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Sample records for methane hydrate-bearing deep

  1. Fungal communities from methane hydrate-bearing deep-sea marine sediments in South China Sea.

    PubMed

    Lai, Xintian; Cao, Lixiang; Tan, Hongming; Fang, Shu; Huang, Yali; Zhou, Shining

    2007-12-01

    To elucidate fungal diversity in methane hydrate-bearing deep-sea marine sediments in the South China Sea, internal transcribed spacer (ITS) regions of rRNA genes from five different sediment DNA samples were amplified and phylogenetically analyzed. Total five ITS libraries were constructed and 413 clones selected randomly were grouped into 24 restriction patterns by Amplified Ribosomal DNA Restriction Analysis (ARDRA). ITS sequences of 44 representative clones were determined and compared with the GenBank database using gapped-BLAST. The phylogenetic analysis showed that the ITS sequences (71-97% similarity) were similar to those of Phoma, Lodderomyces, Malassezia, Cryptococcus, Cylindrocarpon, Hortaea, Pichia, Aspergillus and Candida. The remaining sequences were not associated to any known fungi or fungal sequences in the public database. The results suggested that methane hydrate-bearing deep-sea marine sediments harbor diverse fungi. This is the first report on fungal communities from methane hydrate-bearing deep-sea marine sediments in South China Sea.

  2. Methane Recovery from Hydrate-bearing Sediments

    SciTech Connect

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  3. Bacteria-Driven Carbon Metabolisms in Methane Hydrate-Bearing Deep Marine Sediments from the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Briggs, B.; Inagaki, F.; Morono, Y.; Futagami, T.; Winters, W.; Colwell, F.

    2008-12-01

    The methane hydrates in deep marine subsurface sediments play an important role in the global biogeochemical cycling of carbon. However, we have a limited understanding of the microbial communities and their metabolic functioning with respect to carbon assimilation and respiration pathways in those habitats. Our objective was to determine the microbial diversity and the primary functional genes relevant to potential carbon metabolism in sediments that contain the deepest methane hydrates yet discovered. The samples were obtained from offshore India near the Andaman Islands in the Bay of Bengal, representing the deepest methane hydrate sediments found to date, likely due to the low geothermal gradient. The hydrate was found in sediment layers that contain coarse-grained volcanic ash in the depth range from 300 to 650 meters below the seafloor. DNA was extracted from 13 depth horizons, eight of which were found onboard to contain methane hydrates. Microscopic cell enumeration and domain-specific quantitative polymerase chain reaction (qPCR) revealed that those sediments harbor relatively small microbial populations that are composed mainly of Bacteria. For each sample, multiple displacement amplification (MDA) followed by PCR amplification was attempted using primers specific for archaeal and bacterial 16S rRNA, acetyl-CoA carboxylase (accC), citrate lyase (aclB), pyruvate oxidoreductase (porA), oxoglutarate oxidoreductase (oorA), 1,5-bisphosphate carboxylase (RubisCO: cbbL), particulate methane monooxygenase (pmoA), methanol dehydrogenase (mxaF), and methyl co-enzyme M reductase (mcrA) genes. Consistent with the low Archaea abundance predicted by qPCR, archaeal 16S rRNA, mcrA, and aclB genes were never detected, while the bacterial 16S rRNA genes and the functional genes of oorA, accC, cbbL, pmoA, mxaF, and porA were successfully amplified. Clone libraries of 16S rRNA and functional genes indicated that members of Firmicutes and other Gram-positive Bacteria, such as

  4. Fine structure of methane hydrate-bearing sediments on the Blake Outer ridge as determined from deep-tow multichannel seismic data. (Reannouncement with new availability information). Final report

    SciTech Connect

    Rowe, M.M.; Gettrust, J.F.

    1993-01-01

    High-resolution, deep-tow multichannel seismic data are used to investigate the detailed structure of sediments containing methane hydrate. These data support thick, laterally extensive layers of methane hydrate-bearing sediment underlain by a bottom simulating reflector (BSR) and spatially discontinuous zones of hydrate within the sediments above the BSR depth where no BSR is present. These data resolve normal faults which extend from the surface through the BSR with apparent offsets of up to 20 m. A phase inversion identified at the top of the BSR shows that the material immediately beneath the BSR has anomalously low velocity, consistent with a layer of sediment containing free methane gas. The fault offsets along the BSR and consistent with a pressure change of approx. 200 kPa (approx. 2 bars) across the fault zone.... Directional ambient noise, Bottom scattering, Deep-towed array geophysical system, Towed array, Ocean-bottom seismometer

  5. Seismic Property changes in Methane Gas Hydrate Bearing Sediments During Geomechanical Testing

    NASA Astrophysics Data System (ADS)

    Rees, E. V.; Nakagawa, S.; Kneafsey, T. J.

    2011-12-01

    Geomechanical properties of methane hydrate bearing sediments can impact oil and gas well stability and production performance of hydrate-bearing reservoirs in permafrost regions. Methane hydrate stability in permafrost environments occurs at lower pressures than those of deep sea deposits. Consequently, changes in temperature conditions that occur during hydrocarbon exploration can have a larger impact on methane hydrate stability than in deep sea fields. In recent years, the understanding of the geomechanical properties of hydrate bearing sediment has advanced significantly. However, geophysical signatures of the changes occurring within the sediment undergoing mechanical changes and failure (which are necessary for remote detection and monitoring of the well and reservoir) are not well understood, primarily because of limited available experimental and field data. We conducted a series of triaxial compression tests on methane-hydrate bearing sediment samples in an X-ray transparent triaxial test cell. The cell can apply high pressures under controlled temperatures (5MPa and 2°C were our typical test parameters). This capability allows us to conduct experiments under the realistic temperature, pressure, and chemical conditions of a hydrate reservoir, which is important for studying the behavior of hydrate bearing sediments subjected to changes in the reservoir environment. The cell is also capable of propagating 6-to-12 kHz compression and torsion waves along the sample axis during the test, due to a piezoelectric source and receiver embedded in the top and bottom loading pedestals. Methane hydrate was first synthesized inside a sediment pack under isotropic stress, after which additional stress was applied to bring the sample to failure. Concurrently, seismic velocities of the sample were monitored throughout the process. Before and after the experiment, X-ray CT images were taken to examine the heterogeneity of hydrate distribution within an intact sample and

  6. Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

    USGS Publications Warehouse

    Pohlman, J.W.; Bauer, J.E.; Waite, W.F.; Osburn, C.L.; Chapman, N.R.

    2011-01-01

    Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use ??14 C and ??13 C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13 C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000-6,000 year age of dissolved organic carbon in the deep ocean, and provide reduced organic matter and energy to deep-ocean microbial communities. ?? 2011 Macmillan Publishers Limited. All rights reserved.

  7. Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Lee, J. Y.; Yun, T. S.; Santamarina, J. C.; Ruppel, C.

    2007-06-01

    The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

  8. Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

    USGS Publications Warehouse

    Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.

    2007-01-01

    The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

  9. CFD Modeling of Methane Production from Hydrate-Bearing Reservoir

    SciTech Connect

    Gamwo, I.K.; Myshakin, E.M.; Warzinski, R.P.

    2007-04-01

    Methane hydrate is being examined as a next-generation energy resource to replace oil and natural gas. The U.S. Geological Survey estimates that methane hydrate may contain more organic carbon the the world's coal, oil, and natural gas combined. To assist in developing this unfamiliar resource, the National Energy Technology Laboratory has undertaken intensive research in understanding the fate of methane hydrate in geological reservoirs. This presentation reports preliminary computational fluid dynamics predictions of methane production from a subsurface reservoir.

  10. Temperature variation in methane hydrate bearing sediments in the eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Fujii, T.; Nagakubo, S.; Kawasaki, T.; Fukuhara, M.; Fujii, K.

    2005-12-01

    In the Nankai Trough, seismic data indicates widespread existence of BSR, which is interpreted as an indicator of bottom boundary of methane hydrate bearing zone. Methane hydrate is regarded as future possible natural gas resource, although the mechanisms of its occurrence and distribution have been poorly understood. In order to obtain data for the understanding of methane hydrate occurrence and natural reserves estimation, METI exploratory test wells _e_fTokai-oki to Kumano-nada_h were drilled from January to May in 2004 in the eastern Nankai Trough, offshore central Japan. As a part of this project, continuous formation temperature measurement in hydrate bearing sediments in ocean area, the first attempt in the world, was carried out in order to investigate in-situ temperature condition in hydrate bearing sediments and to obtain basic data to evaluate methane hydrate occurrence. Optical fiber sensor was used for the measurement of temperature distribution. Sensor cable was set in the borehole, with the measurement system (data logger) set above the seafloor. 2 kinds of sensor cable, DTS (Distributed Temperature Sensor) and FBG (Fiber Bragg Grating), were set in the borehole. Continuous temperature distribution data for 50 days was obtained successfully at the location where pore space type hydrate was confirmed in sand layer by coring. Averaged temperature depth profile was constructed after analysis such as data conversion, quality control, evaluation of temperature stability, temperature correction and depth correction (Fukuhara et al., 2005). The thermal gradient obtained from temperature depth profile showed good matching with expected thermal gradient in this area (3C/100m), below hydrate bearing zone. On the other hand, apparent lower thermal gradient was observed in hydrate bearing zone and also around lower BSR. In addition, as a result of preliminary estimation of bottom depth of a hydrate stability zone (BGHS) from phase diagram with measured

  11. Laboratory formation of non-cementing, methane hydrate-bearing sands

    USGS Publications Warehouse

    Waite, William F.; Bratton, Peter M.; Mason, David H.

    2011-01-01

    Naturally occurring hydrate-bearing sands often behave as though methane hydrate is acting as a load-bearing member of the sediment. Mimicking this behavior in laboratory samples with methane hydrate likely requires forming hydrate from methane dissolved in water. To hasten this formation process, we initially form hydrate in a free-gas-limited system, then form additional hydrate by circulating methane-supersaturated water through the sample. Though the dissolved-phase formation process can theoretically be enhanced by increasing the pore pressure and flow rate and lowering the sample temperature, a more fundamental concern is preventing clogs resulting from inadvertent methane bubble formation in the circulation lines. Clog prevention requires careful temperature control throughout the circulation loop.

  12. Microbial community structure in methane hydrate-bearing sediments of freshwater Lake Baikal.

    PubMed

    Kadnikov, Vitaly V; Mardanov, Andrey V; Beletsky, Alexey V; Shubenkova, Olga V; Pogodaeva, Tatiana V; Zemskaya, Tamara I; Ravin, Nikolai V; Skryabin, Konstantin G

    2012-02-01

    Gas hydrates in marine sediments have been known for many years but recently hydrates were found in the sediments of Lake Baikal, the largest freshwater basin in the world. Marine gas hydrates are associated with complex microbial communities involved in methanogenesis, methane oxidation, sulfate reduction and other biotransformations. However, the contribution of microorganisms to the formation of gas hydrates remains poorly understood. We examined the microbial communities in the hydrate-bearing sediments and water column of Lake Baikal using pyrosequencing of 16S rRNA genes. Aerobic methanotrophic bacteria dominated the water sample collected at the lake floor in the hydrate-bearing site. The shallow sediments were dominated by Archaea. Methanogens of the orders Methanomicrobiales and Methanosarcinales were abundant, whereas representatives of archaeal lineages known to perform anaerobic oxidation of methane, as well as sulfate-reducing bacteria, were not found. Affiliation of archaea to methanogenic rather than methane-oxidizing lineages was supported by analysis of the sequences of the methyl coenzyme M reductase gene. The deeper sediments located at 85-90 cm depth close to the hydrate were dominated by Bacteria, mostly assigned to Chloroflexi, candidate division JS1 and Caldiserica. Overall, our results are consistent with the biological origin of methane hydrates in Lake Baikal. PMID:22092495

  13. Methane flux in potential hydrate-bearing sediments offshore southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Nai-Chen; Yang, Tsanyao Frank; Chuang, Pei-Chuan; Hong, Wei-Li; Chen, Hsuan-Wen; Lin, Saulwood; Lin, Li-Hung; Mastumoto, Ryo; Hiruta, Akihiro; Sun, Chih-Hsien; Wang, Pei-Ling; Yang, Tau; Jiang, Shao-yong; Wang, Yun-shuen; Chung, San-Hsiung; Chen, Cheng-Hong

    2016-04-01

    Methane in interstitial water of hydrate-bearing marine sediments ascends with buoyant fluids and is discharged into seawater, exerting profound impacts on ocean biogeochemistry and greenhouse effects. Quantifying the exact magnitude of methane transport across different geochemical transitions in different geological settings would provide bases to better constrain global methane discharge to seawater and to assess physio-chemical contexts imposed on microbial methane production and consumption and carbon sequestration in marine environments. Using sediments collected from different geological settings offshore southwestern Taiwan through decadal exploration on gas hydrates, this study analyzed gas and aqueous geochemistry and calculated methane fluxes across different compartments. Three geochemical transitions, including sulfate-methane transition zone (SMTZ), shallow sediments, and sediment-seawater interface were specifically focused for the flux calculation. The results combined with previous published data showed that methane fluxes at three interfaces of 2.71×10-3 to 3.52×10-1, 5.28×10-7 to 1.08×100, and 1.34×10-6 to 3.17×100 mmol m-2 d-1, respectively. The ranges of fluxes suggest that more than 90 % of methane originating from depth was consumed by anaerobic methanotrophy at the SMTZ, and further >90% of the remnant methane was removed by aerobic methanotrophy prior to reaching the sediment-seawater interface. Exceptions are sites at cold seeps where the percentage of methane released into seawater can reach more than 80% of methane at depth. Most sites with such high methane fluxes are located at active margin where thrusts and diapirism are well developed. Carbon mass balance method was applied for the calculation of anaerobic oxidation of methane (AOM) and organotrophic sulfate reduction rates at SMTZ. Results indicated that AOM rates were comparable with fluxes deduced from concentration gradients for most sites. At least 60% of sulfate

  14. Composite model to reproduce the mechanical behaviour of methane hydrate bearing soils

    NASA Astrophysics Data System (ADS)

    De la Fuente, Maria

    2016-04-01

    Methane hydrate bearing sediments (MHBS) are naturally-occurring materials containing different components in the pores that may suffer phase changes under relative small temperature and pressure variations for conditions typically prevailing a few hundreds of meters below sea level. Their modelling needs to account for heat and mass balance equations of the different components, and several strategies already exist to combine them (e.g., Rutqvist & Moridis, 2009; Sánchez et al. 2014). These equations have to be completed by restrictions and constitutive laws reproducing the phenomenology of heat and fluid flows, phase change conditions and mechanical response. While the formulation of the non-mechanical laws generally includes explicitly the mass fraction of methane in each phase, which allows for a natural update of parameters during phase changes, mechanical laws are, in most cases, stated for the whole solid skeleton (Uchida et al., 2012; Soga et al. 2006). In this paper, a mechanical model is proposed to cope with the response of MHBS. It is based on a composite approach that allows defining the thermo-hydro-mechanical response of mineral skeleton and solid hydrates independently. The global stress-strain-temperature response of the solid phase (grains + hydrate) is then obtained by combining both responses according to energy principle following the work by Pinyol et al. (2007). In this way, dissociation of MH can be assessed on the basis of the stress state and temperature prevailing locally within the hydrate component. Besides, its structuring effect is naturally accounted for by the model according to patterns of MH inclusions within soil pores. This paper describes the fundamental hypothesis behind the model and its formulation. Its performance is assessed by comparison with laboratory data presented in the literature. An analysis of MHBS response to several stress-temperature paths representing potential field cases is finally presented. References

  15. Ultrasonic Velocities in Methane Hydrate-Bearing Ottawa Sand F110

    NASA Astrophysics Data System (ADS)

    Rydzy, M. B.; Batzle, M. L.; Hester, K.; Howard, J. J.

    2010-12-01

    At the ConocoPhillips Technology Center in Bartlesville, an experimental setup was developed that facilitated ultrasonic velocity measurements of hydrate-bearing sediment samples inside a magnetic resonance imager (MRI). P- and S-wave velocities were determined using the pulse-transmission technique. The waveforms were generated with 500 kHz piezoelectric transducers that were embedded in PEEK end caps. This provided improved impedance matching between transducer and sample, as well as shielding of the transducers from the magnetic field of the MRI. The ultrasonic measurements were conducted in conjunction with magnetic resonance imaging (MRI), which proved to be a valuable tool to determine the gas hydrate saturation and distribution within the specimen. The hydrate-bearing samples were formed by injecting methane into partially water-saturated sand packs, whose porosity ranged around 40 percent. Specimen containing initial water saturations of 20 and 80 percent were investigated in this study. The sample was brought into the gas hydrate stability field by either cooling the pressurized sample or pressurizing the cooled sample. The velocity collected during the course of these experiments exhibited a noticeable dependence on both the initial water saturation as well as the order of pressurization and cooling. Comparison of the experimental data calculated using the pore scale models developed by Ecker et al. (1998) and Helgerud et al. (2000) indicated that the samples with high initial water saturation tended to be load-bearing, whereas samples formed from a low initial water saturation exhibited cementing characteristics. At low saturations, for the specimen that were pressurized after cooling, higher velocities were recorded than for samples that were first pressurized and then cooled afterward.

  16. Role of critical state framework in understanding geomechanical behavior of methane hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Uchida, Shun; Xie, Xiao-Guang; Leung, Yat Fai

    2016-08-01

    A proper understanding of geomechanical behavior of methane hydrate-bearing sediments is crucial for sustainable future gas production. There are a number of triaxial experiments conducted over synthetic and natural methane hydrate (MH)-bearing sediments, and several soil constitutive models have been proposed to describe their behavior. However, the generality of a sophisticated model is questioned if it is tested only for a limited number of cases. Furthermore, it is difficult to experimentally determine the associated parameters if their physical meanings and significance are not elucidated. The objective of this paper is to demonstrate that a simple extension of the critical state framework is sufficient to capture the geomechanical behavior of MH-bearing soils from various sources around the world, while the significance of each parameter is quantified through variance-based global sensitivity analyses. Our results show that the influence of hydrates can be largely represented by one hydrate-dependent parameter, pcd', which controls the expansion of the initial yield surface. This is validated through comparisons with shearing and volumetric response of MH-bearing soils tested at various institutes under different confining stresses and with varying degrees of hydrate saturation. Our study suggests that the behavior of MH-bearing soils can be reasonably predicted based on pcd' and the conventional critical state parameters of the host sediments that can be obtained through typical geotechnical testing procedures.

  17. Relation between methane hydrate-bearing formations and geological phenomena on the seafloor in the eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Nagakubo, S.; Kobayashi, T.; Inamori, T.; Saeki, T.; Shimoda, N.; Fujii, T.; Morita, S.; Tanahashi, M.

    2007-12-01

    In 2002, a series of high-resolution 3D seismic surveys was conducted in the Tokai-Oki, the Daini-Atsumi Knoll, the Kumano-nada in the eastern Nankai Trough, Japan. Research Consortium for Methane Hydrate Resources in Japan (MH21) conducted resource assessment of methane hydrate in the eastern Nankai Trough by various seismic data analyses combining results of the exploratory wells conducted in 2005. By these analyses, occurrence of methane hydrate in the eastern Nankai Trough is coming to light. The MH21 has also interpreted the relation between methane hydrate-bearing formations and various geological phenomena on the seafloor, such as pockmarks and carbonate outcrops, using the 3D seismic data in the three survey areas. Bathymetric maps and seafloor amplitude maps constructed by the high-resolution 3D data provided lots of information on the seafloor. Some areas show very high intensity on the seafloor amplitude maps. It is expected that the areas showing strong amplitude correspond to the distribution of carbonate outcrops which are likely precipitated by methane seep activities. By checking the seafloor amplitude maps, seismic sections and methane seep sites observed by the previous submersible dives, some significant correlations are recognized between methane hydrate-bearing formations and various phenomena on the seafloor. It may be likely that the occurrence of methane hydrate and the geological phenomena on the seafloor have a strong implication with some typical geologic structures, e.g. shallow fault, highly-permeable sediments and hydraulic fractures, which may control the fluid migration. Besides, in this study we learnt that bathymetric map and seafloor amplitude map constructed by the high- resolution 3D seismic data are very useful not only for interpretation of relation between methane hydrate-bearing formation and various phenomena on the seafloor but also for designing the following seafloor investigations. This study is conducted by the MH21.

  18. Microbial Communities in Methane Hydrate-Bearing Sediments from the Alaskan North Slope

    NASA Astrophysics Data System (ADS)

    Schwartz, A.; Briggs, B.; Colwell, F.

    2008-12-01

    High latitude soils and sediments often contain large quantities of methane as well as microbial communities capable of producing and consuming the methane. We studied the microbial communities collected from hydrate-bearing sediments on the Alaskan North Slope to determine how abiotic variables (e.g., grain size, hydrate presence, original depositional environment) may control the type and distribution of microbes in the sediments. The cores were acquired from sub-permafrost, Eocene (35-36 million years ago [MYA]) sediments laid down as a marine transgressive series within which hydrates are believed to have formed 1.5 MYA. Forty samples, eight of which originally contained hydrates, were acquired from depths of ca. 606-666 meters below land surface. Five samples from drilling fluids acquired from the same depth range were included in the analysis as a control for contamination during the drilling and handling of cores. DNA was extracted from the samples (typically <1 ng DNA/g sediment was recovered) and then amplified using polymerase chain reaction with primers specific for bacterial and archaeal 16S rDNA. Only bacterial DNA amplicons were detected. Terminal-restriction fragment length polymorphism (t-RFLP) was used to measure bacterial diversity in the respective samples. Non-metric multidimensional scaling (NMDS) was then used to determine the abiotic variables that may have influenced bacterial diversity. NMDS analysis revealed that sediment samples were distinct from those obtained from drilling fluids suggesting that the samples were not contaminated by the drilling fluids. All samples had evidence of microbial communities and sample depth, temperature, and hydrate presence appeared to have some influence on community diversity. Samples sharing these environmental parameters often shared common t-RFLP profiles. Further examination of selected samples using clone libraries should help to identify the key taxa present in these unique sediments and yield a

  19. Measurements of Gas-Water Relative Permeability for Methane-Hydrate-Bearing Sediments using X-ray Computed-Tomography

    NASA Astrophysics Data System (ADS)

    Konno, Y.; Jin, Y.; Nagao, J.

    2012-04-01

    Oceanic gas hydrate deposits at high saturations have been found within sandy sediments in areas such as the Eastern Nankai Trough and the Gulf of Mexico. The recent discovery of these deposits has stimulated research and development programs exploring the use of gas hydrates as energy resources. Depressurization is thought to be a promising method for gas recovery from gas hydrates deposits; however, considerable water production is expected when this method is applied for oceanic gas hydrate deposits. The prediction of water production is a critical problem for successful gas production from these deposits. The gas-water relative permeability of gas-hydrate-bearing sediments is a key parameter to predict gas-water-ratio (GWR) during gas production. However, the experimental measurement of gas-water relative permeability for gas-hydrate-bearing sediments is a challenging problem due to a phase change (gas hydrate formation/dissociation) during gas-water flooding test. We used X-ray computed tomography (CT) and a newly-developed core holder to measure gas-water relative permeability for gas-hydrate-bearing sediments. X-ray CT was used to image a displacement front and quantify density changes during water flooding test in methane-hydrate-bearing cores. We obtained CT images every two minutes during a water flooding test for a gas-saturated methane-hydrate-bearing core. The movement of displacement front was captured from these CT images. Quantitative analysis of density change was also done to analyze the change of gas/water saturations. We developed a multi-sensor-tap core holder to minimize capillary end effect on the pressure measurements. To be able to obtain CT images by X-ray, the core holder was made of aluminum alloy. We successfully measured pressure differences of the intermediate section of the core during water flooding test. The change of pressure differences during water flooding test showed strong correlation with the movement of displacement front

  20. Permeability of laboratory-formed methane-hydrate-bearing sand: Measurements and observations using x-ray computed tomography

    SciTech Connect

    Kneafsey, T. J.; Seol, Y.; Gupta, A.; Tomutsa, L.

    2010-09-15

    Methane hydrate was formed in two moist sands and a sand/silt mixture under a confining stress in an X-ray-transparent pressure vessel. Three initial water saturations were used to form three different methane-hydrate saturations in each medium. X-ray computed tomography (CT) was used to observe location-specific density changes caused by hydrate formation and flowing water. Gas-permeability measurements in each test for the dry, moist, frozen, and hydrate-bearing states are presented. As expected, the effective permeabilities (intrinsic permeability of the medium multiplied by the relative permeability) of the moist sands decreased with increasing moisture content. In a series of tests on a single sample, the effective permeability typically decreased as the pore space became more filled, in the order of dry, moist, frozen, and hydrate-bearing. In each test, water was flowed through the hydrate-bearing medium and we observed the location-specific changes in water saturation using CT scanning. We compared our data to a number of models, and our relative permeability data compare most favorably with models in which hydrate occupies the pore bodies rather than the pore throats. Inverse modeling (using the data collected from the tests) will be performed to extend the relative permeability measurements.

  1. A New Critical State Model for Geomechanical Behavior of Methane Hydrate-Bearing Sands

    NASA Astrophysics Data System (ADS)

    Lin, J. S.; Xing, P.; Rutqvist, J.; Seol, Y.; Choi, J. H.

    2014-12-01

    Methane hydrate bearing sands behave like sands once the hydrate has dissociated, but could exhibit a substantial increase in the shear strength, stiffness and dilatancy as the degree of hydrate saturation increases. A new critical state model was developed that incorporates the spatially mobilized plane (SMP) concept, which has been proven effective in modeling mechanical behavior of sands. While this new model was built on the basic constructs of the critical state model, important enhancements were introduced. The model adopted the t-stress concept, which defined the normal and shear stress on the SMP, in describing the plastic behavior of the soil. In this connection the versatile Matsuoka-Nakai yield criterion was also employed, which defined the general three dimensional yield behavior. The resulting constitutive law was associated in the t-stress space, but became non-associated in the conventional p-q stress space as it should be for sands. The model also introduced a generalized degree of hydrate saturation concept that was modified from the pioneering work of the Cambridge group. The model gives stress change when the sands are subjected to straining, and/or to hydrate saturation changes. The performance of the model has been found satisfactory using data from laboratory triaxial tests on reconstituted samples and core samples taken from Nankai Trough, Japan. The model has been implemented into FLAC3D. A coupling example with the multiphase flow code, TOUGH+, is presented which simulates the mechanical behavior of a sample when the surrounding temperature has been raised, and the hydrate undergoes state change and no longer resides in the stability zone.

  2. X-ray computed-tomography observations of water flow through anisotropic methane hydrate-bearing sand

    SciTech Connect

    Seol, Yongkoo; Kneafsey, Timothy J.

    2009-06-01

    We used X-ray computed tomography (CT) to image and quantify the effect of a heterogeneous sand grain-size distribution on the formation and dissociation of methane hydrate, as well as the effect on water flow through the heterogeneous hydrate-bearing sand. A 28 cm long sand column was packed with several segments having vertical and horizontal layers with sands of different grain-size distributions. During the hydrate formation, water redistribution occurred. Observations of water flow through the hydrate-bearing sands showed that water was imbibed more readily into the fine sand, and that higher hydrate saturation increased water imbibition in the coarse sand due to increased capillary strength. Hydrate dissociation induced by depressurization resulted in different flow patterns with the different grain sizes and hydrate saturations, but the relationships between dissociation rates and the grain sizes could not be identified using the CT images. The formation, presence, and dissociation of hydrate in the pore space dramatically impact water saturation and flow in the system.

  3. Mechanical and dissociation properties of methane hydrate bearing sands with various fines

    NASA Astrophysics Data System (ADS)

    Hyodo, M.

    2015-12-01

    A high pressure and low temperature plane strain testing apparatus was also developed for visualizing the deformation of methane hydrate (MH) bearing sand due to methane hydrate production . This apparatus can control temperatures and pressures equivalent to an MH reservoir in deep seabed. Additionally, observation windows are installed in front of and behind the specimen in order to allow the local deformation of the specimen during shear tests to be measured. The specimen is a cuboid with 80mm width, 60mm thickness and 160mm height. A 5mmx5mm mesh was drawn on the membrane in front of the observation window. Using this testing apparatus, plane strain compression and methane hydrate dissociation by depressurization tests were performed with the measurement of localized deformation. Local deformation analysis was performed by observing the cross-points of the mesh during shear tests and using this data in PIV analysis. Thermocouples were installed at 60mm and 30mm from the bottom of the specimen in order to measure the variation of the temperature during the dissociation of MH. Tc and Toyoura sand were the materials used for comparison. In plane strain shear tests, Tc and Toyoura sand as host sands with and without MH were compared. Due to the existence of MH, initial stiffness and strength increased in both materials, however the tendency was more apparent in Toyoura sand compared with Tc. The local deformations occurred more clearly in Toyoura sand, compared with fine material. It also appeared more clearly when the specimen contained MH. During depressurization, marked deformation was not observed, because of an increase of effective stress. However, after depressurization, repressurization caused the specimen to fail in the case of high initial shear stress conditions.

  4. Methane hydrate-bearing sediments in the Terrebonne basin, northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Meazell, K.; Flemings, P. B.

    2015-12-01

    We characterize the geological, geophysical, and thermodynamic state of three dipping, hydrate-bearing sands in the Terrebonne mini basin of the northern Gulf of Mexico, and describe three potential drilling locations to sample these hydrate reservoirs. Within the sand bodies, there is a prominent negative polarity seismic reflection (opposite phase to the seafloor reflector) that we interpret to record the boundary between gas hydrate above and free gas below. This anomaly is the Bottom Simulating Reflector (BSR) and the base of the Gas Hydrate Stability Zone (BGHSZ). Above the BSR, reflection seismic data record these reservoirs with a positive polarity while below it, they record the reservoirs with a negative polarity event. Within the sand bodies, seismic amplitudes are generally strongest immediately above and below the BSR and weaken in updip and downdip directions. Beneath the BSR, two of the reservoirs have a strong negative amplitude event that parallels structure that we interpret to record a gas-water contact, while the third reservoir does not clearly record this behavior. Much like the seafloor, the BSR is bowl-shaped, occurring at greatest depths in the northwest and rising near salt bodies in the south and east. In the north east area of previous exploration, the BSR is found at a depth of 2868 meters below sealevel, implying a geothermal gradient of 20.1oC/km for type I hydrates. Logging while drilling data reveal that the sands are composed of numerous thin, hydrocarbon-charged, coarse-grained sediments. Hydrate saturation in these sands is greatest near the BGHSZ. Pressure coring is proposed for three wells that will penetrate the reservoirs at different structural elevations in order to further elucidate reservoir conditions of the sands.

  5. Methane sources in gas hydrate-bearing cold seeps: Evidence from radiocarbon and stable isotopes

    USGS Publications Warehouse

    Pohlman, J.W.; Bauer, J.E.; Canuel, E.A.; Grabowski, K.S.; Knies, D.L.; Mitchell, C.S.; Whiticar, Michael J.; Coffin, R.B.

    2009-01-01

    Fossil methane from the large and dynamic marine gas hydrate reservoir has the potential to influence oceanic and atmospheric carbon pools. However, natural radiocarbon (14C) measurements of gas hydrate methane have been extremely limited, and their use as a source and process indicator has not yet been systematically established. In this study, gas hydrate-bound and dissolved methane recovered from six geologically and geographically distinct high-gas-flux cold seeps was found to be 98 to 100% fossil based on its 14C content. Given this prevalence of fossil methane and the small contribution of gas hydrate (??? 1%) to the present-day atmospheric methane flux, non-fossil contributions of gas hydrate methane to the atmosphere are not likely to be quantitatively significant. This conclusion is consistent with contemporary atmospheric methane budget calculations. In combination with ??13C- and ??D-methane measurements, we also determine the extent to which the low, but detectable, amounts of 14C (~ 1-2% modern carbon, pMC) in methane from two cold seeps might reflect in situ production from near-seafloor sediment organic carbon (SOC). A 14C mass balance approach using fossil methane and 14C-enriched SOC suggests that as much as 8 to 29% of hydrate-associated methane carbon may originate from SOC contained within the upper 6??m of sediment. These findings validate the assumption of a predominantly fossil carbon source for marine gas hydrate, but also indicate that structural gas hydrate from at least certain cold seeps contains a component of methane produced during decomposition of non-fossil organic matter in near-surface sediment.

  6. Physical properties of hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Waite, W. F.; Santamarina, J. C.; Cortes, D. D.; Dugan, B.; Espinoza, D. N.; Germaine, J.; Jang, J.; Jung, J. W.; Kneafsey, T. J.; Shin, H.; Soga, K.; Winters, W. J.; Yun, T.-S.

    2009-12-01

    Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

  7. HyFlux - Part II: Subsurface sequestration of methane-derived carbon in gas-hydrate- bearing marine sediments

    NASA Astrophysics Data System (ADS)

    Naehr, T. H.; Asper, V. L.; Garcia, O.; Kastner, M.; Leifer, I.; MacDonald, I. R.; Solomon, E. A.; Yvon-Lewis, S.; Zimmer, B.

    2008-12-01

    The recently funded DOE/NETL study "HyFlux: Remote sensing and sea-truth measurements of methane flux to the atmosphere" (see MacDonald et al.: HyFlux - Part I) will combine sea surface, water column and shallow subsurface observations to improve our estimates of methane flux from submarine seeps and associated gas hydrate deposits to the water column and atmosphere along the Gulf of Mexico continental margin and other selected areas world-wide. As methane-rich fluids rise towards the sediment-water interface, they will interact with sulfate-rich pore fluids derived from overlying bottom water, which results in the formation of an important biogeochemical redox boundary, the so-called sulfate-methane interface, or SMI. Both methane and sulfate are consumed within the SMI and dissolved inorganic carbon, mostly bicarbonate (HCO3-) and hydrogen sulfide are produced, stimulating authigenic carbonate precipitation at and immediately below the SMI. Accordingly, the formation of authigenic carbonates in methane- and gas-hydrate-rich sediments will sequester a portion of the methane-derived carbon. To date, however, little is known about the quantitative aspects of these reactions. Rates of DIC production are not well constrained, but recent biogeochemical models indicate that CaCO3 precipitation rates may be as high as 120 μmol cm-2a-1. Therefore, AOM-driven carbonate precipitation must be considered when assessing the impact of gas-hydrate-derived methane on the global carbon cycle. As part of HyFlux, we will conduct pore water analyses (DOC, DIC, CH4, δ13CDIC, δ13CDOC, δ13CCH4, δ18O, and δD isotope ratios) to evaluate the importance of authigenic carbonate precipitation as a sequestration mechanism for methane- derived carbon. In addition, sediment and seafloor carbonate samples will be analyzed for bulk sedimentary carbonate (δ13C and δ18O) and bulk sedimentary organic matter (δ13C and δ15N), as well as sulfur, bulk mineralogy, texture and morphological

  8. Pore-scale Numerical Simulation Using Lattice Boltzmann Method for Mud Erosion in Methane Hydrate Bearing Layers

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Sato, T.; Oyama, H.

    2014-12-01

    Methane hydrates in subsea environments near Japan are believed to new natural gas resources. These methane hydrate crystals are very small and existed in the intergranular pores of sandy sediments in sand mud alternate layers. For gas production, several processes for recovering natural gas from the methane hydrate in a sedimentary reservoir have been proposed, but almost all technique are obtain dissociated gas from methane hydrates. When methane hydrates are dissociated, gas and water are existed. These gas and water are flown in pore space of sand mud alternate layers, and there is a possibility that the mud layer is eroded by these flows. It is considered that the mad erosion causes production trouble such as making skins or well instability. In this study, we carried out pore scale numerical simulation to represent mud erosion. This research aims to develop a fundamental simulation method based on LBM (Lattice Boltzmann Method). In the simulation, sand particles are generated numerically in simulation area which is approximately 200x200x200μm3. The periodic boundary condition is used except for mud layers. The water/gas flow in pore space is calculated by LBM, and shear stress distribution is obtained at the position flow interacting mud surface. From this shear stress, we consider that the driving force of mud erosion. As results, mud erosion can be reproduced numerically by adjusting the parameters such as critical shear stress. We confirmed that the simulation using LBM is appropriate for mud erosion.

  9. Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?

    USGS Publications Warehouse

    Malinverno, A.; Pohlman, J.W.

    2011-01-01

    The sulfate-methane transition (SMT), a biogeochemical zone where sulfate and methane are metabolized, is commonly observed at shallow depths (1-30 mbsf) in methane-bearing marine sediments. Two processes consume sulfate at and above the SMT, anaerobic oxidation of methane (AOM) and organoclastic sulfate reduction (OSR). Differentiating the relative contribution of each process is critical to estimate methane flux into the SMT, which, in turn, is necessary to predict deeper occurrences of gas hydrates in continental margin sediments. To evaluate the relative importance of these two sulfate reduction pathways, we developed a diagenetic model to compute the pore water concentrations of sulfate, methane, and dissolved inorganic carbon (DIC). By separately tracking DIC containing 12C and 13C, the model also computes ??13C-DIC values. The model reproduces common observations from methane-rich sediments: a well-defined SMT with no methane above and no sulfate below and a ??13C-DIC minimum at the SMT. The model also highlights the role of upward diffusing 13C-enriched DIC in contributing to the carbon isotope mass balance of DIC. A combination of OSR and AOM, each consuming similar amounts of sulfate, matches observations from Site U1325 (Integrated Ocean Drilling Program Expedition 311, northern Cascadia margin). Without AOM, methane diffuses above the SMT, which contradicts existing field data. The modeling results are generalized with a dimensional analysis to the range of SMT depths and sedimentation rates typical of continental margins. The modeling shows that AOM must be active to establish an SMT wherein methane is quantitatively consumed and the ??13C-DIC minimum occurs. The presence of an SMT generally requires active AOM. Copyright 2011 by the American Geophysical Union.

  10. Geomechanical Modeling of Gas Hydrate Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Sanchez, M. J.; Gai, X., Sr.

    2015-12-01

    This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.

  11. Ocean Bottom Gamma-Ray Anomaly Around Methane Seeps Related to Gas Hydrate- Bearing Zone in The Eastern Margin of Japan Sea and Off Southwest Taiwan

    NASA Astrophysics Data System (ADS)

    Machiyama, H.; Kinoshita, M.; Lin, S.; Matsumoto, R.; Soh, W.

    2008-12-01

    JAMSTEC has conducted the ocean bottom gamma-ray measurement using ROVs and Submersibles since 1997. Gamma-ray spectrometer utilizes 3-inch spherical NaI(Tl) scintillator and the signal processor including DA converter in a pressure case. After processing data, we get total count rate (intensity value: count per second (cps)) of gamma ray and contents of K, U-, and Th-series radionuclides. The sensor was equipped to the side of the sample basket or foot of ROVs and submersibles, and always touches the seafloor when ROVs completely landed. Their results are posted on JAMSTEC website as a database. On the basis of past achievements, we present the results of the ocean bottom gamma-ray measurement at the methane seep sites related to gas hydrate off Joetsu in the eastern margin of Japan Sea and off southwest Taiwan. Off Joetsu: A number of mounds, large pockmarks (20 - 50 m deep and 200 - 500 m across), gas plumes, and gas hydrate are found at water depth of 900 - 1000 m in the Umitaka Spur and the Joetsu Knoll. Gamma-ray intensity values are 50 - 70 cps in normal muddy seafloor. On the other hand, the intensity values are 100 - 200 cps around methane venting sites, bacteria mats, and 'collapsed hydrate zone' which has an undulating, rugged seafloor with carbonate nodules and gravels. Contents of each radionuclide are also high. Low U/Th ratio suggests that there is less contribution of Rn accompanied with a recent fault activity. Off southwest Taiwan: Large, dense chemosynthetic communities, associated with carbonate pavements, were discovered at water depth of about 1100 - 1200 m on the top of the Formosa Ridge. Gamma-ray intensity values in normal muddy seafloor (120 - 150 cps) are higher than those around Japan. Since Th-series radionuclide easily absorbs other particles, it is commonly included in surface sediments. This may cause higher content of Th-series radionuclide in normal muddy seafloor. On the other hand, anomaly of gamma-ray intensity (200 - 300 cps

  12. Permeability and porosity of hydrate-bearing sediments in the northern Gulf of Mexico

    SciTech Connect

    Daigle, Hugh; Cook, Ann; Malinverno, Alberto

    2015-10-14

    Hydrate-bearing sands are being actively explored because they contain the highest concentrations of hydrate and are the most economically recoverable hydrate resource. However, relatively little is known about the mechanisms or timescales of hydrate formation, which are related to methane supply, fluid flux, and host sediment properties such as permeability. We used logging-while-drilling data from locations in the northern Gulf of Mexico to develop an effective medium theory-based model for predicting permeability based on clay-sized sediment fraction. The model considers permeability varying between sand and clay endpoint permeabilities that are defined from laboratory data. We verified the model using permeability measurements on core samples from three boreholes, and then used the model to predict permeability in two wells drilled in Walker Ridge Block 313 during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II expedition in 2009. We found that the cleanest sands (clay-sized fraction <0.05) had intrinsic (hydrate-free) permeability contrasts of 5-6 orders of magnitude with the surrounding clays, which is sufficient to provide focused hydrate formation due to advection of methane from a deep source or diffusion of microbial methane from nearby clay layers. In sands where the clay-sized fraction exceeds 0.05, the permeability reduces significantly and focused flow is less pronounced. In these cases, diffusion of dissolved microbial methane is most likely the preferred mode of methane supply for hydrate formation. In conclusion, our results provide important constraints on methane supply mechanisms in the Walker Ridge area and have global implications for evaluating rates of methane migration and hydrate formation in hydrate-bearing sands.

  13. Permeability and porosity of hydrate-bearing sediments in the northern Gulf of Mexico

    DOE PAGES

    Daigle, Hugh; Cook, Ann; Malinverno, Alberto

    2015-10-14

    Hydrate-bearing sands are being actively explored because they contain the highest concentrations of hydrate and are the most economically recoverable hydrate resource. However, relatively little is known about the mechanisms or timescales of hydrate formation, which are related to methane supply, fluid flux, and host sediment properties such as permeability. We used logging-while-drilling data from locations in the northern Gulf of Mexico to develop an effective medium theory-based model for predicting permeability based on clay-sized sediment fraction. The model considers permeability varying between sand and clay endpoint permeabilities that are defined from laboratory data. We verified the model using permeabilitymore » measurements on core samples from three boreholes, and then used the model to predict permeability in two wells drilled in Walker Ridge Block 313 during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II expedition in 2009. We found that the cleanest sands (clay-sized fraction <0.05) had intrinsic (hydrate-free) permeability contrasts of 5-6 orders of magnitude with the surrounding clays, which is sufficient to provide focused hydrate formation due to advection of methane from a deep source or diffusion of microbial methane from nearby clay layers. In sands where the clay-sized fraction exceeds 0.05, the permeability reduces significantly and focused flow is less pronounced. In these cases, diffusion of dissolved microbial methane is most likely the preferred mode of methane supply for hydrate formation. In conclusion, our results provide important constraints on methane supply mechanisms in the Walker Ridge area and have global implications for evaluating rates of methane migration and hydrate formation in hydrate-bearing sands.« less

  14. Attenuation measurements from sonic waveform logs in methane hydrate-bearing sediments at the Nankai Trough exploratory well off Tokai, central Japan

    NASA Astrophysics Data System (ADS)

    Matsushima, Jun

    2005-02-01

    I have used full waveform logs from the Nankai Trough exploratory well off central Japan to estimate both compressional and shear attenuation in sediments containing methane hydrate (MH). The attenuation estimates are based on a median frequency shift to the amplitude spectrum of the recorded waveforms. This paper is concerned with attenuation at sonic frequencies of 10-20 kHz for compressional waves and 500-1000 Hz for shear waves. I observed that the presence of MH increases the host sediments' seismic attenuation, and shear attenuation may be more helpful than compressional attenuation in detecting or characterizing MH-bearing sediments as compressional attenuation is affected by the presence of gas. Moreover, the ratio of compressional to shear attenuation is found to be a more sensitive indicator of the presence of low-saturation gas than the corresponding velocity ratio.

  15. P-wave velocity features of methane hydrate-bearing turbidity sediments sampled by a pressure core tool, from the first offshore production test site in the eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Suzuki, K.; Santamarina, C. J.; Waite, W. F.; Winters, W. J.; Ito, T.; Nakatsuka, Y.; Konno, Y.; Yoneda, J.; Kida, M.; Jin, Y.; Egawa, K.; Fujii, T.; Nagao, J.

    2013-12-01

    Turbidite sediments around the production test site at Daini-Atsumi knoll were deposited under channel and lobe environments of a submarine fan. Changes in physical properties of the sediments are likely caused by differences in the depositional environments. In addition, methane hydrate (MH) crystals growing among sediment grains alter the sediment's original physical properties. Thus, distinguishing between hydrate-bearing sediment and hydrate-free sediment based only on physical property changes measured during downhole logging can be difficult. To more precisely analyze sediment properties, core samples of MH-bearing sediments were taken at the first offshore MH production test site. Samples were collected using a wireline hybrid pressure coring system (Hybrid PCS), which retains downhole pressure, thereby preventing dissociation of MH in the sampled cores. Nondestructive, high-pressure analyses were conducted in both the 2012 summer drilling campaign and a 2013 winter laboratory study in Sapporo. To handle Hybrid PCS cores during the pressure coring campaign in the summer of 2012, a pressure core analysis and transfer system (PCATS) was installed on the research vessel Chikyu (Yamamoto et al., 2012). PCATS P-wave velocity measurements were made at in situ water pressure without causing any core destruction or MH dissociation. In January 2013, Georgia Tech (GT), USGS, AIST, and JOGMEC researchers used pressure core characterization tools (PCCTs) developed by GT to re-measure the P-wave velocity of the MH-bearing sediments at high pressure and low, non-freezing temperature. In the PCATS analysis, results showed a difference of more than 1,200 m/s in P-wave velocities between the MH-bearing sandy and muddy layers. This difference in P-wave velocities was confirmed by PCCTs measurements. P-wave velocities within the turbidite interval tend to decrease upward with the textural grading of the turbidite. Our result implies that MH concentration, which is related to

  16. Comparison of Rock Physics Properties of Tetrahydrofuran and Cyclopentane Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Schindler, M.; Batzle, M. L.

    2013-12-01

    Laboratory rock physics measurements of gas hydrate-bearing sediments provided calibration for field geophysical data. The manner of how the hydrate is formed in the sediment will thereby affect the physical properties of the hydrated sediment. Methane hydrates in nature form either from the free or dissolved gas phase. MXCT images of tetrahydrofuran (THF) and cyclopentane (CP) hydrate-bearing porous media show that the manner of hydrate formation determines the hydrate distribution within the pore space. CP, which is immiscible in water forms hydrate that tends to be located at the grain contacts, whereas THF hydrate, which is formed out of solution, tends to occur in the pore space away from the grains. Consequently, we use THF and CP as proxy for CH4 in solution and as free gas phase, respectively. In addition, ultrasonic velocity measurements are conducted as a function of confining pressure on both types of hydrate-bearing porous media. Glass beads and unconsolidated quartz sand are used as host sediment. To form the THF hydrate-bearing samples, THF-water solution is mixed and injected into the dry and vacuumed sample. The ratio of THF to water determines the resulting hydrate saturation. CP hydrate-bearing samples are generated by injecting CP into partially water-saturated samples. Here, the initial water saturation determines the resulting hydrate saturation. Samples with hydrate saturations of 0, 40, 60, 80, and 100 percent are tested. In both cases hydrates are formed by slowly cooling the samples into the respective hydrate stability zone, which for both types of samples lies at temperatures above 273 K at atmospheric pressure. The results show an increase in velocity with hydrate saturation in both cases. Velocities of hydrate-bearing glass beads tend to be elevated compared to hydrate-bearing quartz sand. Analysis is still ongoing, but it is expected that the cyclopentane hydrate-bearing samples will exhibit a more significant increase in velocities

  17. Thermal conductivity of hydrate-bearing sediments

    USGS Publications Warehouse

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

  18. A Trial of the Delineation of Gas Hydrate Bearing Zones using Seismic Methods Offshore Tokai Japan

    NASA Astrophysics Data System (ADS)

    Inamori, T.; Hato, M.

    2002-12-01

    MITI Research Well 'Nankai Trough' was drilled at offshore Tokai Japan in 1999/2000 and the existence of gas hydrate was confirmed by various proofs through borehole measurement or coring. It gave so big impact to the view of Japan_fs future energy resources and other scientific interests.The METI, Ministry of Economy, Trade and Industry, has started the national project "Methane Hydrate Exploration study" in Japan since the fall 2001. Bottom Simulating Reflectors (BSRs) were widely found on the marine seismic data acquired offshore Japan especially in the shelf-slope near Nankai Trough. BSRs are thought to be the bottom of gas hydrate stability zones, we cannot, however, get the information of gas hydrate bearing zones, such as the height of those, the porosity, the gas hydrate saturation etc, only from BSRs. In order to estimate the amount of gas hydrate accurately, we have to get those reservoir parameters of gas hydrate bearing zones from marine seismic data. The velocity of these zones is greater than that of the surrounding sediment, because pure gas hydrate has high velocity that is more than 3,000 m/s. This means the interval velocity is the key for exploration of gas hydrate. First, we have tried to image the gas hydrate bearing zones from seismic stacking velocity analysis. After the conversion to interval velocity from NMO velocity by Dix's equation, we imaged the P-wave velocity section through 2D seismic line. We successfully imaged high velocity zones above BSRs and low velocity zones beneath BSRs on P-wave velocity section. But the resolution of the section from the velocity analysis is not so high. Although we have only two adjacent well log data on the seismic line, in order to make more detailed map, we tried to execute the seismic impedance inversion with MITI Nankai Trough Well data. We made a simple initial model and inverted to seismic impedance value. We got the good impedance section and delineated the gas hydrate bearing zones through it

  19. Elastic properties of gas hydrate-bearing sediments

    USGS Publications Warehouse

    Lee, M.W.; Collett, T.S.

    2001-01-01

    Downhole-measured compressional- and shear-wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate-bearing sediments is as a pore-filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field-observed velocities; however, the weighted equation more accurately describes the compressional- and shear-wave velocities of gas hydrate-bearing sediments. A decrease of Poisson's ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson's ratio with a decrease in the sediment porosity. Poisson's ratios greater than 0.33 for gas hydrate-bearing sediments imply the unconsolidated nature of gas hydrate-bearing sediments at this well site. The seismic characteristics of gas hydrate-bearing sediments at this site can be used to compare and evaluate other gas hydrate-bearing sediments in the Arctic.

  20. Multi-property characterization chamber for geophysical-hydrological investigations of hydrate bearing sediments

    SciTech Connect

    Seol, Yongkoo Choi, Jeong-Hoon; Dai, Sheng

    2014-08-01

    With the increase in the interest of producing natural gas from methane hydrates as well as potential risks of massive hydrate dissociation in the context of global warming, studies have recently shifted from pure hydrate crystals to hydrates in sediments. Such a research focus shift requires a series of innovative laboratory devices that are capable of investigating various properties of hydrate-bearing sediments (HBS). This study introduces a newly developed high pressure testing chamber, i.e., multi-property characterization chamber (MPCC), that allows simultaneous investigation of a series of fundamental properties of HBS, including small-strain stiffness (i.e., P- and S-waves), shear strength, large-strain deformation, stress-volume responses, and permeability. The peripheral coolant circulation system of the MPCC permits stable and accurate temperature control, while the core holder body, made of aluminum, enables X-ray computer tomography scanning to be easily employed for structural and morphological characterization of specimens. Samples of hydrate-bearing sediments are held within a rubber sleeve inside the chamber. The thick sleeve is more durable and versatile than thin membranes while also being much softer than oedometer-type chambers that are incapable of enabling flow tests. Bias introduced by the rubber sleeve during large deformation tests are also calibrated both theoretically and experimentally. This system provides insight into full characterization of hydrate-bearing sediments in the laboratory, as well as pressure core technology in the field.

  1. Multi-property characterization chamber for geophysical-hydrological investigations of hydrate bearing sediments.

    PubMed

    Seol, Yongkoo; Choi, Jeong-Hoon; Dai, Sheng

    2014-08-01

    With the increase in the interest of producing natural gas from methane hydrates as well as potential risks of massive hydrate dissociation in the context of global warming, studies have recently shifted from pure hydrate crystals to hydrates in sediments. Such a research focus shift requires a series of innovative laboratory devices that are capable of investigating various properties of hydrate-bearing sediments (HBS). This study introduces a newly developed high pressure testing chamber, i.e., multi-property characterization chamber (MPCC), that allows simultaneous investigation of a series of fundamental properties of HBS, including small-strain stiffness (i.e., P- and S-waves), shear strength, large-strain deformation, stress-volume responses, and permeability. The peripheral coolant circulation system of the MPCC permits stable and accurate temperature control, while the core holder body, made of aluminum, enables X-ray computer tomography scanning to be easily employed for structural and morphological characterization of specimens. Samples of hydrate-bearing sediments are held within a rubber sleeve inside the chamber. The thick sleeve is more durable and versatile than thin membranes while also being much softer than oedometer-type chambers that are incapable of enabling flow tests. Bias introduced by the rubber sleeve during large deformation tests are also calibrated both theoretically and experimentally. This system provides insight into full characterization of hydrate-bearing sediments in the laboratory, as well as pressure core technology in the field. PMID:25173288

  2. Stability evaluation of hydrate-bearing sediments during thermally-driven hydrate dissociation

    NASA Astrophysics Data System (ADS)

    Kwon, T.; Cho, G.; Santamarina, J.; Kim, H.; Lee, J.

    2009-12-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations, or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. This study examined how thermal changes destabilize gas hydrate-bearing sediments. First, an analytical formulation was derived for predicting fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation captures the self-preservation behavior, calculates the hydrate and free gas quantities during dissociation, considering effective stress-controlled sediment compressibility and gas solubility in aqueous phase. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. Second, the analytical formulation for hydrate dissociation was incorporated as a user-defined function into a verified finite difference code (FLAC2D). The underlying physical processes of hydrate-bearing sediments, including hydrate dissociation, self-preservation, pore pressure evolution, gas dissolution, and sediment volume expansion, were coupled with the thermal conduction, pore fluid flow, and mechanical response of sediments. We conducted the simulations for a duration of 20 years, assuming a constant-temperature wellbore transferred heat to the surrounding hydrate-bearing sediments, resulting in dissociation of methane hydrate in the well vicinity. The model predicted dissociation-induced excess pore fluid pressures which resulted in a large volume expansion and plastic deformation of the sediments. Furthermore, when the critical stress was reached, localized shear failure of the sediment around the borehole was

  3. Strengthening mechanism of cemented hydrate-bearing sand at microscales

    NASA Astrophysics Data System (ADS)

    Yoneda, Jun; Jin, Yusuke; Katagiri, Jun; Tenma, Norio

    2016-07-01

    On the basis of hypothetical particle-level mechanisms, several constitutive models of hydrate-bearing sediments have been proposed previously for gas production. However, to the best of our knowledge, the microstructural large-strain behaviors of hydrate-bearing sediments have not been reported to date because of the experimental challenges posed by the high-pressure and low-temperature testing conditions. Herein, a novel microtriaxial testing apparatus was developed, and the mechanical large-strain behavior of hydrate-bearing sediments with various hydrate saturation values (Sh = 0%, 39%, and 62%) was analyzed using microfocus X-ray computed tomography. Patchy hydrates were observed in the sediments at Sh = 39%. The obtained stress-strain relationships indicated strengthening with increasing hydrate saturation and a brittle failure mode of the hydrate-bearing sand. Localized deformations were quantified via image processing at the submillimeter and micrometer scale. Shear planes and particle deformation and/or rotation were detected, and the shear band thickness decreased with increasing hydrate saturation.

  4. Water retention curve for hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Dai, Sheng; Santamarina, J. Carlos

    2013-11-01

    water retention curve plays a central role in numerical algorithms that model hydrate dissociation in sediments. The determination of the water retention curve for hydrate-bearing sediments faces experimental difficulties, and most studies assume constant water retention curves regardless of hydrate saturation. This study employs network model simulation to investigate the water retention curve for hydrate-bearing sediments. Results show that (1) hydrate in pores shifts the curve to higher capillary pressures and the air entry pressure increases as a power function of hydrate saturation; (2) the air entry pressure is lower in sediments with patchy rather than distributed hydrate, with higher pore size variation and pore connectivity or with lower specimen slenderness along the flow direction; and (3) smaller specimens render higher variance in computed water retention curves, especially at high water saturation Sw > 0.7. Results are relevant to other sediment pore processes such as bioclogging and mineral precipitation.

  5. Novel integrons and gene cassettes from a Cascadian submarine gas-hydrate-bearing core.

    PubMed

    Elsaied, Hosam; Stokes, Hatch W; Yoshioka, Hideyoshi; Mitani, Yasuo; Maruyama, Akihiko

    2014-02-01

    To determine whether integrons are present in a submarine gas hydrate community, metagenomic DNA was extracted from a gas-hydrate-bearing core, 150 m below the seafloor, from the Cascadian Margin. Integrons and gene cassettes were recovered by PCR from metagenomic DNA and sequenced. Thirty-seven integron integrase phylotypes were identified. The phylotypes were diverse and included members with homology to integrases from Methylomonas methanica, Desulfuromonas acetoxidans, Thermodesulfatator indicus, and marine uncultured bacteria. The gene cassette composition, 153 gene cassettes, was dominated by two types of encoded putative proteins. The first of these was predicted oxidoreductases, such as iron/sulfur cluster-binding proteins. A second type was alkyl transferases. Some cassette proteins showed homologies with those from methane-related archaea. These observations suggest that integrons may assist in the adaptation of microbial communities in this environment. PMID:24117886

  6. Investigation of mechanical properties of hydrate-bearing pressure core sediments recovered from the Eastern Nankai Trough using transparent acrylic cell triaxial testing system (TACTT-system)

    NASA Astrophysics Data System (ADS)

    Yoneda, J.; Masui, A.; Konno, Y.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Tenma, N.; Nagao, J.

    2014-12-01

    Natural gas hydrate-bearing pressure core sediments have been sheared in compression using a newly developed Transparent Acrylic Cell Triaxial Testing (TACTT) system to investigate the geophysical and geomechanical behavior of sediments recovered from the deep seabed in the Eastern Nankai Trough, the first Japanese offshore production test region. The sediments were recovered by hybrid pressure core system (hybrid PCS) and pressure cores were cut by pressure core analysis tools (PCATs) on board. These pressure cores were transferred to the AIST Hokkaido centre and trimmed by pressure core non-destructive analysis tools (PNATs) for TACTT system which maintained the pressure and temperature conditions within the hydrate stability boundary, through the entire process of core handling from drilling to the end of laboratory testing. An image processing technique was used to capture the motion of sediment in a transparent acrylic cell, and digital photographs were obtained at every 0.1% of vertical strain during the test. Analysis of the optical images showed that sediments with 63% hydrate saturation exhibited brittle failure, although nonhydrate-bearing sediments exhibited ductile failure. In addition, the increase in shear strength with hydrate saturation increase of natural gas hydrate is in agreement with previous data from synthetic gas hydrate. This research was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program by the Ministry of Economy, Trade and Industry (METI).

  7. Gas Production from Hydrate-Bearing Sediments - Emergent Phenomena -

    SciTech Connect

    Jung, J.W.; Jang, J.W.; Tsouris, Costas; Phelps, Tommy Joe; Rawn, Claudia J; Santamarina, Carlos

    2012-01-01

    Even a small fraction of fine particles can have a significant effect on gas production from hydrate-bearing sediments and sediment stability. Experiments were conducted to investigate the role of fine particles on gas production using a soil chamber that allows for the application of an effective stress to the sediment. This chamber was instrumented to monitor shear-wave velocity, temperature, pressure, and volume change during CO{sub 2} hydrate formation and gas production. The instrumented chamber was placed inside the Oak Ridge National Laboratory Seafloor Process Simulator (SPS), which was used to control the fluid pressure and temperature. Experiments were conducted with different sediment types and pressure-temperature histories. Fines migrated within the sediment in the direction of fluid flow. A vuggy structure formed in the sand; these small cavities or vuggs were precursors to the development of gas-driven fractures during depressurization under a constant effective stress boundary condition. We define the critical fines fraction as the clay-to-sand mass ratio when clays fill the pore space in the sand. Fines migration, clogging, vugs, and gas-driven fracture formation developed even when the fines content was significantly lower than the critical fines fraction. These results show the importance of fines in gas production from hydrate-bearing sediments, even when the fines content is relatively low.

  8. Physical property changes in hydrate-bearing sediment due to depressurization and subsequent repressurization

    USGS Publications Warehouse

    Waite, W.F.; Kneafsey, T.J.; Winters, W.J.; Mason, D.H.

    2008-01-01

    Physical property measurements of sediment cores containing natural gas hydrate are typically performed on material exposed, at least briefly, to non-in situ conditions during recovery. To examine the effects of a brief excursion from the gas-hydrate stability field, as can occur when pressure cores are transferred to pressurized storage vessels, we measured physical properties on laboratory-formed sand packs containing methane hydrate and methane pore gas. After depressurizing samples to atmospheric pressure, we repressurized them into the methane-hydrate stability field and remeasured their physical properties. Thermal conductivity, shear strength, acoustic compressional and shear wave amplitudes, and speeds of the original and depressurized/repressurized samples are compared. X-ray computed tomography images track how the gas-hydrate distribution changes in the hydrate-cemented sands owing to the depressurizaton/repressurization process. Because depressurization-induced property changes can be substantial and are not easily predicted, particularly in water-saturated, hydrate-bearing sediment, maintaining pressure and temperature conditions throughout the core recovery and measurement process is critical for using laboratory measurements to estimate in situ properties.

  9. Response of oceanic hydrate-bearing sediments to thermalstresses

    SciTech Connect

    Moridis, G.J.; Kowalsky, M.B.

    2006-05-01

    In this study, we evaluate the response of oceanicsubsurface systems to thermal stresses caused by the flow of warm fluidsthrough noninsulated well systems crossing hydrate-bearing sediments.Heat transport from warm fluids, originating from deeper reservoirs underproduction, into the geologic media can cause dissociation of the gashydrates. The objective of this study is to determine whether gasevolution from hydrate dissociation can lead to excessive pressurebuildup, and possibly to fracturing of hydrate-bearing formations andtheir confining layers, with potentially adverse consequences on thestability of the suboceanic subsurface. This study also aims to determinewhether the loss of the hydrate--known to have a strong cementing effecton the porous media--in the vicinity of the well, coupled with thesignificant pressure increases, can undermine the structural stability ofthe well assembly.Scoping 1D simulations indicated that the formationintrinsic permeability, the pore compressibility, the temperature of theproduced fluids andthe initial hydrate saturation are the most importantfactors affecting the system response, while the thermal conductivity andporosity (above a certain level) appear to have a secondary effect.Large-scale simulations of realistic systems were also conducted,involving complex well designs and multilayered geologic media withnonuniform distribution of properties and initial hydrate saturationsthat are typical of those expected in natural oceanic systems. Theresults of the 2D study indicate that although the dissociation radiusremains rather limited even after long-term production, low intrinsicpermeability and/or high hydrate saturation can lead to the evolution ofhigh pressures that can threaten the formation and its boundaries withfracturing. Although lower maximum pressures are observed in the absenceof bottom confining layers and in deeper (and thus warmer and morepressurized) systems, the reduction is limited. Wellbore designs withgravel

  10. Transformations in methane hydrates

    USGS Publications Warehouse

    Chou, I.-Ming; Sharma, A.; Burruss, R.C.; Shu, J.; Mao, Ho-kwang; Hemley, R.J.; Goncharov, A.F.; Stern, L.A.; Kirby, S.H.

    2000-01-01

    Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) A?? and volume V = 5051.3(13) A??3; structure H at 600 MPa has a hexagonal unit cell of a = 11.980(2) A??, c = 9.992(3) A??, and V = 1241.9(5) A??3. The compositions of these two investigated phases are still not known. With the effects of pressure and the presence of other gases in the structure, the structure II phase is likely to dominate over the known structure I methane hydrate within deep hydrate-bearing sediments underlying continental margins.

  11. Sedimentological Properties of Natural Gas Hydrates-Bearing Sands in the Nankai Trough and Mallik Areas

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Tsuji, T.; Waseda, A.

    2009-12-01

    The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys have definitely indicated gas hydrate distributions, and drilling the MITI Nankai Trough wells in 2000 and the METI Tokai-oki to Kumano-nada wells in 2004 have revealed subsurface gas hydrate in the eastern part of Nankai Trough. In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that also clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. During the field operations, the LWD and wire-line well log data were continuously obtained and plenty of gas hydrate-bearing sand cores were recovered. Subsequence sedimentological and geochemical analyses performed on those core samples revealed the crucial geologic controls on the formation and preservation of natural gas hydrate in sediments. Pore-space gas hydrates reside in sandy sediments mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space gas hydrates within moderate to thick sandy layers, typically 10 cm to a meter thick. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 45 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. Gas hydrate saturations are typically up to 80 % in pore volume throughout most of the hydrate-dominant sandy layers, which are estimated by well log analyses as well as pore water chloride anomalies. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicated that highly saturated

  12. Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

    SciTech Connect

    Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

    2008-03-31

    The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

  13. Crosswell seismic studies in gas hydrate-bearing sediments: P wave velocity and attenuation tomography

    NASA Astrophysics Data System (ADS)

    Bauer, K.; Haberland, Ch.; Pratt, R. G.; Ryberg, T.; Weber, M. H.; Mallik Working Group

    2003-04-01

    We present crosswell seismic data from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. The crosswell seismic measurements were carried out by making use of two 1160 m deep observation wells (Mallik 3L-38 and 4L-38) both 45 m from and co-planar with the 1188 m deep production research well (5L-38). A high power piezo-ceramic source was used to generate sweeped signals with frequencies between 100 and 2000 Hz recorded with arrays of 8 hydrophones per depth level. A depth range between 800 and 1150 m was covered, with shot and receiver spacings of 0.75 m. High quality data could be collected during the survey which allow for application of a wide range of crosswell seismic methods. The initial data analysis included suppression of tube wave energy and picking of first arrivals. A damped least-squares algorithm was used to derive P-wave velocities from the travel time data. Next, t* values were derived from the decay of the amplitude spectra, which served as input parameters for a damped least-squares attenuation tomography. The initial results of the P-wave velocity and attenuation tomography reveal significant features reflecting the stratigraphic environment and allow for detection and eventually quantification of gas hydrate bearing sediments. A prominent correlation between P velocity and attenuation was found for the gas hydrate layers. This contradicts to the apparently more meaningful inverse correlation as it was determined for the gas hydrates at the Blake Ridge but supports the results from

  14. Microbial production and oxidation of methane in deep subsurface

    NASA Astrophysics Data System (ADS)

    Kotelnikova, Svetlana

    2002-10-01

    The goal of this review is to summarize present studies on microbial production and oxidation of methane in the deep subterranean environments. Methane is a long-living gas causing the "greenhouse" effect in the planet's atmosphere. Earlier, the deep "organic carbon poor" subsurface was not considered as a source of "biogenic" methane. Evidence of active methanogenesis and presence of viable methanogens including autotrophic organisms were obtained for some subsurface environments including water-flooded oil-fields, deep sandy aquifers, deep sea hydrothermal vents, the deep sediments and granitic groundwater at depths of 10 to 2000 m below sea level. As a rule, the deep subterranean microbial populations dwell at more or less oligotrophic conditions. Molecular hydrogen has been found in a variety of subsurface environments, where its concentrations were significantly higher than in the tested surface aquatic environments. Chemolithoautotrophic microorganisms from deep aquifers that could grow on hydrogen and carbon dioxide can act as primary producers of organic carbon, initiating heterotrophic food chains in the deep subterranean environments independent of photosynthesis. "Biogenic" methane has been found all over the world. On the basis of documented occurrences, gases in reservoirs and older sediments are similar and have the isotopic character of methane derived from CO 2 reduction. Groundwater representing the methanogenic end member are characterized by a relative depletion of dissolved organic carbon (DOC) in combination with an enrichment in 13C in inorganic carbon, which is consistent with the preferential reduction of 12CO 2 by autotrophic methanogens or acetogens. The isotopic composition of methane formed via CO 2 reduction is controlled by the δ13C of the original CO 2 substrate. Literature data shows that CH 4 as heavy as -40‰ or -50‰ can be produced by the microbial reduction of isotopically heavy CO 2. Produced methane may be oxidized

  15. Modeling dissociation of hydrate bearing sediments under shear

    NASA Astrophysics Data System (ADS)

    Lin, J. S.; Choi, J. H.; Seol, Y.; Rutqvist, J.

    2015-12-01

    To assess the stability of ground during gas production from hydrate bearing sediments, it is of fundamental importance that the constitutive model employed and the computational procedure adopted are capable and accurate. One way to establish credence is to investigate if observation from laboratory tests could be reproduced in analysis. From this consideration, this study modeled laboratory triaxial tests in which hydrate dissociation was induced when a certain level of shear stress was reached. During the dissociation, however, both the axial and the confining stresses were kept unchanged. There were basically two scenarios observed: If the applied shear stress was higher than the shear strength of the hydrate free host soil, failure would take place during the dissociation; otherwise the sample would remain stable. The dissociation was induced either by a temperature raise or through pore pressure reduction. To model such tests, a coupled procedure was employed: the geomechanical analysis was conducted in FLAC3D, and the multiphase flow was conducted in TOUGH+. In this study, an SMP critical state constitutive model was implemented in the FLAC3D. This study successfully reproduced the observation from the laboratory tests. It showed that if the dissociation was caused by temperature change alone, failure would take place during dissociation. On the other hand, the modeling results also showed that if the dissociation was induced by pressure reduction, a sample could remain stable during dissociation because the effective confining stress was raised, but it would fail afterwards when the pre-association fluid pressure was allowed to return and the pace of hydrate reformation lagged behind.

