solid and gaseous phases of basement (or other) rocks en route to the surface. It is demonstrated that this interaction is responsible for most of the CO{sub 2} in the Taupo Volcanic Zone (TVZ) geothermal systems. It is proposed that the modeling of this interaction might be accomplished by techniques similar to those used for the understanding of the oxygen isotope shift found in geothermal systems. The water rock interaction experiments of Ellis and Mahon (1964, 1967) provides some data on the kinetic rates for B and Cl dissolution from rocks likely to be encountered in the geothermal system, but further information on the behavior of B may be needed. If these problems can be overcome this modeling technique has promise for the estimation of the recharge of geothermal systems and hence the sustainability of these systems.

Hulston, J.R.

1995-01-01

183

Geochemical properties of groundwater used to geothermal cooling and heating system  

NASA Astrophysics Data System (ADS)

Recently, geothermal cooling and heating system has been used in many countries to reduce emission of greenhouse gases such as water vapour and carbon dioxide (CO2). Especially, CO2 is emitted from combustion of fossil fuel used for cooling and heating of buildings. Therefore, many countries make an effort to reduce amount of CO2 emitted from use of fossil fuel. The geothermal cooling and heating system is good to reduce amount of CO2. Especially, open loop geothermal system shows good thermal efficiency. However, groundwater contaminations will be considered because groundwater is directly used in open loop geothermal system. This study was performed to examine chemical and isotope compositions of groundwater used in open loop geothermal system and to evaluate influence of the system on groundwater using hydrochemical modeling program (preequc). Water temperature of well used in the system (GH) and well around the system (GB) ranged from 8.4 to 17.0 ° and from 15.1 to 18.0 °, respectively. The water temperature in GH was lower than that in GB because of heating mode of the system. Also, EC in GH and GB showed significant difference. The variation trend of EC was different at each site where the system was installed. These results mean that main factors controlling EC in GH was not the system. Generally, EC of groundwater was influenced by water-rock interaction. However, DO and Eh hardly showed significant difference. The operation period of the system observed in this study was short than 5 years. Therefore, influence of the open loop geothermal system on groundwater did not shown significantly. However, while Fe2+ and Mn2+ were not observed in GB, these components were measured in GH. The concentrations of Fe2+ and Mn2+ in GH ranged from 0.02 to 0.14 mg/L and from 0.03 to 0.18 mg/L, respectively. These results mean that redox conditions of GH were changed by the system little by little. In this study, influence of the open loop geothermal system on groundwater did not shown significantly. However, change of redox condition was slightly observed. To significantly observe influence of the open loop geothermal system, monitoring for well installed the system is necessary during long period. This work was supported by the Energy Efficiency and Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20123040110010).

Kim, Namju; Park, Youngyun; Lee, Jin-Yong

2013-04-01

184

Increasing the efficiency of geothermal power plants using optimum pressures for turbocompressors and steam jet ejectors in gas extraction systems  

NASA Astrophysics Data System (ADS)

Geothermal power plants generate electricity by extracting energy from the earth's interior. The radioactive decay of the earth's core causes heat to conduct towards the surface. When water flows into the fissures of this hot rock a naturally occurring geothermal well is formed. Geothermal power plants use the steam in these wells to drive a turbine and thus generate electricity. The steam in the earth however, is always accompanied by a small fraction of non-condensable gases that build up in the power plant's condenser unless actively removed by some gas extraction system. Because these gases contribute significantly to the total backpressure on the turbine, it is in the interest of power generation to remove them from the condenser. The industry standard for removing these non-condensable gases has been steam jet ejectors or a hybrid system of steam jet ejectors and liquid ring vacuum pumps. This thesis focuses on finding the optimum operating pressures for a hybrid steam jet ejector system and a hybrid turbocompressor system. It was found that plants with steam jet ejectors and liquid ring vacuum pumps provide maximum power output when the liquid ring vacuum pump is operated at its maximum pressure ratio. However, plants with a turbocompressor and liquid ring vacuum pump were found to provide maximum power output when the turbocompressor was operated at its maximum pressure ratio.

Harns, Karsten Franz

185

Thermal regime of the Great Basin and its implications for enhanced geothermal systems and off-grid power  

USGS Publications Warehouse

The Basin and Range Province of the Western United States covers most of Nevada and parts of adjoining states. It was formed by east-west tectonic extension that occurred mostly between 50 and 10 Ma, but which still is active in some areas. The northern Basin and Range, also known as the Great Basin, is higher in elevation, has higher regional heat flow and is more tectonically active than the southern Basin and Range which encompasses the Mojave and Sonoran Deserts. The Great Basin terrane contains the largest number of geothermal power plants in the United States, although most electrical production is at The Geysers and in the Salton Trough. Installed capacities of electrical power plants in the Great Basin vary from 1 to 260 MWe. Productivity is limited largely by permeability, relatively small productive reservoir volumes, available water, market conditions and the availability of transmission lines. Accessible, in-place heat is not a limiting condition for geothermal systems in the Great Basin. In many areas, economic temperatures (>120°C) can be found at economically drillable depths making it an appropriate region for implementation of the concept of "Enhanced Geothermal Systems" (EGS). An incremental approach to EGS would involve increasing the productivity and longevity of existing hydrothermal systems. Those geothermal projects that have an existing power plant and transmission facilities are the most attractive EGS candidates. Sites that were not developed owing to marginal size, lack of intrinsic permeability, and distance to existing electrical grid lines are also worthy of consideration for off-grid power production in geographically isolated markets such as ranches, farms, mines, and smelters.

Sass, John H.; Walters, Mark A.

1999-01-01

186

Technical support for geopressured-geothermal well activities in Louisiana. Annual report, 1 November 1982-31 October 1983  

SciTech Connect

This annual report describes environmental monitoring of microseismic activity, land-surface elevations, and surface and ground-water quality at three designed geopressured-geothermal test well sites in Louisiana.

Not Available

1984-10-31

187

Technical support for geopressured-geothermal well activities in Louisiana. Final report, 1 November 1983-31 October 1984  

SciTech Connect

This report describes environmental monitoring of microseismic activity, land-surface subsidence, and surface and ground-water quality at three designed geopressured-geothermal test well sites in Louisiana. Separate abstracts have been prepared for individual sections. (ACR)

Not Available

1985-12-01

188

Secondary mineral growth in fractures in the Miravalles geothermal system, Costa Rica  

SciTech Connect

A mineralogical, fluid-chemical, and theoretical study of hydrothermal alteration in veins from drillcore from the Miravalles geothermal field, Costa Rica has revealed a complex history of mineral-fluid reaction which may be used to characterize changes in temperature and fluid composition with time. Mineralogical and mineral-chemical data are consistent with hydrothermal alteration in the temperature range 200{sup 0}-270{sup 0}C, with deeper portions of the system having undergone temperatures in excess of 300{sup 0}C. Thermodynamic calculations suggest that the observed alteration assemblage is not equilibrium with current well fluids, unless estimates of reservoir pH are incorrect. Fe-Al zoning of prehnite and epidote in veins is consistent with rapid, isothermal fluctuations in fluid composition at current reservoir temperatures, and may be due to changes in volatile content of the fluid due to tectonic activity.

Rochelle, C.A. (Leeds Univ. (UK). Dept. of Earth Sciences); Milodowski, A.E.; Savage, D. (British Geological Survey, Keyworth (UK). Fluid Processes Research Group); Corella, M. (Instituto Costarricense de Electricidad, San Jose (Costa Rica))

1989-01-01

189

Cooling performance and energy saving of a compression–absorption refrigeration system assisted by geothermal energy  

Microsoft Academic Search

The objectives of this paper are to develop a novel combined refrigeration system, and to discuss the thermodynamic analysis of the cycle and the feasibility of its practical development. The aim of this work was to study the possibility of using geothermal energy to supply vapour absorption system cascaded with conventional compression system. Three working fluids (R717, R22, and R134a)

L. Kairouani; E. Nehdi

2006-01-01

190

Evaluating Importance of Heat Transport Mechanisms Neglected in Design of Low Temperature Geothermal Systems  

Microsoft Academic Search

Design calculations for geothermal heating and cooling systems usually simplify or neglect many of the heat transport processes occurring in the subsurface. This is despite the fact that system efficiency, sustainability, and environmental impact all depend on heat transport in the subsurface. Design standards for the most popular systems, which use borehole heat exchangers, usually assume purely conductive heat transport

C. D. Langevin; M. C. Sukop

2009-01-01

191

Three-dimensional upper crustal structure of the geothermal system in Tarutung (North Sumatra, Indonesia) revealed by seismic attenuation tomography  

NASA Astrophysics Data System (ADS)

The geothermal potential in Tarutung is controlled by both the Sumatra Fault system and young arc volcanism. In this study we use the spatial distribution of seismic attenuation, calculated from local earthquake recordings, to image the 3-D seismic attenuation of the area and relate it with the temperature anomalies and the fluid distribution of the subsurface. A temporary seismic network of 42 stations was deployed around Tarutung and Sarulla (south of Tarutung) for a period of 10 months starting in 2011 May. Within this period, the network recorded 2586 local events. A high-quality subset of 229 events recorded by at least 10 stations was used for the attenuation inversion (tomography). Path-average attenuation (tp^{*}) was calculated by using a spectral inversion method. The spread function, the contour lines of the model resolution matrix and the recovery test results show that our 3-D attenuation model (Qp) has good resolution around the Tarutung Basin and along the Sarulla graben. High attenuation (low Qp) related to the geothermal system is found in the northeast of the Tarutung Basin suggesting fluid pathways from below the Sumatra Fault. The upper part of the studied geothermal system in the Tarutung district seems to be mainly controlled by the fault structure rather than by magmatic activities. In the southwest of the Tarutung Basin, the high attenuation zone is associated with the Martimbang volcano. In the Sarulla region, a low-Qp anomaly is found along the graben within the vicinity of the Hopong caldera.

Muksin, Umar; Haberland, Christian; Bauer, Klaus; Weber, Michael

2013-12-01

192

(Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)  

SciTech Connect

Our studies involved petrographic, fluid inclusion, geochemical and stable isotopic studies of drillcores and fluids from the Salton Sea geothermal system. Our initial studies revealed the presence of previously-unrecognized evaporitic anhydrite at depth throughout the geothermal system. The high salinity of the Salton Sea geothermal brines previously had been attributed to low-temperature dissolution of surficial evaporitic deposits by meteoric waters. Our microthermometric studies of halite--containing fluid inclusions in the meta-evaporites indicated that the high salinity of the geothermal brines is derived in part from the hydrothermal metamorphism of relatively deeply-buried salt and evaporites. In addition, our research concentrated on mineralized fractures in drillcores.

McKibben, M.A.

1988-06-01

193

GEOLOGIC AND GEOCHEMICAL INVESTIGATIONS OF THE MEAGER CREEK GEOTHERMAL SYSTEM, BRITISH COLUMBIA, CANADA  

SciTech Connect

Meager Creek is perhaps the most intensely explored geothermal system occurring in the Cascade and Garibaldi Volcanic Belts. This paper describes the results of new lithologic, petrographic, X-ray, isotopic, and geochemical investigations of core and cuttings from the Meager Creek wells. The data demonstrate that alteration related to the present geothermal system is superimposed on basement rocks which were metamorphosed and intruded by dioritic stocks prior to the onset of volcanism. The geothermal alteration developed mainly after emplacement of hypabyssal dikes associated with Meager Mountain volcanism and is characterized by mineral assemblages consisting primarily of sheet silicates, quartz, carbonate, hematite, iron oxides, pyrite, and minor epidote, potassium feldspar, actinolite and biotite. Permeabilities within the upper portions of the reservoir are low, reflecting filling of the fracture systems by carbonate. Petrographic observations suggest that sealing of the fractures accompanied hydrothermal brecciation and boiling of the fluids.

Moore, J.N.; Adams, M.C.; Stauder, J.J.

1985-01-22

194

Hydrology of the Greater Tongonan geothermal system, Philippines, as deduced from geochemical and isotopic data  

SciTech Connect

Fluids in the Greater Tongonan geothermal system exhibit a large positive {sup 18}O shift from the Leyte meteoric water line. However, there is also a significant shift in {sup 2}H. The {delta}{sup 2}H-{delta}{sup 18}O plot shows that the geothermal fluids may be derived by the mixing of meteoric water with local magmatic water. The most enriched water in the Greater Tongonan system, in terms of {delta}{sup 18}O, {delta}{sup 2}H and Cl, is comprised of approximately 40% magmatic water. Baseline isotope results support a hydrogeochemical model in which there is increasing meteoric water dilution to the southeast, from Mahiao to Sambaloran and towards Malitbog. The Cl-{delta}{sup 18}O plot confirms that the geothermal fluid in Mahanagdong, further southeast, is distinct from that of the Mahiao-Sambaloran-Malitbog system.

Alvis-Isidro, R.R.; Solana, R.R. [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines)] [Philippine National Oil Co.-Energy Development Corp., Fort Bonifacio (Philippines); D`amore, F.; Nuti, S. [Inst. Internazionale per le Ricerche Geotermiche, Pisa (Italy)] [Inst. Internazionale per le Ricerche Geotermiche, Pisa (Italy); Gonfiantini, R. [International Atomic Energy Agency, Vienna (Austria)] [International Atomic Energy Agency, Vienna (Austria)

1993-10-01

195

Direct utilization of geothermal heat in cascade application to aquaculture and greenhouse systems at Navarro College. Annual report, January 1984-September 1984  

SciTech Connect

Progress is reported on a project to use the 130/sup 0/F geothermal resource in central Texas. The system for cascading geothermal energy through aquaculture and greenhouse systems was completed and the first shrimp harvest was held. (MHR)

Smith, K.

1984-09-01

196

Enhanced Geothermal Systems in Urban Areas - Lessons Learned from the 2006 Basel ML3.4 Earthquake  

Microsoft Academic Search

We report on a recent deep-heat mining experiment carried out in 2006\\/2007 in the city of Basel (Switzerland). This pilot project was designed to produce renewable geothermal energy using the Enhanced Geothermal System (EGS) methodology. For developing the geothermal reservoir, a deep borehole was brought down to 5 km depth. Then, in December 2006, the deep-heat-mining project entered the first

T. Kraft; P. M. Mai; S. Wiemer; N. Deichmann; J. Ripperger; P. Kästli; C. E. Bachmann; D. Fäh; J. Woessner; D. Giardini

2009-01-01

197

Multicontinuum approach for modeling multiphase reactive geochemical and isotopic transport in geothermal systems (Invited)  

NASA Astrophysics Data System (ADS)

Reactive transport in geothermal systems is primarily governed by localized flow in fractures with heat and diffusive chemical exchange, and progressive alteration in the adjacent rock matrix. Modeling the fluid geochemistry over long path lengths in fault zones and fractured reservoirs, as well as long-term permeability changes, requires capturing processes from the scale of fracture apertures (microns) to kilometers. The Multiple-Interacting-Continua (MINC) approach developed for thermal-hydrological simulation of fractured geothermal systems (Pruess & Narasimhan, 1985) is particularly well suited for extension to reactive transport in fractured rock and evaluating permeability changes. Assessment of reaction rates in geothermal systems, however, becomes more difficult at higher temperatures because of the more rapid tendency towards equilibrium. Isotopic systems, such as 87Sr/86Sr, have been used successfully for evaluating rates of water-rock interaction (e.g., DePaolo, 2006), but full incorporation into reactive transport models has been limited. A MINC model is described that couples kinetic rates of mineral-water reactions with heat and fluid flow in fractured rock as well as changes in Sr isotopic ratios in secondary minerals and fluids. This is applied to analysis of hydrothermal alteration at Newberry Volcano, Oregon, the site of current geothermal exploration and enhanced geothermal system development. Model results show the development of a hydrothermal mineral assemblage under a present-day temperature regime similar to those observed, with inputs of magmatic CO2 and H2S. Estimates of the rates of isotopic changes in secondary minerals and in the fluid with groundwater injection are compared to the rates of mineral-water equilibration. The analysis of sites such as Newberry Volcano, where the mineralogy and temperatures are constrained by borehole data, can guide the setup of MINC simulations of hydrothermal or enhanced geothermal systems where only spring or vent fluid compositions and limited geologic information are available.

Sonnenthal, E. L.

2013-12-01

198

OPTIMIZATION OF HYBRID GEOTHERMAL HEAT PUMP SYSTEMS Scott Hackel, Graduate Research Assistant; Gregory Nellis, Professor; Sanford Klein,  

E-print Network

, simulation, TRNSYS 1 INTRODUCTION AND OBJECTIVE Geothermal heat pump systems have sustained extensive growth1 OPTIMIZATION OF HYBRID GEOTHERMAL HEAT PUMP SYSTEMS Scott Hackel, Graduate Research Assistant to the practicing engineer. This paper describes the development of a simulation tool that integrates physics

Wisconsin at Madison, University of

199

Statistical analysis of the induced Basel 2006 earthquake sequence: introducing a probability-based monitoring approach for Enhanced Geothermal Systems  

Microsoft Academic Search

Geothermal energy is becoming an important clean energy source, however, the stimulation of a reservoir for an Enhanced Geothermal System (EGS) is associated with seismic risk due to induced seismicity. Seismicity occurring due to the water injection at depth have to be well recorded and monitored. To mitigate the seismic risk of a damaging event, an appropriate alarm system needs

C. E. Bachmann; S. Wiemer; J. Woessner; S. Hainzl

2011-01-01

200

Computer simulation of borehole ground heat exchangers for geothermal heat pump systems  

Microsoft Academic Search

Computer simulation of borehole ground heat exchangers used in geothermal heat pump systems was conducted using three-dimensional implicit finite difference method with rectangular coordinate system. Each borehole was approximated by a square column circumscribed by the borehole radius. Borehole loading profile calculated numerically based on the prescribed borehole temperature profile under quasi-steady state conditions was used to determine the ground

C. K. Lee; H. N. Lam

2008-01-01

201

Understanding the Chena Hot Springs, Alaska, geothermal system using temperature and pressure data from exploration boreholes  

Microsoft Academic Search

Chena Hot Springs is a small, moderate temperature, deep circulating geothermal system, apparently typical of those associated to hot springs of interior Alaska. Multi-stage drilling was used in some exploration boreholes and was found to be useful for understanding subsurface flow characteristics and developing a conceptual model of the system. The results illustrate how temperature profiles illuminate varying pressure versus

Kamil Erkan; Gwen Holdmann; Walter Benoit; David Blackwell

2008-01-01

202

Development of Models to Simulate Tracer Behavior in Enhanced Geothermal Systems  

SciTech Connect

A recent report found that power and heat produced from engineered (or enhanced) geothermal systems (EGSs) could have a major impact on the United States while incurring minimal environmental impacts. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distributions, permeability/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the surface area available for heat transfer in EGS is necessary for commercial development of geothermal energy. The goal of this project is to provide integrated tracer and tracer interpretation tools to facilitate this characterization. Modeling capabilities are being developed as part of this project to support laboratory and field testing to characterize engineered geothermal systems in single- and multi-well tests using tracers. The objective of this report is to describe the simulation plan and the status of model development for simulating tracer tests for characterizing EGS.

Williams, Mark D.; Vermeul, Vincent R.; Reimus, P. W.; Newell, D.; Watson, Tom B.

2010-06-01

203

NATIONAL GEOTHERMAL DATA SYSTEM: AN EXEMPLAR OF OPEN ACCESS TO DATA  

SciTech Connect

The formal launch of National Geothermal Data System (NGDS – www.geothermaldata.org) in 2014 will provide open access to technical geothermal-relevant data from all of the Department of Energy- sponsored geothermal development and research projects and geologic data from all 50 states. By making data easily discoverable and accessible this system will open new exploration opportunities and shorten project development. The prototype data system currently includes multiple data nodes, and nationwide data online and available to the public, indexed through a single catalog under construction at http://search.geothermaldata.org. Data from state geological surveys and partners includes more than 5 million records online, including 1.48 million well headers (oil and gas, water, geothermal), 732,000 well logs, and 314,000 borehole temperatures and is growing rapidly. There are over 250 Web services and another 138 WMS (Web Map Services) registered in the system as of August, 2013. Additional data record is being added by companion projects run by Boise State University, Southern Methodist University, and the USGS. The National Renewable Energy Laboratory is managing the Geothermal Data Repository, an NGDS node that will be a clearinghouse for data from hundreds of DOE-funded geothermal projects. NGDS is built on the US Geoscience Information Network (USGIN) data integration framework, which is a joint undertaking of the USGS and the Association of American State Geologists (AASG). NGDS is fully compliant with the White House Executive Order of May 2013, requiring all federal agencies to make their data holdings publicly accessible online in open source, interoperable formats with common core and extensible metadata. The National Geothermal Data System is being designed, built, deployed, and populated primarily with grants from the US Department of Energy, Geothermal Technologies Office. To keep this operational system sustainable after the original implementation will require four core elements: continued serving of data and applications by providers; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges currently under consideration.

Blackman, Harold [Arizona Geological Survey; Blackman, Harold M. [Arizona Geological Survey; Blackman, Harold M. [Arizona Geological Survey; Blackman, Harold [Boise State University; Blackman, Harold [United States Department of Energy; Blackman, Harold

2013-10-01

204

National Geothermal Data System: an Exemplar of Open Access to Data  

NASA Astrophysics Data System (ADS)

The National Geothermal Data System's (NGDS - www.geothermaldata.org) formal launch in 2014 will provide open access to millions of datasets, sharing technical geothermal-relevant data across the geosciences to propel geothermal development and production. With information from all of the Department of Energy's sponsored development and research projects and geologic data from all 50 states, this free, interactive tool is opening new exploration opportunities and shortening project development by making data easily discoverable and accessible. We continue to populate our prototype functional data system with multiple data nodes and nationwide data online and available to the public. Data from state geological surveys and partners includes more than 5 million records online, including 1.48 million well headers (oil and gas, water, geothermal), 732,000 well logs, and 314,000 borehole temperatures and is growing rapidly. There are over 250 Web services and another 138 WMS (Web Map Services) registered in the system as of August, 2013. Companion projects run by Boise State University, Southern Methodist University, and USGS are adding millions of additional data records. The National Renewable Energy Laboratory is managing the Geothermal Data Repository which will serve as a system node and clearinghouse for data from hundreds of DOE-funded geothermal projects. NGDS is built on the US Geoscience Information Network data integration framework, which is a joint undertaking of the USGS and the Association of American State Geologists (AASG). NGDS is fully compliant with the White House Executive Order of May 2013, requiring all federal agencies to make their data holdings publicly accessible online in open source, interoperable formats with common core and extensible metadata. The National Geothermal Data System is being designed, built, deployed, and populated primarily with grants from the US Department of Energy, Geothermal Technologies Office. To keep this operational system sustainable after the original implementation will require four core elements: continued serving of data and applications by providers; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges currently under consideration.

Allison, M. L.; Richard, S. M.; Blackman, H.; Anderson, A.

2013-12-01

205

Numerical modeling of geothermal heat pump system: evaluation of site specific groundwater thermal impact  

NASA Astrophysics Data System (ADS)

A pilot plant using a geothermal open-loop heat pump system has been realized in the city of Vicenza (Northern Italy), in order to meet the heating and cooling needs of the main monumental building in the historical center, the Palladian Basilica. The low enthalpy geothermal system consists of a pumping well and a reinjection well, both intercepting the same confined aquifer; three other monitoring wells have been drilled and then provided with water level and temperature dataloggers. After about 1 year and a half of activity, during a starting experimental period of three years, we have now the opportunity to analyze long term groundwater temperature data series and to evaluate the numerical modeling reliability about thermal impact prediction. The initial model, based on MODFLOW and SHEMAT finite difference codes, has been calibrated using pumping tests and other field investigations data, obtaining a valid and reliable groundwater flow simulation. But thermal parameters, such as thermal conductivity and volumetric heat capacity, didn't have a site specific direct estimation and therefore they have been assigned to model cells referring to bibliographic standards, usually derived from laboratory tests and barely representing real aquifer properties. Anyway preliminary heat transport results have been compared with observed temperature trends, showing an efficient representation of the thermal plume extension and shape. The ante operam simulation could not consider heat pump real utilization, that happened to be relevantly different from the expected project values; so the first numerical model could not properly simulate the groundwater temperature evolution. Consequently a second model has been implemented, in order to calibrate the mathematical simulation with monitored groundwater temperature datasets, trying to achieve higher levels of reliability in heat transport phenomena interpretation. This second step analysis focuses on aquifer thermal parameters calibration and includes a new finite element FEFLOW simulation, as an useful comparison between different approaches to heat transport modeling.

Pedron, Roberto; Sottani, Andrea; Vettorello, Luca

2014-05-01

206

Selected data for low-temperature (less than 90{sup 0}C) geothermal systems in the United States: reference data for US Geological Survey Circular 892  

SciTech Connect

Supporting data are presented for the 1982 low-temperature geothermal resource assessment of the United States. Data are presented for 2072 geothermal sites which are representative of 1168 low-temperature geothermal systems identified in 26 States. The low-temperature geothermal systems consist of 978 isolated hydrothermal-convection systems, 148 delineated-area hydrothermal-convection systems, and 42 delineated-area conduction-dominated systems. The basic data and estimates of reservoir conditions are presented for each geothermal system, and energy estimates are given for the accessible resource base, resource, and beneficial heat for each isolated system.

Reed, M.J.; Mariner, R.H.; Brook, C.A.; Sorey, M.L.

1983-12-15

207

Selected data for low-temperature (less than 90 degrees C) geothermal systems in the United States; reference data for U.S. Geological Survey Circular 892  

USGS Publications Warehouse

Supporting data are presented for the 1982 low-temperature geothermal resource assessment of the United States. Data are presented for 2072 geothermal sites which are representative of 1168 low-temperature geothermal systems identified in 26 States. The low-temperature geothermal systems consist of 978 isolated hydrothermal-convection systems, 148 delineated-area hydrothermal-convection systems, and 42 delineated-area conduction-dominated systems. The basic data and estimates of reservoir conditions are presented for each geothermal system, and energy estimates are given for the accessible resource base, resource, and beneficial heat for each isolated system.

Reed, Marshall J.; Mariner, R.H.; Brook, C.A.; Sorey, M.L.

1983-01-01

208

Temperatures, heat flow, and water chemistry from drill holes in the Raft River geothermal system, Cassia County, Idaho  

SciTech Connect

The Raft River area of Idaho contains a geothermal system of intermediate temperatures (approx. = 150/sup 0/C) at depths of about 1.5 km. Outside of the geothermal area, temperature measurements in three intermediate-depth drill holes (200 to 400 m) and one deep well (1500 m) indicate that the regional conductive heat flow is about 2.5 ..mu..cal/cm/sup 2/ sec or slightly higher and that temperature gradients range from 50/sup 0/ to 60/sup 0/C/km in the sediments, tuffs, and volcanic debris that fill the valley. Within and close to the geothermal system, temperature gradients in intermediate-depth drill holes (100 to 350 m) range from 120/sup 0/ to more than 600/sup 0/C/km, the latter value found close to an artesian hot well that was once a hot spring. Temperatures measured in three deep wells (1 to 2 km) within the geothermal area indicate that two wells are in or near an active upflow zone, whereas one well shows a temperature reversal. Assuming that the upflow is fault controlled, the flow is estimated to be 6 liter/sec per kilometer of fault length. From shut-in pressure data and the estimated flow, the permeability times thickness of the fault is calculated to be 2.4 darcy m. Chemical analyses of water samples from old flowing wells, recently completed intermediate-depth drill holes, and deep wells show a confused pattern. Geothermometer temperatures of shallow samples suggest significant re-equilibration at temperatures below those found in the deep wells. Silica geothermometer temperatures of water samples from the deep wells are in reasonable agreement with measured temperatures, whereas Na-K-Ca temperatures are significantly higher than measured temperatures. The chemical characteristics of the water, as indicated by chloride concentration, are extremely variable in shallow and deep samples. Chloride concentrations of the deep samples range from 580 to 2200 mg/kg.

