geological controls on gas saturation in the yanchuannan coalbed methane field southeastern ordos basin china abstract the paper investigates lateral variation of gas saturation and its geological controls of the no 2 coal seam in the permian shanxi formation based on coal samples from 21 exploration wells in the yanchuannan coalbed methane cbm field southeastern ordos basin china the data set reveals that gas saturation of the no 2 coal seam shows a high lateral variation from 32 44 to 89 69 and that there is an overall trend in gas saturation with depth overprinted by four other factors 1 influence of faults 2 secondary biogenic gas generation 3 local top seal conditions and 4 variations in coal properties the reverse faults f1 and f2 are effective barriers horizontally for the hydraulic communication and divide our study area into relatively closed and recharge zones gas saturation of the relatively closed zone is generally higher than that in the recharge zone in the recharge gas saturation increases generally along the flow pathway of groundwater with the exceptions of the areas affected by secondary biogenic gas the stable isotope compositions suggest that late stage biogenic methane was generated via co 2 reduction associated with meteoric water recharge which significantly contributes to higher gas saturation than expected meanwhile the biogenic gas generation was is restricted to shallow depths the apparent variations in local areas of lithology of the overlying stratum next to the coal seam suggest that the top seal conditions are deteriorative which can cause gas dissipation and reduce gas saturation remarkably integrally for the variations in coal properties gas saturation has a general positive relationship with coalification and weak negative correlations with moisture content and ash yield but the relationships lacks statistical significances gas saturation is not associated with coal maceral in the study area

preliminary research on cbm enrichment models of low rank coal and its geological controls a case study in the middle of the southern junggar basin nw china abstract to date prospecting work on low rank coalbed methane cbm resources in the middle of the southern junggar basin is still in the primary stage and only a few cbm exploration wells or pilot wells have been deployed in local regions systemic understanding of cbm reservoir forming conditions and geological controlling factors is lacking in the study area resulting in the mismatch between cbm well deployment and actual geological conditions as well as poor exploration efficiency in this paper the geological controlling effects of the structure sedimentation and hydrogeology on cbm enrichment are systematically discussed for the first time based on the early cbm exploration achievements the results show that the xishanyao coal and the badaowan coal are developed in the upper and lower part of the neutral surface of a fold respectively the reservoir forming conditions of the badaowan coal are not discussed in this paper due to its poor development the xishanyao coal that developed in the axial part of the syncline is most beneficial to cbm enrichment with concentrated extrusion stress and great methane adsorption capacity while the axial part of the anticline is not favorable for cbm preservation with large tensional stress the gas content of the xishanyao thick seams developed in the syncline is higher average of 4 63 6 34 m3 t than that in the monocline average of 2 84 4 56 m3 t reverse faulting is more beneficial to cbm enrichment than normal faulting due to the better sealing capability the gas content of the xishanyao coal is obviously influenced by the coal thickness and its roof lithology the hydrodynamic conditions and total dissolved solids tds values of coalbed water range greatly on regional scale which leads to a deeper methane weathering zone in the middle west areas 1119 62 m than the eastern liu huanggou areas

geological interpretation of gas content trends walloon subgroup eastern surat basin queensland australia abstract the middle jurassic walloon subgroup is a prolific low rank coal seam gas csg resource in the surat basin australia this study applied a regionally consistent stratigraphic framework model to open file gas desorption and coal property data from 69 cored csg wells to assess spatial trends in gas content and test the influence of large scale geological heterogeneity on present day gas distribution continued successful exploration and production and possible future microbial regeneration of the walloon csg resource require an improved understanding of the controls on gas content distribution across the core region of production in the eastern surat basin the walloon subgroup can be subdivided into upper juandah and lower taroom coal measures separated by a relatively coal barren and sandstone dominated unit tangalooma sandstone within these units lateral variation in coal character is high precluding a regionally agreed coal group or seam correlation while the total dataset shows a general increase in gas content dry ash free d a f with increasing depth as a function of hydrostatic pressure there is considerable scatter in the distribution within individual wells gas content follows one of three trends gas content either 1 increases 2 increases then decreases or 3 decreases with depth trend 2 parabolic wells predominate with the gas content maxima coinciding with the tangalooma sandstone regardless of depth as such gas content layering follows rather than cross cuts the stratigraphy in the majority of wells the change in gas content with depth between the different units and the wells was used to identify domains of different gas gradients which could relate to differing gas saturations and geological setting the well profiles and gas gradients were analysed against available open file coal quality data without strong correlation to rank or type parameters the majority of very high gas gradient values occur in coals within or above the tangalooma sandstone suggesting that it forms a regional scale barrier both to possible gas migration from underlying and higher rank coals and to meteoric and biogenic recharge from above increased ethane values in the upper taroom and tangalooma csg support this interpretation alternatively this distribution may be the result of alternating adsorption desorption cycles linked to burial and uplift the wells containing the highest mean gas gradients span a range of subtle rank and structural domains but generally occur in structural highs under topographic lows with hydrostatic head wells from smaller scale anticlines not associated with topographic surface lows mainly exhibit lower mean gas gradients the study significantly expands the number of published gas content trends and proposes several factors influencing their formation and geographical distribution the results form the basis for future targeted sampling to test for gas origins migration retention and biogenic recharge processes within the surat basin

use of temperature logs in coal seam gas reservoirs application to the sydney basin australia this study examines the relationship between borehole temperature logs and gas distribution in coal seams both spatially and with depth temperature logs are often utilized in hydrogeology to monitor groundwater flow which can introduce methanogenic consortia into coal seams resulting in the generation and accumulation of coal seam gases areas of hydraulic connectivity characterized by open cleats and fractures provide a pathway for the meteoric influx whereas tight mineralized sections of strata prohibit vertical flow and have the potential to trap coal seam gases or to limit the influx of methanogens and the generation of secondary biogenic methane the combination of these concepts raises the possibility of utilizing temperature logs for mapping coal seam gas distributions and assisting exploration activities wireline temperature logs are inexpensive to obtain as part of any exploration production or monitoring program but provide information pertaining to flow regimes and in situ geological environments a case study is presented from the sydney basin of australia to demonstrate the types of analyses and interpretations relating to coal seam gas distribution that may be gleaned from temperature log datasets

geological and hydrogeological controls on the accumulation of coalbed methane in the weibei field southeastern ordos basin abstract commercial exploration and production of coalbed methane cbm in the weibei field ordos basin china has rapidly increased since 2010 the weibei field has become one of the most productive cbm areas in china however relatively few studies have investigated the migration of gas and water in the coal reservoir and their controls on the gas accumulation this study conducts stable isotope analyses and quality tests for groundwater samples discusses the relationships between the fluid flow pathways and tectonics and concludes by discussing the geological and hydrological controls on potential gas accumulation in the weibei field the coalbed groundwaters contain primarily sodium and bicarbonate and are effectively devoid of sulfate calcium and magnesium the groundwaters are typically freshwater with total dissolved solids tds values ranging from 814 to 2657 mg l differences in hydrogeology and structural geology divide the study area into four gas domains in the northern hancheng area the predominant northwest flow of groundwater has resulted in higher gas content in the west 12 m 3 t than in the east 8 12 m 3 t even though the coals in the east have high thermal maturity 2 1 2 3 r o the area with the highest gas content 16 m 3 t is in the region near the downthrown side of the xuefeng nan thrust fault in the northern hancheng area and the fault forms a barrier to the northwestward flow of groundwater the area with the lowest gas content 3 t is in the southwest heyang area where there is no entrapment mechanism and the gas has been flushed out of the coals due to a reduction of hydrostatic pressure and active groundwater flow from the east structural and hydrodynamic mechanisms especially the intensity of the hydrodynamic activity and the groundwater flow pathways are important for gas accumulation in the weibei field

factors controlling high yield coalbed methane vertical wells in the fanzhuang block southern qinshui basin abstract whether a coalbed methane cbm well achieves high yield is controlled by various factors structural and hydrological control models of cbm productivity in vertical wells were built using a combined investigation of basic tectonic settings and hydrological conditions as well as drainage parameters of the coal reservoir in the fanzhuang block southern qinshui basin this study indicates that gas water production differs significantly among wells with different structural settings or hydrogeological conditions low and unstable gas production rates in individual wells are the primary problem for the cbm development in the fanzhuang block the impacts of some geologic and engineering factors on gas production were analyzed and estimated based on comparative analysis quantitative analysis and gray system theory the results indicate that the critical reservoir ratio crr liquid column height lch and gas content are the most important factors in determining well productivity followed by the equivalent drainage radius edr the volume of frac sand and the decline rate of working fluid levels during initial production high yield wells in the fanzhuang block always have the following conditions gas content 20 m 3 t burial depth of 500 700 m crr 0 7 lch 400 m volume of frac sand 40 m 3 edr of 30 60 m and a decline rate of working fluid level lower than 2 m day during the initial production stage

inducing fractures and increasing cleat apertures in a bituminous coal under isotropic stress via application of microwave energy abstract for the degassing of coal seams either prior to mining or in un minable seams to obtain coalbed methane it is the combination of cleat frequency aperture connectivity stress and mineral occlusions that control permeability unfortunately many potential coalbeds have limited permeability and are thus marginal for economic methane extraction enhanced coalbed methane production with concurrent co 2 sequestration is also challenging due to limited co 2 injectivity microwave energy can in the absence of confining stress induce fractures in coal here creation of new fractures and increasing existing cleat apertures via short burst high energy microwave energy was evaluated for an isotropically stressed and an unstressed bituminous coal core a microwave transparent argon gas pressurized 1000 psi polycarbonate vessel was constructed to apply isotropic stress simulating 1800 foot depth cleat frequency and distribution was determined for the two cores via micro focused x ray computed tomography evaluation occurred before and after microwave exposure with and without the application of isotropic stress during exposure optical microscopy was performed for tomography cleat aperture calibration and also to examine lithotypes influences on fracture initiation propagation frequency and orientation it was confirmed that new fractures are induced via high energy microwave exposure in an unconfined bituminous core and that the aperture increased in existing cleats cleat fracture volume following microwave exposure increased from 1 8 to 16 1 of the unconfined core volume for the first time similar observations of fracture generation and aperture enhancement in coal were also determined for microwave exposure under isotropic stress conditions an existing cleat aperture determined from calibrated x ray computed tomography increased from 0 17 mm to 0 32 mm the cleat fracture volume increased from 0 5 to 5 5 optical microscopy indicated that fracture initiated likely occurred in at least some cases at fusain microlithotypes presumably this was due to the open pore volumes and potential for bulk water presence or steam pressure buildup in these locations for the major induced fractures they were mostly horizontal parallel to the bedding plane and often contained within lithotype bands thus it appears likely that microwaves have the potential to enhance the communication between horizontal wellbore and existing cleat network in coal seams at depth for improved gas recovery or co 2 injection

geological and hydrological controls on water coproduced with coalbed methane in liulin eastern ordos basin china significant amounts of water are currently being extracted from coalbed methane cbm wells in permian carboniferous coal in the liulin area of the eastern ordos basin china waters coproduced with cbm have common chemical characteristics that can be an important exploration tool because they relate to the coal depositional environment and hydrodynamic maturation of groundwater and can be used to guide cbm development strategies the cbm production targets of the no 3 and 4 coal seams from sandstone in the shanxi formation and no 8 9 and 10 coal seams in the karst of the taiyuan formation were deposited in fluvial deltaic and epicontinental sea environments respectively this paper combines cbm geology hydrogeology cbm recovery and laboratory data to define mechanisms of cbm preservation including the important influence of groundwater relevant indices include fluid inclusions as an indicator of the hydraulic connection between the coal seam reservoir and the overlaying strata and the ensemble characteristics of total dissolved solids tds contents of water water production rates and reservoir temperatures as an indication of the current hydraulic connection the tds contents of waters from the no 3 and 4 and no 9 and 10 coal seams are double those from the subjacent karst no 8 coal seam indicating the important control of fast flow in karst low salinity fluid inclusions from the roof of the subjacent karst no 8 coal seam also indicate an enduring hydraulic connection with overlaying strata during its burial history relatively low current temperatures in the no 8 subjacent karst coal seam also infer a strong hydraulic connection and active flow regime deuterium concentrations are elevated in the mudstone bounded no 9 and 10 coal seams further confirming low rates of fluid transmission the gas contents of coal seams from the taiyuan formation are higher than those from the sandstone bounded coal seams in shanxi formation also correlating with low rates of water transmission and low permeability conceptual models for these fluvial deltaic and epicontinental sea environments that are consistent with geology gas content and gas and water production rate histories are of gas pressure sealing for the shanxi formation and hydrostatic pressure sealing for the taiyuan formation these results confirm the important controls of hydrogeological conditions on the preservation of cbm and the utility of hydrogeological indicators in prospecting for cbm

