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

geologic controls on transgressive regressive cycles in the upper pictured cliffs sandstone and coal geometry in the lower fruitland formation northern san juan basin new mexico and colorado three upper pictured cliffs sandstone tongues in the northern part of the san juan basin record high frequency transgressive episodes during the late cretaceous and are inferred to have been caused by eustatic sea level rise coincident with differential subsidence outcrop and subsurface studies show that each tongue is an amalgamated barrier strand plain unit up to 100 ft 30 m thick successive upper pictured cliffs tongues display an imbricate relation and are offset basinward reflecting net shoreline progradation northeastward upper pictured cliffs barrier strand plain sandstones underlie and bound thickest fruitland coal seams on the seaward side controls on fruitland coal seam thickness and continuity are a function of local facies distribution in a coastal plain setting shoreline positions related to transgressive regressive cycles and basin subsidence during periods of relative sea level rise the pictured cliffs shoreline was temporarily stabilized allowing thick coastal plain peats to accumulate although some coal seams in the lower fruitland tongue override abandoned pictured cliffs shoreline deposits many pinch out against them differences in the degree of continuity of these coal seams relative to coeval shoreline sandstones are attributed to either differential subsidence in the northern part of the basin multiple episodes of sea level rise local variations in accommodation and progradation stabilization of the shoreline by aggrading peat deposits or a combination of these factors fruitland coalbed methane resources and productivity are partly controlled by coal seam thickness other important factors include thermal maturity fracturing and overpressuring the dominant production trend occurs in the northern part of the basin and is oriented northwestward coinciding with the greatest fruitland net coal thickness similar relationships between trends of thick coal seams of coeval origin with stacked shoreface sandstones exist in other western interior basins in the united states and serve as models for coalbed methane exploration in other basins of the world

coalbed gas systems resources and production and a review of contrasting cases from the san juan and powder river basins coalbed gas has been produced commercially from the northern appalachian basin since the 1930s and from the san juan basin since the early 1950s however the magnitude and economic sig nificance of coalbed gas resources were realized only in the 1970s and early 1980s when the u s bureau of mines u s department of energy the gas research institute and oil and gas operators made a concerted effort to demonstrate commercial production of coalbed gas from vertical wells exploration and development ex panded in the late 1980s and early 1990s due partly to an uncon ventional fuels tax credit by 2000 coalbed gas accounted for 8 8 of the reserves 15 7 tcf 0 44 tm3 and 9 2 of the annual pro duction 1 38 tcf 40 gm3 of dry gas in the united states from 1989 through 2000 cumulative united states coalbed gas produc tion was 9 63 tcf 272 gm3 today coalbed gas development has spread to about a dozen basins in the united states and exploration is progressing worldwide coal beds are self sourcing reservoirs that can contain ther mogenic migrated thermogenic biogenic or mixed gas coalbed gas is stored primarily within micropores of the coal matrix in an adsorbed state and secondarily in micropores and fractures as free gas or solution gas in water the key parameters that control gas resources and producibility are thermal maturity maceral compo sition gas content coal thickness fracture density in situ stress permeability burial history and hydrologic setting these param eters vary greatly in the producing fields of the united states and the world in 2000 the san juan basin accounted for more than 80 of the united states coalbed gas production this basin contains a gi ant coalbed gas play the fruitland fairway which has produced more than 7 tcf 0 2 tm3 of gas the fruitland coalbed gas system and its key elements contrast with the fort union coalbed gas play in the powder river basin the fort union coalbed play is one of the fastest developing gas plays in the united states its production escalated from 14 bcf 0 4 gm3 in 1997 to 147 3 bcf 4 1 gm3 in 2000 when it accounted for 10 7 of the united states coalbed gas production by 2001 annual production was 244 7 bcf 6 9 gm3 differences between the fruitland and fort union petroleum systems make them ideal for elucidating the key elements of contrasting coalbed gas petroleum systems

hydrochemistry and isotopic composition of na hco3 rich groundwaters from the ballimore region central new south wales australia abstract groundwaters flowing under artesian pressure from the ballimore region central new south wales australia contain up to 95 na hco3 carbon dioxide effervesces from these groundwaters as they discharge from boreholes these groundwaters flow from a confined aquifer situated within fractured permian to jurassic sediments regional geological data and k ar dating of outcropping volcanic units indicate that magmatism occurred in this area between 12 and 14 ma ago radiometric and magnetic data supports the interpreted presence of intrusive bodies x ray fluorescence xrf data shows that the miocene magmatic units are sodium rich with the available samples being classified as either syenitic or trachytic hydrochemical and isotopic data indicate that these groundwaters are of meteoric origin and that this system is open with respect to co2 there is an external source of co2 feeding this groundwater system causing dic total alk the salinity of the na hco3 rich groundwaters range from 3000 to 8000 mg l and co2 aq concentrations are up to 1558 mg l log pco2 of 0 6 the ph of these samples range from 6 1 to 6 9 supporting the conclusion that the h2co3 hco3 couple control ph buffering the carbon 13 values 13c pdb of 5 to 3 indicate that the carbon source for these groundwaters is of inorganic origin it is inferred that this carbon source has a primary 13c similar to that typically quoted for mantle derived carbon 5 9 varying degrees of completeness of equilibrium isotopic fractionation resulting from the hydration dissociation of co2 into the groundwater forming hco3 co2 h2co3 hco3 leads to the observed range of carbon 13 data oxygen 18 18o smow and deuterium d smow isotopic data show a shift to the left of the meteoric water line supporting an interpretation of co2 exsolution gas exchange and fractionation resulting from incongruent silicate weathering reactions dissolved inorganic carbon carbon 13 and regional geological data suggest that the most plausible explanation for the high concentration of co2 in these effervescent sodium bicarbonate rich groundwaters is the mantle with this gas initially being delivered to the fractured strata by magmatic activity