Nathenson, M.; Urban, T.C.; Diment, W.H.; Nehring, N.L.

1980-01-01

209

Reservoir modelling of deep geothermal systems: the examples of Guardia Lombardi  

NASA Astrophysics Data System (ADS)

In the framework of the VIGOR project, a characterization of medium enthalpy geothermal resources was carried out in the Campania region (southern Italy), with a focus on the "Guardia dei Lombardi" area (Avellino). The VIGOR project started on the basis of an agreement between the Ministry of Economic Development and the Italian National Research Council, and it deals with the exploitation of innovative uses of geothermal energy in the so-called "regions of convergence" (Campania, Calabria, Puglia and Sicily). One of the main results of this research is the development of an integrated 3D geological model, which provides the base for a detailed assessment of possible geothermal exploitation of the carbonate reservoir. The preliminary results of our study suggest that "Guardia dei Lombardi" can be indicated as an interesting area for medium enthalpy geothermal exploitation, although the presence of a CO2 gas cap and the scaling capability of the deep fluids need to be carefully evaluated. The aim of this work is to give an estimation of a geothermal well productivity, in the case of a geothermal exploitation. The geothermal well that is thought to be more suitable in the Guardia dei Lombardi Area is named Bonito 1 Dir, a well with a measured temperature of 118 °C at 3,107m depth, which gives a corrected temperature of 138 °C with an error of 8 °C. The pressure was found to be nearly hydrostatic, with 266.9 bar at 2992.4 m depth, and the potential reservoir is hosted in the Mesozoic carbonate formation. According to hydraulic tests, we found that the permeability porosity product gives nearly 100 mD for the carbonatic formation. Since the matrix porosity is nearly 1% with 0.65 mD from core drilled tests, the result of the hydraulic test is to be related to a fractured system; in this case, there is no a clear relation among porosity and permeability, thus we had a sensitivity check on the possible porosity-permeability values of the system, keeping as a constrain the value obtained from the hydraulic test. From the 3D geological model we obtained the boundary of the carbonate formation hosting the geothermal reservoir, and we modelled the cases of both a single producing well and a geothermal doublet in order to give an estimation of the geothermal potential. Deposition of calcite in a formation may significantly reduce the inflow performance of geothermal wells producing brine with CO2-rich content. The key operational and reservoir parameters influencing the magnitude of impairment by calcite deposition were identified through the numerical modelling of the rate of calcite deposition and its effect on flow rate assuming idealized flow conditions. This is an important constrain for a well lifetime, especially in the case of a 138 °C well, because the power production requires a large fluid flow, and an encrustating fluid may severely affect the geothermal well performance. The results of the model, in terms of fluid flow at wellhead and scaling potential, will be available for an economic evaluation of the feasibility of geothermal exploitation of the Bonito 1 Dir well, in the Guardia dei Lombardi area.

Montegrossi, Giordano; Inversi, Barbara; Scrocca, Davide

2013-04-01

210

Deep geothermal resources and energy: Current research and developments  

NASA Astrophysics Data System (ADS)

Energy from deep geothermal resources plays an increasing role in many European countries in their efforts to increase the proportion of renewables in their energy portfolio. Deep geothermal heat and electric power have a high load factor, are sustainable and environmentally friendly. However, the safe, sustainable, and economic development of deep geothermal resources, also in less favourable regions, faces a number of issues requiring substantial research efforts: (1) The probability of finding an unknown geothermal reservoir has to be improved. (2) Drilling methods have to be better adapted and developed to the specific needs of geothermal development. (3) The assessment of the geothermal potential should provide more reliable and clear guidelines for the development. (4) Stimulation methods for enhanced geothermal systems (EGS) have to be refined to increase the success rate and reduce the risk associated with induced seismicity. (5) Operation and maintenance in aggressive geothermal environments require specific solutions for corrosion and scaling problems. (6) Last but not least, emerging activities to harness energy from supercritical reservoirs would make significant progress with qualified input from research. In particular, sedimentary basins like e.g. the North German and Polish Basin, the Pannonian Basin, the Po Valley, the Bavarian Molasse Basin or the Upper Rhine Graben have a high geothermal potential, even if geothermal gradients are moderate. We will highlight projects that aim at optimizing exploration, characterization, and modeling prior to drilling and at a better understanding of physical, hydraulic and chemical processes during operation of a geothermal power plant. This includes geophysical, geological and geochemical investigations regarding potential geothermal reservoirs in sedimentary basins, as well as modelling of geothermally relevant reservoir parameters that influence the potential performance and long-term behavior of a future geothermal power plant. In our overview we will also highlight contributions of EGU2012-sessions ERE1.6 (Geothermal energy from deep sedimentary basins - exploration, exploitation, characterization and modeling) and ERE1.7 (Development of deep geothermal resources).

Manzella, A.; Milsch, H.; Hahne, B.; van Wees, J. D.; Bruhn, D.

2012-04-01

211

Use of solar assisted geothermal heat pump and small wind turbine systems for heating agricultural and residential buildings  

Microsoft Academic Search

The main objective of the present study is twofold: (i) to analyze thermal loads of the geothermally and passively heated solar greenhouses; and (ii) to investigate wind energy utilization in greenhouse heating which is modeled as a hybrid solar assisted geothermal heat pump and a small wind turbine system which is separately installed in the Solar Energy Institute of Ege

Onder Ozgener

2010-01-01

212

Geochemical and Energetic Variability across Geothermal Systems in Yellowstone National Park (YNP)  

NASA Astrophysics Data System (ADS)

The physical and chemical characteristics of geothermal outflow channels have been evaluated and correlated with microbial community structure within a variety of geothermal springs in Yellowstone National Park (YNP). Several high-temperature (75-90 C), low to near-neutral pH hot springs in YNP were characterized over a two-year period for a comprehensive understanding of the possible geochemical controls on resident chemolithotrophic microbial populations. Our goal was to analyze and compare YNP geothermal systems in terms of the free energy (Grxn) available from various exergonic oxidation/reduction (redox) reactions. Important electron donors in YNP geothermal systems were measured and include H2, H2S , S0, Fe2+, CH4, and NH4+; terminal electron acceptors of noted importance include O2, NO3-, Fe3+, , S0, SO42- and CO2. Thermodynamic modeling of aqueous chemical species was used to calculate the non-standard state free energy values for a variety of oxidation-reduction reactions potentially important for chemolithotrophic metabolism. Energetic profiles as a function of distance from spring source and temperature were calculated for a series of redox reactions in several YNP springs. Variable temperatures and reactant concentrations across several geothermal springs (pH ranges 2.5-6.8) generally did not significantly change the favorability of many of the reactions considered. These findings imply that observable changes in the distribution of microbial populations are likely linked to physical (e.g. mass transfer, temperature) and biological factors. There are, however, important comparisons to be made among exergonic reactions and presumed metabolisms of resident microbial populations. Both energetic and kinetic considerations will be necessary for understanding which oxidation-reduction reactions provide a competitive metabolic advantage to primary producers in geothermal springs.

Ackerman, G. G.; Macur, R. E.; Taylor, W. P.; Kozubal, M. A.; Korf, S.; Inskeep, W. P.

2005-12-01

213

National Geothermal Data System (USA): an Exemplar of Open Access to Data  

NASA Astrophysics Data System (ADS)

The National Geothermal Data System's (NGDS - www.geothermaldata.org) formal launch in April, 2014 will provide open access to millions of data records, sharing -relevant geoscience and longer term to land use data to propel geothermal development and production. NGDS serves information from all of the U.S. Department of Energy's sponsored development and research projects and geologic data from all 50 states, using free and open source software. This interactive online system is opening new exploration opportunities and potentially shortening project development by making data easily discoverable, accessible, and interoperable. We continue to populate our prototype functional data system with multiple data nodes and nationwide data online and available to the public. Data from state geological surveys and partners includes more than 6 million records online, including 1.72 million well headers (oil and gas, water, geothermal), 670,000 well logs, and 497,000 borehole temperatures and is growing rapidly. There are over 312 interoperable Web services and another 106 WMS (Web Map Services) registered in the system as of January, 2014. Companion projects run by Southern Methodist University and U.S. Geological Survey (USGS) are adding millions of additional data records. The DOE Geothermal Data Repository, currently hosted on OpenEI, is a system node and clearinghouse for data from hundreds of U.S. DOE-funded geothermal projects. NGDS is built on the US Geoscience Information Network (USGIN) data integration framework, which is a joint undertaking of the USGS and the Association of American State Geologists (AASG). NGDS complies with the White House Executive Order of May 2013, requiring all federal agencies to make their data holdings publicly accessible online in open source, interoperable formats with common core and extensible metadata. The National Geothermal Data System is being designed, built, deployed, and populated primarily with support from the US Department of Energy, Geothermal Technologies Office. To keep this system operational after the original implementation will require four core elements: continued serving of data and applications by providers; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges currently under consideration.

Allison, M. Lee; Richard, Stephen; Blackman, Harold; Anderson, Arlene; Patten, Kim

2014-05-01

214

Variation in sericite compositions from fracture zones within the Coso Hot Springs geothermal system  

Microsoft Academic Search

Two types of white micas are found in drillhole samples within the geothermal system at Coso Hot Springs. Low-permeability zones of the crystalline basement contain coarse-grained relict muscovite, whereas rock alteration near fracture zones at temperatures > 150°C is characterized by abundant finegrained sericite in association with secondary calcite and quartz and unaltered relict microcline. In this hydrothermal sericite there

Barbara P. Bishop; Dennis K. Bird

1987-01-01

215

36Cl/Cl ratios in geothermal systems: preliminary measurements from the Coso Field  

SciTech Connect

The {sub 36}Cl/Cl isotopic composition of chlorine in geothermal systems can be a useful diagnostic tool in characterizing hydrologic structure, in determining the origins and age of waters within the systems, and in differentiating the sources of chlorine (and other solutes) in the thermal waters. The {sub 36}Cl/Cl values for several geothermal water samples and reservoir host rock samples from the Coso, California geothermal field have been measured for these purposes. The results indicate that most of the chlorine is not derived from the dominant granitoid that host the geothermal system. If the chlorine was originally input into the Coso subsurface through meteoric recharge, that input occurred at least 1-1.25 million years ago. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources. In either case, the results indicate that most of the chlorine in the thermal waters has existed within the granitoid host rocks for no more than about 100,00-200,00 years. this residence time for the chlorine is similar to residence times suggested by other researchers for chlorine in deep groundwaters of the Mono Basin north of the Coso field.

Nimz, G.J.; Moore, J.N.; Kasameyer, P.W.

1997-07-01

216

Geothermal fluxes of alkalinity in the Narayani river system of central Nepal  

E-print Network

Geothermal fluxes of alkalinity in the Narayani river system of central Nepal Matthew J. Evans hot springs flow within the steeply incised gorges of the central Nepal Himalayan front. The spring of central Nepal, Geochem. Geophys. Geosyst., 5, Q08011, doi:10.1029/2004GC000719. G 3 G 3Geochemistry

Derry, Louis A.

217

Groundwater flow, heat and mass transport in geothermal systems of a Central Alpine Massif.  

E-print Network

Groundwater flow, heat and mass transport in geothermal systems of a Central Alpine Massif waters and natural flows in the Alpine do- main. Description of methods 7 1 Definition, use . . . . . . . . . . . . . . . . . . . . . . 11 1.4 Description of natural flows in Alpine domain

Paris-Sud XI, Université de

218

The Suitability of Conductive and Convective Geothermal Resources in New Mexico for EGS Systems  

Microsoft Academic Search

The State of New Mexico is endowed with both deep conductive and shallow convective geothermal prospects. Shallow convective resources are associated with relatively permeable, fractured crystalline plutonic, volcanic and sedimentary bedrock units. In most instances, hot springs associated with these systems are located along gaps in Paleozoic to Tertiary confining units that form hydrogeologic windows. Hydrogeologic windows are created either

M. A. Person; L. Owens; J. Hubbling; S. Kelley; J. C. Witcher; S. Lucero

2010-01-01

219

Influence of two systematic parameters on the geothermal heat pump system operation  

Microsoft Academic Search

In order to match the output capacity of a geothermal heat pump system (GHPS) with the actual load requirement, research has been carried out in finding the influence of two systematic parameters, the water flow rate inside the condenser and the compressor input frequency on the GHPS operation. Experiments are done on a small-scale GHPS at the water flow rate

L. Zhao; T. J. Zhang; Q. Zhang; G. L. Ding

2003-01-01

220

Energy and exergy analysis of a ground source (geothermal) heat pump system  

Microsoft Academic Search

Ground source heat pumps (GSHPs), often referred to as geothermal heat pumps (GHPs), offer an attractive option for heating and cooling residential and commercial buildings owing to their higher energy efficiency compared with conventional systems. GSHPs have been used for four years in the Turkish market, although they have been in use for more years in developed countries. The purpose

A. Hepbasli; O. Akdemir

2004-01-01

221

Theoretical and basic experimental analysis on load adjustment of geothermal heat pump systems  

Microsoft Academic Search

In order to match the output capacity of a geothermal heat pump system (GHPS) with the actual load requirement, research has been conducted in searching for suitable adjusting methods for the GHPS and on the subsequent effects on the working parameters of the GHPS. Firstly, several methods are compared, and it is found that the method of adjusting the compressor's

L Zhao; L. L Zhao; Q Zhang; G. L Ding

2003-01-01

222

Integrated mineralogical and fluid inclusion study of the Coso geothermal system  

SciTech Connect

Coso is one of several high-temperature geothermal systems on the margins of the Basin and Range province that is associated with recent volcanic activity. This system, which is developed entirely in fractured granitic and metamorphic rocks, consists of a well-defined thermal plume that originates in the southern part of the field and then flows upward and laterally to the north. Fluid inclusion homogenization temperatures and salinities demonstrate that cool, low salinity ground waters were present when the thermal plume was emplaced. Dilution of the thermal waters occurred above and below the plume producing strong gradients in their compositions. In response to heating and mixing, clays and carbonate minerals precipitated, sealing the fractures along the margins of the reservoir and strongly influencing its geometry. The alteration mineralogy varies systematically with depth and temperature. Based on the clay mineralogy, three zones can be recognized: the smectite zone, the illite-smectite zone, and the illite zone. The smectite zone thickens from the north to south and is characterized by smectite, kaolin, stilbite and a variety of carbonate minerals. The illite-smectite zone contains mixed-layer clays and also thickens to the south. The deepest zone (the illite zone) contains illite, chlorite, epidote, and wairakite. Quartz and calcite veins occur in all three zones. Comparison of mineral and fluid inclusion based temperatures demonstrates that cooling has occurred along the margins of the thermal system but that the interior of the system is still undergoing heating.

Lutz, S.J.; Moore, J.N. [Univ. of Utah, Salt Lake City, UT (United States); Copp, J.F. [California Energy Company, Ridgecrest, CA (United States)

1996-12-31

223

Integrated mineralogical and fluid inclusion study of the Coso geothermal systems, California  

SciTech Connect

Coso is one of several high-temperature geothermal systems on the margins of the Basin and Range province that is associated with recent volcanic activity. This system, which is developed entirely in fractured granitic and metamorphic rocks, consists of a well-defined thermal plume that originates in the southern part of the field and then flows upward and laterally to the north. Fluid inclusion homogenization temperatures and salinities demonstrate that cool, low salinity ground waters were present when the thermal plume was emplaced. Dilution of the thermal waters occurred above and below the plume producing strong gradients in their compositions. In response to heating and mixing, clays and carbonate minerals precipitated, sealing the fractures along the margins of the reservoir and strongly influencing its geometry. The alteration mineralogy varies systematically with depth and temperature. Based on the clay mineralogy, three zones can be recognized: the smectite zone, the illite-smectite zone, and the illite zone. The smectite zone thickens from the north to south and is characterized by smectite, kaolin, stilbite and a variety of carbonate minerals. The illite-smectite zone contains mixed-layer clays and also thickens to the south. The deepest zone (the illite zone) contains illite, chlorite, epidote, and wairakite. Quartz and calcite veins occur in all three zones. Comparison of mineral and fluid inclusion based temperatures demonstrates that cooling has occurred along the margins of the thermal system but that the interior of the system is still undergoing heating.

Lutz, Susan J.; Moore, Joseph N.; Copp, John F.

1996-01-24

224

Thermal Modelling of Amagmatic Heat Sources as an Exploration Tool for Hot Rock Geothermal Systems  

NASA Astrophysics Data System (ADS)

Geothermal resources in Australia are amagmatic, "Hot Rock" systems, and unrelated to active volcanism or plate margin collision. Instead, these resources are typically associated with heat from radioactive decay in high-heat-producing (HHP) granites (granites containing high concentrations of U, Th and K), coupled with thermal insulation from a thick sediment cover. A greater understanding of the ideal geological components of the Hot Rock system is needed to assist geothermal exploration and reduce risk. Existing geothermal data for Australia (borehole temperatures and heat flow determinations) are limited and collection of additional data is both time consuming and restricted to accessing wells drilled for other purposes. To aid in targeting and prioritizing areas for further study (i.e., evaluations of permeabilities and flow rates), GA has undertaken synthetic thermal modelling, constrained by available geological and geophysical datasets. 150,000 discrete numerical simulations were performed using the SHEMAT computer code. The models were designed to explore the range of geological conditions present in Australia and include variations in intrusive geometry and heat production, sediment thickness and thermal conductivity, basement heat production and basal heat flow. In order to facilitate computation and analysis, plutons were modelled as radially symmetrical cylinders and advective heat transfer was considered to be negligible. The results of the synthetic modelling indicate that significant heat can be generated by granites and trapped in geologically realistic conditions. Temperatures >160°C can be produced with heat production values as low as 2.0 ?W/m3, but these scenarios require either unusually large pluton diameters (>50 km), low sediment thermal conductivity (<1.75 W/mK), or high basal heat flow values (>0.05 W/m2). The most geologically reasonable conditions that result in temperatures >160°C, are: pluton diameters 30-40 km; heat production of 4.0-5.0 ?W/m3; a basal heat flow of 0.04 W/m2; and basin thicknesses of >3 km. Threshold values for the various parameters can be derived for higher, more economically desirable temperatures (e.g., 220°C), but will require increasingly anomalous conditions. These findings provide a framework for identifying geologically-suitable areas where favourable temperatures are most likely to occur, such as areas of coal deposits and associated low thermal conductivities, or areas of thinner crust and associated high basal heat flow. Model temperature data were fitted empirically using five variables, to produce multiple equations that predict temperature to within ± 5°C of the modelled temperatures. This set of equations was used to construct an ArcGIS tool that calculates the temperature at a specified depth, or a depth to a specified temperature, given the necessary map data layers. The appropriate data layers for Australia are being constructed using available datasets including: OZCHEM geochemistry, outcrop geology, SEEBASE™ basin thickness, and combined magnetics and gravity surveys. The ArcGIS geothermal tool will be applied iteratively with layer refinement to identify areas of Australia that warrant more detailed study.

Lescinsky, D. T.; Budd, A. R.; Champion, D. C.; Gerner, E. J.; Kirkby, A. L.

2012-12-01

225

Climate change and geothermal ecosystems: natural laboratories, sentinel systems, and future refugia.  

PubMed

Understanding and predicting how global warming affects the structure and functioning of natural ecosystems is a key challenge of the 21st century. Isolated laboratory and field experiments testing global change hypotheses have been criticized for being too small-scale and overly simplistic, whereas surveys are inferential and often confound temperature with other drivers. Research that utilizes natural thermal gradients offers a more promising approach and geothermal ecosystems in particular, which span a range of temperatures within a single biogeographic area, allow us to take the laboratory into nature rather than vice versa. By isolating temperature from other drivers, its ecological effects can be quantified without any loss of realism, and transient and equilibrial responses can be measured in the same system across scales that are not feasible using other empirical methods. Embedding manipulative experiments within geothermal gradients is an especially powerful approach, informing us to what extent small-scale experiments can predict the future behaviour of real ecosystems. Geothermal areas also act as sentinel systems by tracking responses of ecological networks to warming and helping to maintain ecosystem functioning in a changing landscape by providing sources of organisms that are preadapted to different climatic conditions. Here, we highlight the emerging use of geothermal systems in climate change research, identify novel research avenues, and assess their roles for catalysing our understanding of ecological and evolutionary responses to global warming. PMID:24729541

O'Gorman, Eoin J; Benstead, Jonathan P; Cross, Wyatt F; Friberg, Nikolai; Hood, James M; Johnson, Philip W; Sigurdsson, Bjarni D; Woodward, Guy

2014-11-01

226

Final report. Geothermal Energy Program: Information dissemination, public outreach, and technical analysis activities. April 1, 1999 to December 31, 2001. USDOE Grant No. DE-FG01-99-EE35098  

SciTech Connect

This is the final report of the accomplishments of the geothermal energy program: information dissemination, public outreach, and technical analysis activities by the project team consisting of the Geo-Heat Center, Geothermal Resources Council, Geothermal Education Office, Geothermal Energy Association, and the Washington State University Energy Program.

Lund, John W.

2002-03-22

227

The importance of methanotrophic activity in geothermal soils of Pantelleria island (Italy)  

NASA Astrophysics Data System (ADS)

Methane is a major contributor to the greenhouse effect, its atmospheric concentration being more than doubled since the XIX century. Every year 22 Tg of methane are released to the atmosphere from several natural and anthropogenic sources. Natural sources include geothermal/volcanic areas but the estimation of the total methane emission from these areas is currently not well defined since the balance between emission through degassing and microbial oxidation within the soils is not well known. Microbial oxidation in soils contributes globally for about 3-9% to the removal of methane from the atmosphere and recent studies evidenced methanotrophic activity also in soils of volcanic/geothermal areas despite their harsh environmental conditions (high temperatures, low pH and high concentrations of H2S and NH3). Methanotrophs are a diverse group of bacteria that are able to metabolize methane as their only source of carbon and energy and are found within the Alpha and Gamma classes of Proteobacteria and within the phylum Verrucomicrobia. Our purpose was to study the interaction between methanotrophic communities and the methane emitted from the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission has been previously estimated in about 2.5 t/a. Laboratory incubation experiments with soil samples from Favara Grande showed methane consumption values of up to 9500 ng g-1 dry soil per hour while soils collected outside the geothermal area consume less than 6 ng g-1 h-1. The maximum consumption was measured in the shallowest part of the soil profile (1-3 cm) and high values (>100 ng g-1 h-1) were maintained up to a depht of 15 cm. Furthermore, the highest consumption was measured at 37°C, and a still recognizable consumption (>20 ng g-1 h-1) at 80°C, with positive correlation with the methane concentration in the incubation atmosphere. These results can be considered a clear evidence of the presence of methanotrophs that were investigated by culturing and culture-independent techniques. The diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding gene, pmoA. Clone sequencing indicates the presence of Gammaproteobacteria in the soils of Favara Grande. Enrichment cultures, on a mineral medium in a CH4-enriched atmosphere, led to the isolation of different strains that were identified as Methylocistis spp., which belong to the Alphaproteobacteria. The presence of Verrucomicrobia was detected by amplification of pmoA gene using newly designed primers. Soils from Favara Grande show therefore the largest spectrum of methanotrophic microorganisms until now detected in a geothermal environment. While the presence of Verrucomicrobia in geothermal soils was predictable due to their thermophilic and acidophilic character, the presence of both Alpha and Gamma proteobacteria was unexpected. Their presence is limited to the shallowest part of the soil were temperatures are lower and is probably favored by a soil pH that is not too low (pH ~5) and their contribution to biological methane oxidation at Pantelleria is significant. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of soils in methane emissions in such environments.

D'Alessandro, Walter; Gagliano, Antonina Lisa; Quatrini, Paola; Parello, Francesco

2013-04-01

228

The Occurrence of Pyrrhotite in the Ngawha Geothermal System, New Zealand  

SciTech Connect

The Ngawha geothermal system is low in all sulfide minerals, but in comparison to systems in the Taupo Volcanic Zone it contains more widely distributed pyrrhotite which is currently depositing, mainly in fractures. This reflects the high proportion of vapor in the Ngawha system. Pyrrhotite is most common in the upper part of the reservoir and lower part of the aquitard. The Ngawha pyrrhotite is of monoclinic and monoclinic + hexagonal structure.

Cox, M.E.; Browne, P.R.L.

1995-01-01

229

Experimentally determined rock-fluid interactions applicable to a natural hot dry rock geothermal system  

SciTech Connect

The Los Alamos Scientific Laboratory is pursuing laboratory and field experiments in the development of the Hot Dry Rock concept of geothermal energy. The field program consists of experiments in a hydraulically fractured region of low permeability in which hot rock is intercepted by two wellbores. These experiments are designed to test reservoir engineering parameters such as: heat extraction rates, water loss rates, flow characteristics including impedance and buoyancy, seismic activity and fluid chemistry. Laboratory experiments have been designed to provide information on the mineral reactivity which may be encountered in the field program. Two experimental circulation systems have been built to study the rates of dissolution and alteration in dynamic flow. Solubility studies have been done in agitated systems. To date, pure minerals, samples of the granodiorite from the actual reservoir and Tijeras Canyon granite have been reacted with distilled water and various solutions of NaCl, NaOH, and Na/sub 2/CO/sub 3/. The results of these experimental systems are compared to observations made in field experiments done in a hot dry rock reservoir at a depth of approximately 3 km with initial rock temperatures of 150 to 200/sup 0/C.

Charles, R.W.; Holley, C.E. Jr.; Tester, J.W.; Blatz, L.A.; Grigsby, C.O.

1980-02-01

230

Geochemistry of sericite and chlorite in well 14-2 Roosevelt Hot Springs geothermal system and in mineralized hydrothermal systems  

SciTech Connect

Chemical compositions of chlorite and sericite from one production well in the Roosevelt geothermal system have been determined by electron probe methods and compared with compositions of chlorite and sericite from porphyry copper deposits. Modern system sericite and chlorite occur over a depth interval of 2 km and a temperature interval of 250/sup 0/C.

Ballantyne, J.M.

1980-06-01

231

Geochemistry of sericite and chlorite in well 14-2 Roosevelt Hot Springs geothermal system and in mineralized hydrothermal systems  

Microsoft Academic Search

Chemical compositions of chlorite and sericite from one production well in the Roosevelt geothermal system have been determined by electron probe methods and compared with compositions of chlorite and sericite from porphyry copper deposits. Modern system sericite and chlorite occur over a depth interval of 2 km and a temperature interval of 250°C.

Ballantyne

1980-01-01

232

Development of Models to Simulate Tracer Tests for Characterization of Enhanced Geothermal Systems  

SciTech Connect

A recent report found that power and heat produced from enhanced (or engineered) geothermal systems (EGSs) could have a major impact on the U.S energy production capability while having a minimal impact on the environment. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distribution, permeability/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the surface area available for heat transfer in EGS is necessary for the design and commercial development of the geothermal energy of a potential EGS site. The goal of this project is to provide integrated tracer and tracer interpretation tools to facilitate this characterization. This project was initially focused on tracer development with the application of perfluorinated tracer (PFT) compounds, non-reactive tracers used in numerous applications from atmospheric transport to underground leak detection, to geothermal systems, and evaluation of encapsulated PFTs that would release tracers at targeted reservoir temperatures. After the 2011 midyear review and subsequent discussions with the U.S. Department of Energy Geothermal Technology Program (GTP), emphasis was shifted to interpretive tool development, testing, and validation. Subsurface modeling capabilities are an important component of this project for both the design of suitable tracers and the interpretation of data from in situ tracer tests, be they single- or multi-well tests. The purpose of this report is to describe the results of the tracer and model development for simulating and conducting tracer tests for characterizing EGS parameters.

