rossby wave propagation into the northern hemisphere stratosphere the role of zonal phase speed sudden stratospheric warming ssw events are to a dominant part induced by upward propagating planetary waves while theory predicts that the zonal phase speed of a tropospheric wave forcing a ects wave propagation into the stratosphere its relevance for ssw events has so far not been considered this study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward indicating that the stratosphere preselects eastward phase speeds for propagation especially for zonal wave number 2 this also a ects ssw events split ssw events tend to be preceded by anomalously eastward zonal phase speeds zonal phase speed may indeed explain part of the increased wave ux observed during the preconditioning of ssw events as for example for the record 2009 ssw event

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

growth characteristics and genetic types of pores and fractures in a high rank coal reservoir of the southern qinshui basin abstract in this paper field investigations such as underground coal wall observations and core log analyses have been conducted and combined with laboratory experiments such as the mercury intrusion method the low temperature liquid nitrogen adsorption method photomicrography and scanning electron microscopy sem to study the growth characteristics and genetic types of pores micro fractures and macro fractures in coal bed 3 of the southern qinshui basin and to analyze the connections between pores and fractures the results show that this coal bed prioritizes micropores and transition pores i e intermolecular pores and residual gas pores followed by macropores i e plant tissue pores and intergranular pores mesopores metamorphic gas pores do not develop moreover coal bed 3 contains a considerable number of closed and semi closed pores it develops two groups of exogenous fractures and cleats i e endogenous fractures and the formation is controlled by a paleotectonic stress field the cleats have a relatively small density and are usually filled by calcite and other minerals which are harmful to the permeability of the coal bed shrinkage micro fissures static pressure micro fissures structure micro fissures and ultramicroscopic fissures are all widely developed and are not filled by minerals micro fissures are important channels for the connections between pores and cleats ultramicroscopic fissures cut through some gas pores these two types of fractures improve the permeability and connectivity of the coal bed and are important links between different sizes of pores and fractures there are three levels of connections between pores and fractures namely connections between ultramicrostructures and microstructures connections between microstructures and cleats and connections between cleats and exogenous fractures

origin of minerals in joint and cleat systems of the pottsville formation black warrior basin alabama implications for coalbed methane generation and production coalbed methane is produced from naturally fractured strata in the lower pennsylvanian pottsville formation in the eastern part of the black warrior basin alabama major fracture systems include orthogonal fractures which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and less commonly cleats in coal joint fill calcite postdates most pyrite and is a weakly ferroan coarse crystalline variety that formed during a period of uplift and erosion late in the burial history pyrite forms fine to coarse euhedral crystals that line joint walls or are complexly intergrown with calcite stable isotope data reveal large variations in the carbon isotope composition of joint and cleat fill calcite 10 3 to 24 3 peedee belemnite pdb but only a relatively narrow range in the oxygen isotope composition of this calcite 16 2 to 4 1 pdb negative carbon values can be attributed to 13c depleted co2 derived from the oxidation of organic matter and moderately to highly positive carbon values can be attributed to bacterial methanogenesis assuming crystallization temperatures of 2050c most joint and cleat fill calcite precipitated from fluids with 18o ratios ranging from about 11 to 2 standard mean ocean water smow uplift and unroofing since the mesozoic led to meteoric recharge of pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned southeastern margin of the basin influxes of fresh water into the basin via faults and coalbeds facilitated late stage bacterial methanogenesis which accounts for the high gas content in coal and the carbonate cementation of joints and cleats diagenetic and epigenetic minerals can affect the transmissivity and storage capacity of joints and cleats and they appear to contribute significantly to interwell heterogeneity in the pottsville formation in highly productive coalbed methane fields joint and cleat fill calcite have strongly positive 13c values whereas calcite fill has lower 13c values in fields that are shut in or abandoned petrographic analysis and stable isotope geochemistry of joint and cleat fill cements provide insight into coalbed methane reservoir quality and the nature and extent of reservoir compartmentalization which are important factors governing methane production

stratigraphy and structure of coalbed methane reservoirs in the united states an overview stratigraphy and geologic structure determine the shape continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane coal in the united states is dominantly of pennsylvanian cretaceous and tertiary age and to date more than 90 of the coalbed methane produced is from pennsylvanian and cretaceous strata of the black warrior and san juan basins investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones coalbed methane production in the united states is mainly from foreland and intermontane basins containing diverse compressional and extensional structures balanced structural models can be used to construct and validate cross sections as well as to quantify layer parallel strain and predict the distribution of fractures folds and faults influence gas and water production in diverse ways however interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict

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

thermogenic and secondary biogenic gases san juan basin colorado and new mexico implications for coalbed gas producibility the san juan basin is the most prolific coalbed gas basin in the world with 1992 production exceeding 440 gcf footnote 12 4 billion m3 resources of approximately 50 tcf 1 4 trillion m3 and proved reserves of over 6 tcf 170 billion m3 coalbed gas wells with the highest production initial potential greater than 10 mcf day or 0 28 million m3 day occur in the overpressured north central part of the basin hydrologic analysis indicates that overpressure in the fruitland formation is artesian in origin and represents repressuring that developed during the middle pliocene highly permeable laterally continuous coal beds override abandoned shoreline pictured cliffs sandstones and extend to the elevated recharge area in he northern basin to form a dynamic regionally interconnected aquifer system coal rank and basin hydrodynamics control the composition of fruitland coalbed gases which varies significantly across the basin chemically dry gases in the north central part of the basin coincide with meteoric recharge and regional overpressure the consistency of methane dgr13c values across the basin the presence of isotopically heavy carbon dioxide in coalbed gases and bicarbonate in formation waters and biodegraded n alkane distributions of some coal extracts indicate that coalbed gases in the north central basin are a mixture of thermogenic 25 50 secondary biogenic 15 30 and migrated thermogenic 12 60 gases migrated conventionally and hydrodynamically trapped gases in situ generated secondary biogenic gases and solution gases result in gas content that plot on or above the coal sorption isotherm bacteria transported basinward in groundwater flowing from the elevated northern basin margins metabolized wet gas components n alkanes and organic compounds in the coal and generated secondary biogenic methane and carbon dioxide subsequent to coalification uplift erosion and cooling these gases may be limited to basin margins where shallow depths and structural deformation result in higher permeability or may extend more than 35 mi 56 km basinward from the recharge zone the presence of appreciable secondary biogenic gas indicates an active dynamic flow system with overall permeability sufficient for high productivity basin hydrogeology reservoir heterogeneity location of permeability barriers no flow boundaries and the timing of biogenic gas generation and trap devel pment are critical for exploration and development of unconventional gas resources in organic rich rocks

evolution of coal bed methane in southeast qinshui basin china insights from stable and noble gas isotopes abstract the late carboniferous early permian coal seams of the qinshui basin in shanxi province are the most prolific producer of coalbed methane cbm in china methane formed in the late triassic during deep burial and reheating in late jurassic early cretaceous driven by magmatic underplating basin inversion brought the coal seams to 400 700 m from the surface in the mid late cenozoic here we present results of a study aimed at understanding the origin of the methane and how it was affected by cenozoic exhumation of the basin methane from a 12 km traverse perpendicular to the basin margin in the southeast part of the basin have stable isotope compositions 13c 30 2 to 35 2 and d 155 to 194 indicating a thermogenic origin with limited biogenic input they are however lighter than expected based on coal maturity and c1 c2 c3 1000 are significantly higher than typical thermogenic methane 90 of the radiogenic 4he produced in the coals has been lost prior to equilibrium between gas and water phase in the reservoir this likely occurred in response to gas loss process during rapid exhumation in cenozoic showing that the he and ar content of natural gases is a sensitive indicator of gas loss event caused by recent basin inversion the event may have led to the loss of up to 44 of the methane from the coal seams this study demonstrates the importance of basin inversion on gas preservation in shallow cbm and shows that in contrast to 13cch4 the light noble gases are essential for tracing such a process