evaluation of the reservoir permeability of anthracite coals by geophysical logging data article i nfo permeability is one of the most significant reservoir parameters it is commonly obtained by experiment history simulation injection falloff well test and geophysical logging among these geophysical logging remains as the most economic and efficient technique in evaluating coal permeability in the vicinity of an open hole in this paper geophysical logging data are used to evaluate the coal reservoir permeability for the no 3 coal seam in the southern qinshui basin fanzhuang and zhengzhuang coal zones ideally coal reservoirs consist of coal matrix and fracture networks that can be represented by a model called a collection of sheets based on the model coal reservoir permeability can be quantitatively calculated using the theoretical formula ofkf 8 50 10 4 w 2 f in which fracture width w and fracture porosity f were obtained by dual laterolog and density logging data respectively calculative results show that coal reservoir permeability ranged from 0 017 md to 0 617 md for the fanzhuang coal zone and from 0 047 md to 1 337 md for the zhengzhuang coal zone the permeability decreases with coal burial depth reflecting variations in penetration capability of coal reservoirs at varying depths comparing results with those from injection falloff well tests however shows that the model calculated permeability is slightly higher this is expected because the model did not include the influence from coal anisotropy

structural control of coalbed methane production in alabama abstract thin skinned structures are distributed throughout the alabama coalbed methane fields and these structures affect the production of gas and water from coal bearing strata extensional structures in deerlick creek and cedar cove fields include normal faults and hanging wall rollovers and area balancing indicates that these structures are detached in the pottsville formation compressional folds in gurnee and oak grove fields by comparison are interpreted to be detachment folds formed above decollements at different stratigraphic levels patterns of gas and water production reflect the structural style of each field and further indicate that folding and faulting have affected the distribution of permeability and the overall success of coalbed methane operations area balancing can be an effective way to characterize coalbed methane reservoirs in structurally complex regions because it constrains structural geometry and can be used to determine the distribution of layer parallel strain comparison of calculated requisite strain and borehole expansion data from calliper logs suggests that strain in coalbed methane reservoirs is predictable and can be expressed as fracturing and small scale faulting however refined methodology is needed to analyze heterogeneous strain distributions in discrete bed segments understanding temporal variation of production patterns in areas where gas and water production are influenced by map scale structure will further facilitate effective management of coalbed methane fields

enrichment origin of critical elements li and rare earth elements and a mo u se re assemblage in pennsylvanian anthracite from the jincheng coalfield southeastern qinshui basin northern china abstract the qinshui basin is the largest reservoir of commercial coalbed methane in china the no 15 seam one of the major coal seams for coalbed methane exploration in the jincheng coalfield se qinshui basin has recently been found to be enriched in the critical element li this study further investigates the inorganic geochemistry of the no 15 coal and associated rocks and reveals the enrichment origin of critical elements in these horizons the jincheng no 15 coal is rich in li mo u se re and rare earth elements and y rey concentrations of mo u se and re are higher in the two topmost coal benches probably due to marine transgression in the early diagenetic stage after the peat had been established the enrichment of li and rey in a few lowermost coal benches is suggested to be derived from hydrothermal fluids that were related to magmatic activity 110 140 ma during the yanshanian orogeny late jurassic early cretaceous or a late triassic early jurassic abnormal thermal event occurring at 190 215 ma light rey la ce pr and nd in the jincheng no 15 coal are predominantly associated with phosphate minerals heavier rey sm to lu show a mixed phosphate and organic affinity in the studied coal samples non coal samples are characterized by light rey and hrey enrichment which is probably inherited from the source material in the trans north china orogen trace elements in the coal can be highly enriched in the ash if the coal is combusted due to the low to medium ash yield of the coal critical elements including li ga and rey in the jincheng no 15 coal are considered as promising material for industrial recovery and have been previously under estimated on the other hand environmentally sensitive elements including as hg and pb while having concentrations within the normal range compared with average worldwide coals can be highly enriched in the coal combustion residues if the coal is combusted and thus careful consideration needs to be given to the utilisation of such coals

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

chemical and stable isotopic evidence for water rock interaction and biogenic origin of coalbed methane fort union formation powder river basin wyoming and montana u s a significant amounts 36 million m3 day of coalbed methane cbm are currently being extracted from coal beds in the paleocene fort union formation of the powder river basin of wyoming and montana information on processes that generate methane in these coalbed reservoirs is important for developing methods that will stimulate additional production the chemical and isotopic compositions of gas and ground water from cbm wells throughout the basin reflect generation processes as well as those that affect water rock interaction our study included analyses of water samples collected from 228 cbm wells major cations and anions were measured for all samples dh2o and 18oh2o were measured for 199 of the samples and dch4 of gas co produced with water was measured for 100 of the samples results show that 1 water from fort union formation coal beds is exclusively na hco3 type water with low dissolved so4 content median 1 mg l and little or no dissolved oxygen 0 15 mg l whereas shallow groundwater depth generally 120 m is a mixed ca mg na so4 hco3 type 2 water rock interactions such as cation exchange on clay minerals and precipitation dissolution of caco3 and so4 minerals account for the accumulation of dissolved na and depletion of ca and mg 3 bacterially mediated oxidation reduction reactions account for high hco3 270 3310 mg l and low so4 median 0 15 mg l values 4 fractionation between dch4 283 to 328 per mil and dh2o 121 to 167 per mil indicates that the production of methane is primarily by biogenic co2 reduction and 5 values of dh2o and 18oh2o 16 to 22 per mil have a wide range of values and plot near or above the global meteoric water line indicating that the original meteoric water has been influenced by methanogenesis and by being mixed with surface and shallow groundwater