Williams, Mark D.; Reimus, Paul; Vermeul, Vincent R.; Rose, Peter; Dean, Cynthia A.; Watson, Tom B.; Newell, D.; Leecaster, Kevin; Brauser, Eric

2013-05-01

233

Evaluation of noise associated with geothermal-development activities. Final report, July 31, 1979-April 30, 1982  

SciTech Connect

This report was prepared for the purpose of ascertaining the current state of noise generation, suppression, and mitigation techniques associated with geothermal development. A description of the geothermal drilling process is included as well as an overview of geothermal development activities in the United States. Noise sources at the well site, along geothermal pipelines, and at the power plants are considered. All data presented are measured values by workers in the field and by Marshall Long/Acoustics. One particular well site was monitored for a period of 55 continuous days, and includes all sources of noise from the time that the drilling rig was brought in until the time that it was moved off site. A complete log of events associated with the drilling process is correlated with the noise measurements including production testing of the completed well. Data are also presented which compare measured values of geothermal noise with federal, state, county, and local standards. A section on control of geothermal noise is also given. Volume I of this document presents summary information.

Long, M.; Stern, R.

1982-01-01

234

GEOGRAPHIC INFORMATION SYSTEMS IN MANAGING OF TERRITORIAL RESOURCES: AN EXAMPLE FOR THE SABATINI GEOTHERMAL SYSTEM (CENTRAL ITALY)  

NASA Astrophysics Data System (ADS)

Geographic Information System (GIS) is very important tool in managing the interdisciplinary researches and territorial resources. GIS integrates data for capturing, managing, analyzing, and displaying all forms of geographically referenced information. They can represent a scientific and social benefit. Here we present an application of GIS to a potentially exploitable geothermal area. The geothermal resource can be used either indirectly or directly. In the first case electricity is produced from high enthalpy systems. In second case heating and cooling systems are obtained from medium or low enthalpy systems. Italian geothermal resources employment is still poorly developed in direct use sector, despite the great geothermal potentials suitable for this purpuse. Often this limited application is due mainly to a inadequate territory knowledge and sometimes by difficulties in obtaining required information. In this case the creation of a geo-database can be extremely helpful. The studied area is located in Central Italy, just north of Rome, and comprise the western part of the Sabatini Volcanic District, Tolfa Mountains, extending up to Civitavecchia. Exploration surveys investigated this area during 70’s-90’s for geothermal purpose, but the area still results unexploited. The presence of thermal waters and of anomalous heat flow, together with demographical growing of the last years, make this site a suitable location for direct applications of the geothermal resource. Previews work and new data about geological, structural, hydrogeological, geochemical features have been processed to be recorded in a geo-database . Further, social data about demographical trend and available scientific record concerning the studied area fulfill the database. The majority of available geological information date back to early 90’s; an important part of the work consisted in the digitalization and updating of pre-existent data. The final product is a WEB-GIS that can facilitate diffusion and consultation of geographically referenced data, which can be easily managed by public and private infrastructures, research institutes and universities, allowing a better development of the territorial resources.

Procesi, M.; Cinti, D.; Poncia, P.; de Rita, D.

2009-12-01

235

Strategic optimization of large-scale vertical closed-loop shallow geothermal systems  

NASA Astrophysics Data System (ADS)

Vertical closed-loop geothermal systems or ground source heat pump (GSHP) systems with multiple vertical borehole heat exchangers (BHEs) are attractive technologies that provide heating and cooling to large facilities such as hotels, schools, big office buildings or district heating systems. Currently, the worldwide number of installed systems shows a recurrent increase. By running arrays of multiple BHEs, the energy demand of a given facility is fulfilled by exchanging heat with the ground. Due to practical and technical reasons, square arrays of the BHEs are commonly used and the total energy extraction from the subsurface is accomplished by an equal operation of each BHE. Moreover, standard designing practices disregard the presence of groundwater flow. We present a simulation-optimization approach that is able to regulate the individual operation of multiple BHEs, depending on the given hydro-geothermal conditions. The developed approach optimizes the overall performance of the geothermal system while mitigating the environmental impact. As an example, a synthetic case with a geothermal system using 25 BHEs for supplying a seasonal heating energy demand is defined. The optimization approach is evaluated for finding optimal energy extractions for 15 scenarios with different specific constant groundwater flow velocities. Ground temperature development is simulated using the optimal energy extractions and contrasted against standard application. It is demonstrated that optimized systems always level the ground temperature distribution and generate smaller subsurface temperature changes than non-optimized ones. Mean underground temperature changes within the studied BHE field are between 13% and 24% smaller when the optimized system is used. By applying the optimized energy extraction patterns, the temperature of the heat carrier fluid in the BHE, which controls the overall performance of the system, can also be raised by more than 1 °C.

Hecht-Méndez, J.; de Paly, M.; Beck, M.; Blum, P.; Bayer, P.

2012-04-01

236

Exergy analysis of the performance of low-temperature district heating system with geothermal heat pump  

NASA Astrophysics Data System (ADS)

Exergy analysis of low temperature geothermal heat plant with compressor and absorption heat pump was carried out. In these two concepts heat pumps are using geothermal water at 19.5 oC with spontaneous outflow 24 m3/h as a heat source. The research compares exergy efficiency and exergy destruction of considered systems and its components as well. For the purpose of analysis, the heating system was divided into five components: geothermal heat exchanger, heat pump, heat distribution, heat exchanger and electricity production and transportation. For considered systems the primary exergy consumption from renewable and non-renewable sources was estimated. The analysis was carried out for heat network temperature at 50/40 oC, and the quality regulation was assumed. The results of exergy analysis of the system with electrical and absorption heat pump show that exergy destruction during the whole heating season is lower for the system with electrical heat pump. The exergy efficiencies of total system are 12.8% and 11.2% for the system with electrical heat pump and absorption heat pump, respectively.

Sekret, Robert; Nitkiewicz, Anna

2014-03-01

237

Modeling of thermodynamic and chemical changes in low-temperature geothermal systems  

SciTech Connect

A method was developed to incorporate the transport of several chemical components into a model of the transport of fluid mass and heat within a geothermal system. It was demonstrated that the use of coupled hydrological, thermal and chemical data allows for the determination of field porosities, amounts and regions of cool recharge into the system as well as field permeabilities and the hot reservoir volume. With the additional information a reliable prediction of the long-term cooling rate can be made.

Spencer, A.L.

1986-12-01

238

Geothermal district heating and cooling system for the city of Calistoga, California  

SciTech Connect

Calistoga has long been known for having moderate (270/sup 0/F maximum) hydrothermal deposits. The economic feasibility of a geothermal heating and cooling district for a portion of the downtown commercial area and city-owned building was studied. Descriptions of existing and proposed systems for each building in the block are presented. Heating and cooling loads for each building, retrofit costs, detailed cost estimates, system schematics, and energy consumption data for each building are included. (MHR)

Frederick, J.

1982-01-01

239

The Pantelleria caldera geothermal system: Data from the hydrothermal minerals  

NASA Astrophysics Data System (ADS)

This paper proposes, on the basis of petrographic and mineralogic data on cutting and cores from two deep wells ("Pantelleria 1" and "Pantelleria 2"), the first model of the active hydrothermal system of the island of Pantelleria. Phyllosilicates were studied in detail because they are considered key minerals in the identification of hydrothermal processes. The results of these studies emphasize differences between the intracaldera and pericaldera areas of the island. Within the 45 ka caldera there is a high-temperature (240-260 °C at 600-800 m depth) active hydrothermal system with five zones of characteristic alteration minerals with increasing depth. Rocks are unaltered to a depth of 200 m, contain smectite and mixed-layer chlorite-smectite (C/S) between 200 and 380 m, chlorite, illite, chalcedony and quartz from 380 to 500 m, albite, adularia and saponite from 500 to 680 m, mixed-layer biotite-vermiculite from 680 m to the depth drilled (1100). Outside the caldera, but near the rim, a low-temperature and low-permeability (< 140 °C) hydrothermal system is characterized by smectite, dolomite and ankerite at depths of 390 to 650 m, chlorite and calcite at 650-900 m, and mixed layers of chlorite-smectite, illite-smectite and iron carbonates (ankerite, siderite) from 900 m of the well at 1203 m. The superimposition of hydrothermal mineral assemblages is evidence for cooling in the hydrothermal system both inside and outside the caldera. We propose that a high-temperature hydrothermal system developed inside the caldera. In an early stage in the area surrounding the subvolcanic body, biotite isograd is reached and an alkali-metasomatism zone develops inside the body itself. This phase may also account for the development of a chlorite-albite-adularia zone extending to 400 m. A cooling phase (nearly 50 °C) followed, resulting in the substitution of biotite by mixed-layer biotite-vermiculite and by the crystallization of Fe-rich saponite instead of chlorite, within the currently active reservoir. A cooling phase has also been identified in the well outside the caldera.

Fulignati, Paolo; Malfitano, Giuseppe; Sbrana, Alessandro

1997-02-01

240

Geophysical logging case history of the Raft River geothermal system, Idaho  

SciTech Connect

Drilling to evaluate the geothermal resource in the Raft River Valley began in 1974 and resulted in the discovery of a geothermal reservoir at a depth of approximately 1523 m (500 ft). Several organizations and companies have been involved in the geophysical logging program. There is no comprehensive report on the geophysical logging, nor has there been a complete interpretation. The objectives of this study are to make an integrated interpretation of the available data and compile a case history. Emphasis has been on developing a simple interpretation scheme from a minimum of data sets. The Raft River geothermal system occurs in the Raft River Valley, which is a portion of the Basin and Range geomorphic province located in south central Idaho, south of the Snake River Plain. The valley is a late Cenozoic structural downwarp bounded by faults on the west, south, and east. The downwarp is filled with Tertiary and Paleozoic sediments, metasediments, and volcanics that overlie Precambrian rocks. The variety of rock types, the presence of alteration products, and the variability of fracturing make reliable interpretations difficult. However, the cross plotting of various parameters has allowed a determination of rock types and an analysis of the degree of alteration and the density of fractures. Thus, one can determine the relevant data necessary to assess a geothermal reservoir in similar rock types and use cross plots to potentially define the producing zones.

Applegate, J.K.; Moens, T.A.

1980-04-01

241

Advanced Horizontal Well Recirculation Systems for Geothermal Energy Recovery in Sedimentary Formations  

SciTech Connect

There is increased recognition that geothermal energy resources are more widespread than previously thought, with potential for providing a significant amount of sustainable clean energy worldwide. Recent advances in drilling, completion, and production technology from the oil and gas industry can now be applied to unlock vast new geothermal resources, with some estimates for potential electricity generation from geothermal energy now on the order of 2 million megawatts. Terralog USA, in collaboration with the University of California, Irvine (UCI), are currently investigating advanced design concepts for paired horizontal well recirculation systems, optimally configured for geothermal energy recovery in permeable sedimentary and crystalline formations of varying structure and material properties. This two-year research project, funded by the US Department of Energy, includes combined efforts for: 1) Resource characterization; 2) Small and large scale laboratory investigations; 3) Numerical simulation at both the laboratory and field scale; and 4) Engineering feasibility studies and economic evaluations. The research project is currently in its early stages. This paper summarizes our technical approach and preliminary findings related to potential resources, small-scale laboratory simulation, and supporting numerical simulation efforts.

Mike Bruno; Russell L. Detwiler; Kang Lao; Vahid Serajian; Jean Elkhoury; Julia Diessl; Nicky White

2012-09-30

242

Gas chemistry, boiling and phase segregation in a geothermal system, Hellisheidi, Iceland  

NASA Astrophysics Data System (ADS)

The geochemistry of aquifer fluids of the Hellisheidi geothermal system, southwest Iceland, was studied. Based on samples of vapor and liquid from well discharge fluids, the aquifer fluid compositions at the depth of the geothermal system were reconstructed taking into account the highly variable degree of excess well discharge enthalpy, where the enthalpy of the discharge is significantly higher than that of vapor-saturated liquid at the measured aquifer temperature. Decreasing concentrations of non-volatile components such as Si in the total well discharge suggest that the main cause of elevated discharge enthalpies is liquid-vapor phase segregation, i.e. the retention of liquid in the aquifer rock due to its adhesion onto mineral surfaces. Moreover, the slightly lower than equilibrium calculated concentrations of H2 and H2S in some of the hottest and highest-enthalpy wells is considered to be caused by conductive heat transfer from the rocks to the fluids. Alternatively, the cause may lie in the selection of the phase segregation conditions. The calculated concentrations of volatile species in the aquifer fluid are very sensitive to the assumed phase segregation conditions while non-volatiles are not greatly affected by this model parameter. In general, the level of uncertainty does not contradict previous findings of a close approach to fluid-mineral equilibrium at aquifer temperatures above 250 °C. The CO2 concentrations were observed to fall below equilibrium with respect to the most likely mineral buffers, suggesting a possible source control. Elevated H2 concentrations indicate a small equilibrium vapor fraction in aquifer fluids (?0.2% by mass or ?3% by volume). Previous conceptual models of the Hengill volcanic area (e.g. Bödvarsson et al., 1990) have implied a central magmatic heat source underlying the Hengill central volcano. Instead, a new conceptual model of the Hellisheidi system is proposed that features two main regions of fluid upflow heated by a complex of dikes and sills associated with an eruptive fissure active during the Holocene.

Scott, Samuel; Gunnarsson, Ingvi; Arnórsson, Stefán; Stefánsson, Andri

2014-01-01

243

Development of an Enhanced Two-Phase Production System at the Geysers Geothermal Field  

SciTech Connect

A method was developed to enhance geothermal steam production from two-phase wells at THE Geysers Geothermal Field. The beneficial result was increased geothermal production that was easily and economically delivered to the power plant.

Steven Enedy

2001-12-14

244

Fluid-rock interactions in CO2-saturated, granite-hosted geothermal systems: Implications for natural and engineered systems from geochemical experiments and models  

NASA Astrophysics Data System (ADS)

Hydrothermal experiments were conducted and geochemical models constructed to evaluate the geochemical and mineralogical response of fractured granite and granite + epidote in contact with thermal water, with and without supercritical CO2, at 250 °C and 25-45 MPa. Illite ± smectite ± zeolite(?) precipitate as secondary minerals at the expense of K-feldspar, oligoclase, and epidote. Illite precipitates in experiments reacting granite and granite + epidote with water; metastable smectite forms in the experiments injected with supercritical CO2. Waters are supersaturated with respect to quartz and saturated with respect to chalcedony in CO2-charged experiments, but neither mineral formed. Carbonate formation is predicted for experiments injected with supercritical CO2, but carbonate only formed during cooling and degassing of the granite + epidote + CO2 experiment. Experimental results provide insight into the buffering capacity of granites as well as the drivers of clay formation. Metastable smectite in the experiments is attributed to high water-rock ratios, high silica activities, and high CO2 and magnesium-iron concentrations. Smectite precipitation in supercritical CO2-bearing geothermal systems may affect reservoir permeability. Silicate formation may create or thicken caps within or on the edges of geothermal reservoirs. Carbonate formation, as desired for carbon sequestration projects coinciding with geothermal systems, may require extended periods of time; cooling and degassing of CO2-saturated waters leads to carbonate precipitation, potentially plugging near-surface production pathways.

Lo Ré, Caroline; Kaszuba, John P.; Moore, Joseph N.; McPherson, Brian J.

2014-09-01

245

Critiquing ';pore connectivity' as basis for in situ flow in geothermal systems  

NASA Astrophysics Data System (ADS)

Geothermal system in situ flow systematics derived from detailed examination of grain-scale structures, fabrics, mineral alteration, and pore connectivity may be extremely misleading if/when extrapolated to reservoir-scale flow structure. In oil/gas field clastic reservoir operations, it is standard to assume that small scale studies of flow fabric - notably the Kozeny-Carman and Archie's Law treatments at the grain-scale and well-log/well-bore sampling of formations/reservoirs at the cm-m scale - are adequate to define the reservoir-scale flow properties. In the case of clastic reservoirs, however, a wide range of reservoir-scale data wholly discredits this extrapolation: Well-log data show that grain-scale fracture density fluctuation power scales inversely with spatial frequency k, S(k) ~ 1/k^?, 1.0 < ? < 1.2, 1cycle/km < k < 1cycle/cm; the scaling is a ';universal' feature of well-logs (neutron porosity, sonic velocity, chemical abundance, mass density, resistivity, in many forms of clastic rock and instances of shale bodies, for both horizontal and vertical wells). Grain-scale fracture density correlates with in situ porosity; spatial fluctuations of porosity ? in well-core correlate with spatial fluctuations in the logarithm of well-core permeability, ?? ~ ?log(?) with typical correlation coefficient ~ 85%; a similar relation is observed in consolidating sediments/clays, indicating a generic coupling between fluid pressure and solid deformation at pore sites. In situ macroscopic flow systems are lognormally distributed according to ? ~ ?0 exp(?(?-?0)), ? >>1 an empirical parameter for degree of in situ fracture connectivity; the lognormal distribution applies to well-productivities in US oil fields and NZ geothermal fields, ';frack productivity' in oil/gas shale body reservoirs, ore grade distributions, and trace element abundances. Although presently available evidence for these properties in geothermal reservoirs is limited, there are indications that geothermal system flow essentially obeys the same ';universal' in situ flow rules as does clastic rock: Well-log data from Los Azufres, MX, show power-law scaling S(k) ~ 1/k^?, 1.2 < ? < 1.4, for spatial frequency range 2cycles/km to 0.5cycle/m; higher ?-values are likely due to the relatively fresh nature of geothermal systems; Well-core at Bulalo (PH) and Ohaaki (NZ) show statistically significant spatial correlation, ?? ~ ?log(?) Well productivity at Ohaaki/Ngawha (NZ) and in geothermal systems elsewhere are lognormally distributed; K/Th/U abundances lognormally distributed in Los Azufres well-logs We therefore caution that small-scale evidence for in situ flow fabric in geothermal systems that is interpreted in terms of ';pore connectivity' may in fact not reflect how small-scale chemical processes are integrated into a large-scale geothermal flow structure. Rather such small scale studies should (perhaps) be considered in term of the above flow rules. These flow rules are easily incorporated into standard flow simulation codes, in particular the OPM = Open Porous Media open-source industry-standard flow code. Geochemical transport data relevant to geothermal systems can thus be expected to be well modeled by OPM or equivalent (e.g., INL/LANL) codes.

Kenedi, C. L.; Leary, P.; Malin, P.

2013-12-01

246

Energy Returned On Investment of Engineered Geothermal Systems Annual Report FY2011  

SciTech Connect

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. For geothermal electric power generation, EROI is determined by the electricity delivered to the consumer compared to the energy consumed to construct, operate, and decommission the facility. Critical factors in determining the EROI of Engineered Geothermal Systems (EGS) are examined in this work. These include the input energy embodied into the system. The embodied energy includes the energy contained in the materials, as well as, that consumed in each stage of manufacturing from mining the raw materials to assembling the finished plant. Also critical are the system boundaries and value of the energy - heat is not as valuable as electrical energy.

Mansure, A.J.

2011-12-31

247

Role of Fluid Pressure in the Production Behavior of Enhanced Geothermal Systems with CO2 as Working Fluid  

E-print Network

Simulation of Injectivity Effects of Mineral Scaling and Clay Swelling in a Fractured GeothermalSimulation of Mineral Precipitation and Dissolution in the 5-km Deep Enhanced Geothermalgeothermal systems (EGS), heat transmission, CO 2 storage, numerical simulation.

Pruess, Karsten

2008-01-01

248

Federal Geothermal Research Program Update, FY 2000  

SciTech Connect

The Department of Energy's Geothermal Program serves two broad purposes: 1) to assist industry in overcoming near-term barriers by conducting cost-shared research and field verification that allows geothermal energy to compete in today's aggressive energy markets; and 2) to undertake fundamental research with potentially large economic payoffs. The four categories of work used to distinguish the research activities of the Geothermal Program during FY 2000 reflect the main components of real-world geothermal projects. These categories form the main sections of the project descriptions in this Research Update. Exploration Technology research focuses on developing instruments and techniques to discover hidden hydrothermal systems and to explore the deep portions of known systems. Research in geophysical and geochemical methods is expected to yield increased knowledge of hidden geothermal systems. Reservoir Technology research combines laboratory and analytical investigations with equipment development and field testing to establish practical tools for resource development and management for both hydrothermal reservoirs and enhanced geothermal systems. Research in various reservoir analysis techniques is generating a wide range of information that facilitates development of improved reservoir management tools. Drilling Technology focuses on developing improved, economic drilling and completion technology for geothermal wells. Ongoing research to avert lost circulation episodes in geothermal drilling is yielding positive results. Conversion Technology research focuses on reducing costs and improving binary conversion cycle efficiency, to permit greater use of the more abundant moderate-temperature geothermal resource, and on the development of materials that will improve the operating characteristics of many types of geothermal energy equipment. Increased output and improved performance of binary cycles will result from investigations in heat cycle research.

Renner, Joel Lawrence

2001-08-01

249

Modeling Hydro-Mechanical Reservoir Stimulation for Geothermal Systems  

NASA Astrophysics Data System (ADS)

Several geothermal EGS projects are under development worldwide. As such the Coso project in the US and the Soultz project in Europe intend to produce electricity from circulating fluids in hot fracture rock. Improvement of the reservoir conditions by hydraulic stimulation and minimizing the seismic risk represents now a primary challenge to enable economic operation and future extension. In this context, the new HEX-S code has been developed to simulate the transient hydro-mechanical response of the rock matrix to massive hydraulic injections. The present paper describes the modeling results of the Soultz stimulation from 2003 and 2004 and the analysis of the situation in Coso. Maximum flow rates of 60 l/s have been used, triggering above 30'000 microseismic events. The transient numerical simulation intends to obtain a match of both, the microseismic and the hydraulic behavior. Different model calculations demonstrate the capabilities of our new approach. It is noteworthy that the modeling became possible only due to the excellent data quality at the Soultz project. The results demonstrate that simulations based on solid physical ground can reveal the complex reservoir behavior during hydraulic stimulation. The use of HEX-S also provides perspectives for future developments such as design calculations that enable optimizing cost-intensive hydraulic stimulations before hand.

Kohl, T.; Mégel, T.

2005-12-01

250

The Domuyo volcanic system: An enormous geothermal resource in Argentine Patagonia  

NASA Astrophysics Data System (ADS)

A geochemical survey of the main thermal waters discharging in the southwestern part of the Domuyo volcanic complex (Argentina), where the latest volcanic activity dates to 0.11 Ma, has highlighted the extraordinarily high heat loss from this remote site in Patagonia. The thermal water discharges are mostly Na-Cl in composition and have TDS values up to 3.78 g L- 1 (El Humazo). A simple hydrogeochemical approach shows that 1,100 to 1,300 kg s- 1 of boiling waters, which have been affected by shallow steam separation, flow into the main drainage of the area (Rio Varvarco). A dramatic increase of the most conservative species such as Na, Cl and Li from the Rio Varvarco from upstream to downstream was observed and related solely to the contribution of hydrothermal fluids. The equilibrium temperatures of the discharging thermal fluids, calculated on the basis of the Na-K-Mg geothermometer, are between 190 °C and 230 °C. If we refer to a liquid originally at 220 °C (enthalpy = 944 J g- 1), the thermal energy release can be estimated as high as 1.1 ± 0.2 GW, a value that is much higher than the natural release of heat in other important geothermal fields worldwide, e.g., Mutnovsky (Russia), Wairakei (New Zealand) and Lassen Peak (USA). This value is the second highest measured advective heat flux from any hydrothermal system on Earth after Yellowstone.

Chiodini, Giovanni; Liccioli, Caterina; Vaselli, Orlando; Calabrese, Sergio; Tassi, Franco; Caliro, Stefano; Caselli, Alberto; Agusto, Mariano; D'Alessandro, Walter

2014-03-01

251

Joint Geophysical Characterization of Geothermal System in Menengai, Kenya Using Magnetotelluric and Gravity  

NASA Astrophysics Data System (ADS)

Geothermal exploration typically focuses on the identification of the heat source and defining the plumbing system that allows fluid flow at depths of 1-5 km where production of geothermal energy is feasible. The faults and fracture systems that make up the plumbing systems for hydrothermal fluids are often offset from their source and may be entirely hidden beneath basin fill or volcanic flows. Thus, a variety of different geophysical methods are used to detect the fracture zones and heat sources, including electrical, electromagnetic, seismic, and potential field techniques, each not giving a unique interpretation. Therefore a careful qualitative and quantitative joint analysis of these data based on common/shared geology may improve the overall understanding of the study area. To determine the extent of geothermal system as the target for development around Menengai volcano in the southern region of the Kenya rift valley, Magnetotelluric (MT) and gravity data were analysed. Subsurface conductivity and density distribution were used to infer the possible geological structures that relate to permeability and the heat source. Density gradient in the NW and NE north of the Menengai caldera defines the rift faults. A low resistivity layer at about 500 m and 1 km is interpreted as alteration clay minerals and overlays a relatively resistive zone. A low resistivity region at a depth of about 5-6 km is inferred to be a cooling magmatic body.

Wamalwa, A. M.; Serpa, L. F.

2010-12-01

252

Applications of fractured continuum model to enhanced geothermal system heat extraction problems.  

PubMed

This paper describes the applications of the fractured continuum model to the different enhanced geothermal systems reservoir conditions. The capability of the fractured continuum model to generate fracture characteristics expected in enhanced geothermal systems reservoir environments are demonstrated for single and multiple sets of fractures. Fracture characteristics are defined by fracture strike, dip, spacing, and aperture. The paper demonstrates how the fractured continuum model can be extended to represent continuous fractured features, such as long fractures, and the conditions in which the fracture density varies within the different depth intervals. Simulations of heat transport using different fracture settings were compared with regard to their heat extraction effectiveness. The best heat extraction was obtained in the case when fractures were horizontal. A conventional heat extraction scheme with vertical wells was compared to an alternative scheme with horizontal wells. The heat extraction with the horizontal wells was significantly better than with the vertical wells when the injector was at the bottom. PMID:24600552

Kalinina, Elena A; Klise, Katherine A; McKenna, Sean A; Hadgu, Teklu; Lowry, Thomas S

2014-01-01

253

A re-evaluation of the Moyuta geothermal system, Southern Guatemala  

Microsoft Academic Search

Chemical and isotopic data from four fumarole sites combined with prefeasibility assessments obtained in the 1970s have resulted in a re-evaluation of the Moyuta geothermal system. Moyuta consists of an east-west trending complex of Quaternary andesite\\/dacite domes and flows cut by north-trending faults. Areas of fumaroles, acid springs, and bicarbonate-rich thermal springs flank the north and south sides of the

F. Goff; A. Adams; P. E. Trujillo; D. Counce; C. Janik; L. Fahlquist; A. Roldan; M. Revolorio

1991-01-01

254

A transient model of the geothermal system of the Long Valley Caldera, California  

Microsoft Academic Search

The present-day geothermal system underlying the southern one third of the Long Valley caldera is discussed, based on interpretation of the complex shapes of temperature-depth curves and the correlation of this interpretation with hydrologic and geologic data. The temperature-depth curves are interpreted using a simple analytical model for transient flow of hot water in a confined aquifer. The results give

David D. Blackwell

1985-01-01

255

Origin of COâ in the Salton Sea geothermal system, Southeastern California, U. S. A  

Microsoft Academic Search

The now-abandoned Imperial carbon dioxide gas field produced in excess of 18,400,000 cu m of COâ gas between 1934 and 1954. At least 54 producing wells tapped one or more sandstone reservoirs at depths of 150 to 210 m and static pressures up to 17-1\\/2 kg\\/sq cm. The COâ field is part of the Salton Sea geothermal system, from which

L. J. P. Muffler; D. E. White

1968-01-01

256

Geothermal systems of the Mono Basin-Long Valley region, eastern California and western Nevada  

SciTech Connect

The region that includes Mono Basin, Long Valley, the Bridgeport-Bodie Hills area, and Aurora, in eastern California and western Nevada was studied to determine the possible causes and interactions of the geothermal anomalies in the Mono Basin-Long Valley region as a whole. A special goal of the study was to locate possible shallow bodies of magma and to determine their influence on the hydrothermal systems in the region. (ACR)

Higgins, C.T.; Flynn, T.; Chapman, R.H.; Trexler, D.T.; Chase, G.R.; Bacon, C.F.; Ghusn, G. Jr.