a numerical evaluation on the effects of impermeable faults on degasification efficiency and methane emissions during underground coal mining abstract impermeable geologic faults in the coal seam can cause intermittent production problems or can cause unexpected amounts of water or gas to issue from degasification boreholes these faults also can impact methane emissions into the mine workings especially if they hinder proper and effective degasification of the coal bed they may also act as barriers for methane flow in the coal seam although this might seem beneficial for advancing mine workings faulting may also cause gas pressure buildups and result in compartmentalization of the gassy regions from which large quantities of water and methane may rush into mine workings this study uses reservoir simulations to illustrate the effects of impermeable faults with and without throws on the production performance of vertical and horizontal degasification boreholes these boreholes were drilled from the surface to intercept the coal layer and fault and were assumed to produce methane two years prior to mining of the coal seam longwall advances and face position related emissions and reservoir properties were characterized using sector definitions along the path of the panel grids this work numerically evaluates water and gas productions of each borehole and presents the effects and the impacts of impermeable faults on methane emissions due to an advancing coal face the results can be used to understand the effects of impermeable faults on borehole productions and face emissions due to these coal seam anomalies

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

study of hydrochemical characteristics of cbm co produced water of the shizhuangnan block in the southern qinshui basin china on its implication of cbm development abstract coalbed methane cbm co produced water is primarily coal seam water it may be mixed with fracturing fluids especially during the early drainage stage or with other aquifer water if the coal seam is connected with an aquifer via artificial or natural fractures faults if the impacts of fracturing fluids and other aquifer water can be removed the chemical characteristics of cbm co produced water can act as effective indicators for cbm exploration and development based on the water chemistry analyses of 119 samples collected from 47 cbm wells over four years quarterly sampling in the shizhuangnan block qinshui basin the dynamic characteristics of the cbm co produced water chemistry that were influenced by fracturing fluids were studied in this study relationships between the major cbm co produced water ions were determined and the relationship between the cbm co produced water ions and gas production were investigated the results suggest that the cbm co produced water chemical signature of the shizhuangnan block is similar to that of other coal seam waters from around the world being characterized by the sodium chloride bicarbonate water types that are depleted in calcium and magnesium ions and exhibit highly lowered sulfate concentrations due to the mixing with the fracturing fluids and coal seam water the tds sodium chloride and calcium and magnesium ion concentrations decrease during the early drainage stage following a power law function however bicarbonate and sulfate concentrations do not significantly vary the na and cl na cl and alkalinity cl and na cl and na alkalinity ratios exhibit a positive linear relationship strong positive linear relationship and exponentially decaying relationship respectively additionally 10 meq l of cl may serve as a dividing line for the presence or absence of the fracturing fluid affect na and cl may release organic bound chlorine complexes from the coal during coal metamorphism the tds and bicarbonate concentration of the cbm co produced water produced by the gas production wells are all 1000 mg l and 8 meq l respectively the bicarbonate concentration is influenced by both the lch which is the height of the liquid level compared to the coal bed surface at the onset of water production at a cbm well and hydraulic conductivity fault and its distribution controls the distribution of the high gas yield wells

a numerical study on optimization of multilateral horizontal wellbore patterns for coalbed methane production in southern shanxi province china abstract china s southern shanxi province contains thick gassy coals of anthracite rank these high methane content higher than 500 ft 3 ton coals necessitate pre mining methane drainage to enhance the health and safety of underground coal workers both traditional vertical wells and multilateral horizontal wells which were shown to perform better have been drilled in the area in order to effectively reduce the gas content of coals however optimization of well drilling patterns is crucial to improve the gas drainage by boosting well performance and resulting in significant additional recovered gas in a cost effective manner in this study exploration borehole data from an undeveloped coalbed methane field in china s qinshui basin was obtained where permeability is expected to range from 0 1 to 10 md reservoir modeling conducted in this study concludes that in the presence of low permeability coals less than 1 0 md well patterns can be optimized to maintain high methane production rates in this work relationships to determine combinations of horizontal lateral spacing and permeability that yield similar production curves were developed in order to maximize production pinnate wells with laterals spaced at 600 ft intervals in reservoirs with 2 0 md permeability performed similar to those with 200 ft lateral intervals in 0 5 md reservoirs additional similar relationships were drawn for reservoirs ranging from 0 1 to 8 0 md furthermore because of the qinshui basin s potential high stress regime pitchfork and pinnate horizontal well patterns were analyzed based on their potential for catastrophic wellbore failure at well junctions and producing well branches analyses concluded that pitchfork wells had a significantly lower risk for significant wellbore loss due to borehole collapse while providing the opportunity for higher gas recovery in reservoirs exhibiting directional permeability