constraining coalbed methane reservoir petrophysical and mechanical properties through a new coal structure index in the southern qinshui basin northern china implications for hydraulic fracturing structurally deformed coal sdc influences not only gas outbursts during coal mining but also coalbed methane cbm production different sdcs have different mechanical strengths and physical properties the structurally constrained petrophysical and mechanical properties of a cbm reservoir from the southern qinshui basin sqb northern china have been investigated by using a coal structure index csi the csi was established as a quantitative criterion for the deformation of sdcs based on surface conditions and blockiness using the data of 783 coring samples from 109 cbm wells the results show that undeformed coal and slight brittle sdcs are dominant in the sqb with ductile sdcs distributed locally both compressive strength and tensile strength decline exponentially with increasing csi average avg coal structure is a crucial factor for coal seam fracturing with an increasing csi avg the major fracture length will first increase to the maximum of 266 m at a csi avg of 45 and then decrease rapidly however branch fractures are independent of the csi avg the major fracture height attained a minimum of 4 39 m at a csi avg of 40 and then slowly increased therefore slightly brittle sdcs should be beneficial for fracturing at least for high rank coals the presence of variable sdcs can have a considerable impact on cbm reservoir petrophysical and mechanical properties finally a csi model that strives to establish the relation between structure deformation and cbm reservoir physical and mechanical properties in coal is expected to effectively guide hydraulic fracturing

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

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

stable isotopic and molecular composition of desorbed coal seam gases from the walloon subgroup eastern surat basin australia this study used compositional and stable isotopic analysis to test hypotheses on the distribution and origins of walloon subgroup coal seam gas csg in the eastern surat basin queensland australia the middle jurassic walloon subgroup play differs from many other low rank csg plays particularly in methane carbon isotopic signature i e the csg is not as microbial as could be expected the carbon isotope compositions of desorbed methane from three cored appraisal wells fall within the generally accepted range for thermogenic or mixed gas 13c 58 5 to 45 3 the 13c ch4 values from stratigraphically placed coal core samples increased became more thermogenic from the top of the upper juandah coal measures to the base of the tangalooma sandstone below the tangalooma sandstone in the lower taroom coal measures the 13c ch4 values decreased with increasing depth these positively parabolic 13c profiles tracked total measured gas content in two out of the three wells studied the third well displayed lower variance of 13c ch4 and gas content increased uniformly with depth a genetic classification based on methane stable carbon isotopes alone might interpret this pattern as a transition from microbially to thermogenically sourced methane in the central coal seams however a 13c co2 profile for one well tracks total gas content and 13c ch4 and exhibits an inverse relationship with d ch4 these results together with the mostly dry nature of the gas samples c1 c2 c3 ratios up to 10 000 and relatively uniform d ch4 values d 238 to 202 suggest that microbial co2 reduction is the primary source of walloon subgroup methane as such stratigraphic variations in gas content mainly reflect the extent of microbial methanogenesis we suggest that peak microbial utilisation of h2 co2 occurred at the tangalooma sandstone level enriching the residual co2 pool and derived methane in 13c carbon 13c co2 ch4 and deuterium isotopic differences d h2o ch4 and cross plots of d h2o and 18o h2o are also consistent with kinetic isotope fractionation during microbial mediated carbonate reduction the results are relevant for applying microbially enhanced coal bed methane mecom in the surat 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

analysis of environmental controls on tsunami deposit texture abstract tsunamis transport large amounts of sediment and can leave recognisable signatures in the landscape the form and composition of onshore tsunami deposits are a function of wave dynamics sediment availability and characteristics of the local environment the latter of which also partially controls preservation of the deposit this research reviews these relationships in a global context and assesses the connection between tsunami deposit particle size and four controlling parameters climate temperature and rainfall density of tsunami sediments degree of coastal protection and distance between tsunami source and sediment deposition an international dataset of tsunami deposit locations and texture was compiled from published literature and existing databases values for environmental variables were calculated for each location from global datasets of temperature rainfall coastline shape and tsunami source locations spearman s rank order correlation principal component analysis pca and hierarchical cluster analysis ca were used to analyse relationships between these variables pca results show an inverse relationship between particle size and sediment density climate variables and distance from source ca results support this suggesting a cluster structure controlled primarily by particle size and secondly by climate and sediment density these relationships can be explained by the influence of the environment on antecedent morphology and the composition of sediments available for tsunami transport

the occurrence and origin of methane in some groundwater flow systems the origin of methane in selected groundwater flow systems is investigated through carbon isotope geochemical studies combined with hydrogeological and hydrogeochemical information methane is a common trace constituent in these groundwaters and occasionally constitutes a major carbon pool two modes of origin for methane are commonly recognized microbial production biogenic methane and non biological chemical production thermocatalytic methane in the groundwaters sampled the few thermocatalytic methanes encountered have 13c values greater than about 45 whereas the more common normal biogenic methanes have 13c values less than about 60 biogenic methanes from sanitary landfill sites have intermediate 13c values of about 38 to 56 and so can easily be distinguished from normal biogenic methane the carbon source for biogenic methane is usually organic matter present in the aquifer materials the carbon isotope ratios of dissolved methane and total inorganic carbon in sampled groundwaters ar

geochemical signature of formation waters associated with coalbed methane formation waters associated with coalbed methane have a common chemical character that can be an exploration tool regardless of formation lithology or age effectively devoid of sulfate calcium and magnesium the waters contain primarily sodium and bicarbonate and where influenced by water of marine association also contain chloride the distinct geochemical signature evolves through the processes of biochemical reduction of sulfate enrichment of bicarbonate and precipitation of calcium and magnesium cation exchange with clays may also deplete the dissolved calcium and magnesium but is not prerequisite low sulfate bicarbonate ratios characterize these waters and are also common but less pronounced with occurrences of conventional oil and gas waters rich in sulfate calcium and magnesium occur in many coalbed aquifers but are not found in association with methane users of total dissolved solids data should ensure that the values reflect adjustments of bicarbonate concentrations to simulate evaporation residues results that erroneously sum the entire bicarbonate content can be far too high in these bicarbonate rich waters thereby exacerbating the issues of disposal evaluations of prospects and choices of exploration targets can be enhanced by an added focus on the geochemical signature that should be expected in association with methane knowledge of the geochemical signature may also be useful in the commonly protracted testing of wells the appearance of high sulfate concentrations in water analyses can justify early curtailment of test pumping and can prompt the siting of subsequent drill holes farther from areas of recharge