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

cross formational flow of water into coalbed methane reservoirs controls on relative permeability curve shape and production profile coalbed methane cbm wells tend to produce large volumes of water especially when there is hydraulic connectivity between coalbed and nearby formations cross formational flow between producing coal and adjacent formations can have significant production and environmental implications affecting economic viability of production from these shallow reservoirs such flows can also affect how much gas can be removed from a coalbed prior to mining and thus can have implications for methane control in mining as well the aim of this paper is to investigate the impact of water flow from an external source into coalbed on production performance and also on reservoir variables including cleat porosity and relative permeability curves derived from production data analysis a reservoir model is constructed to investigate the production performance of a cbm well when cross formational flow is present between the coalbed and the overlying formation results show that cleat porosity calculated by analysis of production data can be more than one order of magnitude higher than actual cleat porosity due to hydraulic connectivity water saturation within coalbed does not considerably change for a period of time and hence the peak of gas production is delayed upon depletion of the overlying formation water saturation in coalbed quickly decreases rapid decline of water saturation in the coalbed corresponds to a sharp increase in gas production as an important consequence when cross flow is present gas and water relative permeability curves derived from simulated production data have distinctive features compared to the initial relative permeability curves in the case of cross flow signatures of relative permeability curves are concave downward and low gas permeability for a range of water saturation followed by rapid increase afterward for water and gas respectively the results and analyses presented in this work can help to assess the impact of cross formational flow on reservoir variables derived from production data analysis and can also contribute to identifying hydraulic connectivity between coalbed and adjacent formations

secondary biogenic coal seam gas reservoirs in new zealand a preliminary assessment of gas contents abstract four coal cores one from the huntly eocene two from the ohai cretaceous and one from the greymouth cretaceous coalfields were sampled and analysed in terms of gas content and coal properties the coals vary in rank from subbituminous b a huntly to subbituminous c a ohai and high volatile a bituminous greymouth average gas contents were 1 60 m 3 t s 0 2 in the huntly core 4 80 m 3 t s 0 8 in the ohai cores and 2 39 m 3 t s 0 8 in the greymouth core the ohai core not only contained more gas but also had the highest saturation 75 compared with the huntly 33 and greymouth 45 cores carbon isotopes indicate that the ohai gas is more mature containing higher 13 c isotopes values than either the huntly or greymouth gas samples this may indicate that the gas was derived from a mixed biogenic and thermogenic source the huntly and greymouth gases appear to be derived solely from a secondary biogenic by co 2 reduction source although the data set is limited preliminary analysis indicates that ash yield is the dominant control on gas volume in all samples where the ash yield was above 10 below 10 the amount of gas variation is unrelated to ash yield although organic content has some influence on gas volume associations are basin and or rank dependent in the huntly core total gas content and structured vitrinite increase together although this relationship does not appear for the other core data for the ohai sc3 core lost gas and fusinite are associated whereas gelovitrinite unstructured vitrinite correlates positively with residual gas for the greymouth data

anatomy of an intruded coal ii effect of contact metamorphism on organic δ13c and implications for the release of thermogenic methane springfield no 5 coal illinois basin abstract concerns about the present day accelerated rate of carbon input to the atmosphere have prompted the search for comparable events throughout earth s history recent research has attempted to determine the cause of such events represented as negative 13 c excursions within the sedimentary record and their subsequent effect on the earth it has been suggested that such excursions could be the result of the large scale release of 13 c depleted thermogenic methane produced by the intrusion of large igneous provinces lips into organic rich rocks and or coal e g mcelwain et al 2005 svensen et al 2004 2007 our study asserts that if intrusions result in significant release of 13 c depleted thermogenic methane from intruded coals 13 c enriched coal should be observed adjacent to the intrusions in this study values of bulk organic 13 c 13 c org are reported for fifteen samples along a coal transect in the illinois basin where a pennsylvanian age coal the springfield or no 5 coal is intruded by a permian ultramafic dike the samples reveal significant bulk geochemical and petrographic changes within the alteration halo for example volatile matter vm decreases towards the intrusion whereas fixed carbon fc and vitrinite reflectance r r both increase accompanied by the development of natural coke both isotropic and anisotropic mosaic structure devolatilization vacuoles and carbonate mineralization reflectance levels and coke development are consistent with exposure to temperatures 450 500 c despite the high level of alteration of the organic matter no significant change is observed in 13 c org values across the transect vary by less than 0 5 along this transect 13 c org does not correlate with r r and does not appear to be influenced by maceral composition the intruded coals show no evidence of pyrolytic carbon that could influence 13 c org the relatively high vm contents of the intruded coals compared to coals that have undergone normal burial maturation and the lack of any trend in 13 c org approaching the intrusion raises questions about previously published models of the effects of large scale igneous intrusions on atmospheric composition and 13 c org excursions associated with oceanic anoxic events this study underscores the importance of the use of organic petrography in combination with isotope geochemistry to determine if contact metamorphosed coals and organic rich shales could have released a significant amount of 13 c org depleted volatiles leading to negative 13 c org excursions in the sedimentary record

no evidence for thermogenic methane release in coal from the karoo ferrar large igneous province abstract the early jurassic toarcian oceanic anoxic event t oae and concurrent negative carbon isotope 13 c excursion have recently been attributed to either the release of methane ch 4 clathrates or thermogenic ch 4 gas associated with the karoo ferrar large igneous province lip into coals and organic rich shales 12 c enriched thermogenic ch 4 production associated with the karoo ferrar would result in residual material being 12 c depleted nearer the intrusions in this study geochemical analyses carbon isotopes volatile matter vm vitrinite reflectance r o are reported for two coal transects associated with dykes intruding the no 4l coal in the highveld coalfield karoo basin south africa vm decreases from over 35 to around 15 in one transect and the second transect shows a less pronounced decrease from 25 to 16 accompanying the decrease in vm content is an increase in r o from background levels of around 0 7 to over 4 adjacent to the dyke used as a palaeo geothermometer r o values indicate background temperatures of 100 c increasing to 300 c close to the contact despite changes in vm and r o there are no significant changes in 13 c certainly not of the magnitude that would be expected associated with large scale thermogenic ch 4 generation these and other gondwanan coals have low vitrinite and liptinite contents components more prone to ch 4 generation in part explaining the modest decreases in vm adjacent to the dykes this combined with the relatively narrow metamorphic aureole surrounding the intrusions and the likelihood that at least some of the volatiles generated by the intrusion were trapped as coalbed ch 4 or condensed as pyrolytic carbon suggests only limited ch 4 release in addition based on original estimates of moisture contents in these coals and the depth at time of intrusion 1 000 2 000 m the dykes would have lost most of their energy heating and evaporating water thus having very little remaining energy to generate thermogenic ch 4

discussion on the concepts in paleoenvironmental reconstruction from coal macerals and petrographic indices abstract organic facies analyses quantify the coal constituents and plot various associations to discriminate the paleoenvironment for coal bearing successions this allows the relation of coal composition to mire ecosystems or environments coal petrographic models are used extensively to reconstruct the nature of ancient peat forming environments many authors proposed relations between specific maceral assemblages and or micro lithotypes and peat forming environments the key controlling factors which affect peat environment include hydrogeology redox ph vegetation type clastic influx sedimentation and peat accumulation rate etc recent advancements in coal maceral study and organic petrology reveal the pros and cons of the available indices and models the main reasons for the failure of the petrographic models are oversimplification of the effects of humification on tissue preservation vs destruction the use of post diagenetic processes e g geochemical gelification in determining depositional environments changes in petrographic composition related to floral evolution geological age rank increase and compaction lack of distinction between different inertinite maceral in some models here the widely used petrographic indices and models are reviewed based on the observations of several workers and the applicability and concepts of paleo environmental reconstruction are discussed a multi disciplinary approach including petrography palynology chemistry etc has been recommended which is more logical and scientific than the exclusive use of petrographic composition for paleoenvironmental interpretation

seepage in isfjorden and its tributary fjords west spitsbergen abstract this study analyses pockmark morphology and their spatial distribution in isfjorden relative to seabed morphology bedrock geology fault systems glacial landforms and processes using multibeam bathymetric data it provides insight into the possible mechanisms of pockmark formation high density pockmark field evolution and fluid migration pathways a total of 1304 pockmarks occur in the isfjorden at water depths of 40 to 320 m varying from circular to elongate in plan view their diameter ranges from 14 to 265 m and their depths from 1 to 11 m elongate pockmarks are dominant in the isfjordbanken and outer isfjorden where the seafloor is influenced by the west spitsbergen current the west spitsbergen fold and thrust belt and other fault systems sub cropping at the isfjorden seafloor correlate spatially with the high density pockmark zones the pockmarks are preferentially located on the marine sediments draping the bedrock of isfjorden fjord system they are most abundant in the areas underlain by jurassic cretaceous and the triassic lower jurassic bedrock pockmarks found ahead of submarine slope failures may have formed due to dewatering of soft sediments as a result of rapid increase of overpressure caused by deposition of glacigenic debris lobes fault conduits potential source rock and thin postglacial sediment layers are found to be crucial for the formation of pockmarks modeling results of the near shore subsea permafrost and potential gas hydrate stability zone imply thawing permafrost and gas hydrate dissociation as additional possible mechanisms for pockmark formation in isfjorden

characterizing coal cleats from optical measurements for cbm evaluation abstract in this study we apply fracture characterization techniques common to many other reservoir rocks to coals additionally the data gathered from this technique is used to determine fracture permeability and porosity based on a cubic relationship between permeability and porosity as a function of aperture and spacing however these data are in an unconfined stress state to relate this information to the subsurface which is in a confined state the results are then compared and calibrated to permeability data determined from laboratory triaxially confined samples using the same sample material a 1d scanline technique is used to gather data on cleat aperture spacing height and frequency sixteen different coals from several european basins were examined creating a large dataset 8000 individual data measurements this data was gathered from blocks of coals and from polished sections the polished sections were digitally scanned under the microscope to create an image of the whole section as a result we examined a range of scales from micrometers to centimeters maximum minimum and median values are determined for each attribute to clearly define the limits of resolution of the data a practical pore resolution is applied to a power law function of the data cleat attributes were further examined to determine a relationship with cleat type e g face or butt and lithotype power law distributions of butt cleat attributes are similar to the distributions found in lithotype it was concluded that butt cleats are more strongly related to lithotype and thus bed thickness and mechanical strength of the bed than face cleats cleat aperture and spacing depend on cleat type a face to butt cleat ratio of 5 1 given an aperture of about 12 m was found this is similar to a published anisotropy in permeability where face cleats are five times more permeable than butt cleats cleat porosity from aperture and spacing is several times greater than cleat porosity calibrated to laboratory permeability under stress the calibrated porosity ranged from 0 01 to 1 8 and agrees with published values of in situ cleat porosity thus aperture width due to an increase in stress is predicted to decrease four times this data can be used to calibrate reservoir simulators for cbm production

