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

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

pyrosequencing reveals the dominance of methylotrophic methanogenesis in a coal bed methane reservoir associated with eastern ordos basin in china it is generally believed that biogenic coal bed methane cbm is an end product of coal biodegradation by methanogenic archaea and syntrophic bacteria in this work the archaeal and bacterial communities of cbm reservoir associated with ordos basin in china were investigated using 454 pyrosequencing sampling produced water coal and rock in the reservoir a total of 46 598 sequence reads were obtained all archaea were methanogens with the genus methanolobus predominating the genus consisted of 81 18 of pyrosequencing reads in water sample and 99 in coal and rock samples although the phylum proteobacteria was the main component of all samples bacterial communities in coal and rock samples were similar at the genus level which were distinctly separated with water sample the results strongly suggested that methylotrophic methanogenesis governed the biogenic cbm formation the separation of microbial communities between water and coal rock samples should be considered when investigating the process of coal biodegradation and the generation of new biogenic cbm c 2012 elsevier b v all rights reserved

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

western mediterranean environmental changes evidences from fluvial archives abstract when dealing with current and past landscape evolution a key issue addresses responses of geomorphic systems to the large number of influencing variables identifying morphodynamic phases and revealing interrelations with specific driving forces are demanding tasks for quaternary research in this paper we present late pleistocene and holocene fluvial sedimentation patterns of three western mediterranean river catchments namely jarama river guadalete river and guadalquivir river that extent along a climatic transect from semi humid sw spain to semi arid central spain these studies are based on extensive fieldwork conducted on 36 exposures and 13 drillings in floodplain positions field data is supported by geochemical analyses while the chronological framework was obtained from the analyses of 70 radiocarbon samples results show distinct patterns of fluvial sedimentation as well as soil formation linked to floodplain stability for each river catchment on regional or catchment scale pollen stratigraphical correlation and comparison with lacustrine records show that fluvial dynamics have a strong reaction to climatic shifts with phases of high fragility characterized by catchment erosion and floodplain sedimentation in response to climatic aridification events and phases of climate change in general the comparison of the examined river systems reveals that periods of supra regional floodplain sedimentation in several catchments occurred from 8 0 to 7 0 5 0 to 3 8 2 2 to 1 5 and around 1 0 as well as 0 4 ka cal bp while we found periods of supra regional soil formation from 13 3 to 12 7 7 0 to 5 1 with a short interruption around 6 0 to 5 5 ka 2 8 to 2 3 ka 1 4 to 1 2 ka and 0 8 to 0 5 ka cal bp beside these consistencies we found deviating dynamic patterns that are apparently expressed in terms of differing onset and offset differing durations or even the lack of fluvial system response the main reasons for this can be seen in different regional climate condition and impacts of further influencing factors or in different levels of sensitivity of the river catchments that may be controlled by initial hydrological conditions catchment size or the degree of anthropogenic influence a larger scale assessment shows that fluvial dynamic patterns are hardly comparable across entire spain due to strong spatial heterogeneity of physiographic and climatic conditions on the iberian peninsula in particular when areas are influenced by different circulation systems e g regions influenced by the atlantic ocean vs regions influenced by the mediterranean sea however the consideration of north atlantic marine records reveals a certain coupling between north atlantic coolings atmospheric processes leading to arid climate over large parts of spain as well as increased landscape instability including strong fluvial sedimentation activity attendant atmospheric conditions are discussed

surface textures of heavy mineral grains a new contribution to provenance studies abstract the study zone is geologically very complex and corresponds to the western limits of the betic cordilleras sw spain materials from the triassic to holocene are found here this study demonstrates that most of the surface textures seen on quartz are present on the seven selected heavy minerals sem analysis of heavy mineral grains reveals that certain morphologies are in part associated with particular surface textures this textural analysis enables the source areas to be differentiated more clearly equally it contributes to a deeper knowledge of the various stages of the grains provenance a good example is the study of the heavy minerals of the guadalete river terraces