analyses of geological and hydrodynamic controls on methane emissions experienced in a lower kittanning coal mine this paper presents a study assessing potential factors and migration paths of methane emissions experienced in a room and pillar mine in lower kittanning coal indiana county pennsylvania methane emissions were not excessive at idle mining areas but significant methane was measured during coal mining and loading although methane concentrations in the mine did not exceed 1 limit during operation due to the presence of adequate dilution airflow the source of methane and its migration into the mine was still a concern in the course of this study structural and depositional properties of the area were evaluated to assess complexity and sealing capacity of roof rocks composition gas content and permeability of lower kittanning coal results of flotation tests and geochemistry of groundwater obtained from observation boreholes were studied to understand the properties of coal and potential effects of old abandoned mines within the same area these data were combined with the data obtained from exploration boreholes such as depths elevations thicknesses ash content and heat value of coal univariate statistical and principal component analyses pca as well as geostatistical simulations and co simulations were performed on various spatial attributes to reveal interrelationships and to establish area wide distributions these studies helped in analyzing groundwater quality and determining gas in place gip of the lower kittanning seam furthermore groundwater level and head on the lower kittanning coal were modeled and flow gradients within the study area were examined modeling results were interpreted with the structural geology of the allegheny group of formations above the lower kittanning coal to understand the potential source of gas and its migration paths analyses suggested that the source of methane was likely the overlying seams such as the middle and upper kittanning coals and freeport seams of the allegheny group simulated ground water water elevations gradients of groundwater flow and the presence of recharge and discharge locations at very close proximity to the mine indicated that methane likely was carried with groundwater towards the mine entries existing fractures within the overlying strata and their orientation due to the geologic conditions of the area and activation of slickensides between shale and sandstones due to differential compaction during mining were interpreted as the potential flow paths

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

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

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

exotic stable isotope compositions of saline waters and brines from the crystalline basement the overwhelming majority of groundwaters reported in literature show isotopic compositions that place them on or right of the meteoric water line mwl in a 2h vs 18o diagram a closer look to the steadily increasing data from the deeper crystalline basement reveals nevertheless that points left of the mwl are not so unusual as has been suggested during the last decades their supposed rareness seems to be due to a bias of sampling the concerned fluids develop only at greater depths and in low permeability environments which makes access to them so difficult paradoxically exotic stable isotope compositions may be the rule in a restricted depth zone in all crystalline basements with slow groundwater movements but not too high temperatures the present study takes stable isotope data on saline fluids from the deep french granitic basement as a starting point in order to situate the french data from the vienne region in a more general context a literature review has been undertaken assembling more than 1300 stable isotope analyses of waters and brines in crystalline rocks from stable cratons and mountain belts world wide the french fluids show some particular features with respect to the majority of other studies as their major ion composition close to seawater or a significant isotopic shift at relatively low salinities detailed knowledge on the hydrological and chemical history of the site allowed to develop a conceptual model of isotopic evolution by interaction of fracture fluids with fracture minerals this model considers interactions of the last fluids flushing the system marine water unaltered evaporated or diluted with previously precipitated mineral phases and the neoformation of the last generation of fracture minerals the model has been tested quantitatively for several combinations of dissolution precipitation reactions involving formation of carbonates clay minerals and fe hydroxides most of the modelled scenarios would leave the residual liquid phase depleted in 18o and either enriched or depleted in 2h and produce waters with isotopic signatures corresponding to the observed 2h vs 18o correlation it is therefore suggested that the general phenomenon of an isotopic shift in deep fissured silicate rocks which seems to be rather independent of lithology may result from a combination of different reaction mechanisms implying not solely the rock matrix but also the different generations of fracture minerals

extreme inundation flows during the hokkaido nansei oki tsunami the tsunami generated by the july 12 1993 hokkaido nansei oki mw 7 8 earthquake produced in japan the worst local tsunami related death toll in fifty years with estimated 10 18m sec overland flow velocities and 30m runup these extreme values are the largest recorded in japan this century and are among the highest ever documented for non landslide generated tsunamis we model this event to confirm the estimated overland flow velocities and we find that given reasonable ground deformation data current state of the art shallow water wave models can predict tsunami inundation correctly including extreme runup current velocities and overland flow we find that even small local topographic structures affect the runup to first order and that the resolution of the bathymetric data is more important than the grid resolution our results qualitatively suggest that for this event coastal inundation is more correlated with inundation velocities than with inundation heights explaining also why threshold type modeling has substantially underpredicted coastal inundation for this and other recent events

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

potential vorticity budgets in the north atlantic ocean abstractthis paper focuses on potential vorticity pv budgets in the north atlantic with an emphasis on the wind driven subtropical gyre since pv is the key dynamical variable of the wind driven circulation these budgets are important to understand pv is a conservative quantity on isopycnals and can only enter or exit through the boundaries like the lateral topography or the surface the latter fluxes are diagnosed and tested against the evolution of the pv content in an isopycnal layer the former are computed using the bernoulli function the essential result is found for all the tested isopycnals and the dominant feature of pv is recirculation with very little added at the surface or the boundaries density coordinates are well suited to understanding pv circulation a novel technique for computing the bernoulli function is proposed the bernoulli function is governed by a simple elliptic equation and the solutions demonstrate the dominant contribution of pv advection