geodetic evidence for a low slip rate in the altyn tagh fault system the collision between india and asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east asia geological slip rate estimates of 20 30 mm yr 1 suggest that the largest of these faults the 2 000 km long altyn tagh fault system on the northern edge of the tibetan plateau absorbs as much of the indo asian convergence signal as do the himalayas partly by oblique slip and partly by contraction and mountain growth however the predictions of dynamic models for asian deformation and the lower bounds of some geological slip rates estimates 3 9 mm yr 1 refs 7 8 suggest that the altyn tagh system is less active here we report geodetic data from 89 91 degrees e that indicate left lateral shear of 9 5 mm yr 1 and contraction of 3 1 mm yr 1 across the altyn tagh system this result combined with our finding that at 90 degrees e tibet contracts north south at 9 1 mm yr 1 supports the predictions of dynamic models of asian deformation

miocene cooling in the northern qilian shan northeastern margin of the tibetan plateau revealed by apatite fission track and vitrinite reflectance analysis apatite fission track and vitrinite reflectance data from phanerozoic rocks of the northern qilian shan and jiuxi basin at the northeastern margin of the tibetan plateau show a complex thermal history with multiple paleothermal events peak paleotemperatures reached in the middle cretaceous suggest that hydrocarbon generation occurred in the basin at that time paleozoic mesozoic samples show evidence of a middle tertiary cooling episode between 20 and 10 ma this thermal fingerprint is significant because stratigraphic evidence for miocene exhumation is overwhelmed by spectacular pliocene pleistocene deformation and erosion we interpret the miocene cooling as recording initial exhumation of the northern qilian shan earlier than other models have proposed i e after 6 5 ma miocene cooling is broadly coincident with cenozoic uplift and exhumation recorded elsewhere in the tibetan tarim region

did the altyn tagh fault extend beyond the tibetan plateau abstract the pre miocene northeastern termination of altyn tagh fault is a critical outstanding problem for understanding the mechanics of cenozoic deformation resultant from the indo asian collision and mechanisms of tibetan plateau formation structures beyond the widely accepted ne end of the altyn tagh fault near the town of yumen are needed in order to accommodate strike slip deformation related to plate like lateral extrusion tectonics but structures with the necessary slip magnitudes and histories have not been identified we report on a series of newly recognized and documented e to ene striking faults within the alxa block ne of the tibetan plateau that are visible on remotely sensed images and confirmed by field studies these structures are demonstrably left lateral faults based on offset geology and kinematic indicators such as striae and s c fabrics in fault gouge the faults have post cretaceous offsets of at least tens to possibly 150 km but limited post miocene displacement constrained by offset sedimentary basins these characteristics suggest that strike slip faults of the alxa region have a similar structural history as the central eastern altyn tagh fault and can provide a mechanism for accommodating oligocene early miocene extrusion along the altyn tagh fault

distribution of thermogenic methane in carboniferous coal seams of the donets basin ukraine applications to exploitation of methane and forecast of mining hazards abstract the main purpose of this contribution is to estimate methane production and to define its migration paths and storage in the donets basin formations for exploitation of methane and forecast of mining hazards in order to study methane migration and storage maps of production calculated by 2d modelling adsorption capacity of methane in coal and present day methane contents were constructed for an altitude of 300 m close to 500 m depth in this basin the results show that three principal factors influenced the methane migration and accumulation in donets basin 1 faults that acted as migration pathways 2 a replacement of thermogenic methane by endogenic co 2 in the central and se parts and 3 the occurrence of magmatic events in some areas in this basin finally in donbas the areas with the highest methane potential and the maximum risk of outburst are not the areas with anthracite that produce the highest volume of methane but areas with volatile bituminous coals where an impermeable cover preserved the accumulated gas until the cenozoic and where dextral shear belts facilitated its migration

methanotrophic activity in carboniferous coalbed rocks abstract carboniferous coalbed rocks originating from the lublin coal basin south east poland were investigated for the presence and activity of aerobic methanotrophic bacteria laboratory studies of samples collected from 914 to 1004 m below earth s surface and performed at 30 c 100 water capacity whc and 10 v v headspace ch 4 revealed microbial methane oxidation which ranged from 0 13 to 0 75 m ch 4 g 1 day 1 methanotrophic activity ma was also investigated as a function of temperature 5 30 c moisture content 25 200 whc and substrate concentration 1 30 v v ch 4 the highest ma was recorded at 30 c 100 whc and 20 ch 4 v v indicating the mesophilic and microaerophilic character of methanotrophic bacteria mb present in the coalbed lack of detectable ma at 5 and 10 c shows narrow temperature tolerance of mb which may result from a long term isolation of the bacterial habitat and stability of thermal conditions in the coalbed cryo sem revealed presence in the investigated rocks of bacteria c a 2 2 5 m long and 0 5 1 m wide and spore like structures 0 5 1 m in diameter these observations were confirmed by fluorescence in situ hybridization with probes mg705 5 fluoresceine mg84 5 cy3 and ma450 5 cy5 which showed that enrichments in nms medium contain types i and ii mb of similar size identification performed with the use of dna amplification of 16s rrna targeted group specific primers confirmed the presence of bacteria belonging to methylosinus methylomicrobium methylocystis and methylocaldum here we show that coalbed rocks constitute a habitat for diverse mb

a modified approach to estimating coal and coal gas resources example from the sand wash basin colorado the significant increase in united states gas production from coal beds over the past 5 yr has encouraged exploration and development of coal gas resources worldwide accurate assessment of coal and coal gas resources and delineating areas within basins containing the largest resources are important aspects of resource development previous resource studies may have overestimated or underestimated coal gas resources because the ash and density terms of resource equations were inconsistently or inappropriately considered in basins where coal analysis data are sparse coal gas resources are best calculated on an ash free basis the density contrast between ash forming minerals and organic matter is large enough that the weight percent ash is much larger than the corresponding volume percent therefore a correction factor relating weight percent ash free coal and ash yield determined from proximate analysis to ash free coal volume is required to accurately calculate coal gas resources rather than using one density value as has been done in previous studies our calculations require that bulk coal density including mineral matter be distinguished from ash free coal density coal and coal gas resources of the williams fork and fort union formations in the sand wash basin determined from modified resource equations are 291 billion tons short tons 264 billion t metric ton and 79 tcf footnote 2 2 tm3 these resources are significantly higher than previous estimates of basin resources of 34 5 billion tons 31 3 billion t of coal and 14 tcf 0 4 tm3 of coal gas the williams fork formation contains 79 of the coal and 95 of the coal gas resources reflecting greater maximum burial depth and higher gas contents the fort union formation contains 21 of the coal but only 5 of the coal gas resources coal gas resources are greatest in the central part of the basin where williams fork resources approach 70 gcf footnote mi sup 2 0 8 gm3 km2 in comparison the san juan basin the nation s most prolific coal gas producing basin has maximum coal gas resources approaching 35 gcf mi2 0 4 gm3 km2 the high resource density in the sand wash basin is due to greater net coal thickness rather than high gas content

organic geochemistry and petrology of subsurface paleocene eocene wilcox and claiborne group coal beds zavala county maverick basin texas usa abstract coal samples from a coalbed methane exploration well in northern zavala county maverick basin texas were characterized through an integrated analytical program the well was drilled in february 2006 and shut in after coal core desorption indicated negligible gas content cuttings samples from two levels in the eocene claiborne group were evaluated by way of petrographic techniques and rock eval pyrolysis core samples from the paleocene eocene indio formation wilcox group were characterized via proximate ultimate analysis in addition to petrography and pyrolysis two indio formation coal samples were selected for detailed evaluation via gas chromatography and fourier transform infrared ftir and 13c cpmas nmr spectroscopy samples are subbituminous rank as determined from multiple thermal maturity parameters elevated rank relative to similar age coal beds elsewhere in the gulf coast basin in the study area is interpreted to be a result of stratigraphic and or structural thickening related to laramide compression and construction of the sierra madre oriental to the southwest vitrinite reflectance data along with extant data suggest the presence of an erosional unconformity or change in regional heat flow between the cretaceous and tertiary sections and erosion of up to 5 km over the cretaceous the presence of liptinite rich coals in the claiborne at the well site may indicate moderately persistent or recurring coal forming paleoenvironments interpreted as perennially submerged peat in shallow ephemeral lakes with herbaceous and or flotant vegetation however significant continuity of individual eocene coal beds in the subsurface is not suggested indio formation coal samples contain abundant telovitrinite interpreted to be preserved from arborescent above ground woody vegetation that developed during the middle portion of mire development in forested swamps other petrographic criteria suggest enhanced biological chemical and physical degradation at the beginning and end of indio mire development fluorescence spectra of sporinite and resinite are consistent and distinctly different from each other attributed to the presence of a greater proportion of complex asphaltene and polar molecules in resinite gas chromatography of resinite rich coal shows sesquiterpenoid and diterpenoid peaks in the c14 17 range which are not present in resinite poor coal quantities of extracts suggest bitumen concentration below the threshold for effective source rocks 30 50 mg hydrocarbon g total organic carbon hc g toc saturate aromatic and pristane phytane pr ph ratios are different from values for nearby tertiary reservoired crude oil suggesting that the indio coals are too immature to source liquid hydrocarbons in the area however moderately high hi values 200 400 mg hc g rock may suggest some potential for naphthenic paraffinic oil generation where buried more deeply down stratigraphic structural dip extractable phenols and c20 alkanes are suggested as possible intermediates for acetate fermentation in microbial methanogenesis which may however be limited by poor nutrient supply related to low rainfall and meteoric recharge rate or high local sulfate concentration

geological controls on gas content distribution of coal seams in the kinik coalfield soma basin turkey abstract the miocene soma coal basin may be one of the most promising areas for low rank coalbed methane in turkey so far the coalbed methane potential of the coal seams in the kinik coalfield soma basin has not been adequately studied a systematic investigation was performed on the gas content distribution of the kp1 and km2 coal seams and its geological controls which has been based on the geological data and the experimental results of 84 coal samples taken from 37 coal exploration wells in the kinik coalfield soma basin samples were analyzed in terms of coal properties and gas content the gas content was measured by the direct method based on the canister desorption test the gas content of the kp1 and km2 coal seams range from 0 90 to 2 61 m3 t and 0 51 to 3 86 m3 t respectively on as received basis with increasing trend from west to east areas in both seams diffusivity values of the kp1 and km2 coal seams vary from 2 84 10 5 min 1 to 56 4 10 5 min 1 and from 0 64 10 5 min 1 to 54 3 10 5 min 1 respectively the gas content of the kp1 seam has not been correlated with the coal properties whereas the gas content of the km2 seam has positive correlation with fixed carbon content and gross calorific value and negative correlation with moisture and ash content normal faults are well developed in the study area play an important role at gas migration causing gas dissipation and reduced gas content of each coal seam in the northern part the low gas content may result from the combined effects of the geological structure thickness of overlying unit burial depth and coal thickness in the southern part the gas content of coal seams is controlled by the combined effects of relatively favorable factors including fewer normal faults thicker overlying unit high burial depth and thick coal seam the variation of the gas content for the coal seams is a comprehensive reflection of geological factors with each coal seam has its own pattern of gas distribution and this should be considered for the future coalbed methane exploration and development studies in soma basin