1985-01-01

257

Underground Mine Water for Heating and Cooling using Geothermal Heat Pump Systems  

Microsoft Academic Search

In many regions of the world, flooded mines are a potentially cost-effective option for heating and cooling using geothermal\\u000a heat pump systems. For example, a single coal seam in Pennsylvania, West Virginia, and Ohio contains 5.1 x 1012 L of water. The growing volume of water discharging from this one coal seam totals 380,000 L\\/min, which could theoretically\\u000a heat and

George R. Watzlaf; Terry E. Ackman

2006-01-01

258

COTHERM: Numerical modeling of the deep roots of volcanic geothermal systems  

NASA Astrophysics Data System (ADS)

We report numerical simulations of the transient evolution of fluid flow and heat transport in high-enthalpy geothermal systems around cooling intrusions, including the deep, 'supercritical' roots. We employ the CSMP++ fluid flow and heat transport code, and analyze the temperature, pressure, phase state distribution etc. during the whole lifetime of a geothermal system. Such simulations are of high relevance to projects like the Iceland Deep Drilling Project, which aim to dramatically improve the economics of geothermal power production by tapping such 'supercritical' reservoirs. We study the effects of the depth of the intrusion, the system-scale permeability and the permeability change across the brittle-ductile transition. While previous studies have commonly adopted a temperature-dependent parameterization, with permeability decreasing in a log-linear fashion at temperatures above 360° C, this study explores a variety of different potential temperature dependencies of permeability and their effects on model results. These effects are large and namely affect the thickness of the conductive boundary layer, which impacts the overall rate of cooling of the intrusion.

Scott, Samuel; Weis, Philipp; Driesner, Thomas

2014-05-01

259

A hydrogeological and geochemical model of the high-temperature geothermal system of Amatitlan, Guatemala  

SciTech Connect

Geological, geophysical and geochemical data from deep and shallow wells indicate the presence of a large geothermal system fed by upflow beneath Volcan de Pacaya, with source temperatures {ge} 330{degrees}C and chloride contents on the order of 2,500 mg/l. A considerable contribution of magmatic water is suggested by chemical and isotopic data, provided that water-rock interactions have substantially neutralized the acidity of the magmatic component. The areal extent of the upflow zone is unknown, and can only be delimited by further drilling to the south and southeast of deep well AMF-2, which encounters the two-phase upflow zone. Outflow is directed to the north, towards Lago de Amatitlan. The outflow path is long (more than 7 km), and lateral cooling occurs both via conduction and dilution with cool groundwater. Vertical cooling is also indicated by temperature reversals of up to 60{degrees}C beneath the outflow tongue, attributed to a regional underflow of cool groundwater. Outflow paths do not appear to be controlled by geologic structures or aquifers; instead, the hot water appears to {open_quotes}float{close_quotes} on top of the gently sloping unconfined groundwater table. These aspects of the geothermal system were used to develop the numerical model of the Amatitlan geothermal system, which is the subject of a separate paper.

Lima, E.; Fujino, T. [West Japan Engineering Consultants, Inc., Fukuoka (Japan); McNitt, J.R.; Klein, C.W. [GeothermEx, Inc., Richmond, CA (United States)] [and others

1996-12-31

260

Simulation of water-rock interaction in the Yellowstone geothermal system using TOUGHREACT  

SciTech Connect

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to simulate the chemical and hydrological effects of water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to simulate the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Dobson, Patrick F.; Salah, Sonia; Spycher, Nicolas; Sonnenthal, Eric L.

2003-04-28

261

Simulation of water-rock interaction in the yellowstone geothermal system using TOUGHREACT  

SciTech Connect

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to accurately simulate water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to determine if TOUGHREACT could accurately predict the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Dobson, P.F.; Salah, S.; Spycher, N.; Sonnenthal, E.

2003-04-28

262

SIMULATION OF WATER-ROCK INTERACTION IN THE YELLOWSTONE GEOTHERMAL SYSTEM USING TOUGHREACT  

E-print Network

The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to simulate the chemical and hydrological effects of water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8°C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to simulate the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Patrick F. Dobson; Sonia Salah; Nicolas Spycher; Eric L. Sonnenthal

263

Recent drilling activities at the earth power resources Tuscarora geothermal power project's hot sulphur springs lease area.  

SciTech Connect

Earth Power Resources, Inc. recently completed a combined rotary/core hole to a depth of 3,813 feet at it's Hot Sulphur Springs Tuscarora Geothermal Power Project Lease Area located 70-miles north of Elko, Nevada. Previous geothermal exploration data were combined with geologic mapping and newly acquired seismic-reflection data to identify a northerly tending horst-graben structure approximately 2,000 feet wide by at least 6,000 feet long with up to 1,700 feet of vertical offset. The well (HSS-2) was successfully drilled through a shallow thick sequence of altered Tertiary Volcanic where previous exploration wells had severe hole-caving problems. The ''tight-hole'' drilling problems were reduced using drilling fluids consisting of Polymer-based mud mixed with 2% Potassium Chloride (KCl) to reduce Smectite-type clay swelling problems. Core from the 330 F fractured geothermal reservoir system at depths of 2,950 feet indicated 30% Smectite type clays existed in a fault-gouge zone where total loss of circulation occurred during coring. Smectite-type clays are not typically expected at temperatures above 300 F. The fracture zone at 2,950 feet exhibited a skin-damage during injection testing suggesting that the drilling fluids may have caused clay swelling and subsequent geothermal reservoir formation damage. The recent well drilling experiences indicate that drilling problems in the shallow clays at Hot Sulphur Springs can be reduced. In addition, average penetration rates through the caprock system can be on the order of 25 to 35 feet per hour. This information has greatly reduced the original estimated well costs that were based on previous exploration drilling efforts. Successful production formation drilling will depend on finding drilling fluids that will not cause formation damage in the Smectite-rich fractured geothermal reservoir system. Information obtained at Hot Sulphur Springs may apply to other geothermal systems developed in volcanic settings.

Goranson, Colin

2005-03-01

264

Multielement geochemistry of solid materials in geothermal systems and its applications. Part 1. Hot-water system at the Roosevelt Hot Springs KGRA, Utah  

SciTech Connect

Geochemical studies of the geothermal system at Roosevelt Hot Springs, Utah, have led to development of chemical criteria for recognition of major features of the system and to a three-dimensional model for chemical zoning in the system. Based on this improved level of understanding several new or modified geochemical exploration and assessment techniques have been defined and are probably broadly applicable to evaluation of hot-water geothermal systems. The main purpose of this work was the development or adaptation of solids geochemical exploration techniques for use in the geothermal environment. (MHR)

Bamford, R.W.; Christensen, O.D.; Capuano, R.M.

1980-02-01

265

Optimization of Integrated Reservoir, Wellbore, and Power Plant Models for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Geothermal energy has the potential to become a substantially greater contributor to the U.S. energy market. An adequate investment in Enhanced Geothermal Systems (EGS) technology will be necessary in order to realize the potential of geothermal energy. This study presents an optimization of a waterbased Enhanced Geothermal System (EGS) modeled for AltaRock Energy's Newberry EGS Demonstration location. The optimization successfully integrates all three components of the geothermal system: (1) the present wellbore design, (2) the reservoir design, and (3) the surface plant design. Since the Newberry EGS Demonstration will use an existing well (NWG 55-29), there is no optimization of the wellbore design, and the aim of the study for this component is to replicate the present wellbore conditions and design. An in-house wellbore model is used to accurately reflect the temperature and pressure changes that occur in the wellbore fluid and the surrounding casing, cement, and earth during injection and production. For the reservoir design, the existing conditions, such as temperature and pressure at depth and rock density, are incorporated into the model, and several design variables are investigated. The engineered reservoir is modeled using the reservoir simulator TOUGH2 while using the graphical interface PetraSim for visualization. Several fracture networks are investigated with the goal of determining which fracture network yields the greatest electrical output when optimized jointly with the surface plant. A topological optimization of the surface is completed to determine what type of power plant is best suited for this location, and a parametric optimization of the surface plant is completed to determine the optimal operating conditions. The conditions present at the Newberry, Oregon EGS project site are the basis for this optimization. The subsurface conditions are favorable for the production of electricity from geothermal energy with rock temperatures exceeding 300°C at a well depth of 3 km. This research was completed in collaboration with AltaRock Energy, which has provided our research group with data from the Newberry well. The purpose of this thesis is to determine the optimal conditions for operating an Enhanced Geothermal System for the production of electricity at Newberry. It was determined that a fracture network consisting of five fractured zones carrying 15 kg/s of fluid is the best reservoir design out of those investigated in this study. Also, it was found that 100 m spacing between the fractured zones should be implemented as opposed to only 50 m of spacing. A double-flash steam power plant provides the best method of utilization of the geothermal fluid. For the maximum amount of electricity generation over the 30-year operating lifetime, the cyclone separator should operate at 205°C and the flash vessel should operate at 125°C.

Peluchette, Jason

266

Geochemical Attributes and Gradients Within Geothermal Systems Define the Distribution of Specific Microbial Populations  

NASA Astrophysics Data System (ADS)

Microorganisms in natural habitats interact with mineral surfaces in many different respects. For example, microorganisms are known to enhance the dissolution rates of some minerals via the production of organic acids and other exudates, but at the same time, may mineralize solid phases as a direct or indirect result of metabolic processes. It is also well-established that many microorganisms form biofilms on mineral surfaces, and may preferentially attach to surfaces rich in necessary nutrients or in elements used for energy conservation. In part due to the complexity of natural soil, water and sediments systems, it is generally difficult to ascertain mechanisms controlling the distribution of organisms on mineral surfaces and their role in mineral precipitation-dissolution reactions. Geothermal microbial communities are often less diverse than surface soils and sediments and offer opportunities for understanding relationships among specific microbial populations and geochemical processes that define the biogeochemical cycles of individual elements. We have investigated numerous acidic and near-neutral geothermal sites in Yellowstone National Park, and have performed a number of complimentary chemical and microbiological analyses to ascertain the role of microorganisms in S, Fe, As and Sb cycling in geothermal systems. Our results demonstrate the importance of microbiota in the formation of various Fe(III) oxide phases with variable anion chemistry, and the importance of chemolithotrophic metabolisms in Fe, S and As cycling. Where possible, these metabolisms are linked to specific microbial populations identified via molecular methods, and in some cases confirmed using isolation and characterization of individual organisms.

Inskeep, W. P.; Macur, R. E.; Korf, S.; Taylor, W. P.; Ackerman, G.; Kozubal, M.; Nagy, A.

2006-12-01

267

Insights From Laboratory Experiments On Simulated Faults With Application To Fracture Evolution In Geothermal Systems  

SciTech Connect

Laboratory experiments provide a wealth of information related to mechanics of fracture initiation, fracture propagation processes, factors influencing fault strength, and spatio-temporal evolution of fracture properties. Much of the existing literature reports on laboratory studies involving a coupling of thermal, hydraulic, mechanical, and/or chemical processes. As these processes operate within subsurface environments exploited for their energy resource, laboratory results provide insights into factors influencing the mechanical and hydraulic properties of geothermal systems. I report on laboratory observations of strength and fluid transport properties during deformation of simulated faults. The results show systematic trends that vary with stress state, deformation rate, thermal conditions, fluid content, and rock composition. When related to geophysical and geologic measurements obtained from engineered geothermal systems (e.g. microseismicity, wellbore studies, tracer analysis), laboratory results provide a means by which the evolving thermal reservoir can be interpreted in terms of physico-chemical processes. For example, estimates of energy release and microearthquake locations from seismic moment tensor analysis can be related to strength variations observed from friction experiments. Such correlations between laboratory and field data allow for better interpretations about the evolving mechanical and fluid transport properties in the geothermal reservoir – ultimately leading to improvements in managing the resource.

Stephen L. Karner, Ph.D

2006-06-01

268

Characterisation of induced fracture networks within an enhanced geothermal system using anisotropic electromagnetic modelling  

NASA Astrophysics Data System (ADS)

As opinions regarding the future of energy production shift towards renewable sources, enhanced geothermal systems (EGS) are becoming an attractive prospect. The characterisation of fracture permeability at depth is central to the success of EGS. Recent magnetotelluric (MT) studies of the Paralana geothermal system (PGS), an EGS in South Australia, have measured changes in MT responses which were attributed to fracture networks generated during fluid injection experiments. However, extracting permeabilities from these measurements remains problematic as conventional isotropic MT modelling is unable to accommodate for the complexities present within an EGS. To circumvent this problem, we introduce an electrical anisotropy representation to allow better characterisation of volumes at depth. Forward modelling shows that MT measurements are sensitive to subtle variations in anisotropy. Subsequent two-dimensional anisotropic forward modelling shows that electrical anisotropy is able to reproduce the directional response associated with fractures generated by fluid injection experiments at the PGS. As such, we conclude that MT monitoring combined with anisotropic modelling is a promising alternative to the micro-seismic method when characterising fluid reservoirs within geothermal and coal seam gas reservoirs.

MacFarlane, Jake; Thiel, Stephan; Pek, Josef; Peacock, Jared; Heinson, Graham

2014-11-01

269

The geochemistry and sequestration of H 2S into the geothermal system at Hellisheidi, Iceland  

NASA Astrophysics Data System (ADS)

The geochemistry and mineralization of H 2S in the geothermal system hosted by basaltic rock formation at Hellisheidi, SW Iceland, was studied. Injection of mixtures of H 2S with geothermal waste water and condensed steam into the > 230 °C geothermal aquifer is planned, where H 2S will hopefully be removed in the form of sulphides. The natural H 2S concentrations in the aquifer average 130 ppm. They are considered to be controlled by close approach to equilibrium with pyrite, pyrrhotite, prehnite and epidote. Injection of H 2S will increase significantly the reservoir H 2S equilibrium concentrations, resulting in mineralization of pyrite and possibly other sulphides as well as affecting the formation of prehnite and epidote. Based on reaction path modelling, the main factors affecting the H 2S mineralization capacity are related to the mobility and oxidation state of iron. At temperatures above 250 °C the pyrite mineralization is greatly reduced upon epidote formation leading to the much greater basalt dissolution needed to sequestrate the H 2S. Based on these findings, the optimum conditions for H 2S injection are aquifers with temperatures below ~ 250 °C where epidote formation is insignificant. Moreover, the results suggest that sequestration of H 2S into the geothermal system is feasible. The total flux of H 2S from the Hellisheidi power plant is 12,950 tonnes yr - 1 . Injection into 250 °C aquifers would result in dissolution of ~ 1000 tonnes yr - 1 of basalt for mineralization of H 2S as pyrite, corresponding to ~ 320 m 3 yr - 1 .

Stefánsson, Andri; Arnórsson, Stefán; Gunnarsson, Ingvi; Kaasalainen, Hanna; Gunnlaugsson, Einar

2011-05-01

270

A Code Intercomparison Study for THMC Simulators Applied to Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Numerical simulation codes have become critical tools for understanding complex geologic processes, as applied to technology assessment, system design, monitoring, and operational guidance. Recently the need for quantitatively evaluating coupled Thermodynamic, Hydrologic, geoMechanical, and geoChemical (THMC) processes has grown, driven by new applications such as geologic sequestration of greenhouse gases and development of unconventional energy sources. Here we focus on Enhanced Geothermal Systems (EGS), which are man-made geothermal reservoirs created where hot rock exists but there is insufficient natural permeability and/or pore fluids to allow efficient energy extraction. In an EGS, carefully controlled subsurface fluid injection is performed to enhance the permeability of pre-existing fractures, which facilitates fluid circulation and heat transport. EGS technologies are relatively new, and pose significant simulation challenges. To become a trusted analytical tool for EGS, numerical simulation codes must be tested to demonstrate that they adequately represent the coupled THMC processes of concern. This presentation describes the approach and status of a benchmarking and code intercomparison effort currently underway, supported by the U. S. Department of Energy's Geothermal Technologies Program. This study is being closely coordinated with a parallel international effort sponsored by the International Partnership for Geothermal Technology (IPGT). We have defined an extensive suite of benchmark problems, test cases, and challenge problems, ranging in complexity and difficulty, and a number of modeling teams are applying various simulation tools to these problems. The descriptions of the problems and modeling results are being compiled using the Velo framework, a scientific workflow and data management environment accessible through a simple web-based interface.

Scheibe, T. D.; White, M. D.; Wurstner White, S.; Sivaramakrishnan, C.; Purohit, S.; Black, G.; Podgorney, R. K.; Phillips, B. R.; Boyd, L.

2013-12-01

271

Simulation of Enhanced Geothermal Systems: A Benchmarking and Code Intercomparison Study  

SciTech Connect

Numerical simulation codes have become critical tools for understanding complex geologic processes, as applied to technology assessment, system design, monitoring, and operational guidance. Recently the need for quantitatively evaluating coupled Thermodynamic, Hydrologic, geoMechanical, and geoChemical (THMC) processes has grown, driven by new applications such as geologic sequestration of greenhouse gases and development of unconventional energy sources. Here we focus on Enhanced Geothermal Systems (EGS), which are man-made geothermal reservoirs created where hot rock exists but there is insufficient natural permeability and/or pore fluids to allow efficient energy extraction. In an EGS, carefully controlled subsurface fluid injection is performed to enhance the permeability of pre-existing fractures, which facilitates fluid circulation and heat transport. EGS technologies are relatively new, and pose significant simulation challenges. To become a trusted analytical tool for EGS, numerical simulation codes must be tested to demonstrate that they adequately represent the coupled THMC processes of concern. This presentation describes the approach and status of a benchmarking and code intercomparison effort currently underway, supported by the U. S. Department of Energy’s Geothermal Technologies Program. This study is being closely coordinated with a parallel international effort sponsored by the International Partnership for Geothermal Technology (IPGT). We have defined an extensive suite of benchmark problems, test cases, and challenge problems, ranging in complexity and difficulty, and a number of modeling teams are applying various simulation tools to these problems. The descriptions of the problems and modeling results are being compiled using the Velo framework, a scientific workflow and data management environment accessible through a simple web-based interface.

Scheibe, Timothy D.; White, Mark D.; White, Signe K.; Sivaramakrishnan, Chandrika; Purohit, Sumit; Black, Gary D.; Podgorney, Robert; Boyd, Lauren W.; Phillips, Benjamin R.

2013-06-30

272

Review of international geothermal activities and assessment of US industry opportunities: Summary report  

SciTech Connect

This report summarizes a study initiated to review and assess international developments in the geothermal energy field and to define business opportunities for the US geothermal industry. The report establishes data bases on the status of worldwide geothermal development and the competitiveness of US industry. Other factors identified include existing legislation, tax incentives, and government institutions or agencies and private sector organizations that promote geothermal exports. Based on the initial search of 177 countries and geographic entities, 71 countries and areas were selected as the most likely targets for the expansion of the geothermal industry internationally. The study then determined to what extent their geothermal resource had been developed, what countries had aided or participated in this development, and what plans existed for future development. Data on the energy, economic, and financial situations were gathered.

Not Available

1987-08-01

273

Review of international geothermal activities and assessment of US industry opportunities: Final report  

SciTech Connect

This study was initiated to review and assess international developments in the geothermal energy field and to define business opportunities for the US geothermal industry. The report establishes data bases on the status of worldwide geothermal development and the competitiveness of US industry. Other factors identified include existing legislation, tax incentives, and government institutions or agencies and private sector organizations that promote geothermal exports. Based on the initial search of 177 countries and geographic entities, 71 countries and areas were selected as the most likely targets for the expansion of the geothermal industry internationally. The study then determined to what extent their geothermal resource had been developed, what countries had aided or participated in this development, and what plans existed for future development. Data on the energy, economic, and financial situations were gathered.

Not Available

1987-08-01

274

An Assessment of the Tectonic Control in Defining the Geothermal System(s) of the Southern Chilean Andes  

NASA Astrophysics Data System (ADS)

Geothermal manifestations between Villarrica and Chihuio (39°15'-40°15'S, 71°40'-72°10'W), in the southern Chilean Andes, have been studied to assess the tectonic control in defining the geothermal systems of the area. These surface manifestations are in close spatial relationship with either the stratovolcanoes or the Liquińe-Ofqui Fault Zone (LOFZ, Cembrano et al., 1996). Volcanism and regional tectonics control the two vital components of the geothermal systems, viz., heat source and permeability. Two distinct domains of the geothermal systems, viz., structural (or non-volcanic) and volcanic have been identified, based on the chemical signatures of the thermal discharges and structural analysis of the lineaments. These two domains are distinct in their ways of heating up of meteoric water. The geothermal system(s) of the volcanic domain are closely associated with the volcanic centers, spatially as well as geochemically. In the case of the geothermal system(s) of volcanic domain, the heating of meteoric water is through absorption of heat and condensation of steam and gases by meteoric water during lateral circulation. These discharges do not exhibit the typical signatures of steam heated waters, which are subdued by near surface processes. The relation between the geothermal systems and fault and fracture density (FFD) is quite evident from the lineaments analysis. FFD correlates very well with the surface geothermal manifestations, as well as with their recharge areas. An increase in the (secondary) permeability in the uppermost 200-300 m in the areas of relatively high FFD values, necessary for lateral flow, is consistent with the lithology, structure and stratigraphy of the area. Although the lineaments scatter in a wide range, the absence of lineaments between N60°E and N100°E is noticeable, and is consistent with displacement and stress data of LOFZ (Lavenu and Cembrano, 1999; Cembrano et al., 2007; Lara and Cembrano, 2009). This indicates that such lineaments, which represent fractures and faults, are the result of recent deformation, causing secondary permeability that facilitates the subsurface flow particularly in NW-SE and N-S directions. Differential rates of exhumation and frictional heating (Parada et al., 2000; Thomson, 2002; Adriasola et al., 2006; Glodny et al., 2008) are the other two controlling factors for the geothermal systems of the area. (Project Funding: PBCT-PDA07) References: Adriasola, A.C., Thomson, S.N., Brix, M.R., Hervé, F., Stóckhert, B., 2006. Int. J. Earth Sci. 95: 501-528. Cembrano, J., Hervé, F., Lavenu, A., 1996. Tectonophysics 259: 55-66. Cembrano, J., Lara, L., 2009. Tectonophysics 471: 96-113. Cembrano, J., Lavenu, A., Yańez, G. (coordinators), Riquelme, R., Garcia, M., González, G., Herail, G., 2007. In: T. Moreno, W. Gibbons (Eds), The Geology of Chile, The Geological Society, London, 147-178. Cembrano, J., Schermer, E., Lavenu, A., Sanhueza, A., 2000. Tectonophysics 319: 129-149. Glodny, J., Gräfe, K., Echtler, H., Rosenau, M., 2008. Int. J. Earth Sci. 97: 1271-1291 Lavenu, A., Cembrano, J., 1999. J. Struct. Geol. 21: 1669-1691. Parada, M.A., Lahsen, A., Palacios, C., 2000. Geological Society of America Special Papers 2000, 91: 169- 179. Thomson, S.N., 2002. Geol. Soc. Am. Bull. 114: 1159-1173.

Sánchez, P.; Alam, M.; Parada, M.; Lahsen, A.

2010-12-01

275

Geothermal Power Potential in the Tatun Volcano Group, Taiwan  

NASA Astrophysics Data System (ADS)

Recent energy issues have concentrated the attention on finding alternative ones. National demands for renewable and sustainable energy increase rapidly, especially the geothermal power production, which is viewed as the most potential opportunity. This study attempts to estimate the geothermal powers in the Tatung Volcano Group (TVG), Taiwan and evaluate the possibility to develop the Enhanced Geothermal System. Tatung Volcano Group is located at the northwest part of Taiwan. It has violent volcanism during 0.8-0.20Ma, and is still active with many thermal manifestations. The young volcanic activity provides the TVG with high geothermal gradient and is well suitable for exploiting geothermal resources. Many explorations on geothermal energy have been accomplished in this area during1966-1973. They included resistivity survey, magnetic prospecting, gravity method, seismic prospecting and etc. In this study, we base on previous data and apply the probabilistic volumetric method proposed by Geotherm EX Inc., modified from the approach introduced by the USGS to evaluate the geothermal power potential in TVG. Meanwhile, use a Monte Carlo simulation technique to calculate the probability distribution of potentially recoverable energy reserves. The results show that the mean value is 270Mw, and P50 is 254Mw for 30 years, separately. Furthermore, the power potential of enhanced geothermal system in TVG is also estimated by the quantitative model proposed by Massachusetts Institute of Technology (MIT 2006). The results suggest that the mean value is 3,000 MW and P50 is 2,780 MW for 30 years, separately.

Tseng, H. H.; Song, S.

2013-12-01

276

Mass variation in outcome to high production activity in Kamojang Geothermal Field, Indonesia: A reservoir monitoring with relative and absolute gravimetry  

NASA Astrophysics Data System (ADS)

The Kamojang Geothermal Field (KGF) is a typical vapor dominated hydrothermal system in west Java, Indonesia. This geothermal field is the oldest exploited geothermal field in Indonesia. From 1983 to 2005, more than 160 million tons of steam has been exploited from the KGF and more than 30 million tons of condensed water and river water were injected to the reservoir system. Regarding to the electricity demand, installed capacity of KGF increased from 30 MWe to 140 MWe in 1987 and 200 MWe in 2007. Mass variation in the geothermal reservoir can be measured by using the map of the gravity changes. Gravity changes observed in the KGF between 1999 and 2005 at 51 benchmarks are interpreted in terms of a change of mass. Concerning to the production mass increase, gravity changes also observed between 1999 and 2008 at 30 benchmarks. The recent gravity measurement was conducted using absolute gravimeter in 2009 and 2010 at 12 gravity benchmarks. Mass variation in the reservoir was caused by production and injection activities. Mass variation in KGF from 1999 to 2005 is about -3.34 Mt/year while is about -3.78 Mt/year from 1999 to 2008. Another period between 2009 and 2010, mass variation decreased about -8.24 Mt. According to the history of production and injection, natural recharge to the KGF's reservoir is estimated at about 2.77 Mt/year from 1999 to 2005 and 2.75 Mt/year from 1999 to 2008. Between 2009 and 2010, KGF has a bigger mass deficiency rate throughout 200 MWe maintain production.

Sofyan, Y.; Kamah, Y.; Nishijima, J.; Fujimitsu, Y.; Ehara, S.; Fukuda, Y.; Taniguchi, M.

2011-11-01

277

US National Geothermal Data System: Web feature services and system operations  

NASA Astrophysics Data System (ADS)

The US National Geothermal Data System is being developed with support from the US Department of Energy to reduce risk in geothermal energy development by providing online access to the body of geothermal data available in the US. The system is being implemented using Open Geospatial Consortium web services for catalog search (CSW), map browsing (WMS), and data access (WFS). The catalog now includes 2427 registered resources, mostly individual documents accessible via URL. 173 WMS and WFS services are registered, hosted by 4 NGDS system nodes, as well as 6 other state geological surveys. Simple feature schema for interchange formats have been developed by an informal community process in which draft content models are developed based on the information actually available in most data provider's internal datasets. A template pattern is used for the content models so that commonly used content items have the same name and data type across models. Models are documented in Excel workbooks and posted for community review with a deadline for comment; at the end of the comment period a technical working group reviews and discusses comments and votes on adoption. When adopted, an XML schema is implemented for the content model. Our approach has been to keep the focus of each interchange schema narrow, such that simple-feature (flat file) XML schema are sufficient to implement the content model. Keeping individual interchange formats simple, and allowing flexibility to introduce new content models as needed have both assisted in adoption of the service architecture. One problem that remains to be solved is that off-the-shelf server packages (GeoServer, ArcGIS server) do not permit configuration of a normative schema location to be bound with XML namespaces in instance documents. Such configuration is possible with GeoServer using a more complex deployment process. XML interchange format schema versions are indicated by the namespace URI; because of the schema location problems, namespace URIs are redirected to the normative schema location. An additional issue that needs consideration is the expected lifetime of a service instance. A service contract should be accessible online and discoverable as part of the metadata for each service instance; this contract should specify the policy for service termination process--e.g. how notification will be made, if there is an expected end-of-life date. Application developers must be aware of these lifetime limitations to avoid unexpected failures. The evolution of the the service inventory to date has been driven primarily by data providers wishing to improve access to their data holdings. Focus is currently shifting towards improving tools for data consumer interaction--search, data inspection, and download. Long term viability of the system depends on business interdependence between the data providers and data consumers.