  16. Geomechanical Performance of Hydrate-Bearing Sediments in Offshore Environments

    SciTech Connect

    Stephen A. Holditch

    2006-12-31

    The main objective of this study is to develop the necessary knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus is on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. To achieve this objective, we have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. To be sure our geomechanical modeling is realistic, we are also investigating the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. In Phase II of the project, we will review all published core data and generate additional core data to verify the models. To generate data for our models, we are using data from the literature and we will be conducting laboratory studies in 2007 that generate data to (1) evaluate the conceptual pore-scale models, (2) calibrate the mathematical models, (3) determine dominant relations and critical parameters defining the geomechanical behavior of HBS, and (4) establish relationships between the geomechanical status of HBS and the corresponding geophysical signature. The milestones for Phase I of this project are given as follows: Literature survey on typical sediments containing gas hydrates in the ocean (TAMU); Recommendations on how to create typical sediments in the laboratory (TAMU); Demonstrate that typical sediments can be created in a repeatable manner in the laboratory and gas hydrates can be created in the pore space (TAMU); Develop a conceptual pore-scale model based on available data and reports (UCB); Test the developed pore-scale concepts on simple configurations and verify the results against known measurements and observations (UCB

  17. Methane in Crystalline Bedrock: the Outokumpu Deep Drill Hole, Finland

    NASA Astrophysics Data System (ADS)

    Kietäväinen, R.; Ahonen, L.; Niinikoski, P.; Itävaara, M.; Kukkonen, I. T.

    2014-12-01

    Carbon is a key element for life. One of the most interesting forms of carbon is methane, as it is both consumed and produced by microorganisms. Methane has also several possible ways of abiotic origin, some of which could provide understanding of the origin of life itself. The study of methane is thus important in order to understand deep subsurface ecosystems such as those found in the 2516 m deep Outokumpu Deep Drill Hole within the Precambrian Fennoscandian Shield in eastern Finland. There rock types differ from graphite-bearing mica schist and black schist to serpentinite and pegmatitic granodiorite and saline, gas-rich water, with up to 32 mmol l-1 of methane, and residence times of tens of millions of years occupies the fracture zones which host diverse microbial life, including methanogenic archaea. In order to understand methane systematics in crystalline bedrock, we analysed several forms of carbon, including dissolved inorganic carbon (DIC), methane and ethane from the Outokumpu Deep Drill Hole for their isotopic composition. In addition, isotopic compositions of water and hydrogen were determined. The results show that hydrogen is in isotopic equilibrium in the system H2O-H2-CH4 at ambient temperatures, which could either indicate equilibration due to long residence time or relatively recent production of methane in situ. Therefore hydrogen is not a very useful indicator for the origin of methane in this case. Carbon isotope analysis shows that both methane and DIC becomes generally more enriched in 13C with depth, which could indicate higher amounts of microbial methane in the upper part of the bedrock. Based on carbon isotope composition, two types of ethane can be discerned. Taken all the evidence together, this leads us to suggest that at least two mechanisms are responsible for the methane production in Outokumpu: 1) Biotic which comprise most of methane and 2) abiotic which dominates in the deeper parts of the bedrock. The former type may include

  18. Impacts of Hydrate Pore Habit on Physical Properties of Hydrate Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Seol, Y.; Dai, S.; Choi, J. H.

    2014-12-01

    The physical properties of gas hydrate bearing sediments, to a large extent, are governed by the volume fraction and spatial distribution of the hydrate phase. For sediments containing the same amount of hydrates, their overall physical properties may vary several orders of magnitude depending on hydrate pore habit. We investigate the interplay among hydrate formation methods, hydrate pore habits, and fundamental physical properties of hydrate bearing sediments. We have developed a new method to synthesize noncementing hydrate in sands, a multi-properties characterization chamber to test the hydrate bearing sediments, and pore network models to simulate fluid flow processes in hydrate bearing sediments. We have found that (1) the growth pattern of hydrate crystal in the pore spaces of water saturated sediments is dominated by the relative magnitude of the capillary force (between hydrate crystal and pore fluid) and the skeleton force, which will result in pore-filling or grain-displacing type of hydrate pore character; (2) the existing capillary tube models of water permeability in hydrate bearing sediments are sensitive to pore geometry and hydrate pore habit; and (3) preliminary CT results suggest that hydrate nucleation in partially water saturated sands tends to agglomerate in patches, rather than in an uniformly-distributed contact-cementing morphology. Additional CT results with a small amount of fines (5wt%) and visualization via micro-CT of hydrate pore habits in sediments using different hydrate formation methods will be discussed.

  19. Physical property changes in hydrate-bearing sediment samples due to depressurization/repressurization

    NASA Astrophysics Data System (ADS)

    Waite, W. F.; Kneafsey, T. J.; Santamarina, J. C.; Winters, W. J.; Yun, T.; Mason, D. H.; Ruppel, C. D.

    2006-12-01

    Physical property measurements on cores containing natural gas hydrate are typically performed on material exposed to non-in situ conditions at least briefly during recovery. In situ temperature and effective stress are difficult to maintain during core recovery, but pressure-coring systems such as the HYACINTH, Fugro, and IODP PCS can maintain in situ hydrostatic pressure during core retrieval. To simulate effects of transferring pressure-core samples to storage vessels, the USGS conducted physical property measurements on Ottawa sand samples containing methane gas and gas hydrate before and after samples were depressurized out of, then repressurized back into, the gas hydrate stability field. For measurements made along a sample's cylindrical axis, compressional and shear wave speed, shear strength, and thermal conductivity increased 10 to 30 percent following a 5 minute excursion from the gas hydrate stability field. Experiments were conducted in unsaturated sand in the presence of methane gas, and increases in measured physical property values resulting from the repressurization cycle can be attributed to a redistribution of water and gas hydrate within the sample. Redistribution of water and re-formation of gas hydrate is inferred from X- Ray Computed Tomography of a cylindrical hydrate-bearing Ottawa sand sample similar to the USGS samples. During the excursion from the gas hydrate stability field, images collected at the Lawrence Berkeley National Laboratory demonstrate gas hydrate dissociates first at the outer surface, where heat is efficiently transferred from a temperature-controlled bath. Upon repressurizing to stable conditions, gas hydrate remaining near the sample's central axis draws water away from the outer part of the sediment sample, and new gas hydrate grows most rapidly close along the central axis, where the original gas hydrate never dissociated during depressurization. These results can be compared to those obtained by Georgia Tech on water

  20. Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 2. Small-strain mechanical properties

    NASA Astrophysics Data System (ADS)

    Lee, J. Y.; Francisca, F. M.; Santamarina, J. C.; Ruppel, C.

    2010-11-01

    The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, σ'v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate

  1. Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

    2014-12-01

    The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

  2. Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 2. Small-strain mechanical properties

    USGS Publications Warehouse

    Lee, J.Y.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2010-01-01

    The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, δ'v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate

  3. Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake

    PubMed Central

    Deutzmann, Joerg S.; Stief, Peter; Brandes, Josephin; Schink, Bernhard

    2014-01-01

    Anaerobic methane oxidation coupled to denitrification, also known as “nitrate/nitrite-dependent anaerobic methane oxidation” (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments, the close proximity of oxygen- and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were very abundant at deep-water sites (profundal sediment). In profundal sediment, the vertical distribution of M. oxyfera-like bacteria showed a distinct peak in anoxic layers that coincided with the zone of methane oxidation and nitrate consumption, a strong indication for n-damo carried out by M. oxyfera-like bacteria. Both potential n-damo rates calculated from cell densities (660–4,890 µmol CH4⋅m−2⋅d−1) and actual rates calculated from microsensor profiles (31–437 µmol CH4⋅m−2⋅d−1) were sufficiently high to prevent methane release from profundal sediment solely by this process. Additionally, when nitrate was added to sediment cores exposed to anoxic conditions, the n-damo zone reestablished well below the sediment surface, completely preventing methane release from the sediment. We conclude that the previously overlooked n-damo process can be the major methane sink in stable freshwater environments if nitrate is available in anoxic zones. PMID:25472842

  4. Methane-Stimulated Benthic Marine Nitrogen Fixation at Deep-Sea Methane Seeps

    NASA Astrophysics Data System (ADS)

    Dekas, A. E.; Orphan, V.

    2011-12-01

    Biological nitrogen fixation (the conversion of N2 to NH3) is a critical process in the oceans, counteracting the production of N2 gas by dissimilatory bacterial metabolisms and providing a source of bioavailable nitrogen to many nitrogen-limited ecosystems. Although current measurements of N2 production and consumption in the oceans indicate that the nitrogen cycle is not balanced, recent findings on the limits of nitrogen fixation suggest that the perceived imbalance is an artifact of an incomplete assessment of marine diazotrophy. One currently poorly studied and potentially underappreciated habitat for diazotrophic organisms is the sediments of the deep-sea. In the present study we investigate the distribution and magnitude of benthic marine diazotrophy at several active deep-sea methane seeps (Mound 12, Costa Rica; Eel River Basin, CA, USA; Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA). Using 15N2 and 15NH4 sediment incubation experiments followed by single-cell (FISH-NanoSIMS) and bulk isotopic analysis (EA-IRMS), we observed total protein synthesis (15N uptake from 15NH4) and nitrogen fixation (15N update from 15N2). The highest rates of nitrogen fixation observed in the methane seep sediment incubation experiments were over an order of magnitude greater than those previously published from non-seep deep-sea sediments (Hartwig and Stanley, Deep-Sea Research, 1978, 25:411-417). However, methane seep diazotrophy appears to be highly spatially variable, with sediments exhibiting no nitrogen fixation originating only centimeters away from sediments actively incorporating 15N from 15N2. The greatest spatial variability in diazotrophy was observed with depth in the sediment, and corresponded to steep gradients in sulfate and methane. The maximum rates of nitrogen fixation were observed within the methane-sulfate transition zone, where organisms mediating the anaerobic oxidation of methane are typically in high abundance. Additionally, incubation

  5. The effect of hydrate saturation on water retention curves in hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Mahabadi, Nariman; Zheng, Xianglei; Jang, Jaewon

    2016-05-01

    The experimental measurement of water retention curve in hydrate-bearing sediments is critically important to understand the behavior of hydrate dissociation and gas production. In this study, tetrahydrofuran (THF) is selected as hydrate former. The pore habit of THF hydrates is investigated by visual observation in a transparent micromodel. It is confirmed that THF hydrates are not wetting phase on the quartz surface of the micromodel and occupy either an entire pore or part of pore space resulting in change in pore size distribution. And the measurement of water retention curves in THF hydrate-bearing sediments with hydrate saturation ranging from Sh = 0 to Sh = 0.7 is conducted for excess water condition. The experimental results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Based on the experimental results, fitting parameters for van Genuchten equation are suggested for different hydrate saturation conditions.

  6. Development of a Numerical Simulator for Analyzing the Geomechanical Performance of Hydrate-Bearing Sediments

    SciTech Connect

    Rutqvist, Jonny; Rutqvist, J.; Moridis, G.J.

    2008-06-01

    In this paper, we describe the development and application of a numerical simulator that analyzes the geomechanical performance of hydrate-bearing sediments, which may become an important future energy supply. The simulator is developed by coupling a robust numerical simulator of coupled fluid flow, hydrate thermodynamics, and phase behavior in geologic media (TOUGH+HYDRATE) with an established geomechanical code (FLAC3D). We demonstrate the current simulator capabilities and applicability for two examples of geomechanical responses of hydrate bearing sediments during production-induced hydrate dissociation. In these applications, the coupled geomechanical behavior within hydrate-bearing seducements are considered through a Mohr-Coulomb constitutive model, corrected for changes in pore-filling hydrate and ice content, based on laboratory data. The results demonstrate how depressurization-based gas production from oceanic hydrate deposits may lead to severe geomechanical problems unless care is taken in designing the production scheme. We conclude that the coupled simulator can be used to design production strategies for optimizing production, while avoiding damaging geomechanical problems.

  7. Catalysis of carbon monoxide methanation by deep sea manganate minerals

    NASA Technical Reports Server (NTRS)

    Cabrera, A. L.; Maple, M. B.; Arrhenius, G.

    1990-01-01

    The catalytic activity of deep sea manganese nodule minerals for the methanation of carbon monoxide was measured with a microcatalytic technique between 200 and 460 degrees C. The manganate minerals were activated at 248 degrees C by immersion into a stream of hydrogen in which pulses of carbon monoxide were injected. Activation energies for the methanation reaction and hydrogen desorption from the manganate minerals were obtained and compared with those of pure nickel. Similar energy values indicate that the activity of the nodule materials for the reaction appears to be related to the amount of reducible transition metals present in the samples (ca. 11 wt.-%). Since the activity of the nodule minerals per gram is comparable to that of pure nickel, most of the transition metal ions located between manganese oxide layers appear to be exposed and available to catalyze the reaction.

  8. Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

    USGS Publications Warehouse

    Stern, Laura A.; Lorenson, T.D.

    2014-01-01

    We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.

  9. Application of Crunch-Flow Routines to Constrain Present and Past Carbon Fluxes at Gas-Hydrate Bearing Sites

    SciTech Connect

    Torres, Marta

    2014-01-31

    In November 2012, Oregon State University initiated the project entitled: Application of Crunch-Flow routines to constrain present and past carbon fluxes at gas-hydrate bearing sites. Within this project we developed Crunch-Flow based modeling modules that include important biogeochemical processes that need to be considered in gas hydrate environments. Our modules were applied to quantify carbon cycling in present and past systems, using data collected during several DOE-supported drilling expeditions, which include the Cascadia margin in US, Ulleung Basin in South Korea, and several sites drilled offshore India on the Bay of Bengal and Andaman Sea. Specifically, we completed modeling efforts that: 1) Reproduce the compositional and isotopic profiles observed at the eight drilled sites in the Ulleung Basin that constrain and contrast the carbon cycling pathways at chimney (high methane flux) and non-chimney sites (low methane, advective systems); 2) Simulate the Ba record in the sediments to quantify the past dynamics of methane flux in the southern Hydrate Ridge, Cascadia margin; and 3) Provide quantitative estimates of the thickness of individual mass transport deposits (MTDs), time elapsed after the MTD event, rate of sulfate reduction in the MTD, and time required to reach a new steady state at several sites drilled in the Krishna-Godavari (K-G) Basin off India. In addition we developed a hybrid model scheme by coupling a home-made MATLAB code with CrunchFlow to address the methane transport and chloride enrichment at the Ulleung Basins chimney sites, and contributed the modeling component to a study focusing on pore-scale controls on gas hydrate distribution in sediments from the Andaman Sea. These efforts resulted in two manuscripts currently under review, and contributed the modeling component of another pare, also under review. Lessons learned from these efforts are the basis of a mini-workshop to be held at Oregon State University (Feb 2014) to instruct

  10. Comparison of Physical Properties of Marine and Arctic Gas-Hydrate-Bearing Deposits

    NASA Astrophysics Data System (ADS)

    Winters, W. J.; Walker, M.; Collett, T. S.; Bryant, S. L.; Novosel, I.; Wilcox-Cline, R.; Bing, J.; Gomes, M. L.

    2009-12-01

    Gas hydrate (GH) occurs in both marine settings and in arctic environments within a wide variety of sediment types. Grain-size analyses from both environments indicate that intrinsic host-sediment properties have a strong influence on gas-hydrate distribution and morphologic characteristics. Depending on the amount formed or dissociated, gas hydrate can significantly change in situ sediment acoustic, mechanical, and hydraulic properties. The U.S. Geological Survey, in cooperation with the U.S. Dept. of Energy, BP Expl.-Alaska, Nat. GH Prog. of India, Canadian Geological Survey, Int. Ocean Drilling Program, Japan Oil Gas and Metals Nat. Corp., Japan Pet. Expl. Co., Int. Marine Past Global Changes Study (IMAGES) program, and Paleoceanography of the Atlantic and Geochemistry (PAGE) program, determined physical properties from marine and arctic sediments and their relation to the presence of GH. At two arctic sites, the Mount Elbert well on the Alaskan North Slope and the Mallik wells on the Mackenzie Delta, NWT, >10-m thick gas-hydrate-bearing (GHB) sandy deposits are capped by finer-grained sediments that may reduce gas migration. In the Mount Elbert well, average median grain sizes (MGS) for the two thickest GHB deposits are 65 and 60 µm. Finer-grained (average MGS of 9 and 28 µm) sediments have plug permeabilities that are 300 and 14 times smaller than underlying GHB sediment. Average MGS of GHB sediment from the Mallik 2L well is ~ 111 µm, compared to overlying sediment with an average MGS of ~ 32 µm. Gas hydrate morphology in the Gulf of Mexico (GOM) and offshore India is substantially more complex than in the arctic, and is related to pervasive, although not exclusive, finer-grained deposits. Massive, several-cm thick, GH layers were recovered in piston cores in the northern GOM, in sediment with little visible lithologic variability (average MGS ~ 0.8 µm). In wells off the east coast of India, GH was present in sand-rich, fractured clay, and reservoirs

  11. Micro X-ray Computed Tomography Imaging and Ultrasonic Velocity Measurements of Hydrate-Bearing Porous Media

    NASA Astrophysics Data System (ADS)

    Schindler, M.; Prasad, M.; Batzle, M. L.

    2015-12-01

    Naturally occurring gas hydrates contain significant amounts of natural gas which might be produced in the foreseeable future. Thus, it is necessary to understand the pore-space characteristics of hydrate reservoirs, especially the pore-scale distribution of hydrate and its interaction with the sediment. The goal of our research is to examine the distribution of hydrate in the pore space and the influence of hydrate pore-scale distribution on seismic velocities and sonic logs. We conducted laboratory measurements to obtain information about the distribution of hydrate in the pore space of synthetic porous media (glass beads). We used Tetrahydrofuran (THF) as a guest molecule since THF hydrate is a proxy for naturally occuring hydrate. We used micro X-ray computed tomography (MXCT) to image hydrate distribution in the pore space. In addition, we investigated the influence of hydrate saturation and distribution on ultrasonic velocities simultaneously with the MXCT imaging. We installed a torlon vessel and a cooling system in the MXCT scanner which allows us to form hydrate in the MXCT scanner at atmospheric pressure and a temperature of approximately 2°C. Both, MXCT images and ultrasonic velocity measurements, indicate that THF hydrate forms in the pore space while residual brine coats the grain surfaces and fills small pores. Our observations are in accordance with the pore-filling model of the effective medium theory of hydrate-bearing sediments. Based on this knowledge, it may be possible to calibrate seismic and well logging data to calculate the amount of natural gas stored in a hydrate reservoir. This information will help to make decisions regarding the producibility of methane hydrates and to develop safe production schemes.

  12. Biot-Gassmann theory for velocities of gas hydrate-bearing sediments

    USGS Publications Warehouse

    Lee, M.W.

    2002-01-01

    Elevated elastic velocities are a distinct physical property of gas hydrate-bearing sediments. A number of velocity models and equations (e.g., pore-filling model, cementation model, effective medium theories, weighted equations, and time-average equations) have been used to describe this effect. In particular, the weighted equation and effective medium theory predict reasonably well the elastic properties of unconsolidated gas hydrate-bearing sediments. A weakness of the weighted equation is its use of the empirical relationship of the time-average equation as one element of the equation. One drawback of the effective medium theory is its prediction of unreasonably higher shear-wave velocity at high porosities, so that the predicted velocity ratio does not agree well with the observed velocity ratio. To overcome these weaknesses, a method is proposed, based on Biot-Gassmann theories and assuming the formation velocity ratio (shear to compressional velocity) of an unconsolidated sediment is related to the velocity ratio of the matrix material of the formation and its porosity. Using the Biot coefficient calculated from either the weighted equation or from the effective medium theory, the proposed method accurately predicts the elastic properties of unconsolidated sediments with or without gas hydrate concentration. This method was applied to the observed velocities at the Mallik 2L-39 well, Mackenzie Delta, Canada.

  13. Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities

    USGS Publications Warehouse

    Lee, Myung W.

    2008-01-01

    Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.

  14. Verification of capillary functions and relative permeability equations for gas production from hydrate bearing sediments

    NASA Astrophysics Data System (ADS)

    Mahabadi Mahabad, N.; Jang, J.

    2013-12-01

    There are several studies of numerical simulation on predicting long-term behavior of hydrate-bearing sediments during gas production. Numerical simulators explore coupled processes that require numerous equations and parameters. Important equations for the estimation of gas production from hydrate-bearing sediments are soil-water characteristic curves and relative permeability equations. These equations require empirical parameters, laboratory and in-situ experiments which are very difficult and expensive. In this research, pore-network model simulation is performed to obtain the fitting parameters for capillary pressure functions and relative permeability equations. First, several sediment packings similar to in-situ sediment are generated by discrete element method. Then, the pore-network model is extracted from the pore space of sediment packing as a system of pores connected at throats. Numerical algorithm to simulate gas hydrate dissociation and gas expansion, and calculate gas and water relative permeability at every saturation is developed for the pore-network model. The assessment of water pore connectivity and the identification of gas clusters are performed using Hoshen-Kopelman algorithm. Finally, reliable fitting parameters for capillary pressure functions and relative permeability equations during gas production will be suggested for further use.

  15. Experimental verification of a prediction model for hydrate-bearing sand

    NASA Astrophysics Data System (ADS)

    Pinkert, S.; Grozic, J. L. H.

    2016-06-01

    This paper presents an experimental verification of a prediction model for the mechanical properties of hydrate-bearing sand. The model is examined using experimental drained triaxial test results of three independent data sets, which are associated with different hydrate formations and testing conditions. For each data set, an optimization process is applied based on numerical modeling of the testing conditions in order to evaluate the pure sand properties. Based on these properties, the model forecasts the stress-stain curves for different hydrate saturations, based on an advanced hydrate simulator. Although the model does not show a fair forecast with "ice-seeding" hydrate formation samples and for specimens tested under gas saturation, it predicts the mechanical behavior of samples with "partly saturated" hydrate formation tested under water saturation.

  16. Development of Sand Production Evaluation Apparatus for Methane Hydrate Development

    NASA Astrophysics Data System (ADS)

    Kakumoto, M.; Yoneda, J.; Tenma, N.; Katagiri, J.; Noda, S.

    2015-12-01

    As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on sand production mechanism during methane gas production. In 2013, the first methane hydrate offshore production test was conducted in Japan, and it was recognized in the production of about 20000m3/day of methane gas from methane hydrate bearing sand sediment in deep marine sediment. In methane hydrate development, depressurization method has been proposed for gas extraction. This method is a method to reduce the bottom hole pressure by submersible pump lowering water level in the production well, and gas and water is recovered by methane hydrate dissociation at the in situ. At that time, a phenomenon that sand flows into the wells is feared. In actually, sand production phenomenon occurred after 6 days from production start in offshore production test. A mechanism of sand production has not yet been resolved in case of methane hydrate development. Therefore, we developed large scale laboratory test apparatus for the purpose of elucidation of the mechanism of sand production phenomenon. In this presentation, we introduce basic performance of this apparatus, and usefulness is made mention by representative test results.

  17. Molecular and isotopic analyses of the hydrocarbon gases within gas hydrate-bearing rock units of the Prudhoe Bay-Kuparuk River area in northern Alaska

    USGS Publications Warehouse

    Valin, Zenon C.; Collett, Timothy S.

    1992-01-01

    Gas hydrates, which are crystalline substances of water molecules that encase gas molecules, have the potential for being a significant source of natural gas. World-wide estimates for the amount of gas contained in hydrates range from 1.1 x 105 to 2.7 x 108 trillion cubic feet. Gas hydrates exist in many Arctic regions, including the North Slope of Alaska. The two primary objectives of the U.S. Geological Survey Gas Hydrate Research Project are (1) to map the distribution of in-situ gas hydrates on the North Slope of Alaska, and (2) to evaluate the geologic parameters that control the distribution of these gas hydrates. To aid in this study, British Petroleum Exploration, ARCO Alaska, Exxon Company USA, and the Continental Oil Company allowed the U.S. Geological Survey to collect geochemical samples from drilling North Slope production wells. Molecular analysis of gaseous drill cutting and free-flowing gas samples from 10 production wells drilled in the Prudhoe Bay, Kuparuk River, and Milne Point oil fields indicates that methane is the primary hydrocarbon gas in the gas hydrate-bearing stratigraphic units. Isotopic data for several of these rock units indicate that the methane within the inferred gas hydrate occurences originated from both microbial and thermogenic processes.

  18. Enhanced lifetime of methane bubble streams within the deep ocean

    NASA Astrophysics Data System (ADS)

    Rehder, Gregor; Brewer, Peter W.; Peltzer, Edward T.; Friederich, Gernot

    2002-08-01

    We have made direct comparisons of the dissolution and rise rates of methane and argon bubbles experimentally released in the ocean at depths from 440 to 830 m. The bubbles were injected from the ROV Ventana into a box open at the top and the bottom, and imaged by HDTV while in free motion. The vehicle was piloted upwards at the rise rate of the bubbles. Methane and argon show closely similar behavior at depths above the methane hydrate stability field. Below that boundary (~520 m) markedly enhanced methane bubble lifetimes are observed, and are attributed to the formation of a hydrate skin. This effect greatly increases the ease with which methane gas released at depth, either by natural or industrial events, can penetrate the shallow ocean layers.

  19. Carbonate-hosted methanotrophy represents an unrecognized methane sink in the deep sea.

    PubMed

    Marlow, Jeffrey J; Steele, Joshua A; Ziebis, Wiebke; Thurber, Andrew R; Levin, Lisa A; Orphan, Victoria J

    2014-01-01

    The atmospheric flux of methane from the oceans is largely mitigated through microbially mediated sulphate-coupled methane oxidation, resulting in the precipitation of authigenic carbonates. Deep-sea carbonates are common around active and palaeo-methane seepage, and have primarily been viewed as passive recorders of methane oxidation; their role as active and unique microbial habitats capable of continued methane consumption has not been examined. Here we show that seep-associated carbonates harbour active microbial communities, serving as dynamic methane sinks. Microbial aggregate abundance within the carbonate interior exceeds that of seep sediments, and molecular diversity surveys reveal methanotrophic communities within protolithic nodules and well-lithified carbonate pavements. Aggregations of microbial cells within the carbonate matrix actively oxidize methane as indicated by stable isotope FISH-nanoSIMS experiments and (14)CH4 radiotracer rate measurements. Carbonate-hosted methanotrophy extends the known ecological niche of these important methane consumers and represents a previously unrecognized methane sink that warrants consideration in global methane budgets. PMID:25313858

  20. Microbial methane production in deep aquifer associated with the accretionary prism in Japan.

    PubMed

    Kimura, Hiroyuki; Nashimoto, Hiroaki; Shimizu, Mikio; Hattori, Shohei; Yamada, Keita; Koba, Keisuke; Yoshida, Naohiro; Kato, Kenji

    2010-04-01

    To identify the methanogenic pathways present in a deep aquifer associated with an accretionary prism in Southwest Japan, a series of geochemical and microbiological studies of natural gas and groundwater derived from a deep aquifer were performed. Stable carbon isotopic analysis of methane in the natural gas and dissolved inorganic carbon (mainly bicarbonate) in groundwater suggested that the methane was derived from both thermogenic and biogenic processes. Archaeal 16S rRNA gene analysis revealed the dominance of H(2)-using methanogens in the groundwater. Furthermore, the high potential of methane production by H(2)-using methanogens was shown in enrichments using groundwater amended with H(2) and CO(2). Bacterial 16S rRNA gene analysis showed that fermentative bacteria inhabited the deep aquifer. Anaerobic incubations using groundwater amended with organic substrates and bromoethanesulfonate (a methanogen inhibitor) suggested a high potential of H(2) and CO(2) generation by fermentative bacteria. To confirm whether or not methane is produced by a syntrophic consortium of H(2)-producing fermentative bacteria and H(2)-using methanogens, anaerobic incubations using the groundwater amended with organic substrates were performed. Consequently, H(2) accumulation and rapid methane production were observed in these enrichments incubated at 55 and 65 degrees C. Thus, our results suggested that past and ongoing syntrophic biodegradation of organic compounds by H(2)-producing fermentative bacteria and H(2)-using methanogens, as well as a thermogenic reaction, contributes to the significant methane reserves in the deep aquifer associated with the accretionary prism in Southwest Japan.

  1. Anisotropic Velocities of Gas Hydrate-Bearing Sediments in Fractured Reservoirs

    USGS Publications Warehouse

    Lee, Myung W.

    2009-01-01

    During the Indian National Gas Hydrate Program Expedition 01 (NGHP-01), one of the richest marine gas hydrate accumulations was discovered at drill site NGHP-01-10 in the Krishna-Godavari Basin, offshore of southeast India. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Gas hydrate saturations estimated from P- and S-wave velocities, assuming that gas hydrate-bearing sediments (GHBS) are isotropic, are much higher than those estimated from the pressure cores. To reconcile this difference, an anisotropic GHBS model is developed and applied to estimate gas hydrate saturations. Gas hydrate saturations estimated from the P-wave velocities, assuming high-angle fractures, agree well with saturations estimated from the cores. An anisotropic GHBS model assuming two-component laminated media - one component is fracture filled with 100-percent gas hydrate, and the other component is the isotropic water-saturated sediment - adequately predicts anisotropic velocities at the research site.

  2. Geomechanical Behaviors of Laboratory-Formed Non-Cementing Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Seol, Y.

    2015-12-01

    Natural hydrate-bearing sediments (HBS) have been known to exist with non-cementing pore habits, i.e., pore-filling, load-bearing, or patchy type. However, few laboratory studies have been conducted to characterize geomechanical behaviors of non-cementing CH4-HBS, which are of great importance in engineering the process of drilling and gas production in natural hydrate reservoir. In this study, we conducted multi-stage drained triaxial tests on laboratory synthesized CH4-HBS samples, which were formed in sand-clay mixtures (5%wt kaolinite) to have non-cementing habits. Three different effective confining stresses, σ3' = 0.69, 1.38, and 2.76 MPa, were applied on the HBS with the hydrate saturation, Sh, in the range of 0 to ~ 40%. The result confirms that the strength and stiffness of HBS increases with effective confining stress and hydrate saturation. It is also demonstrated that when compared to the cementing HBS, the non-cementing HBS has lower strength and cohesion, owing to less inter-particle adhesion effects from non-cementing hydrate.

  3. Global inventory of methane clathrate: sensitivity to changes in the deep ocean

    NASA Astrophysics Data System (ADS)

    Buffett, Bruce; Archer, David

    2004-11-01

    We present a mechanistic model for the distribution of methane clathrate in marine sediments, and use it to predict the sensitivity of the steady-state methane inventory to changes in the deep ocean. The methane inventory is determined by binning the seafloor area according to water depth, temperature, and O 2 concentration. Organic carbon rain to the seafloor is treated as a simple function of water depth, and carbon burial for each bin is estimated using a sediment diagenesis model called Muds [Glob. Biogeochem. Cycles 16 (2002)]. The predicted concentration of organic carbon is fed into a clathrate model [J. Geophys. Res. 108 (2003)] to calculate steady-state profiles of dissolved, frozen, and gaseous methane. We estimate the amount of methane in ocean sediments by multiplying the sediment column inventories by the corresponding binned seafloor areas. Our estimate of the methane inventory is sensitive to the efficiency of methane production from organic matter and to the rate of fluid flow within the sediment column. Preferred values for these parameters are taken from previous studies of both passive and active margins, yielding a global estimate of 3×10 18 g of carbon (3000 Gton C) in clathrate and 2×10 18 g (2000 Gton C) in methane bubbles. The predicted methane inventory decreases by 85% in response to 3 °C of warming. Conversely, the methane inventory increases by a factor of 2 if the O 2 concentration of the deep ocean decreases by 40 μM or carbon rain increases by 50% (due to an increase in primary production). Changes in sea level have a small effect. We use these sensitivities to assess the past and future state of the methane clathrate reservoir.

  4. Microbial Diversity in Hydrate-bearing and -free Seafloor Surface Sediments in the Shenhu Area, South China Sea

    NASA Astrophysics Data System (ADS)

    Su, X.

    2015-12-01

    In 2007, the China's first gas hydrate drilling expedition GMGS-1 in the Shenhu area on the northern continental slope of the South China Sea was performed (Zhang et al., 2007). Six holes (namely Sites SH1B, SH2B, SH3B, SH5B, SH5C and SH7B) were drilled, and gas hydrate samples were recovered at three sites: Sites SH2B, SH3B and SH7B. In order to investigate microbial diversity and community features in correlation to gas hydrate-bearing sediments, a study on microbial diversity in the surface sediments at hydrate-bearing sites (SH3B and SH7B) and -free sites (SH1B, SH5B, SH5C) was carried out by using 16S rRNA gene phylogenetic analysis. The phylogenetic results indicated difference in microbial communities between hydrate-bearing and -free sediments. At the gas hydrate-bearing sites, bacterial communities were dominated by Deltaproteobacteria (30.5%), and archaeal communities were dominated by Miscellaneous Crenarchaeotic Group (33.8%); In contrast, Planctomycetes was the major group (43.9%) in bacterial communities, while Marine Benthic Group-D (MBG-D) (32.4%) took up the largest proportion in the archaeal communities. Moreover, the microbial communities have characteristics different from those in other hydrate-related sediments around the world, indicating that the presence of hydrates could affect the microbial distribution and community composition. In addition, the microbial community composition in the studied sediments has its own uniqueness, which may be resulted by co-effect of geochemical characteristics and presence/absence of gas hydrates.

  5. The Water Retention Curves in THF Hydrate-Bearing Sediments - Experimental Measurement and Pore Scale Simulation

    NASA Astrophysics Data System (ADS)

    Mahabadi, N.; Zheng, X.; Dai, S.; Seol, Y.; Zapata, C.; Yun, T.; Jang, J.

    2015-12-01

    The water retention curve (WRC) of hydrate-bearing sediments is critically important to understand the behaviour of hydrate dissociation for gas production. Most gas hydrates in marine environment have been formed from an aqueous phase (gas-dissolved water). However, the gas hydrate formation from an aqueous phase in a laboratory requires long period due to low gas solubility in water and is also associated with many experimental difficulties such as hydrate dissolution, difficult hydrate saturation control, and dynamic hydrate dissolution and formation. In this study, tetrahydrofuran (THF) is chosen to form THF hydrate because the formation process is faster than gas hydrate formation and hydrate saturation is easy to control. THF hydrate is formed at water-excess condition. Therefore, there is only water in the pore space after a target THF hydrate saturation is obtained. The pore habit of THF hydrate is investigated by visual observation in a transparent micromodel and X-ray computed tomography images; and the water retention curves are obtained under different THF hydrate saturation conditions. Targeted THF hydrate saturations are Sh=0, 0.2, 0.4, 0.6 and 0.8. Results shown that at a given water saturation the capillary pressure increases as THF hydrate saturation increases. And the gas entry pressure increases with increasing hydrate saturation. The WRC obtained by experiments is also compared with the results of a pore-network model simulation and Lattice Boltzmann Method. The fitting parameters of van Genuchten equation for different hydrate saturation conditions are suggested for the use as input parameters of reservoir simulators.

  6. Lab-assay for estimating methane emissions from deep-pit swine manure storages.

    PubMed

    Andersen, D S; Van Weelden, M B; Trabue, S L; Pepple, L M

    2015-08-15

    Methane emission is an important tool in the evaluation of manure management systems due to the potential impact it has on global climate change. Field procedures used for estimating methane emission rates require expensive equipment, are time consuming, and highly variable between farms. The purpose of this paper is to report a simple laboratory procedure for estimating methane emission from stored manure. The test developed was termed a methane production rate (MPR) assay as it provides a short-term biogas production measurement. The MPR assay incubation time is short (3d), requires no sample preparation in terms of inoculation or dilution of manure, is incubated at room temperature, and the manure is kept stationary. These conditions allow for high throughput of samples and were chosen to replicate the conditions within deep-pit manure storages. In brief, an unaltered aliquot of manure was incubated at room temperature for a three-days to assay the current rate of methane being generated by the manure. The results from this assay predict an average methane emission factor of 12.2 ± 8.1 kg CH4 head(-1) yr(-1) per year, or about 5.5 ± 3.7 kg CH4 per finished animal, both of which compare well to literature values of 5.5 ± 1.1 kg CH4 per finished pig for deep-pit systems (Liu et al., 2013). The average methane flux across all sites and months was estimated to be 22 ± 17 mg CH4 m(-2)-min(-1), which is within literature values for deep-pit systems ranging from 0.24 to 63 mg CH4 m(-2)-min(-1) (Park et al., 2006) and similar to the 15 mg CH4 m(-2)-min(-1) estimated by (Zahn et al., 2001).

  7. THE EFFECT OF GAS HYDRATES DISSOCIATION AND DRILLING FLUIDS INVASION UPON BOREHOLE STABILITY IN OCEANIC GAS HYDRATES-BEARING SEDIMENT

    NASA Astrophysics Data System (ADS)

    Ning, F.; Wu, N.; Jiang, G.; Zhang, L.

    2009-12-01

    Under the condition of over-pressure drilling, the solid-phase and liquid-phase in drilling fluids immediately penetrate into the oceanic gas hydrates-bearing sediment, which causes the water content surrounding the borehole to increase largely. At the same time, the hydrates surrounding borehole maybe quickly decompose into water and gas because of the rapid change of temperature and pressure. The drilling practices prove that this two factors may change the rock characteristics of wellbore, such as rock strength, pore pressure, resistivity, etc., and then affect the logging response and evaluation, wellbore stability and well safty. The invasion of filtrate can lower the angle of friction and weaken the cohesion of hydrates-bearing sediment,which is same to the effect of invading into conventional oil and gas formation on borehole mechnical properties. The difference is that temperature isn’t considered in the invasion process of conventional formations while in hydrates-bearing sediments, it is a factor that can not be ignored. Temperature changes can result in hydrates dissociating, which has a great effect on mechanical properties of borehole. With the application of numerical simulation method, we studied the changes of pore pressure and variation of water content in the gas hydrates-bearing sediment caused by drilling fluid invasion under pressure differential and gas hydrate dissociation under temperature differential and analyzed their influence on borehole stability.The result of simulation indicated that the temperature near borehole increased quickly and changed hardly any after 6 min later. About 1m away from the borehole, the temperature of formation wasn’t affected by the temperature change of borehole. At the place near borehole, as gas hydrate dissociated dramatically and drilling fluid invaded quickly, the pore pressure increased promptly. The degree of increase depends on the permeability and speed of temperature rise of formation around

  8. Methane hydrate behavior when exposed to a 23% carbon dioxide 77% nitrogen gas under conditions similar to the ConocoPhillips 2012 Ignik Sikumi Gas Hydrate Field Trial

    NASA Astrophysics Data System (ADS)

    Borglin, S. E.; Kneafsey, T. J.; Nakagawa, S.

    2013-12-01

    In-situ replacement of methane hydrate by carbon dioxide hydrate is considered to be a promising technique for producing natural gas, while simultaneously sequestering greenhouse gas in deep geological formations. For effective application of this technique in the field, kinetic models of gas exchange rates in hydrate under a variety of environmental conditions need to be established, and the impact of hydrate substitution on geophysical (seismic) properties has to be quantified in order to optimize monitoring techniques. We performed a series of laboratory tests in which we monitored changes in methane hydrate-bearing samples while a nitrogen/carbon dioxide gas mixture was flowed through. These experiments were conducted to gain insights into data obtained from a field test in which the same mixture of carbon dioxide and nitrogen was injected into a methane hydrate-bearing unit beneath the north slope of the Brooks Range in northern Alaska (ConocoPhillips 2012 Ignik Sikumi gas hydrate field trial). We have measured the kinetic gas exchange rate for a range of hydrate saturations and different test configurations, to provide an estimate for comparison to numerical model predictions. In our tests, the exchange rate decreased over time during the tests as methane was depleted from the system. Following the elution of residual gaseous methane, the exchange rate ranged from 3.8×10-7 moles methane/(mole water*s) to 5×10-8 moles methane/(mole water*s) (Note that in these rates, the moles of water refers to water originally held in the hydrate.). In addition to the gas exchange rate, we also monitored changes in permeability occurring due to the gas substitution. Further, we determined the seismic P and S wave velocities and attenuations using our Split Hopkinson Resonant Bar apparatus (e.g. Nakagawa, 2012, Rev. Sci. Instr.). In addition to providing geophysical signatures, changes in the seismic properties can also be related to changes in the mechanical strength of

  9. Biogeography and diversity of methane and sulfur-cycling ecotypes in deep subsurface sediments

    NASA Astrophysics Data System (ADS)

    Adams, M. M.; Biddle, J.; Girguis, P. R.

    2013-12-01

    The microbially mediated anaerobic oxidation of methane (AOM) is critical for regulating the flux of methane from the ocean. AOM is coupled to sulfate availability in many anoxic marine environments, which has been extensively studied at cold seeps, hydrothermal vents, and the sulfate-methane transition zone at the seafloor. The microbes known to catalyze AOM form phylogenetically distinct anaerobic methanotroph (ANME) clusters and sometimes live in concert with sulfate-reducing bacteria (SRB). Strikingly, certain ANME groups and subgroups have been shown to occupy different ecological niches in both hydrocarbon seep and hydrothermal vent sediments. However, the environmental parameters that select for certain phylogenetic variants or 'ecotypes' in a wide range of marine systems are still unknown. A marine environment that remains elusive to characterization of potential ANME and SRB ecotype diversity is methane hydrate formations in the deep subsurface. Current estimates indicate that seafloor hydrates may exceed 10,000 GtC at standard temperature and pressure conditions. However, only a handful of studies have investigated the potential for AOM in the deep subsurface associated with methane hydrates. To gain a better understanding of the distribution of methane- and sulfur- cycling ecotypes in biogeochemically distinct marine subsurface ecosystems, we generated a substantial library of 16S rRNA gene sequences for these uncultivable deep sea microorganisms using Illumina sequencing. Sediment strata were collected from the methane-hydrate associated deep subsurface of Hydrate Ridge (30 - 100 mbsf), hydrocarbon cold seeps of Monterey Bay, metalliferous sedimented hydrothermal vents of Juan de Fuca Ridge, and organic-rich hydrothermally influenced sediments of Guaymas Basin. We used the Illumina MiSeq sequencing platform to assess Archaeal and Bacterial richness in a total of 36 deep sea sediment samples followed by qPCR for quantification of ANME and SRB phylotype

  10. Adaptation to deep-sea methane seeps from Cretaceous shallow-water black shale environments?

    NASA Astrophysics Data System (ADS)

    Kiel, Steffen; Wiese, Frank; Titus, Alan

    2013-04-01

    Sulfide-enriched environments in shallow water were considered as sites where animals acquire pre-adaptations enabling them to colonize deep-sea hydrothermal vents and seeps or where they survived extinction events in their deep-sea habitats. Here we present upper Cenomanian (early Late Cretaceous) shallow-water seep communities from the Tropic Shale in the Western Interior Seaway, USA, that lived during a time of extremely warm deep-water temperatures, which supposedly facilitates adaptations to the deep sea, and time-equivalent with a period of widespread oceanic and photic zone anoxia (OAE 2) that supposedly extinguished deep-water vent and seep faunas. Contrary to the expectation, the taxa inhabiting the Tropic Shale seeps were not found at any coeval or younger deep-water seep or vent deposit. This suggests that (i) pre-adaptations for living at deep-sea vents and seeps do not evolve at shallow-water methane seeps, and probably also not in sulfide-rich shallow-water environments in general; (ii) a low temperature gradient from shallow to deep water does not facilitate onshore-offshore adaptations to deep-sea vents and seeps; and (iii) shallow-water seeps did not act as refuges for deep-sea vent and seep animals. We hypothesize that the vast majority of adaptations to successfully colonize deep-sea vents and seeps are acquired below the photic zone.

  11. Active Microbial Communities Inhabit Sulphate-Methane Interphase in Deep Bedrock Fracture Fluids in Olkiluoto, Finland

    PubMed Central

    Bomberg, Malin; Nyyssönen, Mari; Pitkänen, Petteri; Lehtinen, Anne; Itävaara, Merja

    2015-01-01

    Active microbial communities of deep crystalline bedrock fracture water were investigated from seven different boreholes in Olkiluoto (Western Finland) using bacterial and archaeal 16S rRNA, dsrB, and mcrA gene transcript targeted 454 pyrosequencing. Over a depth range of 296–798 m below ground surface the microbial communities changed according to depth, salinity gradient, and sulphate and methane concentrations. The highest bacterial diversity was observed in the sulphate-methane mixing zone (SMMZ) at 250–350 m depth, whereas archaeal diversity was highest in the lowest boundaries of the SMMZ. Sulphide-oxidizing ε-proteobacteria (Sulfurimonas sp.) dominated in the SMMZ and γ-proteobacteria (Pseudomonas spp.) below the SMMZ. The active archaeal communities consisted mostly of ANME-2D and Thermoplasmatales groups, although Methermicoccaceae, Methanobacteriaceae, and Thermoplasmatales (SAGMEG, TMG) were more common at 415–559 m depth. Typical indicator microorganisms for sulphate-methane transition zones in marine sediments, such as ANME-1 archaea, α-, β- and δ-proteobacteria, JS1, Actinomycetes, Planctomycetes, Chloroflexi, and MBGB Crenarchaeota were detected at specific depths. DsrB genes were most numerous and most actively transcribed in the SMMZ while the mcrA gene concentration was highest in the deep methane rich groundwater. Our results demonstrate that active and highly diverse but sparse and stratified microbial communities inhabit the Fennoscandian deep bedrock ecosystems. PMID:26425566

  12. Evolution of gas saturation and relative permeability during gas production from hydrate-bearing sediments: Gas invasion vs. gas nucleation

    NASA Astrophysics Data System (ADS)

    Jang, Jaewon; Santamarina, J. Carlos

    2014-01-01

    Capillarity and both gas and water permeabilities change as a function of gas saturation. Typical trends established in the discipline of unsaturated soil behavior are used when simulating gas production from hydrate-bearing sediments. However, the evolution of gas saturation and water drainage in gas invasion (i.e., classical soil behavior) and gas nucleation (i.e., gas production) is inherently different: micromodel experimental results show that gas invasion forms a continuous flow path while gas nucleation forms isolated gas clusters. Complementary simulations conducted using tube networks explore the implications of the two different desaturation processes. In spite of their distinct morphological differences in fluid displacement, numerical results show that the computed capillarity-saturation curves are very similar in gas invasion and nucleation (the gas-water interface confronts similar pore throat size distribution in both cases); the relative water permeability trends are similar (the mean free path for water flow is not affected by the topology of the gas phase); and the relative gas permeability is slightly lower in nucleation (delayed percolation of initially isolated gas-filled pores that do not contribute to gas conductivity). Models developed for unsaturated sediments can be used for reservoir simulation in the context of gas production from hydrate-bearing sediments, with minor adjustments to accommodate a lower gas invasion pressure Po and a higher gas percolation threshold.

  13. Atmospheric methane emissions along the western Svalbard margin

    NASA Astrophysics Data System (ADS)

    Pohlman, J.; Greinert, J.; Silyakova, A.; Casso, M.; Ruppel, C. D.; Mienert, J.; Lund Myhre, C.; Bunz, S.

    2014-12-01

    Documented warming of intermediate waters by ~1oC over the past 30 years along the western Svalbard margin has been suggested as a driver of climate-change induced dissociation of marine methane hydrate. However, recent evidence suggests methane release from gas hydrate has been occurring for thousands of years near the upper limit of methane hydrate stability and that seasonal changes in bottom water temperature may be more important than longer-term warming of intermediate waters. Nevertheless, this area has been and remains an active area for researching the physical and climate controls of methane release from the seafloor, yet the amount of methane reaching the atmosphere (the ultimate climate driver) in this region is largely unknown. As part of the MOCA project led by the Norwegian Institute for Air Research (NILU), water column and atmospheric marine boundary layer methane data were collected in June 2014 aboard the R/V Helmer Hanssenduring a collaboration among CAGE at University of Tromsӧ, NILU, GEOMAR, and the USGS. The results provide a continuous record of surface methane concentration and carbon isotope data from continental slope sites near temperature-sensitive hydrate-bearing seeps along the shelf-break and upper slope, the deep-water pockmarked gas-venting Vestnesa Ridge and a shallow water seep area within the Forlandet moraine complex at the shelf. Surface water methane and associated data used to calculate sea-air fluxes were obtained with the cavity ring-down spectrometer-based USGS Gas Analysis System (USGS-GAS). Only the shallow seep site (~90 m water depth) had appreciable methane in surface waters. We conducted an exhaustive survey of this site, mapping the full extent of the surface methane plume. To provide three-dimensional constraints, we acquired 65 vertical dissolved methane profiles to delineate the vertical and horizontal extent of the subsurface methane plume. Using these data, we assess how effectively shallow arctic seeps

  14. The origin, source, and cycling of methane in deep crystalline rock biosphere.

    PubMed

    Kietäväinen, Riikka; Purkamo, Lotta

    2015-01-01

    The emerging interest in using stable bedrock formations for industrial purposes, e.g., nuclear waste disposal, has increased the need for understanding microbiological and geochemical processes in deep crystalline rock environments, including the carbon cycle. Considering the origin and evolution of life on Earth, these environments may also serve as windows to the past. Various geological, chemical, and biological processes can influence the deep carbon cycle. Conditions of CH4 formation, available substrates and time scales can be drastically different from surface environments. This paper reviews the origin, source, and cycling of methane in deep terrestrial crystalline bedrock with an emphasis on microbiology. In addition to potential formation pathways of CH4, microbial consumption of CH4 is also discussed. Recent studies on the origin of CH4 in continental bedrock environments have shown that the traditional separation of biotic and abiotic CH4 by the isotopic composition can be misleading in substrate-limited environments, such as the deep crystalline bedrock. Despite of similarities between Precambrian continental sites in Fennoscandia, South Africa and North America, where deep methane cycling has been studied, common physicochemical properties which could explain the variation in the amount of CH4 and presence or absence of CH4 cycling microbes were not found. However, based on their preferred carbon metabolism, methanogenic microbes appeared to have similar spatial distribution among the different sites. PMID:26236303

  15. The origin, source, and cycling of methane in deep crystalline rock biosphere

    PubMed Central

    Kietäväinen, Riikka; Purkamo, Lotta

    2015-01-01

    The emerging interest in using stable bedrock formations for industrial purposes, e.g., nuclear waste disposal, has increased the need for understanding microbiological and geochemical processes in deep crystalline rock environments, including the carbon cycle. Considering the origin and evolution of life on Earth, these environments may also serve as windows to the past. Various geological, chemical, and biological processes can influence the deep carbon cycle. Conditions of CH4 formation, available substrates and time scales can be drastically different from surface environments. This paper reviews the origin, source, and cycling of methane in deep terrestrial crystalline bedrock with an emphasis on microbiology. In addition to potential formation pathways of CH4, microbial consumption of CH4 is also discussed. Recent studies on the origin of CH4 in continental bedrock environments have shown that the traditional separation of biotic and abiotic CH4 by the isotopic composition can be misleading in substrate-limited environments, such as the deep crystalline bedrock. Despite of similarities between Precambrian continental sites in Fennoscandia, South Africa and North America, where deep methane cycling has been studied, common physicochemical properties which could explain the variation in the amount of CH4 and presence or absence of CH4 cycling microbes were not found. However, based on their preferred carbon metabolism, methanogenic microbes appeared to have similar spatial distribution among the different sites. PMID:26236303

  16. The origin, source, and cycling of methane in deep crystalline rock biosphere.

    PubMed

    Kietäväinen, Riikka; Purkamo, Lotta

    2015-01-01

    The emerging interest in using stable bedrock formations for industrial purposes, e.g., nuclear waste disposal, has increased the need for understanding microbiological and geochemical processes in deep crystalline rock environments, including the carbon cycle. Considering the origin and evolution of life on Earth, these environments may also serve as windows to the past. Various geological, chemical, and biological processes can influence the deep carbon cycle. Conditions of CH4 formation, available substrates and time scales can be drastically different from surface environments. This paper reviews the origin, source, and cycling of methane in deep terrestrial crystalline bedrock with an emphasis on microbiology. In addition to potential formation pathways of CH4, microbial consumption of CH4 is also discussed. Recent studies on the origin of CH4 in continental bedrock environments have shown that the traditional separation of biotic and abiotic CH4 by the isotopic composition can be misleading in substrate-limited environments, such as the deep crystalline bedrock. Despite of similarities between Precambrian continental sites in Fennoscandia, South Africa and North America, where deep methane cycling has been studied, common physicochemical properties which could explain the variation in the amount of CH4 and presence or absence of CH4 cycling microbes were not found. However, based on their preferred carbon metabolism, methanogenic microbes appeared to have similar spatial distribution among the different sites.

  17. Carbon and nitrogen assimilation activities of deep subseafloor microbes analyzed by NanoSIMS

    NASA Astrophysics Data System (ADS)

    Morono, Y.; Terada, T.; Inagaki, F.

    2009-12-01

    Deep subseafloor microbes play significant roles on biogeochemical cycles with extremely low metabolic activities. The subseafloor microbial community consists mainly of uncultured components; hence, their growth and metabolic characteristics remain almost completely unknown. Here, we presnet in vitro isotopic evidence that the deep subseafloor microbes actively incooporate multiple carbon and nitrogen compounds into their biomass using NanoSIMS. We incubated methane hydrate-bearing deep marine sediments with small 13C-labeled glucose, acetate, pyruvate, bicarbonate, amino-acids and methane in the presence of 15N-labeled ammonia as a nitrogen source for 2 and 6 monthes under the anaerobic condition. Using NanoSIMS, we observed the cells that incooprated 13C- or 15N-labeled substrates such as 13C-glucose, pyruvate, and 15N-ammonia up to 50% of their cellular carbon or nitrogen mass. Assimilation of 13C- and 15N-labeled amino acids as well as 13C-bicarbonates by autotrophs was also observed while 13C-methane was found to be difficult to be used for the carbon source, regardless of the presence of some additional electron acceptors for the energy respiration. These results indicate that the metabolic activities of deep subseafloor microbes can be stimulated in vitro by adding potential carbon and nitrogen sources, providing new insights into the biogeochemical functioning of the deep subseaflor microbes and its ecosystem.

  18. Marine gas hydrates in thin sand layers that soak up microbial methane

    NASA Astrophysics Data System (ADS)

    Malinverno, Alberto

    2010-04-01

    At Site U1325 (IODP Exp. 311, Cascadia margin), gas hydrates occupy 20-60% of pore space in thin sand layers (< 5 cm) surrounded by fine-grained intervals (2.5 m thick on average) that contain little or no hydrate. This is a common occurrence in gas hydrate-bearing marine sequences, and it has been related to the inhibition of hydrate formation in the small pores of fine-grained sediments. This paper applies a mass balance model to gas hydrate formation in a stack of alternating fine- and coarse-grained sediment layers. The only source of methane considered is in situ microbial conversion of a small amount of organic carbon (< 0.5% dry weight fraction). The results show that in a sequence such as that at Site U1325 the methane concentration never reaches the supersaturation needed to form gas hydrates in the fine-grained layers. Methane generated in these layers is transported by diffusion into the coarse-grained layers where it forms concentrated gas hydrate deposits. The vertical distribution and amount of gas hydrate observed at Site U1325 can be explained by in situ microbial methane generation, and a deep methane source is not necessary.

  19. A Long-Term Cultivation of an Anaerobic Methane-Oxidizing Microbial Community from Deep-Sea Methane-Seep Sediment Using a Continuous-Flow Bioreactor

    PubMed Central

    Aoki, Masataka; Ehara, Masayuki; Saito, Yumi; Yoshioka, Hideyoshi; Miyazaki, Masayuki; Saito, Yayoi; Miyashita, Ai; Kawakami, Shuji; Yamaguchi, Takashi; Ohashi, Akiyoshi; Nunoura, Takuro; Takai, Ken; Imachi, Hiroyuki

    2014-01-01

    Anaerobic oxidation of methane (AOM) in marine sediments is an important global methane sink, but the physiological characteristics of AOM-associated microorganisms remain poorly understood. Here we report the cultivation of an AOM microbial community from deep-sea methane-seep sediment using a continuous-flow bioreactor with polyurethane sponges, called the down-flow hanging sponge (DHS) bioreactor. We anaerobically incubated deep-sea methane-seep sediment collected from the Nankai Trough, Japan, for 2,013 days in the bioreactor at 10°C. Following incubation, an active AOM activity was confirmed by a tracer experiment using 13C-labeled methane. Phylogenetic analyses demonstrated that phylogenetically diverse Archaea and Bacteria grew in the bioreactor. After 2,013 days of incubation, the predominant archaeal components were anaerobic methanotroph (ANME)-2a, Deep-Sea Archaeal Group, and Marine Benthic Group-D, and Gammaproteobacteria was the dominant bacterial lineage. Fluorescence in situ hybridization analysis showed that ANME-1 and -2a, and most ANME-2c cells occurred without close physical interaction with potential bacterial partners. Our data demonstrate that the DHS bioreactor system is a useful system for cultivating fastidious methane-seep-associated sedimentary microorganisms. PMID:25141130

  20. TOUGH+Hydrate v1.0 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

    SciTech Connect

    Moridis, George; Moridis, George J.; Kowalsky, Michael B.; Pruess, Karsten

    2008-03-01

    TOUGH+HYDRATE v1.0 is a new code for the simulation of the behavior of hydrate-bearing geologic systems. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH{sub 4}-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy's law is valid. TOUGH+HYDRATE v1.0 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH{sub 4}, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is the first member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

  1. Study on small-strain behaviours of methane hydrate sandy sediments using discrete element method

    SciTech Connect

    Yu Yanxin; Cheng Yipik; Xu Xiaomin; Soga, Kenichi

    2013-06-18

    Methane hydrate bearing soil has attracted increasing interest as a potential energy resource where methane gas can be extracted from dissociating hydrate-bearing sediments. Seismic testing techniques have been applied extensively and in various ways, to detect the presence of hydrates, due to the fact that hydrates increase the stiffness of hydrate-bearing sediments. With the recognition of the limitations of laboratory and field tests, wave propagation modelling using Discrete Element Method (DEM) was conducted in this study in order to provide some particle-scale insights on the hydrate-bearing sandy sediment models with pore-filling and cementation hydrate distributions. The relationship between shear wave velocity and hydrate saturation was established by both DEM simulations and analytical solutions. Obvious differences were observed in the dependence of wave velocity on hydrate saturation for these two cases. From the shear wave velocity measurement and particle-scale analysis, it was found that the small-strain mechanical properties of hydrate-bearing sandy sediments are governed by both the hydrate distribution patterns and hydrate saturation.

  2. Reverse transcriptase directs viral evolution in a deep ocean methane seep

    NASA Astrophysics Data System (ADS)

    Paul, B. G.; Bagby, S. C.

    2013-12-01

    Deep ocean methane seeps are sites of intense microbial activity, with complex communities fueled by aerobic and anaerobic methanotrophy. Methane consumption in these communities has a substantial impact on the global carbon cycle, yet little is known about their evolutionary history or their likely evolutionary trajectories in a warming ocean. As in other marine systems, viral predation and virally mediated horizontal gene transfer are expected to be major drivers of evolutionary change in these communities; however, the host cells' resistance to cultivation has impeded direct study of the viral population. We conducted a metagenomic study of viruses in the anoxic sediments of a deep methane seep in the Santa Monica Basin in the Southern California Bight. We retrieved 1660 partial viral genomes, tentatively assigning 1232 to bacterial hosts and 428 to archaea. One abundant viral genome, likely hosted by Clostridia species present in the sediment, was found to encode a diversity-generating retroelement (DGR), a module for reverse transcriptase-mediated directed mutagenesis of a distal tail fiber protein. While DGRs have previously been described in the viruses of human pathogens, where diversification of viral tail fibers permits infection of a range of host cell types, to our knowledge this is the first description of such an element in a marine virus. By providing a mechanism for massively broadening potential host range, the presence of DGRs in these systems may have a major impact on the prevalence of virally mediated horizontal gene transfer, and even on the phylogenetic distances across which genes are moved.

  3. ANME-2D Archaea Catalyze Methane Oxidation in Deep Subsurface Sediments Independent of Nitrate Reduction

    NASA Astrophysics Data System (ADS)

    Hernsdorf, A. W.; Amano, Y.; Suzuki, Y.; Ise, K.; Thomas, B. C.; Banfield, J. F.

    2015-12-01

    Terrestrial sediments are an important global reservoir for methane. Microorganisms in the deep subsurface play a critical role in the methane cycle, yet much remains to be learned about their diversity and metabolisms. To provide more comprehensive insight into the microbiology of the methane cycle in the deep subsurface, we conducted a genome-resolved study of samples collected from the Horonobe Underground Research Laboratory (HURL), Japan. Groundwater samples were obtained from three boreholes from a depth range of between 140 m and 250 m in two consecutive years. Groundwater was filtered and metagenomic DNA extracted and sequenced, and the sequence data assembled. Based on the sequences of phylogenetically informative genes on the assembled fragments, we detected a high degree of overlap in community composition across a vertical transect within one borehole at the two sampling times. However, there was comparatively little similarity observed among communities across boreholes. Spatial and temporal abundance patterns were used in combination with tetranucleotide signatures of assembled genome fragments to bin the data and reconstruct over 200 unique draft genomes, of which 137 are considered to be of high quality (>90% complete). The deepest samples from one borehole were highly dominated by an archaeon identified as ANME-2D; this organism was also present at lower abundance in all other samples from that borehole. Also abundant in these microbial communities were novel members of the Gammaproteobacteria, Saccharibacteria (TM7) and Tenericute phyla. Notably, a ~2 Mbp draft genome for the ANME-2D archaeon was reconstructed. As expected, the genome encodes all of the genes predicted to be involved in the reverse methanogenesis pathway. In contrast with the previously reported ANME2-D genome, the HURL ANME-2D genome lacks the capacity to reduce nitrate. However, we identified many multiheme cytochromes with closest similarity to those of the known Fe

  4. Distinctive Geomorphology of Gas Venting and Near Seafloor Gas Hydrate-Bearing sites

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Caress, D. W.; Lundsten, E.; Anderson, K.; Gwiazda, R.; McGann, M. L.; Edwards, B. D.; Riedel, M.; Herguera, J.

    2012-12-01

    High-resolution multibeam bathymetry and chirp seismic-reflection profiles collected with an Autonomous Underwater Vehicle (AUV) complimented by Remotely Operated Vehicle (ROV) observations and sampling reveal the fine scale geomorphology associated with gas venting and/or near subsurface gas hydrate accumulations along the Pacific North American continental margin (Santa Monica Basin, Hydrate Ridge, Eel River, Barkley Canyon, and Bullseye Vent) and along the transform faults in the Gulf of California. At the 1 m multibeam grid resolution of the new data, distinctive features and textures that are undetectable at lower resolution, show the impact of gas venting, gas hydrate development, and related phenomena on the seafloor morphology. Together a suite of geomorphic characteristics illustrates different stages in the development of seafloor gas venting systems. The more mature and/or impacted areas are associated with widespread exposures of methane-derived carbonates, which form broken and irregular seafloor pavements with karst-like voids in between the cemented blocks. These mature areas also contain elevated features >10 m high and circular seafloor craters with diameters of 3-50 m that appear to be associated with missing sections of the original seafloor. Smaller mound-like features (<10 m in diameter and 1-3 m higher than the surrounding seafloor) occur at multiple sites. Solid lenses of gas hydrate are occasionally exposed along fractures on the sides of these mounds and suggest that these are push-up features associated with gas hydrate growth within the near seafloor sediments. The youngest appearing features are associated with more-subtle (<3 m in diameter and ~0.5 m high) seafloor mounds, the crests of which are crossed with small cracks lined with white bacterial mats. ROV-collected (<1.5 m long) cores obtained from these subtle mounds encountered a hard layer at 30-60 cm sub-bottom. When this layer was penetrated, methane bubbles gushed out and

  5. Faulting of gas-hydrate-bearing marine sediments - contribution to permeability

    USGS Publications Warehouse

    Dillon, William P.; Holbrook, W.S.; Drury, Rebecca; Gettrust, Joseph; Hutchinson, Deborah; Booth, James; Taylor, Michael

    1997-01-01

    Extensive faulting is observed in sediments containing high concentrations of methane hydrate off the southeastern coast of the United States. Faults that break the sea floor show evidence of both extension and shortening; mud diapirs are also present. The zone of recent faulting apparently extends from the ocean floor down to the base of gas-hydrate stability. We infer that the faulting resulted from excess pore pressure in gas trapped beneath the gas hydrate-beating layer and/or weakening and mobilization of sediments in the region just below the gas-hydrate stability zone. In addition to the zone of surface faults, we identified two buried zones of faulting, that may have similar origins. Subsurface faulted zones appear to act as gas traps.

  6. Active Gas Venting Through Hydrate-Bearing Sediments on the Vestnesa Ridge, Offshore W-Svalbard

    NASA Astrophysics Data System (ADS)

    Buenz, S.; Vadakkepuliyambatta, S.; Polyanov, S.; Mienert, J.

    2010-12-01

    Gas hydrate systems offshore western Svalbard are far more extensive (~4000km^2) than previously assumed and include the whole Vestnesa Ridge, an elongated sediment drift north of the Molloy Transform and just east of the Molloy Ridge, one of the shortest segments of the slow spreading North-Atlantic Ridge system. The crest of the Vestnesa Ridge at water depth between 1200-1300 m is pierced with fluid-flow features. Seafloor pockmarks vary in size up to 1 km in diameter. Pockmarks are generally larger at the onset of the Vestnesa Ridge than at its western termination. A recent cruise with R/V Jan Mayen discovered methane flares in the water column above the pockmark field at the onset of the Vestnesa Ridge. Over a period of one week at least 4 pockmarks were continuously active and methane flares in the water column reached a height of approximately 800 m. The extent of the active gas venting is much stronger than discovered earlier and it is still unclear what has triggered the increase in gas expulsion from seafloor sediments. Any connection to hundreds of active gas vents further to the east at the shelf edge in water depth of 250-400 m remains speculative at this point but cannot be ruled out. High -resolution 3D seismic data acquired in 2007 and 2010 also show significant dissimilarities of the sub-seafloor expression of these fluid leakage systems. At the western end of the Vestnesa Ridge, sub-seafloor fluid flow features resemble well-described pipe structures. However, the seismic expression of the active fluid flow features is much broader, much more chaotic, dome-shaped and is not very similar to a typical chimney structure. The Vestnesa Ridge gas-hydrate and free- gas system occurs within few km of a mid-oceanic ridge and transform fault, which makes this gas hydrate system unique on Earth. The close proximity to the spreading centre and its hydrothermal circulation system affects the dynamics of the gas-hydrate and free-gas system. The high heat flow

  7. Methane hydrate formation in partially water-saturated Ottawa sand

    USGS Publications Warehouse

    Waite, W.F.; Winters, W.J.; Mason, D.H.

    2004-01-01

    Bulk properties of gas hydrate-bearing sediment strongly depend on whether hydrate forms primarily in the pore fluid, becomes a load-bearing member of the sediment matrix, or cements sediment grains. Our compressional wave speed measurements through partially water-saturated, methane hydrate-bearing Ottawa sands suggest hydrate surrounds and cements sediment grains. The three Ottawa sand packs tested in the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) contain 38(1)% porosity, initially with distilled water saturating 58, 31, and 16% of that pore space, respectively. From the volume of methane gas produced during hydrate dissociation, we calculated the hydrate concentration in the pore space to be 70, 37, and 20% respectively. Based on these hydrate concentrations and our measured compressional wave speeds, we used a rock physics model to differentiate between potential pore-space hydrate distributions. Model results suggest methane hydrate cements unconsolidated sediment when forming in systems containing an abundant gas phase.

  8. Deep Subsurface Biodegradation of Sedimentary Organic Matter in a Methane-Rich Shale Gas Reservoir

    NASA Astrophysics Data System (ADS)

    Formolo, M. J.; Petsch, S.; Salacup, J.; Waldron, P.; Martini, A.; Nusslein, K.

    2006-12-01

    Extensive, sustained subsurface microbial activity in the Antrim Shale (Late Devonian, Michigan Basin, USA) has led to the accumulation of an important unconventional natural gas resource, from which is produced ~14 million m3 of methane per day. Both geochemical and molecular evidence supports a community comprising diverse methanogens, fermentative microorganisms, and little else. The diversity of methanogens is strongly associated with a sharp gradient in formation water salinity spanning 10-4000 mM Cl-1. Analysis of hydrocarbon biomarkers within the Antrim reveal patterns of degradation that are directly associated with zones of active methanogenesis, with marked differences observed between methane- producing and non-producing sections of the formation. Maturity and source indicators show that these patterns do not result from varying degrees of thermal maturity or source inputs across the Basin, but instead demonstrate that biodegradation is confined solely to regions of the Basin exhibiting extensive methanogenesis. Calculated biodegradation indices provide evidence for nearly quantitative loss of saturated hydrocarbons, specifically n-alkanes and acyclic isoprenoids, during biodegradation associated with methanogenesis. These results are the first to document deep subsurface ancient sedimentary organic matter biodegradation associated with the formation of economic microbial gas reserves within low permeability, thermally-immature source rocks. As such, the results provide insight into microbial activity in the deep subsurface, specifically the role that methanogen-dominated communities may play in carbon-rich, electron acceptor-poor sedimentary basins.