predicting methane accumulations generated from humic carboniferous coals in the donbas fold belt ukraine the numerical modeling of the ukrainian part of the donbas fold belt indicates that the coalification pattern was controlled mainly by the maximum burial depth of coal seams and the heat flow hf 40 75 mw m2 during the permian the coalification pattern was overprinted by magmatic events during the late permian in the south syncline 150 mw m2 and during the permian triassic in the north of the krasnoarmeisk region 120 mw m2 the coalification pattern shows a strong increase in vitrinite reflectance values toward the east and southeastern parts of the study area likely caused by 1 an eastward increase in burial depth 2 a probable eastward increase in hf and 3 probable magmatic activity an increase in total erosion toward the eastern and southeastern parts was also observed with a maximum erosional amount of approximately 8 km 5 mi in the southeastern part of the study area the basin modeling of this area predicts that the main phase of hydrocarbon generation occurred during the carboniferous early permian subsidence the magmatic events that occurred during the permian triassic caused renewed pulses of hydrocarbon generation a large amount of the generated hydrocarbons was lost to the surface because of a lack of seals however the numerical simulation predicts accumulations of about 2 tcf 57 billion m3 of methane generated from carboniferous coals in the south and main synclines where lower permian seal rocks are preserved finally this study provides data on methane resources along the northern flank of the basin which remains a significant frontier for natural gas exploration

reservoir parameters and maceral composition of coal in different carboniferous lithostratigraphical series of the upper silesian coal basin poland abstract laboratory tests were carried out on coal samples taken from mine openings of selected coal mines in the upper silesian coal basin the analyses involved maceral composition vitrinite inertinite and liptinite group and vitrinite reflectance on the one hand and reservoir parameters coal permeability and effective porosity on the other the results are compared samples with high values of coal permeability are characterized by vitrinite contents of ca 60 and samples with the lowest permeability by vitrinite contents of 40 the vitrinite rich bright coals are brittle and prone to crushing caused by tectonic pressures moreover coal permeability is more strongly anisotropic in the bright coals of the cracow sandstone and the mudstone series than in the dull coals of the upper silesian sandstone series in bright coals permeability is much along the direction parallel to vitrain layers good reservoir parameters such as permeability and effective porosity are crucial for fluid flow through the coal seams and thus successful coalbed methane exploitation in the upper silesian coal basin cracow sandstone and mudstone series with vitrinite rich coals should be a good target though serious geological problems must first be overcome

the influence of petrological properties and burial history on coal seam methane reservoir characterisation sydney basin australia abstract gas content of coals continuously change throughout their burial histories as a result of the changing state of equilibrium of the coal gas system caused by variations in p t conditions and coal rank to fully evaluate the prospectivity of a coalbed methane resource numerous coal properties burial history p t conditions hydrology and the likelihood of secondary biogenic gas generation need to be considered with respect to gas sorption capacity gas contents and permeability previous studies have given differing interpretations on relationships between rank and maceral composition with sorption capacity the maximum gas storing capacities for sydney basin coals is inversely related to rank up to medium volatile bituminous but a coked contact metamorphosed coal has an elevated capacity comparison of sorption capacities of coals having similar ranks and variable maceral group composition indicate that rank has a dominating effect over any effects of organic matter type for the sydney basin coals the in situ gas contents on average increase with depth up to about 600 m and with further increases in depth to 900 m the gas contents tend to plateau or even decrease such a trend probably is consistent with the combined effects of pressure and temperature on the gas sorption capacity during the geological history r mode cluster analyses of the coal and gas properties yield a positive correlation between gas contents and inertinite abundance this is related to undersaturation of the vitrinite rich coals possibly due to higher permeability and consequent leakage of more gas from vitrinite rich coals than from inertinite rich coals although a large amount of methane and other hydrocarbon gases would have been generated in the sydney basin at maximum burial during the early cretaceous a large proportion of the gas might not have been sorbed within the coal due to limited gas sorption capacities and enhanced diffusivity at high temperatures upon uplift gas that migrated from deeper in the sequence or from shallower biological activity may have been sorbed into the coals without secondary gas replenishment however many of these coals remain significantly undersaturated the areas that contain considerable amounts of secondary biogenic gas are highly prospective for coalbed methane production partly because of the higher gas contents but also because of the higher permeability which is required for access of the microbes and nutrients in meteoric waters to fully evaluate prospectivity of coalbed methane resources numerous coal properties burial history geologic setting and the likelihood of secondary biogenic gas generation need to be considered with respect to gas sorption capacity gas contents and permeability

geology of coalbed methane reservoirs in the southeast qinshui basin of china abstract the no 15 coal seam of the pennsylvanian taiyuan formation and the no 3 coal seam of the permian shanxi formation in the southeast qinshui basin are relatively thick 3 m laterally continuous and are of anthracite rank ro 2 2 4 5 the depth of these coal seams is generally between 200 and 700 m a tectonic thermal event during the jurassic to cretaceous yanshanian orogeny controlled coalification and thermogenic hydrocarbon generation because the generation of late stage bacterial gas coalbed methane in the southeast qinshui basin occupies two zones which are the mixed thermogenic and late stage bacterial gas zone near the basin margins and the dominantly thermogenic gas zone in the structurally deep part of the basin basin hydrodynamics causes low gas content in the shallow subsurface 20 m3 t because cleats are rare and are mostly filled with calcite the permeability of the coalbed methane reservoir is controlled by shear fractures the recharge and flow of groundwater not only control gas content but also control reservoir pressure abnormally high pressure reservoir in the deep stagnant zone is a favorable area for coalbed methane exploration and development the current coalbed methane wells are generally completed in the deep stagnant zone

differential transport of co2 and ch4 in coalbed aquifers implications for coalbed gas distribution and composition coalbed gas content and composition are critical for the successful exploration and production of coalbed methane we investigated the differential transport of a preadsorbed co2 ch4 gas mixture along a coalbed aquifer by groundwater flow or across a coal bed by upward diffusion through pore water consistent analytical approximations and numerical solutions were obtained for typical cases the results suggest that differential transport of ch4 and co2 in a water saturated coal seam is mainly controlled by their adsorption equilibrium in coals and solubilities in water although co2 is about 20 times more soluble than ch4 in water at temperatures lower than 50c the transport of co2 from a coal seam is only several times more efficient than that of ch4 because of the stronger adsorption of co2 than ch4 in coals preferential transport of co2 over ch4 by groundwater advection can substantially accumulate more gas rich in co2 at downstream or near discharge zones if gas trapping structures exist and it may cause low total gas content of ch4 near recharge zones which may explain the co2 and ch4 distribution in the san juan and powder river basins and the undersaturation of gas in many other coals the separation and redistribution of coalbed gas by transport processes may also be complicated by late stage biogenic gas generation with infiltration of meteoric water with nutrients and gas producing microbes into the coal beds as suggested for some basins overall hydrogeologic systems strongly influence the distribution of coalbed gas content and composition in coal seams

a study of hydrogeology and its effect on coalbed methane enrichment in the southern junggar basin china this paper analyzes regional hydrogeological conditions and divides the study area into three hydrogeological types and seven hydrogeological units to investigate hydrogeology and its effect on coalbed methane cbm enrichment in the southern junggar basin china from this work it is found that the groundwater flow paths in the study area are the joint effects of south to north and west to east flows this study also shows that microbial gases are widely developed although the depth limit of microbial gas occurrence is still unclear in the study area microbial co2 reduction is the leading formation path in the study area except for the houxia region where fermentation is the formation mechanism the abnormally high co2 in stagnant zones i e water flow is slow and stagnant is mainly associated with methanogenesis whereas relatively low co2 microbial or thermogenic is present where water flow is active the average cbm content within the xishanyao formation changes within various hydrogeological units moreover the average cbm content within the badaowan formation of the same hydrogeological unit e g fukang suggests that the hydrogeological and cbm enrichment conditions are different within various structural types overall the hydrogeological conditions exert control on the gas content in the study area that is the gas content is high in stagnant zones finally influenced by supplemental microbial gases changes in the cbm oxidation zone are relatively complex in the study area the depth of which has no obvious correlation with hydrogeological conditions and changes significantly from west to east

evaluating the gas content of coals and isolated maceral concentrates from the paleocene guasare coalfield venezuela abstract this work presents the results from evaluating the gases sorbed by coal samples extracted from the paleocene guasare coalfield marcelina formation northwestern venezuela as well as by their distinct maceral concentrates the aim of this work has been to obtain an initial experimental main value of the gas content per unit weight of high volatile bituminous a coal samples from the open pit paso diablo mine an additional goal was to study differences in the ch 4 storage ability of the distinct maceral groups forming part of the coal matrix both the coal samples and the maceral concentrates were studied by thermogravimetric analysis tga in order to determine the temperature to be used in subsequent experiments on line analyses of hydrocarbons c 1 c 2 c 3 and co 2 yielded gas concentrations plus 13 c values thermogenic gas is prevalent in the guasare coals with vitrinite reflectance r o values from 0 65 to 0 88 the amount of gas retained in the coals and maceral concentrates was measured with a special device that allows determination of the volume of gas sorbed by a solid sample subjected to controlled thermal treatment the average coalbed gas concentration obtained was 0 51 cm 3 g the following list of maceral concentrates shows the relative capacity for the volume of sorbed gas per unit weight inertinite low density vitrinite liptinite high density vitrinite it is concluded that the gas volumes retained in the distinct maceral concentrates are not controlled by porosity but rather by their microscopic morphology