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

the characteristics and origins of cleat in coal from western north china cleat in coal influences the occurrence migration and production of coalbed methane therefore research on the cleat can provide some important information for coalbed methane exploration and development the characteristics and origin of cleat in coal of western north china are discussed with respect to field investigation and laboratory experiments cleat in coal of western north china can be divided into two classes face cleat and butt cleat three network patterns of face and butt cleats are identified reticular isolated and random when the vitrinite reflectance is less than 1 35 the cleat frequency increases with the rise of coal rank when the reflectance is more than 1 35 there are three relationships between the cleat frequency and coal rank with the rise of coal rank 1 the cleat frequency decreases 2 remains constant or 3 decreases slowly and then remains constant the mineral filling in the cleats is mainly calcite rarely clay minerals and pyrite intrinsic tensile forces fluid pressure and tectonic stresses are three controls to form cleats two mechanisms of cleat annealing which are the filling of secondary maceral and agglutination are revealed finally the controls on the cleat annealing are briefly described

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

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

deciphering subduction from exhumation in the segmented cycladic blueschist unit central aegean greece the cycladic blueschist unit cbu represents the northern passive margin of the adria continental block and ophiolites that are the remnants of the pindos ocean which were affected by high pressure low temperature metamorphism in the blueschist and eclogite facies during the eocene prior to the lutetian the ophiolitic and margin units were thrust towards the sw inside a ne dipping subduction zone two subsequent exhumation stages are characterized by top to the ne senses of shear i from mantle depths to lower crustal levels before 37 ma which was accommodated by an extensional inversion of the vardar suture zone and ii from deep crustal levels to the near surface between 30 and 20 ma which was accommodated by the north cycladic detachment it is during this late stage of ductile exhumation that the central cyclades core complex was exhumed segmentation of the cbu by normal faults started at 12 ma as recorded by the low temperature thermochronometers and was coeval with block rotation and folding with ns trending axes which were predominantly controlled by the myrthes ikaria strike slip fault in the centre of the cyclades a map restoration of the cbu geometry prior to segmentation has been carried out using available structural and paleomagnetic data the restoration shows that following the cbu exhumation from mantle depths to crustal levels a single core complex was exhumed along a single ne dipping detachment

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

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

identification of coal structures using geophysical logging data in qinshui basin china investigation by kernel fisher discriminant analysis abstract coal structure is closely related to the porosity and permeability of coal reservoirs which not only affects the enrichment of coalbed methane cbm but also influences the hydraulic fracturing and efficient development of cbm the accurate identification of the coal structure would be a critical issue in cbm exploration and development and is always a challenge compared with traditional methods for identifying coal structure base on borehole cores or mining seam observation geophysical logging has become the most economic and efficient technique several linear correlations have been established to describe the relationships between the coal structures and well logs however those correlations cannot accurately reflect nonlinear relations between them therefore a reliable and efficient method to identify coal structure is needed as a powerful nonlinear classifier the kernel fisher discriminant analysis kfd method has been widely used due to its strong generalization ability in this paper a new quantitative coal structure identification model was developed based on the kfd method by using geophysical logging data the model was trained tested and optimized using 178 logging data sets from 15 cbm wells in qinshui basin china the approach accounted for all the available well logging attributes and the training data sizes and kernel parameters were analyzed to get the most appropriate model in practice in addition the built model was validated individually by employing logging data of a new cbm well the results indicate that the kfd based identification model has high prediction accuracy which can be used as a reliable method for coal structure identification the kfd method exhibits strong capability during the modeling and generalization in the determination of nonlinear relationships which provides an efficient way for the coal structure prediction in basic research of coal reservoirs

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