  9. Did shifting seawater sulfate concentrations drive the evolution of deep-sea methane-seep ecosystems?

    PubMed

    Kiel, Steffen

    2015-04-01

    The origin and evolution of the faunas inhabiting deep-sea hydrothermal vents and methane seeps have been debated for decades. These faunas rely on a local source of sulfide and other reduced chemicals for nutrition, which spawned the hypothesis that their evolutionary history is independent from that of photosynthesis-based food chains and instead driven by extinction events caused by deep-sea anoxia. Here I use the fossil record of seep molluscs to show that trends in body size, relative abundance and epifaunal/infaunal ratios track current estimates of seawater sulfate concentrations through the last 150 Myr. Furthermore, the two main faunal turnovers during this time interval coincide with major changes in seawater sulfate concentrations. Because sulfide at seeps originates mostly from seawater sulfate, variations in sulfate concentrations should directly affect the base of the food chain of this ecosystem and are thus the likely driver of the observed macroecologic and evolutionary patterns. The results imply that the methane-seep fauna evolved largely independently from developments and mass extinctions affecting the photosynthesis-based biosphere and add to the growing body of evidence that the chemical evolution of the oceans had a major impact on the evolution of marine life. PMID:25716797

  10. Did shifting seawater sulfate concentrations drive the evolution of deep-sea methane-seep ecosystems?

    PubMed

    Kiel, Steffen

    2015-04-01

    The origin and evolution of the faunas inhabiting deep-sea hydrothermal vents and methane seeps have been debated for decades. These faunas rely on a local source of sulfide and other reduced chemicals for nutrition, which spawned the hypothesis that their evolutionary history is independent from that of photosynthesis-based food chains and instead driven by extinction events caused by deep-sea anoxia. Here I use the fossil record of seep molluscs to show that trends in body size, relative abundance and epifaunal/infaunal ratios track current estimates of seawater sulfate concentrations through the last 150 Myr. Furthermore, the two main faunal turnovers during this time interval coincide with major changes in seawater sulfate concentrations. Because sulfide at seeps originates mostly from seawater sulfate, variations in sulfate concentrations should directly affect the base of the food chain of this ecosystem and are thus the likely driver of the observed macroecologic and evolutionary patterns. The results imply that the methane-seep fauna evolved largely independently from developments and mass extinctions affecting the photosynthesis-based biosphere and add to the growing body of evidence that the chemical evolution of the oceans had a major impact on the evolution of marine life.

  11. Did shifting seawater sulfate concentrations drive the evolution of deep-sea methane-seep ecosystems?

    PubMed Central

    Kiel, Steffen

    2015-01-01

    The origin and evolution of the faunas inhabiting deep-sea hydrothermal vents and methane seeps have been debated for decades. These faunas rely on a local source of sulfide and other reduced chemicals for nutrition, which spawned the hypothesis that their evolutionary history is independent from that of photosynthesis-based food chains and instead driven by extinction events caused by deep-sea anoxia. Here I use the fossil record of seep molluscs to show that trends in body size, relative abundance and epifaunal/infaunal ratios track current estimates of seawater sulfate concentrations through the last 150 Myr. Furthermore, the two main faunal turnovers during this time interval coincide with major changes in seawater sulfate concentrations. Because sulfide at seeps originates mostly from seawater sulfate, variations in sulfate concentrations should directly affect the base of the food chain of this ecosystem and are thus the likely driver of the observed macroecologic and evolutionary patterns. The results imply that the methane-seep fauna evolved largely independently from developments and mass extinctions affecting the photosynthesis-based biosphere and add to the growing body of evidence that the chemical evolution of the oceans had a major impact on the evolution of marine life. PMID:25716797

  12. Microbial Communities of Deep-Sea Methane Seeps at Hikurangi Continental Margin (New Zealand)

    PubMed Central

    Ruff, S. Emil; Arnds, Julia; Knittel, Katrin; Amann, Rudolf; Wegener, Gunter; Ramette, Alban; Boetius, Antje

    2013-01-01

    The methane-emitting cold seeps of Hikurangi margin (New Zealand) are among the few deep-sea chemosynthetic ecosystems of the Southern Hemisphere known to date. Here we compared the biogeochemistry and microbial communities of a variety of Hikurangi cold seep ecosystems. These included highly reduced seep habitats dominated by bacterial mats, partially oxidized habitats populated by heterotrophic ampharetid polychaetes and deeply oxidized habitats dominated by chemosynthetic frenulate tubeworms. The ampharetid habitats were characterized by a thick oxic sediment layer that hosted a diverse and biomass-rich community of aerobic methanotrophic Gammaproteobacteria. These bacteria consumed up to 25% of the emanating methane and clustered within three deep-branching groups named Marine Methylotrophic Group (MMG) 1-3. MMG1 and MMG2 methylotrophs belong to the order Methylococcales, whereas MMG3 methylotrophs are related to the Methylophaga. Organisms of the groups MMG1 and MMG3 are close relatives of chemosynthetic endosymbionts of marine invertebrates. The anoxic sediment layers of all investigated seeps were dominated by anaerobic methanotrophic archaea (ANME) of the ANME-2 clade and sulfate-reducing Deltaproteobacteria. Microbial community analysis using Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that the different seep habitats hosted distinct microbial communities, which were strongly influenced by the seep-associated fauna and the geographic location. Despite outstanding features of Hikurangi seep communities, the organisms responsible for key ecosystem functions were similar to those found at seeps worldwide. This suggests that similar types of biogeochemical settings select for similar community composition regardless of geographic distance. Because ampharetid polychaetes are widespread at cold seeps the role of aerobic methanotrophy may have been underestimated in seafloor methane budgets. PMID:24098632

  13. Microbial communities of deep-sea methane seeps at Hikurangi continental margin (New Zealand).

    PubMed

    Ruff, S Emil; Arnds, Julia; Knittel, Katrin; Amann, Rudolf; Wegener, Gunter; Ramette, Alban; Boetius, Antje

    2013-01-01

    The methane-emitting cold seeps of Hikurangi margin (New Zealand) are among the few deep-sea chemosynthetic ecosystems of the Southern Hemisphere known to date. Here we compared the biogeochemistry and microbial communities of a variety of Hikurangi cold seep ecosystems. These included highly reduced seep habitats dominated by bacterial mats, partially oxidized habitats populated by heterotrophic ampharetid polychaetes and deeply oxidized habitats dominated by chemosynthetic frenulate tubeworms. The ampharetid habitats were characterized by a thick oxic sediment layer that hosted a diverse and biomass-rich community of aerobic methanotrophic Gammaproteobacteria. These bacteria consumed up to 25% of the emanating methane and clustered within three deep-branching groups named Marine Methylotrophic Group (MMG) 1-3. MMG1 and MMG2 methylotrophs belong to the order Methylococcales, whereas MMG3 methylotrophs are related to the Methylophaga. Organisms of the groups MMG1 and MMG3 are close relatives of chemosynthetic endosymbionts of marine invertebrates. The anoxic sediment layers of all investigated seeps were dominated by anaerobic methanotrophic archaea (ANME) of the ANME-2 clade and sulfate-reducing Deltaproteobacteria. Microbial community analysis using Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that the different seep habitats hosted distinct microbial communities, which were strongly influenced by the seep-associated fauna and the geographic location. Despite outstanding features of Hikurangi seep communities, the organisms responsible for key ecosystem functions were similar to those found at seeps worldwide. This suggests that similar types of biogeochemical settings select for similar community composition regardless of geographic distance. Because ampharetid polychaetes are widespread at cold seeps the role of aerobic methanotrophy may have been underestimated in seafloor methane budgets.

  14. Microbial communities of deep-sea methane seeps at Hikurangi continental margin (New Zealand).

    PubMed

    Ruff, S Emil; Arnds, Julia; Knittel, Katrin; Amann, Rudolf; Wegener, Gunter; Ramette, Alban; Boetius, Antje

    2013-01-01

    The methane-emitting cold seeps of Hikurangi margin (New Zealand) are among the few deep-sea chemosynthetic ecosystems of the Southern Hemisphere known to date. Here we compared the biogeochemistry and microbial communities of a variety of Hikurangi cold seep ecosystems. These included highly reduced seep habitats dominated by bacterial mats, partially oxidized habitats populated by heterotrophic ampharetid polychaetes and deeply oxidized habitats dominated by chemosynthetic frenulate tubeworms. The ampharetid habitats were characterized by a thick oxic sediment layer that hosted a diverse and biomass-rich community of aerobic methanotrophic Gammaproteobacteria. These bacteria consumed up to 25% of the emanating methane and clustered within three deep-branching groups named Marine Methylotrophic Group (MMG) 1-3. MMG1 and MMG2 methylotrophs belong to the order Methylococcales, whereas MMG3 methylotrophs are related to the Methylophaga. Organisms of the groups MMG1 and MMG3 are close relatives of chemosynthetic endosymbionts of marine invertebrates. The anoxic sediment layers of all investigated seeps were dominated by anaerobic methanotrophic archaea (ANME) of the ANME-2 clade and sulfate-reducing Deltaproteobacteria. Microbial community analysis using Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that the different seep habitats hosted distinct microbial communities, which were strongly influenced by the seep-associated fauna and the geographic location. Despite outstanding features of Hikurangi seep communities, the organisms responsible for key ecosystem functions were similar to those found at seeps worldwide. This suggests that similar types of biogeochemical settings select for similar community composition regardless of geographic distance. Because ampharetid polychaetes are widespread at cold seeps the role of aerobic methanotrophy may have been underestimated in seafloor methane budgets. PMID:24098632

  15. Deep-ocean field test of methane hydrate formation from a remotely operated vehicle

    USGS Publications Warehouse

    Brewer, P.G.; Orr, F.M.; Friederich, G.; Kvenvolden, K.A.; Orange, D.L.; McFarlane, J.; Kirkwood, W.

    1997-01-01

    We have observed the process of formation of clathrate hydrates of methane in experiments conducted on the remotely operated vehicle (ROY) Ventana in the deep waters of Monterey Bay. A tank of methane gas, acrylic tubes containing seawater, and seawater plus various types of sediment were carried down on Ventana to a depth of 910 m where methane gas was injected at the base of the acrylic tubes by bubble stream. Prior calculations had shown that the local hydrographic conditions gave an upper limit of 525 m for the P-T boundary defining methane hydrate formation or dissociation at this site, and thus our experiment took place well within the stability range for this reaction to occur. Hydrate formation in free sea-water occurred within minutes as a buoyant mass of translucent hydrate formed at the gas-water interface. In a coarse sand matrix the Filling of the pore spaces with hydrate turned the sand column into a solidified block, which gas pressure soon lifted and ruptured. In a fine-grained black mud the gas flow carved out flow channels, the walls of which became coated and then filled with hydrate in larger discrete masses. Our experiment shows that hydrate formation is rapid in natural seawater, that sediment type strongly influences the patterns of hydrate formation, and that the use of ROV technologies permits the synthesis of large amounts of hydrate material in natural systems under a variety of conditions so that fundamental research on the stability and growth of these substances is possible.

  16. Deep-ocean field test of methane hydrate formation from a remotely operated vehicle

    NASA Astrophysics Data System (ADS)

    Brewer, Peter G.; Orr, Franklin M., Jr.; Friederich, Gernot; Kvenvolden, Keith A.; Orange, Daniel L.; McFarlane, James; Kirkwood, William

    1997-05-01

    We have observed the process of formation of clathrate hydrates of methane in experiments conducted on the remotely operated vehicle (ROV) Ventana in the deep waters of Monterey Bay. A tank of methane gas, acrylic tubes containing seawater, and seawater plus various types of sediment were carried down on Ventana to a depth of 910 m where methane gas was injected at the base of the acrylic tubes by bubble stream. Prior calculations had shown that the local hydrographic conditions gave an upper limit of 525 m for the P-T boundary defining methane hydrate formation or dissociation at this site, and thus our experiment took place well within the stability range for this reaction to occur. Hydrate formation in free seawater occurred within minutes as a buoyant mass of translucent hydrate formed at the gas-water interface. In a coarse sand matrix the filling of the pore spaces with hydrate turned the sand column into a solidified block, which gas pressure soon lifted and ruptured. In a fine-grained black mud the gas flow carved out flow channels, the walls of which became coated and then filled with hydrate in larger discrete masses. Our experiment shows that hydrate formation is rapid in natural seawater, that sediment type strongly influences the patterns of hydrate formation, and that the use of ROV technologies permits the synthesis of large amounts of hydrate material in natural systems under a variety of conditions so that fundamental research on the stability and growth of these substances is possible.

  17. An Effective Method for Inversion of Elastic Impedance for Shallow Sediments and Its Application to Gas Hydrate-Bearing Sediments

    USGS Publications Warehouse

    Lee, Myung W.

    2006-01-01

    Elastic properties of gas hydrate-bearing sediments (GHBS) are important for identifying and quantifying gas hydrate as well as discriminating the effects of free gas on velocity from that due to overpressure. Elastic properties of GHBS sediments can be estimated from elastic inversion using the elastic impedance. The accuracy of elastic inversion can be increased by using the predicted S-wave velocity (Vs) in the parameter k, which is k = (Vs / Vp)2. However, when Vs is less than about 0.6 kilometer per second, the inversion is inaccurate, partly because of the difficulty in accurately predicting low S-wave velocities and partly because of the large error associated with small k values. A new formula that leads to estimates of only the high-frequency part of velocity is proposed by decomposing Vs into low- and high-frequency parts. This new inversion formula is applied to a variety of well logs, and the results demonstrate its effectiveness for all ranges of Vs as long as the deviation of Vs from the low-frequency part of Vs is small. For GHBS, the deviation of Vs from the low-frequency part of Vs can be large for moderate to high gas hydrate saturations. Therefore, the new formula is not effective for elastic inversion for GHBS unless the gas hydrate effect is incorporated into the low-frequency part of Vs. For inversion of GHBS with Vs greater than about 0.6 kilometer per second, the original formulation is preferable.

  18. A Domain Decomposition Approach for Large-Scale Simulations of Flow Processes in Hydrate-Bearing Geologic Media

    SciTech Connect

    Zhang, Keni; Moridis, G.J.; Wu, Y.-S.; Pruess, K.

    2008-07-01

    Simulation of the system behavior of hydrate-bearing geologic media involves solving fully coupled mass- and heat-balance equations. In this study, we develop a domain decomposition approach for large-scale gas hydrate simulations with coarse-granularity parallel computation. This approach partitions a simulation domain into small subdomains. The full model domain, consisting of discrete subdomains, is still simulated simultaneously by using multiple processes/processors. Each processor is dedicated to following tasks of the partitioned subdomain: updating thermophysical properties, assembling mass- and energy-balance equations, solving linear equation systems, and performing various other local computations. The linearized equation systems are solved in parallel with a parallel linear solver, using an efficient interprocess communication scheme. This new domain decomposition approach has been implemented into the TOUGH+HYDRATE code and has demonstrated excellent speedup and good scalability. In this paper, we will demonstrate applications for the new approach in simulating field-scale models for gas production from gas-hydrate deposits.

  19. Invasion of drilling mud into gas-hydrate-bearing sediments. Part II: Effects of geophysical properties of sediments

    NASA Astrophysics Data System (ADS)

    Ning, Fulong; Wu, Nengyou; Yu, Yibing; Zhang, Keni; Jiang, Guosheng; Zhang, Ling; Sun, Jiaxin; Zheng, Mingming

    2013-06-01

    This study examines the dynamic behaviour of drilling-mud invasion into gas-hydrate-bearing sediment (GHBS) and the effects of such an invasion on wellbore stability and the reliability of well logging. The effects of mud properties on mud invasion into the GHBS are detailed in Part I. Here, we discuss the effects of sediment properties on mud invasion by considering the Chinese first gas-hydrate-drilling expedition in the South China Sea and other hydrate projects. Our simulation results further show that mud-invasion coupling hydrate dissociation and reformation is the main unique characteristic observed during mud invasion in GHBS compared with conventional oil/gas sediments. The appearance of a high-saturation hydrate ring during mud-invasion process is related to not only mud density, temperature and salinity but also sediment properties. On the whole, the effective permeability and initial hydrate saturation plays a critical role in mud invasion in GHBS. The effect of initial hydrate saturation, which corresponds to effective permeability and porosity on the mud invasion in SH7 is pronounced because initial hydrate saturations vary greatly. For pore-filling GHBS without fractures, well-logging results in high-saturation hydrate intervals are more reliable and accurate than those in low-saturation hydrate intervals. The log results at the interbeds with low-saturation hydrates are easily distorted by mud invasion.

  20. About transformation of the deep-water methane bubbles into hydrate powder and hydrate foam

    NASA Astrophysics Data System (ADS)

    Egorov, A. V.; Nigmatulin, R. I.; Rozhkov, A. N.; Sagalevich, A. M.; Chernyaev, E. S.

    2012-04-01

    During the Russian Academy of Sciences "MIRI na Baikale, 2008-2010" expedition, deep-water experiments with the bubbles of methane seeping from the bottom at depths 405, 860 and 1400 meters were carried out. These depths correspond to gas hydrate stability zone. Bubbles were caught by the trap which was looked like an inverted glass. It was found that the behavior of bubbles in a trap depends on the depth. At depth of 405 meters formation of hydrates was not observed. Having got to a trap at the depth of 860 meters, bubbles became covered by solid hydrate envelope, kept the initial form, and after a time period collapsed in a number of hydrate fragments which showed all properties of a granular matter. No visible changes in the hydrate granular matter were observed in the course of lifting it to a depth of 380 meters. Shallower, the decomposition of the hydrate granular matter into methane gas was observed. In the experiments at depth of 1400 meters the caught bubbles, becoming covered by hydrate envelope formed solid hydrate foam in the trap. At lifting this foam structure was deformed slightly but simultaneously a free gas left the foam and filled the trap. The volume of free gas in the trap at lifting varied according to the Boyle-Mariotte law.

  1. Investigation of gas hydrate-bearing sandstone reservoirs at the "Mount Elbert" stratigraphic test well, Milne Point, Alaska

    SciTech Connect

    Boswell, R.M.; Hunter, R.; Collett, T.; Digert, S. Inc., Anchorage, AK); Hancock, S.; Weeks, M. Inc., Anchorage, AK); Mt. Elbert Science Team

    2008-01-01

    In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), Inc., and the U.S. Geological Survey conducted an extensive data collection effort at the "Mount Elbert #1" gas hydrates stratigraphic test well on the Alaska North Slope (ANS). The 22-day field program acquired significant gas hydrate-bearing reservoir data, including a full suite of open-hole well logs, over 500 feet of continuous core, and open-hole formation pressure response tests. Hole conditions, and therefore log data quality, were excellent due largely to the use of chilled oil-based drilling fluids. The logging program confirmed the existence of approximately 30 m of gashydrate saturated, fine-grained sand reservoir. Gas hydrate saturations were observed to range from 60% to 75% largely as a function of reservoir quality. Continuous wire-line coring operations (the first conducted on the ANS) achieved 85% recovery through 153 meters of section, providing more than 250 subsamples for analysis. The "Mount Elbert" data collection program culminated with open-hole tests of reservoir flow and pressure responses, as well as gas and water sample collection, using Schlumberger's Modular Formation Dynamics Tester (MDT) wireline tool. Four such tests, ranging from six to twelve hours duration, were conducted. This field program demonstrated the ability to safely and efficiently conduct a research-level openhole data acquisition program in shallow, sub-permafrost sediments. The program also demonstrated the soundness of the program's pre-drill gas hydrate characterization methods and increased confidence in gas hydrate resource assessment methodologies for the ANS.

  2. Application of the Split Hopkinson Resonant Bar Test for Seismic Property Characterization of Hydrate-bearing Sand Undergoing Water Saturation

    SciTech Connect

    Nakagawa, S.; Kneafsey, T.J.

    2011-05-03

    Conventional resonant bar tests allow the measurement of seismic properties of rocks and sediments at low frequencies (several kilohertz). However, the tests require a long, slender sample which is often difficult to obtain from the deep subsurface and weak and fractured formations. We present an alternative low-frequency measurement technique to the conventional resonant bar tests. This technique involves a jacketed core sample placed between a pair of long, metal extension rods with attached seismic source and receiver—the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the added length and mass to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The proposed “Split Hopkinson Resonant Bar (SHRB)” test is applied in two steps. In the first step, extension and torsion-mode resonance frequencies and attenuation of the system are measured. Then, numerical inversions for the compressional and shear wave velocities and attenuation are performed. We initially applied the SHRB test to synthetic materials (plastics) for testing its accuracy, then used it for measuring the seismic velocities and attenuation of a rock core containing supercritical CO{sub 2}, and a sediment core while methane hydrate formed in the pore space.

  3. Eocene deep-sea communities in localized limestones formed by subduction-related methane seeps, southwestern Washington

    SciTech Connect

    Goedert, J.L. ); Squires, R.L. )

    1990-12-01

    Densely populated communities of soft-bottom-dwelling taxa similar to those found today along subduction zones off the coasts of Japan and Oregon have been discovered in very localized deep-water limestones of late middle to late Eocene age along the southwestern margin of Washington. Subduction was prevalent in this area during this time, and compressive forces squeezed subsurface methane-rich waters onto the ocean floor, where opportunistic bivalves (especially Modiolus, Calyptogena, and Thyasira), vestimentiferan tube worms, serpulid tube worms, siliceous sponges, very small limpets, trochid and turbinid archaeogastropods, and other macrobenthos colonized. These assemblages are the earliest recorded biologic communities formed in response to methane seeps in subduction zones.

  4. Volume and accessibility of entrained (solution) methane in deep geopressured reservoirs - tertiary formations of the Texas Gulf Coast. Final report

    SciTech Connect

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

    1980-10-01

    The objective of this project was to appraise the total volume of in-place methane dissolved in formation waters of deep sandstone reservoirs of the onshore Texas Gulf Coast within the stratigraphic section extending from the base of significant hydrocarbon production (8000 ft)* to the deepest significant sandstone occurrence. The area of investigation is about 50,000 mi/sup 2/. Factors that determine the total methane resource are reservoir bulk volume, porosity, and methane solubility; the latter is controlled by the temperature, pressure, and salinity of formation waters. Regional assessment of the volume and the distribution of potential sandstone reservoirs was made from a data base of 880 electrical well logs, from which a grid of 24 dip cross sections and 4 strike cross sections was constructed. Solution methane content in each of nine formations or divisions of formations was determined for each subdivision. The distribution of solution methane in the Gulf Coast was described on the basis of five reservoir models. Each model was characterized by depositional environment, reservoir continuity, porosity, permeability, and methane solubility.

  5. Identification, visualization, and sorting of translationally active microbial consortia from deep-sea methane seeps

    NASA Astrophysics Data System (ADS)

    Hatzenpichler, R.; Connon, S. A.; Goudeau, D.; Malmstrom, R.; Woyke, T.; Orphan, V. J.

    2015-12-01

    Within the past few years, great progress has been made in tapping the genomes of individual cells separated from environmental samples. Unfortunately, however, most often these efforts have been target blind, as they did not pre-select for taxa of interest or focus on metabolically active cells that could be considered key species of the system at the time. This problem is particularly pronounced in low-turnover systems such as deep sea sediments. In an effort to tap the genetic potential hidden within functionally active cells, we have recently developed an approach for the in situ fluorescent tracking of protein synthesis in uncultured cells via bioorthogonal non-canonical amino acid-tagging (BONCAT). This technique depends on the incorporation of synthetic amino acids that carry chemically modifiable tags into newly made proteins, which later can be visualized via click chemistry-mediated fluorescence-labeling. BONCAT is thus able to specifically target proteins that have been expressed in reaction to an experimental condition. We are particularly interested in using BONCAT to understand the functional potential of slow-growing syntrophic consortia of anaerobic methanotrophic archaea and sulfate-reducing bacteria which together catalyze the anaerobic oxidation of methane (AOM) in marine methane seeps. In order to specifically target consortia that are active under varying environmental regimes, we are studying different subpopulations of these inter-domain consortia via a combination of BONCAT with rRNA-targeted FISH. We then couple the BONCAT-enabled staining of active consortia with their separation from inactive members of the community via fluorescence-activated cell-sorting (FACS) and metagenomic sequencing of individual consortia. Using this approach, we were able to identify previously unrecognized AOM-partnerships. By comparing the mini-metagenomes obtained from individual consortia with each other we are starting to gain a more hollistic understanding

  6. Mineralization of vestimentiferan tubes at methane seeps on the Congo deep-sea fan

    NASA Astrophysics Data System (ADS)

    Haas, Antonie; Little, Crispin T. S.; Sahling, Heiko; Bohrmann, Gerhard; Himmler, Tobias; Peckmann, Jörn

    2009-02-01

    Vestimentiferan tube worms are prominent members of modern methane seep communities and are totally reliant as adults on symbiotic sulphide-oxidizing bacteria for their nutrition. The sulphide is produced in the sediment by a biochemical reaction called the anaerobic oxidation of methane (AOM). A well-studied species from the Gulf of Mexico shows that seep vestimentiferans 'mine' sulphide from the sediment using root-like, thin walled, permeable posterior tube extensions, which can also be used to pump sulphate and possibly hydrogen ions from the soft tissue back into the sediment to increase the local rate of AOM. The 'root-balls' of exhumed seep vestimentiferans are intimately associated with carbonate nodules, which are a result of AOM. We have studied vestimentiferan specimens and associated carbonates from seeps at the Kouilou pockmark field on the Congo deep-sea fan and find that some of the posterior 'root' tubes of living specimens are enclosed with carbonate indurated sediment and other, empty examples are partially or completely replaced by the carbonate mineral aragonite. This replacement occurs from the outside of the tube wall inwards and leaves fine-scale relict textures of the original organic tube wall. The process of mineralization is unknown, but is likely a result of post-mortem microbial decay of the tube wall proteins by microorganisms or the precipitation from locally high flux of AOM derived carbonate ions. The aragonite-replaced tubes from the Kouilou pockmarks show similar features to carbonate tubes in ancient seep deposits and make it more likely that many of these fossil tubes are those of vestimentiferans. These observations have implications for the supposed origination of this group, based on molecular divergence estimates.

  7. Archaea mediate anaerobic oxidation of methane in deep euxinic waters of the Black Sea

    NASA Astrophysics Data System (ADS)

    Wakeham, Stuart G.; Lewis, Cynthia M.; Hopmans, Ellen C.; Schouten, Stefan; Sinninghe Damsté, Jaap S.

    2003-04-01

    We evaluate anaerobic oxidation of methane (AOM) in the Black Sea water column by determining distributions of archaea-specific glyceryl dialkyl glyceryl tetraethers (GDGTs) and 13C isotopic compositions of their constituent biphytanes in suspended particulate matter (SPM), sinking particulate matter collected in sediment traps, and surface sediments. We also determined isotopic compositions of fatty acids specific to sulfate-reducing bacteria to test for biomarker and isotopic evidence of a syntrophic relationship between archaea and sulfate-reducing bacteria in carrying out AOM. Bicyclic and tricyclic GDGTs and their constituent 13C-depleted monocyclic and bicyclic biphytanes (down to -67‰) indicative of archaea involved in AOM were present in SPM in the anoxic zone below 700 m depth. In contrast, GDGT-0 and crenarchaeol derived from planktonic crenarchaeota dominated the GDGT distributions in the oxic surface and shallow anoxic waters. Fatty acids indicative of sulfate-reducing bacteria (i.e., iso- and anteiso-C 15) were not strongly isotopically depleted (e.g., -32 to -25‰), although anteiso-C 15 was 5‰ more depleted in 13C than iso-C 15. Our results suggest that either AOM is carried out by archaea independent of sulfate-reducing bacteria or those sulfate-reducing bacteria involved in a syntrophy with methane-oxidizing archaea constitute a small enough fraction of the total sulfate-reducing bacterial community that an isotope depletion in their fatty acids is not readily detected. Sinking particulate material collected in sediment traps and the underlying sediments in the anoxic zone contained the biomarker and isotope signature of upper-water column archaea. AOM-specific GDGTs and 13C-depleted biphytanes characteristic of the SPM in the deep anoxic zone are not incorporated into sinking particles and are not efficiently transported to the sediments. This observation suggests that sediments may not always record AOM in overlying euxinic water columns and

  8. Estimates of in situ gas hydrate concentration from resistivity monitoring of gas hydrate bearing sediments during temperature equilibration

    USGS Publications Warehouse

    Riedel, M.; Long, P.E.; Collett, T.S.

    2006-01-01

    As part of Ocean Drilling Program Leg 204 at southern Hydrate Ridge off Oregon we have monitored changes in sediment electrical resistivity during controlled gas hydrate dissociation experiments. Two cores were used, each filled with gas hydrate bearing sediments (predominantly mud/silty mud). One core was from Site 1249 (1249F-9H3), 42.1 m below seafloor (mbsf) and the other from Site 1248 (1248C-4X1), 28.8 mbsf. At Site 1247, a third experiment was conducted on a core without gas hydrate (1247B-2H1, 3.6 mbsf). First, the cores were imaged using an infra-red (IR) camera upon recovery to map the gas hydrate occurrence through dissociation cooling. Over a period of several hours, successive runs on the multi-sensor track (includes sensors for P-wave velocity, resistivity, magnetic susceptibility and gamma-ray density) were carried out complemented by X-ray imaging on core 1249F-9H3. After complete equilibration to room temperature (17-18??C) and complete gas hydrate dissociation, the final measurement of electrical resistivity was used to calculate pore-water resistivity and salinities. The calculated pore-water freshening after dissociation is equivalent to a gas hydrate concentration in situ of 35-70% along core 1249F-9H3 and 20-35% for core 1248C-4X1 assuming seawater salinity of in situ pore fluid. Detailed analysis of the IR scan, X-ray images and split-core photographs showed the hydrate mainly occurred disseminated throughout the core. Additionally, in core 1249F-9H3, a single hydrate filled vein, approximately 10 cm long and dipping at about 65??, was identified. Analyses of the logging-while-drilling (LWD) resistivity data revealed a structural dip of 40-80?? in the interval between 40 and 44 mbsf. We further analyzed all resistivity data measured on the recovered core during Leg 204. Generally poor data quality due to gas cracks allowed analyses to be carried out only at selected intervals at Sites 1244, 1245, 1246, 1247, 1248, 1249, and 1252. With a few

  9. High-resolution well-log derived dielectric properties of gas-hydrate-bearing sediments, Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Sun, Y.; Goldberg, D.; Collett, T.; Hunter, R.

    2011-01-01

    A dielectric logging tool, electromagnetic propagation tool (EPT), was deployed in 2007 in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well), North Slope, Alaska. The measured dielectric properties in the Mount Elbert well, combined with density log measurements, result in a vertical high-resolution (cm-scale) estimate of gas hydrate saturation. Two hydrate-bearing sand reservoirs about 20 m thick were identified using the EPT log and exhibited gas-hydrate saturation estimates ranging from 45% to 85%. In hydrate-bearing zones where variation of hole size and oil-based mud invasion are minimal, EPT-based gas hydrate saturation estimates on average agree well with lower vertical resolution estimates from the nuclear magnetic resonance logs; however, saturation and porosity estimates based on EPT logs are not reliable in intervals with substantial variations in borehole diameter and oil-based invasion.EPT log interpretation reveals many thin-bedded layers at various depths, both above and below the thick continuous hydrate occurrences, which range from 30-cm to about 1-m thick. Such thin layers are not indicated in other well logs, or from the visual observation of core, with the exception of the image log recorded by the oil-base microimager. We also observe that EPT dielectric measurements can be used to accurately detect fine-scale changes in lithology and pore fluid properties of hydrate-bearing sediments where variation of hole size is minimal. EPT measurements may thus provide high-resolution in-situ hydrate saturation estimates for comparison and calibration with laboratory analysis. ?? 2010 Elsevier Ltd.

  10. Seismic evidence of methane cycling between deep and shallow fluid flow systems along the Hikurangi margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Plaza-Faverola, A.; Pecher, I.; Klaeschen, D.; Henrys, S.

    2012-04-01

    Determining the source of the main natural gas, methane, forming gas hydrates, i.e. whether it is microbial or thermogenic, remains one of the main challenges in gas hydrate research. Geochemical data suggest that most of the methane that seep out from the seafloor above gas hydrate zones is microbial. However, significant volumes of free gas trapped beneath the base of the gas hydrate stability zone and the presence of faults and gas chimneys that link deep sited thermogenic gas reservoirs with the hydrate zones are evidence of fluid exchange between deep and shallow systems. We have reprocessed 10 and 12 km long surface streamer multi-channel seismic data from the Opouawe Bank and Porangahau Ridge regions along the Hikurangi Margin in order to obtain realistic geometries of fluid escape features associated with the subduction interface. Pre-stack depth migrated images of the subsurface show thrust faults linking the subduction interface with the gas hydrate zone. Anticlinal features with deeply rooted gas chimneys at their flanks and polygonal faults above the subduction interface are also evidence of fluid expulsion from the subdcuted sediments towards the gas hydrate zone. Further, anomalous low velocity zones in P-wave velocity macro models indicate preferred locations for fluid accumulations in sediments between the gas hydrate zone and the subduction interface. In order to explain the dominant microbial signature of methane sampled at the surface in spite of evident migration of fluids from well beneath the microbial zone, we present a model where microbial methane has been expelled from buried sediments together with thermogenic methane at different periods of overpressure related to the subduction system. We expect signatures for thermogenic methane to be found deeper than maximum depths of conventional coring (i.e. > 30 mbsf) in the sedimentary column. Our results complement an ongoing multidisciplinary investigation of gas hydrate systems along Hikurangi

  11. Larvae from deep-sea methane seeps disperse in surface waters

    PubMed Central

    Arellano, Shawn M.; Van Gaest, Ahna L.; Johnson, Shannon B.; Vrijenhoek, Robert C.; Young, Craig M.

    2014-01-01

    Many species endemic to deep-sea methane seeps have broad geographical distributions, suggesting that they produce larvae with at least episodic long-distance dispersal. Cold-seep communities on both sides of the Atlantic share species or species complexes, yet larval dispersal across the Atlantic is expected to take prohibitively long at adult depths. Here, we provide direct evidence that the long-lived larvae of two cold-seep molluscs migrate hundreds of metres above the ocean floor, allowing them to take advantage of faster surface currents that may facilitate long-distance dispersal. We collected larvae of the ubiquitous seep mussel “Bathymodiolus” childressi and an associated gastropod, Bathynerita naticoidea, using remote-control plankton nets towed in the euphotic zone of the Gulf of Mexico. The timing of collections suggested that the larvae might disperse in the water column for more than a year, where they feed and grow to more than triple their original sizes. Ontogenetic vertical migration during a long larval life suggests teleplanic dispersal, a plausible explanation for the amphi-Atlantic distribution of “B.” mauritanicus and the broad western Atlantic distribution of B. naticoidea. These are the first empirical data to demonstrate a biological mechanism that might explain the genetic similarities between eastern and western Atlantic seep fauna. PMID:24827437

  12. Methane-oxidizing Archaea Fix Nitrogen in Cooperation with Sulfate-reducing Bacteria in Deep-Sea Methane Seeps

    NASA Astrophysics Data System (ADS)

    Orphan, V. J.; Dekas, A. E.; Poretsky, R.; Amend, J.

    2010-04-01

    Using 15N2 incubation experiments of deep-sea sediments combined with FISH-nanoSIMS, we show that uncultured syntrophic consortia of ANME-2 and sulfate-reducing bacteria are capable of nitrogen fixation.

  13. Geochemical investigation of the potential for mobilizing non-methane hydrocarbons during carbon dioxide storage in deep coal beds

    USGS Publications Warehouse

    Kolak, J.J.; Burruss, R.C.

    2006-01-01

    Coal samples of different rank (lignite to anthracite) were extracted in the laboratory with supercritical CO2 (40 ??C; 10 MPa) to evaluate the potential for mobilizing non-methane hydrocarbons during CO2 storage (sequestration) or enhanced coal bed methane recovery from deep (???1-km depth) coal beds. The total measured alkane concentrations mobilized from the coal samples ranged from 3.0 to 64 g tonne-1 of dry coal. The highest alkane concentration was measured in the lignite sample extract; the lowest was measured in the anthracite sample extract. Substantial concentrations of polycyclic aromatic hydrocarbons (PAHs) were also mobilized from these samples: 3.1 - 91 g tonne-1 of dry coal. The greatest amounts of PAHs were mobilized from the high-volatile bituminous coal samples. The distributions of aliphatic and aromatic hydrocarbons mobilized from the coal samples also varied with rank. In general, these variations mimicked the chemical changes that occur with increasing degrees of coalification and thermal maturation. For example, the amount of PAHs mobilized from coal samples paralleled the general trend of bitumen formation with increasing coal rank. The coal samples yielded hydrocarbons during consecutive extractions with supercritical CO2, although the amount of hydrocarbons mobilized declined with each successive extraction. These results demonstrate that the potential for supercritical CO2 to mobilize non-methane hydrocarbons from coal beds, and the effect of coal rank on this process, are important to consider when evaluating deep coal beds for CO2 storage.

  14. Methane assimilation and trophic interactions with marine Methylomicrobium in deep-water coral reef sediment off the coast of Norway.

    PubMed

    Jensen, Sigmund; Neufeld, Josh D; Birkeland, Nils-Kåre; Hovland, Martin; Murrell, John Colin

    2008-11-01

    Deep-water coral reefs are seafloor environments with diverse biological communities surrounded by cold permanent darkness. Sources of energy and carbon for the nourishment of these reefs are presently unclear. We investigated one aspect of the food web using DNA stable-isotope probing (DNA-SIP). Sediment from beneath a Lophelia pertusa reef off the coast of Norway was incubated until assimilation of 5 micromol 13CH4 g(-1) wet weight occurred. Extracted DNA was separated into 'light' and 'heavy' fractions for analysis of labelling. Bacterial community fingerprinting of PCR-amplified 16S rRNA gene fragments revealed two predominant 13C-specific bands. Sequencing of these bands indicated that carbon from 13CH4 had been assimilated by a Methylomicrobium and an uncultivated member of the Gammaproteobacteria. Cloning and sequencing of 16S rRNA genes from the heavy DNA, in addition to genes encoding particulate methane monooxygenase and methanol dehydrogenase, all linked Methylomicrobium with methane metabolism. Putative cross-feeders were affiliated with Methylophaga (Gammaproteobacteria), Hyphomicrobium (Alphaproteobacteria) and previously unrecognized methylotrophs of the Gammaproteobacteria, Alphaproteobacteria, Deferribacteres and Bacteroidetes. This first marine methane SIP study provides evidence for the presence of methylotrophs that participate in sediment food webs associated with deep-water coral reefs. PMID:18811651

  15. Methane assimilation and trophic interactions with marine Methylomicrobium in deep-water coral reef sediment off the coast of Norway.

    PubMed

    Jensen, Sigmund; Neufeld, Josh D; Birkeland, Nils-Kåre; Hovland, Martin; Murrell, John Colin

    2008-11-01

    Deep-water coral reefs are seafloor environments with diverse biological communities surrounded by cold permanent darkness. Sources of energy and carbon for the nourishment of these reefs are presently unclear. We investigated one aspect of the food web using DNA stable-isotope probing (DNA-SIP). Sediment from beneath a Lophelia pertusa reef off the coast of Norway was incubated until assimilation of 5 micromol 13CH4 g(-1) wet weight occurred. Extracted DNA was separated into 'light' and 'heavy' fractions for analysis of labelling. Bacterial community fingerprinting of PCR-amplified 16S rRNA gene fragments revealed two predominant 13C-specific bands. Sequencing of these bands indicated that carbon from 13CH4 had been assimilated by a Methylomicrobium and an uncultivated member of the Gammaproteobacteria. Cloning and sequencing of 16S rRNA genes from the heavy DNA, in addition to genes encoding particulate methane monooxygenase and methanol dehydrogenase, all linked Methylomicrobium with methane metabolism. Putative cross-feeders were affiliated with Methylophaga (Gammaproteobacteria), Hyphomicrobium (Alphaproteobacteria) and previously unrecognized methylotrophs of the Gammaproteobacteria, Alphaproteobacteria, Deferribacteres and Bacteroidetes. This first marine methane SIP study provides evidence for the presence of methylotrophs that participate in sediment food webs associated with deep-water coral reefs.

  16. Stability and flux of methane in the deep crust - a review

    SciTech Connect

    Burruss, R.C. )

    1993-01-01

    Empirical observations and theoretical calculations demonstrate that methane is stable in the crust to temperatures of 800[degrees]C and pressures of 10 kbar or greater. These conditions are equivalent to depths of at least 35 to 40 km. Methane is most stable in metasedimentary crustal rocks that contain graphite. The concept of a [open quotes]deadline[close quotes] for methane is clearly irrelevant in graphitic metasediments. Based on the volume of fluid necessary to form quartz veins, the estimates of the possible flux of methane from depth in the crust are large, on the order of 10's to 100's of Tcf (3 to 30x10[sup 11] m[sup 3]) from single giant vein systems or from areas of focused flow in metamorphic terranes. Crustally generated methane can accumulate through phase separation and buoyant rise of a separate gas phase but may be accompanied by significant amounts of carbon dioxide and nitrogen. The estimated fluxes of methane needed for accumulation of natural gas resources are difficult to assess. Methane can be lost from crustal gases by oxidation in nongraphitic rocks at high temperatures. Methods are needed to chemically identify and ultimately quantify crustally generated methane accumulations that are accessible to drilling and production. 43 refs., 4 figs.

  17. Lab-assay for estimating methane emissions from deep-pit manure storages

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methane emission is an important element in the evaluation of manure management systems due to the potential impact it has on global climate change. Field procedures used for estimating methane emission rates require expensive equipment, are time consuming, and highly variable between farms. The pur...

  18. Heat production in depth up to 2500m via in situ combustion of methane using a counter-current heat-exchange reactor

    NASA Astrophysics Data System (ADS)

    Schicks, Judith Maria; Spangenberg, Erik; Giese, Ronny; Heeschen, Katja; Priegnitz, Mike; Luzi-Helbing, Manja; Thaler, Jan; Abendroth, Sven; Klump, Jens

    2014-05-01

    In situ combustion is a well-known method used for exploitation of unconventional oil deposits such as heavy oil/bitumen reservoirs where the required heat is produced directly within the oil reservoir by combustion of a small percentage of the oil. A new application of in situ combustion for the production of methane from hydrate-bearing sediments was tested at pilot plant scale within the first phase of the German national gas hydrate project SUGAR. The applied method of in situ combustion was a flameless, catalytic oxidation of CH4 in a counter-current heat-exchange reactor with no direct contact between the catalytic reaction zone and the reservoir. The catalyst permitted a flameless combustion of CH4 with air to CO2 and H2O below the auto-ignition temperature of CH4 in air (868 K) and outside the flammability limits. This led to a double secured application of the reactor. The relatively low reaction temperature allowed the use of cost-effective standard materials for the reactor and prevented NOx formation. Preliminary results were promising and showed that only 15% of the produced CH4 was needed to be catalytically burned to provide enough heat to dissociate the hydrates in the environment and release CH4. The location of the heat source right within the hydrate-bearing sediment is a major advantage for the gas production from natural gas hydrates as the heat is generated where it is needed without loss of energy due to transportation. As part of the second period of the SUGAR project the reactor prototype of the first project phase was developed further to a borehole tool. The dimensions of this counter-current heat-exchange reactor are about 540 cm in length and 9 cm in diameter. It is designed for applications up to depths of 2500 m. A functionality test and a pressure test of the reactor were successfully carried out in October 2013 at the continental deep drilling site (KTB) in Windischeschenbach, Germany, in 600 m depth and 2000 m depth, respectively

  19. Organic matters affecting the process of CO2 replacement of CH4 using methane hydrate under deep sea - simulate deep sea conditions

    NASA Astrophysics Data System (ADS)

    Park, T.; Lee, W.

    2012-12-01

    It is widely known that CO2 replacement of CH4 from methane hydrate is available as a method for producing energy source and storing global warming gas stably. Previous studies of replacement mechanism with gas hydrate have been proposed while considering the geochemical factors: electrolytes, soil minerals, and organic matters, independently. For more realistic simulation to be applied, it is necessary to investigate the effects of geochemical factors in deep-sea gas hydrate deposits simultaneously. In this study, CH4 recovery ratio and kinetic have been measured in sand/silt/clay sediments with the organic matters (glycine, glucose, and humic acid). The water-saturated sediments were prepared to observe the effects of organic matters for the replacement process with or without the sediments. By calculating the solvation free energy of organic matter samples, estimating the interaction intensity between water and organic matters are possible because the free energy indicates how stable the structure is. To figure out the kinetic and replacement rate of the CH4-CO2 replacement, gas chromatography (GC) was used. Replacement rate and kinetics with different organic matters in the diverse conditioned sediments showed different replacement rate and kinetics respectively. This could be applied to in-situ replacement technology to recover widely deposited methane and store the carbon dioxide to methane hydrate layer.

  20. An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

    USGS Publications Warehouse

    Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

    2006-01-01

    The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

  1. Methane rising from the Deep: Hydrates, Bubbles, Oil Spills, and Global Warming

    NASA Astrophysics Data System (ADS)

    Leifer, I.; Rehder, G. J.; Solomon, E. A.; Kastner, M.; Asper, V. L.; Joye, S. B.

    2011-12-01

    Elevated methane concentrations in near-surface waters and the atmosphere have been reported for seepage from depths of nearly 1 km at the Gulf of Mexico hydrate observatory (MC118), suggesting that for some methane sources, deepsea methane is not trapped and can contribute to atmospheric greenhouse gas budgets. Ebullition is key with important sensitivity to the formation of hydrate skins and oil coatings, high-pressure solubility, bubble size and bubble plume processes. Bubble ROV tracking studies showed survival to near thermocline depths. Studies with a numerical bubble propagation model demonstrated that consideration of structure I hydrate skins transported most methane only to mid-water column depths. Instead, consideration of structure II hydrates, which are stable to far shallower depths and appropriate for natural gas mixtures, allows bubbles to survive to far shallower depths. Moreover, model predictions of vertical methane and alkane profiles and bubble size evolution were in better agreement with observations after consideration of structure II hydrate properties as well as an improved implementation of plume properties, such as currents. These results demonstrate the importance of correctly incorporating bubble hydrate processes in efforts to predict the impact of deepsea seepage as well as to understand the fate of bubble-transported oil and methane from deepsea pipeline leaks and well blowouts. Application to the DWH spill demonstrated the importance of deepsea processes to the fate of spilled subsurface oil. Because several of these parameters vary temporally (bubble flux, currents, temperature), sensitivity studies indicate the importance of real-time monitoring data.

  2. Development of Ocean Bottom Multi-component Seismic System for Methane Hydrate Dissociation Monitoring

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Asakawa, E.; Hayashi, T.; Inamori, T.; Saeki, T.

    2011-12-01

    A 2D multi-component seismic survey was carried out in the Nankai Trough using the RSCS (Real-time Seismic Cable System) system in 2006. The RSCS is the newly developed ocean bottom cable system which is usable in more than 2000m water depth. The results of the PP and data PS components gave us much information of the methane hydrates bearing zone. Based on RSCS technology, we are developing a new monitoring system using multi-component seismic sensors to delineate the methane hydrate dissociation zone for the offshore methane hydrate production test scheduled in FY2012. Conventional RSCS is composed of three component gimbaled geophones which require a large volume inside the receiver. We will adopt accelerometers to achieve a small receiver that is 2/3 the size of conventional RSCS. The accelerometer data can be corrected into horizontal or vertical directions based on the gravity acceleration. The receiver case has a protective metallic exterior and the cable is protected with steel-screened armoring, allowing for burial usage using ROV for sub-seabed deployment. It will realize a unique survey style that leaves the system on the seabed between pre-test baseline survey and post-test repeated survey, which might be up to 6 months. The fixed location of the receiver is very important for time-lapse monitoring survey. We name the new system as DSS (Deep-sea Seismic System). A feasibility study to detect the methane hydrate dissociation with the DSS was carried out and we found that the methane hydrate dissociation could be detected with the DSS depending on the area of the dissociation. The first experiment of the DSS performance test in a marine area is planned in November 2011. The main features of DSS are described as follows: (1) Deep-sea /Ultra Deep-sea Operation Methane hydrate exists in equilibrium temperature and pressure holds at water depths greater than 500m. The system water depth resistance target up to 2000m. The receiver case has a protective

  3. Estimates of Biogenic Methane Production Rates in Deep Marine Sediments at Hydrate Ridge, Cascadia Margin

    SciTech Connect

    F. S. Colwell; S. Boyd; M. E. Delwiche; D. W. Reed; T. J. Phelps; D. T. Newby

    2008-06-01

    Methane hydrate found in marine sediments is thought to contain gigaton quantities of methane and is considered an important potential fuel source and climate-forcing agent. Much of the methane in hydrates is biogenic, so models that predict the presence and distribution of hydrates require accurate rates of in situ methanogenesis. We estimated the in situ methanogenesis rates in Hydrate Ridge (HR) sediments by coupling experimentally derived minimal rates of methanogenesis to methanogen biomass determinations for discrete locations in the sediment column. When starved in a biomass recycle reactor Methanoculleus submarinus produced ca. 0.017 fmol methane/cell/day. Quantitative polymerase chain reaction (QPCR) directed at the methyl coenzyme M reductase subunit A (mcrA) gene indicated that 75% of the HR sediments analyzed contained <1000 methanogens/g. The highest methanogen numbers were mostly from sediments <10 meters below seafloor. By combining methanogenesis rates for starved methanogens (adjusted to account for in situ temperatures) and the numbers of methanogens at selected depths we derived an upper estimate of <4.25 fmol methane produced/g sediment/day for the samples with fewer methanogens than the QPCR method could detect. The actual rates could vary depending on the real number of methanogens and various seafloor parameters that influence microbial activity. However, our calculated rate is lower than rates previously reported from such sediments and close to the rate derived using geochemical modeling of the sediments. These data will help to improve models that predict microbial gas generation in marine sediments and determine the potential influence of this source of methane on the global carbon cycle.

  4. Iron oxide reduction in deep Baltic Sea sediments: the potential role of anaerobic oxidation of methane

    NASA Astrophysics Data System (ADS)

    Egger, Matthias; Slomp, Caroline P.; Dijkstra, Nikki; Sapart, Célia J.; Risgaard-Petersen, Nils; Kasten, Sabine; Riedinger, Natascha; Barker Jørgensen, Bo

    2015-04-01

    Methane is a powerful greenhouse gas and its emission from marine sediments to the atmosphere is largely controlled by anaerobic oxidation of methane (AOM). Traditionally, sulfate is considered to be the most important electron acceptor for AOM in marine sediments. However, recent studies have shown that AOM may also be coupled to the reduction of iron (Fe) oxides (Beal et al., 2009; Riedinger et al., 2014; Egger et al., 2014). In the Baltic Sea, the transition from the Ancylus freshwater phase to the Littorina brackish/marine phase (A/L-transition) ca. 9-7 ka ago (Zillén et al., 2008) resulted in the accumulation of methanogenic brackish/marine sediments overlying Fe-oxide rich lacustrine deposits. The downward diffusion of methane from the brackish/marine sediments into the lake sediments leads to an ideal diagenetic system to study a potential coupling between Fe oxide reduction and methane oxidation. Here, we use porewater and sediment geochemical data obtained at sites M0063 and M0065 during the IODP Baltic Sea Paleoenvironment Expedition 347 in 2013 to identify the potential mechanisms responsible for the apparent Fe oxide reduction in the non-sulfidic limnic sediments below the A/L transition. In this presentation, we will review the various explanations for the elevated ferrous Fe in the porewater in the lake sediments and we will specifically address the potential role of the reaction of methane with Fe-oxides. References: Beal E. J., House C. H. and Orphan V. J. (2009) Manganese- and iron-dependent marine methane oxidation. Science 325, 184-187. Egger M., Rasigraf O., Sapart C. J., Jilbert T., Jetten M. S. M., Röckmann T., van der Veen C., Banda N., Kartal B., Ettwig K. F. and Slomp C. P. (2014) Iron-mediated anaerobic oxidation of methane in brackish coastal sediments. Environ. Sci. Technol. 49, 277-283. Riedinger N., Formolo M. J., Lyons T. W., Henkel S., Beck A. and Kasten S. (2014) An inorganic geochemical argument for coupled anaerobic oxidation of

  5. Model of Methane Hydrate Formation in Mid-ocean Ridges

    NASA Astrophysics Data System (ADS)

    Dmitrievsky, A. N.; Balanyuk, I. E.; Sorokhtin, O. G.; Matveenkov, V. V.; Dongaryan, L. Sh.

    2003-04-01

    MODEL OF METHANE HYDRATE FORMATION IN MID-OCEAN RIDGES A.N. Dmitrievsky, I.E. Balanyuk, O.G.Sorokhtin, V.V. Matveenkov, and L.Sh. Dongaryan P.P.Shirshov Institute of Oceanology Russian Academy of Sciences Moscow, Russia, balanyuk@sio.rssi.ru One among the most perspective direction in studying the ocean floor is the research of hydrothermal fields within the most active zones — rift valleys, where the processes of spreading of the ocean floor, uplift of the deep matter to the surface of the ocean floor, and creation of the new oceanic crust occur. Volcanic activity in these zones is accompanied with the formation of the hydrothermal system executing separation, transfer, and precipitation of a series of chemical elements. It is known that ore deposits with high concentration of iron, manganese, copper, nickel, cobalt are formed as a result of hydrothermal activity. It is much less known that hydrothermal activity in these zones has important but not so evident result — the formation of hydrocarbons in the form of methane hydrates. We propose the hypothesis of formation of methane hydrate deposits over the shallow slopes of the mid-oceanic ridges as an outcome of the action of two factors: the thermal convection of water in fractured-porous rocks of the crust and the reaction of serpentinization of the crust. The intensive exhalation of hydrocarbons takes place in the process of serpentinization. The conditions of water convection in the porous media are favorable for the formation and accumulation of methane hydrates in the near-surface layers of the oceanic crust. The carbonic-acid gas dissolved in the seawater is involved into the process of methane hydrate formation. It was established that the most favorable conditions for this mechanism are over the slopes of the Mid-Atlantic Ridge. All types of water areas where gas hydrates occur can be conditionally subdivided into following geodynamic zones: the abyssal basins of the inner and marginal seas, the

  6. Active Venting Sites On The Gas-Hydrate-Bearing Hikurangi Margin, Off New Zealand: ROV Measurements And Observations

    NASA Astrophysics Data System (ADS)

    Naudts, L.; Poort, J.; Boone, D.; Linke, P.; Greinert, J.; de Batist, M.; Henriet, J.

    2007-12-01

    During R.V. Sonne cruise SO191-3, part of the "New (Zealand Cold) Vents" expedition, RCMG deployed a CHEROKEE ROV "Genesis" on the Hikurangi Margin. This accretionary margin, on the east coast of New Zealand, is related to the subduction of the Pacific Plate under the Australian Plate. Several cold vent locations as well as an extensive BSR, indicating the presence of gas hydrates, have been found at this margin. The aims of the ROV-work were to precisely localize active methane vents, to conduct detailed visual observations of the vent structures and activity, and to perform measurements of physical properties and collect samples at and around the vent locations. The three investigated areas generally have a flat to moderate undulating sea floor with soft sediments alternating with carbonate platforms. The different sites were sometimes covered with dense fields of live clams or shell debris, often in association with tube worms, sponges and/or soft tissue corals. Active bubble- releasing seeps were observed at Faure's site and LM-3 site. Bubble-releasing activity was very variable in time, with periods of almost non-activity alternating with periods of violent outbursts. Bubble release occurred mainly from prominent depressions in soft-sediment sea floor. Bottom-water sampling revealed sometimes high concentrations of methane. Sediment-temperature measurements were largely comparable with the bottom- water temperature except for a "raindrop site" (with dense populations of polychaetes), where anomalous low sediment-temperature was measured. Further analysis of the ROV data together with the integration of other datasets will enable us to produce a model characterizing seep structure and environment.

  7. Relative permeability of hydrate-bearing sediments from percolation theory and critical path analysis: theoretical and experimental results

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Rice, M. A.

    2015-12-01

    Relative permeabilities to water and gas are important parameters for accurate modeling of the formation of methane hydrate deposits and production of methane from hydrate reservoirs. Experimental measurements of gas and water permeability in the presence of hydrate are difficult to obtain. The few datasets that do exist suggest that relative permeability obeys a power law relationship with water or gas saturation with exponents ranging from around 2 to greater than 10. Critical path analysis and percolation theory provide a framework for interpreting the saturation-dependence of relative permeability based on percolation thresholds and the breadth of pore size distributions, which may be determined easily from 3-D images or gas adsorption-desorption hysteresis. We show that the exponent of the permeability-saturation relationship for relative permeability to water is related to the breadth of the pore size distribution, with broader pore size distributions corresponding to larger exponents. Relative permeability to water in well-sorted sediments with narrow pore size distributions, such as Berea sandstone or Toyoura sand, follows percolation scaling with an exponent of 2. On the other hand, pore-size distributions determined from argon adsorption measurements we performed on clays from the Nankai Trough suggest that relative permeability to water in fine-grained intervals may be characterized by exponents as large as 10 as determined from critical path analysis. We also show that relative permeability to the gas phase follows percolation scaling with a quadratic dependence on gas saturation, but the threshold gas saturation for percolation changes with hydrate saturation, which is an important consideration in systems in which both hydrate and gas are present, such as during production from a hydrate reservoir. Our work shows how measurements of pore size distributions from 3-D imaging or gas adsorption may be used to determine relative permeabilities.

  8. Relative permeability of hydrate-bearing sediments from percolation theory and critical path analysis: theoretical and experimental results

    SciTech Connect

    Daigle, Hugh; Rice, Mary Anna; Daigle, Hugh

    2015-12-14

    Relative permeabilities to water and gas are important parameters for accurate modeling of the formation of methane hydrate deposits and production of methane from hydrate reservoirs. Experimental measurements of gas and water permeability in the presence of hydrate are difficult to obtain. The few datasets that do exist suggest that relative permeability obeys a power law relationship with water or gas saturation with exponents ranging from around 2 to greater than 10. Critical path analysis and percolation theory provide a framework for interpreting the saturation-dependence of relative permeability based on percolation thresholds and the breadth of pore size distributions, which may be determined easily from 3-D images or gas adsorption-desorption hysteresis. We show that the exponent of the permeability-saturation relationship for relative permeability to water is related to the breadth of the pore size distribution, with broader pore size distributions corresponding to larger exponents. Relative permeability to water in well-sorted sediments with narrow pore size distributions, such as Berea sandstone or Toyoura sand, follows percolation scaling with an exponent of 2. On the other hand, pore-size distributions determined from argon adsorption measurements we performed on clays from the Nankai Trough suggest that relative permeability to water in fine-grained intervals may be characterized by exponents as large as 10 as determined from critical path analysis. We also show that relative permeability to the gas phase follows percolation scaling with a quadratic dependence on gas saturation, but the threshold gas saturation for percolation changes with hydrate saturation, which is an important consideration in systems in which both hydrate and gas are present, such as during production from a hydrate reservoir. Our work shows how measurements of pore size distributions from 3-D imaging or gas adsorption may be used to determine relative permeabilities.

  9. Evaluation of Heat Induced Methane Release from Methane Hydrates

    NASA Astrophysics Data System (ADS)

    Leeman, J.; Elwood-Madden, M.; Phelps, T. J.; Rawn, C. J.

    2010-12-01

    Clathrates, or gas hydrates, structurally are guest gas molecules populating a cavity in a cage of water molecules. Gas hydrates naturally occur on Earth under low temperature and moderate pressure environments including continental shelf, deep ocean, and permafrost sediments. Large quantities of methane are trapped in hydrates, providing significant near-surface reserves of carbon and energy. Thermodynamics predicts that hydrate deposits may be destabilized by reducing the pressure in the system or raising the temperature. However, the rate of methane release due to varying environmental conditions remains relatively unconstrained and complicated by natural feedback effects of clathrate dissociation. In this study, hydrate dissociation in sediment due to localized increases in temperature was monitored and observed at the mesoscale (>20L) in a laboratory environment. Experiments were conducted in the Seafloor Process Simulator (SPS) at Oak Ridge National Laboratory (ORNL) to simulate heat induced dissociation. The SPS, containing a column of Ottawa sand saturated with water containing 25mg/L Sno-Max to aid nucleation, was pressurized and cooled well into the hydrate stability field. A fiber optic distributed sensing system (DSS) was embedded at four depths in the sediment column. This allowed the temperature strain value (a proxy for temperature) of the system to be measured with high spatial resolution to monitor the clathrate formation/dissociation processes. A heat exchanger embedded in the sediment was heated using hot recirculated ethylene glycol and the temperature drop across the exchanger was measured. These experiments indicate a significant and sustained amount of heat is required to release methane gas from hydrate-bearing sediments. Heat was consumed by hydrate dissociated in a growing sphere around the heat exchanger until steady state was reached. At steady state all heat energy entering the system was consumed in maintaining the temperature profile

  10. Phylogenetic and enzymatic diversity of deep subseafloor aerobic microorganisms in organics- and methane-rich sediments off Shimokita Peninsula.

    PubMed

    Kobayashi, Tohru; Koide, Osamu; Mori, Kozue; Shimamura, Shigeru; Matsuura, Takae; Miura, Takeshi; Takaki, Yoshihiro; Morono, Yuki; Nunoura, Takuro; Imachi, Hiroyuki; Inagaki, Fumio; Takai, Ken; Horikoshi, Koki

    2008-07-01

    "A meta-enzyme approach" is proposed as an ecological enzymatic method to explore the potential functions of microbial communities in extreme environments such as the deep marine subsurface. We evaluated a variety of extra-cellular enzyme activities of sediment slurries and isolates from a deep subseafloor sediment core. Using the new deep-sea drilling vessel "Chikyu", we obtained 365 m of core sediments that contained approximately 2% organic matter and considerable amounts of methane from offshore the Shimokita Peninsula in Japan at a water depth of 1,180 m. In the extra-sediment fraction of the slurry samples, phosphatase, esterase, and catalase activities were detected consistently throughout the core sediments down to the deepest slurry sample from 342.5 m below seafloor (mbsf). Detectable enzyme activities predicted the existence of a sizable population of viable aerobic microorganisms even in deep subseafloor habitats. The subsequent quantitative cultivation using solid media represented remarkably high numbers of aerobic, heterotrophic microbial populations (e.g., maximally 4.4x10(7) cells cm(-3) at 342.5 mbsf). Analysis of 16S rRNA gene sequences revealed that the predominant cultivated microbial components were affiliated with the genera Bacillus, Shewanella, Pseudoalteromonas, Halomonas, Pseudomonas, Paracoccus, Rhodococcus, Microbacterium, and Flexibacteracea. Many of the predominant and scarce isolates produced a variety of extra-cellular enzymes such as proteases, amylases, lipases, chitinases, phosphatases, and deoxyribonucleases. Our results indicate that microbes in the deep subseafloor environment off Shimokita are metabolically active and that the cultivable populations may have a great potential in biotechnology.

  11. Phylogenetic and enzymatic diversity of deep subseafloor aerobic microorganisms in organics- and methane-rich sediments off Shimokita Peninsula.

    PubMed

    Kobayashi, Tohru; Koide, Osamu; Mori, Kozue; Shimamura, Shigeru; Matsuura, Takae; Miura, Takeshi; Takaki, Yoshihiro; Morono, Yuki; Nunoura, Takuro; Imachi, Hiroyuki; Inagaki, Fumio; Takai, Ken; Horikoshi, Koki

    2008-07-01

    "A meta-enzyme approach" is proposed as an ecological enzymatic method to explore the potential functions of microbial communities in extreme environments such as the deep marine subsurface. We evaluated a variety of extra-cellular enzyme activities of sediment slurries and isolates from a deep subseafloor sediment core. Using the new deep-sea drilling vessel "Chikyu", we obtained 365 m of core sediments that contained approximately 2% organic matter and considerable amounts of methane from offshore the Shimokita Peninsula in Japan at a water depth of 1,180 m. In the extra-sediment fraction of the slurry samples, phosphatase, esterase, and catalase activities were detected consistently throughout the core sediments down to the deepest slurry sample from 342.5 m below seafloor (mbsf). Detectable enzyme activities predicted the existence of a sizable population of viable aerobic microorganisms even in deep subseafloor habitats. The subsequent quantitative cultivation using solid media represented remarkably high numbers of aerobic, heterotrophic microbial populations (e.g., maximally 4.4x10(7) cells cm(-3) at 342.5 mbsf). Analysis of 16S rRNA gene sequences revealed that the predominant cultivated microbial components were affiliated with the genera Bacillus, Shewanella, Pseudoalteromonas, Halomonas, Pseudomonas, Paracoccus, Rhodococcus, Microbacterium, and Flexibacteracea. Many of the predominant and scarce isolates produced a variety of extra-cellular enzymes such as proteases, amylases, lipases, chitinases, phosphatases, and deoxyribonucleases. Our results indicate that microbes in the deep subseafloor environment off Shimokita are metabolically active and that the cultivable populations may have a great potential in biotechnology. PMID:18368287

  12. Comparison of the physical and geotechnical properties of gas-hydrate-bearing sediments from offshore India and other gas-hydrate-reservoir systems

    USGS Publications Warehouse

    Winters, William J.; Wilcox-Cline, R.W.; Long, P.; Dewri, S.K.; Kumar, P.; Stern, Laura A.; Kerr, Laura A.

    2014-01-01

    The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom temperature may govern the hydrate formation process, but it is the host sediment that commonly dictates final hydrate habit, and whether hydrate may be economically developed.In this paper, the physical properties of hydrate-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other hydrate reservoirs. Properties from the hydrate-free Kerala-Konkan basin off the west coast of India are also presented. Coarser-grained reservoirs (permafrost-related and marine) may contain high gas-hydrate-pore saturations, while finer-grained reservoirs may contain low-saturation disseminated or more complex gas-hydrates, including nodules, layers, and high-angle planar and rotational veins. However, even in these fine-grained sediments, gas hydrate preferentially forms in coarser sediment or fractures, when present. The presence of hydrate in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the Andaman Islands.Properties of individual NGHP-01 wells and regional trends are discussed in detail. However, comparison of marine and permafrost-related Arctic reservoirs provides insight into the inter-relationships and common traits between physical properties and the morphology of gas-hydrate reservoirs regardless of location. Extrapolation of properties from one location to another also enhances our understanding of gas-hydrate reservoir systems. Grain size and porosity effects on permeability are critical, both locally to trap gas and regionally to provide fluid flow to hydrate reservoirs. Index properties corroborate more advanced

  13. Anaerobic methane oxidation and a deep H 2S sink generate isotopically heavy sulfides in Black Sea sediments

    NASA Astrophysics Data System (ADS)

    Jørgensen, Bo Barker; Böttcher, Michael E.; Lüschen, Holger; Neretin, Lev N.; Volkov, Igor I.

    2004-05-01

    The main terminal processes of organic matter mineralization in anoxic Black Sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2-4 m and methanogenesis below the sulfate zone. The modern marine deposits comprise a ca. 1-m-deep layer of coccolith ooze and underlying sapropel, below which sea water ions penetrate deep down into the limnic Pleistocene deposits from >9000 years BP. Sulfate reduction rates have a subsurface maximum at the SO 42--CH 4 transition where H 2S reaches maximum concentration. Because of an excess of reactive iron in the deep limnic deposits, most of the methane-derived H 2S is drawn downward to a sulfidization front where it reacts with Fe(III) and with Fe 2+ diffusing up from below. The H 2S-Fe 2+ transition is marked by a black band of amorphous iron sulfide above which distinct horizons of greigite and pyrite formation occur. The pore water gradients respond dynamically to environmental changes in the Black Sea with relatively short time constants of ca. 500 yr for SO 42- and 10 yr for H 2S, whereas the FeS in the black band has taken ca. 3000 yr to accumulate. The dual diffusion interfaces of SO 42--CH 4 and H 2S-Fe 2+ cause the trapping of isotopically heavy iron sulfide with δ 34S = +15 to +33‰ at the sulfidization front. A diffusion model for sulfur isotopes shows that the SO 42- diffusing downward into the SO 42--CH 4 transition has an isotopic composition of +19‰, close to the +23‰ of H 2S diffusing upward. These isotopic compositions are, however, very different from the porewater SO 42- (+43‰) and H 2S (-15‰) at the same depth. The model explains how methane-driven sulfate reduction combined with a deep H 2S sink leads to isotopically heavy pyrite in a sediment open to diffusion. These results have general implications for the marine sulfur cycle and for the interpretation of sulfur isotopic data in modern sediments and in sedimentary rocks throughout earth's history.