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

the occurrence of a secondary zone of coal bed methane in the southern part of the upper silesian coal basin southern poland potential for methane exploitation abstract coal bed methane cbm exploitation in the upper silesian coal basin has in spite of earlier failures again aroused investor interest carboniferous coal seams at depths of 200 500 m are characterized by coal permeability values estimated at 27 230 md and degrees of methane saturation almost 100 that suggest future successful exploitation based on the results of geological surveys archived in the polish geological institute the shallow cbm zone is defined as a gas horizon distinct from a deep cbm zone the disposition of the shallow zone follows the topography of the upper carboniferous paleorelief and is deemed the most important factor controlling methane distribution within this zone the most favorable places for cbm accumulation within the shallow coal seams are erosional highs and the slopes of upper carboniferous ridges associated with fault zones the thickness of the zone 200 m and methane contents 8 m 3 t coal daf are highest in these places the nearly full saturation of the coal seams with methane reflects the involvement of two genetic types of gas indigenous late stage microbial methane and thermogenic methane derived from the deeper coals the favorable geological characteristic of this shallow cbm zone is a potential source of energy for upper silesia

asymmetric deformation in the backarc region of the kuril arc northwest pacific new insights from analogue modeling 1 the eocene to middle late miocene tectonic evolution of the kuril arc and backarc region has been simulated with analogue experiments the experiments simulate asymmetric deformation in the overriding plate due to anticlockwise rollback of the subducting pacific plate the results show the formation of a n s to ne sw oriented dextral shear zone near the far edge of the retreating boundary analogous to the sakhalin hokkaido dextral shear zone contemporaneously normal faults and grabens form striking parallel to the retreating boundary near the far edge but striking more oblique near the hinge point and away from the retreating boundary this is similar to extensional structures observed in the kuril basin and the sea of okhotsk furthermore the model shows that the amount of extension progressively decreases away from the retreating boundary this appears to have also happened in the kuril okhotsk region as evidenced by crustal thickness variation in the region finally the model results show that extension is increasingly accommodated by the region close to the retreating boundary with progressive deformation this can account for the eocene early miocene extension in the sea of okhotsk followed by miocene spreading in the kuril basin

hydrogeologic factors affecting gas content distribution in coal beds gas content in coal is not fixed but changes when equilibrium conditions within the reservoir are disrupted therefore gas content distribution in coal varies laterally within individual coal beds vertically among coal beds in a single well and within thicker coal beds major hydrogeologic factors affecting gas content variability include gas generation coal properties and reservoir conditions gas generation affects gas content variability on a regional scale whereas coal properties influence gas content distribution on a regional and local scale reservoir conditions affect gas content more locally within specific fields or individual wells the potential for high gas content is controlled directly by the amount of thermogenic and secondary biogenic gases generated from the coal which in turn are controlled by burial history maceral composition and basin hydrodynamics variability in mineral matter ash and moisture content sorption behavior among macerals diffusion coefficients and permeability result in heterogeneous gas content distribution gas content decreases with decreasing pressure and temperature and coal beds become undersaturated with respect to methane during basin uplift and cooling gas content generally increases where conventional and hydrodynamic trapping of coal gases occur and may decrease in areas of active recharge with downward flow potential and or convergent flow where there is no mechanism for entrapment

tectonic history of the altyn tagh fault system in northern tibet inferred from cenozoic sedimentation the active left slip altyn tagh fault defines the northern edge of the tibetan plateau to determine its deformation history we conducted integrated research on cenozoic stratigraphic sections in the southern part of the tarim basin fission track ages of detrital apatites existing biostratigraphic data and magnetostratigraphic analysis were used to establish chronostratigraphy whereas composition of sandstone and coarse clastic sedimentary rocks was used to determine the unroofing history of the source region much of the detrital grains in our measured sections can be correlated with uplifted sides of major thrusts or transpressional faults implying a temporal link between sedimentation and deformation the results of our studies together with existing stratigraphic data from the qaidam basin and the hexi corridor suggest that crustal thickening in northern tibet began prior to 46 ma for the western kunlun shan thrust belt at ca 49 ma for the qimen tagh and north qaidam thrust systems bounding the north and south margins of the qaidam basin and prior to ca 33 ma for the nan shan thrust belt these ages suggest that deformation front reached northern tibet only 10 5 m y after the initial collision of india with asia at 65 55 ma because the aforementioned thrust systems are either termination structures or branching faults of the altyn tagh left slip system the altyn tagh fault must have been active since ca 49 ma the altyn tagh range between the tarim basin and the altyn tagh fault has been a long lived topographic high since at least the early oligocene or possibly late eocene this range has shed sediments into both the tarim and qaidam basins while being offset by the altyn tagh fault its continuous motion has made the range act as a sliding door which eventually closed the outlets of westward flowing drainages in the qaidam basin this process has caused large amounts of oligocene miocene sediments to be trapped in the qaidam basin the estimated total slip of 470 70 km and the initiation age of 49 ma yield an average slip rate along the altyn tagh fault of 9 2 mm yr remarkably similar to the rates determined by gps global positioning system surveys this result implies that geologic deformation rates are steady state over millions of years during continental collision

pore characteristics of wilcox group coal u s gulf coast region implications for the occurrence of coalbed gas abstract pore characteristics of 27 subbituminous coal samples 16 mesh splits from the paleocene eocene wilcox group of north louisiana ouachita and caldwell parishes and south texas zavala county were examined in relation to desorbed gas content coal gas of the wilcox group is primarily biogenic in origin thermogenic gas also may be present in some areas on an as received basis desorbed gas contents range from 0 59 to 1 28 m 3 t for ouachita parish samples 0 37 to 5 19 m 3 t for the caldwell parish samples and 0 02 to 0 06 m 3 t for the zavala county samples for louisiana coal samples micropore surface area and volume are correlated to the desorbed gas content of the wilcox group coal correlations r 0 50 and 0 47 respectively suggesting that micropore surface area and volume are important in terms of gas holding capacity adsorption by micropores appears to be the primary form of gas storage for the louisiana coal samples micropore surface area and volumes also are strongly correlated with the carbon ash yield ratio r 0 97 and 0 94 respectively indicating that gas sorption occurs primarily on organic matter mineral matter appears to reduce the sorption capacity of the coal micropore width decreases with depth r 0 63 probably as the result of increasing pressure and coal rank with depth for the louisiana coal samples mesopore surface area is negatively correlated with the carbon ash yield ratio r 0 70 suggesting that mesopores are preferentially associated with mineral matter average mesopore size is correlated with desorbed gas r 0 80 for the relatively shallow ouachita parish samples average depth 441 m 1446 ft these results suggest that the permeability of the wilcox coal is greater in the shallow stratigraphic intervals compared to deeper intervals additionally mesopore size decreases with depth r 0 80 for ouachita parish coal samples negative correlations of gas with mesopore surface area r 0 74 and mesopore volume r 0 56 strongly suggest that gas is not adsorbed in mesopores and that free gas may be present in larger mesopores macropores or fractures of the wilcox coal results also suggest that moisture in ouachita parish samples is present in mesopores moisture in mesopores may have blocked gas adsorption the low gas south texas samples average depth 313 m 1026 ft are markedly different from the louisiana samples specifically micropore surface area and micropore volume are negatively correlated with desorbed gas for the texas samples r 0 21 and 0 36 respectively geologic or environmental conditions probably were not conducive to the generation or storage of microbial gas in the zavala county coals the geologic settings i e salinity of formation water groundwater recharge permeability of coal of each study area are important factors that need to be considered in relation to the potential for generation or storage of microbial gas in south texas tectonic stress may have led to a reduction in permeability in the wilcox group coal creating an unfavorable environment for the generation or preservation of microbial gas the subbituminous rank of the zavala coals is also too low for significant thermogenic gas generation to have occurred

burial and exhumation history of the galilee basin australia implications for unconventional hydrocarbon prospectivity this multidisciplinary study describes the burial and exhumation history of the frontier galilee basin in central queensland australia with implications for understanding its geohistory and unconventional gas prospectivity seismic interpretation stratigraphic mapping and an analysis of exhumation through quantifying overcompaction show total subsidence of approximately 2 km 6600 ft from the carboniferous to the late cretaceous punctuated by two major exhumation events triassic exhumation was less than 600 m 1970 ft whereas late cretaceous exhumation was in the order of 1000 m 3300 ft increasing eastward to greater than 1600 m 5250 ft geohistory reconstructions show that permian coal measures generated up to 45 m3 t 1590 ft3 t of gas when modeled temperatures exceeded 100 c 210 f during maximum burial of 1 5 2 km 4920 6560 ft in the late cretaceous in the carboniferous to the mid cretaceous the basin was situated to the west of the eastern australian subduction zone where proto pacific oceanic lithosphere was subducted until circa 100 ma when subduction ceased our study shows that the geohistory of the basin is characterized by rapid subsidence of 50 m m y 165 ft m y followed by rebound at circa 95 ma resulting in an uplift and erosion phase the undersaturation of the coals at present day is explained by this uplift event carbon isotopes indicate that the remaining gas 8 m3 t 280 ft3 t is of mixed biogenic and thermogenic origin therefore dynamic surface topography driven by subduction dynamics and slab breakoff had a profound effect on the subsidence uplift and resource potential of the galilee basin

geological controls on the formation and distribution of gas in british coal measure strata abstract the methane ethane higher alkanes and nitrogen found in british coal seams are residual products of coalification occasionally complemented by petroleum derived hydrocarbons carbon dioxide a minor constituent of coal seam gas may have been introduced during the phase of cleat mineralisation following uplift helium and argon are considered to be radiogenic in origin variations in seam methane content with depth geographic location and rank can be interpreted in terms of the coalification and erosion history of a coalfield however the limitations inherent in an analysis in which coal rank is represented by a single parameter must be recognised there are indications that the methane content of a seam is not likely to exceed the methane sorption capacity of the coal determined at a temperature commensurate with that obtaining at the maximum burial depth research in the east midlands coalfield suggests that structurally controlled migration of coalification gas was contemporaneous with folding during the permo carboniferous erosion period gas was lost from outcropping seams subsequently the bulk permeability of the seams must have been reduced perhaps as a result of cleat mineralisation because no re distribution of methane appears to have occurred in response to later tertiary deformation and gas contents of seams at incrop below the base of the permo triassic have remained zero data on the effects of faulting on seam gas contents are few but the expectation is that faults of appropriate age and orientation whilst inhibiting in seam migration may in some instances have aided cross measures movement of gas elevated seam ethane and propane contents are frequently encountered in seams disturbed by oil bearing faults

hydrodynamics of coalbed methane reservoirs in the black warrior basin key to understanding reservoir performance and environmental issues abstract the black warrior basin of the southeastern united states hosts one of the world s most prolific and long lived coalbed methane plays and the wealth of experience in this basin provides insight into the relationships among basin hydrology production performance and environmental issues along the southeast margin of the basin meteoric recharge of reservoir coal beds exposed in an upturned fold limb exerts a strong control on water chemistry reservoir pressure and production performance fresh water plumes containing na hco3 waters with low tds content extend from the structurally upturned basin margin into the interior of the basin northwest of the plumes coal beds contain na cl waters with moderate to high tds content carbon isotope data from produced gas and mineral cements suggest that the fresh water plumes have been the site of significant bacterial activity and that the coalbed methane reservoirs contain a mixture of thermogenic and late stage biogenic gases water produced from the fresh water plumes may be disposed safely at the surface whereas underground injection has been used locally to dispose of highly saline water wells in areas that had normal hydrostatic reservoir pressure prior to development tend to produce large volumes of water and may take up to 4 a to reach peak gas production in contrast wells drilled in naturally underpressured areas distal to the fresh water plumes typically produce little water and achieve peak gas rates during the first year of production environmental debate has focused largely on issues associated with hydrologic communication between deep reservoir coal beds and shallow aquifers in the coalbed methane fields of the black warrior basin a broad range of geologic evidence suggests that flow is effectively confined within coal and that the thick intervals of marine shale separating coal zones limit cross formational flow