Richard, Stephen; Clark, Ryan; Allison, M. Lee; Anderson, Arlene

2013-04-01

278

Review of International Geothermal Activities and Assessment of US Industry Opportunites: Final Report  

SciTech Connect

This report contains detailed summaries, with bibliographies, of past, present, and planned geothermal development in 71 selected countries and areas. The report gives a pretty good description of types of work that had been done in each country by the mid 1980s, but does not tell much about which geothermal-provider country did the work. There are maps for most of the countries. There are numbers for market factors, but not for estimated geothermal potential. The information in this document has been superceded by the country summaries in the World Geothermal Congress Transactions of 1995, 2000, and 2005. This report was prepared by Meridian Corporation, Alexandria, VA. (DJE 2005)

None

1987-08-01

279

Geologic and hydrologic research on the Moana geothermal system, Washoe County, Nevada  

SciTech Connect

The Moana geothermal area is the largest single low- to moderate-temperature geothermal resource in the State of Nevada presently employed for direct-use applications. Approximately 150 individual wells, representing a total estimated investment of $5 to $7 million, are presently used to provide heat ahd hot water to more than 130 private residences, several churches and two large motels. Although most of the wells are constructed to meet the heating needs of individual homes, a large-scale district space heating system, designed to supply heat to 60 houses from a single well, is now being developed. Usable temperatures range from 50 to 99/sup 0/C (120 to 210/sup 0/F); well depths range from 60 to 400 m (100 to 1300 ft). The number of new wells coming on-line in Moana is two to three per month. Development of the resource has been largely unregulated and questions dealing with reported reservoir temperature and water level declines, loss of artesian flow, and fluid disposal have recently surfaced. In October 1982, a geologic and hydrologic research program began that was designed to provide detailed geothermal reservoir data to present or prospective developers. The program combines geophysical, geochemical, and geological surveys of the Moana resource area with a drilling program for 5 monitor/observation wells. Data from this program are supplied directly to developers as well as state and local government agencies to provide for prudent resource development. This paper summarizes the program elements and describes the present status.

Flynn, T.; Ghusn, G. Jr.

1983-12-01

280

Hydrogeochemistry and preliminary reservoir model of the Platanares Geothermal System, Honduras, Central America  

SciTech Connect

A detailed hydrogeochemical investigation has been performed at Platanares, Honduras in preparation for shallow geothermal exploration drilling. Platanares is not associated with any Quaternary volcanism but lies in a tectonic zone of late Tertiary to Quaternary extension. Thermal fluids are characterized by pH between 7 and 10, Cl < 40 mg/l, HCO/sub 3/ > SO/sub 4/ > Cl, B less than or equal to 17 mg/l, Li less than or equal to 4 mg/l and As less than or equal to 1.25 mg/l. Various geochemical indicators show that mixing of hot and cold end-member fluids is an important hydrologic process at this site. Geothermometers indicate the geothermal system equilibrated at roughly 225/sup 0/C while trace element chemistry indicates the reservoir resides in Cretaceous red beds of the Valle de Angeles Group. Based on the discharge rates of thermal features, the minimum power output of the Platanares geothermal site is about 45 MW (thermal).

Goff, F.; Shevenell, L.; Janik, C.J.; Truesdell, A.H.; Grigsby, C.O.; Paredes, R.

1986-01-01

281

Improved Detection of Microearthquakes: Application of Matched Field Processing (MFP) to Traditional and Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

We investigate the microseismicity in both traditional and Enhanced Geothermal Systems (EGS) and compare the temporal distribution of microseismic events to well fluid injection data. We apply the empirical and model-based Matched Field Processing (MFP) methods to continuous seismic data from the Salton Sea geothermal field and the DOE Newberry EGS site. MFP is a non-traditional event detection method that can identify more and smaller events than traditional detection methods alone. The empirical MFP method uses known catalog events as master templates to identify new microearthquakes while the model-based MFP method uses synthetic sources computed across a subsurface 3D grid as master templates. Salton Sea data between January 2008 and December 2011 was downloaded off the SCEDC website and high-quality master events were identified from the online catalog. We created empirical matched field steering vector calibrations for 7 three-component stations within the Salton Sea Geothermal Field. The original Salton Sea earthquake catalog identified 4202 events. When we applied the empirical MFP technique to the same data, we identified 5005 additional events (~119% more events). We compare the results from this traditional geothermal area with results obtained from the Newberry EGS site, for which we have 8 three-component stations. The Newberry catalog originally identified 204 events in 3 months while the MFP technique identified 249 additional events (~122% more events). We will compare the results from using the empirical MFP method at the Newberry EGS site with results obtained from using model-based master templates. Additionally, we compare the number of events in the improved earthquake catalogs with available fluid injection data. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Templeton, D. C.; Harris, D.; Goebel, M.

2013-12-01

282

Pumpernickel Valley Geothermal Project Thermal Gradient Wells  

SciTech Connect

The Pumpernickel Valley geothermal project area is located near the eastern edge of the Sonoma Range and is positioned within the structurally complex Winnemucca fold and thrust belt of north-central Nevada. A series of approximately north-northeast-striking faults related to the Basin and Range tectonics are superimposed on the earlier structures within the project area, and are responsible for the final overall geometry and distribution of the pre-existing structural features on the property. Two of these faults, the Pumpernickel Valley fault and Edna Mountain fault, are range-bounding and display numerous characteristics typical of strike-slip fault systems. These characteristics, when combined with geophysical data from Shore (2005), indicate the presence of a pull-apart basin, formed within the releasing bend of the Pumpernickel Valley – Edna Mountain fault system. A substantial body of evidence exists, in the form of available geothermal, geological and geophysical information, to suggest that the property and the pull-apart basin host a structurally controlled, extensive geothermal field. The most evident manifestations of the geothermal activity in the valley are two areas with hot springs, seepages, and wet ground/vegetation anomalies near the Pumpernickel Valley fault, which indicate that the fault focuses the fluid up-flow. There has not been any geothermal production from the Pumpernickel Valley area, but it was the focus of a limited exploration effort by Magma Power Company. In 1974, the company drilled one exploration/temperature gradient borehole east of the Pumpernickel Valley fault and recorded a thermal gradient of 160oC/km. The 1982 temperature data from five unrelated mineral exploration holes to the north of the Magma well indicated geothermal gradients in a range from 66 to 249oC/km for wells west of the fault, and ~283oC/km in a well next to the fault. In 2005, Nevada Geothermal Power Company drilled four geothermal gradient wells, PVTG-1, -2, -3, and -4, and all four encountered geothermal fluids. The holes provided valuable water geochemistry, supporting the geothermometry results obtained from the hot springs and Magma well. The temperature data gathered from all the wells clearly indicates the presence of a major plume of thermal water centered on the Pumpernickel Valley fault, and suggests that the main plume is controlled, at least in part, by flow from this fault system. The temperature data also defines the geothermal resource with gradients >100oC/km, which covers an area a minimum of 8 km2. Structural blocks, down dropped with respect to the Pumpernickel Valley fault, may define an immediate reservoir. The geothermal system almost certainly continues beyond the recently drilled holes and might be open to the east and south, whereas the heat source responsible for the temperatures associated with this plume has not been intersected and must be at a depth greater than 920 meters (depth of the deepest well – Magma well). The geological and structural setting and other characteristics of the Pumpernickel Valley geothermal project area are markedly similar to the portions of the nearby Dixie Valley geothermal field. These similarities include, among others, the numerous, unexposed en echelon faults and large-scale pull-apart structure, which in Dixie Valley may host part of the geothermal field. The Pumpernickel Valley project area, for the majority of which Nevada Geothermal Power Company has geothermal rights, represents a geothermal site with a potential for the discovery of a relatively high temperature reservoir suitable for electric power production. Among locations not previously identified as having high geothermal potential, Pumpernickel Valley has been ranked as one of four sites with the highest potential for electrical power production in Nevada (Shevenell and Garside, 2003). Richards and Blackwell (2002) estimated the total heat loss and the preliminary production capacity for the entire Pumpernickel Valley geothermal system to be at 35MW. A more conservative estimate, for

Z. Adam Szybinski

2006-01-01

283

Identification of High Angle Structures Controlling the Geothermal System at Rye Patch, Nevada.  

NASA Astrophysics Data System (ADS)

The successful completion of a recent well in the Rye Patch Geothermal field, located in Pershing County, Nevada, supports the geologic and geophysical interpretation that high angle structures control this geothermal system. Although lower angle structures are present, hot water migrates up from deeper sources along high angle faults more efficiently than structures with a shallower dip. Earlier attempts to develop the resource focused on structures that dipped at an angle between 60 and 70 degrees from horizontal. Recently acquired geophysical data indicated that numerous high angle structures were present in the area, with dips between 80 and 90 degrees. Original drilling targets focused on the subsurface projection of a surface structure, mapped as the Rye Patch fault, with an erroneously low angle. These early attempts at drilling were discouraging and might have been more successful if additional geology and geophysics were used to evaluate the geothermal system and map the Rye Patch fault more accurately. The successful completion of the most recent well can be attributed to the incorporation of the geology of previous wells with additional geology and geophysics. Temperature gradient holes were used to confirm that the Rye Patch fault provided the primary plumbing for this geothermal system, and 3D seismic data indicated that most of the structures had dips between 80 and 90 degrees. Geothermometry at Rye Patch indicates that the resource has a relatively high quartz equilibrium temperature and it is speculated that the higher the angle of the structural control, the higher the resource temperature. The dip of Basin and Range normal faults varies considerably and the interpretation of these structures for geothermal, fossil geothermal mineral prospects, and or oil and gas prospects is important. At Rye Patch, the high angle structure feeds geothermal fluids into cavernous limestone beds, dipping to the west usually between 40 and 60 degrees, which is a shallower dip than the Rye Patch fault itself. Resistivity surveys at Rye Patch mapped the westward dipping anomalies, which correspond to the cavernous limestone porosity, and numerous vertical anomalies; which are attributable to the high angle normal faults. Time slices of interpreted 3D seismic data identified numerous high angle structures; however none of these seismic structures could be correlated with the Rye Patch fault. It is inferred that the Rye Patch Fault is the youngest fault in the system, having the only surface expression, and therefore the least amount of displacement, resulting in a difficult seismic target. The most recent well was targeted to intercept the Rye Patch fault at 4500' after evaluating the shallower intermediate depth limestone reservoir at about 2000'. Upon testing of the intermediate depth reservoir it was concluded that this zone was capable of commercial production and the well would be completed in this shallower interval

Ehni, W. J.

2001-12-01

284

Recirculation System for Geothermal Energy Recovery in Sedimentary Formations: Laboratory Experiments and Numerical Simulations  

NASA Astrophysics Data System (ADS)

Geothermal energy resources are more widespread than previously thought and have the potential for providing a significant amount of sustainable clean energy worldwide. In particular, hot permeable sedimentary formations provide many advantages over traditional geothermal recovery and enhanced geothermal systems in low permeability crystalline formations. These include: (1) eliminating the need for hydraulic fracturing, (2) significant reduction in risk for induced seismicity, (3) reducing the need for surface wastewater disposal, (4) contributing to decreases in greenhouse gases, and (5) potential use for CO2 sequestration. Advances in horizontal drilling, completion, and production technology from the oil and gas industry can now be applied to unlock these geothermal resources. Here, we present experimental results from a laboratory scale circulation system and numerical simulations aimed at quantifying the heat transfer capacity of sedimentary rocks. Our experiments consist of fluid flow through a saturated and pressurized sedimentary disc of 23-cm diameter and 3.8-cm thickness heated along its circumference at a constant temperature. Injection and production ports are 7.6-cm apart in the center of the disc. We used DI de-aired water and mineral oil as working fluids and explored temperatures from 20 to 150 oC and flow rates from 2 to 30 ml/min. We performed experiments on sandstone samples (Castlegate and Kirby) with different porosity, permeability and thermal conductivity to evaluate the effect of hydraulic and thermal properties on the heat transfer capacity of sediments. The producing fluid temperature followed an exponential form with time scale transients between 15 and 45 min. Steady state outflow temperatures varied between 60% and 95% of the set boundary temperature, higher percentages were observed for lower temperatures and flow rates. We used the flow and heat transport simulator TOUGH2 to develop a numerical model of our laboratory setting. Given the remarkable match between our observations and numerical results, we extended our model to explore a wider range of thermal and hydrological parameters beyond the experimental conditions. Our results prove the capability of heat transfer in sedimentary formations for geothermal energy production.) Sandstone sample with two thermally insulating Teflon caps (white discs). In and out arrows indicate the flow direction while the sample is heated along its circumference (heater not shown). B) Example of a 2D temperature distribution during injection. White x shows the location of the flow ports, inlet (left) and outlet (right). Red is the set boundary temperature and blue is the fluid temperature at the inlet.

Elkhoury, J. E.; Detwiler, R. L.; Serajian, V.; Bruno, M. S.

2012-12-01

285

THERMAL CHARACTERISTICS OF THE CHENA HOT SPRINGS ALASKA GEOTHERMAL SYSTEM  

Microsoft Academic Search

Chena Hot Springs is located in the east-central part of the Alaska within the Yukon-Tanana Plateau, about 75 km east of Fairbanks. It is a moderate temperature deep circulation system typical of interior Alaska. The main shallow upflow zone is about 2000 ft long and 300 ft wide. The system is located at the edge of a granitic body where

Kamil Erkan; Gwen Holdman; David Blackwell; Walter Benoit

286

Application of seismic tomographic techniques in the investigation of geothermal systems  

SciTech Connect

The utility of microearthquake data for characterizing the Northwest Geysers geothermal field and the Long Valley Caldera (LVC) was investigated. Three-dimensional (3-D) P- and S-wave seismic velocity models were estimated for the Coldwater Creek Steam Field (CCSF) in the Northwest Geysers region. Hypocenters relocated using these 3-D models appear to be associated with the steam producing zone, with a deeper cluster of hypocenters beneath an active injection well. Spatial and temporal patterns of seismicity exhibit strong correlation with geothermal exploitation. A 3-D differential attenuation model was also developed for the CCSF from spectral ratios corrected for strong site effects. High-velocity anomalies and low attenuation in the near surface correspond to Franciscan metagraywacke and greenstone units. Microearthquakes recorded at seismographic stations located near the metagraywacke unit exhibit high corner frequencies. Low-velocity anomalies and higher attenuation in the near surface are associated with sections of Franciscan melange. Near-surface high attenuation and high Vp/Vs are interpreted to indicate liquid-saturated regions affected by meteoric recharge. High attenuation and low Vp/Vs marks the steam producing zone, suggesting undersaturation of the reservoir rocks. The extent of the high attenuation and low Vp/Vs anomalies suggest that the CCSF steam reservoir may extend northwestward beyond the known producing zone. This study concludes that microearthquake monitoring may be useful as an active reservoir management tool. Seismic velocity and attenuation structures as well as the distribution of microearthquake activity can be used to identify and delineate the geothermal reservoir, while temporal variations in these quantities would be useful in tracking changes during exploitation.

Romero, A.E. Jr.

1995-05-01

287

Geothermal Progress Monitor 12  

SciTech Connect

Some of the more interesting articles in this GPM are: DOE supporting research on problems at The Geysers; Long-term flow test of Hot Dry Rock system (at Fenton Hill, NM) to begin in Fiscal Year 1992; Significant milestones reached in prediction of behavior of injected fluids; Geopressured power generation experiment yields good results. A number of industry-oriented events and successes are reported, and in that regard it is noteworthy that this report comes near the end of the most active decade of geothermal power development in the U.S. There is a table of all operating U.S. geothermal power projects. The bibliography of research reports at the end of this GPM is useful. (DJE 2005)

None

1990-12-01

288

Geophysical study of the Monroe-Red Hill geothermal system  

Microsoft Academic Search

A detailed geophysical study consisting of heat flow, dipole-dipole resistivity, ground magnetics and gravity was conducted in the vicinity of Monroe, Utah to assess the resource potential of an identified hydrothermal system. The detailed study covered a 40 km² area along the Sevier fault near the Monroe-Red Hill hot springs. Fourteen 100m dipole-dipole resistivity profiles across the system were used

C. W. Mase; D. S. Chapman; S. H. Ward

1978-01-01

289

Naturally occurring arsenic in terrestrial geothermal systems of western Anatolia, Turkey: potential role in contamination of freshwater resources.  

PubMed

Arsenic (As) contamination in terrestrial geothermal systems has been identified in many countries worldwide. Concentrations higher than 0.01 mg/L are detrimental to human health. We examined potential consequences for As contamination of freshwater resources based on hydrogeochemical investigations of geothermal waters in deep wells and hot springs collected from western Anatolia, Turkey. We analyzed samples for major ions and trace element concentrations. Temperature of geothermal waters in deep wells showed extreme ranges (40 and 230 °C), while, temperature of hot spring fluids was up to 90 °C. The Piper plot illustrated two dominant water types: Na-HCO3(-) type for geothermal waters in deep wells and Ca-HCO3(-) type for hot spring fluids. Arsenic concentration ranged from 0.03 to 1.5mg/L. Dominance of reduced As species, i.e., As(III), was observed in our samples. The Eh value ranged between -250 and 119 mV, which suggests diverse geochemical conditions. Some of the measured trace elements were found above the World Health Organization guidelines and Turkish national safe drinking water limits. The variation in pH (range: 6.4-9.3) and As in geothermal waters suggest mixing with groundwater. Mixing of geothermal waters is primarily responsible for contamination of freshwater resources and making them unsuitable for drinking or irrigation. PMID:23498168

Bundschuh, Jochen; Maity, Jyoti Prakash; Nath, Bibhash; Baba, Alper; Gunduz, Orhan; Kulp, Thomas R; Jean, Jiin-Shuh; Kar, Sandeep; Yang, Huai-Jen; Tseng, Yu-Jung; Bhattacharya, Prosun; Chen, Chien-Yen

2013-11-15

290

Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems  

SciTech Connect

Geothermal energy is recovered by circulating water through heat exchange areas within a hot rock mass. Geothermal reservoir rock masses generally consist of igneous and metamorphic rocks that have low matrix permeability. Therefore, cracks and fractures play a significant role in extraction of geothermal energy by providing the major pathways for fluid flow and heat exchange. Therefore, knowledge of the conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fractures are created in the reservoir using hydraulic fracturing. Multiple fractures are preferred because of the large size necessary when using only a single fracture. Although the basic idea is rather simple, hydraulic fracturing is a complex process involving interactions of high pressure fluid injections with a stressed hot rock mass, mechanical interaction of induced fractures with existing natural fractures, and the spatial and temporal variations of in-situ stress. As a result, it is necessary to develop tools that can be used to study these interactions as an integral part of a comprehensive approach to geothermal reservoir development, particularly enhanced geothermal systems. In response to this need we have developed advanced poro-thermo-chemo-mechanical fracture models for rock fracture research in support of EGS design. The fracture propagation models are based on a regular displacement discontinuity formulation. The fracture propagation studies include modeling interaction of induced fractures. In addition to the fracture propagation studies, two-dimensional solution algorithms have been developed and used to estimate the impact of pro-thermo-chemical processes on fracture permeability and reservoir pressure. Fracture permeability variation is studied using a coupled thermo-chemical model with quartz reaction kinetics. The model is applied to study quartz precipitation/dissolution, as well as the variation in fracture aperture and pressure. Also, a three-dimensional model of injection/extraction has been developed to consider the impact poro- and thermoelastic stresses on fracture slip and injection pressure. These investigations shed light on the processes involved in the observed phenomenon of injection pressure variation (e.g., in Coso), and allow the assessment of the potential of thermal and chemical stimulation strategies.

Ahmad Ghassemi

2009-10-01

291

Liu, Rees and Spitler. 1 Simulation of a Geothermal Bridge Deck Anti-icing System and Experimental Validation  

E-print Network

Liu, Rees and Spitler. 1 Simulation of a Geothermal Bridge Deck Anti-icing System and Experimental-term performance under expected future weather conditions. A method of simulating the performance of such a system of each component and their integration into the simulation of the whole system are described. Validation

292

Structural Inventory of Great Basin Geothermal Systems and Definition of Favorable Structural Settings  

SciTech Connect

Over the course of the entire project, field visits were made to 117 geothermal systems in the Great Basin region. Major field excursions, incorporating visits to large groups of systems, were conducted in western Nevada, central Nevada, northwestern Nevada, northeastern Nevada, east?central Nevada, eastern California, southern Oregon, and western Utah. For example, field excursions to the following areas included visits of multiple geothermal systems: - Northwestern Nevada: Baltazor Hot Spring, Blue Mountain, Bog Hot Spring, Dyke Hot Springs, Howard Hot Spring, MacFarlane Hot Spring, McGee Mountain, and Pinto Hot Springs in northwest Nevada. - North?central to northeastern Nevada: Beowawe, Crescent Valley (Hot Springs Point), Dann Ranch (Hand?me?Down Hot Springs), Golconda, and Pumpernickel Valley (Tipton Hot Springs) in north?central to northeast Nevada. - Eastern Nevada: Ash Springs, Chimney Hot Spring, Duckwater, Hiko Hot Spring, Hot Creek Butte, Iverson Spring, Moon River Hot Spring, Moorman Spring, Railroad Valley, and Williams Hot Spring in eastern Nevada. - Southwestern Nevada?eastern California: Walley’s Hot Spring, Antelope Valley, Fales Hot Springs, Buckeye Hot Springs, Travertine Hot Springs, Teels Marsh, Rhodes Marsh, Columbus Marsh, Alum?Silver Peak, Fish Lake Valley, Gabbs Valley, Wild Rose, Rawhide? Wedell Hot Springs, Alkali Hot Springs, and Baileys/Hicks/Burrell Hot Springs. - Southern Oregon: Alvord Hot Spring, Antelope Hot Spring?Hart Mountain, Borax Lake, Crump Geyser, and Mickey Hot Spring in southern Oregon. - Western Utah: Newcastle, Veyo Hot Spring, Dixie Hot Spring, Thermo, Roosevelt, Cove Fort, Red Hill Hot Spring, Joseph Hot Spring, Hatton Hot Spring, and Abraham?Baker Hot Springs. Structural controls of 426 geothermal systems were analyzed with literature research, air photos, google?Earth imagery, and/or field reviews (Figures 1 and 2). Of the systems analyzed, we were able to determine the structural settings of more than 240 sites. However, we found that many “systems” consisted of little more than a warm or hot well in the central part of a basin. Such “systems” were difficult to evaluate in terms of structural setting in areas lacking in geophysical data. Developed database for structural catalogue in a master spreadsheet. Data components include structural setting, primary fault orientation, presence or absence of Quaternary faulting, reservoir lithology, geothermometry, presence or absence of recent magmatism, and distinguishing blind systems from those that have surface expressions. Reviewed site locations for all 426 geothermal systems– Confirmed and/or relocated spring and geothermal sites based on imagery, maps, and other information for master database. Many systems were mislocated in the original database. In addition, some systems that included several separate springs spread over large areas were divided into two or more distinct systems. Further, all hot wells were assigned names based on their location to facilitate subsequent analyses. We catalogued systems into the following eight major groups, based on the dominant pattern of faulting (Figure 1): - Major normal fault segments (i.e., near displacement maxima). - Fault bends. - Fault terminations or tips. - Step?overs or relay ramps in normal faults. - Fault intersections. - Accommodation zones (i.e., belts of intermeshing oppositely dipping normal faults), - Displacement transfer zones whereby strike?slip faults terminate in arrays of normal faults. - Transtensional pull?aparts. These settings form a hierarchal pattern with respect to fault complexity. - Major normal faults and fault bends are the simplest. - Fault terminations are typically more complex than mid?segments, as faults commonly break up into multiple strands or horsetail near their ends. - A fault intersection is generally more complex, as it generally contains both multiple fault strands and can include discrete di...

James E. Faulds

2013-12-31

293

Geothermal drilling technology update  

SciTech Connect

Sandia National Laboratories conducts a comprehensive geothermal drilling research program for the US Department of Energy, Office of Geothermal Technologies. The program currently includes seven areas: lost circulation technology, hard-rock drill bit technology, high-temperature instrumentation, wireless data telemetry, slimhole drilling technology, Geothermal Drilling Organization (GDO) projects, and drilling systems studies. This paper describes the current status of the projects under way in each of these program areas.

Glowka, D.A.

1997-04-01

294

A brine interface in the Salton Sea Geothermal System, California: Fluid geochemical and isotopic characteristics  

SciTech Connect

Data from 71 geothermal production intervals in 48 wells from the Salton Sea Geothermal System (SSGS) indicate that fluids in that system cluster into two distinct populations in terms of their salinity and their stable isotopic compositions. The distinctive, hot, hypersaline brine (typically >20 wt% total dissolved solids) for which the SSGS is known is overlain by a cooler (<260{degree}C) fluid with distinctly lower salinity (typically <10 wt% total dissolved solids). Hypersaline brines have high and rather consistent {sup 18}O shifts produced by water-rock interaction and have a very narrow range in {delta}D values. Low TDS fluids, on the other hand, show a wide range in both {delta}D and {delta}{sup 18}O. production of both types of fluid from closely spaced geothermal wells in many regions of the SSGS indicates that a relatively sharp salinity interface exists over much of the field. The fluid interface typically cross-cuts sedimentary bedding but is consistently found where reservoir temperatures are approximately 260{degree}C. At these temperatures, hypersaline brines have densities of approximately 1.0 gm/cm{sup 3}, while the low TDS fluids have densities as low as 0.85 gm/cm{sup 3}. This stable, density-stratified interface acts as a barrier to convective heat and mass transfer in the SSGS, isolating the hypersaline reservoir from overlying dilute fluids. A lithologic cap implied by previous SSGS models is unnecessary in such a stratified system since heat and mass transfer across the interface must occur by slow conductive, diffusional and interface mixing processes regardless of local permeability.

Williams, A.E.; McKibben, M.A. (Univ. of California, Riverside (USA))

1989-08-01

295

Comparing Maintenance Costs of Geothermal Heat Pump Systems with other HVAC Systems in Lincoln Public Schools: Repair, Service, and Corrective Actions  

SciTech Connect

The Lincoln Public School District, in Lincoln, Nebraska, recently installed vertical-bore geothermal heat pump systems in four, new, elementary schools. Because the district has consistent maintenance records and procedures, it was possible to study repair, service and corrective maintenance requests for 20 schools in the district. Each school studied provides cooling to over 70% of its total floor area and uses one of the following heating and cooling systems: vertical-bore geothermal heat pumps (GHPs), air-cooled chiller with gas-fired hot water boiler (ACUGHWB), water-cooled chiller with gas-fired hot water boiler (WCCYGHWB), or water-cooled chiller with gas-fired steam boiler (WCUGSB). Preventative maintenance and capital renewal activities were not included in the available database. GHP schools reported average total costs at 2.13 cents/ft{sup 2}-yr, followed by ACC/GHWB schools at 2.88 cents/ft{sup 2}-yr, WCC/GSB schools at 3.73 cents/ft{sup 2}-yr, and WCC/GHWB schools at 6.07 cents/ft{sup 2}-yr. Because of tax-exemptions on material purchases, a reliance on in-house labor, and the absence of preventative maintenance records in the database, these costs are lower than those reported in previous studies. A strong relationship (R{sup 2}=O.52) was found between costs examined and cooling system age: the newer the cooling equipment, the less it costs to maintain.