  14. On the path to the digital rock physics of gas hydrate-bearing sediments - processing of in situ synchrotron-tomography data

    NASA Astrophysics Data System (ADS)

    Sell, Kathleen; Saenger, Erik H.; Falenty, Andrzej; Chaouachi, Marwen; Haberthür, David; Enzmann, Frieder; Kuhs, Werner F.; Kersten, Michael

    2016-08-01

    To date, very little is known about the distribution of natural gas hydrates in sedimentary matrices and its influence on the seismic properties of the host rock, in particular at low hydrate concentration. Digital rock physics offers a unique approach to this issue yet requires good quality, high-resolution 3-D representations for the accurate modeling of petrophysical and transport properties. Although such models are readily available via in situ synchrotron radiation X-ray tomography, the analysis of such data asks for complex workflows and high computational power to maintain valuable results. Here, we present a best-practice procedure complementing data from Chaouachi et al. (2015) with data post-processing, including image enhancement and segmentation as well as exemplary numerical simulations of an acoustic wave propagation in 3-D using the derived results. A combination of the tomography and 3-D modeling opens a path to a more reliable deduction of properties of gas hydrate-bearing sediments without a reliance on idealized and frequently imprecise models.

  15. Controls on the physical properties of gas-hydrate-bearing sediments because of the interaction between gas hydrate and porous media

    USGS Publications Warehouse

    Lee, Myung W.; Collett, Timothy S.

    2005-01-01

    Physical properties of gas-hydrate-bearing sediments depend on the pore-scale interaction between gas hydrate and porous media as well as the amount of gas hydrate present. Well log measurements such as proton nuclear magnetic resonance (NMR) relaxation and electromagnetic propagation tool (EPT) techniques depend primarily on the bulk volume of gas hydrate in the pore space irrespective of the pore-scale interaction. However, elastic velocities or permeability depend on how gas hydrate is distributed in the pore space as well as the amount of gas hydrate. Gas-hydrate saturations estimated from NMR and EPT measurements are free of adjustable parameters; thus, the estimations are unbiased estimates of gas hydrate if the measurement is accurate. However, the amount of gas hydrate estimated from elastic velocities or electrical resistivities depends on many adjustable parameters and models related to the interaction of gas hydrate and porous media, so these estimates are model dependent and biased. NMR, EPT, elastic-wave velocity, electrical resistivity, and permeability measurements acquired in the Mallik 5L-38 well in the Mackenzie Delta, Canada, show that all of the well log evaluation techniques considered provide comparable gas-hydrate saturations in clean (low shale content) sandstone intervals with high gas-hydrate saturations. However, in shaly intervals, estimates from log measurement depending on the pore-scale interaction between gas hydrate and host sediments are higher than those estimates from measurements depending on the bulk volume of gas hydrate.

  16. Microbial eukaryotic distributions and diversity patterns in a deep-sea methane seep ecosystem.

    PubMed

    Pasulka, Alexis L; Levin, Lisa A; Steele, Josh A; Case, David H; Landry, Michael R; Orphan, Victoria J

    2016-09-01

    Although chemosynthetic ecosystems are known to support diverse assemblages of microorganisms, the ecological and environmental factors that structure microbial eukaryotes (heterotrophic protists and fungi) are poorly characterized. In this study, we examined the geographic, geochemical and ecological factors that influence microbial eukaryotic composition and distribution patterns within Hydrate Ridge, a methane seep ecosystem off the coast of Oregon using a combination of high-throughput 18S rRNA tag sequencing, terminal restriction fragment length polymorphism fingerprinting, and cloning and sequencing of full-length 18S rRNA genes. Microbial eukaryotic composition and diversity varied as a function of substrate (carbonate versus sediment), activity (low activity versus active seep sites), sulfide concentration, and region (North versus South Hydrate Ridge). Sulfide concentration was correlated with changes in microbial eukaryotic composition and richness. This work also revealed the influence of oxygen content in the overlying water column and water depth on microbial eukaryotic composition and diversity, and identified distinct patterns from those previously observed for bacteria, archaea and macrofauna in methane seep ecosystems. Characterizing the structure of microbial eukaryotic communities in response to environmental variability is a key step towards understanding if and how microbial eukaryotes influence seep ecosystem structure and function.

  17. Microbial methane formation in deep aquifers of a coal-bearing sedimentary basin, Germany

    PubMed Central

    Gründger, Friederike; Jiménez, Núria; Thielemann, Thomas; Straaten, Nontje; Lüders, Tillmann; Richnow, Hans-Hermann; Krüger, Martin

    2015-01-01

    Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, and Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport. PMID:25852663

  18. A novel alveolate in bivalves with chemosynthetic bacteria inhabiting deep-sea methane seeps.

    PubMed

    Noguchi, Fumiya; Kawato, Masaru; Yoshida, Takao; Fujiwara, Yoshihiro; Fujikura, Katsunori; Takishita, Kiyotaka

    2013-01-01

    It has recently been unveiled that a wide variety of microbial eukaryotes (protists) occur in chemosynthetic ecosystems, such as hydrothermal vents and methane seeps. However, there is little knowledge regarding protists associated with endemic animals inhabiting these environments. In the present study, utilizing PCR techniques, we detected fragments of the small subunit ribosomal RNA gene (SSU rRNA gene) from a particular protist from gill tissues of a significant fraction of the vesicomyid clams Calyptogena soyoae and C. okutanii complex and of the mussel Bathymodiolus platifrons and B. japonicus, all of which harbor chemosynthetic endosymbiont bacteria and dominate methane seeps in Sagami Bay, Japan. Based on the phylogeny of SSU rRNA gene, the organism in question was shown to belong to Alveolata. It is noteworthy that this protist did not affiliate with any known alveolate group, although being deeply branched within the lineage of Syndiniales, for which the monophyly was constantly recovered, but not robustly supported. In addition, the protist detected using PCR followed by sequencing was localized within gill epithelial cells of B. platifrons with whole-mount fluorescence in situ hybridization. This protist may be an endoparasite or an endocommensal of Calyptogena spp. and Bathymodiolus spp., and possibly have physiological and ecological impacts on these bivalves.

  19. Isotopic analysis of methane by Cavity Ringdown Spectroscopy (CRDS) Application to the deep-sea Congolobe fan

    NASA Astrophysics Data System (ADS)

    Caprais, J.; Cathalot, C.; de Prunelé, A.; Ruffine, L.; Cassarino, L.; Le Bruchec, J.; Olu, K.; Rabouille, C.

    2013-12-01

    Channeling all the continental material exported from the Congo River to the terminal lobes, the Congo deep-sea fan constitutes an unrecognized hotspot for biology and biogeochemistry in the Atlantic Ocean. Assemblages of benthic ecosystems in this peculiar environment mimic the ones observed only in active cold-seep regions. Massive organic matter inputs from the Congo canyon likely induce a sedimentary production of reduced fluids bearing sulphide and methane. These reduced compounds may support the development of bacterial mats based on chemo-autotrophy and the presence of biological communities feeding on these mats, as already observed in sediment from the lobe zone. Yet, the processes and driving forces controlling the structure of benthic communities in the lobe of the Congo submarine canyon are still poorly understood. Isotopic fractionations occurring during methanogenesis (depletion), thermic alteration of organic matter (enrichment), and microbial anaerobic oxidation (enrichment) lead to distinct δ13CH4 signatures 1,2. Hence, stable methane isotopes are increasingly being used to determine methane source in the surrounding sediments and infer the gas provenance 3. In the frame of the Congolobe project, this study investigates the functioning of benthic communities in relation with the main environmental conditions. Specifically, it focuses on the applicability of the stable methane isotopes (δ13CH4) in understanding the sediment processes involved and the metabolism of the benthic ecosystems (chemo-autotrophy vs heterotrophy). A total of 5 sites (A, B, C, E, F) were investigated, at a water depth of approximately 5000 m. Three sites (A,F,C) were located along the main axis of the currently active lobe. Site B was located on a lobe which has been disconnected from the active canyon for several decades. Site E corresponds to a fossil lobe, and is taken as a reference station for hemipelagic deposition. At site C, sediment cores of ~20 cm length were

  20. The importance of methane and thiosulfate in the metabolism of the bacterial symbionts of two deep-sea mussels

    USGS Publications Warehouse

    Fisher, C.R.; Childress, J.J.; Oremland, R.S.; Bidigare, R.R.

    1987-01-01

    Undescribed hydrocarbon-seep mussels were collected from the Louisiana Slope, Gulf of Mexico, during March 1986, and the ultrastructure of their gills was examined and compared to Bathymodiolus thermophilus, a mussel collected from the deep-sea hydrothermal vents on the Gala??pagos Rift in March 1985. These closely related mytilids both contain abundant symbiotic bacteria in their gills. However, the bacteria from the two species are distinctly different in both morphology and biochemistry, and are housed differently within the gills of the two mussels. The symbionts from the seep mussel are larger than the symbionts from B. thermophilus and, unlike the latter, contain stacked intracytoplasmic membranes. In the seep mussel three or fewer symbionts appear to be contained in each host-cell vacuole, while in B. thermophilus there are often more than twenty bacteria visible in a single section through a vacuole. The methanotrophic nature of the seep-mussel symbionts was confirmed in 14C-methane uptake experiments by the appearance of label in both CO2 and acid-stable, non-volatile, organic compounds after a 3 h incubation of isolated gill tissue. Furthermore, methane consumption was correlated with methanol dehydrogenase activity in isolated gill tissue. Activity of ribulose-1,5-biphosphate (RuBP) carboxylase and 14CO2 assimilation studies indicate the presence of either a second type of symbiont or contaminating bacteria on the gills of freshly captured seep mussels. A reevaluation of the nutrition of the symbionts in B. thermophilus indicates that while the major symbiont is not a methanotroph, its status as a sulfur-oxidizing chemoautotroph, as has been suggested previously, is far from proven. ?? 1987 Springer-Verlag.

  1. Evaluation of CO2 Substitution for CH4 as a Mechanism for Concurrent Gas Production and CO2 Sequestration in Hydrate-Bearing Geologic Media

    NASA Astrophysics Data System (ADS)

    Moridis, G. J.; Reagan, M. T.; Silpngarmlert, S.

    2010-12-01

    Natural hydrates in geologic media contain CH4 in overwhelming abundance. In addition to the conventional methods of CH4-hydrate dissociation (depressurization, thermal stimulation, the use of inhibitors, and combinations thereof), CO2 substitution for CH4 has been proposed as a potential method that could simultaneously achieve two goals: the release of CH4 from the CH4-hydrates for gas production, and the replacement of CH4 by CO2 in the clathrates, thus forming either binary CH4+CO2-hydrates or pure CO2-hydrates and enabling CO2 sequestration. The reaction of CO2 substitution for CH4 in the clathrates is thermodynamically favorable, resulting in binary or CO2-hydrates that are more thermodynamically stable than CH4-hydrates. In this numerical study we first evaluate the performance of a new equation-of-state (EOS) module developed as a code unit for the TOUGH+ general simulator. The EOS describes the thermodynamic and flow behavior of binary CH4+CO2-hydrates in geologic media, and covers the entire composition spectrum in both the gas and the hydrate phase. The EOS includes fast parametric relationships that describe the 3-dimensional P-T-X phase diagram of the CH4+CO2+H2O system, which (a) were developed from 3D regression of thermodynamic data obtained from the CSMGem code (a statistical thermodynamics simulator that is based on the minimization of Gibbs energy of hydrate systems) and (b) were validated using laboratory measurements. The TOUGH+ simulator with the CH4+CO2-hydrate EOS is then validated using results from laboratory studies that involve replacement of CH4 by CO2 in hydrate-bearing cores. Finally, we investigate the technical feasibility of such replacement at the reservoir scale, and the conditions under which it may be successful, in realistic settings involving systems of vertical and horizontal wells.

  2. Anaerobic methane oxidation in low-organic content methane seep sediments

    USGS Publications Warehouse

    Pohlman, John W.; Riedel, Michael; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Lapham, Laura; Grabowski, Kenneth S.; Coffin, Richard B.; Spence, George D.

    2013-01-01

    Sulfate-dependent anaerobic oxidation of methane (AOM) is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps. In this study, we investigate how the presence of low-organic content sediment influences the capacity and efficiency of AOM at Bullseye vent, a gas hydrate-bearing cold seep offshore of Vancouver Island, Canada. The upper 8 m of sediment contains 14C. A fossil origin for the DIC precludes remineralization of non-fossil OM present within the sulfate zone as a significant contributor to pore water DIC, suggesting that nearly all sulfate is available for anaerobic oxidation of fossil seep methane. Methane flux from the SMT to the sediment water interface in a diffusion-dominated flux region of Bullseye vent was, on average, 96% less than at an OM-rich seep in the Gulf of Mexico with a similar methane flux regime. Evidence for enhanced methane oxidation capacity within OM-poor sediments has implications for assessing how climate-sensitive reservoirs of sedimentary methane (e.g., gas hydrate) will respond to ocean warming, particularly along glacially-influenced mid and high latitude continental margins.

  3. Evidence for large methane releases to the atmosphere from deep-sea gas-hydrate dissociation during the last glacial episode

    PubMed Central

    de Garidel-Thoron, Thibault; Beaufort, Luc; Bassinot, Franck; Henry, Pierre

    2004-01-01

    Past atmospheric methane-concentration oscillations recorded in polar ice cores vary together with rapid global climatic changes during the last glacial episode. In the “clathrate gun hypothesis,” massive releases of deep-sea methane from marine gas-hydrate dissociation led to these well known, global, abrupt warmings in the past. If evidence for such releases in the water column exists, however, the mechanism and eventual transfer to the atmosphere has not yet been documented clearly. Here we describe a high-resolution marine-sediment record of stable carbon isotopic changes from the Papua Gulf, off Papua New Guinea, which exhibits two extremely depleted excursions (down to -9‰) at ≈39,000 and ≈55,000 years. Morphological, isotopic, and trace metal evidence dismisses authigenic calcite as the main source of depleted carbon. Massive methane release associated with deep-sea gas-hydrate dissociation is the most likely cause for such large depletions of δ13C. The absence of a δ13C gradient in the water column during these events implies that the methane rose through the entire water column, reaching the sea–air interface and thus the atmosphere. Foraminiferal δ18O composition suggests that the rise of the methane in the water column created an upwelling flow. These inferred emission events suggest that during the last glacial episode, this process was likely widespread, including tropical regions. Thus, the release of methane from the ocean floor into the atmosphere cannot be dismissed as a strong positive feedback in climate dynamics processes. PMID:15197255

  4. Methane release from sediment seeps to the atmosphere is counteracted by highly active Methylococcaceae in the water column of deep oligotrophic Lake Constance.

    PubMed

    Bornemann, Maren; Bussmann, Ingeborg; Tichy, Lucas; Deutzmann, Jörg; Schink, Bernhard; Pester, Michael

    2016-08-01

    Methane emissions from freshwater environments contribute substantially to global warming but are under strong control of aerobic methane-oxidizing bacteria. Recently discovered methane seeps (pockmarks) in freshwater lake sediments have the potential to bypass this control by their strong outgassing activity. Whether this is counteracted by pelagic methanotrophs is not well understood yet. We used a (3)H-CH4-radiotracer technique and pmoA-based molecular approaches to assess the activity, abundance and community structure of pelagic methanotrophs above active pockmarks in deep oligotrophic Lake Constance. Above profundal pockmarks, methane oxidation rates (up to 458 nmol CH4 l(-1) d(-1)) exceeded those of the surrounding water column by two orders of magnitude and coincided with maximum methanotroph abundances of 0.6% of the microbial community. Phylogenetic analysis indicated a dominance of members of the Methylococcaceae in the water column of both, pockmark and reference sites, with most of the retrieved sequences being associated with a water-column specific clade. Communities at pockmark and reference locations also differed in parts, which was likely caused by entrainment of sediment-hosted methanotrophs at pockmark sites. Our results show that the release of seep-derived methane to the atmosphere is counteracted by a distinct methanotrophic community with a pronounced activity throughout bottom waters. PMID:27267930

  5. Methane release from sediment seeps to the atmosphere is counteracted by highly active Methylococcaceae in the water column of deep oligotrophic Lake Constance.

    PubMed

    Bornemann, Maren; Bussmann, Ingeborg; Tichy, Lucas; Deutzmann, Jörg; Schink, Bernhard; Pester, Michael

    2016-08-01

    Methane emissions from freshwater environments contribute substantially to global warming but are under strong control of aerobic methane-oxidizing bacteria. Recently discovered methane seeps (pockmarks) in freshwater lake sediments have the potential to bypass this control by their strong outgassing activity. Whether this is counteracted by pelagic methanotrophs is not well understood yet. We used a (3)H-CH4-radiotracer technique and pmoA-based molecular approaches to assess the activity, abundance and community structure of pelagic methanotrophs above active pockmarks in deep oligotrophic Lake Constance. Above profundal pockmarks, methane oxidation rates (up to 458 nmol CH4 l(-1) d(-1)) exceeded those of the surrounding water column by two orders of magnitude and coincided with maximum methanotroph abundances of 0.6% of the microbial community. Phylogenetic analysis indicated a dominance of members of the Methylococcaceae in the water column of both, pockmark and reference sites, with most of the retrieved sequences being associated with a water-column specific clade. Communities at pockmark and reference locations also differed in parts, which was likely caused by entrainment of sediment-hosted methanotrophs at pockmark sites. Our results show that the release of seep-derived methane to the atmosphere is counteracted by a distinct methanotrophic community with a pronounced activity throughout bottom waters.

  6. Methane exsolution due to carbon dioxide injection in deep saline reservoirs: Implications for geologic carbon sequestration

    NASA Astrophysics Data System (ADS)

    Oldenburg, C. M.; Doughty, C.; Spycher, N.

    2013-12-01

    Deep saline formations targeted for geologic carbon sequestration, especially in areas known for hydrocarbon production, may contain significant concentrations of dissolved CH4. As CO2 enters the formation water either in its free phase or dissolved forms, CH4 tends to exsolve from the water, potentially causing complications for geologic carbon sequestration. We have used numerical simulation with TOUGH2/EOS7C to investigate the process of CH4 exsolution caused by CO2 injection into deep formations containing water saturated with CH4. We validated the solubility model in TOUGH2/EOS7C against published measurements of solubility and corresponding Henry's Law coefficients which show that CO2 and CH4 solubilities actually increase with dissolution of the other component. Exsolution occurs because the partial pressures exerted by dissolved CO2 and CH4 in water exceed the static pressure, which can lead to the formation of a CH4-rich gas phase. We verified our results against a previously published one-dimensional test problem, and investigated the effects of numerical dispersion on the process. In 2D radial simulations of a model system, we found that highly concentrated CH4 gas regions form at the leading edge of the CO2 injection front, but the gas saturations in such regions are small. Because the gas saturations are small in the CH4-rich gas regions in the generic system studied here, (1) CH4 exsolution does not appear to be a problem for seismic monitoring of CO2 plumes, (2) reservoir pressurization due to dilution of supercritical CO2 by CH4 does not appear to be a concern, and (3) relative permeability is not strongly reduced.

  7. Methane Content and Distribution of Natural Gas Hydrate Accumulations in the Deep-Water Basins of the Bering Sea

    NASA Astrophysics Data System (ADS)

    Barth, G. A.; Scholl, D. W.; Childs, J. R.

    2005-12-01

    Seismic reflection images from the deep-water (>3500 m) Aleutian and Bowers Basins of the Bering Sea indicate an abundant presence of natural gas and gas hydrate. Distinctive velocity-amplitude anomalies, or VAMPs, stand out as both velocity pseudostructures and gas bright spots within the otherwise horizontal and uniform sedimentary reflection sequences. These are interpreted as methane chimneys overlain by interstitial gas hydrate caps. Hundreds of VAMPs have been imaged throughout the Bering Sea; several thousand are inferred to exist. Ongoing USGS development of an interpretive seismic database presents an opportunity to quantify the hydrate content of individual VAMPs and to explore the distribution of major and minor anomalies relative to basement topography, silica diagenesis features, ancient subduction boundary structures and sediment sources. We present quantitative estimates of the size and methane content of representative large VAMP structures, based on seismic reflection interval-time anomalies. Time-average and frame-component effective medium velocity models are used to relate hydrate concentration to velocity anomaly. For this specific case, differences between the two models are minimal for hydrate concentrations <35% of pore space. To facilitate modeling of sediment dominated by diatomaceous ooze, grain-scale elastic moduli for diatom frustules are back-calculated to be ~5 GPa, assuming shear and bulk modulus are equal. Maximum velocity anomaly observed within the VAMPs is +235 m/s in the hydrate zone, relative to a background P-wave velocity of 1600 m/s. This corresponds to hydrate concentration ~40% of pore space (or ~20% of bulk rock). Hydrate distribution appears to be lithologically controlled within a section of alternating turbidite and diatomaceous sediments. It is preferentially located in a zone ~40 to 90 m above the gas hydrate BSR. Free gas is most concentrated immediately below the hydrate BSR, which lies at ~360 m bsf. Evidence for

  8. Preparation of a nitro-substituted tris(indolyl)methane modified silica in deep eutectic solvents for solid-phase extraction of organic acids.

    PubMed

    Wang, Na; Wang, Jiamin; Liao, Yuan; Shao, Shijun

    2016-05-01

    A new sorbent for solid-phase extraction was synthesized by chemical immobilization of nitro-substituted tris(indolyl)methane on silica in new and green deep eutectic solvents. Elemental analysis results indicated that deep eutectic solvents could be an alternative to the traditional solvents in preparing nitro-substituted tris(indolyl)methane modified silica. Coupled with high performance liquid chromatography, the extraction performance of the sorbent was evaluated by using four organic acids as model analytes. The rebinding experiments results showed that the nitro-substituted tris(indolyl)methane modified silica sorbent had a good adsorption capacity towards the selected organic acids. Under the appropriate experimental conditions, good precision and wide linear ranges with coefficient of determination (R(2)) of higher than 0.9957 were obtained, and the limits of detection were in the range of 0.50-2.0μgL(-1) for the organic acids tested. The developed solid-phase extraction-high performance liquid chromatography-diode array detection (SPE-HPLC-DAD) method was successfully applied for the determination of organic acids in two drinking samples with recoveries ranging from 76.7% to 110.0% and 67.7% to 104.0% for all the selected organic acids, respectively.

  9. Harnessing methane

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    The total methane resource in hydrates—ice-like substances found in deep ocean sediments and Arctic permafrost—exceeds the energy content of all other fossil fuel resources,such as coal, oil, and conventional gas, according to the U.S. Geological Survey (USGS).The Methane Hydrate Research and Development Act, signed into law by U.S. President Bill Clinton on May 3, establishes a new federal commitment to developing methane hydrates, which has been touted as a potentially clean energy source that could make the U.S. less dependent on foreign sources of energy. The bill authorizes $47.5 million over five years for the Department of Energy to establish a federal methane hydrate research and development program.

  10. Noble gases, nitrogen, and methane from the deep interior to the atmosphere of Titan

    NASA Astrophysics Data System (ADS)

    Glein, Christopher R.

    2015-04-01

    Titan's thick N2-CH4 atmosphere is unlike any in the Solar System, and its origin has been shrouded in mystery for over half a century. Here, I perform a detailed analysis of chemical and isotopic data from the Cassini-Huygens mission to develop the hypothesis that Titan's (non-photochemical) atmospheric gases came from deep within. It is suggested that Titan's CH4, N2, and noble gases originated in a rocky core buried inside the giant satellite, and hydrothermal and cryovolcanic processes were critical to the creation of Titan's atmosphere. Mass balance and chemical equilibrium calculations demonstrate that all aspects of this hypothesis can be considered geochemically plausible with respect to contemporary observational, experimental, and theoretical knowledge. Specifically, I show that a rocky core with a bulk noble gas content similar to that in CI carbonaceous meteorites would contain sufficient 36Ar and 22Ne to explain their reported abundances. I also show that Henry's law constants for noble gases in relevant condensed phases can be correlated with the size of their atoms, which leads to expected mixing ratios for 84Kr (∼0.2 ppbv) and 132Xe (∼0.01 ppbv) that can explain why these species have yet to be detected (Huygens upper limit <10 ppbv). The outgassing of volatiles into Titan's atmosphere may be restricted by the stability of clathrate hydrates in Titan's interior. The noble gas geochemistry also provides significant new insights into the origin of N2 and CH4 on Titan, as I find that Ar and N2, and Kr and CH4 should exhibit similar phase partitioning behavior on Titan. One implication is that over 95% of Titan's N2 may still reside in the interior. Another key result is that the upper limit from the Huygens GC-MS on the Kr/CH4 ratio in Titan's atmosphere is far too low to be consistent with accretion of primordial CH4 clathrate, which motivates me to consider endogenic production of CH4 from CO2 as a result of geochemical reactions between liquid

  11. Methane Gradients Associated With a Small, Deep Lake on the Ice-Free Margin of Western Greenland

    NASA Astrophysics Data System (ADS)

    Webster, K. D.; White, J. R.; Young, S.; Pratt, L. M.

    2012-12-01

    Northern wetlands are thought to contribute from < 6 - 25 % of Earth's annual atmospheric methane inputs. However, despite extensive areal coverage, little is known about methane emissions from small lakes (< 540 ha) in the Arctic. We report initial results of methane concentrations in air, soil and water column associated with Potentilla Lake (informal name), near Kangerlussuaq, Greenland (N 67° 04.888', W 050° 21.084'). Potentilla Lake has a surface area of 1.8 ha and a maximum depth of 8 m. We measured methane concentrations in the hypolimnion, metalimnion, and epilimnion of Potentilla Lake as well as surrounding soils and atmosphere. The dissolved methane concentrations in the water column were collected using a gas stripping method. Methane concentrations in atmosphere, soils and water were analyzed on a Los Gatos Instruments MCIA employing cavity enhanced absorption spectroscopy with off-axis ICOS technology. Additionally, a Boreal open-path laser (OPL) for methane was used to measure the average atmospheric methane concentration across the long axis (283 m) of the lake for a period of 37 hrs from 12:00 pm on July 20, to 1:00 am on July 22, 2012. The laser was 0.8 m above the surface of the lake and micrometeorology was collected with a Davis Vantage Vue meteorological station. The OPL measured atmospheric methane concentrations once every minute and 13 seconds while the meteorological station recorded conditions every minute. A linear interpolation was used to pair the data for statistical analysis in order to correct for the differing data collection rates. Hypolimnetic methane concentration was 6000 ppm, metalimnetic concentration was 22 ppm, and the concentration of methane in the epilimnion was 62 ppm. Atmospheric methane concentrations from the OPL ranged from 1.56 to 1.85 ppmv over the duration of the measurement period and showed statistically significant relationships with wind speed (y = -0.0237x + 1.7241, P << 0.01, R2 = 0.19) and humidity (y = 0

  12. CO2 Exchange in a Methane Hydrate Reservoir: Ignik Sikumi #1 Alaska Field Trial Operations and Summary Results

    NASA Astrophysics Data System (ADS)

    Hester, K. C.; Farrell, H.; Howard, J. J.; Martin, K.; Raterman, K.; Schoderbek, D.; Smith, B.; Silpngarmlert, S.

    2012-12-01

    In the winter of 2012, a CO2 exchange field trial was performed at Prudhoe Bay, Alaska. The goal was to demonstrate the feasibility of CO2 hydrate exchange technology, developed in the laboratory, on a natural methane hydrate-bearing reservoir. This included verifying the chemical exchange of CO2 with methane in addition to maintaining injectivity. Drilled in 2011, the Ignik Sikumi #1 well was perforated in February 2012. The pilot was designed as a 'huff and puff' style test where a single well is used first for injection then followed with production. The target for the test was a 10 m sand zone estimated to contain 70-80% hydrate saturation. For 13 days, over 5600 m3 of a CO2 mixture (77mol% N2, 23 mol% CO2) were injected in the hydrate-bearing interval. Injectivity was maintained over this period. Following injection, flow back commenced over a 30 day period. The production started by maintaining a bottom hole pressure above the dissociation pressure above methane hydrate. At later times, the bottom hole pressure was lowered causing both pore space fluids to be produced along with dissociation of non-exchanged original methane hydrate. In total, over 23,700 m3 of methane was produced over the production period.

  13. Changes in deep-sea carbonate-hosted microbial communities associated with high and low methane flux

    NASA Astrophysics Data System (ADS)

    Case, D. H.; Steele, J. A.; Chadwick, G.; Mendoza, G. F.; Levin, L. A.; Orphan, V. J.

    2012-12-01

    Methane seeps on continental shelves are rich in authigenic carbonates built of methane-derived carbon. These authigenic carbonates are home to micro- and macroscopic communities whose compositions are thus far poorly constrained but are known to broadly depend on local methane flux. The formation of authigenic carbonates is itself a result of microbial metabolic activity, as associations of anaerobic methane oxidizing archaea (ANME) and sulfate reducing bacteria (SRB) in the sediment subsurface increase both dissolved inorganic carbon (DIC) and alkalinity in pore waters. This 1:1 increase in DIC and alkalinity promotes the precipitation of authigenic carbonates. In this study, we performed in situ manipulations to test the response of micro- and macrofaunal communities to a change in methane flux. Methane-derived authigenic carbonates from two locations at Hydrate Ridge, OR, USA (depth range 595-604 mbsl), were transplanted from "active" cold seep sites (high methane flux) to "inactive" background sites (low methane flux), and vise versa, for one year. Community diversity surveys using T-RFLP and 16S rRNA clone libraries revealed how both bacterial and archaeal assemblages respond to this change in local environment, specifically demonstrating reproducible shifts in different ANME groups (ANME-1 vs. ANME-2). Animal assemblage composition also shifted during transplantation; gastropod representation increased (relative to control rocks) when substrates were moved from inactive to active sites and polychaete, crustacean and echinoderm representation increased when substrates were moved from active to inactive sites. Combined with organic and inorganic carbon δ13C measurements and mineralogy, this unique in situ experiment demonstrates that authigenic carbonates are viable habitats, hosting microbial and macrofaunal communities capable of responding to changes in external environment over relatively short time periods.

  14. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    SciTech Connect

    Donn McGuire; Thomas Williams; Bjorn Paulsson; Alexander Goertz

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a drilling hazard by the oil and gas industry for years. Drilling engineers working in Russia, Canada and the USA have documented numerous problems, including drilling kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates as a potential energy source agree that the resource potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained from physical samples taken from actual hydrate-bearing rocks. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The project team drilled and continuously cored the Hot Ice No. 1 well on Anadarko-leased acreage beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and used for determining physical characteristics of hydrates and surrounding rock. After the well was logged, a 3D vertical seismic profile (VSP) was recorded to calibrate the shallow geologic section with seismic data and to investigate techniques to better resolve lateral subsurface variations of potential hydrate-bearing strata. Paulsson Geophysical Services, Inc. deployed their 80 level 3C clamped borehole seismic receiver array in the wellbore to record samples every 25 ft. Seismic vibrators were successively positioned at 1185 different surface positions in a circular pattern around the wellbore. This technique generated a 3D image of the subsurface. Correlations were

  15. Laboratory controls of precursor and temperature on the kinetics and isotopic fractionations of microbial methane for deep subsurface environments

    NASA Astrophysics Data System (ADS)

    Ling, Y.; Lin, L.; Wang, P.; Sun, C.

    2009-12-01

    In subsurface environments, the mineralization of organic carbon involves complex interactions among geological and microbial processes. As the most reduced form and the shortest hydrocarbon chain, methane, is the final product of both microbial degradation and thermal-cracking of organic matter, it serves as the connection of carbon cycles between different reservoirs. Of various mechanisms for methane formation, microbial methane constitutes 85% of the total methane inventory investigated by far. However, the mechanisms and resultant carbon isotope fingerprints of methanogenesis in environments still remained largely unknown. The types of precursors and temperature might be the most critical factors governing methanogenesis. Lots of studies have been investigating the mechanisms responsible for methanogenesis by pure cultures, but it still remains obscure with regard to which precursors are predominantly utilized by methanogens in natural settings. The effect of temperature is especially prominent for anoxic sediments within which the temperature increases with depth in accordance with the local geotherm. Commonly observed temperatures for methanogenesis span from ambient temperature to 90OC, a temperature range for most diagenetic reactions. In order to address how different precursors would be activated for microbially catalytic methane formation upon different temperatures, we incubated the sediments collected from Kuan-Tzu-Ling hot spring at temperatures up to 90OC. Five precursors including acetate, formate, methanol, methylamine, and hydrogen were added with the inocula to stimulate methanogenesis and inhibit fermentation, and were monitored together with methane production through time. Results of this experiments indicated that methanogenesis was positive at temperatures from room temperature to 80OC and precursors investigated despite substantial variations in the maximum rates and yields. In the experiment supplied with hydrogen and formate

  16. Simulation of the advective methane transport and AOM in Shenhu area, the Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Liu, L.; Wu, N.

    2012-04-01

    Anaerobic Oxidation of Methane (AOM) occurs in the transition zone between the presence of sulfate and methane. This reaction is an important process for methane and the global carbon cycle. Methane gas hydrates bearing sediments were recovered in Shenhu Area, the Northern South China Sea, and methane advective transport was detected in this area as well. A one dimension numerical simulation tool was implemented to study the AOM process combined with the advective methane transport in Shenhu Area according to the local drilling data and geochemical information. The modeled results suggest that local methane flux will be consumed in the sediment column via dissolution, sorption and AOM reaction. A portion of methane will enter water column and possibly atmosphere if the methane flux was one order of magnitude higher than current level. Furthermore, the calculated rates of AOM in Shenhu area range similar to that of gas hydrate mounds in Mexico Golf. However, AOM is ability to consume more methane than that in Golf of Mexico due to the lower permeable sediment associated with a deeper sulfate methane transition layer.

  17. Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

    SciTech Connect

    McGrail, B. Peter; Schaef, Herbert T.; White, Mark D.; Zhu, Tao; Kulkarni, Abhijeet S.; Hunter, Robert B.; Patil, Shirish L.; Owen, Antionette T.; Martin, P F.

    2007-09-01

    Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO2 for enhanced recovery of an unconventional but potentially very important source of natural gas, gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally. The EGHR (Enhanced Gas Hydrate Recovery) concept takes advantage of the physical and thermodynamic properties of mixtures in the H2O-CO2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a LCO2-Lw microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Small scale column experiments show injection of the emulsion into a CH4 hydrate rich sand results in the release of CH4 gas and the formation of CO2 hydrate

  18. Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 ka in Fram Strait, the deep-water gateway to the Arctic

    NASA Astrophysics Data System (ADS)

    Consolaro, C.; Rasmussen, T. L.; Panieri, G.; Mienert, J.; Bünz, S.; Sztybor, K.

    2014-10-01

    We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (∼80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dating reveals a detailed chronology for the last 14 ka BP. The δ13C record measured on the benthic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values, as low as -4.37‰ in the Bølling-Allerød interstadials and as low as -3.41‰ in the early Holocene. After cleaning procedure designed to remove all authigenic carbonate coatings on benthic foraminiferal tests, the 13C values are still negative (as low as -2.75‰). We have interpreted these negative carbon isotope excursions (CIEs) to record past methane release events, resulting from the incorporation of 13C-depleted carbon from methane emissions into the benthic foraminiferal shells. The CIEs during the Bølling-Allerød interstadials and the early Holocene relate to periods of ocean warming, sea level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

  19. Deep-sea survey for the detection of methane at the “Santa Maria di Leuca” cold-water coral mounds (Ionian Sea, South Italy)

    NASA Astrophysics Data System (ADS)

    Etiope, G.; Savini, A.; Lo Bue, N.; Favali, P.; Corselli, C.

    2010-03-01

    The "Santa Maria di Leuca" Cold-Water Coral (CWC) province (northern Ionian Sea) was investigated for the first time to detect eventual occurrence of methane anomalies as a possible indication of hydrocarbon seepage stimulating the coral growth. Most coral mounds have developed in correspondence with tectonic scarps and faults, orthogonal to the southern margin and trending NW-SE, which could be potential sites of gas escape. A visual and instrumental inspection was performed by using a new deep-sea probe equipped with video-cameras, sonar, CTD, methane sensors, and a water sampler. Eight areas were explored by 10 surveys, depths ranging from 380 to 1100 m, for a total of more than 26 h of continuous video and instrumental recording. Sediments were also sampled by gravity corers and analysed in laboratory. The images allowed to assess distribution, abundance and geometry of the colonies, most of which are developed on morphological highs often characterised by tectonic scarps. All data indicate however the lack of a significant occurrence of methane, both in seawater and sediments. No direct or indirect expressions of gas seepage were recognised on the seabed. Weak methane anomalies were detected only in seawater at the base of some fault-linked scarps, where more reducing conditions and bacterial methanogenesis are possibly enhanced by less water circulation. The faults are not fluid-bearing as previously suggested by high-resolution geophysical signatures. The development of the coral colonies thus cannot be attributed to seeping fluids, but to a favourable physiographic position with exposure to nutrient-rich currents.

  20. Molecular isotopic evidence for anaerobic oxidation of methane in deep-sea hydrothermal vent environment in Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Uchida, M.; Takai, K.; Inagaki, F.

    2003-04-01

    Large amount of methane in anoxic marine sediments as well as cold seeps and hydrothermal vents is recycled through for an anoxic oxidation of methane processes. Now that combined results of field and laboratory studies revealed that microbiological activity associated with syntrophic consortium of archaea performing reversed methanogenesis and sulfate-reducing bacteria is significant roles in methane recycling, anaerobic oxidation of methane (AOM). In this study, we examined the diversity of archaeal and bacterial assemblages of AOM using compound-specific stable carbon isotopic and phylogenetic analyses. "Iheya North" in Okinawa Trough is sediment-rich, back arc type hydrothermal system (27^o47'N, 126^o53'E). Sediment samples were collected from three sites where are "bubbling sites", yellow-colored microbial mats are formed with continuous bubbling from the seafloor bottom, vent mussel's colonies site together with slowly venting and simmering, and control site off 100 m distance from thermal vent. This subsea floor structure has important effect in the microbial ecosystem and interaction between their activity and geochemical processes in the subseafloor habitats. Culture-independent, molecular biological analysis clearly indicated the presence of thermophilic methanogens in deeper area having higher temperatures and potential activity of AMOs consortium in the shallower area. AMO is composed with sulfate-reducing bacterial components (Desulfosarcina spp.) and anoxic methane oxidizing archaea (ANME-2). These results were consistent with the results of compound-specific carbon analysis of archaeal biomarkers. They showed extremely depleted 13C contents (-80 ppm ˜ -100 ppm), which also appeared to be capable of directly oxidizing methane.

  1. Estimates of Biogenic Methane Production Rates in Deep Marine Sediments at Hydrate Ridge, Cascadia Margin ▿ †

    PubMed Central

    Colwell, F. S.; Boyd, S.; Delwiche, M. E.; Reed, D. W.; Phelps, T. J.; Newby, D. T.

    2008-01-01

    Methane hydrate found in marine sediments is thought to contain gigaton quantities of methane and is considered an important potential fuel source and climate-forcing agent. Much of the methane in hydrates is biogenic, so models that predict the presence and distribution of hydrates require accurate rates of in situ methanogenesis. We estimated the in situ methanogenesis rates in Hydrate Ridge (HR) sediments by coupling experimentally derived minimal rates of methanogenesis to methanogen biomass determinations for discrete locations in the sediment column. When starved in a biomass recycle reactor, Methanoculleus submarinus produced ca. 0.017 fmol methane/cell/day. Quantitative PCR (QPCR) directed at the methyl coenzyme M reductase subunit A gene (mcrA) indicated that 75% of the HR sediments analyzed contained <1,000 methanogens/g. The highest numbers of methanogens were found mostly from sediments <10 m below seafloor. By considering methanogenesis rates for starved methanogens (adjusted to account for in situ temperatures) and the numbers of methanogens at selected depths, we derived an upper estimate of <4.25 fmol methane produced/g sediment/day for the samples with fewer methanogens than the QPCR method could detect. The actual rates could vary depending on the real number of methanogens and various seafloor parameters that influence microbial activity. However, our calculated rate is lower than rates previously reported for such sediments and close to the rate derived using geochemical modeling of the sediments. These data will help to improve models that predict microbial gas generation in marine sediments and determine the potential influence of this source of methane on the global carbon cycle. PMID:18344348

  2. Geological modeling for methane hydrate reservoir characterization in the eastern Nankai Trough, offshore Japan

    NASA Astrophysics Data System (ADS)

    Tamaki, M.; Komatsu, Y.; Suzuki, K.; Takayama, T.; Fujii, T.

    2012-12-01

    The eastern Nankai trough, which is located offshore of central Japan, is considered as an attractive potential resource field of methane hydrates. Japan Oil, Gas and Metals National Corporation is planning to conduct a production test in early 2013 at the AT1 site in the north slope of Daini-Atsumi Knoll in the eastern Nankai Trough. The depositional environment of methane hydrate-bearing sediments around the production test site is a deep submarine-fan turbidite system, and it is considered that the reservoir properties should show lateral as well as vertical heterogeneity. Since the variations in the reservoir heterogeneity have an impact on the methane hydrate dissociation and gas production performance, precise geological models describing reservoir heterogeneity would be required for the evaluation of reservoir potentials. In preparation for the production test, 3 wells; two monitoring boreholes (AT1-MC and AT1-MT1) and a coring well (AT1-C), were newly acquired in 2012. In addition to a geotechnical hole drilling survey in 2011 (AT1-GT), totally log data from 2 wells and core data from 2 wells were obtained around the production test site. In this study, we conducted well correlations between AT1 and A1 wells drilled in 2003 and then, 3D geological models were updated including AT1 well data in order to refine hydrate reservoir characterization around the production test site. The results of the well correlations show that turbidite sand layers are characterized by good lateral continuity, and give significant information for the distribution morphology of sand-rich channel fills. We also reviewed previously conducted 3D geological models which consist of facies distributions and petrophysical properties distributions constructed from integration of 3D seismic data and a well data (A1 site) adopting a geostatistical approach. In order to test the practical validity of the previously generated models, cross-validation was conducted using AT1 well data. The

  3. Authigenic carbonates related to active seepage of methane-rich hot brines at the Cheops mud volcano, Menes caldera (Nile deep-sea fan, eastern Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Pierre, Catherine; Bayon, Germain; Blanc-Valleron, Marie-Madeleine; Mascle, Jean; Dupré, Stéphanie

    2014-06-01

    On the passive margin of the Nile deep-sea fan, the active Cheops mud volcano (MV; ca. 1,500 m diameter, ~20-30 m above seafloor, 3,010-3,020 m water depth) comprises a crater lake with hot (up to ca. 42 °C) methane-rich muddy brines in places overflowing down the MV flanks. During the Medeco2 cruise in fall 2007, ROV dives enabled detailed sampling of the brine fluid, bottom lake sediments at ca. 450 m lake depth, sub-surface sediments from the MV flanks, and carbonate crusts at the MV foot. Based on mineralogical, elemental and stable isotope analyses, this study aims at exploring the origin of the brine fluid and the key biogeochemical processes controlling the formation of these deep-sea authigenic carbonates. In addition to their patchy occurrence in crusts outcropping at the seafloor, authigenic carbonates occur as small concretions disseminated within sub-seafloor sediments, as well as in the bottom sediments and muddy brine of the crater lake. Aragonite and Mg-calcite dominate in the carbonate crusts and in sub-seafloor concretions at the MV foot, whereas Mg-calcite, dolomite and ankerite dominate in the muddy brine lake and in sub-seafloor concretions near the crater rim. The carbonate crusts and sub-seafloor concretions at the MV foot precipitated in isotopic equilibrium with bottom seawater temperature; their low δ13C values (-42.6 to -24.5‰) indicate that anaerobic oxidation of methane was the main driver of carbonate precipitation. By contrast, carbonates from the muddy lake brine, bottom lake concretions and crater rim concretions display much higher δ13C (up to -5.2‰) and low δ18O values (down to -2.8‰); this is consistent with their formation in warm fluids of deep origin characterized by 13C-rich CO2 and, as confirmed by independent evidence, slightly higher heavy rare earth element signatures, the main driver of carbonate precipitation being methanogenesis. Moreover, the benthic activity within the seafloor sediment enhances aerobic

  4. Methane Hydrates: Chapter 8

    USGS Publications Warehouse

    Boswell, Ray; Yamamoto, Koji; Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott

    2008-01-01

    Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be

  5. Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

    NASA Astrophysics Data System (ADS)

    Consolaro, C.; Rasmussen, T. L.; Panieri, G.; Mienert, J.; Bünz, S.; Sztybor, K.

    2015-04-01

    We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as -4.37‰ in CIE I, correlating with the Bølling-Allerød interstadials, and as low as -3.41‰ in CIE II, correlating with the early Holocene. In the Bølling-Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as -2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

  6. Authigenic minerals related to carbon and sulfur biogeochemical cycling from deep-sea active methane seeps offshore South-West Africa

    NASA Astrophysics Data System (ADS)

    Pierre, C.; Blanc-Valleron, M.; Demange, J.; Boudouma, O.; Pape, T.; Himmler, T.; Fekete, N.; Spiess, V.

    2011-12-01

    The South-West African continental margin is well known for occurrences of active methane-rich fluid seeps that are associated with seafloor pockmarks in a broad range of water depths, from the shelf to the deep basins. High gas flares in the water column, luxurious oases of benthic fauna, gas hydrate accumulations and diagenetic carbonate crusts have been observed at these seeps. During the M76/3a expedition of R/V METEOR (summer 2008) gravity cores recovered abundant authigenic carbonate concretions from five pockmarks of the South-West African margin including previously studied sites (Hydrate Hole, Worm Hole, Regab Pockmark) and two sites (Deep Hole, Baboon Cluster) newly discovered during the cruise. Carbonate concretions were mostly associated to sediments settled by seep-associated benthic macrofauna and bearing shallow gas hydrates. We present new results of the comprehensive analysis of the mineralogy and isotope geochemistry of the diagenetic carbonates sampled in the five pockmarks. The mineralogy of authigenic carbonates is dominated by magnesian calcite and aragonite, associated occasionally with dolomite. The oxygen and carbon isotopic compositions of authigenic carbonates (+2.4 < δ18O % V-PDB < +6.2 ; -61.0 < δ13C % V-PDB < -40.1) indicate that microbial anaerobic oxidation of methane (AOM) was the main process controling carbonate precipitation within sub-seafloor sediments deposited from the glacial-time up to the present. The frequent occurrence of diagenetic gypsum crystals within the sediments demonstrates that bio-irrigation with oxygenated bottom water by the burrowing activity of benthic fauna caused the secondary oxidation of reduced sulfur (hydrogen sulfide and pyrite) that was produced by sulfate reducting bacteria as a by-product of AOM; during the sulfide oxidation process, the released acidity induced the partial dissolution of carbonates. Our results demonstrate also the strong link that existed between the carbon and sulfur cycles

  7. Gas hydrate formation rates from dissolved-phase methane in porous laboratory specimens

    USGS Publications Warehouse

    Waite, William F.; Spangenberg, E.K.

    2013-01-01

    Marine sands highly saturated with gas hydrates are potential energy resources, likely forming from methane dissolved in pore water. Laboratory fabrication of gas hydrate-bearing sands formed from dissolved-phase methane usually requires 1–2 months to attain the high hydrate saturations characteristic of naturally occurring energy resource targets. A series of gas hydrate formation tests, in which methane-supersaturated water circulates through 100, 240, and 200,000 cm3 vessels containing glass beads or unconsolidated sand, show that the rate-limiting step is dissolving gaseous-phase methane into the circulating water to form methane-supersaturated fluid. This implies that laboratory and natural hydrate formation rates are primarily limited by methane availability. Developing effective techniques for dissolving gaseous methane into water will increase formation rates above our observed (1 ± 0.5) × 10−7 mol of methane consumed for hydrate formation per minute per cubic centimeter of pore space, which corresponds to a hydrate saturation increase of 2 ± 1% per day, regardless of specimen size.

  8. Relative abundances of methane- and sulfur-oxidizing symbionts in gills of the deep-sea hydrothermal vent mussel Bathymodiolus azoricus under pressure

    NASA Astrophysics Data System (ADS)

    Szafranski, Kamil M.; Piquet, Bérénice; Shillito, Bruce; Lallier, François H.; Duperron, Sébastien

    2015-07-01

    The deep-sea mussel Bathymodiolus azoricus dominates hydrothermal vent fauna in the Azores region. The gills of this species house methane- and sulfur-oxidizing bacteria that fulfill most of the mussel's nutritional requirements. Previous studies suggested that the ratio between methane- and sulfur-oxidizers could vary in response to the availability of electron donors in their environment, and this flexibility is considered a key factor in explaining the ecological success of the species. However, previous studies were based on non-isobaric recovery of specimens, with experiments at atmospheric pressure which may have induced artifacts. This study investigates the effect of pressure-related stress during recovery and experimentation on the relative abundances of bacterial symbionts. Mussel specimens were recovered for the first time using the pressure-maintaining device PERISCOP. Specimens were subsequently transferred into pressurized vessels and exposed to various chemical conditions. Using optimized fluorescence in situ hybridization-based approaches, relative abundance of symbionts were measured. Our results show that the recovery method (isobaric versus non-isobaric) does not influence the abundances of bacterial symbionts. Significant differences occur among specimens sampled from two contrasting sites. Exposure of mussels from the deeper site to sulfide and bicarbonate, and to bicarbonate alone, both resulted in a rapid and significant increase in the relative abundance of sulfur-oxidizers. Results reported herein are congruent with those from previous reports investigating mussels originating from shallow sites and kept at ambient pressure. Isobaric recovery and maintenance allowed us to perform in vivo experiments in specimens from a deeper site that could not be maintained alive at ambient pressure, and will greatly improve the chances of identifying the molecular mechanisms underlying the dialogue between bathymodioline hosts and symbionts.

  9. Methanothermococcus okinawensis sp. nov., a thermophilic, methane-producing archaeon isolated from a Western Pacific deep-sea hydrothermal vent system.

    PubMed

    Takai, Ken; Inoue, Akira; Horikoshi, Koki

    2002-07-01

    A novel thermophilic, methane-producing archaeon was isolated from a deep-sea hydrothermal vent chimney at the Iheya Ridge, in the Okinawa Trough, Japan. The cells were highly motile, irregular cocci, with a polar bundle of flagella. Growth was observed between 40 and 75 degrees C (optimum 60-65 degrees C; 30 min doubling time) and between pH 4.5 and 8.5 (optimum pH 6.7). The isolate was a strictly anaerobic autotroph capable of using hydrogen and carbon dioxide as sole sources of energy and carbon. Formate can serve as an alternative energy source. The G+C content of the genomic DNA was 33.5 mol%. Phylogenetic analysis based on 16S rDNA sequences and DNA-DNA hybridization analysis indicated that the isolate was closely related to members of the genera Methanococcus and Methanothermococcus. This isolate, however, could be differentiated from the previously described species of these genera on the basis of its physiological and molecular properties. The name Methanothermococcus okinawensis sp. nov is proposed, with the type strain IH1T (=JCM 11175T=DSM 14208T).

  10. The strength and rheology of methane clathrate hydrate

    USGS Publications Warehouse

    Durham, W.B.; Kirby, S.H.; Stern, L.A.; Zhang, W.

    2003-01-01

    Methane clathrate hydrate (structure I) is found to be very strong, based on laboratory triaxial deformation experiments we have carried out on samples of synthetic, high-purity, polycrystalline material. Samples were deformed in compressional creep tests (i.e., constant applied stress, ??), at conditions of confining pressure P = 50 and 100 MPa, strain rate 4.5 ?? 10-8 ??? ?? ??? 4.3 ?? 10-4 s-1, temperature 260 ??? T ??? 287 K, and internal methane pressure 10 ??? PCH4 ??? 15 MPa. At steady state, typically reached in a few percent strain, methane hydrate exhibited strength that was far higher than expected on the basis of published work. In terms of the standard high-temperature creep law, ?? = A??ne-(E*+PV*)/RT the rheology is described by the constants A = 108.55 MPa-n s-1, n = 2.2, E* = 90,000 J mol-1, and V* = 19 cm3 mol-1. For comparison at temperatures just below the ice point, methane hydrate at a given strain rate is over 20 times stronger than ice, and the contrast increases at lower temperatures. The possible occurrence of syntectonic dissociation of methane hydrate to methane plus free water in these experiments suggests that the high strength measured here may be only a lower bound. On Earth, high strength in hydrate-bearing formations implies higher energy release upon decomposition and subsequent failure. In the outer solar system, if Titan has a 100-km-thick near-surface layer of high-strength, low-thermal conductivity methane hydrate as has been suggested, its interior is likely to be considerably warmer than previously expected.

  11. Gas hydrate formation in the deep sea: In situ experiments with controlled release of methane, natural gas, and carbon dioxide

    USGS Publications Warehouse

    Brewer, P.G.; Orr, F.M.; Friederich, G.; Kvenvolden, K.A.; Orange, D.L.

    1998-01-01

    We have utilized a remotely operated vehicle (ROV) to initiate a program of research into gas hydrate formation in the deep sea by controlled release of hydrocarbon gases and liquid CO2 into natural sea water and marine sediments. Our objectives were to investigate the formation rates and growth patterns of gas hydrates in natural systems and to assess the geochemical stability of the reaction products over time. The novel experimental procedures used the carrying capacity, imaging capability, and control mechanisms of the ROV to transport gas cylinders to depth and to open valves selectively under desired P-T conditions to release the gas either into contained natural sea water or into sediments. In experiments in Monterey Bay, California, at 910 m depth and 3.9??C water temperature we find hydrate formation to be nearly instantaneous for a variety of gases. In sediments the pattern of hydrate formation is dependent on the pore size, with flooding of the pore spaces in a coarse sand yielding a hydrate cemented mass, and gas channeling in a fine-grained mud creating a veined hydrate structure. In experiments with liquid CO2 the released globules appeared to form a hydrate skin as they slowly rose in the apparatus. An initial attempt to leave the experimental material on the sea floor for an extended period was partially successful; we observed an apparent complete dissolution of the liquid CO2 mass, and an apparent consolidation of the CH4 hydrate, over a period of about 85 days.

  12. Anomalous preservation of pure methane hydrate at 1 atm

    USGS Publications Warehouse

    Stern, L.A.; Circone, S.; Kirby, S.H.; Durham, W.B.

    2001-01-01

    Direct measurement of decomposition rates of pure, polycrystalline methane hydrate reveals a thermal regime where methane hydrate metastably `preserves' in bulk by as much as 75 K above its nominal equilibrium temperature (193 K at 1 atm). Rapid release of the sample pore pressure at isothermal conditions between 242 and 271 K preserves up to 93% of the hydrate for at least 24 h, reflecting the greatly suppressed rates of dissociation that characterize this regime. Subsequent warming through the H2O ice point then induces rapid and complete dissociation, allowing controlled recovery of the total expected gas yield. This behavior is in marked contrast to that exhibited by methane hydrate at both colder (193-240 K) and warmer (272-290 K) test conditions, where dissociation rates increase monotonically with increasing temperature. Anomalous preservation has potential application for successful retrieval of natural gas hydrate or hydrate-bearing sediments from remote settings, as well as for temporary low-pressure transport and storage of natural gas.

  13. Methane hydrate distribution from prolonged and repeated formation in natural and compacted sand samples: X-ray CT observations

    SciTech Connect

    Rees, E.V.L.; Kneafsey, T.J.; Seol, Y.

    2010-07-01

    To study physical properties of methane gas hydrate-bearing sediments, it is necessary to synthesize laboratory samples due to the limited availability of cores from natural deposits. X-ray computed tomography (CT) and other observations have shown gas hydrate to occur in a number of morphologies over a variety of sediment types. To aid in understanding formation and growth patterns of hydrate in sediments, methane hydrate was repeatedly formed in laboratory-packed sand samples and in a natural sediment core from the Mount Elbert Stratigraphic Test Well. CT scanning was performed during hydrate formation and decomposition steps, and periodically while the hydrate samples remained under stable conditions for up to 60 days. The investigation revealed the impact of water saturation on location and morphology of hydrate in both laboratory and natural sediments during repeated hydrate formations. Significant redistribution of hydrate and water in the samples was observed over both the short and long term.

  14. Molecular analysis of deep-sea hydrothermal vent aerobic methanotrophs by targeting genes of 16S rRNA and particulate methane monooxygenase.

    PubMed

    Elsaied, Hosam Easa; Hayashi, Toru; Naganuma, Takeshi

    2004-01-01

    Molecular diversity of deep-sea hydrothermal vent aerobic methanotrophs was studied using both 16S ribosomalDNA and pmoA encoding the subunit A of particulate methane monooxygenase (pMOA). Hydrothermal vent plume and chimney samples were collected from back-arc vent at Mid-Okinawa Trough (MOT), Japan, and the Trans-Atlantic Geotraverse (TAG) site along Mid-Atlantic Ridge, respectively. The target genes were amplified by polymerase chain reaction from the bulk DNA using specific primers and cloned. Fifty clones from each clone library were directly sequenced. The 16S rDNA sequences were grouped into 3 operational taxonomic units (OTUs), 2 from MOT and 1 from TAG. Two OTUs (1 MOT and 1 TAG) were located within the branch of type I methanotrophic ?-Proteobacteria. Another MOT OTU formed a unique phylogenetic lineage related to type I methanotrophs. Direct sequencing of 50 clones each from the MOT and TAG samples yielded 17 and 4 operational pmoA units (OPUs), respectively. The phylogenetic tree based on the pMOA amino acid sequences deduced from OPUs formed diverse phylogenetic lineages within the branch of type I methanotrophs, except for the OPU MOT-pmoA-8 related to type X methanotrophs. The deduced pMOA topologies were similar to those of all known pMOA, which may suggest that the pmoA gene is conserved through evolution. Neither the 16S rDNA nor pmoA molecular analysis could detect type II methanotrophs, which suggests the absence of type II methanotrophs in the collected vent samples.

  15. Thermal conductivity measurements in Porous mixtures of methane hydrate and quartz sand

    USGS Publications Warehouse

    Waite, W.F.; deMartin, B.J.; Kirby, S.H.; Pinkston, J.; Ruppel, C.D.

    2002-01-01

    Using von Herzen and Maxwell's needle probe method, we measured thermal conductivity in four porous mixtures of quartz sand and methane gas hydrate, with hydrate composing 0, 33, 67 and 100% of the solid volume. Thermal conductivities were measured at a constant methane pore pressure of 24.8 MPa between -20 and +15??C, and at a constant temperature of -10??C between 3.5 and 27.6 MPa methane pore pressure. Thermal conductivity decreased with increasing temperature and increased with increasing methane pore pressure. Both dependencies weakened with increasing hydrate content. Despite the high thermal conductivity of quartz relative to methane hydrate, the largest thermal conductivity was measured in the mixture containing 33% hydrate rather than in hydrate-free sand. This suggests gas hydrate enhanced grain-to-grain heat transfer, perhaps due to intergranular contact growth during hydrate synthesis. These results for gas-filled porous mixtures can help constrain thermal conductivity estimates in porous, gas hydrate-bearing systems.

  16. Numerical investigations of the fluid flows at deep oceanic and arctic permafrost-associated gas hydrate deposits

    NASA Astrophysics Data System (ADS)

    Frederick, Jennifer Mary

    older than the host sediment. Old pore fluid age may reflect complex flow patterns, such a fluid focusing, which can cause significant lateral migration as well as regions where downward flow reverses direction and returns toward the seafloor. Longer pathlines can produce pore fluid ages much older than that expected with a one-dimensional compaction model. For steady-state models with geometry representative of Blake Ridge (USA), a well-studied hydrate province, pore fluid ages beneath regions of topography and within fractured zones can be up to 70 Ma old. Results suggest that the measurements of 129-I/127-I reflect a mixture of new and old pore fluid. However, old pore fluid need not originate at great depths. Methane within pore fluids can travel laterally several kilometers, implying an extensive source region around the deposit. Iodine age measurements support the existence of fluid focusing beneath regions of seafloor topography at Blake Ridge, and suggest that the methane source at Blake Ridge is likely shallow. The response of methane hydrate reservoirs to warming is poorly understood. The great depths may protect deep oceanic hydrates from climate change for the time being because transfer of heat by conduction is slow, but warming will eventually be felt albeit in the far future. On the other hand, unique permafrost-associated methane hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Arctic hydrates are thought to be a relict of cold glacial periods, aggrading when sea levels are much lower and shelf sediments are exposed to freezing air temperatures. During interglacial periods, rising sea levels flood the shelf, bringing dramatic warming to the permafrost- and hydrate-bearing sediments. Permafrost-associated methane hydrate deposits have been responding to warming since the last glacial maximum ~18 kaBP as a consequence of these natural glacial cycles. This `experiment,' set into motion by nature itself

  17. Methane cycling. Nonequilibrium clumped isotope signals in microbial methane.

    PubMed

    Wang, David T; Gruen, Danielle S; Lollar, Barbara Sherwood; Hinrichs, Kai-Uwe; Stewart, Lucy C; Holden, James F; Hristov, Alexander N; Pohlman, John W; Morrill, Penny L; Könneke, Martin; Delwiche, Kyle B; Reeves, Eoghan P; Sutcliffe, Chelsea N; Ritter, Daniel J; Seewald, Jeffrey S; McIntosh, Jennifer C; Hemond, Harold F; Kubo, Michael D; Cardace, Dawn; Hoehler, Tori M; Ono, Shuhei

    2015-04-24

    Methane is a key component in the global carbon cycle, with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply substituted "clumped" isotopologues (for example, (13)CH3D) has recently emerged as a proxy for determining methane-formation temperatures. However, the effect of biological processes on methane's clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on (13)CH3D abundances and results in anomalously elevated formation-temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters. PMID:25745067

  18. Developmental geology of coalbed methane from shallow to deep in Rocky Mountain basins and in Cook Inlet-Matanuska Basin, Alaska, USA and Canada

    USGS Publications Warehouse

    Johnson, R.C.; Flores, R.M.

    1998-01-01

    The Rocky Mountain basins of western North America contain vast deposits of coal of Cretaceous through early Tertiary age. Coalbed methane is produced in Rocky Mountain basins at depths ranging from 45 m (150 ft) to 1981 m (6500 ft) from coal of lignite to low-volatile bituminous rank. Although some production has been established in almost all Rocky Mountain basins, commercial production occurs in only a few. despite more than two decades of exploration for coalbed methane in the Rocky Mountain region, it is still difficult to predict production characteristics of coalbed methane wells prior to drilling. Commonly cited problems include low permeabilities, high water production, and coals that are significantly undersaturated with respect to methane. Sources of coalbed gases can be early biogenic, formed during the early stages of coalification, thermogenic, formed during the main stages of coalification, or late stage biogenic, formed as a result of the reintroduction of methane-gnerating bacteria by groundwater after uplift and erosion. Examples of all three types of coalbed gases, and combinations of more than one type, can be found in the Rocky Mountain region. Coals in the Rocky Mountain region achieved their present ranks largely as a result of burial beneath sediments that accumulated during the Laramide orogeny (Late Cretaceous through the end of the eocene) or shortly after. Thermal events since the end of the orogeny have also locally elevated coal ranks. Coal beds in the upper part of high-volatile A bituminous rank or greater commonly occur within much more extensive basin-centered gas deposits which cover large areas of the deeper parts of most Rocky Mountain basins. Within these basin-centered deposits all lithologies, including coals, sandstones, and shales, are gas saturated, and very little water is produced. The interbedded coals and carbonaceous shales are probably the source of much of this gas. Basin-centered gas deposits become overpressured

  19. Simultaneous determination of thermal conductivity, thermal diffusivity and specific heat in sI methane hydrate

    USGS Publications Warehouse

    Waite, W.F.; Stern, L.A.; Kirby, S.H.; Winters, W.J.; Mason, D.H.

    2007-01-01

    Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between −20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.

  20. Formation mechanism of authigenic gypsum in marine methane hydrate settings: Evidence from the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Lin, Qi; Wang, Jiasheng; Algeo, Thomas J.; Su, Pibo; Hu, Gaowei

    2016-09-01

    During the last decade, gypsum has been discovered widely in marine methane hydrate-bearing sediments. However, whether this gypsum is an in-situ authigenic precipitate remains controversial. The GMGS2 expedition carried out in 2013 by the Guangzhou Marine Geological Survey (GMGS) in the northern South China Sea provided an excellent opportunity for investigating the formation of authigenic minerals and, in particular, the relationship between gypsum and methane hydrate. In this contribution, we analyzed the morphology and sulfur isotope composition of gypsum and authigenic pyrite as well as the carbon and oxygen isotopic compositions of authigenic carbonate in a drillcore from Site GMGS2-08. These methane-derived carbonates have characteristic carbon and oxygen isotopic compositions (δ13C: -57.9‰ to -27.3‰ VPDB; δ18O: +1.0‰ to +3.8‰ VPDB) related to upward seepage of methane following dissociation of underlying methane hydrates since the Late Pleistocene. Our data suggest that gypsum in the sulfate-methane transition zone (SMTZ) of this core precipitated as in-situ authigenic mineral. Based on its sulfur isotopic composition, the gypsum sulfur is a mixture of sulfate derived from seawater and from partial oxidation of authigenic pyrite. Porewater Ca2+ ions for authigenic gypsum were likely generated from carbonate dissolution through acidification produced by oxidation of authigenic pyrite and ion exclusion during methane hydrate formation. This study thus links the formation mechanism of authigenic gypsum with the oxidation of authigenic pyrite and evolution of underlying methane hydrates. These findings suggest that authigenic gypsum may be a useful proxy for recognition of SMTZs and methane hydrate zones in modern and ancient marine methane hydrate geo-systems.

  1. Gas hydrates in the deep water Ulleung Basin, East Sea, Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae

    2016-04-01

    Studies on gas hydrates in the deep-water Ulleung Basin, East Sea, Korea was initiated by the Korea Institute of Geoscience and Mineral Resources (KIGAM) to secure the future energy resources in 1996. Bottom simulating reflectors (BSRs) were first identified on seismic data collected in the southwestern part of the basin from 1998 to 1999. Regional geophysical surveys and geological studies of gas hydrates in the basin have been carried out by KIGAM from 2000 to 2004. The work included 12,367 km of 2D multi-channel seismic reflection lines and 38 piston cores 5 to 8 m long. As a part of the Korean National Gas Hydrate Program that has been performed since 2005, 6690 km of 2D multi-channel reflection seismic lines, 900 km2 of 3D seismic data, 69 piston cores and three PROD cores were additionally collected. In addition, two gas hydrate drilling expeditions were performed in 2007 and 2010. Cracks generally parallel to beddings caused by the dissociation of gas hydrate were often observed in cores. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data showed clear and wide-spread bottom-simulating reflectors (BSRs). The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone. Several vertical to sub-vertical chimney-like blank zones up to several kilometers in diameter were also identified in the study area. They are often associated with velocity pull-up structures that are interpreted due to higher velocity in gas hydrate-bearing deposits. Seismic velocity analysis also showed a high velocity anomaly within the pull-up structure. Gas hydrate samples were collected from the shallow sedimentary section of blanking zone by piston coring in 2007. BSRs mainly occur in the southern part of the basin. They also locally observed in the

  2. IN-SITU SAMPLING AND CHARACTERIZATION OF NATURALLY OCCURRING MARINE METHANE HYDRATE USING THE D/V JOIDES RESOLUTION

    SciTech Connect

    Frank R. Rack; Peter Schultheiss; Melanie Holland

    2005-01-01

    The primary accomplishments of the JOI Cooperative Agreement with DOE/NETL in this quarter were that: (1) follow-up logging of pressure cores containing hydrate-bearing sediment; and (2) opening of some of these cores to establish ground-truth understanding. The follow-up measurements made on pressure cores in storage are part of a hydrate geriatric study related to ODP Leg 204. These activities are described in detail in Appendices A and B of this report. Work also continued on developing plans for Phase 2 of this cooperative agreement based on evolving plans to schedule a scientific ocean drilling expedition to study marine methane hydrates along the Cascadia margin, in the NE Pacific as part of the Integrated Ocean Drilling Program (IODP) using the R/V JOIDES Resolution.

  3. Methane conversion

    SciTech Connect

    Jones, C.A.; Leonard, J.J.; Sofranko, J.A.

    1984-04-17

    Another version of Arco's process for reforming methane or natural gas into a synthesis gas uses bismuth oxide as the reforming agent; it also requires no nickel or noble metal catalyst. The methane-containing gas contacts bismuth oxide at temperatures of 900/sup 0/-1560/sup 0/F. The oxide is reduced by methane and easily regenerated with an oxygen-containing gas. The oxide Bi/sub 2/O/sub 3/ is a particularly effective synthesizing agent.

  4. Evolution of a spherical hydrate-free inclusion in a porous matrix filled with methane hydrate.

    PubMed

    Tsiberkin, Kirill; Lyubimov, Dmitry V; Lyubimova, Tatyana P; Zikanov, Oleg

    2014-02-01

    The behavior of a small isolated hydrate-free inclusion (a gas bubble) within a porous matrix filled with methane hydrate and either water or methane gas is analyzed. Simplifying assumptions of spherical symmetry, an infinite uniform porous medium, and negligible effects of background temperature and pressure variations focus the investigation on the features of the dynamics of a single bubble determined by a phase transition. Two solutions are presented: an exact solution of the Stefan problem obtained when the effects of gas and water flow are neglected, and a numerical solution of the full problem. The solutions are in good agreement with each other and with known asymptotic dependencies, confirming that the effects of inertia and convection transport can be neglected in the case of small inclusions. It is found that, after an initial adjustment, the radius of any small bubble decreases with time following a self-similar solution of the Stefan problem. The lifetime of a bubble is evaluated as a function of initial radius and the system's physical parameters. Possible effects of such inclusions on the filtration of methane to the surface and other aspects of the dynamics of hydrate-bearing deposits are discussed. PMID:25353572

  5. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M; Roberts, Jeffery J.

    2015-01-01

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  6. Sinking methane.