horizontal stress anisotropy and effective stress as regulator of coal seam gas zonation in the sydney basin australia abstract coal seam gas zonation in the sydney basin nsw australia is related to basin hydrodynamics and hydrochemical facies evolution along the flow path from the subcrop to the basin center biogenic methane corresponds with meteoric water under hydrostatic pressure and persists down to the top of the geopressured zone 800 to 1000 m thermogenic gases including wet hydrocarbons can reach up to relatively shallow horizons of less than 500 600 m depth in the transition zone between the top of the geopressured and base of the hydrostatic zone a mixed water and gas regime prevails comprising brackish waters and gases of mixed biogenic thermogenic and inorganic origins including co 2 mechanisms for and the role of stress in the development of this layered hydrogeological and gas environment are investigated in this paper the inverse relationship between effective horizontal stress and permeability in coals through regulation of cleat volumes is well documented and there is evidence of regionally compartmentalized stress regimes with depth within the sydney and other eastern australian coal basins this regional stress regime can be overprinted by the effect of localized geological features it is hypothesized that the in situ stress regime plays an important role in the regulation of groundwater flow regimes and extents resulting in the development of the reported gas content and compositional zonation analysis of regional gas and stress data obtained from public and private databases as well as literature supports this hypothesis changes in gas concentration and composition with depth correspond with discernable variations in horizontal stress anisotropy gas contents generally increase with depth down to a peak gas horizon below which concentrations decrease this peak gas zone is coincident with a horizontal stress anisotropy change from moderately high to low levels associated with reverse to strike slip faulting conditions respectively the stress release zone also marks the top of the thermogenic gas zone identified by the first appearance of ethane in the vertical profile this zone also hosts gases of mixed origins biogenic thermogenic and inorganic co 2 and represents a mixed transitional groundwater flow environment the base of the mixed gas zone is the top of the geopressured only flow associated with thermogenic gases and is signaled by the return to high stress reverse faulting conditions below 850 900 m depth in the sydney basin

conceptual exploration targeting for microbially enhanced coal bed methane mecom in the walloon subgroup eastern surat basin australia abstract the sustainable in situ regeneration of microbial biogenic methane or microbially enhanced coal bed methane mecom is an emerging concept being investigated globally promising results and recommendations of a preliminary culture study of walloon subgroup co produced coal seam gas csg waters from the surat basin queensland established the presence of viable methanogens and suggested that in situ methanogenesis could be stimulated using physical and chemical reservoir treatments this paper represents the culmination of a stepwise basin analysis project ultimately aimed at siting potential in situ bioreactor locations in the eastern surat basin the integration of stratigraphically located data on the molecular and isotopic composition of desorbed gases host coal properties and spatially associated waters through the core production zone has allowed the spatial variability and relative influence of hydro geological factors on methanogenesis to be evaluated in detail for the first time higher gas contents and systematically enriched ch 4 and co 2 carbon isotopic compositions in the stratigraphically central coal seams oldest youngest in the upper taroom coal measures tangalooma sandstone lower juandah coal measures are best explained by increased rates of microbial co 2 reduction and substrate depletion there is a building case to trial mecom in the central coal seams in a depleted underperforming well in an area of high permeability integrated microbiological chemical engineering hydro chemical and geological studies are ongoing to further enhance understanding of walloon subgroup csg and the bioreactor potential of the surat basin

geological and hydrological controls on the producibility of coalbed methane geological and hydrological comparison of two united states coalbed methane basins the prolific san juan basin and the marginally producing sand wash basin indicates that coal distribution and rank gas content permeability ground water flow and depositional and structural setting are critical controls on coalbed methane producibility a complex interplay and moreover a synergy amongst these controls determines high productivity this paper proposes a basin scale explanation for the prolific and marginal production in the two basins and that can be applied to evaluation of coalbed methane potential in coal basins worldwide high productivity is governed by 1 thick laterally continuous coals of high thermal maturity 2 basinward flow of ground water through coals of high rank and gas content orthogonally toward no flow boundaries regional hingelines fault systems facies changes and or discharge areas and 3 conventional trapping along those boundaries to provide additional gas beyond that sorbed on the coal surface

coal reservoir characteristics and coalbed methane resource assessment in huainan and huaibei coalfields southern north china abstract the huaibei and huainan coalfields in southern north china contain abundant coalbed methane cbm resources 1 1 10 12 m 3 net accumulated thicknesses of all minable coal seams are 18 32 m in huainan and 8 18 m in huaibei coalfields coal rank in the huainan coalfield high volatile a and b bituminous r o 0 65 0 85 is generally controlled by geothermal metamorphism in comparison coal rank in the huaibei coalfield varies from high volatile a bituminous to semi anthracites 0 8 to 2 8 r o and is controlled by the influence of the cretaceous yanshanian magmatic metamorphism in both coalfields coal reservoirs have low permeability values of 0 0013 0 224 md and porosity of 0 9 10 9 pores in coals are dominated by those with diameter 2 in both coalfields the abundance of microfractures in coals is related to the coal structures commonly more abundant in sheared coals 200 per 9 cm 2 than in the normally structured coals 2 the in place gas content is generally 8 16 m 3 t in huaibei and 10 30 m 3 t in huainan coalfields these data yield an estimated in place cbm resource of 375 247 10 9 m 3 for the huaibei and 722 677 10 9 m 3 for the huainan coalfields based on the cbm resource investigation and reservoir evaluation the most prospective target areas for cbm production are evaluated which include the nanping taoyuan mines of the southern suxian deep coal district and zhuxianzhuang and luling mines in eastern suxian area of the huaibei coalfield and the area around the panji 2 mine in panji xieqiao coal mining districts in the huainan coalfield

variable gas content saturation and accumulation characteristics of weibei coalbed methane pilot production field in the southeastern ordos basin china using diverse geologic and geophysical data from recent exploration and development and experimental results of analysis of gas content gas capacity and gas composition this article discusses how geologic structural and hydrological factors determine the heterogeneous distribution of gas in the weibei coalbed methane cbm field the coal rank of the pennsylvanian no 5 coal seam is mainly low volatile bituminous and semianthracite the total gas content is 2 69 to 16 15 m3 t 95 00 570 33 scf t and gas saturation is 26 0 to 93 2 burial coalification followed by tectonically driven hydrothermal activity controls not only thermal maturity but also the quality and quantity of thermogenic gas generated from the coal gas composition indicates that the cbm is dry and of dominantly thermogenic origin the thermogenic gases have been altered by fractionation that may be related to subsurface water movement in the southern part of the study area three gas accumulation models are identified 1 gas diffusion and long distance migration of thermogenic gases to no flow boundaries for sorption and minor conventional trapping 2 hydrodynamic trapping of gas in structural lows and 3 gas loss by hydrodynamic flushing the first two models are applicable for the formation of two cbm enrichment areas in blocks b3 and b4 whereas the last model explains extremely low gas content and gas saturation in block b5 the variable gas content saturation and accumulation characteristics are mainly controlled by these gas accumulation models

relationships between major ions in coal seam gas groundwaters examples from the surat and clarence moreton basins abstract using a combination of multivariate statistical techniques and the graphical assessment of major ion ratios the influences on hydrochemical variability of coal seam gas or coal bed methane groundwaters from several sites in the surat and clarence moreton basins in queensland australia were investigated several characteristic relationships between major ions were observed 1 strong positive linear correlation between the na cl and alkalinity cl ratios 2 an exponentially decaying trend between the na cl and na alkalinity ratios 3 inverse linear relationships between increasing chloride concentrations and decreasing ph for high salinity groundwaters and 4 high residual alkalinity for lower salinity waters and an inverse relationship between decreasing residual alkalinity and increasing chloride concentrations for more saline waters the interpretation of the hydrochemical data provides invaluable insights into the hydrochemical evolution of coal seam gas csg groundwaters that considers both the source of major ions in coals and the influence of microbial activity elevated chloride and sodium concentrations in more saline groundwaters appear to be influenced by organic bound chlorine held in the coal matrix a sodium and chloride ion source that has largely been neglected in previous csg groundwater studies however contrastingly high concentrations of bicarbonate in low salinity waters could not be explained and are possibly associated with a number of different factors such as coal degradation methanogenic processes the evolution of high bicarbonate nahco 3 water types earlier on in the evolutionary pathway and variability in gas reservoir characteristics using recently published data for csg groundwaters in different basins the characteristic major ion relationships identified for new data presented in this study were also observed in other csg groundwaters from australia as well as for those in the illinois basin in the usa this observation suggests that where coal maceral content and the dominant methanogenic pathway are similar and where organic bound chlorine is relatively abundant distinct hydrochemical responses may be observed comparisons with published data of other nahco 3 water types in non csg environments suggest that these characteristic major ion relationships described here can i serve as an indicator of potential csg groundwaters in certain coal bearing aquifers that contain methane and ii help in the development of strategic sampling programmes for csg exploration and to monitor potential impacts of csg activities on groundwater resources

relationships between water and gas chemistry in mature coalbed methane reservoirs of the black warrior basin water and gas chemistry in coalbed methane reservoirs of the black warrior basin reflects a complex interplay among burial processes basin hydrodynamics thermogenesis and late stage microbial methanogenesis these factors are all important considerations for developing production and water management strategies produced water ranges from nearly potable sodium bicarbonate water to hypersaline sodium chloride brine the hydrodynamic framework of the basin is dominated by structurally controlled fresh water plumes that formed by meteoric recharge along the southeastern margin of the basin the produced water contains significant quantities of hydrocarbons and nitrogen compounds and the produced gas appears to be of mixed thermogenic biogenic origin late stage microbial methanogenesis began following unroofing of the basin and stable isotopes in the produced gas and in mineral cements indicate that late stage methanogenesis occurred along a co2 reduction metabolic pathway hydrocarbons as well as small amounts of nitrate in the formation water probably helped nourish the microbial consortia which were apparently active in fresh to hypersaline water the produced water contains nh4 and nh3 which correlate strongly with brine concentration and are interpreted to be derived from silicate minerals denitrification reactions may have generated some n2 which is the only major impurity in the coalbed gas carbon dioxide is a minor component of the produced gas but significant quantities are dissolved in the formation water degradation of organic compounds augmented by deionization of nh4 may have been the principal sources of hydrogen facilitating late stage co2 reduction

study on coalbed methane accumulation characteristics and favorable areas in the binchang area southwestern ordos basin china article the binchang area of southwestern ordos basin is one of the most promising areas for low rank coalbed methane cbm in china this work investigates the jurassic yanan formation coal and cbm geology and accumulation characteristics of cbm in the southwestern ordos basin based on data from 46 wells and labo ratory measurements of 14 coal samples from 7 mines the results show that coal rank in the binchang area is mainly sub bituminous a and high volatile c bituminous 0 46 0 73 ro coals are dominated by inertinite 14 7 85 6 less abundant are vitrinite 8 5 77 7 and liptinite 1 5 15 2 minerals are found only in small amounts 0 4 8 3 permeability is between 0 04 and 25 3 md and porosity ranges from 2 4 to 20 1 most coal pores are less than 100 nm in diameter making them favorable for gas adsorption but unfavorable for gas permeability pore morphology is represented mainly by micro and mesopores with a well connected and ink bottle shaped narrow throat and wide body morphology these coals are charac terized by a high adsorption volume of more than 3 0 10 3

geological and hydrological controls on the accumulation of coalbed methane within the no 3 coal seam of the southern qinshui basin abstract since 2006 the zhengzhuang zz block has been part of a commercial coalbed methane cbm production area in the southern qinshui basin which has become one of the most productive cbm areas in china however hydrogeological study of the migration gas and groundwater of the zz block has not been systematically launched this study focuses on geochemical analysis including quality analysis and stable isotope analyses for the water from the cbm production wells discusses the groundwater flow pathways and their influencing factors and evaluates the geological and hydrological controls on gas accumulation in the study area the results show that the produced waters produced with total dissolved solids tds values of 152 8 5389 49 mg l are typically fresh water and brackish water the water type is primarily bicarbonate and the dissolved ions are effectively devoid of sulfate calcium and magnesium with the low desulfurization coefficients of 0 24 5 63 the hydrochemical condition is conductive to cbm preservation the predominant flow of groundwater originates from the southwestern source which flows to the north basin center and then shifts to the east deep graben due to the drastic structural variation four hydrodynamic zones were distinguished through the differences in hydrodynamic conditions in the southwest zone i and the central zone ii the gas contents are relatively low 13 17 24 53 m 3 t despite the high thermal maturity r o max 3 31 3 97 however the stagnant zone iii in the north and the deep stagnant zone iv in the southeast show comparatively high gas content 16 5 31 44 m 3 t the complex geostructures act synergistically with the intense hydrodynamic activities for gas accumulation three cbm enrichment modes were distinguished hydrodynamic trapping at structure lows with high hydrostatic pressure conventional trap of impermeable boundary and hydraulic flushing and gas loss through the fault these investigations may serve for cbm exploration and development in the study area