Martin, M.A.; Durfee, D.J.; Hughes, P.J.

1999-06-19

296

Influence of time on metamorphism of sedimentary organic matter in liquid-dominated geothermal systems, western North America.  

USGS Publications Warehouse

Reflectance data of sedimentary organic matter samples from six liquid-dominated geothermal systems are strongly temperature-dependent. Geologic evidence indicates that reaction duration ranges from approx 103 to 106 yr in these systems that appear to have near-maximum temperatures. The strong temperature dependence of vitrinite reflectance indicates that after about 104 yr, reaction duration has little or no influence on metamorphism of organic matter in liquid-dominated geothermal systems. These data indicate that vitrinite reflectance can be used to determine the maximum temperature reached in hot sedimentary basins of moderate longevity. -after Author

Barker, C.E.

1983-01-01

297

Temporary Bridging Agents for use in Drilling and Completion of Enhanced Geothermal Systems  

SciTech Connect

CSI Technologies, in conjunction with Alta Rock Energy and the University of Utah have undergone a study investigating materials and mechanisms with potential for use in Enhanced Geothermal Systems wells as temporary diverters or lost circulation materials. Studies were also conducted with regards to particle size distribution and sealing effectiveness using a lab-scale slot testing apparatus to simulate fractures. From the slot testing a numerical correlation was developed to determine the optimal PSD for a given fracture size. Field trials conducted using materials from this study were also successful.

Watters, Larry; Watters, Jeff; Sutton, Joy; Combs, Kyle; Bour, Daniel; Petty, Susan; Rose, Peter; Mella, Michael

2011-12-21

298

Using Estimated Risk to Develop Stimulation Strategies for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades, and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the generation of microseismicity through the shearing of pre-existing fractures or fault segments. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir through fluid injection against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. In this article we propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity of the previous 6 h with a (potentially site-specific) ground motion prediction equation to obtain a real-time seismic hazard curve; this is then convolved with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds, the injection is increased if the risk is below the amber level, decreased if the risk is between the amber and red levels, or stopped completely if the risk is above the red level. Based on simulations using a recently developed model of induced seismicity in geothermal systems, which is checked here using observations from the Basel EGS, in this article it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.

Douglas, John; Aochi, Hideo

2014-01-01

299

Using estimated risk to develop stimulation strategies for induced seismicity in enhanced geothermal systems  

NASA Astrophysics Data System (ADS)

Enhanced Geothermal Systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the shearing of pre-existing factures or fault segments, and hence by the generation of microseismicity. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir by injecting fluids against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. Douglas and Aochi (Pageoph, 2014) propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity rate of the previous six hours, with a (potentially site-specific) ground-motion prediction equation to obtain a real-time seismic hazard curve, and then the convolution of this with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds the injection is: increased (if the risk is below the amber level), decreased (if the risk is between amber and red levels) or stopped completely (if the risk is above the red level). Based on simulations using a recently developed model of induced seismicity in geothermal systems (Aochi et al., GJI, 2014), which is validated here using observations from the Basel EGS in 2006, it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.

Douglas, John; Aochi, Hideo

2014-05-01

300

Using Estimated Risk to Develop Stimulation Strategies for Enhanced Geothermal Systems  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades, and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the generation of microseismicity through the shearing of pre-existing fractures or fault segments. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir through fluid injection against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. In this article we propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity of the previous 6 h with a (potentially site-specific) ground motion prediction equation to obtain a real-time seismic hazard curve; this is then convolved with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds, the injection is increased if the risk is below the amber level, decreased if the risk is between the amber and red levels, or stopped completely if the risk is above the red level. Based on simulations using a recently developed model of induced seismicity in geothermal systems, which is checked here using observations from the Basel EGS, in this article it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.

Douglas, John; Aochi, Hideo

2014-08-01

301

Continuous on-line steam quality monitoring system of the Bacman Geothermal Production Field, Philippines  

SciTech Connect

In any operating geothermal power plant, steam quality is one of the most important parameters being monitored. In the Bacon-Manito Geothermal Production Field (BGPF), an online steam quality monitoring system have been installed in two operating power plants which provides an accurate, efficient and continuous real-time data which is more responsive to the various requirements of the field operation. The system utilizes sodium as an indicator of steam purity. Sodium concentration is read by the flame photometer located at the interface after aspirating a sample of the condensed steam through a continuous condensate sampler. The condensate has been degassed through a condensate-NCG separator. The flame photometer analog signal is then converted by a voltage-to-current converter/transmitter and relayed to the processor which is located at the control center through electrical cable to give a digital sodium concentration read-out at the control panel. The system features a high and high-high sodium level alarm, a continuous strip-chart recorder and a central computer for data capture, retrieval, and processing for further interpretation. Safety devices, such as the flame-off indicator at the control center and the automatic fuel cut-off device along the fuel line, are incorporated in the system.

Solis, R.P.; Chavez, F.C.; Garcia, S.E. [PNOC Energy Development Corp., Makati City (Philippines)] [and others

1997-12-31

302

Summary of geothermal exploration activity in the state of Washington from 1978 to 1983  

SciTech Connect

During the course of conducting the statewide reconnaissance study of Washington's potential geothermal resources, several specific areas and broader regions have been identified as targets which warrant a more concentrated effort. Over the past three years, the program has continued to identify new sites, but has concentrated on better defining the resource potential of the best areas. The locations of these geothermal areas are shown, and the level of progress for each area is shown, expressed as a percentage of completion for the various exploration tasks. Descriptions of the geothermal target areas are presented.

Korosec, M.A.

1984-01-01

303

Design and Implementation of Geothermal Energy Systems at West Chester University  

SciTech Connect

West Chester University is launching a comprehensive transformation of its campus heating and cooling systems from traditional fossil fuels (coal, oil and natural gas) to geothermal. This change will significantly decrease the institution's carbon footprint and serve as a national model for green campus efforts. The institution is in the process of designing and implementing this project to build well fields, a pumping station and install connecting piping to provide the geothermal heat/cooling source for campus buildings. This project addresses the US Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) goal to invest in clean energy technologies that strengthen the economy, protect the environment, and reduce dependence on foreign oil. In addition, this project advances EERE's efforts to establish geothermal energy as an economically competitive contributor to the US energy supply. For this grant, WCU will extend piping for its geo-exchange system. The work involves excavation of a trench approximately 8 feet wide and 10-12 feet deep located about 30 feet north of the curb along the north side of West Rosedale for a distance of approximately 1,300 feet. The trench will then turn north for the remaining distance (60 feet) to connect into the mechanical room in the basement of the Francis Harvey Green Library. This project will include crossing South Church Street near its intersection with West Rosedale, which will involve coordination with the Borough of West Chester. After installation of the piping, the trench will be backfilled and the surface restored to grass as it is now. Because the trench will run along a heavily-used portion of the campus, it will be accomplished in sections to minimize disruption to the campus as much as possible.

Greg Cuprak

2011-08-31

304

Vapliq hydrothermal systems, and the vertical permeability of Los Azufres, Mexico, geothermal reservoir  

SciTech Connect

We identify a new category of natural hydrothermal systems intermediate between liquid- and vapor-dominated. This category is characterized by a “vapliq” vertical pressure profile, which is nearly vaporstatic in the shallower portion of the system, and nearly boiling-point-for-depth at depth. The prototype of these systems is the geothermal field of Los Azufres, Mexico. To explore the thermohydrological conditions conducent to this type of system, we propose a 1-D vertical scenario based on generally accepted conceptual models of liquid- and vapor-dominated geothermal reservoirs. We use the corresponding mass and thermal energy transport equations to establish that a necessary condition for the existence of 2-phase hydrothermal systems is that the absolute value of the vertical thermal flux must exceed Q{sub min}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point of the system. The values of Q{sub min} are typically 1-4 times the average terrestrial flux. We also find that geothermal systems in which convective heat transport is accomplished by the well-known heat-pipe mechanism can exist only if the corresponding heat flux exceeds Q{sub min} and the permeability at the boiling point of the system is smaller than k{sub Bmax}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point. Typical values of k{sub Bmax} are 1-3 {times} 10{sup -18} m{sup 2}, suggesting a reason for the fact that all vapor-dominated systems are associated with very-low matrix permeability formations. Applying these insights, and the mass and heat transport equations to Los Azufres, we conclude that a contrast of 1-3 orders of magnitude exists between the vertical permeability at the boiling point and that corresponding to the vapor-dominated portion of the system. We propose that similar permeability contrasts may be responsible for the characteristic composite pressure observed in other vapliq systems.

Iglesias, Eduardo R.; Arellano, Victor M.

1988-01-01

305

Rock Mechanics and Enhanced Geothermal Systems: A DOE-sponsored Workshop to Explore Research Needs  

SciTech Connect

This workshop on rock mechanics and enhanced geothermal systems (EGS) was held in Cambridge, Mass., on June 20-21 2003, before the Soil and Rock America 2003 International Conference at MIT. Its purpose was to bring together experts in the field of rock mechanics and geothermal systems to encourage innovative thinking, explore new ideas, and identify research needs in the areas of rock mechanics and rock engineering applied to enhanced geothermal systems. The agenda is shown in Appendix A. The workshop included experts in the fields of rock mechanics and engineering, geological engineering, geophysics, drilling, the geothermal energy production from industry, universities and government agencies, and laboratories. The list of participants is shown is Appendix B. The first day consisted of formal presentations. These are summarized in Chapter 1 of the report. By the end of the first day, two broad topic areas were defined: reservoir characterization and reservoir performance. Working groups were formed for each topic. They met and reported in plenary on the second day. The working group summaries are described in Chapter 2. The final session of the workshop was devoted to reaching consensus recommendations. These recommendations are given in Chapter 3. That objective was achieved. All the working group recommendations were considered and, in order to arrive at a practical research agenda usable by the workshop sponsors, workshop recommendations were reduced to a total of seven topics. These topics were divided in three priority groups, as follows. First-priority research topics (2): {sm_bullet} Define the pre-existing and time-dependent geometry and physical characteristics of the reservoir and its fracture network. That includes the identification of hydraulically controlling fractures. {sm_bullet} Characterize the physical and chemical processes affecting the reservoir geophysical parameters and influencing the transport properties of fractures. Incorporate those processes in reservoir simulators. Second-priority research topics (4): {sm_bullet} Implement and proof-test enhanced fracture detection geophysical methods, such as 3-D surface seismics, borehole seismics, and imaging using earthquake data. {sm_bullet} Implement and proof-test enhanced stress measurement techniques, such as borehole breakout analysis, tilt-meters, and earthquake focal mechanism analysis. {sm_bullet} Implement and proof-test high-temperature down-hole tools for short-term and long-term diagnostics, such as borehole imaging, geophone arrays, packers, and electrical tools.

Francois Heuze; Peter Smeallie; Derek Elsworth; Joel L. Renner

2003-10-01

306

Volcanology and volcanic activity with a primary focus on potential hazard impacts for the Hawaii geothermal project  

SciTech Connect

This annotated bibliography reviews published references about potential volcanic hazards on the Island of Hawaii that are pertinent to drilling and operating geothermal wells. The first two sections of this annotated bibliography list the most important publications that describe eruptions of Kilauea volcano, with special emphasis on activity in and near the designated geothermal subzones. References about historic eruptions from Mauna Loa`s northeast rift zone, as well as the most recent activity on the southern flank of dormant Mauna Kea, adjacent to the Humu`ula Saddle are described. The last section of this annotated bibliography lists the most important publications that describe and analyze deformations of the surface of Kilauea and Mauna Loa volcanoes.

Moore, R.B. [Federal Center, Denver, CO (United States); Delaney, P.T. [2255 North Gemini Drive, Flagstaff, AZ (United States); Kauahikaua, J.P. [Geological Survey, Hawaii National Park, HI (United States). Hawaiian Volcano Observatory

1993-10-01

307

Reconstructing the geological and structural history of an active geothermal field: A case study from New Zealand  

NASA Astrophysics Data System (ADS)

The utilisation of geothermal systems benefits from an understanding of the host-rock geology, locations and controls of permeability pathways, and the nature and timing of magmatic sources providing thermal energy. Kawerau Geothermal Field in the central Taupo Volcanic Zone (TVZ) of New Zealand is currently developed for electricity generation and direct uses of high-temperature steam to ~ 200 MW electrical output. The Kawerau geothermal system is hosted in a sequence of volcanic lithologies (tuffs, lavas and intrusive bodies) and sediments that overlie faulted Mesozoic metasedimentary (greywacke) basement. Identification of lithologies in the volcanic/sedimentary sequence is challenging due to the levels of hydrothermal alteration and lithological similarities. A combination of detailed petrological investigations, consideration of the emplacement processes and greater certainty of crystallisation or eruption ages through U-Pb age determinations on zircons is used to reconstruct the depositional and faulting evolution of the rocks hosting the currently active hydrothermal system. The oldest event inferred is faulting of the greywacke along northwest-southeast orientated, dominantly strike-slip structures to generate half-grabens that were filled with sediments, incorporating two dated ignimbrites (2.38 ± 0.05 and 2.17 ± 0.05 Ma). A 1.46 ± 0.01 Ma ignimbrite was deposited relatively evenly across the field, implying that any topographic relief was subdued at that time. Subsequent deposition of ignimbrites occurred in episodes around 1.0, 0.55-0.6, and 0.32 Ma, interspersed with thin sedimentary sequences that accumulated at average rates of 0.06 mm yr- 1. Andesite lavas from a buried composite cone occur as a conformable package between units dated at 1.0 and 0.6 Ma. Bodies of coherent rhyolite occur at multiple stratigraphic levels: two magma types with associated tuffs were emplaced as domes and sills at 0.36 ± 0.03 Ma, and a third type at 0.138 ± 0.007 Ma as dikes, and domes that are exposed at surface. The andesitic Putauaki composite cone southwest of the field first erupted around 8 ka, but earlier hydrothermal eruption breccias imply that magma was intruded to shallow depths as early as ~ 16 ka. Age data and associated correlations show that post-1.5 Ma normal faulting has accompanied episodic subsidence of the Kawerau area, with fault movement focused between northeast-southwest structures (associated with the geometry of the modern TVZ) and the reactivated northwest-southeast structures associated with most displacement in the area prior to 1.5 Ma. Contrasts between emplacement of coherent rhyolite as sills at 0.36 Ma and a dike at 0.138 Ma reflect a shift in orientation of the principal stress axes in response to initiation of the modern TVZ rifting regime. Most volcanic rocks at Kawerau are distally sourced from elsewhere in the TVZ but form local marker horizons that delineate topographic relief within the field, and additionally constrain past subsidence rates. Current rates of subsidence and thermal output at Kawerau are geologically recent features associated with latest Quaternary rifting processes (< ~ 50 ka) and emplacement of the magmatic system for Putauaki volcano (~ 16 ka) respectively.

Milicich, S. D.; Wilson, C. J. N.; Bignall, G.; Pezaro, B.; Bardsley, C.

2013-07-01

308

Steam-electrical generating system using geothermal heat source  

SciTech Connect

A liquid-to-liquid heat pump is utilized for supplying sufficient heat to generate steam from the condensate of a steam turbine. A liquid coolant is circulated through the condenser of the steam turbine for absorption of heat from the steam as the steam forms condensate. The liquid coolant is then circulated through the heat pump for recovery of the heat absorbed by the coolant during condensation of the steam. Sufficient transferred heat is transferred to the coolant to permit the heat pump to extract sufficient heat from the coolant to regenerate steam from the condensate. The transferred heat is supplied by a plurality of heat sinks buried in the earth to a sufficient depth so as to be in heat exchange relationship with the subterranean water system of the earth.

Wolf, H.B.

1982-08-10

309

Numerical simulations to assess thermal potential at Tauranga low-temperature geothermal system, New Zealand  

NASA Astrophysics Data System (ADS)

Tauranga low-temperature geothermal system (New Zealand) has been used for the last 40 years for direct uses including space heating, bathing and greenhouses. Warm-water springs in the area are between 22 and 39 °C, with well temperatures up to 67 °C at 750 m depth. A heat and fluid flow model of the system is used to determine reservoir properties and assess thermal potential. The model covers 130 km by 70 km to 2 km depth, and was calibrated against temperatures measured in 17 wells. Modelling shows that to maintain the observed primarily conductive heat flow regime, bulk permeability is ?2.5 × 10-14 m2 in sedimentary cover and ?1 × 10-16 m2 in the underlying volcanic rocks. The preferred model (R 2 = 0.9) corresponds to thermal conductivities of 1.25 and 1.8 W/m2 for sedimentary and volcanic rocks, respectively, and maximum heat flux of 350 mW/m2. The total surface heat flow is 258 MW over 2,200 km2. Heat flux is highest under Tauranga City, which may be related to inferred geology. Model simulations give insights into rock properties and the dynamics of heat flow in this low-temperature geothermal system, and provide a basis to estimate the effects of extracting hot fluid.

Pearson, S. C. P.; Alcaraz, S. A.; Barber, J.

2013-12-01

310

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

DOE Data Explorer

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Jenna N. Schroeder

311

Enhanced Geothermal Systems (EGS) - Where Are We Now  

NASA Astrophysics Data System (ADS)

There were seven major EGS projects in which reservoir circulation was achieved prior to the Geodynamics Limited project in the Innamincka granite in northern South Australia which commenced in 2002. Six other projects did not achieve significant circulation. Importantly all but one of these projects were located in granitic bodies in which it is assumed that families of existing natural fractures are present. Evidence from all these EGS projects indicated that: 1 Stimulation in granite rock resulting from water injection with no added chemicals enhanced rock fracture permeability by 2-3 orders of magnitude. 2 The increased permeability resulted from increased fracture porosity associated with slippage on existing natural fractures during the stimulation. 3The extent of the resulting reservoir could be accurately mapped by acoustic (micro-seismic) monitoring of the fracture slippages. 4 The orientation of the reservoir is strongly dependent on the relative directions of the three principle rock stress axes. 5 The stimulation pumping pressures required were 50-75% of the minimum principle stress for the depth of reservoir creation in accord with geomechanical theory, and are therefore lower than those required to open tensile fractures (fracking). 6 The size of the resulting stimulated reservoir is proportional to the volume of water injected. New space created by the increase in fracture porosity associated with the micro-seismic events is taken up by the injected water. 7 Most projects to 2002 were carried out in strike-slip and normal faulting stress regimes with minimum stress direction horizontal and the resulting reservoirs were oriented close to vertically. 8 Volcanic activity can only occur in strike-slip and normal faulting stress regimes so EGS reservoirs in volcanic areas will be oriented close to vertically. 9 The Fjallbacka project in Sweden was the only project carried out in an overthrust stress regime (minimum stress direction vertical) and the reservoir was oriented horizontally. It is with these understandings that the Geodynamics field program commenced near Innamincka in 2002 where high temperature granite basement had been intersected at 3.6 km depth by petroleum exploration wells. Gravity and heat flow models indicated the basement granite to be 10 km thick and that most of the heat flow (> 100 mW/m2) was derived from elevated thorium and uranium levels in the granite. The stress environment was thought to be overthrust, but this was not certain.The results of the Geodynamics field program consists of drilling 5 wells to the granite, stimulation in three of those wells, flow testing in two of those wells and circulation between two of those wells. There are now four main barriers to economic deployment of EGS throughout the world for electricity generation. One is the cost of drilling and new technologies need to be developed to increase drilling ROP in high strength rocks. The other three relate to reservoir development and increased flow rate. These are (i) new geophysical tools to locate large fractures remotely (ii) deployment of temporary fracture sealing agents to allow enhancement in more than one fracture, and (iii) decreased flow impedance in a given fracture at the production well. New projects at different locations around the world are required to test ways of overcoming these barriers.

Wyborn, D.

2011-12-01

312

CO{sub 2} flux measurements across portions of the Dixie Valley geothermal system, Nevada  

SciTech Connect

A map of the CO{sub 2} flux across a newly formed area of plant kill in the NW part of the Dixie Valley geothermal system was constructed to monitor potential growth of a fumarole field. Flux measurements were recorded using a LI-COR infrared analyzer. Sample locations were restricted to areas within and near the dead zone. The data delineate two areas of high CO{sub 2} flux in different topographic settings. Older fumaroles along the Stillwater range front produce large volumes of CO{sub 2} at high temperatures. High CO{sub 2} flux values were also recorded at sites along a series of recently formed ground fractures at the base of the dead zone. The two areas are connected by a zone of partial plant kill and moderate flux on an alluvial fan. Results from this study indicate a close association between the range front fumaroles and the dead zone fractures. The goals of this study are to characterize recharge to the geothermal system, provide geochemical monitoring of reservoir fluids and to examine the temporal and spatial distribution of the CO{sub 2} flux in the dead zone. This paper reports the results of the initial CO{sub 2} flux measurements taken in October, 1997.

Bergfeld, D.; Goff, F. [Los Alamos National Lab., NM (United States). Earth and Environmental Sciences Div.; Janik, C.J. [Geological Survey, Menlo Park, CA (United States); Johnson, S.D. [Oxbow Power Services, Reno, NV (United States)

1998-12-31

313

Imperial County geothermal development. Quarterly report, April 1-June 30, 1982  

SciTech Connect

The activities of the Geothermal Office during the quarter are discussed, including: important geothermal events, geothermal waste disposal, a grant award by the California Energy Commission, the geothermal development meeting, and the current status of geothermal development in Imperial County. Activities of the Geothermal Planner are addressed, including permits, processing of EIR's, and other planning activities. Progress on the direct heat study is reported.

Not Available

1982-06-30

314

Characterization of medium enthalpy geothermal system in the Campania region (southern Italy): from geological data to resource modelling  

NASA Astrophysics Data System (ADS)

Within the framework of the VIGOR project, a characterization of medium enthalpy geothermal resources have been carried out in the Campania region (southern Italy), with a focus on the "Guardia dei Lombardi" area (province of Avellino). The VIGOR project began on the basis of an agreement between the Ministry of Economic Development and the Italian National Research Council, and it deal with the exploitation of innovative uses of geothermal energy in the so-called "regions of convergence"(Campania, Calabria, Puglia and Sicilia). Thanks to the intense hydrocarbon exploration, carried out particularly during the 1956-1996 period, an extensive data set made up by deep wells and seismic reflection profiles exist in the study area. The previous exploration demonstrated the presence of a fractured carbonate reservoir, mainly belonging to the Cretaceous section of the Apulian shallow water carbonate platform (e.g. Scrocca 2010 and references therein), which is deformed to shape a buried antiformal stack. The culmination of the uppermost thrust unit reaches a depth of about 200 m SSL (i.e., about 1100 m below the ground level). The reservoir fluids are made up by a CO2 gas cap, which rests above an accumulation of fresh water in the central and upper part of the culmination of the deep carbonatic acquifer (e.g., Monte Forcuso 1 and 2 wells), and a saline water along the flank of the buried anticline (e.g., Bonito 1 Dir, Ciccone 1 wells). Medium enthalpy geothermal resources with a reservoir fluid temperature up to 100°C have been estimated in previous assessments at depth of 2000 m below ground level (ENEL 1987; 1994). However, the presence of thermal springs (e.g. Terme di S. Teodoro) in the area suggests the presence of an active hydraulic circuit and provide further constraints about the geochemical characteristics of the reservoir waters, and the geothermometers investigation (Duchi et al. 1995) give a possible reservoir fluid temperature up to about 124 °C. In this study, the overall reservoir/caprock system structural-stratigraphic setting has been defined based on the integrated interpretation of surface geology, public and available seismic reflection profiles, and composite well logs. In particular, a careful assessment of temperature field at depth has been carried out analyzing the well logs through Horner plot construction (Rider, 1996 and reference therein). Where the temperature data data were scarce or poorly constrained, the approach proposed by Della Vedova, et al. (2001) has been applied. On the basis of well tests, cores and mud losses/absorptions, the reservoir permeability was also re-estimated, confirming quite good permeability values for the fractured carbonate reservoir. One of the main results of this research is the development of an integrated 3D geological model which provides the base for a detailed assessment of the possible geothermal exploitation of the carbonate reservoir. The preliminary results of our analysis suggest that "Guardia dei Lombardi" can be indicated as an interesting area for the geothermal medium enthalpy exploitation, although the presence of the CO2 gas cap and the scaling capability of the deep fluids should be carefully evaluated. From the 3D geological model, we put a sounding basis for a numerical model of hot fluid extraction (made by TOUGH/TOUGHREACT) in which some reasonable hypothesis on the reservoir exploitation may be evaluated.

Montegrossi, G.; Inversi, B.; Scrocca, D.; Livani, M.; Petracchini, L.

2012-04-01

315

High-precision relocation of induced seismicity in the geothermal system below St. Gallen (Switzerland)  

NASA Astrophysics Data System (ADS)

From July to November 2013 a sequence of more than 850 events, of which more than 340 could be located, was triggered in a planned hydrothermal system below the city of St. Gallen in eastern Switzerland. Seismicity initiated on July 14 and the maximum Ml in the sequence was 3.5, comparable in size with the Ml 3.4 event induced by stimulation below Basel in 2006. To improve absolute locations of the sequence, more than 1000 P and S wave arrivals were inverted for hypocenters and 1D velocity structure. Vp of 5.6-5.8 km/s and a Vp/Vs ratio of 1.82-1.9 in the source region indicate a limestone or shale-type composition and a comparison with a lithological model from a 3D seismic model suggests that the seismically active streak (height up to 400 m) is within the Mesozoic layer. To resolve the fine structure of the induced seismicity, we applied waveform cross-correlation and double-difference algorithms. The results image a NE-SW striking lineament, consistent with a left-lateral fault plane derived from first motion polarities and moment tensor inversions. A spatio-temporal analysis of the relocated seismicity shows that, during first acid jobs on July 17, microseismicity propagated towards southwest over the entire future Ml 3.5 rupture plane. The almost vertical focal plane associated with the Ml 3.5 event of July 20 is well imaged by the seismicity. The area of the ruptured fault is approximately 675x400 m. Seismicity images a change in focal depths along strike, which correlates with a kink or bend in the mapped fault system northeast of the Ml 3.5 event. This change might indicate structural differences or a segmentation of the fault. Following the Ml 3.5 event, seismicity propagated along strike to the northeast, in a region without any mapped faults, indicating a continuation of the fault segment. Seismicity on this segment occurred in September and October. A complete rupture of the NE segment would have the potential to produce a magnitude larger than 3.0. Similarity of waveforms suggests that an Ml 3.2 in 1987 and an Ml 2.2 event in 1993 occurred on a similar structure with a similar slip direction as the Ml 3.5 event. It appears that the fault zone targeted by the geothermal project is not only oriented favourably for rupture relative to the regional stress field, but is also close to failure.

Diehl, Tobias; Kraft, Toni; Eduard, Kissling; Nicholas, Deichmann; Clinton, John; Wiemer, Stefan

2014-05-01

316

Performance enhancement of a thermally activated cooling system using microchannel heat exchangers  

Microsoft Academic Search

In the current study a thermally activated cooling system that combines an ORC system with a vapor compression cooling cycle was developed and tested under laboratory conditions. This combined system can utilize waste heat or other thermal sources such as solar and geothermal to generate power and cooling. Hot oil with temperature up to 200 °C was used as the simulated

Hailei Wang; Richard B. Peterson

2011-01-01

317

Local influences of geothermal anomalies on permafrost distribution in an active volcanic island (Deception Island, Antarctica)  

NASA Astrophysics Data System (ADS)

This study aims at understanding the spatial distribution and characteristics of the frozen and unfrozen terrain in an alluvial fan on Deception Island, which is an active strato-volcano located in the Bransfield Strait (South Shetland Islands) with recent eruptions in 1967, 1969 and 1970. The alluvial fan is dominated by debris-flow, run-off and rock fall processes and permafrost occurs in several parts in the vicinity of anomalous geothermal heat flux. The aim is to assess the ways volcanic activity controls permafrost development and associated geomorphic dynamics using shallow subsurface, surface and air temperature measurements as well as thaw depth and electrical resistivity tomography (ERT) surveys. Results show a temperature increase with depth in the lower part of the fan reaching 13 °C at 0.80 m depth, without the presence of permafrost. The shallow borehole located at this site showed a stable thermal stratification all year-round, with only the upper 0.20 m reacting to meteorological forcing. In the upper part of the alluvial fan and debris cones, c. 100 m from the coast, frozen ground is present at c. 0.70 m depth. There, the shallow borehole shows a good coupling with air temperatures and the thermal regime favours the presence of permafrost. ERT shows the lowest resistivity values in the lower part of the alluvial fan and a highly resistivity zone in the upper sector of the fan and in the debris cones. These large variations in resistivity mark the presence of a saline water wedge from the sea into the fan, reaching frozen ground conditions about 100 m inland. It can be shown that the volcano-hydrothermal activity only inhibits frost development very locally, with frozen ground conditions occurring about 100 m away.