    PubMed

    Reay, David S

    2003-02-01

    Concentrations of the powerful greenhouse gas, methane, in our atmosphere have doubled since the beginning of the industrial age. Reducing these levels is a vital part of global efforts to combat global warming. Could we make use of the Earth's own methane sinks?

  7. Deep oxidation of methane on particles derived from YSZ-supported Pd-Pt-(O) coatings synthesized by pulsed filtered cathodic arc

    SciTech Connect

    Horwat, D.; Endrino, J.L.; Boreave, A.; Karoum,R.; Pierson, J.F.; Weber, S.; Anders, A.; Vernoux, Ph.

    2008-12-12

    Methane conversion tests were performed on Pd, PdOy, Pd0.6Pt0.4Oy and Pd0.4Pt0.6Oy thin films deposited on yttria stabilized zirconia (YSZ) substrates. Pt containing films exhibited poor activity and high reducibility. As-deposited Pd and PdOy films showed good activity and transformed, during the cycling process, to particles dispersed on the YSZ substrates. The higher reaction rate of initially PdOy films was explained by a better dispersion of the catalyst. A drop of the reaction rate was observed when the temperature exceeded 735oC and 725oC for initially Pd and PdOy, respectively, which can be associated with the high-temperature reduction of PdO into Pd.

  8. Breaking methane

    PubMed Central

    Rosenzweig, Amy C.

    2015-01-01

    The most powerful oxidant found in nature is compound Q, an enzymatic intermediate that oxidizes methane. New spectroscopic data have resolved the long-running controversy about Q’s chemical structure. PMID:25607367

  9. Development and evaluation of technology for methane production from a deep coal seam in the Piceance Basin. Annual report, June 1, 1985-May 31, 1986

    SciTech Connect

    Schwoebel, J.J.; Logan, T.L.; Decker, A.D.; Cooper, J.D.

    1986-09-01

    The Red Mountain Site, leased and operated by Resource Enterprises, Inc. is the focus of a six-year, multi-well project with a main objective to develop, improve, evaluate and communicate the technology required to produce gas from deeply buried coal. To understand the parameters controlling coalbed gas production, project efforts are focused on a single coal reservoir (the Cameo Coal 'D' Seam) at the test site. Last year, 1 Deep Seam was stimulated with a nitrogen foam fracture. Post-stimulation stabilized gas production is approximately 20 Mcfd, accompanied by water production of 1 Bpd. Extensive pre-frac testing was performed on 2 Deep Seam including step-rate tests, pump-in/flow-back tests, and a 20,000 gallon mini-frac. The well was successfully fracture stimulated with approximately 122,00 gallons of 40-lb linear gel and 260,000 lbs of 20/40 mesh sand. The well stimulation was designed to selectively place the proppant in the D coal seam. Post-stimulation gas production reached over 100 Mcfd; however, it has declined to 40 Mcfd at present. A horizontal drainhole will be attempted in 3 Deep Seam. The overall objective is to test and evaluate the effectiveness of drainhole completion technology in a coal reservoir.

  10. Powering up the ``biogeochemical engine'': The impact of exceptional ventilation of a deep meromictic lake on the lacustrine redox, nutrient, and methane balances

    NASA Astrophysics Data System (ADS)

    Lehmann, Moritz; Simona, Marco; Wyss, Silvia; Blees, Jan; Frame, Caitlin; Niemann, Helge; Veronesi, Mauro; Zopfi, Jakob

    2015-08-01

    The Lake Lugano North Basin has been meromictic for several decades, with anoxic waters below 100m depth. Two consecutive cold winters in 2005 and 2006 induced exceptional deep mixing, leading to a transient oxygenation of the whole water column. With the ventilation of deep waters and the oxidation of large quantities of reduced solutes, the lake's total redox-balance turned positive, and the overall hypolimnetic oxygen demand of the lake strongly decreased. The disappearance of 150 t dissolved phosphorous (P) during the first ventilation in March 2005 is attributed to the scavenging of water-column-borne P by newly formed metal oxyhydroxides and the temporary transfer to the sediments. The fixed nitrogen (N) inventory was reduced by ~30% (~1000 t). The water-column turnover induced the nitratation of the previously NO3--free deep hypolimnion by oxidation of large amounts of legacy NH4+ and by mixing with NO3--rich subsurface water masses. Sediments with a strong denitrifying potential, but NO3--starved for decades, were brought in contact with NO3--replete waters, invigorating benthic denitrification and rapid fixed N loss from the lake in spite of the overall more oxygenated conditions. Similarly, a large microbial aerobic CH4 oxidation (MOx) potential in the hypolimnion was capitalized with the ventilation of the deep basin. Almost all CH4, which had been built up over more than 40 years (~2800 t), was removed from the water column within 30 days. However, boosted MOx could only partly explain the disappearance of the CH4. The dominant fraction (75%) of the CH4 evaded to the atmosphere, through storage flux upon exposure of anoxic CH4-rich water to the atmosphere. As of today, the North Basin seems far from homeostasis regarding its fixed N and CH4 budgets, and the deep basin's CH4 pool is recharging at a net production rate of ~66 t y-1. The size of impending CH4 outbursts will depend on the frequency and intensity of exceptional mixing events in the future.

  11. Emerging topics in marine methane biogeochemistry.

    PubMed

    Valentine, David L

    2011-01-01

    Our knowledge of physical, chemical, geological and biological processes affecting methane in the ocean and in underlying sediments is expanding at a rapid pace. On first inspection, marine methane biogeochemistry appears simple: Methane distribution in sediment is set by the deposition pattern of organic material, and the balance of sources and sinks keeps its concentration low in most waters. However, recent research reveals that methane is affected by complex biogeochemical processes whose interactions are understood only at a superficial level. Such processes span the deep-subsurface, near subsurface, and ocean waters, and relate primarily to the production, consumption, and transport of methane. The purpose of this synthesis is to examine select processes within the framework of methane biogeochemistry, to formulate hypotheses on how they might operate and interact with one another, and to consider their controls. PMID:21329202

  12. Uncorking the bottle: What triggered the Paleocene/Eocene thermal maximum methane release?

    NASA Astrophysics Data System (ADS)

    Katz, Miriam E.; Cramer, Benjamin S.; Mountain, Gregory S.; Katz, Samuel; Miller, Kenneth G.

    2001-12-01

    The Paleocene/Eocene thermal maximum (PETM) was a time of rapid global warming in both marine and continental realms that has been attributed to a massive methane (CH4) release from marine gas hydrate reservoirs. Previously proposed mechanisms for this methane release rely on a change in deepwater source region(s) to increase water temperatures rapidly enough to trigger the massive thermal dissociation of gas hydrate reservoirs beneath the seafloor. To establish constraints on thermal dissociation, we model heat flow through the sediment column and show the effect of the temperature change on the gas hydrate stability zone through time. In addition, we provide seismic evidence tied to borehole data for methane release along portions of the U.S. continental slope; the release sites are proximal to a buried Mesozoic reef front. Our model results, release site locations, published isotopic records, and ocean circulation models neither confirm nor refute thermal dissociation as the trigger for the PETM methane release. In the absence of definitive evidence to confirm thermal dissociation, we investigate an alternative hypothesis in which continental slope failure resulted in a catastrophic methane release. Seismic and isotopic evidence indicates that Antarctic source deepwater circulation and seafloor erosion caused slope retreat along the western margins of the North Atlantic in the late Paleocene. Continued erosion or seismic activity along the oversteepened continental margin may have allowed methane to escape from gas reservoirs trapped between the frozen hydrate-bearing sediments and the underlying buried Mesozoic reef front, precipitating the Paleocene/Eocene boundary methane release. An important implication of this scenario is that the methane release caused (rather than resulted from) the transient temperature increase of the PETM. Neither thermal dissociation nor mechanical disruption of sediments can be identified unequivocally as the triggering mechanism

  13. Characterization of methane hydrate host sediments using synchrotron-computed microtomography (CMT)

    USGS Publications Warehouse

    Jones, K.W.; Feng, H.; Tomov, S.; Winters, W.J.; Prodanovic, M.; Mahajan, D.

    2007-01-01

    The hydrate-sediment interaction is an important aspect of gas hydrate studies that needs further examination. We describe here the applicability of the computed microtomography (CMT) technique that utilizes an intense X-ray synchrotron source to characterize sediment samples, two at various depths from the Blake Ridge area (a well-known hydrate-prone region) and one from Georges Bank, that once contained methane trapped as hydrates. Detailed results of the tomographic analysis performed on the deepest sample (667??m) from Blake Ridge are presented as 2-D and 3-D images which show several mineral constituents, the internal grain/pore microstructure, and, following segmentation into pore and grain space, a visualization of the connecting pathways through the pore-space of the sediment. Various parameters obtained from the analysis of the CMT data are presented for all three sediment samples. The micro-scale porosity values showed decreasing trend with increasing depth for all three samples that is consistent with the previously reported bulk porosity data. The 3-D morphology, pore-space pathways, porosity, and permeability values are also reported for all three samples. The application of CMT is now being expanded to the laboratory-formed samples of hydrate in sediments as well as field samples of methane hydrate bearing sediments.

  14. Electrical properties of methane hydrate + sediment mixtures: The σ of CH4 Hydrate + Sediment

    SciTech Connect

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M.; Roberts, Jeffery J.

    2015-07-30

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  15. Methane ocean on Titan?

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    There was an impressive list of names on a recent scientific communication that argues for the existence on Titan of an ocean of liquid methane (CH4) perhaps several hundred meters deep. C. Sagan and S. Dermott with helpful comments by S. Oter, S. Ostro, S. Peale, C. Yoder, W. Thompson, S. Squyres, G. Pettengill, P. Gierasch, and B. Khare speculate that such a methanic ocean, with its Saturnian tides and its tholinian floor, should exist all over Titan's surface; it should unless, they conclude, there is the ‘distracting coincidence [that] … the position of the surface of Titan [is] … near the liquidus in the CH4phase diagram [and, consequently, there is] …almost no methane ocean at all’ (Nature, 300, 731, 1982).We know very little about Titan and its surface; the way of checking into Sagan and Dermott's ideas appears to rest on the interpretation of radar reflectivity data. Preliminary attempts to obtain radar data were made in 1979 with the 305-m Arecibo telescope, but only broad limits resulted. The next opportunity for a measurement at Arecibo comes in the 1990's. Of course, the ideal circumstance would be to send spacecraft equipped with a radar reflectometer for a Titan flyby.

  16. Nonequilibrium clumped isotope signals in microbial methane

    NASA Astrophysics Data System (ADS)

    Wang, David T.; Gruen, Danielle S.; Lollar, Barbara Sherwood; Hinrichs, Kai-Uwe; Stewart, Lucy C.; Holden, James F.; Hristov, Alexander N.; Pohlman, John W.; Morrill, Penny L.; Könneke, Martin; Delwiche, Kyle B.; Reeves, Eoghan P.; Sutcliffe, Chelsea N.; Ritter, Daniel J.; Seewald, Jeffrey S.; McIntosh, Jennifer C.; Hemond, Harold F.; Kubo, Michael D.; Cardace, Dawn; Hoehler, Tori M.; Ono, Shuhei

    2015-04-01

    Methane is a key component in the global carbon cycle, with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply substituted “clumped” isotopologues (for example, 13CH3D) has recently emerged as a proxy for determining methane-formation temperatures. However, the effect of biological processes on methane’s clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on 13CH3D abundances and results in anomalously elevated formation-temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters.

  17. Nonequilibrium clumped isotope signals in microbial methane

    USGS Publications Warehouse

    Wang, David T.; Gruen, Danielle S.; Lollar, Barbara Sherwood; Hinrichs, Kai-Uwe; Stewart, Lucy C.; Holden, James F.; Hristov, Alexander N.; Pohlman, John W.; Morrill, Penny L.; Könneke, Martin; Delwiche, Kyle B.; Reeves, Eoghan P.; Sutcliffe, Chelsea N.; Ritter, Daniel J.; Seewald, Jeffrey S.; McIntosh, Jennifer C.; Hemond, Harold F.; Kubo, Michael D.; Cardace, Dawn; Hoehler, Tori M.; Ono, Shuhei

    2015-01-01

    Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological processes on methane’s clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on 13CH3D abundances and results in anomalously elevated formation temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters.

  18. Time-series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon

    NASA Astrophysics Data System (ADS)

    Philip, Brendan T.; Denny, Alden R.; Solomon, Evan A.; Kelley, Deborah S.

    2016-03-01

    An estimated 500-2500 gigatons of methane carbon is sequestered in gas hydrate at continental margins and some of these deposits are associated with overlying methane seeps. To constrain the impact that seeps have on methane concentrations in overlying ocean waters and to characterize the bubble plumes that transport methane vertically into the ocean, water samples and time-series acoustic images were collected above Southern Hydrate Ridge (SHR), a well-studied hydrate-bearing seep site ˜90 km west of Newport, Oregon. These data were coregistered with robotic vehicle observations to determine the origin of the seeps, the plume rise heights above the seafloor, and the temporal variability in bubble emissions. Results show that the locations of seep activity and bubble release remained unchanged over the 3 year time-series investigation, however, the magnitude of gas release was highly variable on hourly time scales. Bubble plumes were detected to depths of 320-620 m below sea level (mbsl), in several cases exceeding the upper limit of hydrate stability by ˜190 m. For the first time, sustained gas release was imaged at the Pinnacle site and in-between the Pinnacle and the Summit area of venting, indicating that the subseafloor transport of fluid and gas is not restricted to the Summit at SHR, requiring a revision of fluid-flow models. Dissolved methane concentrations above background levels from 100 to 300 mbsl are consistent with long-term seep gas transport into the upper water column, which may lead to the build-up of seep-derived carbon in regional subsurface waters and to increases in associated biological activity.

  19. Coal-bed methane resources in Arkoma basin, southeastern Oklahoma

    SciTech Connect

    Friedman, S.A. )

    1989-08-01

    A major federal tax incentive for unconventional gas production has interested entrepreneurs, geologists, and engineers in the occurrence and distribution of coal-bed methane resources in the Arkoma basin. Because the methane is trapped in coal beds, geology of the coal resources also has received renewed attention. The Arkoma basin contains most of the coal-bed methane resources in Oklahoma: 76% of the 7.9 billion short tons of the remaining, identified Middle Pennsylvanian coal resources of the state. This paper briefly reviews previous estimates of coal-bed methane resources in Oklahoma and presents an updated estimate for Haskell and LeFlore Counties and a new estimate for Latimer County. Rieke and Kirr indicated that 2.8 tcf of coal-bed methane is present in 10 coals in eight Oklahoma counties of the Arkoma basin, 500-3,000 ft deep. Iannacchione and Puglio estimated that a maximum of 1.5 tcf of coal-bed methane occurs in the Hartshorne coals in Haskell and LeFlore Counties from 500-3,000 ft deep. The present investigation shows that the Hartshorne and 11 other coals contain at least 1.8 tcf of coal-bed methane resources, based on identified coal resources 500-3,000 ft deep in Haskell, Latimer, and LeFlore Counties. An additional 1.2 tcf of coal-bed methane resources occur in the Hartshorne and four other coals from 3,000-7,000 ft deep, based on assumed stratigraphic and thickness continuity. Thus, a revised estimate indicates that Haskell, Latimer, and LeFlore Counties alone contain about 3 tcf of coal-bed methane resources in 12 coal beds from 500-7,000 ft deep. Undoubtedly additional coal-bed methane resources are present in the westernmost part of the Arkoma basin.

  20. Drilling and data acquisition programs for the methane hydrate offshore production test in the Eastern Nankai Trough

    NASA Astrophysics Data System (ADS)

    Yamamoto, K.; Fujii, T.

    2013-12-01

    Marine methane hydrates are a matter of scientific interests from various viewpoints such as a key player of global carbon cycle, effects on climate change, cause of seafloor instability, and a possible future energy resource. Under the Japanese national research program, the MH21 research consortium (Japan Oil, Gas and Metals National Corporation and National Institute of Advanced Industrial Science and Technology) has conducted survey operations and subsequent analyses of data and samples from methane hydrate-bearing sediments in the Eastern Nankai Trough. The goal of the project was a gas production test from a methane hydrate deposits in sandy intervals of Pleistocene turbidite sediments. The test location was set in Daini Atsumi Knoll that is a ridge between forearc basin and accretionary prism, and the sediments cover the flank of the knoll. The water depth at the test location is approximately 1000m, and 50m thick methane hydrate concentrated zone exists around 300m below seafloor. The main interest of the MH21 research team is to know physical (thermal, hydraulic, and mechanical) parameters of sediments that are necessary to understand gas hydrate dissociation processes during the production test. Core samples and geophysical logging data obtained during past surveys are utilized for this purpose. Sedimentation and tectono-geophysical conditions govern such material properties, so the samples were analyzed from those viewpoints, too. The first drilling at the location was done in 2004 with logging and coring operation including pressure-conserved core sampling. In 2011, shallow geotechnical survey holes were drilled in the area for geo-hazard assessment, and core samples were taken in the holes, along with some in-situ mechanical and hydraulic testings. In early 2012, a well construction operation for the gas production test was conducted with logging operations that contains neutron porosity data using pulse-neutron devices, magnetic resonance log, etc. A

  1. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    SciTech Connect

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    part of the Ugnu and throughout the West Sak. No hydrate-bearing zones were identified either in recovered core or on well logs. The base of the permafrost was found at about 1260 ft. With the exception of the deepest sands in the West Sak and some anomalous thin, tight zones, all sands recovered (after thawing) are unconsolidated with high porosity and high permeability. At 800 psi, Ugnu sands have an average porosity of 39.3% and geometrical mean permeability of 3.7 Darcys. Average grain density is 2.64 g/cc. West Sak sands have an average porosity of 35.5%, geometrical mean permeability of 0.3 Darcys, and average grain density of 2.70 g/cc. There were several 1-2 ft intervals of carbonate-cemented sandstone recovered from the West Sak. These intervals have porosities of only a few percent and very low permeability. On a well log they appear as resistive with a high sonic velocity. In shallow sections of other wells these usually are the only logs available. Given the presence of gas in Hot Ice No. 1, if only resistivity and sonic logs and a mud log had been available, tight sand zones may have been interpreted as containing hydrates. Although this finding does not imply that all previously mapped hydrate zones are merely tight sands, it does add a note of caution to the practice of interpreting the presence of hydrates from old well information. The methane hydrate stability zone below the Hot Ice No. 1 location includes thick sections of sandstone and conglomerate which would make excellent reservoir rocks for hydrates and below the permafrost zone shallow gas. The Ugnu formation comprises a more sand-rich section than does the West Sak formation, and the Ugnu sands when cleaned and dried are slightly more porous and significantly more permeable than the West Sak.

  2. Methane hydrate formation in turbidite sediments of northern Cascadia, IODP Expedition 311

    USGS Publications Warehouse

    Torres, M.E.; Trehu, A.M.; Cespedes, N.; Kastner, M.; Wortmann, U.G.; Kim, J.-H.; Long, P.; Malinverno, A.; Pohlman, J.W.; Riedel, M.; Collett, T.

    2008-01-01

    Expedition 311 of the Integrated Ocean Drilling Program (IODP) to northern Cascadia recovered gas-hydrate bearing sediments along a SW-NE transect from the first ridge of the accretionary margin to the eastward limit of gas-hydrate stability. In this study we contrast the gas gas-hydrate distribution from two sites drilled ~ 8??km apart in different tectonic settings. At Site U1325, drilled on a depositional basin with nearly horizontal sedimentary sequences, the gas-hydrate distribution shows a trend of increasing saturation toward the base of gas-hydrate stability, consistent with several model simulations in the literature. Site U1326 was drilled on an uplifted ridge characterized by faulting, which has likely experienced some mass wasting events. Here the gas hydrate does not show a clear depth-distribution trend, the highest gas-hydrate saturation occurs well within the gas-hydrate stability zone at the shallow depth of ~ 49??mbsf. Sediments at both sites are characterized by abundant coarse-grained (sand) layers up to 23??cm in thickness, and are interspaced within fine-grained (clay and silty clay) detrital sediments. The gas-hydrate distribution is punctuated by localized depth intervals of high gas-hydrate saturation, which preferentially occur in the coarse-grained horizons and occupy up to 60% of the pore space at Site U1325 and > 80% at Site U1326. Detailed analyses of contiguous samples of different lithologies show that when enough methane is present, about 90% of the variance in gas-hydrate saturation can be explained by the sand (> 63????m) content of the sediments. The variability in gas-hydrate occupancy of sandy horizons at Site U1326 reflects an insufficient methane supply to the sediment section between 190 and 245??mbsf. ?? 2008 Elsevier B.V.

  3. Methane hydrate formation in turbidite sediments of northern Cascadia IODP Expedition 311

    SciTech Connect

    Torres, M. E.; Trehu, Ann M.; cespedes, N.; Kastner, Miriam; Wortmann, Ulrich; Kim, J.; Long, Philip E.; Malinverno, Alberto; Pohlman, J. W.; Collett, T. S.

    2008-07-15

    Expedition 311 of the Integrated Ocean Drilling Program (IODP) to northern Cascadia recovered gas-hydrate bearing sediments along a SW–NE transect from the first ridge of the accretionary margin to the eastward limit of gas-hydrate stability. In this study we contrast the gas gas-hydrate distribution from two sites drilled ~8 km apart in different tectonic settings. At Site U1325, drilled on a depositional basin with nearly horizontal sedimentary sequences, the gas-hydrate distribution shows a trend of increasing saturation toward the base of gas-hydrate stability, consistent with several model simulations in the literature. Site U1326 was drilled on an uplifted ridge characterized by faulting, which has likely experienced some mass wasting events. Here the gas hydrate does not show a clear depth-distribution trend, the highest gas-hydrate saturation occurs well within the gas-hydrate stability zone at the shallow depth of ~49 mbsf. Sediments at both sites are characterized by abundant coarse-grained (sand) layers up to 23 cm in thickness, and are interspaced within fine-grained (clay and silty clay) detrital sediments. The gas-hydrate distribution is punctuated by localized depth intervals of high gas-hydrate saturation, which preferentially occur in the coarse-grained horizons and occupy up to 60% of the pore space at Site U1325 and N80% at Site U1326. Detailed analyses of contiguous samples of different lithologies show that when enough methane is present, about 90% of the variance in gas-hydrate saturation can be explained by the sand (N63 μm) content of the sediments. The variability in gas-hydrate occupancy of sandy horizons at Site U1326 reflects an insufficient methane supply to the sediment section between 190 and 245 mbsf.

  4. Methane Plumes on Mars

    NASA Video Gallery

    Spectrometer instruments attached to several telescopes detect plumes of methane emitted from Mars during its summer and spring seasons. High levels of methane are indicated by warmer colors. The m...

  5. Up with methane

    SciTech Connect

    Barlaz, M.A.; Milke, M.W.; Ham, R.K.

    1986-12-01

    Methane production from municipal refuse represents a rapidly developing source of energy which remains underutilized. Part of the problem is the small amount of methane which is typically collected relative to the refuse's methane generation potential. This study was undertaken to define the parameters which affect the onset of methane production and methane yields in sanitary landfills. Ultimately, we need to develop refuse disposal methods which enhance its methane production potential. Included in the study were tests of how introduction of old refuse, use of sterile cover soil, addition of acetate to refuse, and use of leachate, recycling and neutralization affect methane generation. A more thorough understanding of how the microbes present in refuse react to different variables is the first step in the development of techniques for stimulating methane production in sanitary landfills.

  6. Aerobic methane production in surface waters of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Finke, N.; Crespo-Medina, M.; Schweers, J.; Joye, S. B.

    2011-12-01

    Near surface water of the global oceans often show elevated methane concentrations compared to the water column below with concentrations in supersaturation in regard to the atmosphere (Lamontagne et al. 1973), resulting in a source of this potent greenhouse gas to the atmosphere. The mechanisms leading to methane supersaturation in surface waters remains unclear. Incubations with Trichodesmium-containing Pacific surface water suggested methylphosphonate as potential methane precursor under phosphate limiting conditions (Karl et al. 2008), whereas in phosphate rich Arctic surface waters, DMSP addition stimulated methane production (Damm et al. 2010). Surface waters of the Gulf of Mexico typically exhibit a methane maximum that is conincident with the deep chlorophyll maximum, below the depths where Trichodesmium is abundant. Addition of methylphosphonate, dimethylsulfoniopropionate (DMSP) or methane thiol (MeSH), the proposed methane precursor in DMSP conversion to methane, to oxic sea water did not affect methane production within the chlorophyll maximum at most stations, whereas methyl phosphonate addition stimulated methane production in the surface water and proposed deep Trichodesmium horizon. Pre-filtration of the water through a 10 μm sieve, which eliminated Trichodesmium, or through a 1.2 μm filter, which eliminated additional cyanobacteria such as Synechococcus, did not reduce methane production. Under dark oxic and dark anoxic conditions, however, methane production was reduced 5 and 7-20 fold, respectively, indicating that anerobic methane production in anoxic microniches is not responsible for the methane production. The reduction of methane production under dark conditions suggests that methane production is, in some yet unrecognized way, linked to phototrophic metabolism. Cyanobacteria are likely not responsible for the observed aerobic methane production in the surface waters of the Gulf of Mexico and while methylphosphonate is a potential

  7. Heat pipe methanator

    DOEpatents

    Ranken, William A.; Kemme, Joseph E.

    1976-07-27

    A heat pipe methanator for converting coal gas to methane. Gravity return heat pipes are employed to remove the heat of reaction from the methanation promoting catalyst, transmitting a portion of this heat to an incoming gas pre-heat section and delivering the remainder to a steam generating heat exchanger.

  8. Using the Deepwater Horizon Disaster to Investigate Natural Biogeochemical Cycling Associated with Rapid Methane Emissions (Invited)

    NASA Astrophysics Data System (ADS)

    Kessler, J. D.; Valentine, D. L.; Yvon-Lewis, S. A.; Heintz, M. B.; Hu, L.; Garcia Tigreros, F.; Du, M.; Chan, E. W.

    2010-12-01

    On April 20, a violent methane discharge severed the Deepwater Horizon rig from its well and oil and gas began spilling into the deep Gulf of Mexico at depths of ca. 1.5 km simulating a natural, rapid, and short-term methane release in deepwater. Given the estimated rates of emission of total material as well as the fraction methane by weight, one can estimate that a total of 0.1 to 0.3 Tg (10^12 g) of methane were emitted from a localized area in only 83 days. Measurements of methane oxidation and sea-air methane flux were measured in June indicating that at that time, oxidation rates were slow and sea-air fluxes were relatively insignificant. A deepwater methane plume was identified and in June 2010, the depth of the methane plume was on average from 950 - 1150 m with the maximum methane concentration measured being 183 μM. Analyses of diffusion, advective mixing, and methane oxidation were used to estimate that this plume has a lifetime of years to decades with the main controlling factor being the rate of methane oxidation. The persistent nature of this deepwater methane plume allows it to be used as a natural laboratory to investigate key hypotheses concerning the biogeochemical cycling of methane and oxygen associated with rapid, short-term methane discharges.

  9. Deep subsurface microbial processes

    USGS Publications Warehouse

    Lovley, D.R.; Chapelle, F.H.

    1995-01-01

    Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed redox reactions that influence the geophysical properties of these environments. Furthermore, there is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by man's activities, and there is a need to predict the extent to which microbial activity may remediate such contamination. Metabolically active microorganisms can be recovered from a diversity of deep subsurface environments. The available evidence suggests that these microorganisms are responsible for catalyzing the oxidation of organic matter coupled to a variety of electron acceptors just as microorganisms do in surface sediments, but at much slower rates. The technical difficulties in aseptically sampling deep subsurface sediments and the fact that microbial processes in laboratory incubations of deep subsurface material often do not mimic in situ processes frequently necessitate that microbial activity in the deep subsurface be inferred through nonmicrobiological analyses of ground water. These approaches include measurements of dissolved H2, which can predict the predominant microbially catalyzed redox reactions in aquifers, as well as geochemical and groundwater flow modeling, which can be used to estimate the rates of microbial processes. Microorganisms recovered from the deep subsurface have the potential to affect the fate of toxic organics and inorganic contaminants in groundwater. Microbial activity also greatly influences 1 the chemistry of many pristine groundwaters and contributes to such phenomena as porosity development in carbonate aquifers, accumulation of undesirably high concentrations of dissolved iron, and production of methane and hydrogen sulfide. Although the last decade has seen a dramatic increase in interest in deep subsurface microbiology, in comparison with the study of

  10. Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome.

    PubMed

    Shi, Weibing; Moon, Christina D; Leahy, Sinead C; Kang, Dongwan; Froula, Jeff; Kittelmann, Sandra; Fan, Christina; Deutsch, Samuel; Gagic, Dragana; Seedorf, Henning; Kelly, William J; Atua, Renee; Sang, Carrie; Soni, Priya; Li, Dong; Pinares-Patiño, Cesar S; McEwan, John C; Janssen, Peter H; Chen, Feng; Visel, Axel; Wang, Zhong; Attwood, Graeme T; Rubin, Edward M

    2014-09-01

    Ruminant livestock represent the single largest anthropogenic source of the potent greenhouse gas methane, which is generated by methanogenic archaea residing in ruminant digestive tracts. While differences between individual animals of the same breed in the amount of methane produced have been observed, the basis for this variation remains to be elucidated. To explore the mechanistic basis of this methane production, we measured methane yields from 22 sheep, which revealed that methane yields are a reproducible, quantitative trait. Deep metagenomic and metatranscriptomic sequencing demonstrated a similar abundance of methanogens and methanogenesis pathway genes in high and low methane emitters. However, transcription of methanogenesis pathway genes was substantially increased in sheep with high methane yields. These results identify a discrete set of rumen methanogens whose methanogenesis pathway transcription profiles correlate with methane yields and provide new targets for CH4 mitigation at the levels of microbiota composition and transcriptional regulation. PMID:24907284

  11. Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome

    PubMed Central

    Moon, Christina D.; Leahy, Sinead C.; Kang, Dongwan; Froula, Jeff; Kittelmann, Sandra; Fan, Christina; Deutsch, Samuel; Gagic, Dragana; Seedorf, Henning; Kelly, William J.; Atua, Renee; Sang, Carrie; Soni, Priya; Li, Dong; Pinares-Patiño, Cesar S.; McEwan, John C.; Janssen, Peter H.; Chen, Feng; Visel, Axel; Wang, Zhong; Attwood, Graeme T.

    2014-01-01

    Ruminant livestock represent the single largest anthropogenic source of the potent greenhouse gas methane, which is generated by methanogenic archaea residing in ruminant digestive tracts. While differences between individual animals of the same breed in the amount of methane produced have been observed, the basis for this variation remains to be elucidated. To explore the mechanistic basis of this methane production, we measured methane yields from 22 sheep, which revealed that methane yields are a reproducible, quantitative trait. Deep metagenomic and metatranscriptomic sequencing demonstrated a similar abundance of methanogens and methanogenesis pathway genes in high and low methane emitters. However, transcription of methanogenesis pathway genes was substantially increased in sheep with high methane yields. These results identify a discrete set of rumen methanogens whose methanogenesis pathway transcription profiles correlate with methane yields and provide new targets for CH4 mitigation at the levels of microbiota composition and transcriptional regulation. PMID:24907284

  12. Methane photochemistry and methane production on Neptune

    NASA Astrophysics Data System (ADS)

    Romani, P. N.; Atreya, S. K.

    1988-06-01

    The Neptune stratosphere's methane photochemistry is presently studied by means of a numerical model in which the observed mixing ratio of methane prompts photolysis near the CH4 homopause. Haze generation by methane photochemistry has its basis in the formation of hydrocarbon ices and polyacetylenes; the hazes can furnish the requisite aerosol haze at the appropriate pressure levels required by observations of Neptune in the visible and near-IR. Comparisons of model predictions with Uranus data indicate a lower ratio of polyacetylene production to hydrocarbon ice, as well as a lower likelihood of UV postprocessing of the acetylene ice to polymers on Neptune, compared to Uranus.

  13. Methane photochemistry and methane production on Neptune

    NASA Technical Reports Server (NTRS)

    Romani, P. N.; Atreya, S. K.

    1988-01-01

    The Neptune stratosphere's methane photochemistry is presently studied by means of a numerical model in which the observed mixing ratio of methane prompts photolysis near the CH4 homopause. Haze generation by methane photochemistry has its basis in the formation of hydrocarbon ices and polyacetylenes; the hazes can furnish the requisite aerosol haze at the appropriate pressure levels required by observations of Neptune in the visible and near-IR. Comparisons of model predictions with Uranus data indicate a lower ratio of polyacetylene production to hydrocarbon ice, as well as a lower likelihood of UV postprocessing of the acetylene ice to polymers on Neptune, compared to Uranus.

  14. Methane photochemistry and methane production on Neptune

    SciTech Connect

    Romani, P.N.; Atreya, S.K.

    1988-06-01

    The Neptune stratosphere's methane photochemistry is presently studied by means of a numerical model in which the observed mixing ratio of methane prompts photolysis near the CH4 homopause. Haze generation by methane photochemistry has its basis in the formation of hydrocarbon ices and polyacetylenes; the hazes can furnish the requisite aerosol haze at the appropriate pressure levels required by observations of Neptune in the visible and near-IR. Comparisons of model predictions with Uranus data indicate a lower ratio of polyacetylene production to hydrocarbon ice, as well as a lower likelihood of UV postprocessing of the acetylene ice to polymers on Neptune, compared to Uranus. 65 references.

  15. Methane emission from sewers.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie; Sharma, Keshab R; Yuan, Zhiguo

    2015-08-15

    Recent studies have shown that sewer systems produce and emit a significant amount of methane. Methanogens produce methane under anaerobic conditions in sewer biofilms and sediments, and the stratification of methanogens and sulfate-reducing bacteria may explain the simultaneous production of methane and sulfide in sewers. No significant methane sinks or methanotrophic activities have been identified in sewers to date. Therefore, most of the methane would be emitted at the interface between sewage and atmosphere in gravity sewers, pumping stations, and inlets of wastewater treatment plants, although oxidation of methane in the aeration basin of a wastewater treatment plant has been reported recently. Online measurements have also revealed highly dynamic temporal and spatial variations in methane production caused by factors such as hydraulic retention time, area-to-volume ratio, temperature, and concentration of organic matter in sewage. Both mechanistic and empirical models have been proposed to predict methane production in sewers. Due to the sensitivity of methanogens to environmental conditions, most of the chemicals effective in controlling sulfide in sewers also suppress or diminish methane production. In this paper, we review the recent studies on methane emission from sewers, including the production mechanisms, quantification, modeling, and mitigation. PMID:25889543

  16. Methane emission from sewers.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie; Sharma, Keshab R; Yuan, Zhiguo

    2015-08-15

    Recent studies have shown that sewer systems produce and emit a significant amount of methane. Methanogens produce methane under anaerobic conditions in sewer biofilms and sediments, and the stratification of methanogens and sulfate-reducing bacteria may explain the simultaneous production of methane and sulfide in sewers. No significant methane sinks or methanotrophic activities have been identified in sewers to date. Therefore, most of the methane would be emitted at the interface between sewage and atmosphere in gravity sewers, pumping stations, and inlets of wastewater treatment plants, although oxidation of methane in the aeration basin of a wastewater treatment plant has been reported recently. Online measurements have also revealed highly dynamic temporal and spatial variations in methane production caused by factors such as hydraulic retention time, area-to-volume ratio, temperature, and concentration of organic matter in sewage. Both mechanistic and empirical models have been proposed to predict methane production in sewers. Due to the sensitivity of methanogens to environmental conditions, most of the chemicals effective in controlling sulfide in sewers also suppress or diminish methane production. In this paper, we review the recent studies on methane emission from sewers, including the production mechanisms, quantification, modeling, and mitigation.

  17. Methane-Powered Vehicles

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Liquid methane is beginning to become an energy alternative to expensive oil as a power source for automotive vehicles. Methane is the principal component of natural gas, costs less than half as much as gasoline, and its emissions are a lot cleaner than from gasoline or diesel engines. Beech Aircraft Corporation's Boulder Division has designed and is producing a system for converting cars and trucks to liquid methane operation. Liquid methane (LM) is a cryogenic fuel which must be stored at a temperature of 260 degrees below zero Fahrenheit. The LM system includes an 18 gallon fuel tank in the trunk and simple "under the hood" carburetor conversion equipment. Optional twin-fuel system allows operator to use either LM or gasoline fuel. Boulder Division has started deliveries for 25 vehicle conversions and is furnishing a liquid methane refueling station. Beech is providing instruction for Northwest Natural Gas, for conversion of methane to liquid state.

  18. Mars methane engine

    NASA Technical Reports Server (NTRS)

    Bui, Hung; Coletta, Chris; Debois, Alain

    1994-01-01

    The feasibility of an internal combustion engine operating on a mixture of methane, carbon dioxide, and oxygen has been verified by previous design groups for the Mars Methane Engine Project. Preliminary stoichiometric calculations examined the theoretical fuel-air ratios needed for the combustion of methane. Installation of a computer data acquisition system along with various ancillary components will enable the performance of the engine, running on the described methane mixture, to be optimized with respect to minimizing excess fuel. Theoretical calculations for stoichiometric combustion of methane-oxygen-carbon dioxide mixtures yielded a ratio of 1:2:4.79 for a methane-oxygen-carbon dioxide mixture. Empirical data shows the values to be closer to 1:2.33:3.69 for optimum operation.

  19. Enhancement of Biogenic Coalbed Methane Production and Back Injection of Coalbed Methane Co-Produced Water

    SciTech Connect

    Song Jin

    2007-05-31

    Biogenic methane is a common constituent in deep subsurface environments such as coalbeds and oil shale beds. Coalbed methane (CBM) makes significant contributions to world natural gas industry and CBM production continues to increase. With increasing CBM production, the production of CBM co-produced water increases, which is an environmental concern. This study investigated the feasibility in re-using CBM co-produced water and other high sodic/saline water to enhance biogenic methane production from coal and other unconventional sources, such as oil shale. Microcosms were established with the selected carbon sources which included coal, oil shale, lignite, peat, and diesel-contaminated soil. Each microcosm contained either CBM coproduced water or groundwater with various enhancement and inhibitor combinations. Results indicated that the addition of nutrients and nutrients with additional carbon can enhance biogenic methane production from coal and oil shale. Methane production from oil shale was much greater than that from coal, which is possibly due to the greater amount of available Dissolved Organic Carbon (DOC) from oil shale. Inconclusive results were observed from the other sources since the incubation period was too low. WRI is continuing studies with biogenic methane production from oil shale.

  20. In-Situ Sampling and Characterization of Naturally Occurring Marine Methane Hydrate Using the D/V JOIDES Resolution

    SciTech Connect

    Rack, Frank; Storms, Michael; Schroeder, Derryl; Dugan, Brandon; Schultheiss, Peter

    2002-12-31

    The primary accomplishments of the JOI Cooperative Agreement with DOE/NETL in this quarter were (1) the preliminary postcruise evaluation of the tools and measurement systems that were used during ODP Leg 204 to study hydrate deposits on Hydrate Ridge, offshore Oregon from July through September 2002; and (2) the preliminary study of the hydrate-bearing core samples preserved in pressure vessels and in liquid nitrogen cryofreezers, which are now stored at the ODP Gulf Coast Repository in College Station, TX. During ODP Leg 204, several newly modified downhole tools were deployed to better characterize the subsurface lithologies and environments hosting microbial populations and gas hydrates. A preliminary review of the use of these tools is provided herein. The DVTP, DVTP-P, APC-methane, and APC-Temperature tools (ODP memory tools) were used extensively and successfully during ODP Leg 204 aboard the D/V JOIDES Resolution. These systems provided a strong operational capability for characterizing the in situ properties of methane hydrates in subsurface environments on Hydrate Ridge during ODP Leg 204. Pressure was also measured during a trial run of the Fugro piezoprobe, which operates on similar principles as the DVTP-P. The final report describing the deployments of the Fugro Piezoprobe is provided in Appendix A of this report. A preliminary analysis and comparison between the piezoprobe and DVTP-P tools is provided in Appendix B of this report. Finally, a series of additional holes were cored at the crest of Hydrate Ridge (Site 1249) specifically geared toward the rapid recovery and preservation of hydrate samples as part of a hydrate geriatric study partially funded by the Department of Energy (DOE). In addition, the preliminary results from gamma density non-invasive imaging of the cores preserved in pressure vessels are provided in Appendix C of this report. An initial visual inspection of the samples stored in liquid nitrogen is provided in Appendix D of this

  1. Detecting Methane Leaks

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Hinkley, E. D.

    1984-01-01

    Remote sensor uses laser radiation backscattered from natural targets. He/Ne Laser System for remote scanning of Methane leaks employs topographic target to scatter light to receiver near laser transmitter. Apparatus powered by 1.5kW generator transported to field sites and pointed at suspected methane leaks. Used for remote detection of natural-gas leaks and locating methane emissions in landfill sites.

  2. Methane emissions from cattle.

    PubMed

    Johnson, K A; Johnson, D E

    1995-08-01

    Increasing atmospheric concentrations of methane have led scientists to examine its sources of origin. Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%. Many factors influence methane emissions from cattle and include the following: level of feed intake, type of carbohydrate in the diet, feed processing, addition of lipids or ionophores to the diet, and alterations in the ruminal microflora. Manipulation of these factors can reduce methane emissions from cattle. Many techniques exist to quantify methane emissions from individual or groups of animals. Enclosure techniques are precise but require trained animals and may limit animal movement. Isotopic and nonisotopic tracer techniques may also be used effectively. Prediction equations based on fermentation balance or feed characteristics have been used to estimate methane production. These equations are useful, but the assumptions and conditions that must be met for each equation limit their ability to accurately predict methane production. Methane production from groups of animals can be measured by mass balance, micrometeorological, or tracer methods. These techniques can measure methane emissions from animals in either indoor or outdoor enclosures. Use of these techniques and knowledge of the factors that impact methane production can result in the development of mitigation strategies to reduce methane losses by cattle. Implementation of these strategies should result in enhanced animal productivity and decreased contributions by cattle to the atmospheric methane budget.

  3. Methane-derived authigenic carbonates from the northern Gulf of Mexico - MD02 Cruise

    USGS Publications Warehouse

    Chen, Y.; Matsumoto, R.; Paull, C.K.; Ussler, W.; Lorenson, T.; Hart, P.; Winters, W.

    2007-01-01

    Authigenic carbonates were sampled in piston cores collected from both the Tunica Mound and the Mississippi Canyon area on the continental slope of the northern Gulf of Mexico during a Marion Dufresne cruise in July 2002. The carbonates are present as hardgrounds, porous crusts, concretions or nodules and shell fragments with or without carbonate cements. Carbonates occurred at gas venting sites which are likely to overlie gas hydrates bearing sediments. Electron microprobe, X-ray diffraction (XRD) and thinsection investigations show that these carbonates are high-Mg calcite (6-21??mol% MgCO3), with significant presence of framboidal pyrite. All carbonates are depleted in 13C (??13C = - 61.9 to - 31.5??? PDB) indicating that the carbon is derived mainly from anaerobic methane oxidation (AMO). Age estimates based on 14C dating of shell fragments and on regional sedimentation rates indicate that these authigenic carbonates formed within the last 1000??yr in the Mississippi Canyon and within 5500??yr at the Tunica Mound. The oxygen isotopic composition of carbonates ranges from + 3.4 to + 5.9??? PDB. Oxygen isotopic compositions and Mg2+ contents of carbonates, and present in-situ temperatures of bottom seawater/sediments, show that some of these carbonates, especially from a core associated with underlying massive gas hydrates precipitated in or near equilibrium with bottom-water. On the other hand, those carbonates more enriched in 18O are interpreted to have precipitated from 18O-rich fluids which are thought to have been derived from the dissociation of gas hydrates. The dissociation of gas hydrates in the northern Gulf of Mexico within the last 5500??yr may be caused by nearby salt movement and related brines. ?? 2007 Elsevier B.V. All rights reserved.

  4. Seafloor methane: Atlantic bubble bath

    NASA Astrophysics Data System (ADS)

    Kessler, John

    2014-09-01

    The release of large quantities of methane from ocean sediments might affect global climate change. The discovery of expansive methane seeps along the US Atlantic margin provides an ideal test bed for such a marine methane-climate connection.

  5. Importance of the autumn overturn and anoxic conditions in the hypolimnion for the annual methane emissions from a temperate lake.

    PubMed

    Encinas Fernández, Jorge; Peeters, Frank; Hofmann, Hilmar

    2014-07-01

    Changes in the budget of dissolved methane measured in a small temperate lake over 1 year indicate that anoxic conditions in the hypolimnion and the autumn overturn period represent key factors for the overall annual methane emissions from lakes. During periods of stable stratification, large amounts of methane accumulate in anoxic deep waters. Approximately 46% of the stored methane was emitted during the autumn overturn, contributing ∼80% of the annual diffusive methane emissions to the atmosphere. After the overturn period, the entire water column was oxic, and only 1% of the original quantity of methane remained in the water column. Current estimates of global methane emissions assume that all of the stored methane is released, whereas several studies of individual lakes have suggested that a major fraction of the stored methane is oxidized during overturns. Our results provide evidence that not all of the stored methane is released to the atmosphere during the overturn period. However, the fraction of stored methane emitted to the atmosphere during overturn may be substantially larger and the fraction of stored methane oxidized may be smaller than in the previous studies suggesting high oxidation losses of methane. The development or change in the vertical extent and duration of the anoxic hypolimnion, which can represent the main source of annual methane emissions from small lakes, may be an important aspect to consider for impact assessments of climate warming on the methane emissions from lakes.

  6. Eagle Fort Shale Play Methane Source and Fate Assessment

    NASA Astrophysics Data System (ADS)

    hampton, C. L.; Coffin, R. B.; Rose, P. S.; Boyd, T. J.; Murgulet, D.

    2013-12-01

    Shale gas is a new and important energy source in the United States. Methane in elevated concentrations has been observed in aquifers overlying active horizontal drilling sites in the Marcellus Shale operation area. In South Texas, horizontal fracturing is being applied to petroleum exploration in the Eagle Ford Shale play. Horizontal drilling and hydraulic fracturing can enhance methane transport to deep aquifers, soil, and the vadose zone. There is little information available regarding the presence and origin of methane in Texas groundwaters and the influence of horizontal fracking. The objective of this study is to assess the extent, severity, and sources of methane contamination in South Texas groundwaters. The ultimate goal of this research is to understand potential environmental impacts of hydraulic fracking on groundwater supplies. For this purpose, 35 groundwater samples were collected from active and non-active drilling areas at depths ranging between 50 and 1,300 meters. Stable carbon isotopes in methane (δ13CCH4) and carbon stable isotope ratios in dissolved incorganic carbon (δ13CDIC) analysis were measured to determine the range of signatures for shale petroleum-sourced methane and to differentiate between methane sources (i.e. microbial versus thermogenic). The preliminary δ13CCH4 data set suggests the presence of multiple sources of methane in the aquifers sampled. Stable isotope signatures of CH4 and DIC will help differentiate between sources.

  7. Coupled pyrite concentration and sulfur isotopic insight into the paleo sulfate-methane transition zone (SMTZ) in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Lin, Qi; Wang, Jiasheng; Taladay, Katie; Lu, Hongfeng; Hu, Gaowei; Sun, Fei; Lin, Rongxiao

    2016-01-01

    The sulfate-methane transition zone (SMTZ) is an important diagenetic redox boundary within marine sediments where the anaerobic oxidation of methane (AOM), coupled with bacterial sulfate reduction, can promote sulfur isotopic enrichments in several solid phase minerals including pyrite (FeS2). Authigenic pyrite can form in concentrated abundances within the SMTZ and as such, can be used as a proxy to identify paleo-SMTZs. This study uses enrichments in 34S and anomalously high abundances of authigenic pyrites in 287 samples from the northern South China Sea (SCS) to determine the paleo-SMTZ. The pyrite samples were collected from sediment cores acquired at three sites, each of which are known to be located in natural gas hydrate-bearing regions. We assess the relative abundances of authigenic pyrites, the types of pyrite morphologies recovered in the cored sediments, and the sulfur isotopic values of recovered pyrite samples using two methods: (1) handpicked sample analysis using a binocular microscope, and (2) the chromium reduction method. Our results show that pyrite concentrations and sulfur isotopic compositions exhibit synchronous fluctuations, particularly from 6.8 m below seafloor (mbsf) to 8.4 mbsf at all three study sites. There is a significant increase in the occurrence of rod-like pyrite morphology within this key interval. We define the position of the paleo-SMTZ by the presence of anomalously high accumulations of pyrites at greater than 5.0 wt.% using the handpicking method or greater than 0.5 wt.% via the chromium reduction method, along with positive Δδ34S excursions greater than 10.0‰ VCDT. We discovered a regional paleo-SMTZ that is shallower than the modern SMTZ, suggesting a previous period of elevated methane flux from depth, possibly related to widespread gas hydrate dissociation.

  8. The future of methane

    SciTech Connect

    Howell, D.G.

    1995-12-31

    Natural gas, mainly methane, produces lower CO{sub 2}, CO, NO{sub x}, SO{sub 2} and particulate emissions than either oil or coal; thus further substitutions of methane for these fuels could help mitigate air pollution. Methane is, however, a potent greenhouse gas and the domestication of ruminants, cultivation of rice, mining of coal, drilling for oil, and transportation of natural gas have all contributed to a doubling of the amount of atmospheric methane since 1800. Today nearly 300,000 wells yearly produce ca. 21 trillion cubic feet of methane. Known reserves suggest about a 10 year supply at the above rates of recovery; and the potential for undiscovered resources is obscured by uncertainty involving price, new technologies, and environmental restrictions steming from the need to drill an enormous number of wells, many in ecologically sensitive areas. Until all these aspects of methane are better understood, its future role in the world`s energy mix will remain uncertain. The atomic simplicity of methane, composed of one carbon and four hydrogen atoms, may mask the complexity and importance of this, the most basic of organic molecules. Within the Earth, methane is produced through thermochemical alteration of organic materials, and by biochemical reactions mediated by metabolic processes of archaebacteria; some methane may even be primordial, a residue of planetary accretion. Methane also occurs in smaller volumes in landfills, rice paddies, termite complexes, ruminants, and even many humans. As an energy source, its full energy potential is controversial. Methane is touted by some as a viable bridge to future energy systems, fueled by the sun and uranium and carried by electricity and hydrogen.

  9. Global dispersion and local diversification of the methane seep microbiome

    PubMed Central

    Ruff, S. Emil; Biddle, Jennifer F.; Teske, Andreas P.; Knittel, Katrin; Boetius, Antje

    2015-01-01

    Methane seeps are widespread seafloor ecosystems shaped by the emission of gas from seabed reservoirs. The microorganisms inhabiting methane seeps transform the chemical energy in methane to products that sustain rich benthic communities around the gas leaks. Despite the biogeochemical relevance of microbial methane removal at seeps, the global diversity and dispersion of seep microbiota remain unknown. Here we determined the microbial diversity and community structure of 23 globally distributed methane seeps and compared these to the microbial communities of 54 other seafloor ecosystems, including sulfate–methane transition zones, hydrothermal vents, coastal sediments, and deep-sea surface and subsurface sediments. We found that methane seep communities show moderate levels of microbial richness compared with other seafloor ecosystems and harbor distinct bacterial and archaeal taxa with cosmopolitan distribution and key biogeochemical functions. The high relative sequence abundance of ANME (anaerobic methanotrophic archaea), as well as aerobic Methylococcales, sulfate-reducing Desulfobacterales, and sulfide-oxidizing Thiotrichales, matches the most favorable microbial metabolisms at methane seeps in terms of substrate supply and distinguishes the seep microbiome from other seafloor microbiomes. The key functional taxa varied in relative sequence abundance between different seeps due to the environmental factors, sediment depth and seafloor temperature. The degree of endemism of the methane seep microbiome suggests a high local diversification in these heterogeneous but long-lived ecosystems. Our results indicate that the seep microbiome is structured according to metacommunity processes and that few cosmopolitan microbial taxa mediate the bulk of methane oxidation, with global relevance to methane emission in the ocean. PMID:25775520

  10. Global dispersion and local diversification of the methane seep microbiome.

    PubMed

    Ruff, S Emil; Biddle, Jennifer F; Teske, Andreas P; Knittel, Katrin; Boetius, Antje; Ramette, Alban

    2015-03-31

    Methane seeps are widespread seafloor ecosystems shaped by the emission of gas from seabed reservoirs. The microorganisms inhabiting methane seeps transform the chemical energy in methane to products that sustain rich benthic communities around the gas leaks. Despite the biogeochemical relevance of microbial methane removal at seeps, the global diversity and dispersion of seep microbiota remain unknown. Here we determined the microbial diversity and community structure of 23 globally distributed methane seeps and compared these to the microbial communities of 54 other seafloor ecosystems, including sulfate-methane transition zones, hydrothermal vents, coastal sediments, and deep-sea surface and subsurface sediments. We found that methane seep communities show moderate levels of microbial richness compared with other seafloor ecosystems and harbor distinct bacterial and archaeal taxa with cosmopolitan distribution and key biogeochemical functions. The high relative sequence abundance of ANME (anaerobic methanotrophic archaea), as well as aerobic Methylococcales, sulfate-reducing Desulfobacterales, and sulfide-oxidizing Thiotrichales, matches the most favorable microbial metabolisms at methane seeps in terms of substrate supply and distinguishes the seep microbiome from other seafloor microbiomes. The key functional taxa varied in relative sequence abundance between different seeps due to the environmental factors, sediment depth and seafloor temperature. The degree of endemism of the methane seep microbiome suggests a high local diversification in these heterogeneous but long-lived ecosystems. Our results indicate that the seep microbiome is structured according to metacommunity processes and that few cosmopolitan microbial taxa mediate the bulk of methane oxidation, with global relevance to methane emission in the ocean.

  11. Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues

    NASA Astrophysics Data System (ADS)

    Douglas, P. M. J.; Stolper, D. A.; Smith, D. A.; Walter Anthony, K. M.; Paull, C. K.; Dallimore, S.; Wik, M.; Crill, P. M.; Winterdahl, M.; Eiler, J. M.; Sessions, A. L.

    2016-09-01

    Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understanding present and future Arctic contributions to atmospheric methane budgets. Here we apply measurements of multiply-substituted isotopologues, or clumped isotopes, of methane as a new tool to identify the origins of ebullitive fluxes in Alaska, Sweden and the Arctic Ocean. When methane forms in isotopic equilibrium, clumped isotope measurements indicate the formation temperature. In some microbial methane, however, non-equilibrium isotope effects, probably related to the kinetics of methanogenesis, lead to low clumped isotope values. We identify four categories of emissions in the studied samples: thermogenic methane, deep subsurface or marine microbial methane formed in isotopic equilibrium, freshwater microbial methane with non-equilibrium clumped isotope values, and mixtures of deep and shallow methane (i.e., combinations of the first three end members). Mixing between deep and shallow methane sources produces a non-linear variation in clumped isotope values with mixing proportion that provides new constraints for the formation environment of the mixing end-members. Analyses of microbial methane emitted from lakes, as well as a methanol-consuming methanogen pure culture, support the hypothesis that non-equilibrium clumped isotope values are controlled, in part, by kinetic isotope effects induced during enzymatic reactions involved in methanogenesis. Our results indicate that these kinetic isotope effects vary widely in microbial methane produced in Arctic lake sediments, with non-equilibrium Δ18 values spanning a range of more than 5‰.

  12. Methanation assembly using multiple reactors

    DOEpatents

    Jahnke, Fred C.; Parab, Sanjay C.

    2007-07-24

    A methanation assembly for use with a water supply and a gas supply containing gas to be methanated in which a reactor assembly has a plurality of methanation reactors each for methanating gas input to the assembly and a gas delivery and cooling assembly adapted to deliver gas from the gas supply to each of said methanation reactors and to combine water from the water supply with the output of each methanation reactor being conveyed to a next methanation reactor and carry the mixture to such next methanation reactor.

  13. Methane drizzle on Titan.

    PubMed

    Tokano, Tetsuya; McKay, Christopher P; Neubauer, Fritz M; Atreya, Sushil K; Ferri, Francesca; Fulchignoni, Marcello; Niemann, Hasso B

    2006-07-27

    Saturn's moon Titan shows landscapes with fluvial features suggestive of hydrology based on liquid methane. Recent efforts in understanding Titan's methane hydrological cycle have focused on occasional cloud outbursts near the south pole or cloud streaks at southern mid-latitudes and the mechanisms of their formation. It is not known, however, if the clouds produce rain or if there are also non-convective clouds, as predicted by several models. Here we show that the in situ data on the methane concentration and temperature profile in Titan's troposphere point to the presence of layered optically thin stratiform clouds. The data indicate an upper methane ice cloud and a lower, barely visible, liquid methane-nitrogen cloud, with a gap in between. The lower, liquid, cloud produces drizzle that reaches the surface. These non-convective methane clouds are quasi-permanent features supported by the global atmospheric circulation, indicating that methane precipitation occurs wherever there is slow upward motion. This drizzle is a persistent component of Titan's methane hydrological cycle and, by wetting the surface on a global scale, plays an active role in the surface geology of Titan.

  14. Methane conversion process

    SciTech Connect

    Gaffney, A.M.; Jones, C.A.; Sofranko, J.A.

    1989-01-03

    This patent describes a process for the conversion of methane to higher hydrocarbons and coproduct water wherein methane is contacted at reactive conditions with a conversion catalyst comprised of a reducible metal oxide selected from the group consisting of an oxide of manganese, tin, indium, germanium, antimony, leads, bismuth, cerium, praseodymium, terbium, iron, and ruthenium. The improvement consists of: pretreating the catalyst before use in the conversion of methane to higher hydrocarbons and coproduct water with a reducing agent at 650/sup 0/C to 1200/sup 0/C for a time sufficient to improve the bulk density and attrition resistance of the catalyst and thereafter contacting the pretreated catalyst with methane at methane conversion conditions effective to form higher hydrocarbons and coproduct water.

  15. Hypotheses for Near-Surface Exchange of Methane on Mars

    NASA Astrophysics Data System (ADS)

    Hu, Renyu; Bloom, A. Anthony; Gao, Peter; Miller, Charles E.; Yung, Yuk L.

    2016-07-01

    The Curiosity rover recently detected a background of 0.7 ppb and spikes of 7 ppb of methane on Mars. This in situ measurement reorients our understanding of the martian environment and its potential for life, as the current theories do not entail any geological source or sink of methane that varies sub-annually. In particular, the 10-fold elevation during the southern winter indicates episodic sources of methane that are yet to be discovered. Here we suggest a near-surface reservoir could explain this variability. Using the temperature and humidity measurements from the rover, we find that perchlorate salts in the regolith deliquesce to form liquid solutions, and deliquescence progresses to deeper subsurface in the season of the methane spikes. We therefore formulate the following three testable hypotheses. The first scenario is that the regolith in Gale Crater adsorbs methane when dry and releases this methane to the atmosphere upon deliquescence. The adsorption energy needs to be 36 kJ mol-1 to explain the magnitude of the methane spikes, higher than existing laboratory measurements. The second scenario is that microorganisms convert organic matter in the soil to methane when they are in liquid solutions. This scenario does not require regolith adsorption but entails extant life on Mars. The third scenario is that deep subsurface aquifers produce the bursts of methane. Continued in situ measurements of methane and water, as well as laboratory studies of adsorption and deliquescence, will test these hypotheses and inform the existence of the near-surface reservoir and its exchange with the atmosphere.

  16. Methane emission by camelids.

    PubMed

    Dittmann, Marie T; Runge, Ullrich; Lang, Richard A; Moser, Dario; Galeffi, Cordula; Kreuzer, Michael; Clauss, Marcus

    2014-01-01

    Methane emissions from ruminant livestock have been intensively studied in order to reduce contribution to the greenhouse effect. Ruminants were found to produce more enteric methane than other mammalian herbivores. As camelids share some features of their digestive anatomy and physiology with ruminants, it has been proposed that they produce similar amounts of methane per unit of body mass. This is of special relevance for countrywide greenhouse gas budgets of countries that harbor large populations of camelids like Australia. However, hardly any quantitative methane emission measurements have been performed in camelids. In order to fill this gap, we carried out respiration chamber measurements with three camelid species (Vicugna pacos, Lama glama, Camelus bactrianus; n = 16 in total), all kept on a diet consisting of food produced from alfalfa only. The camelids produced less methane expressed on the basis of body mass (0.32±0.11 L kg⁻¹ d⁻¹) when compared to literature data on domestic ruminants fed on roughage diets (0.58±0.16 L kg⁻¹ d⁻¹). However, there was no significant difference between the two suborders when methane emission was expressed on the basis of digestible neutral detergent fiber intake (92.7±33.9 L kg⁻¹ in camelids vs. 86.2±12.1 L kg⁻¹ in ruminants). This implies that the pathways of methanogenesis forming part of the microbial digestion of fiber in the foregut are similar between the groups, and that the lower methane emission of camelids can be explained by their generally lower relative food intake. Our results suggest that the methane emission of Australia's feral camels corresponds only to 1 to 2% of the methane amount produced by the countries' domestic ruminants and that calculations of greenhouse gas budgets of countries with large camelid populations based on equations developed for ruminants are generally overestimating the actual levels.

  17. New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents

    NASA Astrophysics Data System (ADS)

    Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio

    2016-05-01

    Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria’s coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries.

  18. New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents.

    PubMed

    Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio

    2016-05-27

    Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria's coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries.

  19. New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents

    PubMed Central

    Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio

    2016-01-01

    Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria’s coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries. PMID:27230887

  20. New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents.

    PubMed

    Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio

    2016-01-01

    Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria's coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries. PMID:27230887

  1. Artificial electron acceptors decouple archaeal methane oxidation from sulfate reduction.

    PubMed

    Scheller, Silvan; Yu, Hang; Chadwick, Grayson L; McGlynn, Shawn E; Orphan, Victoria J

    2016-02-12

    The oxidation of methane with sulfate is an important microbial metabolism in the global carbon cycle. In marine methane seeps, this process is mediated by consortia of anaerobic methanotrophic archaea (ANME) that live in syntrophy with sulfate-reducing bacteria (SRB). The underlying interdependencies within this uncultured symbiotic partnership are poorly understood. We used a combination of rate measurements and single-cell stable isotope probing to demonstrate that ANME in deep-sea sediments can be catabolically and anabolically decoupled from their syntrophic SRB partners using soluble artificial oxidants. The ANME still sustain high rates of methane oxidation in the absence of sulfate as the terminal oxidant, lending support to the hypothesis that interspecies extracellular electron transfer is the syntrophic mechanism for the anaerobic oxidation of methane.

  2. Methane production from coal by a single methanogen

    NASA Astrophysics Data System (ADS)

    Mayumi, Daisuke; Mochimaru, Hanako; Tamaki, Hideyuki; Yamamoto, Kyosuke; Yoshioka, Hideyoshi; Suzuki, Yuichiro; Kamagata, Yoichi; Sakata, Susumu

    2016-10-01

    Coal-bed methane is one of the largest unconventional natural gas resources. Although microbial activity may greatly contribute to coal-bed methane formation, it is unclear whether the complex aromatic organic compounds present in coal can be used for methanogenesis. We show that deep subsurface–derived Methermicoccus methanogens can produce methane from more than 30 types of methoxylated aromatic compounds (MACs) as well as from coals containing MACs. In contrast to known methanogenesis pathways involving one- and two-carbon compounds, this “methoxydotrophic” mode of methanogenesis couples O-demethylation, CO2 reduction, and possibly acetyl–coenzyme A metabolism. Because MACs derived from lignin may occur widely in subsurface sediments, methoxydotrophic methanogenesis would play an important role in the formation of natural gas not limited to coal-bed methane and in the global carbon cycle.

  3. Mars Methane Plume Tracer

    NASA Astrophysics Data System (ADS)

    Mischna, M. A.; Banfield, D.; Sykes, I.

    2014-07-01

    Putative releases of methane from the martian surface may be challenging to detect from orbit. Successful detections depend on the character of the plume itself (duration, magnitude, expanse), but also on the observing platform.

  4. Methane heat transfer investigation

    NASA Technical Reports Server (NTRS)

    Cook, R. T.

    1984-01-01

    Future high chamber pressure LOX/hydrocarbon booster engines require copper-base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and resuable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper-base alloy material adjacent to the fuel coolant. High-pressure methane cooling and coking characteristics were recently evaluated using stainless-steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper-base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.

  5. Methane heat transfer investigation

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Future high chamber pressure LOX/hydrocarbon booster engines require copper base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and reusable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper base alloy material adjacent to he fuel coolant. High pressure methane cooling and coking characteristics recently evaluated at Rocketdyne using stainless steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.

  6. Enzymatic Oxidation of Methane

    SciTech Connect

    Sirajuddin, S; Rosenzweig, AC

    2015-04-14

    Methane monooxygenases (MMOs) are enzymes that catalyze the oxidation of methane to methanol in methanotrophic bacteria. As potential targets for new gas-to-liquid methane bioconversion processes, MMOs have attracted intense attention in recent years. There are two distinct types of MMO, a soluble, cytoplasmic MMO (sMMO) and a membrane-bound, particulate MMO (pMMO). Both oxidize methane at metal centers within a complex, multisubunit scaffold, but the structures, active sites, and chemical mechanisms are completely different. This Current Topic review article focuses on the overall architectures, active site structures, substrate reactivities, proteinprotein interactions, and chemical mechanisms of both MMOs, with an emphasis on fundamental aspects. In addition, recent advances, including new details of interactions between the sMMO components, characterization of sMMO intermediates, and progress toward understanding the pMMO metal centers are highlighted. The work summarized here provides a guide for those interested in exploiting MMOs for biotechnological applications.

  7. Electrochemical methane sensor

    DOEpatents

    Zaromb, S.; Otagawa, T.; Stetter, J.R.

    1984-08-27

    A method and instrument including an electrochemical cell for the detection and measurement of methane in a gas by the oxidation of methane electrochemically at a working electrode in a nonaqueous electrolyte at a voltage about 1.4 volts vs R.H.E. (the reversible hydrogen electrode potential in the same electrolyte), and the measurement of the electrical signal resulting from the electrochemical oxidation.

  8. Laser beam methane detector

    NASA Technical Reports Server (NTRS)

    Hinkley, E. D., Jr.

    1981-01-01

    Instrument uses infrared absorption to determine methane concentration in liquid natural gas vapor. Two sensors measure intensity of 3.39 mm laser beam after it passes through gas; absorption is proportional to concentration of methane. Instrument is used in modeling spread of LNG clouds and as leak detector on LNG carriers and installations. Unit includes wheels for mobility and is both vertically and horizontally operable.

  9. Geologic studies of deep natural gas resources

    USGS Publications Warehouse

    Dyman, T. S., (Edited By); Kuuskraa, V.A.

    2001-01-01

    In 1995, the USGS estimated a mean resource of 114 trillion cubic feet of undiscovered technically recoverable natural gas in plays deeper than 15,000 feet/4,572 meters in onshore regions of the United States. This volume summarizes major conclusions of ongoing work. Chapters A and B address the areal extent of drilling and distribution of deep basins in the U.S. Chapter C summarizes distribution of deep sedimentary basins and potential for deep gas in the former Soviet Union. Chapters D and E are geochemical papers addressing source-rock issues and deep gas generation. Chapter F develops a probabilistic method for subdividing gas resources into depth slices, and chapter G analyzes the relative uncertainty of estimates of deep gas in plays in the Gulf Coast Region. Chapter H evaluates the mechanism of hydrogenation of deep, high-rank spent kerogen by water, with subsequent generation of methane-rich HC gas.

  10. Coring Methane Hydrate by using Hybrid Pressure Coring System of D/V Chikyu

    NASA Astrophysics Data System (ADS)

    Kubo, Y.; Mizuguchi, Y.; Inagaki, F.; Eguchi, N.; Yamamoto, K.

    2013-12-01

    by X-ray CT scan. Hybrid PCS was also used in the following JOGMEC methane hydrate cruise, resulting in the good recovery of methane hydrate-bearing cores (approx. 69%).

  11. Methane Emissions from Upland Forests

    NASA Astrophysics Data System (ADS)

    Megonigal, Patrick; Pitz, Scott; Wang, Zhi-Ping

    2016-04-01

    Global budgets ascribe 4-10% of atmospheric methane sinks to upland soils and assume that soils are the sole surface for methane exchange between upland forests and the atmosphere. The dogma that upland forests are uniformly atmospheric methane sinks was challenged a decade ago by the discovery of abiotic methane production from plant tissue. Subsequently a variety of relatively cryptic microbial and non-microbial methane sources have been proposed that have the potential to emit methane in upland forests. Despite the accumulating evidence of potential methane sources, there are few data demonstrating actual emissions of methane from a plant surface in an upland forest. We report direct observations of methane emissions from upland tree stems in two temperate forests. Stem methane emissions were observed from several tree species that dominate a forest located on the mid-Atlantic coast of North America (Maryland, USA). Stem emissions occurred throughout the growing season while soils adjacent to the trees simultaneously consumed methane. Scaling fluxes by stem surface area suggested the forest was a net methane source during a wet period in June, and that stem emissions offset 5% of the soil methane sink on an annual basis. High frequency measurements revealed diurnal cycles in stem methane emission rates, pointing to soils as the methane source and transpiration as the most likely pathway for gas transport. Similar observations were made in an upland forest in Beijing, China. However, in this case the evidence suggested the methane was not produced in soils, but in the heartwood by microbial or non-microbial processes. These data challenge the concept that forests are uniform sinks of methane, and suggest that upland forests are smaller methane sinks than previously estimated due to stem emissions. Tree emissions may be particularly important in upland tropical forests characterized by high rainfall and transpiration.