geology spatial distribution of methane content and origin of coalbed gases in upper carboniferous upper mississippian and pennsylvanian strata in the south eastern part of the upper silesian coal basin poland abstract the subject of the investigation was both vertical and horizontal distribution of methane content in coal series within the south eastern part of the upper silesian coal basin in the study area coal deposits are characterized by various methane structures and varied spatial distribution of methane brzeszcze coal deposit located in the upthrow of jawiszowice fault zone represents the so called open methane pattern in which the upper parts of coal bearing series to the depth of 300 500 m seam 327 are naturally degassed beneath methane content rapidly increases with depth and often achieves high values between ten and twenty m 3 ch 4 mg coal daf the area located to the south of jawiszowice fault zone represents the so called closed methane pattern which means that the primary methane zone was reworked due to the forming of carpathian foredeep in the miocene period a thick cover of miocene claystones overlying the carboniferous formations favors gas accumulation in the uppermost parts of the carboniferous coal bearing complex especially in the roof elevations free methane occurs within the elevated part of porous and permeable aziska sandstones covered by miocene claystones the highest methane content characterizes the coal seams which lie within mudstone or upper silesian sandstone series smaller methane content is typical of the seams lying within aziska sandstones the fault tectonics is another factor influencing the distribution of methane content therefore the large size dislocations i e jawiszowice and bzie czechowice fault zones move the high methane coal seams according to throw direction southwards the carboniferous lithology fault tectonics and also miocene claystones covering the carboniferous formations are the crucial factors influencing the various methane contents in the area discussed methane the main component of gases accumulated in coal deposits and the minor components such as ethane propane butanes and carbon dioxide are of thermogenic origin that resulted from variscan coalification whereas the methane of the secondary accumulation in the uppermost part of carboniferous formations beneath the impermeable miocene cover contains a large microbial component which is a result of paleocene infiltration of meteoric waters with nutrients for methane bacteria into the coal series

gas saturation and co2 enhancement potential of coalbed methane reservoirs as a function of depth the influence of moisture temperature coal rank and differential enthalpy on the methane ch4 and carbon dioxide co2 sorption capacity of coals of different rank has been investigated by using high pressure sorption isotherms at 303 318 and 333 k ch4 and 318 333 and 348 k co2 respectively the variation of sorption capacity was studied as a function of burial depth of coal seams using the corresponding langmuir parameters in combination with a geothermal gradient of 0 03 k m and a normal hydrostatic pressure gradient taking the gas content corresponding to 100 gas saturation at maximum burial depth as a reference value the theoretical ch4 saturation after the uplift of the coal seam was computed as a function of depth according to these calculations the change in sorption capacity caused by changing pressure temperature conditions during uplift will lead consistently to high saturation values therefore the commonly observed undersaturation of coal seams is most likely related to dismigration losses into adjacent formations and atmosphere finally we attempt to identify sweet spots for co2 enhanced coalbed methane co2 ecbm production the co2 ecbm is expected to become less effective with increasing depth because the co2 to ch4 sorption capacity ratio decreases with increasing temperature and pressure furthermore co2 ecbm efficiency will decrease with increasing maturity because of the highest sorption capacity ratio and affinity difference between co2 and ch4 for low mature coals

evaluation of geological features for deep coalbed methane reservoirs in the dacheng salient jizhong depression china abstract the dacheng salient of the northeast jizhong depression is one of the most promising areas for deep coalbed methane cbm development in china this work investigates the permo carboniferous c p taiyuan and shanxi formation coals and cbm geology and gas accumulation characteristics in the dacheng salient based on field data from 24 wells and laboratory measurements of eight coal samples and eight mudstone and sandstones from exploration well d1 1 the results show that the coal rank in the dacheng salient is a high volatile c bituminous coal to low volatile bituminous coal 0 54 1 85 r o controlled by the magmatism in the region the coals vary from 2 94 to 8 58 in porosity and 0 263 m 2 g to 2 6 m 2 g in bet surface area the in situ permeability is low normally less than 0 5 10 3 m 2 methane isothermal adsorption measurements of five coal samples reveal that their maximum adsorption capacity on an as received basis varies from 17 13 to 25 98 m 3 t with an apparent relationship with ash yield the roof and floor of coal seams are mainly mudstone with minor quantities of sandy mudstone and carbonate all have the ability to be suitable cap rocks with adequate sealing capacity and large breakthrough pressure the in place gas content range from 10 23 to 1 41 m 3 t with a decreasing trend from no 3 to no 6 coal seam group in the d1 1 well due to effects by the active ground water near the east jinghai dacheng fault however the gas content and the gas saturation increase with burial depth and ground water salinity and decrease with coal rank finally based on a comprehensive analysis of coal thickness gas content hydrogeology conditions roof floor and depth properties this study reveals that the best prospective target areas for cbm production are the south central parts of the dacheng salient at1200 1600 m in depth

influence of lamprophyre sills on coal metamorphism coalbed gas composition and coalbed gas occurrence in the tongxin minefield datong coalfield china abstract magmatic intrusions in coal bearing strata can significantly change the physical and chemical properties of the intruded coal lamprophyre intrusions are extensive in coal seams 3 5 and 8 of the carboniferous permian coal bearing strata in the southeastern and southwestern regions of the tongxin minefield datong coalfield china they appear primarily as sills of varying magnitudes with thicknesses ranging from 0 15 to 23 51 m in this area coals can be classified as unaffected normal geothermal gradient and intrusion affected unaffected coals are of high volatile bituminous rank with values of maximum vitrinite reflectance ranging from 0 7 to 0 9 whereas intrusion affected coals have values of maximum vitrinite reflectance ranging from 0 9 to 7 2 a marked decrease in the degree of coalification can be observed with increasing distance from the lamprophyre intrusions near the intrusion coal contacts high volatile bituminous coals have been thermally altered to form natural coke the carbonate contents in intrusion affected coals 0 2 46 1 are significantly higher than those of the unaffected coal 0 2 0 the coalbed gases of coal seams 3 5 and 8 are highly variable in both their molecular compositions and overall gas contents their co2 volumes vary from 0 01 to 6 55 m3 t daf higher co2 values are found in the coals affected by intrusions and roughly decrease with increasing distance from the lamprophyre igneous intrusions toward the central region of the minefield these variations in gas compositions are mainly related to magmatic activity the coalbed gas contents in coal seams 3 5 and 8 range from 1 48 to 16 43 m3 t on a dry ash free basis the positive correlation observed between gas content and the ratio of co2 ch4 co2 occurs only in intrusion affected coals lamprophyre intrusions have negative effects on ch4 content in the study area since co2 has a higher adsorption capacity than ch4 c2h6 and n2 the injection of gaseous co2 derived from magmatic intrusions can effectively displace ch4 rich reservoir gas in addition there is a positive correlation between ash content and gas content on a dry ash free basis ash content is positively correlated with the ratio of co2 ch4 co2 occurring only in intrusion affected coals massive secondary carbonates that filled in the cleats act as small scale impermeable seals which provide a sealing effect both on gas contents and gas compositions during uplift

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

evidence of fluid seepage in gronfjorden spitsbergen implications from an integrated acoustic study of seafloor morphology marine sediments and tectonics abstract this study integrates high resolution surface and sub surface geophysical data to investigate possible fluid gas and or liquids migration pathways to the seafloor in gronfjorden west spitsbergen gronfjorden is an n s aligned tributary fjord located in the western part of the isfjorden fjord system pockmarks were identified on the bathymetric data in the southern and northern parts of the fjord three types of shallow seep related acoustic features have been identified in the marine sediments i enhanced reflections ii acoustic turbid zones and iii acoustic blankings they occur beneath some of the pockmarks and circular patches of high backscatter on the seafloor in the central part of the fjord which are potential seep related seafloor features 6 8 km long nnw sse striking ridges have been identified in the southern part of the study area thrust faults were interpreted on 2d multichannel seismic data truncating the triassic jurassic and cretaceous successions of western isfjorden located north of gronfjorden a possible link has been found between these fault systems and the seafloor ridges which strike in a similar direction further a normal fault has been identified within the shallow marine sediments which drapes the bedrock of the fjord the fractured bedrock of the fjord and faults associated with the west spitsbergen fold and thrust belt could possibly represent major conduits for fluid migration from deeper stratigraphy to shallow marine sediments and the seafloor

accumulation of coal bed methane in the south west part of the upper silesian coal basin southern poland abstract the archives of the polish geological institute house a wealth of coal bed methane cbm data from surface boreholes and excavations in coal from the deposits of the upper silesian coal basin uscb these data support a model for the origin of substantial methane accumulations in the south west part of the basin that reflects the interplay of the factors controlling methane sorption capacity and those controlling methane content the factors controlling the sorption capacity of coal include coal rank temperature pressure moisture content and maceral composition methane content controls include lithology stratigraphy tectonics hydrogeology and mining activity the nature of the coal bearing carboniferous horizons the sorption desorption properties of the coals the disposition of faults and folds the topography of the carboniferous palaeosurface and the presence of an impermeable miocene cover were key controls the methane accumulated in coal seams and in their host rocks in settings comparable with those in which petroleum and gas deposits are trapped

preliminary evaluation of the coalbed methane production potential and its geological controls in the weibei coalfield southeastern ordos basin china article i nfo the coalbed methane cbm geology resource and production potential in the weibei coalfield southeastern ordos basin are studied based on geological surveys and laboratory measurements the results showed that coal rank varies both laterally and vertically and changes from volatile bituminous coals in the margin to anthracites towards the basin 1 6 2 5 ro coals are composed of 60 85 vitrinite 15 40 inertinite and a trace amount of minerals methane isothermal adsorption measurements of 20 coal samples revealed that the maximum adsorption capacity on a dry and ash free basis of coals which are affected by coal rank coal maceral coal lithotype and especially to the moisture content varies from 13 91 to 29 54 m 3 t estimated gas contents range from 0 to 15 m