Goyanes, G.; Vieira, G.; Caselli, A.; Cardoso, M.; Marmy, A.; Santos, F.; Bernardo, I.; Hauck, C.

2014-11-01

318

Using Electromagnetic Techniques to Test Models for Shallow Permeability in the Surprise Valley, CA Geothermal System  

NASA Astrophysics Data System (ADS)

Surprise Valley in northeastern Modoc County, CA is the westernmost major extensional graben in the northwestern Basin and Range province. There are abundant faults coincident with moderate to boiling temperature hot springs that discharge along the western rim of the valley and in the central eastern part of the valley. Fluid recharge and discharge pathways are poorly understood despite sporadic geothermal exploration, drilling, and development since the 1950's and a wide variety of academic studies that have been focused in the region. It is hypothesized that thermal fluids discharged into the basin exploit fracture permeability related to active extensional faulting along the Surprise Valley Fault (SVF), Lake City Fault Zone (LCFZ), and faults in the Hays Canyon Range (HCR). We present several fault-perpendicular Magnetotelluric profiles conducted across the LCFZ and HCR faults with the goal of imaging the orientation and extent of the geothermal reservoir that supplies the hot springs. Initial results are consistent with the HCR faults tapping a deep conductive aquifer below shallow resistive extrusive igneous rocks, with narrow low resistivity regions beneath the faults. There is no conclusive evidence for or against the LCFZ acting as a preferred fluid pathway, due to relatively homogeneous distribution highly conductive materials and the difficulty in differentiating clay-rich lacustrine sediments from hydrothermal fluids or clays.

Hawkes, S.; McClain, J. S.; Kahn, A.; Lewis, K.

2013-12-01

319

Geothermal chemical engineering  

Microsoft Academic Search

Programs, projects, and research for utilization of geothermal energy are reviewed from a chemical engineering vantage point, with attention given to costs, proved resources, reservoir models, applications, and environmental impact. Neglect of crucial chemical reactions occurring in geothermal systems impair the usefulness of existing models constructed for hydrothermal reservoirs. Currently entertained models, studies of reservoir mechanics and ground water hydrology,

R. C. Axtmann; L. B. Peck

1976-01-01

320

An efficient finite volume model for shallow geothermal systems. Part I: Model formulation  

NASA Astrophysics Data System (ADS)

This series of two papers presents a three-dimensional finite volume model for shallow geothermal systems. In this part, an efficient computational model describing heat and fluid flow in ground-source heat pumps is formulated. The physical system is decomposed into two subdomains, one representing a soil mass, and another representing one or a set of borehole heat exchangers. Optimization of the computational procedure has been achieved by, first, using a pseudo three-dimensional line element for modeling the borehole heat exchanger, and second, using a combination of a locally refined Cartesian grid and a multigrid with hierarchal tree data structure for discretizing and solving the soil mass governing equations. This optimization made the model computationally efficient and capable of simulating multiple borehole heat exchangers embedded in a multilayer system, in relatively short CPU time. In Part II of this series, verifications and numerical examples describing the computational capabilities of the model are presented.

Nabi, M.; Al-Khoury, R.

2012-12-01

321

Comparing FRACHEM and TOUGHREACT for reactive transport modelingof brine-rock interactions in enhanced geothermal systems (EGS)  

SciTech Connect

Coupled modelling of fluid flow and reactive transport ingeothermal systems is challenging because of reservoir conditions such ashigh temperatures, elevated pressures and sometimes high salinities ofthe formation fluids. Thermal hydrological-chemical (THC) codes, such asFRACHEM and TOUGHREACT, have been developed to evaluate the long-termhydrothermal and chemical evolution of exploited reservoirs. In thisstudy, the two codes were applied to model the same geothermal reservoir,to forecast reservoir evolution using respective thermodynamic andkinetic input data. A recent (unreleased) TOUGHREACT version allows theuse of either an extended Debye-Hu?ckel or Pitzer activity model forcalculating activity coefficients, while FRACHEM was designed to use thePitzer formalism. Comparison of models results indicate that differencesin thermodynamic equilibrium constants, activity coefficients andkinetics models can result in significant differences in predictedmineral precipitation behaviour and reservoir-porosity evolution.Differences in the calculation schemes typically produce less differencein model outputs than differences in input thermodynamic and kineticdata, with model results being particularly sensitive to differences inion-interaction parameters for highsalinity systems.

Andre, L.; Spycher, N.; Xu, T.; Pruess, K.; Vuataz, F.-D.

2005-11-15

322

Microbiological Monitoring in Geothermal Plants  

NASA Astrophysics Data System (ADS)

In the scope of the research projects “AquiScreen” and “MiProTherm” we investigated geothermally used groundwater systems under microbial, geochemical, mineralogical and petrological aspects. On one side an enhanced process understanding of engineered geothermal systems is mandatory to optimize plant reliability and economy, on the other side this study provides insights into the microbiology of terrestrial thermal systems. Geothermal systems located in the North German Basin and the Molasse Basin were analyzed by sampling of fluids and solid phases. The investigated sites were characterized by different temperatures, salinities and potential microbial substrates. The microbial population was monitored by the use of genetic fingerprinting techniques and PCR-cloning based on PCR-amplified 16S rRNA and dissimilatory sulfite reductase (DSR) genes. DNA-sequences of fingerprints and cloned PCR-products were compared to public databases and correlated with metabolic classes to provide information about the biogeochemical processes. In all investigated geothermal plants, covering a temperature range from 5° to 120°C, microorganisms were found. Phylogenetic gene analyses indicate a broad diversity of microorganisms adapted to the specific conditions in the engineered system. Beside characterized bacteria like Thermus scotoductus, Siderooxidans lithoautotrophicus and the archaeon Methanothermobacter thermoautotrophicus a high number of so far uncultivated microorganisms was detected. As it is known that - in addition to abiotic factors - microbes like sulfate-reducing bacteria (SRB) are involved in the processes of corrosion and scaling in plant components, we identified SRB by specific analyses of DSR genes. The SRB detected are closely related to thermotolerant and thermophilic species of Desulfotomaculum, Thermodesulfovibrio, Desulfohalobium and Thermodesulfobacterium, respectively. Overall, the detection of microbes known to be involved in biocorrosion and the examined precipitation products like iron sulfides are indicating that microorganisms play an important role for the understanding of processes in engineered geothermal systems. The further identification of crucial process parameters influencing microbial activities will help to develop appropriate counter measures against microbial induced clogging and corrosion.

Alawi, M.; Lerm, S.; Linder, R.; Vetter, A.; Vieth-Hillebrand, A.; Miethling-Graff, R.; Seibt, A.; Wolfgramm, M.; Wuerdemann, H.

2010-12-01

323

Microbiological Aspects of Geothermal Energy: Influence of Microbial Activity on Scaling and Clogging in a Cold Storage  

NASA Astrophysics Data System (ADS)

The development of strategies to substantially reduce emission of greenhouse gases to the atmosphere is one of the major challenges of the next decades. Therefore, the utilization of subsurface stored energy arouses increasing interest. Corrosion and scaling are major problems in geothermal operation which create significant maintenance and cleaning costs. In the scope of the research project AquiScreen the operational reliability of geothermal used aquifer systems was investigated under microbial, geochemical, mineralogical, and petrologic aspects (see also Alawi et al.; General Assembly EGU 2010). This presentation focuses on the investigation of a cold storage in Berlin (Reichstag building, depth 30-50 m). In order to evaluate the impact of microbial processes in the low saline aquifer (see also Vetter et al.; General Assembly EGU 2010), the microbial communities of fluid and filter samples were investigated by Fluorescent in situ hybridization (FISH) and DNA fingerprinting techniques based on PCR amplified partial 16S rRNA genes. Analyses of fluid samples revealed a bacterial community dominated by iron and sulfur oxidizing bacteria closely related to Siderooxidans lithoautotrophicus, Gallionella sp. and Thiotrix unzii. Scanning electron microscope analysis revealed iron hydroxide formation and precipitation in the filter of the top side facility and the well, corresponding to the abundance of iron oxidizing bacteria. Besides oxidizing bacteria sulfate reducing bacteria (SRB) were detected as well, indicating the formation of micro-habitats with divergent redox zones. After several years of operation and routine maintenance procedures the injectivity of the injection wells and the endurance of the top side facility filters were reduced drastically due to clogging. Mechanical cleaning and a disinfection treatment with hydrogen peroxide (H2O2) were successful to re-establish the injectivity of the wells. The results of the microbiological investigations prove that bacteria and their metabolic activities were involved in the decrease of filter endurances. A strong biofilm formation of filamentous sulfur-oxidizing bacteria related to Thiothrix was observed. In the course of the disinfection measure the microbial composition in the process water changed significantly. Thiothrix could not be detected any longer and the biocoenosis in the fluid was dominated now by Flavobacterium, Acidovorax as well as Alcaligenaceae related organisms. In contrast, SRB analyzed by specific dissimilatory sulfite reductase genes were hardly affected by the disinfection measures. However, even if especially SRB are considered as the most important taxonomic group for microbiologically influenced corrosion (MIC), present operational results indicate that scaling and clogging were the predominant processes for the operation of the shallow cold storage in Berlin.

Lerm, Stephanie; Alawi, Mashal; Miethling-Graff, Rona; Vieth, Andrea; Seibt, Andrea; Wolfgramm, Markus; Würdemann, Hilke

2010-05-01

324

Active Management of Integrated Geothermal-CO2 Storage Reservoirs in Sedimentary Formations  

DOE Data Explorer

The purpose of phase 1 is to determine the feasibility of integrating geologic CO2 storage (GCS) with geothermal energy production. Phase 1 includes reservoir analyses to determine injector/producer well schemes that balance the generation of economically useful flow rates at the producers with the need to manage reservoir overpressure to reduce the risks associated with overpressure, such as induced seismicity and CO2 leakage to overlying aquifers. Based on a range of well schemes, techno-economic analyses of the levelized cost of electricity (LCOE) are conducted to determine the economic benefits of integrating GCS with geothermal energy production. In addition to considering CO2 injection, reservoir analyses are conducted for nitrogen (N2) injection to investigate the potential benefits of incorporating N2 injection with integrated geothermal-GCS, as well as the use of N2 injection as a potential pressure-support and working-fluid option. Phase 1 includes preliminary environmental risk assessments of integrated geothermal-GCS, with the focus on managing reservoir overpressure. Phase 1 also includes an economic survey of pipeline costs, which will be applied in Phase 2 to the analysis of CO2 conveyance costs for techno-economics analyses of integrated geothermal-GCS reservoir sites. Phase 1 also includes a geospatial GIS survey of potential integrated geothermal-GCS reservoir sites, which will be used in Phase 2 to conduct sweet-spot analyses that determine where promising geothermal resources are co-located in sedimentary settings conducive to safe CO2 storage, as well as being in adequate proximity to large stationary CO2 sources.

Thomas A. Buscheck

325

Session 1: Geothermal Pumping Systems and Two-Phase Flow Studies  

SciTech Connect

Improvements in electric submersible pumping systems have resulted in a demonstrated downhole running life of one year for low horsepower units operating in 180 C brine. The implementation of a prototype pressurized lubrication system to prevent brine intrusion and loss of lubricating oil from the motor and protector sections has been successfully tested. Second generation pressurized lubrication systems have been designed and fabricated and will be utilized in downhole production pumping tests during FY84. Pumping system lifetime is currently limited by available power cable designs that are degraded by high-temperature brine. A prototype metal-sheathed power cable has been designed and fabricated and is currently undergoing destructive and nondestructive laboratory testing. This cable design has the potential for eliminating brine intrusion into the power delivery system through the use of a hermatically sealed cable from the surface to the downhole motor. The two-phase flow program is directed at understanding the hydrodynamics of two-phase flows. The two-phase flow regime is characterized by a series of flow patterns that are designated as bubble, slug, churn, and annular flow. Churn flow has received very little scientific attention. This lack of attention cannot be justified because calculations predict that the churn flow pattern will exist over a substantial portion of the two-phase flow zone in producing geothermal wells. The University of Houston is experimentally investigating the dynamics of churn flow and is measuring the holdup over the full range of flow space for which churn flow exists. These experiments are being conducted in an air/water vertical two-phase flow loop. Brown University has constructed and is operating a unique two-phase flow research facility specifically designed to address flow problems of relevance to the geothermal industry. An important feature of the facility is that it is dedicated to two-phase flow of a single substance (including evaporation and condensation) as opposed to the case of a two-component two-phase flow. This facility can be operated with horizontal or vertical test sections of constant diameter or with step changes in diameter to simulate a geothermal well profile.

Hanold, R.J.

1983-12-01

326

Evaluation of materials for systems using cooled, treated geothermal or high-saline brines  

NASA Astrophysics Data System (ADS)

Lack of adequate quantities of clean surface water for use in wet (evaporative) cooling systems indicates the use of high-salinity waste waters, or cooled geothermal brines, for makeup purposes. High-chloride, aerated water represents an extremely corrosive environment. In order to determine metals suitable for use in such an environment, metal coupons were exposed to aerated, treated geothermal brine salted to a chloride concentration of 10,000 and 50,000 ppM (mg/L) for periods of up to 30 days. The exposed coupons were evaluated to determine the general, pitting, and crevice corrosion characteristics of the metals. Results indicate that ferritic stainless steels (29-4-2 and SEACURE) exhibit excellent corrosion resistance at all levels of chloride concentration. Copper-nickel alloys (70/30 and Monel 400) exhibited excellent corrosion resistance in the high-saline water. The 70/30 copper-nickel alloy, which showed excellent resistance to general corrosion, exhibited mild pitting in the 30-day tests.

Suciu, D. F.; Wikoff, P. M.

1982-09-01

327

The effect of CO{sub 2} on reservoir behavior for geothermal systems  

SciTech Connect

The purpose was to gain an understanding of the effects of non-condensible gases (CO/sub 2/) in fractured two-phase geothermal systems. A thorough review of previous work on non-condensible gases was carried out. In addition, since the flowing mass fraction of CO/sub 2/ is strongly controlled by the flowing saturation, the flowing enthalpy literature was also reviewed. Numerical techniques were employed to examine how non-condensible gases (CO/sub 2/) affect well transients and to determine the value of these effects as tools to evaluate in situ reservoir parameters. Simplified reservoir models were used to define the effects of CO/sub 2/ in the reservoir and the resulting transient behavior at the feedzones to the well. Furthermore, fracture-matrix interaction was studied in detail to identify the effects of CO/sub 2/ on recovery and flow patterns within the reservoir. The insight gained from the sensitivity studies for enthalpy and CO/sub 2/ transients was applied to interpret transient data from well BR21 at the Broadlands geothermal field of New Zealand.

Gaulke, S.W.

1986-12-01

328

Potential impacts of artificial intelligence expert systems on geothermal well drilling costs:  

SciTech Connect

The Geothermal research Program of the US Department of Energy (DOE) has as one of its goals to reduce the cost of drilling geothermal wells by 25 percent. To attain this goal, DOE continuously evaluates new technologies to determine their potential in contributing to the Program. One such technology is artifical intelligence (AI), a branch of computer science that, in recent years, has begun to impact the marketplace in a number of fields. Expert systems techniques can (and in some cases, already have) been applied to develop computer-based ''advisors'' to assist drilling personnel in areas such as designing mud systems, casing plans, and cement programs, optimizing drill bit selection and bottom hole asssembly (BHA) design, and alleviating lost circulation, stuck pipe, fishing, and cement problems. Intelligent machines with sensor and/or robotic directly linked to AI systems, have potential applications in areas of bit control, rig hydraulics, pipe handling, and pipe inspection. Using a well costing spreadsheet, the potential savings that could be attributed to each of these systems was calculated for three base cases: a dry steam well at The Geysers, a medium-depth Imerial Valley well, and a deep Imperial Valley well. Based on the average potential savings to be realized, expert systems for handling lost circulations problems and for BHA design are the most likely to produce significant results. Automated bit control and rig hydraulics also exhibit high potential savings, but these savings are extremely sensitive to the assumptions of improved drilling efficiency and the cost of these sytems at the rig. 50 refs., 19 figs., 17 tabs.

Satrape, J.V.

1987-11-24

329

Changes in fluid geochemistry and physico-chemical conditions of geothermal systems caused by magmatic input: The recent abrupt outgassing off the island of Panarea (Aeolian Islands, Italy)  

NASA Astrophysics Data System (ADS)

Hydrothermal systems and related vents can exhibit dramatic changes in their physico-chemical conditions over time as a response to varying activity in the feeding magmatic systems. Massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system. Here we propose a new stability diagram based on the CO 2-CH 4-CO-H 2 concentrations in vapor, which aims at calculating the temperatures and pressures in hydrothermal reservoirs. To filter gas scrubbing effects, we have also developed a model for selective dissolution of CO 2-H 2S-N 2-CH 4-He-Ne mixtures in fresh and/or air-saturated seawater. This methodology has been applied to the recent (November 2002) crisis that affected the geothermal field off the island of Panarea (Italy), where the fluid composition and fluxes have been monitored for the past two decades. The chemical and isotopic compositions of the gases suggest that the volatile elements originate from an active magma, which feeds a boiling saline solution having temperatures of up to 350°C and containing ?12 mol% CO 2 in vapor. The thermal fluids undergo cooling and re-equilibration processes on account of gas-water-rock interactions during their ascent along fracture networks. Furthermore, steam condensation and removal of acidic species, partial dissolution in cold air-saturated seawater and stripping of atmospheric components, affect the composition of the geothermal gases at shallow levels. The observed geochemical variations are consistent with a new input of magmatic fluids that perturbed the geothermal system and caused the unrest event. The present-state evolution shows that this dramatic input of fluids is probably over, and that the system is now tending towards steady-state conditions on a time scale of months.

Caracausi, A.; Ditta, M.; Italiano, F.; Longo, M.; Nuccio, P. M.; Paonita, A.; Rizzo, A.

2005-06-01

330

Geochemical Monitoring of Geothermal Waters (2002–2004) along the North Anatolian Fault Zone, Turkey: Spatial and Temporal Variations and Relationship to Seismic Activity  

Microsoft Academic Search

A total of nine geothermal fields located along an 800-km long E-W transect of the North Anatolian Fault Zone (NAFZ), Turkey\\u000a were monitored for three years (2002–2004 inclusive; 3-sampling periods per year) to investigate any possible relationship\\u000a between seismic activity and temporal variations in the chemistry and isotope characteristics of waters in the fields. The\\u000a geothermal fields monitored in the

Selin Süer; Nilgün Güleç; Halim Mutlu; David R. Hilton; Candan Çifter; Mesut Sayin

331

Geochemical Monitoring of Geothermal Waters (2002–2004) along the North Anatolian Fault Zone, Turkey: Spatial and Temporal Variations and Relationship to Seismic Activity  

Microsoft Academic Search

A total of nine geothermal fields located along an 800-km long E-W transect of the North Anatolian Fault Zone (NAFZ), Turkey\\u000a were monitored for three years (2002–2004 inclusive; 3-sampling periods per year) to investigate any possible relationship\\u000a between seismic activity and temporal variations in the chemistry and isotope characteristics of waters in the fields. The\\u000a geothermal fields monitored in the

Selin Süer; Nilgün Güleç; Halim Mutlu; David R. Hilton; Candan Çifter; Mesut Sayin

2008-01-01

332

Thermally induced seawater intrusion in the coastal aquifers of the Seferihisar-Balçova Geothermal system, Western Anatolia, Turkey - results from thermohaline simulations  

Microsoft Academic Search

The Seferihisar-Balçova Geothermal system (SBG), Western Anatolia, Turkey, is characterized by complex temperature and hydrochemical anomalies which causes are not fully understood. Heated groundwater types with low total dissolved solids (TDS) content are found in the Balçova geothermal field whereas the thermal waters in the Ürkmez area, southern SBG, originated from a mixture of seawater and local meteoric groundwater. Previous

Fabien Magri; Toygar Akar; Asaf Pekdeger; Ünsal Gemici

2010-01-01

333

Assessment of the State-Of-The-Art of Numerical Simulation of Enhanced Geothermal Systems  

SciTech Connect

The reservoir features of importance in the operation of enhanced geothermal systems are described first (Section 2). The report then reviews existing reservoir simulators developed for application to HDR reservoirs (Section 3), hydrothermal systems (Section 4), and nuclear waste isolation (Section 5), highlighting capabilities relevant to the evaluation and assessment of EGS. The report focuses on simulators that include some representation of flow in fractures, only mentioning other simulators, such as general-purpose programs or groundwater models (Section 6). Following these detailed descriptions, the report summarizes and comments on the simulators (Section 7), and recommends a course of action for further development (Section 8). The references are included in Section 9. Appendix A contains contractual information, including a description of the original and revised scope of work for this study. Appendix B presents comments on the draft report from DOE reviewer(s) and the replies of the authors to those comments. [DJE-2005

None

1999-11-01

334

Evolution of the thermal cap in two wells from the Salton Sea geothermal system, California  

SciTech Connect

The Salton Sea geothermal system is overlain by a thermal cap of low permeability rocks that restricts the upward movement of the high-temperature reservoir brines. Petrographic and fluid inclusion data from two wells show that the thermal cap in the southern part of the field consists of an upper layer of lacustrine and evaporite deposits with low initial permeabilities and a lower layer of deltaic sandstones. The sandstones were incorporated into the thermal cap as downward percolating fluids deposited anhydrite and calcite in the pore space of the rocks, reducing their permeabilities. During development of the thermal cap, base-metal sulfides, potassium feldspar and quartz veins were deposited by brines from higher temperature portions of the system.

Moore, Joseph N.; Adams, Michael C.

1988-01-01

335

Enhanced Geothermal Systems Research and Development: Models of Subsurface Chemical Processes Affecting Fluid Flow  

SciTech Connect

Successful exploitation of the vast amount of heat stored beneath the earth’s surface in hydrothermal and fluid-limited, low permeability geothermal resources would greatly expand the Nation’s domestic energy inventory and thereby promote a more secure energy supply, a stronger economy and a cleaner environment. However, a major factor limiting the expanded development of current hydrothermal resources as well as the production of enhanced geothermal systems (EGS) is insufficient knowledge about the chemical processes controlling subsurface fluid flow. With funding from past grants from the DOE geothermal program and other agencies, we successfully developed advanced equation of state (EOS) and simulation technologies that accurately describe the chemistry of geothermal reservoirs and energy production processes via their free energies for wide XTP ranges. Using the specific interaction equations of Pitzer, we showed that our TEQUIL chemical models can correctly simulate behavior (e.g., mineral scaling and saturation ratios, gas break out, brine mixing effects, down hole temperatures and fluid chemical composition, spent brine incompatibilities) within the compositional range (Na-K-Ca-Cl-SO4-CO3-H2O-SiO2-CO2(g)) and temperature range (T < 350°C) associated with many current geothermal energy production sites that produce brines with temperatures below the critical point of water. The goal of research carried out under DOE grant DE-FG36-04GO14300 (10/1/2004-12/31/2007) was to expand the compositional range of our Pitzer-based TEQUIL fluid/rock interaction models to include the important aluminum and silica interactions (T < 350°C). Aluminum is the third most abundant element in the earth’s crust; and, as a constituent of aluminosilicate minerals, it is found in two thirds of the minerals in the earth’s crust. The ability to accurately characterize effects of temperature, fluid mixing and interactions between major rock-forming minerals and hydrothermal and/or injected fluids is critical to predict important chemical behaviors affecting fluid flow, such as mineral precipitation/dissolution reactions. We successfully achieved the project goal and objectives by demonstrating the ability of our modeling technology to correctly predict the complex pH dependent solution chemistry of the Al3+ cation and its hydrolysis species: Al(OH)2+, Al(OH)2+, Al(OH)30, and Al(OH)4- as well as the solubility of common aluminum hydroxide and aluminosilicate minerals in aqueous brines containing components (Na, K, Cl) commonly dominating hydrothermal fluids. In the sodium chloride system, where experimental data for model parameterization are most plentiful, the model extends to 300°C. Determining the stability fields of aluminum species that control the solubility of aluminum-containing minerals as a function of temperature and composition has been a major objective of research in hydrothermal chemistry.

Moller, Nancy; Weare J. H.

2008-05-29

336

Thermal and hydrochemical anomalies due to large-scale thermohaline convection in Seferihisar-Balçova Geothermal system, Western Anatolia, Turkey  

Microsoft Academic Search

The Seferihisar-Balçova Geothermal system (SBG), Western Anatolia, Turkey, is characterized by complex temperature and hydrochemical anomalies which causes are not fully understood. Previous geophysical investigations suggested that hydrothermal convection in the faulted areas of the SBG and recharge flow from the Horst may be possible transport mechanisms underlying the observed patterns. A numerical model of thermohaline flow along a North-South

F. Magri; A. Pekdeger; Gemici; T. Akar

2009-01-01

337

A comparative study on exergetic assessment of two ground-source (geothermal) heat pump systems for residential applications  

Microsoft Academic Search

Ground source heat pumps (GSHPs), also known as geothermal heat pumps (GHPs), have been widely used for years in developed countries due to their higher energy utilization efficiencies than those of both conventional heating and cooling systems. However, they have been applied to the Turkish residential buildings since 1997.This study deals with the exergetic performance evaluation of two types of

Ebru Kavak Akpinar; Arif Hepbasli

2007-01-01

338

Interactive Maps from the Great Basin Center for Geothermal Energy  

DOE Data Explorer

The Great Basin Center for Geothermal Energy, part of the University of Nevada, Reno, conducts research towards the establishment of geothermal energy as an economically viable energy source within the Great Basin. The Center specializes in collecting and synthesizing geologic, geochemical, geodetic, geophysical, and tectonic data, and using Geographic Information System (GIS) technology to view and analyze this data and to produce favorability maps of geothermal potential. The interactive maps are built with layers of spatial data that are also available as direct file downloads (see DDE00299). The maps allow analysis of these many layers, with various data sets turned on or off, for determining potential areas that would be favorable for geothermal drilling or other activity. They provide information on current exploration projects and leases, Bureau of Land Management land status, and map presentation of each type of scientific spatial data: geothermal, geophysical, geologic, geodetic, groundwater, and geochemical.

339

Life Cycle Water Consumption and Water Resource Assessment for Utility-Scale Geothermal Systems: An In-Depth Analysis of Historical and Forthcoming EGS Projects  

SciTech Connect

This report is the third in a series of reports sponsored by the U.S. Department of Energy Geothermal Technologies Program in which a range of water-related issues surrounding geothermal power production are evaluated. The first report made an initial attempt at quantifying the life cycle fresh water requirements of geothermal power-generating systems and explored operational and environmental concerns related to the geochemical composition of geothermal fluids. The initial analysis of life cycle fresh water consumption of geothermal power-generating systems identified that operational water requirements consumed the vast majority of water across the life cycle. However, it relied upon limited operational water consumption data and did not account for belowground operational losses for enhanced geothermal systems (EGSs). A second report presented an initial assessment of fresh water demand for future growth in utility-scale geothermal power generation. The current analysis builds upon this work to improve life cycle fresh water consumption estimates and incorporates regional water availability into the resource assessment to improve the identification of areas where future growth in geothermal electricity generation may encounter water challenges.