  12. Abiotic Methane Synthesis: Caveats and New Results

    NASA Astrophysics Data System (ADS)

    Zou, R.; Sharma, A.

    2005-12-01

    The role of mineral interaction with geochemical fluids under hydrothermal conditions has invoked models of geochemical synthesis of organic molecules at deep crustal conditions. Since Thomas Gold's (1992) hypothesis of the possibility of an abiotic organic synthesis, there have been several reports of hydrocarbon formation under high pressure and temperature conditions. Several previous experimental studies have recognized that small amounts of methane (and other light HC compounds) can be synthesized via catalysis by transition metals: Fe, Ni (Horita and Berndt, 1999 Science) and Cr (Foustavous and Seyfried, 2004 Science). In light of these pioneering experiments, an investigation of the feasibility of abiotic methane synthesis at higher pressure conditions in deep geological setting and the possible role of catalysis warrants a closer look. We conducted three sets of experiments in hydrothermal diamond anvil cell using FeO nanopowder, CaCO 3 and water at 300° - 600° C and 0.5 - 5 GPa : (a) with stainless steel gasket, (b) gold-lined gasket, and (c) gold-lined gasket with added Fe and Ni nanopowder. The reactions were monitored in-situ using micro-Raman spectroscopy with 532nm and 632nm lasers. The solids phases were characterized in-situ using synchrotron X-ray diffraction at CHESS-Cornell and quenched products with an electron microprobe. Interestingly, a variable amount of hydrocarbon was observed only in runs with stainless steel gasket and with Fe, Ni nanoparticles. Experiments with gold-lined reactors did not show any hydrocarbon formation. Added high resolution microscopy of the products and their textural relationship within the diamond cell with Raman spectroscopy data show that the hydrocarbon (methane and other light fractions) synthesis is a direct result of transition metal catalysis, rather than wustite - calcium carbonate reaction as recently reported by Scott et al (2004, PNAS). The author will further present new results highlighting abiotic

  13. Methane metabolism in the archaeal phylum Bathyarchaeota revealed by genome-centric metagenomics.

    PubMed

    Evans, Paul N; Parks, Donovan H; Chadwick, Grayson L; Robbins, Steven J; Orphan, Victoria J; Golding, Suzanne D; Tyson, Gene W

    2015-10-23

    Methanogenic and methanotrophic archaea play important roles in the global flux of methane. Culture-independent approaches are providing deeper insight into the diversity and evolution of methane-metabolizing microorganisms, but, until now, no compelling evidence has existed for methane metabolism in archaea outside the phylum Euryarchaeota. We performed metagenomic sequencing of a deep aquifer, recovering two near-complete genomes belonging to the archaeal phylum Bathyarchaeota (formerly known as the Miscellaneous Crenarchaeotal Group). These genomes contain divergent homologs of the genes necessary for methane metabolism, including those that encode the methyl-coenzyme M reductase (MCR) complex. Additional non-euryarchaeotal MCR-encoding genes identified in a range of environments suggest that unrecognized archaeal lineages may also contribute to global methane cycling. These findings indicate that methane metabolism arose before the last common ancestor of the Euryarchaeota and Bathyarchaeota.

  14. Methane on Titan: Photochemical-Meteorological-Hydrogeochemical Cycle

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Niemann, H. B.; Owen, T. C.; Adams, E. Y.; Demick, J. E.; GCMS Team

    2005-08-01

    Photochemically driven destruction of methane in Titan's stratosphere leads to irreversible conversion to heavier hydrocarbons (1). The latter would largely condense out of the atmosphere (2). In the absence of recycling, Titan's methane would thus be destroyed in 10-100 million years (1). However, methane is key to the maintenance of Titan's nitrogen atmosphere. Without warming provided by CH4-generated hydrocarbon hazes in the stratosphere and pressure induced opacity in the infrared, particularly by H2-N2 and CH4-N2 collisions in the troposphere, the atmosphere would gradually diminish to tens of millibar pressure (3). Thus, the source-sink cycle of methane is crucial to the evolutionary history of Titan and its atmosphere. The GCMS measurements show that a ``methalogical" cycle with surface evaporation, cloud formation, followed by precipitation (rain) of methane exists. However, this ``closed" cycle does not recycle methane lost to heavy hydrocarbons. A source is required. Unlike the deep, hot, H2-rich interiors of the giant planets, Titan's interior is ill suited for thermochemical conversion of hydrocarbons back to methane. Instead we propose that serpentinization is an effective process for producing methane in Titan's interior (4). Hydration of ultramafic silicates, followed by reaction between the released H2 gas and CO2 or carbon grains can produce large quantities of CH4 at relatively mild (40-90oC) temperatures. Such thermal conditions are believed to exist below the purported water-ammonia ocean (5). Storage of methane produced via serpentinization can occur in form of clathrates. Evidence of outgassing from Titan's interior is provided by GCMS (6) and VIMS (7) data. (1) Wilson, Atreya, JGR 109, E06002, doi:10.1029/2003JE002181, 2004. (2) Wilson, Atreya, PSS 51, 1017, 2003. (3) Lorenz etal. Science 275, 642, 1997. (4) Owen etal. Phys. Uspekhi, in press. (5) Grasset, Pargamin, PSS 53, 371, 2005. (6) Niemann etal., Submitted to Nature, 2005. (7) Sotin

  15. X-ray computed tomography observations of phase distribution during methane hydrate formation and dissociation process in a sediment sample

    NASA Astrophysics Data System (ADS)

    Ahn, Taewoong; Lee, Jaehyoung; Lee, Joo Yong; Kim, Se-Joon; Seo, Young-ju

    2016-04-01

    The recovery schemes for natural gas caged in the solid state have not been commercialized. Depressurization has been known as a promising method due to its economic feasibility according to previous lab-scale experiments and simulation studies. However, the results of few field tests showed that the production characteristics of real field differed from that of predicted results. To reliably predict the production performance of real fields, it is necessary to understand quantitative changes of phase distribution and fluid flow in sediments in response to hydrate dissociation by depressurization. In this study, we observed and analyzed the phase distribution and flow behavior during methane hydrate formation and dissociation using X-ray computed tomography which provides high-resolution density distribution. Artificial particles having similar grain size distribution of sandy layers found in real hydrate field were packed into X-ray transparent aluminum vessel. Information on pore distribution within a sediment sample was achieved by comparing CT images between dry condition and fully water-saturated condition. Dynamic changes of phase saturation were observed during gas flooding, through which potential flow pathway was estimated. Hydrate formation and dissociation significantly affected phase distribution and flow pathway. Hydrate distribution was extremely heterogeneous in every tests of hydrate formation repeated with same amount of water. It was inferred that water saturation prior to hydrate formation was not directly correlated to the hydrate distribution. There were definite differences of hydrate dissociation behavior between gas-saturated and water-saturated hydrate-bearing sample. The production of gas and water lasted quite a while even after the production pressure reached the target level of depressurization.

  16. Studying methane migration mechanisms at Walker Ridge, Gulf of Mexico, via 3D methane hydrate reservoir modeling

    SciTech Connect

    Nole, Michael; Daigle, Hugh; Mohanty, Kishore; Cook, Ann; Hillman, Jess

    2015-12-15

    . Therefore, it is likely that additional mechanisms are at play, notably bound water activity reduction in clays. Three-dimensionality allows for inclusion of lithologic heterogeneities, which focus fluid flow and subsequently allow for heterogeneity in the methane migration mechanisms that dominate in marine sediments at a local scale. Incorporating recently acquired 3D seismic data from Walker Ridge to inform the lithologic structure of our modeled reservoir, we show that even with deep adjective sourcing of methane along highly permeable pathways, local hydrate accumulations can be sourced either by diffusive or advective methane flux; advectively-sourced hydrates accumulate evenly in highly permeable strata, while diffusively-sourced hydrates are characterized by thin strata-bound intervals with high clay-sand pore size contrasts.

  17. The State, Potential Distribution, and Biological Implications of Methane in the Martian Crust

    NASA Technical Reports Server (NTRS)

    Max, Michael D.; Clifford, Stephen M.

    2000-01-01

    The search for life on Mars has recently focused on its potential survival in deep (>2 km) subpermafrost aquifers where anaerobic bacteria, similar to those found in deep subsurface ecosystems on Earth, may have survived in an environment that has remained stable for billions of years. An anticipated by-product of this biological activity is methane. The detection of large deposits of methane gas and hydrate in the Martian cryosphere, or as emissions from deep fracture zones, would provide persuasive evidence of indigenous life and confirm the presence of a valuable in situ resource for use by future human explorers.

  18. Characteristics of slush and boiling methane and methane mixtures.

    NASA Technical Reports Server (NTRS)

    Sindt, C. F.; Ludtke, P. R.

    1971-01-01

    Methane gas of two purities, 99.97% and 99%, was condensed to study the characteristics of the boiling liquid and the slush. In addition, binary mixtures of nitrogen and methane, and those of ethane and methane, and propane and methane, were also studied. Potential advantages of these gases when employed as fuels for high-performance aircraft, rocket engines, and motor vehicles are emphasized.

  19. X-ray CT Observations of Methane Hydrate Distribution Changes over Time in a Natural Sediment Core from the BPX-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well

    SciTech Connect

    Kneafsey, T.J.; Rees, E.V.L.

    2010-03-01

    When maintained under hydrate-stable conditions, methane hydrate in laboratory samples is often considered a stable and immobile solid material. Currently, there do not appear to be any studies in which the long-term redistribution of hydrates in sediments has been investigated in the laboratory. These observations are important because if the location of hydrate in a sample were to change over time (e.g. by dissociating at one location and reforming at another), the properties of the sample that depend on hydrate saturation and pore space occupancy would also change. Observations of hydrate redistribution under stable conditions are also important in understanding natural hydrate deposits, as these may also change over time. The processes by which solid hydrate can move include dissociation, hydrate-former and water migration in the gas and liquid phases, and hydrate formation. Chemical potential gradients induced by temperature, pressure, and pore water or host sediment chemistry can drive these processes. A series of tests were performed on a formerly natural methane-hydrate-bearing core sample from the BPX-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well, in order to observe hydrate formation and morphology within this natural sediment, and changes over time using X-ray computed tomography (CT). Long-term observations (over several weeks) of methane hydrate in natural sediments were made to investigate spatial changes in hydrate saturation in the core. During the test sequence, mild buffered thermal and pressure oscillations occurred within the sample in response to laboratory temperature changes. These oscillations were small in magnitude, and conditions were maintained well within the hydrate stability zone.

  20. Combustion of Methane Hydrate

    NASA Astrophysics Data System (ADS)

    Roshandell, Melika

    A significant methane storehouse is in the form of methane hydrates on the sea floor and in the arctic permafrost. Methane hydrates are ice-like structures composed of water cages housing a guest methane molecule. This caged methane represents a resource of energy and a potential source of strong greenhouse gas. Most research related to methane hydrates has been focused on their formation and dissociation because they can form solid plugs that complicate transport of oil and gas in pipelines. This dissertation explores the direct burning of these methane hydrates where heat from the combustion process dissociates the hydrate into water and methane, and the released methane fuels the methane/air diffusion flame heat source. In contrast to the pipeline applications, very little research has been done on the combustion and burning characteristics of methane hydrates. This is the first dissertation on this subject. In this study, energy release and combustion characteristics of methane hydrates were investigated both theoretically and experimentally. The experimental study involved collaboration with another research group, particularly in the creation of methane hydrate samples. The experiments were difficult because hydrates form at high pressure within a narrow temperature range. The process can be slow and the resulting hydrate can have somewhat variable properties (e.g., extent of clathration, shape, compactness). The experimental study examined broad characteristics of hydrate combustion, including flame appearance, burning time, conditions leading to flame extinguishment, the amount of hydrate water melted versus evaporated, and flame temperature. These properties were observed for samples of different physical size. Hydrate formation is a very slow process with pure water and methane. The addition of small amounts of surfactant increased substantially the hydrate formation rate. The effects of surfactant on burning characteristics were also studied. One finding

  1. Methane formation and methane oxidation by methanogenic bacteria.

    PubMed Central

    Zehnder, A J; Brock, T D

    1979-01-01

    Methanogenic bacteria were found to form and oxidize methane at the same time. As compared to the quantity of methane formed, the amount of methane simultaneously oxidized varied between 0.3 and 0.001%, depending on the strain used. All the nine tested strains of methane producers (Methanobacterium ruminantium, Methanobacterium strain M.o.H., M. formicicum, M. thermoautotrophicum, M. arbophilicum, Methanobacterium strain AZ, Methanosarcina barkeri, Methanospirillum hungatii, and the "acetate organism") reoxidized methane to carbon dioxide. In addition, they assimilated a small part of the methane supplied into cell material. Methanol and acetate also occurred as oxidation products in M. barkeri cultures. Acetate was also formed by the "acetate organism," a methane bacterium unable to use methanogenic substrates other than acetate. Methane was the precursor of the methyl group of the acetate synthesized in the course of methane oxidation. Methane formation and its oxidation were inhibited equally by 2-bromoethanesulfonic acid. Short-term labeling experiments with M. thermoautotrophicum and M. hungatii clearly suggest that the pathway of methane oxidation is not identical with a simple back reaction of the methane formation process. Images PMID:762019

  2. Enhanced coalbed methane recovery

    SciTech Connect

    Mazzotti, M.; Pini, R.; Storti, G.

    2009-01-15

    The recovery of coalbed methane can be enhanced by injecting CO{sub 2} in the coal seam at supercritical conditions. Through an in situ adsorption/desorption process the displaced methane is produced and the adsorbed CO{sub 2} is permanently stored. This is called enhanced coalbed methane recovery (ECBM) and it is a technique under investigation as a possible approach to the geological storage of CO{sub 2} in a carbon dioxide capture and storage system. This work reviews the state of the art on fundamental and practical aspects of the technology and summarizes the results of ECBM field tests. These prove the feasibility of ECBM recovery and highlight substantial opportunities for interdisciplinary research at the interface between earth sciences and chemical engineering.

  3. Arctic Methane Hydrates: A Potential Greenhouse Gas Hazard

    NASA Astrophysics Data System (ADS)

    Light, M. P. R.; Solana, C.

    Methane is one of the most important greenhouse gases present in the atmosphere, having 20 times more warming potential than CO2 over a 100 yr period and 56 times more over a 20 yr period. The submarine arctic ice contains abundant methane trapped as hydrates below the continental shelf and its edge. The reserves in this area are estimated at more than 140 times the volume of methane in the atmosphere and, if released relatively quickly, the effects could be catastrophic. Although some authors have established that submarine hydrates will remain stable for the next 1000 yr, this estimation could change if other phenomena are taken into account. Hydrates within the continental shelf in the Arctic are more unstable because of the increase in oceanic temperatures over the last 10,000 yr. A warm (2C maximum) intermediate depth (5- 500 m) current recently detected in the Arctic basin flowing along the shelf edge will further destabilize the methane hydrates exposed there. In addition, the presence of seismic activity along the Arctic mid-ocean ridge and in the northern Alaska region, with magnitudes greater than 3.5 Richter and epicentres less than 30 km deep, could trigger slope failures where the methane hydrate is unstable, releasing huge volumes of methane into the atmosphere. Therefore, identifying those areas that are potentially unstable under these new conditions and the possibilities of reducing the hazard are a priority in our research.

  4. Methane-Powered Airplane

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Beech Aircraft's Corporation's Boulder Division developed expertise in producing superinsulated virtually leak-proof cryogenic equipment for storing liquid oxygen and hydrogen fuels in NASA's Apollo, Skylab and Space Shuttle programs. Boulder Division used this experience in designing a fuel storage tank for liquid methane, a "cryogenic" fuel that must be supercooled to keep it liquid. Beech Aircraft is producing a four-place lightplane powered by liquid methane (LM) which is stored in two of these specially designed cryogenic storage tanks holding 18 gallons each.

  5. Biomimetic methane oxidation

    SciTech Connect

    Watkins, B.E.; Droege, M.W.; Taylor, R.T.; Satcher, J.H.

    1992-06-12

    Methane monooxygenase (MMO) is an enzyme found in methanotrophs that catalyses the selective oxidation of methane to methanol. MMO is protein complex one component of which is a binuclear metal center containing oxygenase. We have completed one round of a design/synthesis/evaluation cycle in the development of coordination complexes that mimic the structure/function of the MMO active site. One of these, a binuclear, coordinately-asymmetric copper complex, is capable of oxidizing cyclohexane to a mixture of cyclohexanol and cyclohexanone in the presence of hydrogen peroxide.

  6. Methane-related microbial processes and metabolic stratification in a terrestrial mud volcano, southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, T.; Lin, L.; Wang, P.; Chu, P.; Wu, J.

    2009-12-01

    Mud volcanoes are distinct geological features with fluid, sediment and hydrocarbon-enriched gas mixtures emitted from deep sedimentary environments. Without microbial attenuation in the water column, methane emission to atmosphere from terrestrial mud volcanoes constitutes a significant proportion to the global methane inventory. Microorganisms mediating methane transformation would be particularly enriched in such environments. Their activity, distribution, and diversity involved remain not well-constrained. At Shin-Yan-Ny-Hu Mud Volcanoes (SYNHMV) of southwestern Taiwan, we performed series of measurements and analyses on the pore water and eruptive water samples using geochemical and molecular approaches, in order to determine microbial processes and community assemblages responsible for methane transformation. Geochemical measurements indicated that sulfate depletion was companied with methane increase as the depth increased. Dissolved inorganic carbon (DIC) more depleted in 13C was observed at the depth of sulfate-methane transition zone (SMT, at ~12cm depth) than at other depth intervals. These characteristics of methane, sulfate, and DIC isotope profiles and the presence of ANME-1 sequences showed a high similarity with those of marine sediments, indicating the existence of active anaerobic oxidation of methane (AOM). From bottom to top, the increasing δ13C values of methane with the greatest value occurring in the eruptive surface water suggests methanogenesis and/or methane oxidation over the entire depth range. The contribution of microbial methane could be supported by molecular data of which methanogen-related archaea distributed throughout the entire depths, and the community structures were characterized by Methanosarcinales dominating at shallow depths and Methanomicrobiales dominating in deep sediments. The affinities and activities to substrate addition for methanogenesis appeared to be depth-dependent. Bacterial sequences affiliated with methane

  7. Methane emissions from natural wetlands

    SciTech Connect

    Meyer, J.L.; Burke, R.A. Jr.

    1993-09-01

    Analyses of air trapped in polar ice cores in conjunction with recent atmospheric measurements, indicate that the atmospheric methane concentration increased by about 250% during the past two or three hundred years (Rasmussen and Khalil, 1984). Because methane is a potent ``greenhouse`` gas, the increasing concentrations are expected to contribute to global warning (Dickinson and Cicerone, 1986). The timing of the methane increase suggests that it is related to the rapid growth of the human population and associated industrialization and agricultural development. The specific causes of the atmospheric methane concentration increase are not well known, but may relate to either increases in methane sources, decreases in the strengths of the sinks, or both.

  8. Direct Aromaization of Methane

    SciTech Connect

    George Marcelin

    1997-01-15

    The thermal decomposition of methane offers significant potential as a means of producing higher unsaturated and aromatic hydrocarbons when the extent of reaction is limited. Work in the literature previous to this project had shown that cooling the product and reacting gases as the reaction proceeds would significantly reduce or eliminate the formation of solid carbon or heavier (Clo+) materials. This project studied the effect and optimization of the quenching process as a means of increasing the amount of value added products during the pyrolysis of methane. A reactor was designed to rapidly quench the free-radical combustion reaction so as to maximize the yield of aromatics. The use of free-radical generators and catalysts were studied as a means of lowering the reaction temperature. A lower reaction temperature would have the benefits of more rapid quenching as well as a more feasible commercial process due to savings realized in energy and material of construction costs. It was the goal of the project to identify promising routes from methane to higher hydrocarbons based on the pyrolysis of methane.

  9. Methane Clathrate Hydrate Prospecting

    NASA Technical Reports Server (NTRS)

    Duxbury, N.; Romanovsky, V.

    2003-01-01

    A method of prospecting for methane has been devised. The impetus for this method lies in the abundance of CH4 and the growing shortages of other fuels. The method is intended especially to enable identification of subpermafrost locations where significant amounts of methane are trapped in the form of methane gas hydrate (CH4(raised dot)6H2O). It has been estimated by the U.S. Geological Survey that the total CH4 resource in CH4(raised dot) 6H2O exceeds the energy content of all other fossil fuels (oil, coal, and natural gas from non-hydrate sources). Also, CH4(raised dot)6H2O is among the cleanest-burning fuels, and CH4 is the most efficient fuel because the carbon in CH4 is in its most reduced state. The method involves looking for a proxy for methane gas hydrate, by means of the combination of a thermal-analysis submethod and a field submethod that does not involve drilling. The absence of drilling makes this method easier and less expensive, in comparison with prior methods of prospecting for oil and natural gas. The proposed method would include thermoprospecting in combination with one more of the other non-drilling measurement techniques, which could include magneto-telluric sounding and/or a subsurface-electrical-resistivity technique. The method would exploit the fact that the electrical conductivity in the underlying thawed region is greater than that in the overlying permafrost.

  10. Methane capture from livestock manure.

    PubMed

    Tauseef, S M; Premalatha, M; Abbasi, Tasneem; Abbasi, S A

    2013-03-15

    It has been estimated that livestock manure contributes about 240 million metric tons of carbon dioxide equivalent of methane to the atmosphere and represents one of the biggest anthropogenic sources of methane. Considering that methane is the second biggest contributor to global warming after carbon dioxide, it is imperative that ways and means are developed to capture as much of the anthropogenic methane as possible. There is a major associated advantage of methane capture: its use as a source of energy which is comparable in 'cleanness' to natural gas. The present review dwells upon the traditional ways of methane capture used in India, China, and other developing countries for providing energy to the rural poor. It then reviews the present status of methane capture from livestock manure in developed countries and touches upon the prevalent trends.

  11. Future methane emissions from animals

    SciTech Connect

    Anastasi, C.; Simpson, V.J. )

    1993-04-20

    The authors project future methane emissions from animals to the year 2025. They review the present estimated sources of methane from enteric fermentation in animals. Ruminant animals produce the highest concentrations of methane. Methane is a byproduct of anaerobic breakdown of carbohydrates by microbes in the digestive tract of herbatious animals. In general the methane production depends on the variety of animal, the quality of the feed, and the feeding level. Since cattle, sheep, and buffalo account for roughly 91% of all animal methane emission, they only study these animals in detail. Results suggest a rise in methane production of roughly 1% per year averaged through 2025. Increasing levels are found to originate from developed countries even though the feedstock levels are lower.

  12. Methane hydrate formation in confined nanospace can surpass nature

    NASA Astrophysics Data System (ADS)

    Casco, Mirian E.; Silvestre-Albero, Joaquín; Ramírez-Cuesta, Anibal J.; Rey, Fernando; Jordá, Jose L.; Bansode, Atul; Urakawa, Atsushi; Peral, Inma; Martínez-Escandell, Manuel; Kaneko, Katsumi; Rodríguez-Reinoso, Francisco

    2015-03-01

    Natural methane hydrates are believed to be the largest source of hydrocarbons on Earth. These structures are formed in specific locations such as deep-sea sediments and the permafrost based on demanding conditions of high pressure and low temperature. Here we report that, by taking advantage of the confinement effects on nanopore space, synthetic methane hydrates grow under mild conditions (3.5 MPa and 2 °C), with faster kinetics (within minutes) than nature, fully reversibly and with a nominal stoichiometry that mimics nature. The formation of the hydrate structures in nanospace and their similarity to natural hydrates is confirmed using inelastic neutron scattering experiments and synchrotron X-ray powder diffraction. These findings may be a step towards the application of a smart synthesis of methane hydrates in energy-demanding applications (for example, transportation).

  13. Methane hydrate formation in confined nanospace can surpass nature.

    PubMed

    Casco, Mirian E; Silvestre-Albero, Joaquín; Ramírez-Cuesta, Anibal J; Rey, Fernando; Jordá, Jose L; Bansode, Atul; Urakawa, Atsushi; Peral, Inma; Martínez-Escandell, Manuel; Kaneko, Katsumi; Rodríguez-Reinoso, Francisco

    2015-03-02

    Natural methane hydrates are believed to be the largest source of hydrocarbons on Earth. These structures are formed in specific locations such as deep-sea sediments and the permafrost based on demanding conditions of high pressure and low temperature. Here we report that, by taking advantage of the confinement effects on nanopore space, synthetic methane hydrates grow under mild conditions (3.5 MPa and 2 °C), with faster kinetics (within minutes) than nature, fully reversibly and with a nominal stoichiometry that mimics nature. The formation of the hydrate structures in nanospace and their similarity to natural hydrates is confirmed using inelastic neutron scattering experiments and synchrotron X-ray powder diffraction. These findings may be a step towards the application of a smart synthesis of methane hydrates in energy-demanding applications (for example, transportation).

  14. Methane hydrate formation in confined nanospace can surpass nature.

    PubMed

    Casco, Mirian E; Silvestre-Albero, Joaquín; Ramírez-Cuesta, Anibal J; Rey, Fernando; Jordá, Jose L; Bansode, Atul; Urakawa, Atsushi; Peral, Inma; Martínez-Escandell, Manuel; Kaneko, Katsumi; Rodríguez-Reinoso, Francisco

    2015-01-01

    Natural methane hydrates are believed to be the largest source of hydrocarbons on Earth. These structures are formed in specific locations such as deep-sea sediments and the permafrost based on demanding conditions of high pressure and low temperature. Here we report that, by taking advantage of the confinement effects on nanopore space, synthetic methane hydrates grow under mild conditions (3.5 MPa and 2 °C), with faster kinetics (within minutes) than nature, fully reversibly and with a nominal stoichiometry that mimics nature. The formation of the hydrate structures in nanospace and their similarity to natural hydrates is confirmed using inelastic neutron scattering experiments and synchrotron X-ray powder diffraction. These findings may be a step towards the application of a smart synthesis of methane hydrates in energy-demanding applications (for example, transportation). PMID:25728378

  15. Natural Methane and Carbon Dioxide Hydrates in the Earth System

    NASA Astrophysics Data System (ADS)

    Research Team; Milkereit, B.

    2004-05-01

    Both CH4 and CO2 are abundant volatiles in the earth's crust. Methane hydrates occur in permafrost regions and continental slopes of oceans. It is currently estimated that the energy stored in CH4 hydrate reserves totals more than twice the global reserves of all conventional oil, gas, and coal deposits combined. This means that methane hydrate could prove to be a very important source of energy in the future. Pressure versus temperature phase diagrams for methane and carbon dioxide define characteristic stability fields for gas, fluid and hydrates states. Sequestration of carbon dioxide in the earths crust and production of methane hydrate reservoirs are critically dependent on knowledge of the in situ elastic moduli of natural hydrates. The physical properties of simple methane and carbon dioxide hydrates are similar [1]. Our compilation of experimental data confirms high compressional wave velocities and elastic moduli for CH4 and CO2 hydrates and low compressional wave velocities for the fluid and gas phases. As methane and carbon dioxide hydrates are stable over similar pressure-temperature ranges, the two types of hydrates form in similar settings in the earth's crust. For example, temperature and pressure conditions in deepwater marine environments require both CO2 and CH4 to be in hydrate phase. However, not much is known about the origin, distribution and total volume of natural carbon dioxide hydrates stored in the earth's crust. For a number of tectonic/geological settings, CO2-rich fluids from deep crustal reservoirs must be considered: rifted margins, volcanic arcs, deepwater vents [2], mud volcanoes and mud diapirs [3]. Both methane and carbon dioxide hydrates work to cement sea floors in similar ways. Slope failure, a phenomenon usually taken as a hallmark of the presence of methane hydrate, could also be attributed to the existence of carbon dioxide hydrates. Perhaps most critically, many of the estimations of the amounts of methane hydrates are

  16. Deep Carbon Cycling in the Deep Hydrosphere: Abiotic Organic Synthesis and Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Sherwood Lollar, B.; Sutcliffe, C. N.; Ballentine, C. J.; Warr, O.; Li, L.; Ono, S.; Wang, D. T.

    2014-12-01

    Research into the deep carbon cycle has expanded our understanding of the depth and extent of abiotic organic synthesis in the deep Earth beyond the hydrothermal vents of the deep ocean floor, and of the role of reduced gases in supporting deep subsurface microbial communities. Most recently, this research has expanded our understanding not only of the deep biosphere but the deep hydrosphere - identifying for the first time the extreme antiquity (millions to billions of years residence time) of deep saline fracture waters in the world's oldest rocks. Energy-rich saline fracture waters in the Precambrian crust that makes up more than 70% of the Earth's continental lithosphereprovide important constraints on our understanding of the extent of the crust that is habitable, on the time scales of hydrogeologic isolation (and conversely mixing) of fluids relevant to the deep carbon cycle, and on the geochemistry of substrates that sustain both abiotic organic synthesis and biogeochemical cycles driven by microbial communities. Ultimately the chemistry and hydrogeology of the deep hydrosphere will help define the limits for life in the subsurface and the boundary between the biotic-abiotic fringe. Using a variety of novel techniques including noble gas analysis, clumped isotopologues of methane, and compound specific isotope analysis of CHNOS, this research is addressing questions about the distribution of deep saline fluids in Precambrian rocks worldwide, the degree of interconnectedness of these potential biomes, the habitability of these fluids, and the biogeographic diversity of this new realm of the deep hydrosphere.

  17. Deep learning

    NASA Astrophysics Data System (ADS)

    Lecun, Yann; Bengio, Yoshua; Hinton, Geoffrey

    2015-05-01

    Deep learning allows computational models that are composed of multiple processing layers to learn representations of data with multiple levels of abstraction. These methods have dramatically improved the state-of-the-art in speech recognition, visual object recognition, object detection and many other domains such as drug discovery and genomics. Deep learning discovers intricate structure in large data sets by using the backpropagation algorithm to indicate how a machine should change its internal parameters that are used to compute the representation in each layer from the representation in the previous layer. Deep convolutional nets have brought about breakthroughs in processing images, video, speech and audio, whereas recurrent nets have shone light on sequential data such as text and speech.

  18. Deep learning.

    PubMed

    LeCun, Yann; Bengio, Yoshua; Hinton, Geoffrey

    2015-05-28

    Deep learning allows computational models that are composed of multiple processing layers to learn representations of data with multiple levels of abstraction. These methods have dramatically improved the state-of-the-art in speech recognition, visual object recognition, object detection and many other domains such as drug discovery and genomics. Deep learning discovers intricate structure in large data sets by using the backpropagation algorithm to indicate how a machine should change its internal parameters that are used to compute the representation in each layer from the representation in the previous layer. Deep convolutional nets have brought about breakthroughs in processing images, video, speech and audio, whereas recurrent nets have shone light on sequential data such as text and speech.

  19. Deep learning.

    PubMed

    LeCun, Yann; Bengio, Yoshua; Hinton, Geoffrey

    2015-05-28

    Deep learning allows computational models that are composed of multiple processing layers to learn representations of data with multiple levels of abstraction. These methods have dramatically improved the state-of-the-art in speech recognition, visual object recognition, object detection and many other domains such as drug discovery and genomics. Deep learning discovers intricate structure in large data sets by using the backpropagation algorithm to indicate how a machine should change its internal parameters that are used to compute the representation in each layer from the representation in the previous layer. Deep convolutional nets have brought about breakthroughs in processing images, video, speech and audio, whereas recurrent nets have shone light on sequential data such as text and speech. PMID:26017442

  20. Solid methane on Triton and Pluto - 3- to 4-micron spectrophotometry

    NASA Technical Reports Server (NTRS)

    Spencer, John R.; Buie, Marc W.; Bjoraker, Gordon L.

    1990-01-01

    Methane has been identified in the Pluto/Charon system on the basis of absorption features in the reflectance spectrum at 1.5 and 2.3 microns; attention is presently given to observations of a 3.25 micron-centered deep absorption feature in Triton and Pluto/Charon system reflectance spectra. This absorption may indicate the presence of solid methane, constituting either the dominant surface species or a mixture with a highly transparent substance, such as N2 frost.

  1. Low-level 14C methane oxidation rate measurements modified for remote field settings

    NASA Astrophysics Data System (ADS)

    Pack, M. A.; Pohlman, J.; Ruppel, C. D.; Xu, X.

    2012-12-01

    Aerobic methane oxidation limits atmospheric methane emissions from degraded subsea permafrost and dissociated methane hydrates in high latitude oceans. Methane oxidation rate measurements are a crucial tool for investigating the efficacy of this process, but are logistically challenging when working on small research vessels in remote settings. We modified a low-level 14C-CH4 oxidation rate measurement for use in the Beaufort Sea above hydrate bearing sediments during August 2012. Application of the more common 3H-CH4 rate measurement that uses 106 times more radioactivity was not practical because the R/V Ukpik cannot accommodate a radiation van. The low-level 14C measurement does not require a radiation van, but careful isolation of the 14C-label is essential to avoid contaminating natural abundance 14C measurements. We used 14C-CH4 with a total activity of 1.1 μCi, which is far below the 100 μCi permitting level. In addition, we modified field procedures to simplify and shorten sample processing. The original low-level 14C-CH4 method requires 6 steps in the field: (1) collect water samples in glass serum bottles, (2) inject 14C-CH4 into bottles, (3) incubate for 24 hours, (4) filter to separate the methanotrophic bacterial cells from the aqueous sample, (5) kill the filtrate with sodium hydroxide (NaOH), and (6) purge with nitrogen to remove unused 14C-CH4. Onshore, the 14C-CH4 respired to carbon dioxide or incorporated into cell material by methanotrophic bacteria during incubation is quantified by accelerator mass spectrometry (AMS). We conducted an experiment to test the possibility of storing samples for purging and filtering back onshore (steps 4 and 6). We subjected a series of water samples to steps 1-3 & 5, and preserved with mercuric chloride (HgCl2) instead of NaOH because HgCl2 is less likely to break down cell material during storage. The 14C-content of the carbon dioxide in samples preserved with HgCl2 and stored for up to 2 weeks was stable

  2. Resource Assessment of Methane Hydrate in the Eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Fujii, T.; Saeki, T.; Kobayashi, T.; Inamori, T.; Hayashi, M.; Takano, O.

    2007-12-01

    Resource assessment of methane hydrate (MH) in the eastern Nankai Trough was conducted through probabilistic approach using 2D/3D seismic survey data and drilling survey data from METI exploratory test wells 'Tokai-oki to Kumano-nada' [1, 2, 3]. We have extracted several prospective 'MH concentrated zones' [4] characterized by high resistivity in well log, strong seismic reflector, seismic high velocity, and turbidite deposit delineated by sedimentary facies analysis. The amount of methane gas contained in MH bearing layers was calculated using volumetric method for each zone. Each parameter, such as Gross Rock Volume (GRV), net-to-gross ratio (N/G), MH pore saturation (Sh), porosity, cage occupancy, and volume ratio was given as probabilistic distribution for Monte Carlo simulation, considering the uncertainly of these values. The GRV for each hydrate bearing zones was calculated from both strong seismic amplitude anomaly and velocity anomaly. Time-to-depth conversion was conducted using interval velocity derived from SVWD (Seismic Vision While Drilling). Risk factor was applied for the estimation of the GRV in 2D seismic area considering the uncertainty of seismic interpretation. The N/G was determined based on the relationship between LWD (Logging While Drilling) resistivity and grain size in zones with existing wells. 3ohm-m was used for typical cut off value to determine net intervals. Seismic facies map created by sequence stratigraphic approach [5] was also used for the determination of the N/G in zone without well controls. Porosity was estimated using density log, together with calibration by core analysis. The Sh was estimated by the combination of density log and NMR log (DMR method), together with the calibration by observed gas volume from onboard MH dissociation tests using PTCS (Pressure Temperature Core Sampler) [6]. The Sh in zone without well control was estimated using relationship between seismic P-wave interval velocity and Sh from NMR log at

  3. Project identification for methane reduction options

    SciTech Connect

    Kerr, T.

    1996-12-31

    This paper discusses efforts directed at reduction in emission of methane to the atmosphere. Methane is a potent greenhouse gas, which on a 20 year timeframe may present a similar problem to carbon dioxide. In addition, methane causes additional problems in the form of smog and its longer atmospheric lifetime. The author discusses strategies for reducing methane emission from several major sources. This includes landfill methane recovery, coalbed methane recovery, livestock methane reduction - in the form of ruminant methane reduction and manure methane recovery. The author presents examples of projects which have implemented these ideas, the economics of the projects, and additional gains which come from the projects.

  4. Methane from acetate.

    PubMed

    Ferry, J G

    1992-09-01

    The general features are known for the pathway by which most methane is produced in nature. All acetate-utilizing methanogenic microorganisms contain CODH which catalyzes the cleavage of acetyl-CoA; however, the pathway differs from all other acetate-utilizing anaerobes in that the methyl group is reduced to methane with electrons derived from oxidation of the carbonyl group of acetyl-CoA to CO2. The current understanding of the methanogenic fermentation of acetate provides impressions of nature's novel solutions to problems of methyl transfer, electron transport, and energy conservation. The pathway is now at a level of understanding that will permit productive investigations of these and other interesting questions in the near future. PMID:1512186

  5. Coal Bed Methane Primer

    SciTech Connect

    Dan Arthur; Bruce Langhus; Jon Seekins

    2005-05-25

    During the second half of the 1990's Coal Bed Methane (CBM) production increased dramatically nationwide to represent a significant new source of income and natural gas for many independent and established producers. Matching these soaring production rates during this period was a heightened public awareness of environmental concerns. These concerns left unexplained and under-addressed have created a significant growth in public involvement generating literally thousands of unfocused project comments for various regional NEPA efforts resulting in the delayed development of public and fee lands. The accelerating interest in CBM development coupled to the growth in public involvement has prompted the conceptualization of this project for the development of a CBM Primer. The Primer is designed to serve as a summary document, which introduces and encapsulates information pertinent to the development of Coal Bed Methane (CBM), including focused discussions of coal deposits, methane as a natural formed gas, split mineral estates, development techniques, operational issues, producing methods, applicable regulatory frameworks, land and resource management, mitigation measures, preparation of project plans, data availability, Indian Trust issues and relevant environmental technologies. An important aspect of gaining access to federal, state, tribal, or fee lands involves education of a broad array of stakeholders, including land and mineral owners, regulators, conservationists, tribal governments, special interest groups, and numerous others that could be impacted by the development of coal bed methane. Perhaps the most crucial aspect of successfully developing CBM resources is stakeholder education. Currently, an inconsistent picture of CBM exists. There is a significant lack of understanding on the parts of nearly all stakeholders, including industry, government, special interest groups, and land owners. It is envisioned the Primer would being used by a variety of

  6. Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.

    PubMed

    Drake, Henrik; Åström, Mats E; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C (δ13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  7. Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.

    PubMed

    Drake, Henrik; Åström, Mats E; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-05-07

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C (δ13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane.

  8. Extreme 13C depletion of carbonates formed during oxidation of biogenic methane in fractured granite

    PubMed Central

    Drake, Henrik; Åström, Mats E.; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C (δ13C as light as −69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to −125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  9. Deep Lysimeter

    DOEpatents

    Hubbell, Joel M.; Sisson, James B.

    2004-06-01

    A deep lysimeter including a hollow vessel having a chamber, a fill conduit extending into the chamber through apertures, a semi-permeable member mounted on the vessel and in fluid communication with the fill conduit, and a line connection for retrieving the lysimeter.

  10. Deep Trouble.

    ERIC Educational Resources Information Center

    Popke, Michael

    2002-01-01

    Discusses how the safety-related ruling by the National Federation of State High School Associations to eliminate the option of using 18-inch starting platforms in pools less than 4 feet deep may affect operators of swimming pools and the swim teams who use them. (EV)

  11. 49 new T dwarfs identified using methane imaging

    NASA Astrophysics Data System (ADS)

    Cardoso, C. V.; Burningham, B.; Smart, R. L.; van Spaandonk, L.; Baker, D.; Smith, L. C.; Zhang, Z. H.; Andrei, A. H.; Bucciarelli, B.; Dhital, S.; Jones, H. R. A.; Lattanzi, M. G.; Magazzú, A.; Pinfield, D. J.; Tinney, C. G.

    2015-07-01

    We present the discovery of 49 new photometrically classified T dwarfs from the combination of large infrared and optical surveys combined with follow-up Telescopio Nazionale Galileo photometry. We used multiband infrared and optical photometry from the United Kingdom Infrared Telescope and Sloan Digital Sky Surveys to identify possible brown dwarf candidates, which were then confirmed using methane filter photometry. We have defined a new photometric conversion between CH4s - CH4l colour and spectral type for T4-T8 brown dwarfs based on a part of the sample that has been followed up using methane photometry and spectroscopy. Using methane differential photometry as a proxy for spectral type for T dwarfs has proved to be a very efficient technique. Of a subset of 45 methane selected brown dwarfs that were observed spectroscopically, 100 per cent were confirmed as T dwarfs. Future deep imaging surveys will produce large samples of faint brown dwarf candidates, for which spectroscopy will not be feasible. When broad wavelength coverage is unavailable, methane imaging offers a means to efficiently classify candidates from such surveys using just a pair of near-infrared images.

  12. X-ray Computed Tomography Observation of Methane Hydrate Dissociation

    USGS Publications Warehouse

    Tomutsa, L.; Freifeld, B.; Kneafsey, T.J.; Stern, L.A.

    2002-01-01

    Deposits of naturally occurring methane hydrate have been identified in permafrost and deep oceanic environments with global reserves estimated to be twice the total amount of energy stored in fossil fuels. The fundamental behavior of methane hydrate in natural formations, while poorly understood, is of critical importance if the economic recovery of methane from hydrates is to be accomplished. In this study, computed X-ray tomography (CT) scanning is used to image an advancing dissociation front in a heterogeneous gas hydrate/sand sample at 0.1 MPa. The cylindrical methane hydrate and sand aggregate, 2.54 cm in diameter and 6.3 cm long, was contained in a PVC sample holder that was insulated on all but one end. At the uninsulated end, the dissociated gas was captured and the volume of gas monitored. The sample was initially imaged axially using X-ray CT scanning within the methane hydrate stability zone by keeping the sample temperature at 77??K. Subsequently, as the sample warmed through the methane hydrate dissociation point at 194??K and room pressure, gas was produced and the temperature at the bottom of the sample plug was monitored while CT images were acquired. The experiment showed that CT imaging can resolve the reduction in density (as seen by a reduction in beam attenuation) of the hydrate/sand aggregate due to the dissociation of methane hydrate. In addition, a comparison of CT images with gas flow and temperature measurements reveals that the CT scanner is able to resolve accurately and spatially the advancing dissociation front. Future experiments designed to better understand the thermodynamics of hydrate dissociation are planned to take advantage of the temporal and spatial resolution that the CT scanner provides.

  13. The distribution of methane in groundwater in Alberta (Canada) and associated aqueous geochemistry conditions

    NASA Astrophysics Data System (ADS)

    Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Millot, Romain; Kloppmann, Wolfram

    2016-04-01

    Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish: (a) natural in-situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. We have conducted a NSERC-ANR co-funded baseline study investigating the occurrence of methane in shallow groundwater of Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. Our objective was to assess the occurrence and sources of methane in shallow groundwaters and to also characterize the hydrochemical environment in which the methane was formed or transformed through redox processes. Ultimately our aim was to determine whether methane was formed in-situ or whether it migrated from deeper formations into shallow aquifers. Combining hydrochemical and dissolved and free geochemical gas data from 372 groundwater samples obtained from 186 monitoring wells of the provincial groundwater observation well network (GOWN) in Alberta, it was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of dissolved biogenic methane (> 0.01 mM or > 0.2 mg/L), characterized by δ13CCH4 values < -55‰, occurred in anoxic Na-Cl, Na-HCO3 and Na-HCO3-Cl type groundwater with negligible concentrations of nitrate and sulfate suggesting that methane was formed in-situ under methanogenic conditions consistent with the redox ladder concept. Despite quite variable gas concentrations and a

  14. Kansas coal distribution, resources, and potential for coalbed methane

    USGS Publications Warehouse

    Brady, L.L.

    2000-01-01

    Kansas has large amounts of bituminous coal both at the surface and in the subsurface of eastern Kansas. Preliminary studies indicate at least 53 billion tons (48 billion MT) of deep coal [>100 ft (>30 m)] determined from 32 different coal beds. Strippable coal resources at a depth < 100 ft (<30 m) total 2.8 billion tons (2.6 billion MT), and this total is determined from 17 coals. Coal beds present in the Cherokee Group (Middle Pennsylvanian) represent most of these coal resource totals. Deep coal beds with the largest resource totals include the Bevier, Mineral, "Aw" (unnamed coal bed), Riverton, and Weir-Pittsburg coals, all within the Cherokee Group. Based on chemical analyses, coals in the southeastern part of the state are generally high volatile A bituminous, whereas coals in the east-central and northeastern part of the state are high-volatile B bituminous coals. The primary concern of coal beds in Kansas for deep mining or development of coalbed methane is the thin nature [<2 ft (0.6 m)] of most coal beds. Present production of coalbed methane is centered mainly in the southern Wilson/northern Montgomery County area of southeastern Kansas where methane is produced from the Mulky, Weir-Pittsburg, and Riverton coals.

  15. Evidence for nitrite-dependent anaerobic methane oxidation as a previously overlooked microbial methane sink in wetlands.

    PubMed

    Hu, Bao-lan; Shen, Li-dong; Lian, Xu; Zhu, Qun; Liu, Shuai; Huang, Qian; He, Zhan-fei; Geng, Sha; Cheng, Dong-qing; Lou, Li-ping; Xu, Xiang-yang; Zheng, Ping; He, Yun-feng

    2014-03-25

    The process of nitrite-dependent anaerobic methane oxidation (n-damo) was recently discovered and shown to be mediated by "Candidatus Methylomirabilis oxyfera" (M. oxyfera). Here, evidence for n-damo in three different freshwater wetlands located in southeastern China was obtained using stable isotope measurements, quantitative PCR assays, and 16S rRNA and particulate methane monooxygenase gene clone library analyses. Stable isotope experiments confirmed the occurrence of n-damo in the examined wetlands, and the potential n-damo rates ranged from 0.31 to 5.43 nmol CO2 per gram of dry soil per day at different depths of soil cores. A combined analysis of 16S rRNA and particulate methane monooxygenase genes demonstrated that M. oxyfera-like bacteria were mainly present in the deep soil with a maximum abundance of 3.2 × 10(7) gene copies per gram of dry soil. It is estimated that ∼0.51 g of CH4 m(-2) per year could be linked to the n-damo process in the examined wetlands based on the measured potential n-damo rates. This study presents previously unidentified confirmation that the n-damo process is a previously overlooked microbial methane sink in wetlands, and n-damo has the potential to be a globally important methane sink due to increasing nitrogen pollution. PMID:24616523

  16. Methane/nitrogen separation process

    DOEpatents

    Baker, R.W.; Lokhandwala, K.A.; Pinnau, I.; Segelke, S.

    1997-09-23

    A membrane separation process is described for treating a gas stream containing methane and nitrogen, for example, natural gas. The separation process works by preferentially permeating methane and rejecting nitrogen. The authors have found that the process is able to meet natural gas pipeline specifications for nitrogen, with acceptably small methane loss, so long as the membrane can exhibit a methane/nitrogen selectivity of about 4, 5 or more. This selectivity can be achieved with some rubbery and super-glassy membranes at low temperatures. The process can also be used for separating ethylene from nitrogen. 11 figs.

  17. Methane/nitrogen separation process

    DOEpatents

    Baker, Richard W.; Lokhandwala, Kaaeid A.; Pinnau, Ingo; Segelke, Scott

    1997-01-01

    A membrane separation process for treating a gas stream containing methane and nitrogen, for example, natural gas. The separation process works by preferentially permeating methane and rejecting nitrogen. We have found that the process is able to meet natural gas pipeline specifications for nitrogen, with acceptably small methane loss, so long as the membrane can exhibit a methane/nitrogen selectivity of about 4, 5 or more. This selectivity can be achieved with some rubbery and super-glassy membranes at low temperatures. The process can also be used for separating ethylene from nitrogen.

  18. On methane pyrolysis special applications

    NASA Astrophysics Data System (ADS)

    Toncu, D. C.; Toncu, G.; Soleimani, S.

    2015-11-01

    Methane pyrolysis represents one of the most important processes in industrial use, with applications rising from the chemical and petrochemical industry, combustion, materials and protective coatings. Despite the intense research, experimental data lack kinetic aspects, and the thermodynamics involved often leads to inaccurate results when applied to various systems. Carrying out a comparative analysis of several available data on methane pyrolysis, the paper aims to study the phenomenon of methane pyrolysis under different environments (combustion and plasma), concluding on the most possible reaction pathways involved in many of its applications. Computer simulation using different database underlines the conclusion, helping to the understanding of methane pyrolysis importance in future technologies.

  19. Redefining the isotopic boundaries of biogenic methane: Methane from endoevaporites

    NASA Astrophysics Data System (ADS)

    Tazaz, Amanda M.; Bebout, Brad M.; Kelley, Cheryl A.; Poole, Jennifer; Chanton, Jeffrey P.

    2013-06-01

    The recent reports of methane in the atmosphere of Mars, as well as the findings of hypersaline paleoenvironments on that planet, have underscored the need to evaluate the importance of biological (as opposed to geological) trace gas production and consumption, particularly in hypersaline environments. Methane in the atmosphere of Mars may be an indication of extant life, but it may also be a consequence of geologic activity and/or the thermal alteration of ancient organic matter. On Earth these methane sources can be distinguished using stable isotopic analyses and the ratio of methane (C1) to C2 and C3 alkanes present in the gas source (C1/(C2 + C3)). We report here that methane produced in hypersaline environments on Earth has an isotopic composition and alkane content outside the values presently considered to indicate a biogenic origin. Methane-rich bubbles released from sub-aqueous substrates contained δ13CCH4 and δ2HCH4 values ranging from -65‰ to -35‰ and -350‰ to -140‰ respectively. Higher salinity endoevaporites yielded what would be considered non-biogenic methane based upon stable isotopic and alkane content, however incubation of crustal and algal mat samples resulted in methane production with similar isotopic values. Radiocarbon analysis indicated that the production of the methane was from recently fixed carbon. An extension of the isotopic boundaries of biogenic methane is necessary in order to avoid the possibility of false negatives returned from measurements of methane on Mars and other planetary bodies.

  20. Assessing Methane Migration Mechanisms at Walker Ridge, Gulf of Mexico, via 3D Methane Hydrate Reservoir Modeling

    NASA Astrophysics Data System (ADS)

    Nole, M.; Daigle, H.; Mohanty, K. K.; Hillman, J. I. T.; Cook, A.

    2015-12-01

    structure, we show that even with deep advective sourcing of methane, local hydrate accumulations can be sourced advectively or diffusively. Advectively sourced hydrates accumulate evenly in highly permeable strata, while diffusively sourced hydrates are characterized by thin strata-bound intervals of high clay-sand pore size contrasts.

  1. Geological emission of methane from the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China.

    PubMed

    Tang, Junhong; Bao, Zhengyu; Xiang, Wu; Gou, Qinghong

    2008-01-01

    A static flux chamber method was applied to study natural emissions of methane into the atmosphere in the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China. Using an online method, which couples a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS) together, the 13C/12C ratios of methane in the flux chambers were measured. The results demonstrated that methane gases were liable to migrate from deep oil/gas reservoir to the surface through microseepage and pervasion, and that a part of the migrated methane that remained unoxidized could emit into the atmosphere. Methane emission rates varied less in the oil/gas field because the whole region was homogeneous in geology and geography, with a standard deviation of less than 0.02 mg/(m2 x h). These were the differences in methane emission flux in the day and at night in the oil/gas field. The maximum methane emission flux reached 0.15 mg/(m2 x h) at 5:00-6:00 early in the morning, and then decreased gradually. The minimum was shown 0.10 mg/(m2 x h) at 17:00-18:00 in the afternoon, and then increased gradually. The daily methane released flux of the study area was 2.89 mg/(m2 x d), with a standard deviation of 0.43 mg/(m2 x d), using the average methane flux of every hour in a day for all chambers. delta13C of methane increased with the increase of methane concentration in the flux chambers, further indicating that the pyrogenetic origin of methane was come from deep oil/gas reservoirs.

  2. Consumption of atmospheric methane by tundra soils

    NASA Technical Reports Server (NTRS)

    Whalen, S. C.; Reeburgh, W. S.

    1990-01-01

    The results of field and laboratory experiments on methane consumption by tundra soils are reported. For methane concentrations ranging from below to well above ambient, moist soils are found to consume methane rapidly; in nonwaterlogged soils, equilibration with atmospheric methane is fast relative to microbial oxidation. It is concluded that lowering of the water table in tundra as a resulting from a warmer, drier climate will decrease methane fluxes and could cause these areas to provide negative feedback for atmospheric methane.

  3. Community Structure of Methane-Cycling Archaea in Different Geochemical Zones in Aarhus Bay, Denmark

    NASA Astrophysics Data System (ADS)

    Chen, X.; Lever, M. A.; Saunders, A. M.; Jørgensen, B. B.

    2014-12-01

    Methanogenesis and anaerobic oxidation of methane are dominant processes regulating methane cycle in the deep biosphere in marine environments, both of which are executed by microbes. The diversity of methane-cycling archaea has been intensively studied by exploring 16S ribosomal RNA gene and alpha subunit of methyl coenzyme M reductase gene (mcrA). In marine sediments, methanogens and methane-oxidizing archaea are mainly found in methane zone (MZ) and in sulfate-methane transition zone (SMTZ), respectively. However, methane-cycling archaea are also present in zones other than their usual residing geochemical zones. Next generation sequencing of mcrA genes from 5 gravity cores shows that both methanogens and methane-oxidizing archaeal group - ANME-1 are ubiquitous in all biogeochemical zones in Aarhus Bay. We will further discuss below questions: which methanogens and methanotrophs are present and active in the presence of sulfate, and which are restricted in SMTZ or MZ? How do activity and pathway of methanogenesis / methanotrophy change with depth and substrate availability?

  4. Methane emissions from canopy wetlands

    NASA Astrophysics Data System (ADS)

    Martinson, G. O.; Conrad, R.

    2012-12-01

    Ground wetlands are the main natural source of methane but they fail to explain the observed amounts of methane over tropical forests. Bromeliad tanks are discrete habitats for aquatic organisms and up to several thousand of bromeliad individuals per hectare of tropical forest create a unique canopy wetland ecosystem in neotropical forests. Recently, we have discovered that canopy wetlands inhabit methanogenic archaea, emit substantial amounts of methane and may help to explain the high amounts of methane over neotropical forests. However, the pathway of methane formation and potential methane production in canopy wetlands of different tropical forest ecosystems have not yet been studied. In this study, we investigated the stable carbon isotope fractionation, methanogenic pathway and potential methane production of bromeliad tanks along an elevation gradient in neotropical forests for the first time. We sampled the bromeliad tank-substrate of 3 tank bromeliads per functional type and elevation (1000 m, 2000 m and 3000 m above the sea level). We distinguished three functional types of tank bromeliads, based on plant architecture and ecological niche preference. Functional type I-tank bromeliads are concentrated in the understory and on the ground. Functional type II and type III are concentrated in the mid and overstory. We conducted tank-substrate incubation experiments and measured CH4, CO2, 13CH4 and 13CO2 at regular time intervals during the incubation period. The methane production potential of bromeliad tanks correlated positively with tank-substrate carbon concentration and decreased with increasing canopy height and increasing elevation. The dominant pathway of methane formation in bromeliad tanks was hydrogenotrophic methanogenesis (>50%) and this dominance increased with increasing canopy height and increasing elevation. Our results provide novel insights into the pathway of methane formation in neotropical canopy wetlands and suggest that canopy height is

  5. Hypotheses for a Near-Surface Reservoir of Methane and Its Release on Mars

    NASA Astrophysics Data System (ADS)

    Hu, R.; Bloom, A. A.; Gao, P.; Miller, C. E.; Yung, Y. L.

    2015-12-01

    The Curiosity rover recently detected a background of 0.7 ppb and spikes of 7 ppb of methane on Mars. This in situ measurement reorients our understanding of the Martian environment and its potential for life, as the current theories do not entail any active source or sink of methane. In particular, the 10-fold elevation during the southern winter indicates episodic sources of methane that are yet to be discovered. Using the temperature and humidity measurements from the rover, we find that perchlorate salts in the regolith deliquesce to form liquid solutions, and deliquescence progresses to deeper subsurface in the season of the methane spikes. We therefore formulate the following three testable hypotheses as an attempt to explain the apparent variability of the atmospheric methane abundance. The first scenario is that the regolith in Gale Crater adsorbs methane when dry and releases this methane to the atmosphere upon deliquescence. The adsorption energy needs to be 36 kJ mol-1 to explain the magnitude of the methane spikes, higher than laboratory measurements. The second scenario is that microorganisms exist and convert organic matter in the soil to methane when they are in liquid solutions. This scenario does not require regolith adsorption. The third scenario is that deep subsurface aquifers sealed by ice or clathrate produce bursts of methane as a result of freezing and thawing of the permafrost, as the terrestrial arctic tundra. Continued monitoring of methane by Curiosity will test the existence of the near-surface reservoir and its exchange with the atmosphere.

  6. Methane related changes in prokaryotic activity along geochemical profiles in sediments of Lake Kinneret (Israel)

    NASA Astrophysics Data System (ADS)

    Bar Or, I.; Ben-Dov, E.; Kushmaro, A.; Eckert, W.; Sivan, O.

    2014-06-01

    Microbial methane oxidation process (methanotrophy) is the primary control on the emission of the greenhouse gas methane (CH4) to the atmosphere. In terrestrial environments, aerobic methanotrophic bacteria are mainly responsible for oxidizing the methane. In marine sediments the coupling of the anaerobic oxidation of methane (AOM) with sulfate reduction, often by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria, was found to consume almost all the upward diffusing methane. Recently, we showed geochemical evidence for AOM driven by iron reduction in Lake Kinneret (LK) (Israel) deep sediments and suggested that this process can be an important global methane sink. The goal of the present study was to link the geochemical gradients found in the porewater (chemical and isotope profiles) with possible changes in microbial community structure. Specifically, we examined the possible shift in the microbial community in the deep iron-driven AOM zone and its similarity to known sulfate driven AOM populations. Screening of archaeal 16S rRNA gene sequences revealed Thaumarchaeota and Euryarchaeota as the dominant phyla in the sediment. Thaumarchaeota, which belongs to the family of copper containing membrane-bound monooxgenases, increased with depth while Euryarchaeota decreased. This may indicate the involvement of Thaumarchaeota, which were discovered to be ammonia oxidizers but whose activity could also be linked to methane, in AOM in the deep sediment. ANMEs sequences were not found in the clone libraries, suggesting that iron-driven AOM is not through sulfate. Bacterial 16S rRNA sequences displayed shifts in community diversity with depth. Proteobacteria and Chloroflexi increased with depth, which could be connected with their different dissimilatory anaerobic processes. The observed changes in microbial community structure suggest possible direct and indirect mechanisms for iron-driven AOM in deep sediments.

  7. Resistivity structure of the Del Mar methane seep.

    NASA Astrophysics Data System (ADS)

    Kannberg, P. K.; Constable, S.

    2015-12-01

    In March of 2015 we mapped the resistivity structure of the Del Mar methane seep in the inner California borderlands using a deep towed electromagnetic (EM) source and receiver array. Located in the San Diego trough at a depth of 1km, the seep site is on the flank of a mound associated with a transpressive step in the San Diego trough fault. The seep site has previously been associated with seafloor pockmarks, acoustic wipeouts, chemosynthetic communities, and active methane bubble venting. Controlled source electromagnetic (CSEM) surveys are performed by deep-towing an EM source that is transmitting a known signal; this signal is detected by towed receivers. This transmitted signal is altered by the electrical properties of the surrounding environment. Compared to seismic methods, EM methods are largely insensitive to free gas, making it an especially useful tool for detecting electrically resistive methane hydrate in areas of active gas venting. We used a 50m dipole transmitting 100A, with 3-axis electric field receivers spaced at 130m, 230m, 330m, and 430m behind the transmitter dipole center. The receiver data are inverted using MARE2DEM, a finite element 2D inversion routine. The inversion results show the background resistivity of the trough sediments to be about 1-2 ohmm, and are largely featureless outside of the seep site. However at the seep site we see a decanter-shaped 100 ohmm resistor whose base is 100m below the seafloor, and 1km wide at its widest. This feature narrows at the top to form a pipe structure about 200m wide that extends to the seafloor. These resistive structures are interpreted to be methane hydrate resulting from methane rich fluid flow along faults associated with the transpressional system that brackets the seep site.

  8. Shallow Aquifer Methane Gas Source Assessment

    NASA Astrophysics Data System (ADS)

    Coffin, R. B.; Murgulet, D.; Rose, P. S.; Hay, R.

    2014-12-01

    Shale gas can contribute significantly to the world's energy demand. Hydraulic fracturing (fracking) on horizontal drill lines developed over the last 15 years makes formerly inaccessible hydrocarbons economically available. From 2000 to 2035 shale gas is predicted to rise from 1% to 46% of the total natural gas for the US. A vast energy resource is available in the United States. While there is a strong financial advantage to the application of fracking there is emerging concern about environmental impacts to groundwater and air quality from improper shale fracking operations. Elevated methane (CH4) concentrations have been observed in drinking water throughout the United States where there is active horizontal drilling. Horizontal drilling and hydraulic-fracturing can increase CH4 transport to aquifers, soil and the vadose zone. Seepage can also result from casing failure in older wells. However, there is strong evidence that elevated CH4 concentrations can be associated with topographic and hydrogeologic features, rather than shale-gas extraction processes. Carbon isotope geochemistry can be applied to study CH4source(s) in shallow vadose zone and groundwater systems. A preliminary TAMU-CC isotope data set from samples taken at different locations in southern Texas shows a wide range of CH4 signatures suggesting multiple sources of methane and carbon dioxide. These data are interpreted to distinguish regions with methane contributions from deep-sourced horizontal drilling versus shallow system microbial production. Development of a thorough environmental assessment using light isotope analysis can provide understanding of shallow anthropogenic versus natural CH4sources and assist in identifying regions that require remedial actions.

  9. Dielectric Barrier Discharge Methane Conversion

    NASA Astrophysics Data System (ADS)

    Liu, Chong; Fridman, Alexander; Rabinovich, Alexander; Dobrynin, Danil

    2015-09-01

    With the large amount of nature gas discovery every year, there is an increasing interest on modification of methane. The fact that methane is gaseous makes it less economic and efficient than liquid fuel. Here we propose a new way of converting methane from gas phase to liquid phase. Dielectric barrier discharge is used to treat methane and nitrogen mixture bubbles inside of liquid fuel. Nitrogen is here to help activate methane into an excited state, then it is possible for the excited molecules to react with other liquid hydrocarbon. Gaseous methane is converted in to liquid phase when excited methane replace a hydrogen and add onto the carbon chain. In this study some preliminary experiments is done to verify this hypothesis. There is equivalent weight increases with methane and nitrogen mixture discharging in diesel when compare to only nitrogen discharging in diesel. The same experiment have also been done with gas mixture discharged in 1-methylnaphthalene. And FTIR analysis of the after treatment hydrocarbon liquid all indicates that there is an increasing in C-H bond concentration and a decreasing in phenyl ring structure.

  10. A Methane Balloon Inflation Chamber

    ERIC Educational Resources Information Center

    Czerwinski, Curtis J.; Cordes, Tanya J.; Franek, Joe

    2005-01-01

    The various equipments, procedure and hazards in constructing the device for inflating a methane balloon using a standard methane outlet in a laboratory are described. This device is fast, safe, inexpensive, and easy to use as compared to a hydrogen gas cylinder for inflating balloons.

  11. Deep Vein Thrombosis

    MedlinePlus

    Deep vein thrombosis, or DVT, is a blood clot that forms in a vein deep in the body. Most deep vein ... the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem ...

  12. Constraining Methane Flux Estimates Using Atmospheric Observations of Methane and 1^3C in Methane

    NASA Astrophysics Data System (ADS)

    Mikaloff Fletcher, S. E.; Tans, P. P.; Miller, J. B.; Bruhwiler, L. M.

    2002-12-01

    Understanding the budget of methane is crucial to predicting climate change and managing earth's carbon reservoirs. Methane is responsible for approximately 15% of the anthropogenic greenhouse forcing and has a large impact on the oxidative capacity of Earth's atmosphere due to its reaction with hydroxyl radical. At present, many of the sources and sinks of methane are poorly understood due in part to the large spatial and temporal variability of the methane flux. Model simulations of methane mixing ratios using most process-based source estimates typically over-predict the latitudinal gradient of atmospheric methane relative to the observations; however, the specific source processes responsible for this discrepancy have not been identified definitively. The aim of this work is to use the isotopic signatures of the sources to attribute these discrepancies to a source process or group of source processes and create global and regional budget estimates that are in agreement with both the atmospheric observations of methane and 1^3C in methane. To this end, observations of isotopic ratios of 1^3C in methane and isotopic signatures of methane source processes are used in conjunction with an inverse model of the methane budget. Inverse modeling is a top-down approach which uses observations of trace gases in the atmosphere, an estimate of the spatial pattern of trace gas fluxes, and a model of atmospheric transport to estimate the sources and sinks. The atmospheric transport was represented by the TM3 three-dimensional transport model. The GLOBALVIEW 2001 methane observations were used along with flask measurements of 1^3C in methane at six of the CMDL-NOAA stations by INSTAAR. Initial results imply interesting differences from previous methane budget estimates. For example, the 1^3C isotope observations in methane call for an increase in southern hemisphere sources with a bacterial isotopic signature such as wetlands, rice paddies, termites, and ruminant animals. The

  13. Coal mine methane global review

    SciTech Connect

    2008-07-01

    This is the second edition of the Coal Mine Methane Global Overview, updated in the summer of 2008. This document contains individual, comprehensive profiles that characterize the coal and coal mine methane sectors of 33 countries - 22 methane to market partners and an additional 11 coal-producing nations. The executive summary provides summary tables that include statistics on coal reserves, coal production, methane emissions, and CMM projects activity. An International Coal Mine Methane Projects Database accompanies this overview. It contains more detailed and comprehensive information on over two hundred CMM recovery and utilization projects around the world. Project information in the database is updated regularly. This document will be updated annually. Suggestions for updates and revisions can be submitted to the Administrative Support Group and will be incorporate into the document as appropriate.

  14. Coalbed methane: Clean energy for the world

    USGS Publications Warehouse

    Ahmed, A.-J.; Johnston, S.; Boyer, C.; Lambert, S.W.; Bustos, O.A.; Pashin, J.C.; Wray, A.

    2009-01-01

    Coalbed methane (CBM) has the potential to emerge as a significant clean energy resource. It also has the potential to replace other diminishing hydrocarbon reserves. The latest developments in technologies and methodologies are playing a key role in harnessing this unconventional resource. Some of these developments include adaptations of existing technologies used in conventional oil and gas generations, while others include new applications designed specifically to address coal's unique properties. Completion techniques have been developed that cause less damage to the production mechanisms of coal seams, such as those occurring during cementing operations. Stimulation fluids have also been engineered specifically to enhance CBM production. Deep coal deposits that remain inaccessible by conventional mining operations offer CBM development opportunities.

  15. Natural gas hydrate occurrence and issues: Large amounts of methane in gas hydrates are potential energy sources; role in climate change?

    SciTech Connect

    Kvenvolden, K.

    1995-09-01

    Naturally occurring gas hydrate is a solid, icelike substance composed of rigid cages of water molecules that enclose molecules of gas, mainly methane. Chemically, this substance is a water clathrate of methane, often called methane clathrate, in addition to methane hydrate or gas hydrate. In an ideally saturated methane hydrate, the molar ratio of methane to water is 1:5.75, that is, equal to a volumetric ratio at standard conditions of about 164:1. Gas hydrate deposits aaoccur under specific conditions of pressure and temperature, where the supply of methane is sufficient to initiate and stabilize the hydrate structure. These conditions are met on Earth in shallow sediment, less than 2,000 meters deep in two regions: (1) continental, including continental shelves at high latitudes where surface temperatures are very cold, and (2) submarine continental slopes and rises where not only is the bottom water cold but also pressures are very high. Thus in polar regions, gas hydrate is found where temperatures are cold enough for onshore and offshore permafrost to be present. During global warming, deep sea gas hydrates become more stable, but gas hydrate of polar continents and continental shelves is destabilized, leading to methane release over long time scales. Methane reaching the atmosphere from these sources contributes to the global warming trend. During a global cooling cycle, the whole system reverses. Methodologies are being developed to recover methane from this substance. Three principal methods are being considered: thermal stimulation, depressurization, and inhibitor injection.