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

geological controls on prediction of coalbed methane of no 3 coal seam in southern qinshui basin north china article i nfo in order to better understand the geological controls on coalbed methane cbm in southern qinshui basin sqb north china geological surveys and laboratory experiments including coal petrology analysis proximate analysis and methane adsorption desorption were conducted results show that the coals from the sqb contain 0 59 3 54 moisture 3 5 15 54 ash yield 73 62 88 92 fixed carbon and 2 14 4 04 hydrogen with c h ratios in the range of 19 96 36 25 the vitrinite reflectance ro m ranges from 1 95 to 3 49 the coals are composed of 18 5 97 4 vitrinite and 2 4 81 4 inertinite the geologic structures coal bearing strata and coal depositional environment were studied by both field geological research and laboratory tests a positive relationship is found between cbm content and basin hydrodynamics in which cbm easily concentrates in the groundwater stagnant zone because of the water pressure furthermore integrated geographical information system gis and analytical hierarchy fuzzy prediction method ahp were used to evaluate the cbm resources in the sqb the results show that the amount of cbm associated with the no 3 coal seam in the sqb is 3 62 10 11 m 3 t he cbm resource concentration gas in place per square kilometer in the sqb is in the range of 0 72 2 88 10 8 m 3 km 2 with an average of 1 21 10 8

characteristics of natural fractures in the upper paleozoic coal bearing strata in the southern qinshui basin china implications for coalbed methane cbm development abstract natural fractures as the effective storage space and fluid flow pathway of hydrocarbons play a critical role in the exploration and development of unconventional gas resources in the coal bearing strata in the present study to reveal the effects of natural fractures on coalbed methane cbm preservation and development the types origins and development characteristics of natural fractures in the upper paleozoic permian shanxi formation in the southern qinshui basin were systematically described and analyzed based on outcrops cores borehole image logs thin sections and sem four types of natural fractures have been identified in the shanxi formation according to their geologic origins including the endogenic fractures cleats and exogenous fractures in the no 3 coal seam and tectonic fractures and diagenetic fractures in its roof and floor tectonic fractures can be further divided into small faults intraformational shear fractures intraformational open fractures and slip fractures while diagenetic fractures are mainly bed parallel fractures the statistical results show that the development and distribution characteristics of those types of fractures are significantly different which are mainly influenced by lithology layer thickness and geological structure further natural fractures with different types and distributions show different influences on cbm preservation and well productivity exogenous fractures can effectively improve the seepage capability of coal reservoirs and are conducive to cbm wells productivity whereas endogenic fractures have less contributions to coal permeability due to their poor effectiveness the intraformational open fractures in the fold axis zones and intraformational shear fractures and small faults in the fault zones are generally excessive developed those fractures may result in gas dissipation and external water supplement which have negative effects on cbm preservation and production however moderate developed intraformational shear fractures in the sandstone roof can favorably affect the pressure reduction of coal reservoir and improve the recovery potential of unconventional gas resources these investigations may serve as a geological basis for unconventional gas exploration and development of the upper paleozoic coal bearing strata in the southern qinshui basin

merging tsunamis of the 2011 tohoku oki earthquake detected over the open ocean 1 tsunamis often travel long distances without losing power and severely devastate some coastal areas while leaving others with little damage this unpredictable situation has been a major challenge for accurate and timely tsunami forecasting to facilitate early warning and possible evacuations of affected coastal communities without disturbing the lives of others here we show evidence from satellite altimetry observations of the 2011 tohoku oki earthquake induced tsunami that sheds light on this issue three satellites observed the same tsunami front and for the first time one of them recorded a tsunami height about twice as high as that of the other two model simulations based on the gps derived earthquake source and constrained by measurements of seafloor motions near the hypocenter confirm that the amplified tsunami is one of several jets formed through topographic refraction when tsunamis travel along ocean ridges and seamount chains in the pacific ocean this process caused the tsunami front to merge as it propagates resulting in the doubling of the wave height and destructive potential in certain directions we conclude that the potential of merging tsunamis should be emphasized in mapping tsunami hazards and assessing risk levels at key coastal facilities

hydrodynamic and stratigraphic controls for a large coalbed methane accumulation in ferron coals of east central utah abstract upper cretaceous coals within the ferron sandstone member of the mancos shale contain large volumes of coalbed methane coals at the northern end of the 80 mile long 129 km ferron trend have produced more than 200 billion cubic feet bcf 5663 10 6 m 3 of coalbed methane with daily production of 260 million cubic feet per day mmcfd 7 36 10 6 m 3 day from 470 wells during november 2000 core data from exploratory wells drilled along trend to the south indicate that the gas content of the coals decreases dramatically from north to south even though the rank and maturity of the coals decreases only slightly the area with lowest gas content correlates with the outcrop of the ferron coals hydrodynamic studies have shown that the ferron coals are aquifers that are recharged from the wasatch plateau to the west regional mapping indicates that the productive fields are large stratigraphic traps where the coals pinchout updip into tight marine shales to the east much of the produced gas is secondary biogenic gas and migrated thermogenic gas that has moved from the wasatch plateau and south margin of the uinta basin respectively further south near the town of emery coals are present at the surface but most of the gas has been flushed out of the coals due to reduction of reservoir pressure and active water flow from the west therefore the entire ferron trend probably contained tremendous volumes of stratigraphically trapped coalbed methane before uplift and erosion exposed the southern coals to the atmosphere