Jenna N. Schroeder

2013-08-31

340

Life Cycle Water Consumption and Water Resource Assessment for Utility-Scale Geothermal Systems: An In-Depth Analysis of Historical and Forthcoming EGS Projects  

DOE Data Explorer

This report is the third in a series of reports sponsored by the U.S. Department of Energy Geothermal Technologies Program in which a range of water-related issues surrounding geothermal power production are evaluated. The first report made an initial attempt at quantifying the life cycle fresh water requirements of geothermal power-generating systems and explored operational and environmental concerns related to the geochemical composition of geothermal fluids. The initial analysis of life cycle fresh water consumption of geothermal power-generating systems identified that operational water requirements consumed the vast majority of water across the life cycle. However, it relied upon limited operational water consumption data and did not account for belowground operational losses for enhanced geothermal systems (EGSs). A second report presented an initial assessment of fresh water demand for future growth in utility-scale geothermal power generation. The current analysis builds upon this work to improve life cycle fresh water consumption estimates and incorporates regional water availability into the resource assessment to improve the identification of areas where future growth in geothermal electricity generation may encounter water challenges.

Jenna N. Schroeder

341

The Coso geothermal area: A laboratory for advanced MEQ studies for geothermal monitoring  

USGS Publications Warehouse

The permanent 16-station network of three-component digital seismometers at the Coso geothermal area, California, supplemented by 14 temporary instruments deployed in connection with the DOE Enhanced Geothermal Systems (EGS) Project, provides high-quality microearthquake (MEQ) recordings that are well suited to monitoring a producing geothermal area. We are currently using these data to investigate structure and active processes within the geothermal reservoir by applying three advanced methods: a) high-precision MEQ hypocenter location; b) time-dependent tomography; c) complete (moment tensor) MEQ source mechanism determination. Preliminary results to date resolve seismogenic structures in the producing field more clearly than is possible with conventional earthquake-location techniques. A shallow part of the producing field shows clear changes in the ratio of the seismic wave speeds, Vp/V s, between 1996 and 2002, which are probably related to physical changes in the reservoir caused by fluid extraction.

Julian, B.R.; Foulger, G.R.; Richards-Dinger, K.

2004-01-01

342

Geothermal activity and energy of the Yakedake volcano, Gifu-Nagano, Japan  

SciTech Connect

The temperature of the most active solfatara in the summit crater of the Yakedake volcano (altitude 2,455 m Gifu-Nagano, Japan) was 92.2 and 129.4{degrees}C in September 1995 and in October 1994, respectively. The temperature of solfatara in the northern summit dome at an altitude of 2,240 to 2,270 m ranged from 68.2 to 92.5{degrees}C in September 1995. The water sample from a crater pond, Shoga-ike, located on the summit, showed a pH and electrical conductivity of 4.38 and 42.2 {mu}S/cm in October 1991, 4.35 and 42.4 {mu}S/cm in September 1992, 4.11 and 76.6 {mu}S/cm in October 1994, and 4.30 and 45.1 {mu}S/cm in September 1995, respectively. In 1960, the water sample from the same pond showed the pH and electrical conductivity of 3.7 and 80.8 {mu}S/cm, respectively. Although the values of pH and electrical conductivity in 1994 approached to the values at the volcano`s pre-eruption in 1960, the eruption in the summit dome did not occur in 1995. However, a large steam explosion occurred in the Nakanoyu area of the southeastern Mountainside of the volcano. The geothermal energy within the summit dome at an altitude of 2,050 to 2,455 m of the Yakedake volcano is calculated, using new data, to be about 4.8 x 10{sup 17} J, which represents a thermal power output of 5.1 x 10{sup 2} MW{sub th} averaged over 30 yrs.

Iriyama, Jun [Chuba Univ., Aichi (Japan)

1996-12-31

343

PROCEEDINGS, Thirty-Sixth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, January 31 -February 2, 2011  

E-print Network

and Resources SA, Petroleum and Geothermal Group GPO Box 1671 Adelaide, SA, 5000, Australia e-mail: alexandra System (EGS) and Hot Sedimentary Aquifer (HSA) ventures. With no active extensional regimes generating high-permeability systems of fluid-borne crustal heat, commercially-viable geothermal systems

Stanford University

344

Rock-water interactions in the Fenton Hill, New Mexico, hot dry rock geothermal systems; Modeling geochemical behavior  

SciTech Connect

A transient mass balance model is developed to account for the dynamic behavior of an artificially stimulated hot dry rock (HDR) geothermal reservoir system in fractured granitic rock. Fluid mixing between fractured zones, hydrodynamic dispersion within zones, pore fluid displacement, and mineral dissolution effects are incorporated into the model. A two-zone system is sufficient to account for the major observed results from field testing of the Fenton Hill HDR system.

Grigsby, C.O.; Tester, J.W. (Dept. of Chemical Engineering, Massachusetts Inst. of Technology, Cambridge, MA (US))

1989-01-01

345

Geothermal energy - an old concept with a new importance  

SciTech Connect

A general discussion of geothermal energy is presented. The different kinds of geothermal systems are identified and discussed, and geothermal resources are discussed. The methods of geothermal exploration are discussed, as are the techniques and necessity of reservoir evaluation. The economic aspects of geothermal energy are discussed. 5 references.

Downing, R.A.

1982-01-01

346

Novel thermophilic sulfate-reducing bacteria from a geothermally active underground mine in Japan.  

PubMed

Thermophilic sulfate-reducing bacteria were enriched from samples obtained from a geothermal underground mine in Japan. The enrichment cultures contained bacteria affiliated with the genera Desulfotomaculum, Thermanaeromonas, Thermincola, Thermovenabulum, Moorella, "Natronoanaerobium," and Clostridium. Two novel thermophilic sulfate-reducing strains, RL50JIII and RL80JIV, affiliated with the genera Desulfotomaculum and Thermanaeromonas, respectively, were isolated. PMID:16672530

Kaksonen, Anna H; Plumb, Jason J; Robertson, Wendy J; Spring, Stefan; Schumann, Peter; Franzmann, Peter D; Puhakka, Jaakko A

2006-05-01

347

Geothermal Recovery System Using Natural Circulating CO2 as A Heat Transfer Fluid  

NASA Astrophysics Data System (ADS)

In the conventional system, heat is recovered as sensible heat through liquid anti-freezer circulating in a piping laid underground, but if CO2 is used as a heat transfer fluid, heat is recovered as latent heat which increases the capacity and enables to promote downsize of the equipment and reduction of the electric consumption. It also enables the diameter or the length of heat recovery piping for the same heat exchange performance, thus the installation cost of the piping would be reduced. In our study, a geothermal recovery system using CO2 for air-conditioning was installed, and the heating capacity and the electric consumption were measured. Also, those of a conventional propylene-glycol system were measured. As a result, the CO2-system exerted the same heating ability with the propylene-glycol system with a half length of heat recovery piping and a half electric consumption of the propylene-glycol system. And the reduction in the diameter of the CO2 recovery piping was possible to 50 mm at most to gain more than adequate heating effect.

Soma, Hiroshi; Iwasawa, Kenji; Fukumiya, Kenji

348

Stratigraphy, Hydrothermal Alteration and Evolution of the Mangakino Geothermal System, Taupo Volcanic Zone, New Zealand  

Microsoft Academic Search

A major part of the ca. 1.6 Myr history of the Taupo Volcanic Zone (TVZ) is represented by buried and hydrothermally altered rocks penetrated by geothermal exploration wells. The geothermal field at Mangakino is sited in the oldest TVZ caldera on the western edge of the TVZ. Four exploration wells into the field reveal a thick sequence of flat-lying ignimbrites.

C. J. Fagan; C. J. Wilson; K. D. Spinks; P. R. Browne; S. F. Simmons

2006-01-01

349

Sustaining the National Geothermal Data System: Considerations for a System Wide Approach and Node Maintenance, Geothermal Resources Council 37th Annual Meeting, Las Vegas, Nevada, September 29-October 2, 2013  

SciTech Connect

Since the 2009 American Recovery and Reinvestment Act the U.S. Department of Energy’s Geothermal Technologies Office has funded $33.7 million for multiple data digitization and aggregation projects focused on making vast amounts of geothermal relevant data available to industry for advancing geothermal exploration. These projects are collectively part of the National Geothermal Data System (NGDS), a distributed, networked system for maintaining, sharing, and accessing data in an effort to lower the levelized cost of electricity (LCOE). Determining “who owns” and “who maintains” the NGDS and its data nodes (repositories in the distributed system) is yet to be determined. However, the invest- ment in building and populating the NGDS has been substantial, both in terms of dollars and time; it is critical that this investment be protected by ensuring sustainability of the data, the software and systems, and the accessibility of the data. Only then, will the benefits be fully realized. To keep this operational system sustainable will require four core elements: continued serving of data and applications; maintenance of system operations; a governance structure; and an effective business model. Each of these presents a number of challenges. Data being added to the NGDS are not strictly geothermal but data considered relevant to geothermal exploration and develop- ment, including vast amounts of oil and gas and groundwater wells, among other data. These are relevant to a broader base of users. By diversifying the client base to other users and other fields, the cost of maintaining core infrastructure can be spread across an array of stakeholders and clients. It is presumed that NGDS will continue to provide free and open access to its data resources. The next-phase NGDS operation should be structured to eventually pursue revenue streams to help off-set sustainability expenses as necessary and appropriate, potentially including income from: grants and contracts (agencies, foundations, pri- vate sector), membership, fees for services (consulting, training, customization, ‘app’ development), repository services (data, services, apps, models, documents, multimedia), advertisements, fees for premier services or applications, subscriptions to value added services, licenses, contributions and donations, endow- ments, and sponsorships.

Allison, Lee [Arizona Geological Survey; Chickering, Cathy [Southern Methodist University; Anderson, Arlene [U. S. Department of Energy, Geothermal Technologies Office; Richard, Stephen M. [Arizona Geological Survey

2013-10-01

350

Numerical modeling of the thermo-physical hydrology of volcanic geothermal systems  

NASA Astrophysics Data System (ADS)

Numerical modeling of fluid flow and heat transfer plays an important role in elucidating the structure and dynamics of hydrothermal systems. Although past studies have provided important insights into the physical factors governing fluid convection, most numerical models have been limited by temperature restrictions or other simplifications that have limited the applicability of model results to natural geothermal systems. This study applies the fluid flow and heat transport code CSMP++ to simulate the cooling of intrusions and the sub-surface structure and evolution of hydrothermal systems. Early simulations are focused on characterizing the influence of ';primary' factors such as magma chamber depth and geometry as well as system-scale permeability. Later simulations will test the influence of fluid salinity, topography, as well as heterogeneous/anisotropic permeability. Preliminary results show that the depth of the magma chamber plays an important role in system evolution, strongly influencing whether two upflow zones develop on the margins of the chamber or a single upflow zone develops directly over the center. If the roof of the magma chamber is near 2-2.5 km depth, extensive two-phase zones can develop above the magma chambers and are able to transport heat much more rapidly than for single-phase upflow zones. As shown by previous studies, higher host rock permeability results in lower upflow temperatures and thus two-phase zones are more short-lived and confined to shallower depths. However, since the total fluid flux around the magma chamber is much greater, higher permeability causes magma chambers to cool more rapidly and develop more numerous, narrower upflow zones than develop at lower permeability. Although relatively little is known about the geometry of magma bodies acting as heat sources for geothermal systems, results from these simulations show that information obtainable from drilling, such as the locations and temperatures of upflow zones, may be able to constrain the depth and geometry of possible heat sources. Similarly, while permeability is difficult to directly measure in natural reservoirs, simulation results show that upflow zone temperatures are very sensitive to the system-scale permeability. Future simulation efforts will build on these early results in a systematic way in order to quantitatively examine the main governing factors and their physical effects.

Scott, S. W.; Driesner, T.; Weis, P.

2013-12-01

351

Idaho Geothermal Commercialization Program. Idaho geothermal handbook  

SciTech Connect

The following topics are covered: geothermal resources in Idaho, market assessment, community needs assessment, geothermal leasing procedures for private lands, Idaho state geothermal leasing procedures - state lands, federal geothermal leasing procedures - federal lands, environmental and regulatory processes, local government regulations, geothermal exploration, geothermal drilling, government funding, private funding, state and federal government assistance programs, and geothermal legislation. (MHR)

Hammer, G.D.; Esposito, L.; Montgomery, M.

1980-03-01

352

Final Report: Natural State Models of The Geysers Geothermal System, Sonoma County, California  

SciTech Connect

Final project report of natural state modeling effort for The Geysers geothermal field, California. Initial models examined the liquid-dominated state of the system, based on geologic constraints and calibrated to match observed whole rock delta-O18 isotope alteration. These models demonstrated that the early system was of generally low permeability (around 10{sup -12} m{sup 2}), with good hydraulic connectivity at depth (along the intrusive contact) and an intact caprock. Later effort in the project was directed at development of a two-phase, supercritical flow simulation package (EOS1sc) to accompany the Tough2 flow simulator. Geysers models made using this package show that ''simmering'', or the transient migration of vapor bubbles through the hydrothermal system, is the dominant transition state as the system progresses to vapor-dominated. Such a system is highly variable in space and time, making the rock record more difficult to interpret, since pressure-temperature indicators likely reflect only local, short duration conditions.

T. H. Brikowski; D. L. Norton; D. D. Blackwell

2001-12-31

353

Accelerated Geothermal Resource Development in the Great Basin Through Enhanced Public Awareness and Outreach to Shareholders.  

SciTech Connect

The Great Basin Center for Geothermal Energy conducted work encompassing two main tasks. We (1) produced a web-based, stakeholder geothermal information system for Nevada geothermal data relevant to assessing and developing geothermal resources, and (2) we held informational stakeholder workshops (both as part of GeoPowering the West Initiative). The objective of this grant was to conduct workshops and fund database and web development activities. This grant funds salaries for web and database developers and part of the administrative assistant who helps to coordinate and organize workshops, and maintain selected databases.

Taranik, James V.; Oppliger, Gary; Sawatsky, Don

2002-04-10

354

GEOTHERMAL RESERVOIR ENGINEERING MANGEMENT PROGRAM PLAN (GREMP PLAN)  

E-print Network

flow in a geothermal system; a chemical simulation mightsimulation or to expose the fundamental laws governing geothermalsimulations. Statement of the Problem Problems in numerical modeling of geothermal

Bloomster, C.H.

2010-01-01

355

User manual for GEOCITY: A computer model for cost analysis of geothermal district-heating-and-cooling systems. Volume 1: Main text  

NASA Astrophysics Data System (ADS)

The cost of residential space heating, space cooling, and sanitary water heating or process heating (cooling) using geothermal energy from a hydrothermal reservoir was calculated. The GEOCITY simulates the complete geothermal heating and cooling system, which consists of two principal parts: the reservoir and fluid transmission system and the distribution system. Geothermal space heating is provided by circulating hot water through radiators, convectors, and fan-coil units. Geothermal process heating is provided by directly using the hot water or by circulating it through a process heat exchanger. The life cycle cost of thermal energy from the reservoir and fluid transmission system to the distribution system and the life cycle cost of heat (chill) to the end users are calculated by discounted cash flow analysis.

Huber, H. D.; Fassbender, L. L.; Bloomster, C. H.

1982-09-01

356

Geologic and hydrologic research on the Moana geothermal system, Washoe County, Nevada. Final report October 1, 1982-December 31, 1983  

SciTech Connect

Combined geologic, geophysical, geochemical, and drilling exploration surveys were used to assess the Moana geothermal resource in Washoe County, Nevada, and to determine its relationship with nearby Steamboat Hot Springs. Moana is the largest single moderate-temperature resource in Nevada that supports geothermal space heating applications. Results show that the general geology and structure for the two systems is similar, but important differences exist with respect to reservoir rocks. Gravity data delineated the contact between important volcanic and sedimentary rocks in Moana, but contour trends did not correlate well with mapped faults. Fluid geochemistry data show major differences in bulk chemical composition, stable-light isotope ratios, and radiocarbon ages for Moana and Steamboat geothermal waters. Water level measurements in observation wells in Moana show simultaneous increasing and decreasing values in different sections of the geothermal area. Temperature-depth profiles changed little during the six-month monitoring period. Direct use of the resource is increasing and longer-lasting, more efficient down-hole heat exchangers are replacing previous equipment that was prone to scaling and corrosion. A computer program that calculates heat output for state-of-the-art heat exchangers is described. Recommendations for continued monitoring, heat exchanger design, and fluid reinjection studies are included. Data are available to government agencies responsible for regulation as well as local residents and potential developers to ensure prudent resource utilization.

Flynn, T.; Ghusn, G. Jr.

1984-01-01

357

Microseismic Activity in Low-Hazard Geothermal Settings in Southern Germany  

NASA Astrophysics Data System (ADS)

In the last few years several geothermal power plants have taken up production in southern Germany and many more are currently in exploration or construction stages. One of the most promising areas in Germany with respect to geothermal exploitation is the Bavarian Molasse Basin: A karstified limestone formation at a few kilometers depth provides sufficiently high temperatures also for power production and its high permeability obviates the need for hydraulic stimulation of the reservoir. Furthermore the local setting is being considered as generally aseismic with very sparse and weak seismicity. The seismic hazard going along with production is therefore being considered negligible and no particular efforts for seismic monitoring were made. In 2008, however, an unexpected Ml 2.3 event which was felt by locals attracted public attention. With no stations near the epicenter, the event still was located in the general vicinity of a geothermal plant that took up production about half a year earlier. In the last two years a temporary network was set up that recorded more than thirty events with magnitudes mainly ranging from Ml 0 to 1.5. The data recorded in the local network are used for absolute locations. A high resolution 3-D P-wave velocity model is constructed from data of a dense 3-D seismic survey conducted to image the geothermal reservoir. An S-wave velocity model is compiled from converted shear waves, an old survey with shear wave excitation and cluster analysis of Vp/Vs ratios using the recorded events. Results show the hypocenters close to the bottom of the injection well. Results of waveform similarity analysis and clustering of events are presented along with preliminary results of further work focusing on hypocenter relocation via master-slave analysis and differential location techniques. Still, the exact extent of the man-made influence on the seismicity remains arguable. Events below magnitude 1.5 could not be detected prior to the production of the geothermal plant in the main network of the local earthquake service. Questions also remain as to the unique features of this geothermal site in comparison with others not far away that do not produce notable induced seismicity. How the fault targeted by the well is oriented in the present-day stress field is suspected to have a major impact on fault reactivation. An upcoming field experiment is about to address these open questions and test some working hypotheses. It is located at another geothermal reservoir in a very similar setting where a geothermal power plant is currently in the construction stage. In addition to monitoring the production stage, we intend to collect one year of pre-production data of the unperturbed reservoir. This will enable us to better assess the influence of fluid injections on local seismicity at geothermal plants and will lead to a better understanding of the reasons for the observed microseismicity.

Megies, T.; Wassermann, J. M.

2010-12-01

358

Structural control on geothermal circulation in the Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Argentina)  

NASA Astrophysics Data System (ADS)

The reconstruction of the stratigraphical-structural framework and the hydrogeology of geothermal areas is fundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermal fluids and for planning the exploitation of the field. The Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina) has a high geothermal potential. It is crossed by the active NW-SE trans-Andean tectonic lineament known as the Calama-Olacapato-Toro (COT) fault system, which favours a high secondary permeability testified by the presence of numerous springs. This study presents new stratigraphic and hydrogeological data on the geothermal field, together with the analysis from remote sensed image analysis of morphostructural evidences associated with the structural framework and active tectonics. Our data suggest that the main geothermal reservoir is located within or below the Pre-Palaeozoic-Ordovician basement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged by infiltration in the ridges above 4500 m a.s.l., where basement rocks are in outcrop. Below 4500 m a.s.l., the reservoir is covered by the low permeable Miocene-Quaternary units that allow a poor circulation of shallow groundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regional structures, particularly NW-SE COT-parallel lineaments, intersect with secondary structures, such as at the Tocomar field. Away from the main tectonic features, such as at the Cerro Tuzgle field, the less developed network of faults and fractures allows only a moderate upwelling of geothermal fluids and a mixing between hot and shallow cold waters. The integration of field-based and remote-sensing analyses at the Cerro Tuzgle-Tocomar area proved to be effective in approaching the prospection of remote geothermal fields, and in defining the conceptual model for geothermal circulation.

Giordano, Guido; Pinton, Annamaria; Cianfarra, Paola; Baez, Walter; Chiodi, Agostina; Viramonte, José; Norini, Gianluca; Groppelli, Gianluca

2013-01-01

359

Broadband Magnetotelluric Investigations of Crustal Resistivity Structure in North-Eastern Alberta: Implications for Engineered Geothermal Systems  

NASA Astrophysics Data System (ADS)

Greenhouse gas emissions from hydrocarbon consumption produce profound changes in the global climate, and the implementation of alternative energy sources is needed. The oilsands industry in Alberta (Canada) is a major producer of greenhouse gases as natural gas is burnt to produce the heat required to extract and process bitumen. Geothermal energy could be utilized to provide this necessary heat and has the potential to reduce both financial costs and environmental impacts of the oilsands industry. In order to determine the geothermal potential the details of the reservoir must be understood. Conventional hydrothermal reservoirs have been detected using geophysical techniques such as magnetotellurics (MT) which measures the electrical conductivity of the Earth. However, in Northern Alberta the geothermal gradient is relatively low, and heat must be extracted from deep inside the basement rocks using Engineered Geothermal Systems (EGS) and therefore an alternative exploration technique is required. MT can be useful in this context as it can detect fracture zones and regions of elevated porosity. MT data were recorded near Fort McMurray with the goal of determining the geothermal potential by understanding the crustal resistivity structure beneath the Athabasca Oilsands. The MT data are being used to locate targets of significance for geothermal exploration such as regions of low resistivity in the basement rocks which can relate to in situ fluids or fracture zones which can facilitate efficient heat extraction or het transport. A total of 93 stations were collected ~500m apart on two profiles stretching 30 and 20km respectively. Signals were recorded using Phoenix Geophysics V5-2000 systems over frequency bands from 1000 to 0.001 Hz, corresponding to depths of penetration approximately 50m to 50km. Groom-Bailey tensor decomposition and phase tensor analysis shows a well defined geoelectric strike direction that varied along the profile from N60°E to N45°E. Inversion of the data reveals the low resistivity sedimentary rocks of the Western Canadian Sedimentary Basin overlying a highly resistive Pre-Cambrian crystalline basement. The basement rocks have strong indications of being electrically anisotropic. Groom-Bailey and phase tensor azimuths are stable and consistent across both frequency and distance but display large phase tensor skew values (indicating 3D structure) and small induction vectors (indicating a lack of lateral structure). This type of anisotropy is unique because of its apparent widespread nature and the number of sites we have to constrain the anisotropic characteristics. These results can help to guide future geothermal development in Alberta as detailed information of the host rock resistivity structure can aid any EGS development.

Liddell, M. V.; Unsworth, M. J.; Nieuwenhuis, G.

2013-12-01

360

Multidisciplinary research of geothermal modeling  

NASA Astrophysics Data System (ADS)

KEYWORDS Geothermal sciences, geothermics, research, theory and application, numerical calculation, geothermal modeling, Technical University Darmstadt, Ministry of Economics and Technology (BMWi) INTRODUCTION In times of global warming renewable, green energies are getting more and more important. The development of application of geothermal energy as a part of renewable energies in Germany is a multidisciplinary process of fast growing research and improvements. Geothermal energy is the energy, which is stored below earth's surface. The word geothermal derives from the Greek words geo (earth) and thermos (heat), so geothermal is a synonym to earth heat. Geothermal energy is one of the auspicious renewable energies. In average the temperature increases 3°C every 100 m of depth, which is termed as geothermal gradient. Therefore 99 percent of our planet is hotter than 1.000°C, while 99 percent of that last percent is even hotter than 100°C. Already in a depth of about 1 kilometer temperatures of 35 - 40°C can be achieved. While other renewable energies arise less or more from the sun, geothermal energy sources its heat from the earth's interior, which is caused mostly by radioactive decay of persistent isotopes. This means a possibility of a base-loadable form of energy supply. Especially efficient is the use of deep geothermal energy of high-enthalpie reservoirs, which means a high energy potential in low depths. In Germany no high-enthalpie reservoirs are given. To use the given low-enthalpie potential and to generate geothermal power efficiently inventions and improvements need to be performed. An important part of geothermal progresses is performed by universities with multidisciplinary research of geothermal modeling. Especially in deep geothermal systems numerical calculations are essential for a correct dimensioning of the geothermal system. Therefore German universities and state aided organizations are developing numerical programs for a detailed use of application on geothermal systems. The history of this multidisciplinary research of geothermal modeling performed by German universities is shown in this paper. Outstanding geothermal research programs of German universities and state aided organizations (BGR, LBEG, GGA) are pointed out. Actual geothermal modeling programs based on the Finite-Element-Method or the Finite-Differences-Method as well as analytical programs are introduced. National and international geothermal projects supported by German universities and state aided organizations are described. Examples of supervised shallow and deep geothermal systems are given. Actually the Technical University Darmstadt is performing a research program supported by a national organization, the Ministry of Economics and Technology (BMWi). Main aim of this research program titled experimental investigation for the verification of a Finite-Element-Multiphase-Model is to analyze the subsoil as a three-phases-model with separated consideration of conduction, convection and advection and their subsequent interaction. The latest developments of numerical projects as well as the actual state of the before mentioned research program are pointed out in the paper. REFERENCES Quick, H., Arslan, U., Meißner, S., Michael, J. 2007. Deep foundations and geothermal energy - a multi-purpose solution, IFHS: 8. International conference on multi-purpose high-rise towers and tall buildings, Abu Dhabi, 2007 Arslan, U. and Huber, H. 2008. Application of geothermal energy. University of Istanbul, Yapistanbul No. 3 / 2008, Turkey, 2008 Quick, Q., Michael, J., Arslan, U., Huber, H. 2010. History of International Geothermal Power Plants and Geothermal Projects in Germany, Proceedings World Geothermal Congress 2010 Bali, Indonesia, 25-29 April 2010 Arslan, U., Huber, H. 2010. Education of Geothermal Sciences in Germany as part of an application orientated research, Proceedings European Civil Engineering Education and Training (EUCEET III) Special Volume, 2010

-Ing. Ulvi Arslan, Univ., ., Dr. _., Prof.; Heiko Huber, Dipl.-Ing.

2010-05-01

361

Geochemical Enhancement Of Enhanced Geothermal System Reservoirs: An Integrated Field And Geochemical Approach  

SciTech Connect

The geochemical effects of injecting fluids into geothermal reservoirs are poorly understood and may be significantly underestimated. Decreased performance of injection wells has been observed in several geothermal fields after only a few years of service, but the reasons for these declines has not been established. This study had three primary objectives: 1) determine the cause(s) of the loss of injectivity; 2) utilize these observations to constrain numerical models of water-rock interactions; and 3) develop injection strategies for mitigating and reversing the potential effects of these interactions. In this study rock samples from original and redrilled injection wells at Coso and the Salton Sea geothermal fields, CA, were used to characterize the mineral and geochemical changes that occurred as a result of injection. The study documented the presence of mineral scales and at both fields in the reservoir rocks adjacent to the injection wells. At the Salton Sea, the scales consist of alternating layers of fluorite and barite, accompanied by minor anhydrite, amorphous silica and copper arsenic sulfides. Amorphous silica and traces of calcite were deposited at Coso. The formation of silica scale at Coso provides an example of the effects of untreated (unacidified) injectate on the reservoir rocks. Scanning electron microscopy and X-ray diffractometry were used to characterize the scale deposits. The silica scale in the reservoir rocks at Coso was in