  16. Oxygen-Methane Thruster

    NASA Technical Reports Server (NTRS)

    Pickens, Tim

    2012-01-01

    An oxygen-methane thruster was conceived with integrated igniter/injector capable of nominal operation on either gaseous or liquid propellants. The thruster was designed to develop 100 lbf (approximately 445 N) thrust at vacuum conditions and use oxygen and methane as propellants. This continued development included refining the design of the thruster to minimize part count and manufacturing difficulties/cost, refining the modeling tools and capabilities that support system design and analysis, demonstrating the performance of the igniter and full thruster assembly with both gaseous and liquid propellants, and acquiring data from this testing in order to verify the design and operational parameters of the thruster. Thruster testing was conducted with gaseous propellants used for the igniter and thruster. The thruster was demonstrated to work with all types of propellant conditions, and provided the desired performance. Both the thruster and igniter were tested, as well as gaseous propellants, and found to provide the desired performance using the various propellant conditions. The engine also served as an injector testbed for MSFC-designed refractory combustion chambers made of rhenium.

  17. Making methane visible

    NASA Astrophysics Data System (ADS)

    Gålfalk, Magnus; Olofsson, Göran; Crill, Patrick; Bastviken, David

    2016-04-01

    Methane (CH4) is one of the most important greenhouse gases, and an important energy carrier in biogas and natural gas. Its large scale emission patterns have been unpredictable and the source and sink distributions are poorly constrained. Remote assessment of CH4 with high sensitivity at m2 spatial resolution would allow detailed mapping of near ground distribution and anthropogenic sources and sinks in landscapes but has hitherto not been possible. Here we show that CH4 gradients can be imaged on methane imaging will include a lake, barn, sewage sludge deposit, waste incineration plant, and controlled gas releases. We will also present successful simultaneous imaging of another important greenhouse gas, nitrous oxide, with the same instrument.

  18. Search for interstellar methane

    NASA Technical Reports Server (NTRS)

    Knacke, R. F.; Kim, Y. H.; Noll, K. S.; Geballe, T. R.

    1990-01-01

    Researchers searched for interstellar methane in the spectra of infrared sources embedded in molecular clouds. New observations of several lines of the P and R branches of the nu 3 band of CH4 near 3.3 microns give column densities in the range N less than 1(-2) times 10 to the minus 16th power cm(-2). Resulting abundance ratios are (CH4)/(CO) less than 3.3 times 10 to the minus 2nd power toward GL961 in NGC 2244 and less than 2.4 times 10 to the minus 3rd power toward GL989 in the NGC 2264 molecular cloud. The limits, and those determined in earlier observations of BN in Orion and GL490, suggest that there is little methane in molecular clouds. The result agrees with predictions of chemical models. Exceptions could occur in clouds where oxygen may be depleted, for example by H2O freezing on grains. The present observations probably did not sample such regions.

  19. Comparison of Landfill Methane Oxidation Measured Using Stable Isotope Analysis and CO2/CH4 Fluxes Measured by the Eddy Covariance Method

    NASA Astrophysics Data System (ADS)

    Xu, L.; Chanton, J.; McDermitt, D. K.; Li, J.; Green, R. B.

    2015-12-01

    Methane plays a critical role in the radiation balance and chemistry of the atmosphere. Globally, landfill methane emission contributes about 10-19% of the anthropogenic methane burden into the atmosphere. In the United States, 18% of annual anthropogenic methane emissions come from landfills, which represent the third largest source of anthropogenic methane emissions, behind enteric fermentation and natural gas and oil production. One uncertainty in estimating landfill methane emissions is the fraction of methane oxidized when methane produced under anaerobic conditions passes through the cover soil. We developed a simple stoichiometric model to estimate methane oxidation fraction when the anaerobic CO2 / CH4 production ratio is known, or can be estimated. The model predicts a linear relationship between CO2 emission rates and CH4 emission rates, where the slope depends on anaerobic CO2 / CH4 production ratio and the fraction of methane oxidized, and the intercept depends on non-methane-dependent oxidation processes. The model was tested using carbon dioxide emission rates (fluxes) and methane emission rates (fluxes) measured using the eddy covariance method over a one year period at the Turkey Run landfill in Georgia, USA. The CO2 / CH4 production ratio was estimated by measuring CO2 and CH4 concentrations in air sampled under anaerobic conditions deep inside the landfill. We also used a mass balance approach to independently estimate fractional oxidation based on stable isotope measurements (δ13C of methane) of gas samples taken from deep inside the landfill and just above the landfill surface. Results from the two independent methods agree well. The model will be described and methane oxidation will be discussed in relation to wind direction, location at the landfill, and age of the deposited refuse.

  20. Hydroxylation of methane through component interactions in soluble methane monooxygenases.

    PubMed

    Lee, Seung Jae

    2016-04-01

    Methane hydroxylation through methane monooxygenases (MMOs) is a key aspect due to their control of the carbon cycle in the ecology system and recent applications of methane gas in the field of bioenergy and bioremediation. Methanotropic bacteria perform a specific microbial conversion from methane, one of the most stable carbon compounds, to methanol through elaborate mechanisms. MMOs express particulate methane monooxygenase (pMMO) in most strains and soluble methane monooxygenase (sMMO) under copper-limited conditions. The mechanisms of MMO have been widely studied from sMMO belonging to the bacterial multicomponent monooxygenase (BMM) superfamily. This enzyme has diiron active sites where different types of hydrocarbons are oxidized through orchestrated hydroxylase, regulatory and reductase components for precise control of hydrocarbons, oxygen, protons, and electrons. Recent advances in biophysical studies, including structural and enzymatic achievements for sMMO, have explained component interactions, substrate pathways, and intermediates of sMMO. In this account, oxidation of methane in sMMO is discussed with recent progress that is critical for understanding the microbial applications of C-H activation in one-carbon substrates.

  1. Experimental determination of methane dissolution from simulated subsurface oil leakages

    NASA Astrophysics Data System (ADS)

    Sauthoff, W.; Peltzer, E. T.; Walz, P. M.; Brewer, P. G.

    2013-12-01

    Subsurface oil leakages and increased offshore drilling efforts have raised concern over the fate of hydrocarbon mixtures of oil and gas in ocean environments. Recent wellhead and pipeline failures in the Gulf of Mexico are extreme examples of this problem. Understanding the mechanism and rate of vertical transport of hydrocarbon chemical species is necessary to predict the environmental impact of subsurface leakages. In a series of controlled experiments, we carried out a deep-sea field experiment in Monterey Canyon to investigate the behavior of a gas-saturated liquid hydrocarbon mass rising from the seafloor. Aboard the R/V Rachel Carson, we used the ROV Ventana to transport a laboratory prepared volume of decane (C10H22) saturated with methane gas (CH4) to mimic a subsurface seafloor discharge. We released the oil and gas mixture into a vertically oriented open bottom glass tube followed by methane loss rate measurements both at discrete depths, and during rapid, continuous vehicle ascent from 800 to 100 m water depth to monitor changes in dissolution and bubble nucleation. Using laser Raman techniques and HD video we quantified the chemical state of the hydrocarbon fluid, including rate of methane gas dissolution. The primary methane Raman peak was readily observable within the decane C-H stretching complex. Variation in the amount of gas dissolved in the oil greatly influences oil plume density and in turn oil plume vertical rise rate. Our results show that the rise rate of the hydrocarbon mass significantly exceeds the rate at which the excess methane was lost by dissolution. This result implies that vertical transport of methane in the saturated hydrocarbon liquid phase can greatly exceed a gas bubble plume ascending the water column from a seafloor source. These results and observations may be applicable to improved understanding of the composition, distribution, and environmental fate of leaked hydrocarbon mixtures and inform remediation efforts.

  2. Weather, Climate, and Methane: Linking Short and Long Term Changes in Available Energy to Observed Methane Emission from Shallow Subarctic Lakes

    NASA Astrophysics Data System (ADS)

    Thornton, B. F.; Wik, M.; Crill, P. M.

    2015-12-01

    Many studies have noted that there is a positive relationship between temperatures in freshwater systems and methane production by Archaea, but not all freshwater systems are alike. In the Arctic and Subarctic, small, very shallow lakes are a common feature. We hypothesize that such lakes' sediment temperatures (where methane production occurs) are particularly sensitive and responsive to solar shortwave flux (SW), because direct solar heating of the sediments can partly bypass the need for physical mixing of warm water downwards across stratifications in the water column (such mixing is necessary for heating the bottom sediments in deeper lakes). Ebullitive (bubble) fluxes of methane are far more varying, and may represent the additional methane production not being diffusively lost. Although trigger events such as air pressure changes are known to transiently produce bubbling, we show a link to SW input on both shorter and longer timescales than previously demonstrated. However, it is difficult to separate SW-driven increases due to autochthonous production leading to increased methane production from SW-driven temperature increases in sediment speeding methane production in the current dataset. We show that in a shallow (ca. 1 m deep) lake (Villasjön, in Stordalen Mire, Sweden), during summer (June-August) methane bubbling is closely tied to available SW input on timescales of a few days. For the study area in northern Sweden, the available SW appears linked to the phase of the North Atlantic Oscillation (NAO). Relationships between the winter NAO and snow cover, which impacts lake ice-out date, and available summer SW are also considered. Linking methane production in shallow lakes to the NAO may allow back-projections of methane production in the Stordalen region to the 1860s. We compare these back-projections to recently published back-projections based on lake ice-out dates for Stordalen dating back to 1916.

  3. Archaebacterial Fuel Production: Methane from Biomass.

    ERIC Educational Resources Information Center

    Lennox, John E.; And Others

    1983-01-01

    Discusses microbial production of methane from biomass. Topics include methogens (bacteria producing methane), ecology of methanogenesis, methanogenesis in ruminant/nonruminant and other environments, role of methanogenesis in nature, and methane production in sewage treatment plants. Also discusses construction of methane digesters (and related…

  4. 75 FR 9886 - Methane Hydrate Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-04

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. Federal... Methane Hydrate Advisory Committee is to provide advice on potential applications of methane hydrate...

  5. Oceanic Methane Concentrations in Three Mexican Regions

    EPA Science Inventory

    The atmospheric concentration of methane has increased significantly over the last several decades. Methane is an important greenhouse gas, and it is important to better quantify methane sources and sinks. Dissolved methane in the ocean is produced by biological and hydrothermal ...

  6. Methane-derived hydrocarbons produced under upper-mantle conditions

    SciTech Connect

    Kolesnikov, Anton; Kutcherov, Vladimir G.; Goncharov, Alexander F.

    2009-08-13

    There is widespread evidence that petroleum originates from biological processes. Whether hydrocarbons can also be produced from abiogenic precursor molecules under the high-pressure, high-temperature conditions characteristic of the upper mantle remains an open question. It has been proposed that hydrocarbons generated in the upper mantle could be transported through deep faults to shallower regions in the Earth's crust, and contribute to petroleum reserves. Here we use in situ Raman spectroscopy in laser-heated diamond anvil cells to monitor the chemical reactivity of methane and ethane under upper-mantle conditions. We show that when methane is exposed to pressures higher than 2 GPa, and to temperatures in the range of 1,000-1,500 K, it partially reacts to form saturated hydrocarbons containing 2-4 carbons (ethane, propane and butane) and molecular hydrogen and graphite. Conversely, exposure of ethane to similar conditions results in the production of methane, suggesting that the synthesis of saturated hydrocarbons is reversible. Our results support the suggestion that hydrocarbons heavier than methane can be produced by abiogenic processes in the upper mantle.

  7. Shallow Methane Hydrates: Rates, Mechanisms of Formation and Environmental Significance.

    NASA Astrophysics Data System (ADS)

    Torres, M. E.; Trehu, A. M.

    2005-05-01

    Shallow gas hydrates have been identified at more than 20 locations worldwide, and are commonly associated with observations of bubble discharge at the seafloor. These deposits are host to active chemosynthetic communities and are likely to play a predominant role in energy, climate and carbon cycle issues associated with hydrate processes. Because seafloor gas hydrates are not in equilibrium with seawater, these deposits require a constant supply of methane to replace loss by continuous diffusion to bottom water. We will summarize evidence documenting that at the shallow deposits on Hydrate Ridge (OR) methane must be delivered in the free gas phase and present simple models used to infer formation rates, which are orders of magnitude higher than those for hydrates formed deeper in the sediment column (Torres et al., 2004). At Hydrate Ridge, methane gas is channeled from deep accretionary margin sequences to the gas hydrate stability zone (GHSZ) through a permeable layer that has been mapped seismically (Horizon A). High gas pressure in this horizon can drive gas through the GHSZ to the seafloor (Trehu et al., 2004). We will review current ideas that address mechanisms whereby gas migrates from Horizon A to the seafloor, including inhibition by capillary effects and the development of a high salinity front that can shift the hydrate stability field enough to allow for methane transport as a gas phase.

  8. Tetraperchlorate of methane

    NASA Technical Reports Server (NTRS)

    Schack, C. J.

    1972-01-01

    The preparation of the tetraperchlorate of methane (TPM) was attempted. Displacement of halogen from carbon tetrahalides was accomplished with either CCl4 or CBr4 using the halogen perchlorates, ClOClO3, and BOClO3. Although the displacement process was successful, the generated carbon perchlorate intermediates were not isolated. Instead, these species decomposed to COCl2, CO2, and Cl2O7. The vigorous displacement reaction that often occurred required moderation. Fluorocarbon solvents and chlorine perchlorate were successfully tested for compatibility, permitting their use in these synthetic reactions. While the sought for moderating effect was obtained, the net result of the displacement of halogen from CX sub 4 substrates was the same as before. Thus only CO2, COCl2, and Cl2O7 were isolated.

  9. (Methane digester). Final report

    SciTech Connect

    Waybright, R.C.

    1981-01-01

    The purpose of the grant was to construct and operate a methane digester for dairy manure involving the latest state-of-the-art technics. The first step taken was to empty out the existing digester to evaluate its performance and to gain ideas of how to build the next digester so it would operate more efficiently. Next, the design criteria was set up in order to eliminate some problems involved with the first digester and also new ideas as to how to build the next one without a protective building and testing simplified construction technics. After this the digester construction was started with the completion date in late January. The digester was then filled and operated at different temperatures attempting to achieve the optimum operating range.

  10. Large methane reserves beneath Antarctica?

    NASA Astrophysics Data System (ADS)

    Wadham, J. L.; Tulaczyk, S. M.; Stibal, M.; Arndt, S.; Telling, J.; Lis, G.; Lawson, E. C.; Dubnick, A.; Tranter, M.; Sharp, M. J.; Anesio, A.

    2010-12-01

    Once thought to be devoid of life, the Antarctic Ice Sheet is now known to be a dynamic reservoir of metabolically active microbial cells and organic carbon. Its potential to support the degradation of organic carbon to methane, however, has not yet been evaluated. Large marine sedimentary basins beneath the ice sheet (estimated to cover up to 50% by area and contain sedimentary sequences up to 3 km thick) remain thawed during glaciation. These basins are estimated to contain ~7000 Pg of organic carbon, assuming that sedimentary basins account for 1 and 2 M km2 of the West and East Antarctic Ice Sheets respectively, the organic carbon content of overridden marine sediments is 0.5 % and the mean sediment depth is 1 km. We predict that this carbon is microbially cycled to methane under anoxic conditions beneath the ice sheet. Laboratory experimental data are consistent with this and show that organic carbon overridden by glaciers and ice sheets produces methane under anoxic conditions, and at rates similar to those observed in sub-seafloor sediments. We numerically model the accumulation of methane in Antarctic sedimentary basins and show that sediment porewaters become over-saturated with methane over >1 Myr and that typical pressure/temperature conditions favour methane hydrate formation down to between ~500m and ~1000m in the sedimentary column. We calculate conservatively that a minimum of ~70 and ~360 PgC of releasable methane (clathrate + free gas) could be produced beneath the West and East Antarctic Ice Sheets over 3 and 30 Myr of glaciation respectively, which is of a similar order of magnitude to methane present as hydrate in Arctic permafrost. The stability of this releasable methane reserve depends sensitively upon in situ pressure conditions, and hence ice thickness. We show that only modest ice sheet retreat rates (700-2000 km2 a-1) are required to stimulate out gassing of releasable methane from Antarctic sedimentary basins at rates sufficient to

  11. Phase behavior of methane haze.

    PubMed

    Signorell, R; Jetzki, M

    2007-01-01

    Methane aerosols play a fundamental role in the atmospheres of Neptune, Uranus, and Saturn's moon Titan as borne out by the recent Cassini-Huygens mission. Here we present the first study of the phase behavior of free methane aerosol particles combining collisional cooling with rapid-scan infrared spectroscopy in situ. We find fast (within minutes) phase transitions to crystalline states directly after particle formation and characteristic surface effects for nanometer-sized particles. From our results, we conclude that in atmospheric clouds solid methane particles are crystalline.

  12. Phase behavior of methane haze.

    PubMed

    Signorell, R; Jetzki, M

    2007-01-01

    Methane aerosols play a fundamental role in the atmospheres of Neptune, Uranus, and Saturn's moon Titan as borne out by the recent Cassini-Huygens mission. Here we present the first study of the phase behavior of free methane aerosol particles combining collisional cooling with rapid-scan infrared spectroscopy in situ. We find fast (within minutes) phase transitions to crystalline states directly after particle formation and characteristic surface effects for nanometer-sized particles. From our results, we conclude that in atmospheric clouds solid methane particles are crystalline. PMID:17358473

  13. Deep blast

    NASA Astrophysics Data System (ADS)

    From southern New Mexico to the Great Slave Lake of Canada, scientists from the United States and Canada recently detonated 10 underground chemical explosions to generate a clearer picture of the Earth's crust and upper mantle. Called Project Deep Probe, the experiment is designed to see through the crust and into the upper mantle to a depth of 300 miles.In the United States, Earth scientists from Rice University, Purdue University, and the University of Oregon are participating in the project. “Researchers hope to get a picture of the upper mantle beneath the Rocky Mountains and the Colorado Plateau, to understand the role the mantle played in formation and uplift,” says Alan Levander of Rice. To enhance that “picture,” 750 portable seismographs were placed along a roughly north-south line extending from Crownpoint, New Mexico to Edmonton, Alberta. The seismic recordings will be used to enhance weak seismic waves that penetrated the upper mantle.

  14. Analysis of time-structure of BSRs using 3D seismic data in the Eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Nagakubo, S.; Inamori, T.; Kobayashi, T.; Fujii, T.

    2005-12-01

    According to the result of METI Exploratory Wells "Tokai-Oki to Kumano-nada" conducted in FY2003 in Japan, it is suggested that methane hydrate bearing layers in the Eastern Nanakai Trough distribute heterogeneously above BSRs (Bottom Simulating Reflectors). To understand the heterogeneity of distribution of methane hydrate bearing layers and explore concentrated hydrate bearing layers, we conducted a detailed analysis of time-structure map of BSR using 3D seismic survey data acquired in the Eastern Nankai Trough. Since P-wave velocity of hydrate bearing layers are high, it was expected that two-way-time from sea bottom to BSR is short above concentrated hydrate bearing layers compared to hydrate bearing zones. Although significant anomalies are recognized on time-structure map, it seems that anomalies are corresponding to heterogeneous thermal-structure in preference to distribution of hydrate bearing layers around surveyed area. It should be considered that these thermal anomalies are depending on fluid migration with hydrocarbons through faults, unconformities and permeable sand layers from deeper formations. Since occurrences of methane hydrates are strongly restricted by temperature and pressure, analysis of time-structure of BSR acquired by seismic data could be helpful to understand the accumulation mechanism of methane hydrates in sediments.

  15. Global Methane Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Reeburgh, W. S.

    2003-12-01

    Methane (CH4) has been studied as an atmospheric constituent for over 200 years. A 1776 letter from Alessandro Volta to Father Campi described the first experiments on flammable "air" released by shallow sediments in Lake Maggiore (Wolfe, 1996; King, 1992). The first quantitative measurements of CH4, both involving combustion and gravimetric determination of trapped oxidation products, were reported in French by Boussingault and Boussingault, 1864 and Gautier (1901), who reported CH4 concentrations of 10 ppmv and 0.28 ppmv (seashore) and 95 ppmv (Paris), respectively. The first modern measurements of atmospheric CH4 were the infrared absorption measurements of Migeotte (1948), who estimated an atmospheric concentration of 2.0 ppmv. Development of gas chromatography and the flame ionization detector in the 1950s led to observations of vertical CH4 distributions in the troposphere and stratosphere, and to establishment of time-series sampling programs in the late 1970s. Results from these sampling programs led to suggestions that the concentration of CH4, as that of CO2, was increasing in the atmosphere. The possible role of CH4 as a greenhouse gas stimulated further research on CH4 sources and sinks. Methane has also been of interest to microbiologists, but findings from microbiology have entered the larger context of the global CH4 budget only recently.Methane is the most abundant hydrocarbon in the atmosphere. It plays important roles in atmospheric chemistry and the radiative balance of the Earth. Stratospheric oxidation of CH4 provides a means of introducing water vapor above the tropopause. Methane reacts with atomic chlorine in the stratosphere, forming HCl, a reservoir species for chlorine. Some 90% of the CH4 entering the atmosphere is oxidized through reactions initiated by the OH radical. These reactions are discussed in more detail by Wofsy (1976) and Cicerone and Oremland (1988), and are important in controlling the oxidation state of the atmosphere

  16. Novel microbial communities of the Haakon Mosby mud volcano and their role as a methane sink.

    PubMed

    Niemann, Helge; Lösekann, Tina; de Beer, Dirk; Elvert, Marcus; Nadalig, Thierry; Knittel, Katrin; Amann, Rudolf; Sauter, Eberhard J; Schlüter, Michael; Klages, Michael; Foucher, Jean Paul; Boetius, Antje

    2006-10-19

    Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere. Recent investigations show that the number of active submarine mud volcanoes might be much higher than anticipated (for example, see refs 3-5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean. Unfortunately, global methane emission from active submarine mud volcanoes cannot be quantified because their number and gas release are unknown. It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72 degrees N, 14 degrees 44' E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active marine mud volcanoes to <40% of the total flux. PMID:17051217

  17. From wetlands to sauropods (?) and cold seeps: New perspectives on methane cycling in the Phanerozoic (Invited)

    NASA Astrophysics Data System (ADS)

    Tripati, A.; Beerling, D.; Bristow, T.; Campbell, K.; Catling, D. C.; Reinhard, C.; Rohrssen, M.; Sample, J. C.

    2013-12-01

    The role of methane in Phanerozoic climate change is a topic of debate. Methane has been implicated as a contributory climate forcing agent to sustained warm climates during the Permo-Carboniferous, the Mesozoic, and the Paleogene. It also has been discussed as a driver of transient warming events including rapid deglaciation marking the end of a hypothesized ';snowball' type glacial era in the run up to the Phanerozoic, the end-Ordovician glaciation, the Permo-Triassic boundary, and the Paleocene-Eocene Thermal Maximum. Here we review evidence for methane's role in Phanerozoic global climate change and present new carbon budget calculations for the Ordovician and Permo-Triassic. In addition, we will highlight some new perspectives on methane cycling, ranging from the possible significance of seawater sulfate concentrations in modulating oceanic anaerobic methane oxidation, methane emissions from the guts of sauropods and ruminants, to the decomposition of methane hydrates at active continental margins triggered by deep fluid flow in accretionary prism sediments during great earthquakes.

  18. [Microbial Processes and Genesis of Methane Gas Jets in the Coastal Areas of the Crimea Peninsula].

    PubMed

    Malakhova, T V; Kanapatskii, T A; Egorov, V N; Malakhova, L V; Artemov, Yu G; Evtushenko, D B; Gulin, S B; Pimenov, N V

    2015-01-01

    Hydroasoustic techniques were used for detection and mapping of gas jet areas in the coastal regions of the Crimean peninsula. Gas seep areas in the bays Laspi, Khersones, and Kazach'ya were chosen for detailed microbiological investigation. The first type of gas jets, observed in the Laspi Bay, was probably associated with discarge of deep thermogenic methane along the faults. Methane isotopic composition was char- acterized by Δ13C of -35.3 degrees. While elevated rates of aerobic methane oxidation were revealed in the sandy sediments adjacent to the methane release site, no evidence of bacterial mats was found. The second type of gas emission, observed in the Khersones Bay, was accompanied by formation of bacterial biofilms of the "Thiodendron" microbial community type, predominated by filamentous, spirochete-like organisms, in the areas of gas seepage. The isotopic composition of methane was there considerably lower (-60.4 degrees), indicating a considerable contribution of modern microbial methane to the gas bubbles discharged in this bay. Activity of the third type of gas emission, the seeps of the Kazach'ya Bay, probably depended directly on modern microbial processes of organic matter degradation in the upper sediment layers. The rates of sulfate reduction and methanogenesis were 260 and 34 μmol dm(-3) day(-1), respectively. Our results indicate different mechanisms responsible for formation of methane jets in the Laspi Bay and in the coastal areas of the Heracles Peninsula, where the bays Kazach'ya and Khersones are located.

  19. [Microbial Processes and Genesis of Methane Gas Jets in the Coastal Areas of the Crimea Peninsula].

    PubMed

    Malakhova, T V; Kanapatskii, T A; Egorov, V N; Malakhova, L V; Artemov, Yu G; Evtushenko, D B; Gulin, S B; Pimenov, N V

    2015-01-01

    Hydroasoustic techniques were used for detection and mapping of gas jet areas in the coastal regions of the Crimean peninsula. Gas seep areas in the bays Laspi, Khersones, and Kazach'ya were chosen for detailed microbiological investigation. The first type of gas jets, observed in the Laspi Bay, was probably associated with discarge of deep thermogenic methane along the faults. Methane isotopic composition was char- acterized by Δ13C of -35.3 degrees. While elevated rates of aerobic methane oxidation were revealed in the sandy sediments adjacent to the methane release site, no evidence of bacterial mats was found. The second type of gas emission, observed in the Khersones Bay, was accompanied by formation of bacterial biofilms of the "Thiodendron" microbial community type, predominated by filamentous, spirochete-like organisms, in the areas of gas seepage. The isotopic composition of methane was there considerably lower (-60.4 degrees), indicating a considerable contribution of modern microbial methane to the gas bubbles discharged in this bay. Activity of the third type of gas emission, the seeps of the Kazach'ya Bay, probably depended directly on modern microbial processes of organic matter degradation in the upper sediment layers. The rates of sulfate reduction and methanogenesis were 260 and 34 μmol dm(-3) day(-1), respectively. Our results indicate different mechanisms responsible for formation of methane jets in the Laspi Bay and in the coastal areas of the Heracles Peninsula, where the bays Kazach'ya and Khersones are located. PMID:26964364

  20. Summer methane fluxes from a boreal bog in northern Quebec, Canada, using eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Nadeau, Daniel F.; Rousseau, Alain N.; Coursolle, Carole; Margolis, Hank A.; Parlange, Marc B.

    2013-12-01

    A boreal bog located in the James Bay lowlands, Canada, was instrumented with an open-path gas analyzer to monitor the turbulent fluxes of methane throughout the summer of 2012. The mostly continuous eddy covariance measurements permitted the study of methane dynamics at the hourly, daily and seasonal scales. To exclude data segments for which the biological methane fluxes were underestimated due to inefficient atmospheric transport under stable stratification, we applied a novel approach based on both the atmospheric stability parameter ζ = z/L and the friction velocity u∗, where z is the measurement height and L the Obukhov length. The field measurements revealed the existence of at least one sustained ebullition event, triggered by low barometric pressures, a declining water table and increasing mechanical turbulence - suggesting that large-scale release of methane bubbles can be an important transport mechanism of methane in boreal bogs. The validity of similarity scaling for atmospheric methane under convective conditions was also assessed and the normalized standard deviations of methane concentrations did not scale well with ζ, highlighting the heterogeneity in natural methane production and release across the bog. Overall the hourly emissions ranged between -2.0 and 32.1 mg CH4 m-2 h-1, with a summertime mean of 2.4 mg CH4 m-2 h-1. At the daily scale, the two main controls on methane emissions were found to be the water table position and the peat temperature at 0.3 m under the surface. Contrary to other studies, seasonal methane emissions peaked when the water table was at its maximum distance from the surface, around mid-August. No clear diurnal pattern could be found in methane emissions, indicating that methane was produced quite deep within the peat. The seasonal emissions were estimated at 4.4 g CH4 m-2, and compared well with other observations over similar landscapes using different measurement techniques. Given that methane releases and

  1. Impact of hydrology on methane flux patterns in a permafrost-affected floodplain in Northeast Siberia

    NASA Astrophysics Data System (ADS)

    Kwon, Min Jung; Beulig, Felix; Kuesel, Kirsten; Wildner, Marcus; Heimann, Martin; Zimov, Nikita; Zimov, Sergei; Goeckede, Mathias

    2015-04-01

    produced in the first place due to less anaerobic condition, and subsequently most of it was oxidized while being transported to the atmosphere through diffusion. In fall, however, methane emission was higher in the drained site, potentially originating from stored methane during growing season or freshly produced methane in deep, relatively warmer soil layers. To summarize all effects of WTD, the drainage changed vegetation and microbial community structure, which in turn altered net methane emissions in growing season with significantly less amount of methane emission in drained site.

  2. Quasielastic electron scattering from methane, methane-d4, methane-d2, ethylene, and 2-methylpropane

    NASA Astrophysics Data System (ADS)

    Cooper, G.; Christensen, E.; Hitchcock, A. P.

    2007-08-01

    Quasielastic electron scattering from gaseous species at high momentum transfer was recently reported for the first time [Cooper et al., J. Electron Spectrosc. Relat. Phenom. 155, 28 (2007)]. The first results for CH4 and CD4 were well explained by a classical electron Compton scattering picture in which the electron scatters independently from each atom rather than the molecule as a whole. However, an alternative possible interpretation in terms of nondipole molecular vibrational excitation is suggested by previously published quantum mechanical calculations on high momentum transfer electron scattering from diatomic molecules [Bonham and de Souza, J. Chem. Phys. 79, 134 (1983)]. In order to determine which of these two interpretations best fits the experimental results, we have measured the quasielastic spectra of gaseous 2-methylpropane, ethylene, methane, and two isotopically substituted methanes, CH2D2 and CD4, at a momentum transfer of ˜20a.u. (2.25keV impact energy and 100° scattering angle). The experimental spectra are found to be composed of as many peaks as there are different atomic isotopes in the molecule (two for CH4, C2H4, 2-methylpropane, and CD4 and three for CH2D2). The peak positions are predicted accurately by the independent atom electron Compton scattering model, and the relative intensities are in reasonable agreement. The experimental results thus support classical electron Compton scattering as the origin of the signal.

  3. FORT UNION DEEP

    SciTech Connect

    Lyle A. Johnson Jr.

    2002-09-01

    Coalbed methane (CBM) is currently the hottest area of energy development in the Rocky Mountain area. The Powder River Basin (PRB) is the largest CBM area in Wyoming and has attracted the majority of the attention because of its high permeability and relatively shallow depth. Other Wyoming coal regions are also being targeted for development, but most of these areas have lower permeability and deeper coal seams. This project consists of the development of a CBM stimulation system for deep coal resources and involves three work areas: (1) Well Placement, (2) Well Stimulation, and (3) Production Monitoring and Evaluation. The focus of this project is the Washakie Basin. Timberline Energy, Inc., the cosponsor, has a project area in southern Carbon County, Wyoming, and northern Moffat County, Colorado. The target coal is found near the top of the lower Fort Union formation. The well for this project, Evans No.1, was drilled to a depth of 2,700 ft. Three coal seams were encountered with sandstone and some interbedded shale between seams. Well logs indicated that the coal seams and the sandstone contained gas. For the testing, the upper seam at 2,000 ft was selected. The well, drilled and completed for this project, produced very little water and only occasional burps of methane. To enhance the well, a mild severity fracture was conducted to fracture the coal seam and not the adjacent sandstone. Fracturing data indicated a fracture half-length of 34 ft, a coal permeability of 0.2226 md, and permeability of 15.3 md. Following fracturing, the gas production rate stabilized at 10 Mscf/day within water production of 18 bpd. The Western Research Institute (WRI) CBM model was used to design a 14-day stimulation cycle followed by a 30-day production period. A maximum injection pressure of 1,200 psig to remain well below the fracture pressure was selected. Model predictions were 20 Mscf/day of air injection for 14 days, a one-day shut-in, then flowback. The predicted flowback

  4. FORT UNION DEEP

    SciTech Connect

    Lyle A. Johnson Jr.

    2002-03-01

    Coalbed methane (CBM) is currently the hottest area of energy development in the Rocky Mountain area. The Powder River Basin (PRB) is the largest CBM area in Wyoming and has attracted the majority of the attention because of its high permeability and relatively shallow depth. Other Wyoming coal regions are also being targeted for development, but most of these areas have lower permeability and deeper coal seams. This project consists of the development of a CBM stimulation system for deep coal resources and involves three work areas: (1) Well Placement, (2) Well Stimulation, and (3) Production Monitoring and Evaluation. The focus of this project is the Washakie Basin. Timberline Energy, Inc., the cosponsor, has a project area in southern Carbon County, Wyoming, and northern Moffat County, Colorado. The target coal is found near the top of the lower Fort Union formation. The well for this project, Evans No.1, was drilled to a depth of 2,700 ft. Three coal seams were encountered with sandstone and some interbedded shale between seams. Well logs indicated that the coal seams and the sandstone contained gas. For the testing, the upper seam at 2,000 ft was selected. The well, drilled and completed for this project, produced very little water and only occasional burps of methane. To enhance the well, a mild severity fracture was conducted to fracture the coal seam and not the adjacent sandstone. Fracturing data indicated a fracture half-length of 34 ft, a coal permeability of 0.2226 md, and permeability of 15.3 md. Following fracturing, the gas production rate stabilized at 10 Mscf/day within water production of 18 bpd. The Western Research Institute (WRI) CBM model was used to design a 14-day stimulation cycle followed by a 30-day production period. A maximum injection pressure of 1,200 psig to remain well below the fracture pressure was selected. Model predictions were 20 Mscf/day of air injection for 14 days, a one-day shut-in, then flowback. The predicted flowback

  5. Stratified Community Responses to Methane and Sulfate Supplies in Mud Volcano Deposits: Insights from an In Vitro Experiment

    PubMed Central

    Zhang, Yu; Maignien, Lois; Stadnitskaia, Alina; Boeckx, Pascal; Xiao, Xiang; Boon, Nico

    2014-01-01

    Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans. AOM has also been reported in the deep biosphere. But the responses of the primary microbial players in eliciting changes in geochemical environments, specifically in methane and sulfate supplies, have yet to be fully elucidated. Marine mud volcanoes (MVs) expel a complex fluid mixture of which methane is the primary component, forming an environment in which AOM is a common phenomenon. In this context, we attempted to identify how the prokaryotic community would respond to changes in methane and sulfate intensities, which often occur in MV environments in the form of eruptions, diffusions or seepage. We applied an integrated approach, including (i) biochemical surveys of pore water originated from MV, (ii) in vitro incubation of mud breccia, and (iii) prokaryotic community structure analysis. Two distinct AOM regions were clearly detected. One is related to the sulfate methane transition zone (SMTZ) at depth of 30–55 cm below the sea floor (bsf); the second is at 165–205 cm bsf with ten times higher rates of AOM and SR. This finding contrasts with the sulfide concentrations in pore waters and supports the suggestion that potential AOM activity below the SMTZ might be an important methane sink that is largely ignored or underestimated in oceanic methane budget calculations. Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities. These incubation conditions also promote the increase of richness in bacterial communities. Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry. PMID:25393146

  6. Stratified community responses to methane and sulfate supplies in mud volcano deposits: insights from an in vitro experiment.

    PubMed

    Zhang, Yu; Maignien, Lois; Stadnitskaia, Alina; Boeckx, Pascal; Xiao, Xiang; Boon, Nico

    2014-01-01

    Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans. AOM has also been reported in the deep biosphere. But the responses of the primary microbial players in eliciting changes in geochemical environments, specifically in methane and sulfate supplies, have yet to be fully elucidated. Marine mud volcanoes (MVs) expel a complex fluid mixture of which methane is the primary component, forming an environment in which AOM is a common phenomenon. In this context, we attempted to identify how the prokaryotic community would respond to changes in methane and sulfate intensities, which often occur in MV environments in the form of eruptions, diffusions or seepage. We applied an integrated approach, including (i) biochemical surveys of pore water originated from MV, (ii) in vitro incubation of mud breccia, and (iii) prokaryotic community structure analysis. Two distinct AOM regions were clearly detected. One is related to the sulfate methane transition zone (SMTZ) at depth of 30-55 cm below the sea floor (bsf); the second is at 165-205 cm bsf with ten times higher rates of AOM and SR. This finding contrasts with the sulfide concentrations in pore waters and supports the suggestion that potential AOM activity below the SMTZ might be an important methane sink that is largely ignored or underestimated in oceanic methane budget calculations. Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities. These incubation conditions also promote the increase of richness in bacterial communities. Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry.

  7. Stratified community responses to methane and sulfate supplies in mud volcano deposits: insights from an in vitro experiment.

    PubMed

    Zhang, Yu; Maignien, Lois; Stadnitskaia, Alina; Boeckx, Pascal; Xiao, Xiang; Boon, Nico

    2014-01-01

    Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans. AOM has also been reported in the deep biosphere. But the responses of the primary microbial players in eliciting changes in geochemical environments, specifically in methane and sulfate supplies, have yet to be fully elucidated. Marine mud volcanoes (MVs) expel a complex fluid mixture of which methane is the primary component, forming an environment in which AOM is a common phenomenon. In this context, we attempted to identify how the prokaryotic community would respond to changes in methane and sulfate intensities, which often occur in MV environments in the form of eruptions, diffusions or seepage. We applied an integrated approach, including (i) biochemical surveys of pore water originated from MV, (ii) in vitro incubation of mud breccia, and (iii) prokaryotic community structure analysis. Two distinct AOM regions were clearly detected. One is related to the sulfate methane transition zone (SMTZ) at depth of 30-55 cm below the sea floor (bsf); the second is at 165-205 cm bsf with ten times higher rates of AOM and SR. This finding contrasts with the sulfide concentrations in pore waters and supports the suggestion that potential AOM activity below the SMTZ might be an important methane sink that is largely ignored or underestimated in oceanic methane budget calculations. Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities. These incubation conditions also promote the increase of richness in bacterial communities. Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry. PMID:25393146

  8. Methane production in terrestrial arthropods

    SciTech Connect

    Hackstein, J.H.P.; Stumm, C.K. )

    1994-06-07

    The authors have screened more than 110 representatives of the different taxa of terrestrial arthropods for methane production in order to obtain additional information about the origins of biogenic methane. Methanogenic bacteria occur in the hindguts of nearly all tropical representatives of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isoptera), and scarab beetles (Scarabaeidae), while such methanogens are absent from 66 other arthropod species investigated. Three types of symbiosis were found: in the first type, the arthropod's hindgut is colonized by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hindgut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are likely to be a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populations of methane-producing arthropods constitute an enormous biomass. The authors show that arthropod symbionts can contribute substantially to atmospheric methane.

  9. Methane production in terrestrial arthropods.

    PubMed

    Hackstein, J H; Stumm, C K

    1994-06-01

    We have screened more than 110 representatives of the different taxa of terrestrial arthropods for methane production in order to obtain additional information about the origins of biogenic methane. Methanogenic bacteria occur in the hindguts of nearly all tropical representatives of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isoptera), and scarab beetles (Scarabaeidae), while such methanogens are absent from 66 other arthropod species investigated. Three types of symbiosis were found: in the first type, the arthropod's hindgut is colonized by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hindgut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are likely to be a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populations of methane-producing arthropods constitute an enormous biomass. We show that arthropod symbionts can contribute substantially to atmospheric methane.

  10. Methane production in terrestrial arthropods.

    PubMed Central

    Hackstein, J H; Stumm, C K

    1994-01-01

    We have screened more than 110 representatives of the different taxa of terrestrial arthropods for methane production in order to obtain additional information about the origins of biogenic methane. Methanogenic bacteria occur in the hindguts of nearly all tropical representatives of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isoptera), and scarab beetles (Scarabaeidae), while such methanogens are absent from 66 other arthropod species investigated. Three types of symbiosis were found: in the first type, the arthropod's hindgut is colonized by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hindgut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are likely to be a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populations of methane-producing arthropods constitute an enormous biomass. We show that arthropod symbionts can contribute substantially to atmospheric methane. Images PMID:8202505

  11. Methane emissions from MBT landfills

    SciTech Connect

    Heyer, K.-U. Hupe, K.; Stegmann, R.

    2013-09-15

    Highlights: • Compilation of methane generation potential of mechanical biological treated (MBT) municipal solid waste. • Impacts and kinetics of landfill gas production of MBT landfills, approach with differentiated half-lives. • Methane oxidation in the waste itself and in soil covers. • Estimation of methane emissions from MBT landfills in Germany. - Abstract: Within the scope of an investigation for the German Federal Environment Agency (“Umweltbundesamt”), the basics for the estimation of the methane emissions from the landfilling of mechanically and biologically treated waste (MBT) were developed. For this purpose, topical research including monitoring results regarding the gas balance at MBT landfills was evaluated. For waste treated to the required German standards, a methane formation potential of approximately 18–24 m{sup 3} CH{sub 4}/t of total dry solids may be expected. Monitoring results from MBT landfills show that a three-phase model with differentiated half-lives describes the degradation kinetics in the best way. This is due to the fact that during the first years of disposal, the anaerobic degradation processes still proceed relatively intensively. In addition in the long term (decades), a residual gas production at a low level is still to be expected. Most of the soils used in recultivation layer systems at German landfills show a relatively high methane oxidation capacity up to 5 l CH{sub 4}/(m{sup 2} h). However, measurements at MBT disposal sites indicate that the majority of the landfill gas (in particular at non-covered areas), leaves the landfill body via preferred gas emission zones (hot spots) without significant methane oxidation. Therefore, rather low methane oxidation factors are recommended for open and temporarily covered MBT landfills. Higher methane oxidation rates can be achieved when the soil/recultivation layer is adequately designed and operated. Based on the elaborated default values, the First Order Decay (FOD

  12. Methane generation from animal wastes

    SciTech Connect

    Fulton, E.L.

    1980-06-01

    The conversion of manure to biogas via anaerobic digestion is described. The effluent resulting from the conversion retains fertilizer value and is environmentally acceptable. Discussion is presented under the headings: methane formation in the digester; the Tarleton State Poultry Waste to Methane production system; operating experience at Tarleton State; economics of biogas production from poultry waste; construction cost and biogas value; energy uses; feed and waste processing; and advantages of anaerobic digestion. (DMC)

  13. Methane production in Minnesota peatlands

    SciTech Connect

    Williams, R.T.; Crawford, R.L.

    1984-06-01

    Rates of methane production in Minnesota peats were studied. Surface (10- to 25-cm) peats produced an average of 228 nmol of CH/sub 4/ per g (dry weight) per h at 25/sup 0/C and ambient pH. Methanogenesis rates generally decreased with depth in ombrotrophic peats, but on occasion were observed to rise within deeper layers of certain fen peats. Methane production was temperature dependent, increasing with increasing temperature (4 to 30/sup 0/C), except in peats from deeper layers. Maximal methanogenesis from these deeper regions occurred at 12/sup 0/C. Methane production rates were also pH dependent. Two peats with pHs of 3.8 and 4.3 had an optimum rate of methane production at pH 6.0. The addition to peat of glucose and H/sub 2/-CO/sub 2/ stimulated methanogenesis, whereas the addition of acetate inhibited methanogenesis. Cysteine-sulfide, nitrogen-phosphorus-trace metals, and vitamins-yeast extract affected methane production very little. Various gases were found to be trapped or dissolved (or both) within peatland waters. Dissolved methane increased linearly to a depth of 210 cm. The accumulation of metabolic end products produced within peat bogs appears to be an important mechanism limiting turnover in peatland environments.

  14. Optical constants of solid methane

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Thompson, W. R.; Sagan, C.; Arakawa, E. T.; Bruel, C.; Judish, J. P.; Khanna, R. K.; Pollack, J. B.

    1989-01-01

    Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented of the optical constants of solid methane for the 0.4 to 2.6 micron region. K is reported for both the amorphous and the crystalline (annealed) states. Using the previously measured values of the real part of the refractive index, n, of liquid methane at 110 K n is computed for solid methane using the Lorentz-Lorentz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for condensed CH4.

  15. Assessing the Efficacy of the Aerobic Methanotrophic Biofilter in Methane Hydrate Environments

    SciTech Connect

    Valentine, David

    2012-09-30

    In October 2008 the University of California at Santa Barbara (UCSB) initiated investigations of water column methane oxidation in methane hydrate environments, through a project funded by the National Energy Technology Laboratory (NETL) entitled: assessing the efficacy of the aerobic methanotrophic biofilter in methane hydrate environments. This Final Report describes the scientific advances and discoveries made under this award as well as the importance of these discoveries in the broader context of the research area. Benthic microbial mats inhabit the sea floor in areas where reduced chemicals such as sulfide reach the more oxidizing water that overlies the sediment. We set out to investigate the role that methanotrophs play in such mats at locations where methane reaches the sea floor along with sulfide. Mats were sampled from several seep environments and multiple sets were grown in-situ at a hydrocarbon seep in the Santa Barbara Basin. Mats grown in-situ were returned to the laboratory and used to perform stable isotope probing experiments in which they were treated with 13C-enriched methane. The microbial community was analyzed, demonstrating that three or more microbial groups became enriched in methane?s carbon: methanotrophs that presumably utilize methane directly, methylotrophs that presumably consume methanol excreted by the methanotrophs, and sulfide oxidizers that presumably consume carbon dioxide released by the methanotrophs and methylotrophs. Methanotrophs reached high relative abundance in mats grown on methane, but other bacterial processes include sulfide oxidation appeared to dominate mats, indicating that methanotrophy is not a dominant process in sustaining these benthic mats, but rather a secondary function modulated by methane availability. Methane that escapes the sediment in the deep ocean typically dissolved into the overlying water where it is available to methanotrophic bacteria. We set out to better understand the efficacy of this

  16. Is methane a new therapeutic gas?

    PubMed Central

    2012-01-01

    Background Methane is an attractive fuel. Biologically, methanogens in the colon can use carbon dioxide and hydrogen to produce methane as a by-product. It was previously considered that methane is not utilized by humans. However, in a recent study, results demonstrated that methane could exert anti-inflammatory effects in a dog small intestinal ischemia-reperfusion model. Point of view Actually, the bioactivity of methane has been investigated in gastrointestinal diseases, but the exact mechanism underlying the anti-inflammatory effects is required to be further elucidated. Methane can cross the membrane and is easy to collect due to its abundance in natural gas. Although methane is flammable, saline rich in methane can be prepared for clinical use. These seem to be good news in application of methane as a therapeutic gas. Conclusion Several problems should be resolved before its wide application in clinical practice. PMID:23009320

  17. Phase states of methane in fossil coals

    NASA Astrophysics Data System (ADS)

    Alexeev, A. D.; Vasylenko, T. A.; Ul'yanova, E. V.

    2004-06-01

    NMR measurements have revealed that methane can exist in coal samples in the state of solid solution rather than only adsorbed gas, opening new ways to prevention of gas dynamic accidents in underground coal mines and true estimation of coalbed methane resources. Understanding molecular structure of coal constituents and forms of methane occurrence in coal is the only way of extracting safely either coal or methane. We had studied nuclear magnetic resonance lines in various coals at room or low temperatures and have found that there exist three species of methane molecules differing in molecular mobility. Based on estimated diffusion parameters, these species were attributed to free methane, adsorbed methane, and solid solution of methane in crystalline coal substance. While first two phases are well known and can be analyzed by many different techniques, the last one hardly can be studied by methods other than NMR, resulting in inadequate estimations of methane resources.

  18. Making methane visible

    NASA Astrophysics Data System (ADS)

    Gålfalk, Magnus; Olofsson, Göran; Crill, Patrick; Bastviken, David

    2016-04-01

    Methane (CH4) is one of the most important greenhouse gases, and an important energy carrier in biogas and natural gas. Its large-scale emission patterns have been unpredictable and the source and sink distributions are poorly constrained. Remote assessment of CH4 with high sensitivity at a m2 spatial resolution would allow detailed mapping of the near-ground distribution and anthropogenic sources in landscapes but has hitherto not been possible. Here we show that CH4 gradients can be imaged on the

  19. Origin of hydrothermal fluid methane in sediment-associated Okinawa Trough fields

    NASA Astrophysics Data System (ADS)

    Kawagucci, S.

    2012-12-01

    Deep-sea hydrothermal fields in the sediment-associated Okinawa Trough and their fluid chemistry have been investigated over two decades. In sediment-associated hydrothermal systems including all the Okinawa Trough fields, hydrothermal fluids are characterized by abundant methane. Historically, most of this methane has been thought to originate thermogenically. However, recent works, related to the TAIGA project, have revealed remarkable compositional and isotopic variation of the hydrothermal fluid methane among the sediment-associated hydrothermal fields [1-3], suggesting multiple origins of methane other than thermochemical hydrocarbon generation. For example, 13C-depleted methane in the Iheya-North field implies its biogenic origin [2] while 13C-enriched methane in the Minami-Ensei field is probably derived from thermochemical process. Interpreting the imprinted chemical information in venting fluid methane (13C/12C, D/H) with the related chemistry ([H2], [C2+], 87Sr/86Sr, etc.) is an excellent way not only to reveal geochemical origin of methane in high-temperature fluid but also to deduce the subseafloor processes occurring within the whole hydrothermal fluid circulation [1]. The geochemical origins of the hydrothermal fluid methane and their relevance to the magnitude and geographical distribution of the entire subseafloor fluid circulation in the sediment-associated hydrothermal system are discussed. [1] Kawagucci, S. et. al., Chemical Geology, doi: 10.1016/j.chemgeo.2012.05.003, 2012. [2] Kawagucci, S. et al., Geochemical Journal, 45, 109-124, 2011. [3] Kawagucci, S. et al., Geochemical Journal, 44, 507-518, 2010.

  20. Temporal patterns of methane emissions from wetland rice fields treated by different modes of N application

    NASA Astrophysics Data System (ADS)

    Wassmann, R.; Neue, H. U.; Lantin, R. S.; Aduna, J. B.; Alberto, M. C. R.; Andales, M. J.; Tan, M. J.; van der Gon, H. A. C. Denier; Hoffmann, H.; Papen, H.; Rennenberg, H.; Seiler, W.

    1994-08-01

    Methane emission rates from wetland rice fields were determined in Los Baños (Philippines) using an automatic system that allows continuous measurements over time. Methane emission was monitored in an irrigated Aquandic Epiaqualf planted to rice cultivar IR72. Urea fertilizer was applied using four modes: (1) broadcast 10 days after transplanting, (2) broadcast at transplanting, (3) broadcast and incorporated at final harrowing, and (4) deep placement as sulfur-coated granules. The treatments were laid out in a randomized complete block design with four replicates. Measurements were done in the 1991 wet season, 1992 dry season (four treatments), and the 1992 wet season (only treatment 3). Methane emission rates from the experimental plots showed pronounced seasonal and diel variations. The diel pattern of methane emission rates followed a consistent pattern, with highest rates observed in the early afternoon and lowest rates in the early morning. Methane emission rate was generally highest at the ripening stage. The average methane emission rate during the 1992 dry season (190 mg CH4 m-2 d-1) exceeded the average flux rates of the 1992 wet season (79 mg CH4 m-2 d-1) by a factor of 2.4. The total methane emitted from these flooded rice fields amounted to 19 g CH4 m-2 in the dry season with rice yields of 5.2-6.3 t ha-1 and 7 g CH4 m-2 in the wet season with rice yields of 2.4-3.3 t ha-1 regardless of the mode of N application. Significant amounts corresponding to 20% of the methane released under waterlogged conditions were released when the soil was drained after harvest. Emission rates increased sharply when the floodwater receded and macropores started to drain. Emission of methane stopped only when the soil became fully aerated.

  1. Unifying principles of the deep terrestrial and deep marine biospheres

    NASA Astrophysics Data System (ADS)

    Colwell, Frederick S.; Smith, Richard P.

    Recent estimates of the amount of microbial biomass in the combined marine and terrestrial subsurface boost this portion of the biosphere to a level which needs to be considered when integrating where life exists on our planet. Additionally, the subsurface serves practical needs associated with groundwater, waste disposal, and resource recovery. Although our view of this isolated ecosystem is restricted by technologies used to access samples, we are learning more about places where life thrives in the subsurface and where life is severely repressed. Until studies of hyperthermophiles provide different information, a thermal boundary to life exists at the 120°C isotherm. Other locations in the subsurface are barren where they are impoverished by low fluid flux to supply electron donors and acceptors or by limited pore space in which microorganisms can reside. Examples of such locations include deep vadose zones and igneous rock masses with limited fractures. In contrast, subsurface locations that show evidence of gaseous or liquid flux are the most likely to yield higher numbers of microorganisms. Locations that have marine and terrestrial hydrothermal convection cells, active methane venting, solid-liquid-gas phase changes, as well as zones of salinity and porosity contrasts are all examples of demonstrated or potential subsurface oases. Our ability to conceptualize and quantify the subsurface biosphere will be accelerated by new sampling tools and molecular characterization methods for microbes. The merging of disparate disciplines such as microbiology, geophysics, and tectonic research will extend our ability to fully comprehend the deep biosphere.

  2. Methane monooxygenase: functionalizing methane at iron and copper.

    PubMed

    Sazinsky, Matthew H; Lippard, Stephen J

    2015-01-01

    Methane monooxygenases (MMOs) catalyze the conversion of methane to methanol as the first committed step in the assimilation of this hydrocarbon into biomass and energy by methanotrophs, thus playing a significant role in the biogeochemistry of this potent greenhouse gas. Two distinct enzymes, a copper-dependent membrane protein, particulate methane monooxygenase (pMMO), and an iron-dependent cytosolic protein, soluble methane monooxygenase (sMMO), carry out this transformation using large protein scaffolds that help to facilitate the timely transport of hydrocarbon, O₂, proton, and electron substrates to buried dimetallic active sites. For both enzymes, reaction of the reduced metal centers with O₂leads to intermediates that activate the relatively inert C-H bonds of hydrocarbons to yield oxidized products. Among synthetic and biological catalysts, MMOs are unique because they are the only ones known to hydroxylate methane at ambient temperatures. As a need for new industrial catalysts and green chemical transformations increases, understanding how the different MMO metal centers efficiently accomplish this challenging chemistry has become the focus of intense study. This chapter examines current understanding of the sMMO and pMMO protein structures, their methods for substrate channeling, and mechanisms for the dimetallic activation of O₂and C-H bonds. PMID:25707469

  3. Methane production from steam-exploded bamboo.

    PubMed

    Kobayashi, Fumihisa; Take, Harumi; Asada, Chikako; Nakamura, Yoshitoshi

    2004-01-01

    To convert unutilized plant biomass into a useful energy source, methane production from bamboo was investigated using a steam explosion pretreatment. Methane could not be produced from raw bamboo but methane production was enhanced by steam explosion. The maximum amount of methane produced, i.e., about 215 ml, was obtained from 1 g of exploded bamboo at a steam pressure of 3.53 MPa and a steaming time of 5 min. A negative correlation between the amount of methane produced and the amount of Klason lignin was observed in the methane fermentation of steam-exploded bamboo.

  4. Influence of transient flooding on methane fluxes from subtropical pastures

    NASA Astrophysics Data System (ADS)

    Chamberlain, Samuel D.; Gomez-Casanovas, Nuria; Walter, M. Todd; Boughton, Elizabeth H.; Bernacchi, Carl J.; DeLucia, Evan H.; Groffman, Peter M.; Keel, Earl W.; Sparks, Jed P.

    2016-03-01

    Seasonally flooded subtropical pastures are major methane (CH4) sources, where transient flooding drives episodic and high-magnitude emissions from the underlying landscape. Understanding the mechanisms that drive these patterns is needed to better understand pasture CH4 emissions and their response to global change. We investigated belowground CH4 dynamics in relation to surface fluxes using laboratory water table manipulations and compared these results to field-based eddy covariance measurements to link within-soil CH4 dynamics to ecosystem fluxes. Ecosystem CH4 fluxes lag flooding events, and this dynamic was replicated in laboratory experiments. In both cases, peak emissions were observed during water table recession. Flooding of surface organic soils and precipitation driven oxygen pulses best explained the observed time lags. Precipitation oxygen pulses likely delay CH4 emissions until groundwater dissolved oxygen is consumed, and emissions were temporally linked to CH4 production in surface soil horizons. Methane accumulating in deep soils did not contribute to surface fluxes and is likely oxidized within the soil profile. Methane production rates in surface organic soils were also orders of magnitude higher than in deep mineral soils, suggesting that over longer flooding regimes CH4 produced in deep horizons is not a significant component of surface emissions. Our results demonstrate that distinct CH4 dynamics may be stratified by depth and flooding of surface organic soils drives CH4 fluxes from subtropical pastures. These results suggest that small changes in pasture water table dynamics can drive large changes in CH4 emissions if surface soils remain saturated over longer time scales.

  5. Methane Emission from Tropical Rivers

    NASA Astrophysics Data System (ADS)

    Sawakuchi, H. O.; Rasera, M. F. F. L.; Krusche, A. V.; Ballester, M. V. R.

    2012-04-01

    Inland water is already known as an important source of methane to atmosphere. Methane is produced in anaerobic environments usually find in lakes and floodplain bottom sediment. It is the main reason that almost all information regarding methane flux come from this environments. However, while floodplain dries during low water season reducing methanogenesis, rivers keep the capacity to emit methane throughout the year. Here we present preliminary results of CH4 flux measurements done in 6 large tropical rivers within the Amazon basin. We measured 17 areas using floating chamber during dry (low water) season, between September and November of 2011, in Amazon river mainstem, Araguaia, Xingu, Tapajós, Madeira, and Negro Rivers. Measured fluxes of all rivers ranged from 59.3 to 2974.4 mmol m-2 yr-1. Geomorphologic structure of channels is one important factor that contributes to this high heterogeneity due to development of low flow velocity depositional settings allowing formation of anoxic zones in rivers. Hydraulic and sediment barriers in the confluence of river channels promote the generation of natural dams which function as a trap for the suspension load favoring the deposition of organic rich muds. This kind of environment is very different from common river channels and has a stronger potential of methane emission. Average values of our flux measurements for this two river environments show that depositional areas can have much higher fluxes than the main channel, 1089.6 and 163.1 mmol m-2 yr-1, respectively. Hence, CH4 flux from these depositional zones is similar to some tropical floodplain lakes and reservoirs. Although the low flux from channel, the area covered by water is very large resulting in a significant contribution to the regional methane emission to the atmosphere. Moreover, mapping the area of these depositional river zones will give us a better idea of the magnitude of methane flux from tropical rivers.

  6. A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

    NASA Astrophysics Data System (ADS)

    Archer, D.

    2014-06-01

    A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbon (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales

  7. A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

    DOE PAGES

    Archer, D.

    2014-06-03

    A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbonmore » (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time

  8. Reconstructing Methane Emission Events in the Arctic Ocean: Observations from the Past to Present

    NASA Astrophysics Data System (ADS)

    Panieri, G.; Mienert, J.; Fornari, D. J.; Torres, M. E.; Lepland, A.

    2015-12-01

    Methane hydrates are ice-like crystals that are present along continental margins, occurring in the pore space of deep sediments or as massive blocks near the seafloor. They form in high pressure and low temperature environments constrained by thermodynamic stability, and supply of methane. In the Arctic, gas hydrates are abundant, and the methane released by their destabilization can affect local to global carbon budgets and cycles, ocean acidification, and benthic community survival. With the aim to locate in space and time the periodicity of methane venting, CAGE is engaged in a vast research program in the Arctic, a component of which comprises the analyses of numerous sediment cores and correlative geophysical and geochemical data from different areas. Here we present results from combined analyses of biogenic carbonate archives along the western Svalbard Margin, which reveal past methane venting events in this region. The reconstruction of paleo-methane discharge is complicated by precipitation of secondary carbonate on foraminifera shells, driven by an increase in alkalinity during anaerobic oxidation of methane (AOM). The biogeochemical processes involved in methane cycling and processes that drive methane migration affect the depth where AOM occurs, with relevance to secondary carbonate formation. Our results show the value and complexity of separating primary vs. secondary signals in bioarchives with relevance to understanding fluid-burial history in methane seep provinces. Results from our core analyses are integrated with observations made during the CAGE15-2 cruise in May 2015, when we deployed a towed vehicle equipped with camera, multicore and water sampling capabilities. The instrument design was based on the Woods Hole Oceanographic Institution (WHOI) MISO TowCam sled equipped with a deep-sea digital camera and CTD real-time system. Sediment sampling was visually-guided using this system. In one of the pockmarks along the Vestnesa Ridge where high

  9. Characterization of Methane Degradation and Methane-Degrading Microbes in Alaska Coastal Water

    SciTech Connect

    Kirchman, David L.

    2012-03-29

    The net flux of methane from methane hydrates and other sources to the atmosphere depends on methane degradation as well as methane production and release from geological sources. The goal of this project was to examine methane-degrading archaea and organic carbon oxidizing bacteria in methane-rich and methane-poor sediments of the Beaufort Sea, Alaska. The Beaufort Sea system was sampled as part of a multi-disciplinary expedition (Methane in the Arctic Shelf or MIDAS) in September 2009. Microbial communities were examined by quantitative PCR analyses of 16S rRNA genes and key methane degradation genes (pmoA and mcrA involved in aerobic and anaerobic methane degradation, respectively), tag pyrosequencing of 16S rRNA genes to determine the taxonomic make up of microbes in these sediments, and sequencing of all microbial genes (metagenomes ). The taxonomic and functional make-up of the microbial communities varied with methane concentrations, with some data suggesting higher abundances of potential methane-oxidizing archaea in methane-rich sediments. Sequence analysis of PCR amplicons revealed that most of the mcrA genes were from the ANME-2 group of methane oxidizers. According to metagenomic data, genes involved in methane degradation and other degradation pathways changed with sediment depth along with sulfate and methane concentrations. Most importantly, sulfate reduction genes decreased with depth while the anaerobic methane degradation gene (mcrA) increased along with methane concentrations. The number of potential methane degradation genes (mcrA) was low and inconsistent with other data indicating the large impact of methane on these sediments. The data can be reconciled if a small number of potential methane-oxidizing archaea mediates a large flux of carbon in these sediments. Our study is the first to report metagenomic data from sediments dominated by ANME-2 archaea and is one of the few to examine the entire microbial assemblage potentially involved in

  10. Air-Sea Methane Flux after the Deepwater Horizon Oil Leak

    NASA Astrophysics Data System (ADS)

    McAdoo, J.; Sweeney, C.; Kiene, R. P.; McGillis, W. R.

    2012-12-01

    One of the key questions associated with the Deepwater Horizon's (DWH) oil leak involves understanding how much of its methane is still entrained in deep waters. Analysis of air-sea fluxes reveals a slight decrease in average aqueous CH4 from 3.3 nM in June to 3.1 and 2.8 nM in August and September, respectively. The flux estimate showed higher methane flux to the atmosphere after the blowout was capped (3.8 μmol m-2 d-1 in August) compared to 0.024 μmol m-2 d-1 during the leak. Almost all observations were within the range of historical levels. The exception was one large peak to the southwest of the wellhead, but its contribution to atmospheric methane is found to be insignificant compared to the total amount of methane released by the leak. This result supports findings that DWH methane remained entrained in the deep waters and consequently is available for biological degradation and threatens to deplete oxygen, adding further stress to an area that already suffers from anoxic-induced dead zones.

  11. Methane anomalies in seawater above the Loihi submarine summit area, Hawaii

    SciTech Connect

    Gamo, Toshitaka; Ishibashi, Junichiro; Sakai, Hitoshi ); Tilbrook, B. )

    1987-10-01

    Hydrothermal activity above Loihi submarine volcano was characterized by water column distributions of methane, pH and helium-3. It was found that the southern Loihi summit is almost covered with hydrothermal plumes, which have anomalously high concentrations of methane (maximum: 569 {times} 10{sup {minus}6} cm{sup 3} kg{sup {minus}}1) accompanied by high concentrations of helium-3 and low pH values (minimum: 7.18). The plumes consist of two layers: a shallow plume (about 200 m above the summit) and a deep plume (about 100 m above the summit), probably derived from different hydrothermal vents. The shallow and deep plumes showed different CH{sub 4}/{sup 3}He and CH{sub 4}/pH ratios with the same {sup 3}He/pH ratio, which implies that methane concentrations differ between the hydrothermal end members for the two plumes. The variation of methane between the end members is suggested to result from inter-vent inhomogeneity of bacterial activities that consume or produce methane within the vents. Comparison of the CH{sub 4}/{sup 3}He ratios of the two plumes with the previous data for Loihi and other submarine hydrothermal areas confirms that the Loihi hotspot has one to two orders of magnitude smaller CH{sub 4}/{sup 3}He value than those of the East Pacific Rise and the Galapagos spreading centers.

  12. Consumption of atmospheric methane by desert soils

    USGS Publications Warehouse

    Striegl, R.G.; McConnaughey, T.A.; Thorstenson, D.C.; Weeks, E.P.; Woodward, J.C.

    1992-01-01

    ATMOSPHERIC concentrations of methane, a greenhouse gas, are increasing at a rate of about 1% yr-1 (refs 1-4). Oxidation by methylotrophic bacteria in soil is the largest terrestrial sink for atmospheric CH4, and is estimated to consume about 30?? 1012 g CH4 yr-1 (refs 4-6). Spatial and temporal variability in the rate of soil CH4 consumption are incompletely understood6-19, as are the apparent inhibitory12,13,18 or enhancing20 effects of changes in land use. Dry deserts, which constitute 20% of total land surface, are not currently included in global soil uptake estimates. Here we describe measurements of the rate of uptake of atmospheric CH4 by undisturbed desert soils. We observed rates as great as 4.38 mg CH4 m-2 day-1; 50% of the measured rates were between 0.24 and 0.92 mg CH4 m2 d-1. Uptake of CH4 by desert soil is enhanced by rainfall after an initial soil-drainage period - opposite to the response of temperate forest soils12. Methane is consumed to a depth of about 2 m, allowing for deep removal of atmospheric CH4 if near-surface conditions are unfavourable for consumption. On the basis of an annual average CH4 consumption rate of 0.66 mg CH4 m-2 d-1, we estimate that the global CH4 sink term needs to be increased by about 7 ?? 1012 g yr-1 to account for the contribution of desert soils.

  13. Redox controls on methane formation, migration and fate in shallow aquifers

    NASA Astrophysics Data System (ADS)

    Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Bayegnak, Guy; Millot, Romain; Kloppmann, Wolfram

    2016-07-01

    Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish (a) natural in situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. This study combines aqueous and gas (dissolved and free) geochemical and isotope data from 372 groundwater samples obtained from 186 monitoring wells of the provincial Groundwater Observation Well Network (GOWN) in Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. We investigated whether methane occurring in shallow groundwater formed in situ, or whether it migrated into the shallow aquifers from elsewhere in the stratigraphic column. It was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of biogenic methane (> 0.01 mM or > 0.2 mgL-1), characterized by δ13CCH4 values < -55 ‰, occurred in anoxic Na-Cl, Na-HCO3, and Na-HCO3-Cl type groundwaters with negligible concentrations of nitrate and sulfate suggesting that methane was formed in situ under methanogenic conditions for 39.1 % of the samples. In only a few cases (3.7 %) was methane of biogenic origin found in more oxidizing shallow aquifer portions suggesting limited upward migration from deeper methanogenic aquifers. Of the samples, 14.1 % contained methane with δ13CCH4 values > -54 ‰, potentially suggesting a thermogenic origin, but aqueous and isotope

  14. Anomalous waveforms observed in laboratory-formed gas hydrate-bearing and ice-bearing sediments

    USGS Publications Warehouse

    Lee, M.W.; Waite, W.F.

    2011-01-01

    Acoustic transmission measurements of compressional, P, and shear, S, wave velocities rely on correctly identifying the P- and S-body wave arrivals in the measured waveform. In cylindrical samples for which the sample is much longer than the acoustic wavelength, these body waves can be obscured by high-amplitude waveform features arriving just after the relatively small-amplitude P-body wave. In this study, a normal mode approach is used to analyze this type of waveform, observed in sediment containing gas hydrate or ice. This analysis extends an existing normal-mode waveform propagation theory by including the effects of the confining medium surrounding the sample, and provides guidelines for estimating S-wave velocities from waveforms containing multiple large-amplitude arrivals. ?? 2011 Acoustical Society of America.

  15. Water Retention Curve and Relative Permeability for Gas Production from Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Mahabadi, N.; Dai, S.; Seol, Y.; Jang, J.

    2014-12-01

    Water retention curve (soil water characteristic curve SWCC) and relative permeability equations are important to determine gas and water production for gas hydrate development. However, experimental studies to determine fitting parameters of those equations are not available in the literature. The objective of this research is to obtain reliable parameters for capillary pressure functions and relative permeability equations applicable to hydrate dissociation and gas production. In order to achieve this goal, (1) micro X-ray Computer Tomography (CT) is used to scan the specimen under 10MPa effective stress, (2) a pore network model is extracted from the CT image, (3) hydrate dissociation and gas expansion are simulated in the pore network model, (4) the parameters for the van Genuchten-type soil water characteristic curve and relative permeability equation during gas expansion are suggested. The research outcome will enhance the ability of numerical simulators to predict gas and water production rate.

  16. Anomalous waveforms observed in laboratory-formed gas hydrate-bearing and ice-bearing sediments

    PubMed Central

    Lee, Myung W.; Waite, William F.