possible controls of hydrogeological and stress regimes on the producibility of coalbed methane in upper cretaceous tertiary strata of the alberta basin canada the coalbed methane potential and producibility of any coal bearing strata are strongly affected by the hydrogeological regime of formation waters and by coal permeability which in turn depends on the effective stress regime of the coals peat that accumulated in the alberta basin during the late cretaceous and early tertiary led to the formation of coal deposits that may contain significant coalbed methane resources the flow of formation waters plays an important role in the maintenance and producibility of this resource the present day flow is driven by gravity topography and erosional rebound and is controlled by rock permeability and the presence of gas saturated sandstones the estimated gas in place in the tertiary upper cretaceous coals decreases significantly with stratigraphic age ranging between less than 2 bcf mi2 in the lower coal zones and 12 bcf mi2 in the uppermost coals the gas content especially of the deeper coals is lower than would be expected for the corresponding coal rank and burial depth most likely because the underpressuring has caused the release of gas from the coals and accumulation in adjacent sands the shallow coals although of low rank may contain important amounts of late stage biogenic methane the salinity of formation water in shallow coal seams where the flow is driven by topography is low generally less than 1500 mg l although in places it reaches 3000 5000 mg l the salinity of formation water in the deeper underpressured strata in the west central part of the basin is significantly higher reaching 18 000 mg l this affects treatment and or disposal strategies with regard to the water produced concurrent to coalbed methane the producibility of this resource depends on coal permeability which decreases west southwestward with increasing burial depth from the order of several darcys in the shallow zones to millidarcys in the deep zones the minimum effective stress which affects coal permeability by closing fractures increases west southwestward from zero at the erosional edge of these strata to approximately 20 mpa near the rocky mountain deformation front fractures including those in coal seams will generally be vertical and will propagate on a southwest northeast axis along the direction of the maximum horizontal stress in a direction generally perpendicular to the rocky mountain deformation front considering the hydrogeological and stress regimes in conjunction with estimations of the gas content in coals the region with probably good coalbed methane potential and producibility are the ardley coal zone in the scollard formation and maybe to a lesser extent the coal zones of the stratigraphically deeper edmonton and belly river groups along their respective subcrop in central and southern alberta the deep edmonton and belly river strata in western and central alberta have most likely a reduced coalbed methane potential as a result of lower gas content and of low permeability these regional considerations need to be applied against local studies of coal thickness rank permeability and gas content to identify the best targets for coalbed methane exploration and production

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

mass movement induced tsunami hazard on perialpine lake lucerne switzerland scenarios and numerical experiments previous studies of the sediments of lake lucerne have shown that massive subaqueous mass movements affecting unconsolidated sediments on lateral slopes are a common process in this lake and in view of historical reports describing damaging waves on the lake it was suggested that tsunamis generated by mass movements represent a considerable natural hazard on the lakeshores newly performed numerical simulations combining two dimensional depth averaged models for mass movement propagation and for tsunami generation propagation and inundation reproduce a number of reported tsunami effects four analysed mass movement scenarios three based on documented slope failures involving volumes of 5 5 to 20 8 106 m3 show peak wave heights of several metres and maximum runup of 6 to 10 m in the directly affected basins while effects in neighbouring basins are less drastic the tsunamis cause large scale inundation over distances of several hundred metres on flat alluvial plains close to the mass movement source areas basins at the ends of the lake experience regular water level oscillations with characteristic periods of several minutes the vulnerability of potentially affected areas has increased dramatically since the times of the damaging historical events recommending a thorough evaluation of the hazard

hydraulic fracturing and wellbore completion of coalbed methane wells in the powder river basin wyoming implications for water and gas production excessive water production more than 7000 bbl month per well from many coalbed methane cbm wells in the powder river basin of wyoming is also associated with significant delays in the time it takes for gas production to begin analysis of about 550 water enhancement activities carried out during well completion demonstrates that such activities result in hydraulic fracturing of the coal water enhancement activities as the operators in the basin call this procedure consists of pumping 60 bbl of water min into the coal seam during approximately 15 min this is done to clean the wellbore and to enhance cbm production hydraulic fracturing is of concern because vertical hydraulic fracture growth could extend into adjacent formations and potentially result in excess cbm water production and inefficient depressurization of coals analysis of the pressure time records of the water enhancement tests enabled us to determine the magnitude of the least principal stress s3 in the coal seams of 372 wells these data reveal that because s3 switches between the minimum horizontal stress and the overburden at different locations both vertical and horizontal hydraulic fracture growth is inferred to occur in the basin depending on the exact location and coal layer relatively low water production is observed for wells with inferred horizontal fractures whereas all of the wells associated with excessive water production are characterized by inferred vertical hydraulic fractures the reason wells with exceptionally high water production show delays in gas production appears to be inefficient depressurization of the coal caused by water production from the formations outside the coal to minimize cbm water production we recommend that in areas of known vertical fracture propagation the injection rate during the water enhancement tests should be reduced to prevent the propagation of induced fractures into adjacent water bearing formations in areas where s3 is unknown a minifrac should be done to determine the magnitude of s3 to know whether fracture propagation will be vertical or horizontal so the water enhancement activities at the time of well completion are done to minimize water production and optimize gas production

simulation study on evolution of coalbed methane reservoir in qinshui basin china a dynamic equilibrium model has been proposed to describe the coalbed methane concentration dissipation evolution process in coal including its generation storage and migration the model developed with a computational program has been applied to the qinshui basin china which allows to evaluate features of coal seam of the basin including coal quality and burial palaeo geothermal field and coal organic material maturation evolution history the simulation study was focused on coalbed methane concentration dissipation evolution history of the upper and lower main coal seams in the basin the results indicate that the whole evolution process can be divided into three stages at the first stage i e the primary concentration stage gas generation quantity and gas content were lower and only weak diffusion took place the second stage can be called the active concentration dissipation stage during this period coal organic material was matured at a higher rate generating a large amount of gas because of abnormal high palaeo geothermal field in the middle and late yanshan epoch as a result gas content in coal reservoir was higher and gas could be lost in different ways including diffusion cap outburst and permeation the third stage can be defined as the absolute dissipation stage at which coal organic material no longer generates gas meanwhile much gas was lost mainly by diffusion and partly by permeation simulation results further show that although the high gas generation led to active dissipation in the coal reservoir there still remains comparatively high gas content on the south and north ends of the qinshui basin due to the preserving geological conditions this suggests that these regions are favorable for coalbed methane exploitation which has been confirmed by recent geological exploitations in qinshui basin c 2007 published by elsevier b v