cleats and their relation to geologic lineaments and coalbed methane potential in pennsylvanian coals in indiana abstract cleats and fractures in pennsylvanian coals in southwestern indiana were described statistically analyzed and subsequently interpreted in terms of their origin relation to geologic lineaments and significance for coal permeability and coalbed gas generation and storage these cleats can be interpreted as the result of superimposed endogenic and exogenic processes endogenic processes are associated with coalification i e matrix dehydration and shrinkage while exogenic processes are mainly associated with larger scale phenomena such as tectonic stress at least two distinct generations of cleats were identified on the basis of field reconnaissance and microscopic study a first generation of cleats that developed early on during coalification and a second generation that cuts through the previous one at an angle that mimics the orientation of the present day stress field the observed parallelism between early formed cleats and mapped lineaments suggests a well established tectonic control during early cleat formation authigenic minerals filling early cleats represent the vestiges of once open hydrologic regimes the second generation of cleats is characterized by less prominent features i e smaller apertures with a much less pronounced occurrence of authigenic mineralization our findings suggest a multistage development of cleats that resulted from tectonic stress regimes that changed orientation during coalification and basin evolution the coals studied are characterized by a macrocleat distribution similar to that of well developed coalbed methane basins e g black warrior basin alabama scatter plots and regression analyses of meso and microcleats reveal a power law distribution between spacing and cleat aperture the same distribution was observed for fractures at microscopic scale our observations suggest that microcleats enhance permeability by providing additional paths for migration of gas out of the coal matrix in addition to providing access for methanogenic bacteria the abundance distribution and orientation of cleats control coal fabric and are crucial features in all stages of coalbed gas operations i e exploration and production understanding coal fabric is important for coal gas exploration as it may be related to groundwater migration and the occurrence of methanogenic bacteria prerequisite to biogenic gas accumulations likewise the distribution of cleats in coal also determines pathways for migration and accumulation of thermogenic gas generated during coalification

variable gas saturation in coalbed methane reservoirs of the black warrior basin implications for exploration and production abstract gas saturation is highly variable in carboniferous coalbed methane reservoirs of the black warrior basin usa and diverse geologic data derived from more than three decades of exploration and development provides insight into the origin of this variability and the consequences for production performance coalbed methane is produced from numerous thin 0 3 to 95 importantly this range of variation is commonly developed among closely spaced seams within the same well exploration has to date been successful where coal seams are in the thermogenic gas window geochemical evidence indicates that thermogenic gases have been altered by subsurface water movement and may have been augmented with late stage biogenic gases particularly in areas affected by fresh water recharge adsorption isotherms of coal samples in the black warrior basin typically have langmuir volume between 15 and 30 cm3 g and langmuir pressure between 2 and 6 mpa both langmuir pressure and langmuir volume correlate significantly with coal rank in deep normally pressured coal beds where reservoir pressure is substantially above langmuir pressure even a small degree of undersaturation can necessitate prolonged dewatering before a large reservoir volume can reach the critical desorption pressure permeability moreover decreases exponentially with depth which can make dewatering coal seams deeper than 800 m difficult where reservoir pressure is relatively low however isotherm geometry indicates that significantly undersaturated reservoirs can be near the critical desorption pressure consequently areas of underpressure favor high gas production along with minimal water production

evaluation of coalbed gas potential of the seelyville coal member indiana usa abstract the seelyville coal member of the linton formation in indiana potentially contains 0 03 trillion m3 1 1 tcf of coalbed gas the gas content determined by canister desorption technique ranges from 0 5 to 5 7 cm3 g on dry ash free basis 15 4 to 182 2 scf ton the controls on gas content distribution are complex and cannot be explained by the coal rank alone ash content and the lithology of the overlying strata among other factors may influence this distribution

the upper paleozoic coalbed methane system in the qinshui basin china the coalbed methane resource is very abundant in qinshui basin 3 28 1012 m3 114 tcf the investigation on the upper paleozoic coalbed methane system is a guide to the exploration and development of coalbed methane the upper paleozoic coalbed methane system in the qinshui basin is sealed by a low permeability roof and floor strata comprising mudstone siltstone and bauxite of the carboniferous benxi formation and the permian shanxi and xiashihezi formations the overburden is the lower permian xiashihezi formation and the upper permian triassic and middle jurassic clastic deposits the source and reservoir rocks are the carboniferous permian coal seams the hydrocarbon generation of the source rocks reached its first peak in the late triassic the highest maturity was about ro 1 2 under a normal paleogeothermal gradient 2 3c 100 m 1 1 1 7f 100 ft a tectonic thermal event during the jurassic and cretaceous yanshanian orogeny enhanced the coal maturity and caused a second peak of hydrocarbon generation varying igneous intrusions caused the coal maturity to be higher in the southern northern and eastern parts of the qinshui basin instead of the central and western parts the highest maturity was greater than ro 4 in the jincheng area the migrated thermogenetic coalbed methane accumulated in the reservoirs in which abnormally high reservoir pressure exists locally under the hydrodynamic drive because of the different hydrodynamic background and sealing condition the distribution of coalbed methane content is inhomogeneous the reservoir is undersaturated with gas in most areas based on the coalbed methane system investigation we assessed the coalbed methane producibility in different parts of the qinshui basin and the major producibility area is in the southern part of the basin

geological controls on variable gas concentrations a case study of the northern gujiao block northwestern qinshui basin china abstract a systematic investigation was performed on the variation of gas content and its geological controls based on the diverse geological data and the experimental results of 72 coal samples from 24 coalbed methane cbm wells in the northern gujiao block nw qinshui basin china coal rank varies from low volatile bituminous coal to medium volatile bituminous coal with maximum vitrinite reflectance ro max ranging from 1 21 to 1 92 cbm in the northern gujiao block is mainly produced from the relatively thick coal seams 1 0 m 7 0 m which are distributed in the upper carboniferous taiyuan formation and lower permian shanxi formation the total gas content of coal seams ranges from 3 83 to 16 82 m3 t with increasing gas content from marginal to central areas highly variable gas content reflects the comprehensive effect of various geological factors and coal reservoir properties the results of the study show that the structural types roof lithology burial depth and hydrodynamic conditions are key factors controlling the gas content whereas coal thickness and coal properties have no or little correlation with the gas content in the northern gujiao block three geological features controlling gas content are identified 1 hydrodynamic trapping of gas in the graben structure with an adequate burial depth and impermeable roof 2 gas loss by hydrodynamic flushing and normal faults in the syncline structure and 3 gas migration by intensive movement of groundwater in the shallow burial area the first mechanism is considered to cause the high gas content of central study area whereas the other two mechanisms can explain the low gas content in the north western and south eastern regions

stable isotope and water quality analysis of coal bed methane production waters and gases from the bowen basin australia abstract coal bed methane cbm is a significant growing industry in queensland s energy sector it is however a relatively new industry with little local water quality data and stable isotope compositions of production waters and gases available in the public domain this study aims to determine whether water quality and stable isotope data can be correlated with gas and groundwater production and flow pathways and identify zones of recharge and water mixing stable isotope analysis and accessory water quality tests were conducted on cbm production gas and water samples collected from two cbm producing bituminous coal seams within a single field in the bowen basin in the production field the reservoir seams are gently folded with eastwardly dipping fold axes and compartmentalised by an ene normal fault on the flank of a broad central anticline that contains minor faults for one seam splitting and a change in coal quality parallels the fault and fold axes although virgin reservoir conditions were similar differing production performance north and south of the main fault suggests it acts as a barrier to water and gas flow along strike the stable isotope analysis on the production water showed that waters with more positive d and 18o compositions were associated with areas of higher water production and shallower depths whereas more negative d and 18o compositions were associated with lower water production and high gas production the gas isotope analysis showed that production gases had both biogenic and thermogenic origins and that secondary biogenic gas generated through co2 reduction comprises a significant portion of the cbm produced from this field more negative ch4 13c values characterize the zones of meteoric recharge in shallow up dip areas gas production data and co2 13c values suggest that this may result from 13ch4 stripping by the recharge waters and or increased biogenic activity in this area smaller co2 ch4 carbon isotopic fractionation values characterized zones of meteoric recharge whereas higher isotopic fractionation values characterized the high gas production domain

intracrustal detachment within zones of continental deformation geologic mapping of active to recently active geologic structures in panamint valley western united states and in the haiyuan region and northern tibetan plateau china suggests detachment in the middle and lower crust on a scale of tens of kilometres to at least several hundred kilometres detachment occurs similarly in predominantly extensional panamint valley and in predominantly compressional china environments it involves structures with displacements of more than 10 km and displacement rates of more than 3 mm yr perhaps more than 10 mm yr the steeply dipping strike slip faults present in all three areas hunter mountain fault haiyuan fault and altyn tagh fault zone terminate in zones of extension or compression and geometric relations indicate that all structures including strike slip faults are thin skinned and restricted to the upper crust in panamint valley and in the haiyuan region deformation within these systems can be reconstructed in three dimensions displacement on the strike slip faults is absorbed by extension or compression occurring at the termination of the faults so strike slip displacement is roughly equal to and in the same direction as shortening or extension we propose that left slip on the altyn tagh fault zone in northern tibet is similarly absorbed by shortening southeast of the fault zone within the qaidam basin and the nan shan

image processing based characterisation of coal cleat networks abstract characterisation of the cleat network serves as the basis for estimating the hydraulic and mechanical seam properties which in turn are fundamental for flow and geomechanical modelling in the context of underground coal mining cleat and cleat network geometry can be described as a function of frequency aperture size orientation relative to in situ stresses connectivity and porosity with mineralised and un mineralised cleats occurring to describe these properties ct scans of core samples of a bowen basin coal in central queensland australia are analysed a unique image processing workflow method is introduced to extract the key statistical parameters of perpendicular butt and face cleats present in a two dimensional image as face and butt cleats have different characteristics the presented method distinguishes face cleats and butt cleats by direction and present detailed data for both cleat types the results comprise cleat length apertures sizes intensities densities shape parameter spacing orientation and connectivity and are therefore more comprehensive than previous cleat descriptions three generally different cleat geometries are considered within this study one sample shows perpendicular face and butt cleats the second two sets of face cleats intersected by butt cleats and the third parallel face cleats only

paired deformation sources of the campi flegrei caldera italy required by recent 1980 2010 deformation history we analyze 1980 2010 ground displacements to discern similarities or differences between campi flegrei cf inflations and deflations and highlight possible anomalies in particular areas we show that the deformation pattern can be decomposed into two stationary constant over time except for a mere scaling factor parts both of them are satisfied by simple deformation sources a quasi horizontal elongated crack oriented nw to se and embedded in an elastic layered half space at a depth of about 3600 m satisfies large scale deformation all source parameters but potency volume change are constant over time residual deformation is confined to the area of the solfatara fumarolic field and satisfied by a small spheroid located at about 1900 m in depth again all source parameters but potency are constant over time the histories of the two sources are somewhat similar but not equal supporting the existence of a genuine local deformation source at solfatara against the emergence of a mere distortion of large scale deformation although reality is probably much more complex our simple model explains 1980 2010 cf deformation within ground displacement data errors and is consistent with solfatara geochemical conceptual models fumarolic geochemical data and seismic attenuation imaging of cf the observation that the cf deformation pattern can be decomposed into two stationary parts is hardly compatible with several recent works which proposed multiple sources with different features acting in different periods fluid injections implying ample changes of large scale deformation pattern over time complex spatio temporal patterns of distributions of volumetric sources

shale gas desorption behavior and carbon isotopic variations of gases from canister desorption of two sets of gas shales in south china abstract four shale samples from the lower silurian longmaxi formation and the lower cambrian shuijingtuo formation in the eastern part of chongqing sw china were subjected to canister desorption experiments at reservoir and elevated temperatures up to 90 c to investigate shale gas release behaviors and their variations in chemical and isotopic compositions of desorbed gases both the ratios of gas released at reservoir temperature to the total desorbed gas at reservoir and elevated temperatures and the desorption rates suggest that the longmaxi shale gas is more easily released than the shuijingtuo shale gas scanning electron microscope sem observation along with low temperature co2 and n2 adsorption results suggests that organic matter hosted pores with diameters of 2 100 nm are rich in the longmaxi shales whereas well developed micropores