    2011-01-01

    Acoustic transmission measurements of compressional, P, and shear, S, wave velocities rely on correctly identifying the P- and S-body wave arrivals in the measured waveform. In cylindrical samples for which the sample is much longer than the acoustic wavelength, these body waves can be obscured by high-amplitude waveform features arriving just after the relatively small-amplitude P-body wave. In this study, a normal mode approach is used to analyze this type of waveform, observed in sediment containing gas hydrate or ice. This analysis extends an existing normal-mode waveform propagation theory by including the effects of the confining medium surrounding the sample, and provides guidelines for estimating S-wave velocities from waveforms containing multiple large-amplitude arrivals. PMID:21476628

  17. Electrical anisotropy of gas hydrate-bearing sand reservoirs in the Gulf of Mexico

    USGS Publications Warehouse

    Cook, Anne E.; Anderson, Barbara I.; Rasmus, John; Sun, Keli; Li, Qiming; Collett, Timothy S.; Goldberg, David S.

    2012-01-01

    We present new results and interpretations of the electricalanisotropy and reservoir architecture in gashydrate-bearingsands using logging data collected during the Gulf of MexicoGasHydrate Joint Industry Project Leg II. We focus specifically on sandreservoirs in Hole Alaminos Canyon 21 A (AC21-A), Hole Green Canyon 955 H (GC955-H) and Hole Walker Ridge 313 H (WR313-H). Using a new logging-while-drilling directional resistivity tool and a one-dimensional inversion developed by Schlumberger, we resolve the resistivity of the current flowing parallel to the bedding, R| and the resistivity of the current flowing perpendicular to the bedding, R|. We find the sandreservoir in Hole AC21-A to be relatively isotropic, with R| and R| values close to 2 Ω m. In contrast, the gashydrate-bearingsandreservoirs in Holes GC955-H and WR313-H are highly anisotropic. In these reservoirs, R| is between 2 and 30 Ω m, and R| is generally an order of magnitude higher. Using Schlumberger's WebMI models, we were able to replicate multiple resistivity measurements and determine the formation resistivity the gashydrate-bearingsandreservoir in Hole WR313-H. The results showed that gashydrate saturations within a single reservoir unit are highly variable. For example, the sand units in Hole WR313-H contain thin layers (on the order of 10-100 cm) with varying gashydrate saturations between 15 and 95%. Our combined modeling results clearly indicate that the gashydrate-bearingsandreservoirs in Holes GC955-H and WR313-H are highly anisotropic due to varying saturations of gashydrate forming in thin layers within larger sand units.

  18. Gas migration into gas hydrate-bearing sediments on the southern Hikurangi margin of New Zealand

    NASA Astrophysics Data System (ADS)

    Crutchley, G. J.; Fraser, D. R. A.; Pecher, I. A.; Gorman, A. R.; Maslen, G.; Henrys, S. A.

    2015-02-01

    We present multichannel seismic data from New Zealand's Hikurangi subduction margin that show widespread evidence for gas migration into the field of gas hydrate stability. Gas migration along stratigraphic layers into the hydrate system manifests itself as highly reflective segments of dipping strata that originate at the base of hydrate stability and extend some distance toward the seafloor. The highly reflective segments exhibit the same polarity as the seafloor reflection, indicating that localized gas hydrate precipitation from gas-charged fluids within relatively permeable layers has occurred. High-density velocity analysis shows that these layer-constrained gas hydrate accumulations are underlain by thick (up to ~500 m) free gas zones, which provide the source for focused gas migration into the hydrate layer. In addition to gas being channeled along layers, we also interpret gas migration through a fault zone into the field of hydrate stability; in this case, a low-velocity layer within the hydrate stability zone extends laterally away from the fault, which might indicate that gas-charged fluids have also migrated away from the fault along strata. At this site, where both dipping strata and faulting seem to influence fluid migration, we observe anomalously high velocities at the base of hydrate stability that we interpret as concentrated gas hydrates. Our results give insight into how shallow fluid flow responds to permeability contrasts between strata, fault zones, and perhaps also the gas hydrate system itself. Ultimately, these relationships can lead to gas migration across the base of hydrate stability and the precipitation of concentrated hydrate deposits.

  19. Anaerobic Methane Oxidation: Occurrence and Ecology

    PubMed Central

    Zehnder, Alexander J. B.; Brock, Thomas D.

    1980-01-01

    Anoxic sediments and digested sewage sludge anaerobically oxidized methane to carbon dioxide while producing methane. This strictly anaerobic process showed a temperature optimum between 25 and 37°C, indicating an active microbial participation in this reaction. Methane oxidation in these anaerobic habitats was inhibited by oxygen. The rate of the oxidation followed the rate of methane production. The observed anoxic methane oxidation in Lake Mendota and digested sewage sludge was more sensitive to 2-bromoethanesulfonic acid than the simultaneous methane formation. Sulfate diminished methane formation as well as methane oxidation. However, in the presence of iron and sulfate the ratio of methane oxidized to methane formed increased markedly. Manganese dioxide and higher partial pressures of methane also stimulated the oxidation. The rate of methane oxidation in untreated samples was approximately 2% of the CH4 production rate in Lake Mendota sediments and 8% of that in digested sludge. This percentage could be increased up to 90% in sludge in the presence of 10 mM ferrous sulfate and at a partial pressure of methane of 20 atm (2,027 kPa). PMID:16345488

  20. Why can water cages adsorb aqueous methane? A potential of mean force calculation on hydrate nucleation mechanisms.

    PubMed

    Guo, Guang-Jun; Li, Meng; Zhang, Yi-Gang; Wu, Chang-Hua

    2009-11-28

    By performing constrained molecular dynamics simulations in the methane-water system, we successfully calculated the potential of mean force (PMF) between a dodecahedral water cage (DWC) and dissolved methane for the first time. As a function of the distance between DWC and methane, this is characterized by a deep well at approximately 6.2 A and a shallow well at approximately 10.2 A, separated by a potential barrier at approximately 8.8 A. We investigated how the guest molecule, cage rigidity and the cage orientation affected the PMF. The most important finding is that the DWC itself strongly adsorbs methane and the adsorption interaction is independent of the guests. Moreover, the activation energy of the DWC adsorbing methane is comparable to that of hydrogen bonds, despite differing by a factor of approximately 10% when considering different water-methane interaction potentials. We explain that the cage-methane adsorption interaction is a special case of the hydrophobic interaction between methane molecules. The strong net attraction in the DWC shell with radii between 6.2 and 8.8 A may act as the inherent driving force that controls hydrate formation. A cage adsorption hypothesis for hydrate nucleation is thus proposed and discussed. PMID:19890529

  1. Why can water cages adsorb aqueous methane? A potential of mean force calculation on hydrate nucleation mechanisms.

    PubMed

    Guo, Guang-Jun; Li, Meng; Zhang, Yi-Gang; Wu, Chang-Hua

    2009-11-28

    By performing constrained molecular dynamics simulations in the methane-water system, we successfully calculated the potential of mean force (PMF) between a dodecahedral water cage (DWC) and dissolved methane for the first time. As a function of the distance between DWC and methane, this is characterized by a deep well at approximately 6.2 A and a shallow well at approximately 10.2 A, separated by a potential barrier at approximately 8.8 A. We investigated how the guest molecule, cage rigidity and the cage orientation affected the PMF. The most important finding is that the DWC itself strongly adsorbs methane and the adsorption interaction is independent of the guests. Moreover, the activation energy of the DWC adsorbing methane is comparable to that of hydrogen bonds, despite differing by a factor of approximately 10% when considering different water-methane interaction potentials. We explain that the cage-methane adsorption interaction is a special case of the hydrophobic interaction between methane molecules. The strong net attraction in the DWC shell with radii between 6.2 and 8.8 A may act as the inherent driving force that controls hydrate formation. A cage adsorption hypothesis for hydrate nucleation is thus proposed and discussed.

  2. Methane release from pingo-like features across the South Kara Sea shelf, an area of thawing offshore permafrost

    NASA Astrophysics Data System (ADS)

    Serov, Pavel; Portnov, Alexey; Mienert, Jurgen; Semenov, Peter; Ilatovskaya, Polina

    2015-08-01

    The Holocene marine transgression starting at ~19 ka flooded the Arctic shelves driving extensive thawing of terrestrial permafrost. It thereby promoted methanogenesis within sediments, the dissociation of gas hydrates, and the release of formerly trapped gas, with the accumulation in pressure of released methane eventually triggering blowouts through weakened zones in the overlying and thinned permafrost. Here we present a range of geophysical and chemical scenarios for the formation of pingo-like formations (PLFs) leading to potential blowouts. Specifically, we report on methane anomalies from the South Kara Sea shelf focusing on two PLFs imaged from high-resolution seismic records. A variety of geochemical methods are applied to study concentrations and types of gas, its character, and genesis. PLF 1 demonstrates ubiquitously low-methane concentrations (14.2-55.3 ppm) that are likely due to partly unfrozen sediments with an ice-saturated internal core reaching close to the seafloor. In contrast, PLF 2 reveals anomalously high-methane concentrations of >120,000 ppm where frozen sediments are completely absent. The methane in all recovered samples is of microbial and not of thermogenic origin from deep hydrocarbon sources. However, the relatively low organic matter content (0.52-1.69%) of seafloor sediments restricts extensive in situ methane production. As a consequence, we hypothesize that the high-methane concentrations at PLF 2 are due to microbial methane production and migration from a deeper source.

  3. Search for methane isotope fractionation due to Rayleigh distillation on Titan

    NASA Astrophysics Data System (ADS)

    Ádámkovics, Máté; Mitchell, Jonathan L.

    2016-09-01

    We search for meridional variation in the abundance of CH3D relative to CH4 on Titan using near-IR spectra obtained with NIRSPAO at Keck, which have a photon-limited signal-to-noise ratio of ∼50. Our observations can rule out a larger than 10% variation in the column of CH3D below 50 km. The preferential condensation of the heavy isotopologues will fractionate methane by reducing CH3D in the remaining vapor, and therefore these observations place limits on the amount of condensation that occurs in the troposphere. While previous estimates of CH3D fractionation on Titan have estimated an upper limit of -6‰, assuming a solid condensate, we consider more recent laboratory data for the equilibrium fractionation over liquid methane, and use a Rayleigh distillation model to calculate fractionation in an ascending parcel of air that is following a moist adiabat. We find that deep, precipitating convection can enhance the fractionation of the remaining methane vapor by -10 to -40‰, depending on the final temperature of the rising parcel. By relating fractionation of our reference parcel model to the pressure level where the moist adiabat achieves the required temperature, we argue that the measured methane fractionation constrains the outflow level for a deep convective event. Observations with a factor of at least 4-6 times larger signal-to-noise are required to detect this amount of fractionation, depending on the altitude range over which the outflow from deep convection occurs.

  4. Origins, characteristics, controls, and economic viabilities of deep- basin gas resources

    USGS Publications Warehouse

    Price, L.C.

    1995-01-01

    Dry-gas deposits (methane ???95% of the hydrocarbon (HC) gases) are thought to originate from in-reservoir thermal cracking of oil and C2+ HC gases to methane. However, because methanes from Anadarko Basin dry-gas deposits do not carry the isotopic signature characteristics of C15+ HC destruction, an origin of these methanes from this process is considered improbable. Instead, the isotopic signature of these methanes suggests that they were cogenerated with C15+ HC's. Only a limited resource of deep-basin gas deposits may be expected by the accepted model for the origin of dry-gas deposits because of a limited number of deep-basin oil deposits originally available to be thermally converted to dry gas. However, by the models of this paper (inefficient source-rock oil and gas expulsion, closed fluid systems in petroleum-basin depocenters, and most dry-gas methane cogenerated with C15+ HC's), very large, previously unrecognized, unconventional, deep-basin gas resources are expected. -from Author

  5. Controls on subsurface methane fluxes and shallow gas formation in Baltic Sea sediment (Aarhus Bay, Denmark)

    NASA Astrophysics Data System (ADS)

    Flury, Sabine; Røy, Hans; Dale, Andrew W.; Fossing, Henrik; Tóth, Zsuzsanna; Spiess, Volkhard; Jensen, Jørn Bo; Jørgensen, Bo Barker

    2016-09-01

    Shallow gas accumulates in coastal marine sediments when the burial rate of reactive organic matter beneath the sulfate zone is sufficiently high and the methanogenic zone is sufficiently deep. We investigated the controls on methane production and free methane gas accumulation along a 400 m seismo-acoustic transect across a sharp transition from gas-free into gas-bearing sediment in Aarhus Bay (Denmark). Twelve gravity cores were taken, in which the pore water was analyzed for inorganic solutes while rates of organic carbon mineralization were measured experimentally by 35SO42- radiotracer method. The thickness of organic-rich Holocene mud increased from 5 to 10 m along the transect concomitant with a shallowing of the depth of the sulfate-methane transition from >4 m to 2.5 m. In spite of drastic differences in the distribution of methane and sulfate in the sediment along the transect, there were only small differences in total mineralization, and methanogenesis was only equivalent to about 1% of sulfate reduction. Shallow gas appeared where the mud thickness exceeded 8-9 m. Rates of methanogenesis increased along the transect as did the upward diffusive flux of methane. Interestingly, the increase in the sedimentation rate and Holocene mud thickness had only a modest direct effect on methanogenesis rates in deep sediments. This increase in methane flux, however, triggered a shallowing of the sulfate-methane transition which resulted in a large increase in methanogenesis at the top of the methanogenic zone. Thus, our results demonstrate a positive feedback mechanism that causes a strong enhancement of methanogenesis and explains the apparently abrupt appearance of gas when a threshold thickness of organic-rich mud is exceeded.

  6. Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Mountjoy, Joshu J.; Pecher, Ingo; Henrys, Stuart; Crutchley, Gareth; Barnes, Philip M.; Plaza-Faverola, Andreia

    2014-11-01

    and seismic data from a submarine landslide complex east of New Zealand indicate flow-like deformation within gas hydrate-bearing sediment. This "creeping" deformation occurs immediately downslope of where the base of gas hydrate stability reaches the seafloor, suggesting involvement of gas hydrates. We present evidence that, contrary to conventional views, gas hydrates can directly destabilize the seafloor. Three mechanisms could explain how the shallow gas hydrate system could control these landslides. (1) Gas hydrate dissociation could result in excess pore pressure within the upper reaches of the landslide. (2) Overpressure below low-permeability gas hydrate-bearing sediments could cause hydrofracturing in the gas hydrate zone valving excess pore pressure into the landslide body. (3) Gas hydrate-bearing sediment could exhibit time-dependent plastic deformation enabling glacial-style deformation. We favor the final hypothesis that the landslides are actually creeping seafloor glaciers. The viability of rheologically controlled deformation of a hydrate sediment mix is supported by recent laboratory observations of time-dependent deformation behavior of gas hydrate-bearing sands. The controlling hydrate is likely to be strongly dependent on formation controls and intersediment hydrate morphology. Our results constitute a paradigm shift for evaluating the effect of gas hydrates on seafloor strength which, given the widespread occurrence of gas hydrates in the submarine environment, may require a reevaluation of slope stability following future climate-forced variation in bottom-water temperature.

  7. 46 CFR 154.703 - Methane (LNG).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Cargo Pressure and Temperature Control § 154.703 Methane (LNG). Unless a cargo tank carrying methane (LNG)...

  8. Biogeochemistry: Rebalancing the global methane budget

    NASA Astrophysics Data System (ADS)

    Allen, Grant

    2016-10-01

    A database of the carbon-isotope 'fingerprints' of methane has been used to constrain the contributions of different sources to the global methane budget. The surprising results have implications for climate prediction. See Letter p.88

  9. Hello, Water -- Good-bye, Methane

    NASA Video Gallery

    An animation shows carbon, hydrogen and oxygen atoms. Two hydrogen atoms join each oxygen atom to make water, or H2O. Four hydrogen atoms join a carbon atom to make methane, or CH4. The methane the...

  10. Gas hydrates (clathrates) causing pore-water freshening and oxygen isotope fractionation in deep-water sedimentary sections of terrigenous continental margins

    USGS Publications Warehouse

    Hesse, R.; Harrison, W.E.

    1981-01-01

    The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10-20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9???). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with 18O-enrichment in the hydrate explaining increasingly more positive ??18O values in the pore fluids recovered (after hydrate dissociation) with depth. ?? 1981.

  11. Solid methane on Triton and Pluto - 3- to 4-micron spectrophotometry

    SciTech Connect

    Spencer, J.R.; Buie, M.W.; Bjoraker, G.L. Space Telescope Science Institute, Baltimore, MD NASA, Goddard Space Flight Center, Greenbelt, MD )

    1990-12-01

    Methane has been identified in the Pluto/Charon system on the basis of absorption features in the reflectance spectrum at 1.5 and 2.3 microns; attention is presently given to observations of a 3.25 micron-centered deep absorption feature in Triton and Pluto/Charon system reflectance spectra. This absorption may indicate the presence of solid methane, constituting either the dominant surface species or a mixture with a highly transparent substance, such as N2 frost. 35 refs.

  12. Constraining the 2012-2014 growing season Alaskan methane budget using CARVE aircraft measurements

    NASA Astrophysics Data System (ADS)

    Hartery, S.; Chang, R. Y. W.; Commane, R.; Lindaas, J.; Miller, S. M.; Wofsy, S. C.; Karion, A.; Sweeney, C.; Miller, C. E.; Dinardo, S. J.; Steiner, N.; McDonald, K. C.; Watts, J. D.; Zona, D.; Oechel, W. C.; Kimball, J. S.; Henderson, J.; Mountain, M. E.

    2015-12-01

    Soil in northen latitudes contains rich carbon stores which have been historically preserved via permafrost within the soil bed; however, recent surface warming in these regions is allowing deeper soil layers to thaw, influencing the net carbon exchange from these areas. Due to the extreme nature of its climate, these eco-regions remain poorly understood by most global models. In this study we analyze methane fluxes from Alaska using in situ aircraft observations from the 2012-2014 Carbon in Arctic Reservoir Vulnerability Experiment (CARVE). These observations are coupled with an atmospheric particle transport model which quantitatively links surface emissions to atmospheric observations to make regional methane emission estimates. The results of this study are two-fold. First, the inter-annual variability of the methane emissions was found to be <1 Tg over the area of interest and is largely influenced by the length of time the deep soil remains unfrozen. Second, the resulting methane flux estimates and mean soil parameters were used to develop an empirical emissions model to help spatially and temporally constrain the methane exchange at the Alaskan soil surface. The empirical emissions model will provide a basis for exploring the sensitivity of methane emissions to subsurface soil temperature, soil moisture, organic carbon content, and other parameters commonly used in process-based models.

  13. Method for the photocatalytic conversion of methane

    DOEpatents

    Noceti, Richard P.; Taylor, Charles E.; D'Este, Joseph R.

    1998-01-01

    A method for converting methane to methanol is provided comprising subjecting the methane to visible light in the presence of a catalyst and an electron transfer agent. Another embodiment of the invention provides for a method for reacting methane and water to produce methanol and hydrogen comprising preparing a fluid containing methane, an electron transfer agent and a photolysis catalyst, and subjecting said fluid to visible light for an effective period of time.

  14. Method for the photocatalytic conversion of methane

    DOEpatents

    Noceti, R.P.; Taylor, C.E.; D`Este, J.R.

    1998-02-24

    A method for converting methane to methanol is provided comprising subjecting the methane to visible light in the presence of a catalyst and an electron transfer agent. Another embodiment of the invention provides for a method for reacting methane and water to produce methanol and hydrogen comprising preparing a fluid containing methane, an electron transfer agent and a photolysis catalyst, and subjecting said fluid to visible light for an effective period of time. 3 figs.

  15. Potential methane reservoirs beneath Antarctica.

    PubMed

    Wadham, J L; Arndt, S; Tulaczyk, S; Stibal, M; Tranter, M; Telling, J; Lis, G P; Lawson, E; Ridgwell, A; Dubnick, A; Sharp, M J; Anesio, A M; Butler, C E H

    2012-08-30

    Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

  16. Potential methane reservoirs beneath Antarctica.

    PubMed

    Wadham, J L; Arndt, S; Tulaczyk, S; Stibal, M; Tranter, M; Telling, J; Lis, G P; Lawson, E; Ridgwell, A; Dubnick, A; Sharp, M J; Anesio, A M; Butler, C E H

    2012-08-30

    Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage. PMID:22932387

  17. Optical constants of solid methane

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Thompson, W. R.; Sagan, C.; Arakawa, E. T.; Bruel, C.; Judish, J. P.; Khanna, R. K.; Pollack, J. B.

    1990-01-01

    Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented on the optical constants of solid methane for the 0.4 to 2.6 micrometer region. Deposition onto a substrate at 10 K produces glassy (semi-amorphous) material. Annealing this material at approximately 33 K for approximately 1 hour results in a crystalline material as seen by sharper, more structured bands and negligible background extinction due to scattering. The constant k is reported for both the amorphous and the crystalline (annealed) states. Typical values (at absorption maxima) are in the .001 to .0001 range. Below lambda = 1.1 micrometers the bands are too weak to be detected by transmission through the films less than or equal to 215 micrometers in thickness, employed in the studies to date. Using previously measured values of the real part of the refractive index, n, of liquid methane at 110 K, n is computed for solid methane using the Lorentz-Lorenz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for

  18. Estimates of Vertical Methane Fluxes in Porangahau Ridge Sediment on the Hikurangi Margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Coffin, R.; Hamdan, L.; Wood, W.; Pohlman, J.; Smith, J.; Henrys, S.; Pecher, I.

    2007-12-01

    methanogenesis and variable rates of anaerobic methane oxidation (AOM). Above the SMI the methane δ13C was elevated up to -45 ppt and corresponded to low methane concentrations likely resulting from AOM at the SMI. Vertical methane fluxes in this area are within the range observed in other seep areas such as Atwater Valley in the Gulf of Mexico and mid Chilean margin (-9 to -362 mM m-2 a-1). Because methane flux estimates can not be attributed to near surface methanogenesis alone, these data suggest deep sediment methane pools are present along the Porangahau Ridge.

  19. Gas Hydrates and Perturbed Permafrost: Can Thermokarst Lakes Leak Hydrate-Derived Methane?

    NASA Astrophysics Data System (ADS)

    Ruppel, C.; Walter, K.; Pohlman, J.; Wooller, M.

    2008-12-01

    Thermokarst lakes are common features in the continuous permafrost of Siberia, the Alaskan North Slope, and the Canadian Arctic and have been intensely studied as the loci of rapid and substantial methane flux to the atmosphere. Previous numerical modeling has constrained the conditions under which deep thermokarst lakes can develop organic-rich thaw bulbs (talik) tens of meters thick, and seismic surveys have imaged thaw bulbs more than 75 m thick beneath some thermokarst lakes. Microbial processes active in talik organic material are likely the predominant source for thermokarst methane emissions, although coalbed methane and methane associated with conventional hydrocarbons may contribute in some geologic settings. Here we evaluate the possibility that another source--methane released from dissociating gas hydrate--could contribute to methane emissions from these lakes. Temperatures within and beneath thermokarst lakes are significantly warmer than those in surrounding permafrost, and these relatively warm conditions can persist to depths several times greater than the thickness of the thaw bulb. For a 95-m-thick thaw bulb and a geothermal gradient consistent with the regional top of gas hydrate stability at ~200 m depth, the warmer temperatures beneath a thermokarst lake could lead to destabilization of up to 75 m of gas hydrate. Arguably, the presence of gas hydrate near the top of the stability zone in permafrost regions has not yet been observed. Nonetheless, the potential dissociation of such relatively shallow gas hydrate and the widespread availability in terrestrial settings of high permeability conduits (e.g., faults, sandy strata) that could facilitate the migration of hydrate-derived methane to the surface render this an important topic for future investigation. The susceptibility of permafrost gas hydrate zones to thermal perturbations is in sharp contrast to the situation in conventional marine hydrate provinces. There, gas hydrate first dissociates

  20. Is there methane on Mars?

    NASA Astrophysics Data System (ADS)

    Zahnle, Kevin; Freedman, Richard S.; Catling, David C.

    2011-04-01

    There have been several reports of methane on Mars at the 10-60 ppbv level. Most suggest that methane is both seasonally and latitudinally variable. Here we review why variable methane on Mars is physically and chemically implausible, and then we critically review the published reports. There is no known mechanism for destroying methane chemically on Mars. But if there is one, methane oxidation would deplete the O 2 in Mars's atmosphere in less than 10,000 years unless balanced by an equally large unknown source of oxidizing power. Physical sequestration does not raise these questions, but adsorption in the regolith or condensation in clathrates ignore competition for adsorption sites or are inconsistent with clathrate stability, respectively. Furthermore, any mechanism that relies on methane's van der Waals' attraction is inconsistent with the continued presence of Xe in the atmosphere at the 60 ppbv level. We then use the HITRAN database and transmission calculations to identify and characterize the absorption lines that would be present on Earth or Mars at the wavelengths of the published observations. These reveal strong competing telluric absorption that is most problematic at just those wavelengths where methane's signature seems most clearly seen from Earth. The competing telluric lines must be removed with models. The best case for martian methane was made for the 12CH 4ν3 R0 and R1 lines seen in blueshift when Mars was approaching Earth in early 2003 (Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T., Bonev, B.P., DiSanti, M.A., Mandell, A.M., Smith, M.D. [2009]. Science 323, 1041-1045). For these the Doppler shift moves the two martian lines into near coincidence with telluric 13CH 4ν3 R1 and R2 lines that are 10-50× stronger than the inferred martian lines. By contrast, the 12CH 4ν3 R0 and R1 lines when observed in redshift do not contend with telluric 13CH 4. For these lines, Mumma et al.'s observations and analyses are consistent with an

  1. Coalbed methane production case histories

    SciTech Connect

    Not Available

    1981-02-01

    The production of methane gas from coal and coal-bearing rocks is one of the prime objectives of the Department of Energy's Methane Recovery from Coalbeds Project. This report contains brief description of wells that are presently producing gas from coal or coal-bearing rocks. Data from three gob gas production areas in Illinois, an in-mine horizontal borehole degasification, and eleven vertical boreholes are presented. Production charts and electric logs of the producing zones are included for some of the wells. Additional information on dry gas production from the San Juan Basin, Colorado/New Mexico and the Greater Green River Coal Region, Colorado/Wyoming is also included.

  2. Terminating marine methane bubbles by superhydrophobic sponges.

    PubMed

    Chen, Xiao; Wu, Yuchen; Su, Bin; Wang, Jingming; Song, Yanlin; Jiang, Lei

    2012-11-14

    Marine methane bubbles are absorbed, steadily stored, and continuously transported based on the employment of superhydrophobic sponges. Antiwetting sponges are water-repellent in the atmosphere and absorb gas bubbles under water. Their capacity to store methane bubbles increases with enhanced submerged depth. Significantly, trapped methane bubbles can be continuously transported driven by differential pressure.

  3. APPROACH FOR ESTIMATING GLOBAL LANDFILL METHANE EMISSIONS

    EPA Science Inventory

    The report is an overview of available country-specific data and modeling approaches for estimating global landfill methane. Current estimates of global landfill methane indicate that landfills account for between 4 and 15% of the global methane budget. The report describes an ap...

  4. Are methane production and cattle performance related?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methane is a product of fermentation of feed in ruminant animals. Approximately 2 -12% of the gross energy consumed by cattle is released through enteric methane production. There are three primary components that contribute to the enteric methane footprint of an animal. Those components are dry ...

  5. 78 FR 37536 - Methane Hydrate Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. The Federal... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of...

  6. 40 CFR 721.4820 - Methane, bromodifluoro-.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Methane, bromodifluoro-. 721.4820... Substances § 721.4820 Methane, bromodifluoro-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as methane, bromodifluoro- is subject to reporting...

  7. 30 CFR 75.342 - Methane monitors.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Methane monitors. 75.342 Section 75.342 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.342 Methane monitors. (a)(1) MSHA approved methane monitors shall be installed on all face cutting machines, continuous miners, longwall...

  8. 30 CFR 75.342 - Methane monitors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Methane monitors. 75.342 Section 75.342 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.342 Methane monitors. (a)(1) MSHA approved methane monitors shall be installed on all face cutting machines, continuous miners, longwall...

  9. 40 CFR 721.4820 - Methane, bromodifluoro-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Methane, bromodifluoro-. 721.4820... Substances § 721.4820 Methane, bromodifluoro-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as methane, bromodifluoro- is subject to reporting...

  10. 30 CFR 75.342 - Methane monitors.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Methane monitors. 75.342 Section 75.342 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.342 Methane monitors. (a)(1) MSHA approved methane monitors shall be installed on all face cutting machines, continuous miners, longwall...

  11. 76 FR 59667 - Methane Hydrate Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-27

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... Meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. Federal... of the Committee: The purpose of the Methane Hydrate Advisory Committee is to provide advice...

  12. 78 FR 26337 - Methane Hydrate Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... Meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. The Federal... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of...

  13. 30 CFR 75.342 - Methane monitors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Methane monitors. 75.342 Section 75.342 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.342 Methane monitors. (a)(1) MSHA approved methane monitors shall be installed on all face cutting machines, continuous miners, longwall...

  14. Sensitivity of the recent methane budget to LMDz sub-grid-scale physical parameterizations

    NASA Astrophysics Data System (ADS)

    Locatelli, R.; Bousquet, P.; Saunois, M.; Chevallier, F.; Cressot, C.

    2015-09-01

    With the densification of surface observing networks and the development of remote sensing of greenhouse gases from space, estimations of methane (CH4) sources and sinks by inverse modeling are gaining additional constraining data but facing new challenges. The chemical transport model (CTM) linking the flux space to methane mixing ratio space must be able to represent these different types of atmospheric constraints for providing consistent flux estimations. Here we quantify the impact of sub-grid-scale physical parameterization errors on the global methane budget inferred by inverse modeling. We use the same inversion setup but different physical parameterizations within one CTM. Two different schemes for vertical diffusion, two others for deep convection, and one additional for thermals in the planetary boundary layer (PBL) are tested. Different atmospheric methane data sets are used as constraints (surface observations or satellite retrievals). At the global scale, methane emissions differ, on average, from 4.1 Tg CH4 per year due to the use of different sub-grid-scale parameterizations. Inversions using satellite total-column mixing ratios retrieved by GOSAT are less impacted, at the global scale, by errors in physical parameterizations. Focusing on large-scale atmospheric transport, we show that inversions using the deep convection scheme of Emanuel (1991) derive smaller interhemispheric gradients in methane emissions, indicating a slower interhemispheric exchange. At regional scale, the use of different sub-grid-scale parameterizations induces uncertainties ranging from 1.2 % (2.7 %) to 9.4 % (14.2 %) of methane emissions when using only surface measurements from a background (or an extended) surface network. Moreover, spatial distribution of methane emissions at regional scale can be very different, depending on both the physical parameterizations used for the modeling of the atmospheric transport and the observation data sets used to constrain the inverse

  15. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans.

    PubMed

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end. PMID:26739600

  16. Retrievals of boundary layer methane and isotope fractionation on Titan

    NASA Astrophysics Data System (ADS)

    Adamkovics, Mate; Lora, Juan M.; Mitchell, Jonathan L.

    2016-10-01

    The amount of methane in the boundary layer on Titan is an interesting diagnostic of whether or not it might be seeping out of the regolith. We know that kinetic fractionation of methane isotopes can be diagnostic of evaporation at the surface and condensation in the atmosphere. If a parcel is constrained to follow a moist adiabat while condensation occurs, we can predict the amount of fractionation that is expected (Ádámkovics & Mitchell, 2016). We will present our most recent efforts to measure boundary layer methane abundance and isotopic composition, which include our recently published Keck NIRSPAO observations from 17 July 2014 (Ádámkovics et al., 2016), as well as preliminary results from follow-up measurements made on 15 May 2016. Our measurements are tantalizingly close to being able to distinguish between different hydrological parameterizations of the polar regions in the Titan Atmospheric Model (Lora & Ádámkovics, 2016). We will discuss the systematic uncertainties that can be evaluated with the combination of these two datasets and the prospects for exceptionally high S/N observations via particularly deep integrations over multiple nights.

  17. Bacterial dominance in subseafloor sediments characterized by methane hydrates

    USGS Publications Warehouse

    Briggs, Brandon R.; Inagaki, Fumio; Morono, Yuki; Futagami, Taiki; Huguet, Carme; Rosell-Mele, Antoni; Lorenson, T.D.; Colwell, Frederick S.

    2015-01-01

    The degradation of organic carbon in subseafloor sediments on continental margins contributes to the largest reservoir of methane on Earth. Sediments in the Andaman Sea are composed of ~ 1% marine-derived organic carbon and biogenic methane is present. Our objective was to determine microbial abundance and diversity in sediments that transition the gas hydrate occurrence zone (GHOZ) in the Andaman Sea. Microscopic cell enumeration revealed that most sediment layers harbored relatively low microbial abundance (103–105 cells cm−3). Archaea were never detected despite the use of both DNA- and lipid-based methods. Statistical analysis of terminal restriction fragment length polymorphisms revealed distinct microbial communities from above, within, and below the GHOZ, and GHOZ samples were correlated with a decrease in organic carbon. Primer-tagged pyrosequences of bacterial 16S rRNA genes showed that members of the phylum Firmicutes are predominant in all zones. Compared with other seafloor settings that contain biogenic methane, this deep subseafloor habitat has a unique microbial community and the low cell abundance detected can help to refine global subseafloor microbial abundance.

  18. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans

    NASA Astrophysics Data System (ADS)

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (~2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.

  19. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans

    PubMed Central

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500–750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end. PMID:26739600

  20. The effect of elevated methane pressure on methane hydrate dissociation

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    Methane hydrate, equilibrated at P, T conditions within the hydrate stability field, was rapidly depressurized to 1.0 or 2.0 MPa and maintained at isobaric conditions outside its stability field, while the extent and rate of hydrate dissociation was measured at fixed, externally maintained temperatures between 250 and 288 K. The dissociation rate decreases with increasing pressure at a given temperature. Dissociation rates at 1.0 MPa parallel the complex, reproducible T-dependence previously observed between 250 and 272 K at 0.1 MPa. The lowest rates were observed near 268 K, such that >50% of the sample can persist for more than two weeks at 0.1 MPa to more than a month at 1 and 2 MPa. Varying the pressure stepwise in a single experiment increased or decreased the dissociation rate in proportion to the rates observed in the isobaric experiments, similar to the rate reversibility previously observed with stepwise changes in temperature at 0.1 MPa. At fixed P, T conditions, the rate of methane hydrate dissociation decreases monotonically with time, never achieving a steady rate. The relationship between time (t) and the extent of hydrate dissociation is empirically described by: Evolved gas (%) = A??tB where the pre-exponential term A ranges from 0 to 16% s-B and the exponent B is generally <1. Based on fits of the dissociation results to Equation 1 for the full range of temperatures (204 to 289 K) and pressures (0.1 to 2.0 MPa) investigated, the derived parameters can be used to predict the methane evolution curves for pure, porous methane hydrate to within ??5%. The effects of sample porosity and the presence of quartz sand and seawater on methane hydrate dissociation are also described using Equation 1.

  1. Exploration of deep intraterrestrial microbial life: current perspectives.

    PubMed

    Pedersen, K

    2000-04-01

    Intraterrestrial life has been found at depths of several thousand metres in deep sub-sea floor sediments and in the basement crust beneath the sediments. It has also been found at up to 2800-m depth in continental sedimentary rocks, 5300-m depth in igneous rock aquifers and in fluid inclusions in ancient salt deposits from salt mines. The biomass of these intraterrestrial organisms may be equal to the total weight of all marine and terrestrial plants. The intraterrestrial microbes generally seem to be active at very low but significant rates and several investigations indicate chemolithoautotrophs to form a chemosynthetic base. Hydrogen, methane and carbon dioxide gases are continuously generated in the interior of our planet and probably constitute sustainable sources of carbon and energy for deep intraterrestrial biosphere ecosystems. Several prospective research areas are foreseen to focus on the importance of microbial communities for metabolic processes such as anaerobic utilisation of hydrocarbons and anaerobic methane oxidation.

  2. Methane sources and emissions in Italy

    SciTech Connect

    Guidotti, G.R.; Castagnola, A.M.

    1994-12-31

    Methane emissions in Italy were assessed in the framework of the measures taken to follow out the commitments undertaken at the 1992 U.N. Conference for Environment and Development. Methane emissions of anthropic origin were estimated to be in the range of 1.6 to 2.3 million ton of methane per year. Some of these methane sources (natural gas production, transmission and distribution; rice paddies; managed livestock enteric fermentation and waste; solid waste landfills) are given here particular care as they mainly contribute to the total methane emission budget.

  3. Methane on Triton - Physical state and distribution

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.; Apt, J.

    1984-01-01

    Infrared spectrophotometric measurements of Neptune's satellite Triton obtained between 1980 and 1982 in the spectral range 0.8-2.5 microns show six individual absorption bands attributable to methane. An additional band in the Triton data is not methane. The Triton spectral data conform more closely to a laboratory spectrum of frozen methane than to a synthetic spectrum of methane gas computed for conditions of low temperature expected at the satellite. Additionally, the strength of the bands vary with Triton's orbital position. The data thus suggest that methane in the ice phase is mostly responsible for the bands in Triton's spectrum, and that the ice is distributed nonuniformly around the satellite's surface.

  4. Methane Dynamics in Flooded Lands

    EPA Science Inventory

    Methane (CH4) is the second most important anthropogenic greenhouse gas with a heat trapping capacity 34 times greater than that of carbon dioxide on a100 year time scale. Known anthropogenic CH4 sources include livestock production, rice agriculture, landfills, and natural gas m...

  5. Bis(2-chloroethoxy)methane

    Integrated Risk Information System (IRIS)

    Bis ( 2 - chloroethoxy ) methane ; CASRN 111 - 91 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for

  6. Methane flux from Minnesota peatlands

    SciTech Connect

    Crill, P.M.; Bartlett, K.B.; Harriss, R.C.; Gorham, E.; Verry, E.S. )

    1988-12-01

    Northern (> 40 deg N) wetlands have been suggested as the largest natural source of methane (CH{sub 4}) to the troposphere. To refine the authors estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Late spring and summer fluxes ranged from 11 to 866 mg CH{sub 4}/sq/m/day, averaging 207 mg CH{sub 4} sq/m/day overall. At Marcell Forest, forested bogs and fen sites had lower fluxes than open bogs. In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface. Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. It is estimated that the methane flux from all peatlands north of 40 deg may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH{sub 4} producing season, and the spatial and temporal variability of the flux. 60 refs., 7 figs., 5 tabs.

  7. Methane production by attached film

    DOEpatents

    Jewell, William J.

    1981-01-01

    A method for purifying wastewater of biodegradable organics by converting the organics to methane and carbon dioxide gases is disclosed, characterized by the use of an anaerobic attached film expanded bed reactor for the reaction process. Dilute organic waste material is initially seeded with a heterogeneous anaerobic bacteria population including a methane-producing bacteria. The seeded organic waste material is introduced into the bottom of the expanded bed reactor which includes a particulate support media coated with a polysaccharide film. A low-velocity upward flow of the organic waste material is established through the bed during which the attached bacterial film reacts with the organic material to produce methane and carbon dioxide gases, purified water, and a small amount of residual effluent material. The residual effluent material is filtered by the film as it flows upwardly through the reactor bed. In a preferred embodiment, partially treated effluent material is recycled from the top of the bed to the bottom of the bed for further treatment. The methane and carbon dioxide gases are then separated from the residual effluent material and purified water.

  8. Methane storage in molecular nanostructures

    NASA Astrophysics Data System (ADS)

    Adisa, Olumide O.; Cox, Barry J.; Hill, James M.

    2012-05-01

    We survey various molecular structures which have been proposed as possible nanocontainers for methane storage. These are molecular structures that have been investigated through either experiments, molecular dynamics simulations or mathematical modelling. Computational simulation and mathematical modelling play an important role in predicting and verifying experimental outcomes, but both have their limitations. Even though recent advances have greatly improved computations, due to the large number of atoms and force field calculations involved, computational simulations can still be time consuming as compared to an instantaneous mathematical modelling approach. On the other hand, underlying an ideal mathematical model, there are many assumptions and approximations, but such modelling often reveals the key physical parameters and optimal configurations. Here, we review methane adsorption for three conventional nanostructures, namely graphite, single and multi-walled carbon nanotubes, and nanotube bundles (including interstitial and groove sites), and we survey methane adsorption in other molecular structures including metal organic frameworks. We also include an examination of minimum binding energies, equilibrium distances, gravimetric and volumetric uptakes, volume available for adsorption, as well as the effects of temperature and pressure on the adsorption of methane onto these molecular structures.

  9. Methane on the greenhouse agenda

    NASA Technical Reports Server (NTRS)

    Hogan, Kathleen B.; Hoffman, John S.; Thompson, Anne M.

    1991-01-01

    Options for reducing methane emissions, which could have a significant effect on global warming, are addressed. Emissions from landfills, coal mining, oil and natural gas systems, ruminants, animal wastes and wastewater, rice cultivation, and biomass burning are considered. Methods for implementing these emission reductions are discussed.

  10. Ductile flow of methane hydrate

    USGS Publications Warehouse

    Durham, W.B.; Stern, L.A.; Kirby, S.H.

    2003-01-01

    Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

  11. Methane generation from waste materials

    DOEpatents

    Samani, Zohrab A.; Hanson, Adrian T.; Macias-Corral, Maritza

    2010-03-23

    An organic solid waste digester for producing methane from solid waste, the digester comprising a reactor vessel for holding solid waste, a sprinkler system for distributing water, bacteria, and nutrients over and through the solid waste, and a drainage system for capturing leachate that is then recirculated through the sprinkler system.

  12. Insights into Methane Formation Temperatures, Biogenic Methanogenesis, and Natural Methane Emissions from Clumped Isotopes

    NASA Astrophysics Data System (ADS)

    Douglas, P. M.; Stolper, D. A.; Walter Anthony, K. M.; Dallimore, S.; Paull, C. K.; Wik, M.; Crill, P. M.; Winterdahl, M.; Smith, D. A.; Luhmann, A. J.; Ding, K.; Seyfried, W. E., Jr.; Eiler, J. M.; Ponton, C.; Sessions, A. L.

    2015-12-01

    Multiply substituted isotopologues of methane are a valuable new tool for characterizing and understanding the source of methane in different Earth environments. Here we present methane clumped isotope results from natural gas wells, hydrothermal vents, marine and lacustrine methane seeps, and culture experiments. We observe a wide range of formation temperatures for thermogenic methane. Methane samples from low-maturity reservoirs indicate formation temperatures between 102-144° C, high-maturity conventional and shale gasses indicate temperatures between 158-246 °C, and thermogenic coal gases indicate temperatures between 174-267 °C. Methane formation temperatures generally correlate positively with δ13C, and negatively with gas wetness indices. Methane samples from a set of marine hydrothermal vents indicate a formation temperature of 290-350 °C. Methane sampled from subsurface and marine biogenic sources typically indicate temperatures consistent with the formation environment (0-64° C). In contrast, freshwater biogenic methane samples, and cultures of hydrogenotrophic and methylotrophic methanogens, express low levels of isotopic clumping inconsistent with their formation temperature. These data and complementary models suggest that kinetic isotope effects, likely modulated by rates and pathways of methanogenesis, affect biogenic methane in cultures and freshwater environments. Alternatively, non-equilibrium signatures may result from mixing of methane with widely differing δD and δ13C values. Analyses of biogenic methane emissions from lakes indicate a correlation between methane flux and non-equilibrium clumped isotope fractionations in a given lake. Results from large methane seeps in Alaskan lakes confirm that some seeps emit thermogenic methane, but also indicate that other seeps emit subsurface biogenic methane or variable mixtures of biogenic and thermogenic methane. These results point to diverse sources for large Arctic methane seeps.

  13. Understanding the Recent Methane Budget

    NASA Astrophysics Data System (ADS)

    Bruhwiler, L.; Dlugokencky, E. J.; Masarie, K.

    2010-12-01

    Anthropogenic sources are thought to account for roughly 2/3 of the global atmospheric methane budget, with natural sources making up the other 1/3. Emissions from wetlands are the largest contribution from natural sources while agriculture (rice and ruminants) and waste dominate anthropogenic emissions. Fugitive emissions from fossil fuel extraction are thought to make up about 20% of the global atmospheric methane budget. It is generally recognized that observed inter-annual variability in global network observations can be attributed to natural sources such as wetlands and biomass burning, while longer-term trends likely indicate changes in anthropogenic sources. Exceptions include an abrupt decrease in fossil fuel emissions in the early 1990s associated with political changes in the Former Soviet Union, and long-term trends in emissions from the Arctic due to a warming climate. The growth rate of global average atmospheric methane since the 1980s shows a steady decline until recent years when it started to increase again. Superimposed on these trends are episodes of higher growth rates. The cause of the recent increase is not currently well-understood, although climate-driven increases in wetland emissions likely played an important role, especially in the tropics. Recent increases in anthropogenic emissions, especially from rapidly expanding Asian economies cannot be ruled out. In addition, trends in the photochemical lifetime of methane must also be considered. In this paper we use both traditional data analysis of observations of methane and related species, and a state-of-the-art ensemble data assimilation system (CarbonTracker-CH4) to attribute methane variability and trends to anthropogenic and natural source processes. We pay particular attention to the Arctic, where some recent years have been the warmest on record, and to the tropics and the potential role of ENSO in driving variability of wetland emissions. Finally, we explore whether a signal in

  14. The regulation of methane oxidation in soil

    NASA Technical Reports Server (NTRS)

    Mancinelli, R. L.

    1995-01-01

    The atmospheric concentration of methane, a greenhouse gas, has more than doubled during the past 200 years. Consequently, identifying the factors influencing the flux of methane into the atmosphere is becoming increasingly important. Methanotrophs, microaerophilic organisms widespread in aerobic soils and sediments, oxidize methane to derive energy and carbon for biomass. In so doing, they play an important role in mitigating the flux of methane into the atmosphere. Several physico-chemical factors influence rates of methane oxidation in soil, including soil diffusivity; water potential; and levels of oxygen, methane, ammonium, nitrate, nitrite, and copper. Most of these factors exert their influence through interactions with methane monooxygenase (MMO), the enzyme that catalyzes the reaction converting methane to methanol, the first step in methane oxidation. Although biological factors such as competition and predation undoubtedly play a role in regulating the methanotroph population in soils, and thereby limit the amount of methane consumed by methanotrophs, the significance of these factors is unknown. Obtaining a better understanding of the ecology of methanotrophs will help elucidate the mechanisms that regulate soil methane oxidation.

  15. Geogenic methane emissions in central and eastern Romania

    NASA Astrophysics Data System (ADS)

    Baciu, Calin; Ionescu, Artur; Pop, Cristian; Etiope, Giuseppe

    2015-04-01

    Keywords: methane, greenhouse gases, geogenic emissions, Romania Relatively often, the hydrocarbon reservoirs are not completely sealed, thus permitting the channeling to the surface of various amounts of gas, mainly consisting of methane and homologues. When important volumes of gas are released, features as mud volcanoes and everlasting fires may occur. When the gas amount is low, the degassing can be revealed by instrumental means only. The gas seeps may be useful as indicators in the hydrocarbon exploration, but may be also hazardous when gas is accumulating in closed spaces. Additionally, the geogenic methane degassing represents an important contribution to the atmospheric budget of greenhouse gases. Romania is one of the European important hydrocarbon producers, with oil and gas deposits in different geologic and tectonic contexts. As well, the frequency of gas emitting features and seepage areas is high. Some relevant hydrocarbon-prone areas from Romania, namely the Neogene Transylvanian Basin, the Carpathian Foredeep, and the Moldavian Platform, are comparatively analysed within the current work from the point of view of methane emissions. The Carpathian Foredeep hosts the most impressive mud volcanoes and everlasting fires in Romania, classified among the biggest in Europe. The degassing area also extends in the Carpathian Flysch zone. The Transylvanian Basin hosts numerous gas-bearing structures, mainly of biogenic origin. With some exceptions, the methane-emitting features are small, releasing relatively low amounts of gas. A relatively high number of seeps have been described on the Moldavian Platform, although no commercial hydrocarbon reservoirs have been identified. The seeps are small, and they are releasing low amounts of methane. However, it is important to notice that the investigated zone partly corresponds to an area of interest for shale gas, related to the deep-seated Silurian shales. For all mentioned areas, the main geochemical

  16. Source apportionment of methane using a triple isotope approach - Method development and application in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Steinbach, Julia; Holmstrand, Henry; Semiletov, Igor; Shakhova, Natalia; Shcherbakova, Kseniia; Kosmach, Denis; Sapart, Célia J.; Gustafsson, Örjan

    2015-04-01

    We present a method for measurements of the stable and radiocarbon isotope systems of methane in seawater and sediments. The triple isotope characterization of methane is useful in distinguishing different sources and for improving our understanding of biogeochemical processes affecting methane in the water column. D14C-CH4 is an especially powerful addition to stable isotope analyses in distinguishing between thermogenic and biogenic origins of the methane. Such measurements require large sample sizes, due to low natural abundance of the radiocarbon in CH4. Our system for sample collection, methane extraction and purification builds on the approach by Kessler and Reeburgh (Limn. & Ocean. Meth., 2005). An in-field system extracts methane from 30 -120 l water or 1-2 l sediment (depending on the in-situ methane concentration) by purging the samples with Helium to transfer the dissolved methane to the headspace and circulating it through cryogenically cooled absorbent traps where methane is collected. The in-field preparation eliminates the risks of storage and transport of large seawater quantities and subsequent leakage of sample gas as well as ongoing microbial processes and chemical reactions that may alter the sample composition. In the subsequent shore-based treatment, a laboratory system is used to purify and combust the collected CH4 to AMS-amenable CO2. Subsamples from the methane traps are analyzed for stable isotopes and compared to stable isotope measurements directly measured from small water samples taken in parallel, to correct for any potential fractionation occurring during this process. The system has been successfully tested and used on several shorter shipboard expeditions in the Baltic Sea and on a long summer expedition across the Arctic Ocean. Here we present the details of the method and testing, as well as first triple isotope field data from two cruises to the Landsort Deep area in the Central Baltic Sea.

  17. Estimation of methane emission flux at landfill surface using laser methane detector: Influence of gauge pressure.

    PubMed

    Park, Jin-Kyu; Kang, Jong-Yun; Lee, Nam-Hoon

    2016-08-01

    The aim of this study was to investigate the possibility of measuring methane emission fluxes, using surface methane concentration and gauge pressure, by analyzing the influence of gauge pressure on the methane emission flux and the surface methane concentration, as well as the correlation between the methane emission flux and surface methane concentrations. The surface methane concentration was measured using a laser methane detector. Our results show a positive linear relationship between the surface methane concentration and the methane emission flux. Furthermore, the methane emission flux showed a positive linear relationship with the gauge pressure; this implies that when the surface methane concentration and the surface gauge pressure are measured simultaneously, the methane emission flux can be calculated using Darcy's law. A decrease in the vertical permeability was observed when the gauge pressure was increased, because reducing the vertical permeability may lead to a reduced landfill gas emission to the atmosphere, and landfill gas would be accumulated inside the landfill. Finally, this method is simple and can allow for a greater number of measurements during a relatively shorter period. Thus, it provides a better representation of the significant space and time variations in methane emission fluxes. PMID:27401161

  18. Estimation of methane emission flux at landfill surface using laser methane detector: Influence of gauge pressure.

    PubMed

    Park, Jin-Kyu; Kang, Jong-Yun; Lee, Nam-Hoon

    2016-08-01

    The aim of this study was to investigate the possibility of measuring methane emission fluxes, using surface methane concentration and gauge pressure, by analyzing the influence of gauge pressure on the methane emission flux and the surface methane concentration, as well as the correlation between the methane emission flux and surface methane concentrations. The surface methane concentration was measured using a laser methane detector. Our results show a positive linear relationship between the surface methane concentration and the methane emission flux. Furthermore, the methane emission flux showed a positive linear relationship with the gauge pressure; this implies that when the surface methane concentration and the surface gauge pressure are measured simultaneously, the methane emission flux can be calculated using Darcy's law. A decrease in the vertical permeability was observed when the gauge pressure was increased, because reducing the vertical permeability may lead to a reduced landfill gas emission to the atmosphere, and landfill gas would be accumulated inside the landfill. Finally, this method is simple and can allow for a greater number of measurements during a relatively shorter period. Thus, it provides a better representation of the significant space and time variations in methane emission fluxes.

  19. Methane clathrates in the solar system.

    PubMed

    Mousis, Olivier; Chassefière, Eric; Holm, Nils G; Bouquet, Alexis; Waite, Jack Hunter; Geppert, Wolf Dietrich; Picaud, Sylvain; Aikawa, Yuri; Ali-Dib, Mohamad; Charlou, Jean-Luc; Rousselot, Philippe

    2015-04-01

    We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate

  20. Methane clathrates in the solar system.

    PubMed

    Mousis, Olivier; Chassefière, Eric; Holm, Nils G; Bouquet, Alexis; Waite, Jack Hunter; Geppert, Wolf Dietrich; Picaud, Sylvain; Aikawa, Yuri; Ali-Dib, Mohamad; Charlou, Jean-Luc; Rousselot, Philippe

    2015-04-01

    We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate

  1. Short-range, overpressure-driven methane migration in coarse-grained gas hydrate reservoirs

    NASA Astrophysics Data System (ADS)

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; Malinverno, Alberto

    2016-09-01

    Two methane migration mechanisms have been proposed for coarse-grained gas hydrate reservoirs: short-range diffusive gas migration and long-range advective fluid transport from depth. Herein, we demonstrate that short-range fluid flow due to overpressure in marine sediments is a significant additional methane transport mechanism that allows hydrate to precipitate in large quantities in thick, coarse-grained hydrate reservoirs. Two-dimensional simulations demonstrate that this migration mechanism, short-range advective transport, can supply significant amounts of dissolved gas and is unencumbered by limitations of the other two end-member mechanisms. Short-range advective migration can increase the amount of methane delivered to sands as compared to the slow process of diffusion, yet it is not necessarily limited by effective porosity reduction as is typical of updip advection from a deep source.

  2. Short-range, overpressure-driven methane migration in coarse-grained gas hydrate reservoirs

    DOE PAGES

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; Malinverno, Alberto

    2016-08-31

    Two methane migration mechanisms have been proposed for coarse-grained gas hydrate reservoirs: short-range diffusive gas migration and long-range advective fluid transport from depth. Herein we demonstrate that short-range fluid flow due to overpressure in marine sediments is a significant additional methane transport mechanism that allows hydrate to precipitate in large quantities in thick, coarse-grained hydrate reservoirs. Two-dimensional simulations demonstrate that this migration mechanism, short-range advective transport, can supply significant amounts of dissolved gas and is unencumbered by limitations of the other two end-member mechanisms. Here, short-range advective migration can increase the amount of methane delivered to sands as compared tomore » the slow process of diffusion, yet it is not necessarily limited by effective porosity reduction as is typical of updip advection from a deep source.« less

  3. NATURAL GAS RESOURCES IN DEEP SEDIMENTARY BASINS

    SciTech Connect

    Thaddeus S. Dyman; Troy Cook; Robert A. Crovelli; Allison A. Henry; Timothy C. Hester; Ronald C. Johnson; Michael D. Lewan; Vito F. Nuccio; James W. Schmoker; Dennis B. Riggin; Christopher J. Schenk

    2002-02-05

    From a geological perspective, deep natural gas resources are generally defined as resources occurring in reservoirs at or below 15,000 feet, whereas ultra-deep gas occurs below 25,000 feet. From an operational point of view, ''deep'' is often thought of in a relative sense based on the geologic and engineering knowledge of gas (and oil) resources in a particular area. Deep gas can be found in either conventionally-trapped or unconventional basin-center accumulations that are essentially large single fields having spatial dimensions often exceeding those of conventional fields. Exploration for deep conventional and unconventional basin-center natural gas resources deserves special attention because these resources are widespread and occur in diverse geologic environments. In 1995, the U.S. Geological Survey estimated that 939 TCF of technically recoverable natural gas remained to be discovered or was part of reserve appreciation from known fields in the onshore areas and State waters of the United. Of this USGS resource, nearly 114 trillion cubic feet (Tcf) of technically-recoverable gas remains to be discovered from deep sedimentary basins. Worldwide estimates of deep gas are also high. The U.S. Geological Survey World Petroleum Assessment 2000 Project recently estimated a world mean undiscovered conventional gas resource outside the U.S. of 844 Tcf below 4.5 km (about 15,000 feet). Less is known about the origins of deep gas than about the origins of gas at shallower depths because fewer wells have been drilled into the deeper portions of many basins. Some of the many factors contributing to the origin of deep gas include the thermal stability of methane, the role of water and non-hydrocarbon gases in natural gas generation, porosity loss with increasing thermal maturity, the kinetics of deep gas generation, thermal cracking of oil to gas, and source rock potential based on thermal maturity and kerogen type. Recent experimental simulations using laboratory

  4. Geological & Geophysical findings from seismic, well log and core data for marine gas hydrate deposits at the 1st offshore methane hydrate production test site in the eastern Nankai Trough, offshore Japan: An overview

    NASA Astrophysics Data System (ADS)

    Fujii, T.; Noguchi, S.; Takayama, T.; Suzuki, K.; Yamamoto, K.

    2012-12-01

    In order to evaluate productivity of gas from marine gas hydrate by the depressurization method, Japan Oil, Gas and Metals National Corporation is planning to conduct a full-scale production test in early 2013 at the AT1 site in the north slope of Daini-Atsumi Knoll in the eastern Nankai Trough, Japan. The test location was determined using the combination of detailed 3D seismic reflection pattern analysis, high-density velocity analysis, and P-impedance inversion analysis, which were calibrated using well log data obtained in 2004. At the AT1 site, one production well (AT1-P) and two monitoring wells (AT1-MC and MT1) were drilled from February to March 2012, followed by 1 coring well (AT1-C) from June to July 2012. An extensive logging program with logging while drilling (LWD) and wireline-logging tools, such as GeoVISION (resistivity image), EcoScope (neutron/density porosity, mineral spectroscopy etc.), SonicScanner (Advanced Sonic tool), CMR/ProVISION (Nuclear Magnetic Resonance Tools), XPT (formation pressure, fluid mobility), and IsolationScanner (ultrasonic cement evaluation tools) was conducted at AT1-MC well to evaluate physical reservoir properties of gas hydrate-bearing sediments, to determine production test interval in 2013, and to evaluate cement bonding. Methane hydrate concentrated zone (MHCZ) confirmed by the well logging at AT1-MC was thin turbidites (tens of centimeters to few meters) with 60 m of gross thickness, which is composed of lobe type sequences in the upper part of it and channel sand sequences in the lower part. The gross thickness of MHCZ in the well is thicker than previous wells in 2004 (A1, 45 m) located around 150 m northeast, indicating that the prediction given by seismic inversion analysis was reasonable. Well-to-well correlation between AT1-MC and MT1 wells within 40 m distance exhibited that lateral continuity of these sand layers (upper part of reservoir) are fairly good, which representing ideal reservoir for the production

  5. Turbulent burning rates of methane and methane-hydrogen mixtures

    SciTech Connect

    Fairweather, M.; Ormsby, M.P.; Sheppard, C.G.W.; Woolley, R.

    2009-04-15

    Methane and methane-hydrogen (10%, 20% and 50% hydrogen by volume) mixtures have been ignited in a fan stirred bomb in turbulence and filmed using high speed cine schlieren imaging. Measurements were performed at 0.1 MPa (absolute) and 360 K. A turbulent burning velocity was determined for a range of turbulence velocities and equivalence ratios. Experimental laminar burning velocities and Markstein numbers were also derived. For all fuels the turbulent burning velocity increased with turbulence velocity. The addition of hydrogen generally resulted in increased turbulent and laminar burning velocity and decreased Markstein number. Those flames that were less sensitive to stretch (lower Markstein number) burned faster under turbulent conditions, especially as the turbulence levels were increased, compared to stretch-sensitive (high Markstein number) flames. (author)

  6. Bedrock, Borehole, and Water-Quality Characterization of a Methane-Producing Water Well in Wolfeboro, New Hampshire

    USGS Publications Warehouse

    Degnan, James R.; Walsh, Gregory J.; Flanagan, Sarah; Burruss, Robert A.

    2008-01-01

    In August 2004, a commercial drill rig was destroyed by ignition of an explosive gas released during the drilling of a domestic well in granitic bedrock in Tyngsborough, MA. This accident prompted the Massachusetts Department of Environmental Protection (MassDEP) to sample the well water for dissolved methane - a possible explosive fuel. Water samples collected from the Tyngsborough domestic well in 2004 by the MassDEP contained low levels of methane gas (Pierce and others, 2007). When the U.S. Geological Survey (USGS) sampled this well in 2006, there was no measurable amount of methane remaining in the well water (Pierce and others, 2007). Other deep water wells in nearby south-central New Hampshire have been determined to have high concentrations of naturally occurring methane (David Wunsch, New Hampshire State Geologist, 2004, written commun.). Studying additional wells in New England crystalline bedrock aquifers that produce methane may help to understand the origin of methane in crystalline bedrock. Domestic well NH-WRW-37 was chosen for this study because it is a relatively deep well completed in crystalline bedrock, it is not affected by known anthropogenic sources of methane, and it had the highest known natural methane concentration (15.5 mg/L, U.S. Geological Survey, 2007) measured in a study described by Robinson and others (2004). This well has been in use since it was drilled in 1997, and it was originally selected for study in 2000 as part of a 30 well network, major-aquifer study by the USGS' New England Coastal Basins (NECB) study unit of the National Water-Quality Assessment (NAWQA) Program. Dissolved methane in drinking water is not considered an ingestion health hazard, although the occurrence in ground water is a concern because, as a gas, its buildup in confined spaces can cause asphyxiation, fire, or explosion hazards (Mathes and White, 2006). Methane occurrence in the fractured crystalline bedrock is not widely reported or well understood

  7. Preventing Deep Vein Thrombosis

    MedlinePlus

    ... Patient Education FAQs Preventing Deep Vein Thrombosis Patient Education Pamphlets - Spanish Preventing Deep Vein Thrombosis FAQ174, August 2011 PDF ... Your Practice Patient Safety & Quality Payment Reform (MACRA) Education & Events Annual ... Pamphlets Teen Health About ACOG About Us Leadership & ...

  8. Taoism and Deep Ecology.

    ERIC Educational Resources Information Center

    Sylvan, Richard; Bennett, David

    1988-01-01

    Contrasted are the philosophies of Deep Ecology and ancient Chinese. Discusses the cosmology, morality, lifestyle, views of power, politics, and environmental philosophies of each. Concludes that Deep Ecology could gain much from Taoism. (CW)

  9. Methane-related changes in prokaryotes along geochemical profiles in sediments of Lake Kinneret (Israel)

    NASA Astrophysics Data System (ADS)

    Bar-Or, I.; Ben-Dov, E.; Kushmaro, A.; Eckert, W.; Sivan, O.

    2015-05-01

    Microbial methane oxidation is the primary control on the emission of the greenhouse gas methane into the atmosphere. In terrestrial environments, aerobic methanotrophic bacteria are largely responsible for this process. In marine sediments, a coupling of anaerobic oxidation of methane (AOM) with sulfate reduction, often carried out by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria, consumes almost all methane produced within those sediments. Motivated by recent evidence for AOM with iron(III) in Lake Kinneret sediments, the goal of the present study was to link the geochemical gradients in the lake porewater to the microbial community structure. Screening of archaeal 16S rRNA gene sequences revealed a shift from hydrogenotrophic to acetoclastic methanogens with depth. The observed changes in microbial community structure suggest possible direct and indirect mechanisms for the AOM coupled to iron reduction in deep sediments. The percentage of members of the Nitrospirales order increased with depth, suggesting their involvement in iron reduction together with Geobacter genus and "reverse methanogenesis". An indirect mechanism through sulfate and ANME seems less probable due to the absence of ANME sequences. This is despite the abundant sequences related to sulfate-reducing bacteria (Deltaproteobacteria) together with the occurrence of dsrA in the deep sediment that could indicate the production of sulfate (disproportionation) from S0 for sulfate-driven AOM. The presence of the functional gene pmoA in the deep anoxic sediment together with sequences related to Methylococcales suggests the existence of a second unexpected indirect pathway - aerobic methane oxidation pathway in an anaerobic environment.

  10. The Methane to Markets Coal Mine Methane Subcommittee meeting

    SciTech Connect

    2008-07-01

    The presentations (overheads/viewgraphs) include: a report from the Administrative Support Group; strategy updates from Australia, India, Italy, Mexico, Nigeria, Poland and the USA; coal mine methane update and IEA's strategy and activities; the power of VAM - technology application update; the emissions trading market; the voluntary emissions reduction market - creating profitable CMM projects in the USA; an Italian perspective towards a zero emission strategies; and the wrap-up and summary.

  11. Effects of Salinity and Sea Level Change on Permafrost-Hosted Methane Hydrate Reservoirs

    NASA Astrophysics Data System (ADS)

    Elwood-Madden, M.

    2010-12-01

    Recent observations of methane release from sediments on the circum-arctic continental shelf indicate that arctic warming is likely leading to increased fluxes of methane . Thermodynamics predicts that 2-4 degree increases in global temperature will lead to massive marine hydrate decomposition; however, the rate of warming deep ocean waters and sediments is fairly slow, resulting in modest fluxes of methane over hundreds to thousands of years. In contrast, increasing arctic temperatures and rising sea level may have immediate effects on permafrost-hosted hydrate deposits. Rising sea level affects both the geothermal gradient of the region and the salinity of pore waters, leading to hydrate destabilization (Figure 1). Seawater infiltration of permafrost may be currently dissociating permafrost-hosted methane hydrate through a combination of mechanisms: shifting geothermal gradients to higher temperatures, addition of salts due to seawater encroachment, and the transition from solid state diffusion of methane through overlying ice cemented permafrost to mass transfer through seawater-saturated sediments via aqueous diffusion, advection, or ebullition. Effects of seawater erosion of permafrost have been observed in arctic coastal areas, and degradation of arctic permafrost is predicted to continue, especially in coastal areas. However, the rate at which these processes proceed and their effects on permafrost-hosted methane hydrates have been largely uninvestigated. Changes in geothermal gradient alone take hundreds to thousands of years to affect relatively deep hydrate reservoirs. However, warmer temperatures combined with freezing point depression effects of seawater may lead to rapid melting of permafrost ice, thus accelerating the transfer of heat to the hydrate reservoirs and changing the mass transfer mechanism of methane release from slow solid state diffusion through ice to more rapid aqueous diffusion, advection, or ebullition. Therefore, we hypothesize that

  12. Attributing Atmospheric Methane to Anthropogenic Emission Sources.

    PubMed

    Allen, David

    2016-07-19

    Methane is a greenhouse gas, and increases in atmospheric methane concentration over the past 250 years have driven increased radiative forcing of the atmosphere. Increases in atmospheric methane concentration since 1750 account for approximately 17% of increases in radiative forcing of the atmosphere, and that percentage increases by approximately a factor of 2 if the effects of the greenhouse gases produced by the atmospheric reactions of methane are included in the assessment. Because of the role of methane emissions in radiative forcing of the atmosphere, the identification and quantification of sources of methane emissions is receiving increased scientific attention. Methane emission sources include biogenic, geogenic, and anthropogenic sources; the largest anthropogenic sources are natural gas and petroleum systems, enteric fermentation (livestock), landfills, coal mining, and manure management. While these source categories are well-known, there is significant uncertainty in the relative magnitudes of methane emissions from the various source categories. Further, the overall magnitude of methane emissions from all anthropogenic sources is actively debated, with estimates based on source sampling extrapolated to regional or national scale ("bottom-up analyses") differing from estimates that infer emissions based on ambient data ("top-down analyses") by 50% or more. To address the important problem of attribution of methane to specific sources, a variety of new analytical methods are being employed, including high time resolution and highly sensitive measurements of methane, methane isotopes, and other chemical species frequently associated with methane emissions, such as ethane. This Account describes the use of some of these emerging measurements, in both top-down and bottom-up methane emission studies. In addition, this Account describes how data from these new analytical methods can be used in conjunction with chemical mass balance (CMB) methods for source

  13. Attributing Atmospheric Methane to Anthropogenic Emission Sources.

    PubMed

    Allen, David

    2016-07-19

    Methane is a greenhouse gas, and increases in atmospheric methane concentration over the past 250 years have driven increased radiative forcing of the atmosphere. Increases in atmospheric methane concentration since 1750 account for approximately 17% of increases in radiative forcing of the atmosphere, and that percentage increases by approximately a factor of 2 if the effects of the greenhouse gases produced by the atmospheric reactions of methane are included in the assessment. Because of the role of methane emissions in radiative forcing of the atmosphere, the identification and quantification of sources of methane emissions is receiving increased scientific attention. Methane emission sources include biogenic, geogenic, and anthropogenic sources; the largest anthropogenic sources are natural gas and petroleum systems, enteric fermentation (livestock), landfills, coal mining, and manure management. While these source categories are well-known, there is significant uncertainty in the relative magnitudes of methane emissions from the various source categories. Further, the overall magnitude of methane emissions from all anthropogenic sources is actively debated, with estimates based on source sampling extrapolated to regional or national scale ("bottom-up analyses") differing from estimates that infer emissions based on ambient data ("top-down analyses") by 50% or more. To address the important problem of attribution of methane to specific sources, a variety of new analytical methods are being employed, including high time resolution and highly sensitive measurements of methane, methane isotopes, and other ch