production characteristics and the key factors in high rank coalbed methane fields a case study on the fanzhuang block southern qinshui basin china abstract the temporal and spatial production characteristics of coalbed methane cbm wells in the fanzhuang block of the southern qinshui basin the first commercial cbm producing basin in china were studied to determine the dominant factors the study indicates that gas production differs significantly in different wells adjacent to or located in different tectonic areas in combination with the production characteristics in the temporal and spatial variations the impact of seven factors burial depth thickness of coal gas content porosity permeability effect of fracturing structural setting and hydrogeological conditions on the gas production was analyzed based on bivariate correlation analysis and gray system theory which are suitable for solving the complex interrelationships between multiple factors and variables the results indicate that hydraulic fracturing is an effective guarantee of high production cbm wells in the first several months during a high rank cbm field development however the effect of hydraulic fracturing on enhancing the gas production of cbm wells decreases with time because the initial reservoir permeability lower than the hydraulic fracture permeability limits the adsorption diffusion and flow of cbm this limitation inevitably leads to a slow gas production rate when the adsorbed cbm from the initial reservoir becomes the main gas source instead of the fracturing affected zone gas content and permeability are two key factors that dominate cbm well productivity because they perform elementary roles in controlling the volume of gas sources and conductivity respectively the structural setting and hydrogeological condition are also two important factors that dominate cbm well productivity because they can influence the spatial distribution of permeability and gas content as well as other factors such as aquifers

stable isotope geochemistry of coal bed and shale gas and related production waters a review coal bed and shale gas can be of thermogenic microbial or of mixed origin with the distinction made primarily on the basis of the molecular and stable isotope compositions of the gases and production waters methane ethane carbon dioxide and nitrogen are the main constituents of coal bed and shale gases with a general lack of c2 hydrocarbon species in gases produced from shallow levels and more mature coals and shales evidence for the presence of microbial gas include 13c ch4 values less than 50 covariation of the isotope compositions of gases and production water carbon and hydrogen isotope fractionations consistent with microbial processes and positive 13c values of dissolved inorganic carbon in production waters the co2 reduction pathway is distinguished from acetate methyl type fermentation by somewhat lower 13c ch4 and higher d ch4 but can also have overlapping values depending on the openness of the microbial system and the extent of substrate depletion crossplots of 13c ch4 versus 13c co2 and d ch4 versus 13c h2o may provide a better indication of the origin of the gases and the dominant metabolic pathway than the absolute carbon and hydrogen isotope compositions of methane in the majority of cases microbial coal bed and shale gases have carbon and hydrogen isotope fractionations close to those expected for co2 reduction primary thermogenic gases have 13c ch4 values greater than 50 and 13c values that systematically increase from c1 to c4 and define a relatively straight line when plotted against reciprocal carbon number although coals and disseminated organic matter in shales represent a continuum as hydrocarbon source rocks current data suggest a divergence between these two rock types at the high maturity end in deep basin shale gas reversals or rollovers in molecular and isotopic compositions are increasingly reported in what is effectively a closed shale system as opposed to the relative openness in coal measure environments detailed geochemical studies of coal bed and shale gas and related production waters are essential to determine not only gas origins but also the dominant methanogenic pathway in the case of microbial gases

application of seismic curvature attributes in the delineation of coal texture and deformation in zhengzhuang field southern qinshui basin coal texture refers to the in situ particle size morphological characteristics and structural components of coal beds and it determines the permeability and producibility of a coalbed methane cbm reservoir coal texture is commonly classified into undeformed coal with primary coal texture and deformed coal with increasing degree of deformation including cataclastic coal granulated coal and mylonitized coal geophysical logging has recently been proven effective for detecting coal texture in boreholes but it is inefficient for establishing a regional distribution where there have been only limited amounts of drilling in contrast seismic attributes have high lateral extent and an advantage in terms of characterizing fine structures even minor faults with throws of 2 3 m and other strata deformations by comparing seismic curvature data to the results of 221 core samples from the zhengzhuang field in the southern qinshui basin we provide a seismic curvature attribute based coal texture evaluation method evaluation of the results shows that the coal texture types of the no 3 coal seam include undeformed coal cataclastic coal and some granulated coal the undeformed coal is mainly located in the western and northwestern parts of the study area the cataclastic and granulated coals are mainly distributed in the southern and eastern parts of the study areas the permeability of no 3 coal seam is weakly correlated with undeformed coal and it has a high negative correlation with deformed coal permeability has a strong negative correlation with the maximum curvature attribute of the no 3 coal seam it is suggested that the in situ stress distribution combined with the curvature controlled the local development of the coal texture types and thus resulted in regional differences in permeability finally the distribution characteristics of coal textures of no 3 coal seam in the study area are divided into four types in which the undeformed cataclastic coal dominated area located in the midwestern part of the study area is the most favorable area for cbm production

generation accumulation and resource potential of biogenic gas biogenic gas is generated at low temperatures by decomposition of organic matter by anaerobic microorganisms more than 20 of the world s discovered gas reserves are of biogenic origin a higher percentage of gases of predominantly biogenic origin will be discovered in the future biogenic gas is an important target for exploration because it occurs in geologically predictable circumstances and in areally widespread large quantities at shallow depths in rapidly accumulating marine sediments a succession of microbial ecosystems leads to the generation of biogenic gas after oxygen is consumed by aerobic respiration sulfate reduction becomes the dominant form of respiration methane generation and accumulation become dominant only after sulfate in sediment pore water is depleted the most important mechanism of methane generation in marine sediments is the reduction of co2 by hydrogen electrons produced by the anaerobic oxidation of organic matter co2 is the product of either metabolic decarboxylation or chemical decarboxylation at slightly higher temperatures the factors that control the level of methane production after sediment burial are anoxic environment sulfate deficient environment low temperatu e availability of organic matter and sufficient space the timing of these factors is such that most biogenic gas is generated prior to burial depths of 1 000 m in marine sediments most of the biogenic gas formed can be retained in solution in the interstitial pore waters because of higher methane solubility at the higher hydrostatic pressures due to the weight of the overlying water column under certain conditions of high pressures and or low temperatures biogenic methane combines with water to form gas hydrates biogenic gas usually can be distinguished from thermogenic gas by chemical and isotopic analyses the hydrocarbon fraction of biogenic gas consists predominantly of methane the presence of as much as 2 of heavier hydrocarbons can be attributed to admixture of minor thermogenic gas due to low temperature degradation of organic matter the amounts of hydrocarbon components other than methane generally are proportional to temperature age and organic matter content of the sediments biogenic methane is enriched in the light isotope 12c dgr13c1 lighter than 55 ppt owing to kinetic isotope fractionation by methanogens the variations in isotopic composition of biogenic methane are controlled primarily by dgr13c of the original co2 substrate which reflects the net isotopic effect of both addition and removal of co2 the methane isotopic composition also can be affected by mixing of isotopically heavier thermogenic gas the possible complicating factors require that geologic chemical and isotopic evidence be considered in attempts to interpret the origin of gas accumulations accumulations of biogenic gas have been discovered in canada germany italy japan trinidad the united states and ussr in cretaceous and younger rocks at less than 3 350 m of burial and in marine and nonmarine rocks other gas accumulations of biogenic origin have undoubtedly been discovered however data that permit their recognition are not available

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

methanogenic pathways of coal bed gas in the powder river basin united states the geologic factor abstract coal bed gas of the tertiary fort union and wasatch formations in the powder river basin in wyoming and montana u s was interpreted as microbial in origin by previous studies based on limited data on the gas and water composition and isotopes associated with the coal beds to fully evaluate the microbial origin of the gas and mechanisms of methane generation additional data for 165 gas and water samples from 7 different coal bed methane bearing coal bed reservoirs were collected basinwide and correlated to the coal geology and stratigraphy the c1 c2 c3 ratio and vitrinite reflectance of coal and organic shale permitted differentiation between microbial gas and transitional thermogenic gas in the central part of the basin analyses of methane 13c and d carbon dioxide 13c and water d values indicate gas was generated primarily from microbial co2 reduction but with significant gas generated by microbial methyl type fermentation aceticlastic in some areas of the basin microbial co2 reduction occurs basinwide but is generally dominant in paleocene fort union formation coals in the central part of the basin whereas microbial methyl type fermentation is common along the northwest and east margins isotopically light methane 13c is distributed along the basin margins where d is also depleted indicating that both co2 reduction and methyl type fermentation pathways played major roles in gas generation but gas from the latter pathway overprinted gas from the former pathway more specifically along the northwest basin margin gas generation by methyl type fermentation may have been stimulated by late stage infiltration of groundwater recharge from clinker areas which flowed through highly fractured and faulted coal aquifers also groundwater recharge controlled a change in gas composition in the shallow eocene wasatch formation with the increase of nitrogen and decrease of methane composition of the coal bed gas other geologic factors such as burial thermal and maturation history lateral and vertical continuity and coalification of the coal beds also played a significant role in controlling methanogenic pathways and provided new perspectives on gas evolution and emplacement the early stage gas produced by co2 reduction has mixed with transitional thermogenic gas in the deeper central parts of the powder river basin to form old gas whereas along the basin margins the overprint of gas from methyl type fermentation represents new gas thus a clear understanding of these geologic factors is necessary to relate the microbiological biogeochemical and hydrological processes involved in the generation of coal bed gas

evaluation of coal texture distributions in the southern qinshui basin north china investigation by a multiple geophysical logging method abstract coal texture is indicative of coal mechanical strength which is important not only for evaluating coalbed methane cbm reservoir permeability but also for evaluating the possibility of coal and gas outbursts in underground coal mining this paper begins with a foundation of a geophysical logging based coal texture evaluation method that compares the digital logging data with the results from 108 coring samples then the method was applied to the analyses of coal textures in 39 cbm wells the results of which are discussed in terms of the vertical distribution of coal textures in the study area finally a ternary diagram based on thickness proportions of coal textures was used to identify reservoir compartments in the zhengzhuang field of the southern qinshui basin the results show that undeformed coals are easily distinguished from cataclastic and granulated coals because of the high den and gr of undeformed coals meanwhile cataclastic coal has lower response values of ac and lld than granulated coal which can be used in identifying cataclastic from granulated coal a multiple geophysical logging method combining the log data of den gr ac and lld was provided for predication of the coal textures in the zhengzhuang field the predicated results show that the coal seam can be vertically divided into three to eight sub layers with a typical interbedded pattern of undeformed and cataclastic coals on the upper and lower parts and granulated coal in the middle at a relatively large thickness the study area is divided into four major regions and 11 sub regions based on the classification of coal texture types the undeformed coal dominated region is located in the southwestern part of the study area indicating a low permeability in the coal reservoir the granulated coal dominated region is mainly in the northern and eastern parts of the study area and has resulted from deep burial and multi period structural activities the cataclastic coal dominated region is in the middle of the study area the coal reservoir in this region is possibly the most favorable for cbm production

a flying start then a slow slip the human tragedy caused by the sumatra andaman earthquake moment magnitude 9 3 on 26 december 2004 and its companion nias earthquake moment magnitude 8 7 on 28 march 2005 is difficult to comprehend these earthquakes the largest in 40 years have also left seismologists searching for the words and tools to describe the enormity of the geological processes involved four papers in this issue discuss aspects of a rupture process of surprising complexity the first such event to test the sensitivity and range of many new technologies a surprising feature of the earthquake is that after the initial rapid rupture subsequent slip of the plate interface occurred with decreasing speed toward the north