geologic and hydrological controls on coal reservoir water production in marine coal bearing strata a case study of the carboniferous taiyuan formation in the liulin area eastern ordos basin china abstract coalbed methane cbm is commercially explored and produced in the continental permian shanxi formation of the southern qinshui and eastern ordos basins of china however cbm production in marine carboniferous taiyuan formation is hindered by a lack of knowledge about the controlling factors on water production the liulin area of the eastern ordos basin is one of the trail areas for cbm development in china in this study water yield characteristics and their influencing factors during cbm production in the liulin area were investigated by fluid inclusion studies core slice observations and stable isotope analyses of groundwater the results demonstrated that the recharge area for this limestone aquifer of the taiyuan formation is the exposed carbonate in the northeastern liulin area the thickness along with the dissolved pores and fractures of the limestone aquifer were closely related to the water production of the cbm well from an engineering point of view hydraulic fracturing allows the direct movement of water from coal seams to the roof limestone aquifers which was a key factor in the high water yield of cbm wells in the liulin area finally based on the structure and distribution of roof limestone as well as water production data the geologic scenarios for water production in the taiyuan formation was divided into four types these divisions indicated that the best prospective target areas for cbm production should have low numbers of faults small limestone thicknesses relatively large burial depths and normal reservoir pressures and temperatures the results of this study are helpful for cbm exploration and production in the marine coal bearing strata of china

a geochemical investigation of carboxylic acids released via sequential treatments of two surficial sediments from the changjiang delta and east china sea two surface sediments from the delta of the changjiang river the fourth largest river in the world in terms of water discharge and the seventh in terms of sediment discharge and an adjacent area of the east china sea were subjected to sequential treatments in order to obtain complete quantitative and qualitative information on carboxylic acid moieties five successive treatments allowed for the release of all acid moieties occurring in each sample i the unbound acids isolated from extracts ii the oh labile acids released by classical saponification iii the oh ptc labile acids obtained via an additional saponification with a phase transfer catalyst iv the h labile acids released by a subsequent acid hydrolysis and v the tightly bound acids only released by thermolysis these five fractions correspond to distinct pools whose occurrence reflects diaerences in the mode of linkage of the acid moieties and or in the protection provided by the structures to which they are linked such analysis of acid moieties provided information on i the relative contributions from microalgae bacteria and higher plants in the delta and seaward stations ii the degree of early diagenetic alteration for the acids derived from these diaerent sources and iii the types of microalgal and bacterial species implicated these features were also compared with the results of the only previous study where the sequential treatments were applied on surficial sediments from a sharply diaerent environment the lena river delta arctic 2000 elsevier science ltd all rights reserved

an accurate method for permeability evaluation of undersaturated coalbed methane reservoirs using early dewatering data abstract accurate determination of permeability is critical for the efficient development of coalbed methane cbm reservoirs permeability determination is mainly based on the feature straight line analysis method and the plate fitting method requiring pressure build up data although few analytical methods only require dynamic production data they usually have limitations in application due to complicated solution processes or insufficient consideration of cbm reservoir characteristics this study improves the previous method for determining the permeability of undersaturated cbm reservoirs firstly mathematical models are established for calculating permeability of undersaturated cbm reservoirs with constant permeability and variable permeability due to pulverized coal output blockage matrix shrinkage and stress dependence during the production process secondly the proposed models are validated by numerical simulation analytical and pressure build up test methods finally the models are applied to the muai cbm reservoir in sichuan basin china high middle and low permeability zones of the muai reservoir are classified the results show that when bottom hole pressure and water production data of cbm wells during single phase water flow period are processed by the proposed method and plotted in a rectangular coordinate system a strong linear relationship can be obtained for cbm reservoirs with constant permeability and variable permeability the slope of the fitted equations can be used to determine permeability efficiently and accurately compared with previous methods the new method provides better interpretation results for cbm wells with strongly fluctuating production data since the use of the integration of fluctuating data and cumulative water production reduce the effect of production fluctuation on the results due to its conciseness this method can rapidly calculate reservoir permeability around a large number of production wells and obtain permeability distribution in the reservoir providing guidance for cbm productivity forecasting and development policy adjustment

a model for lignin alteration part ii numerical model of natural gas generation and application to the piceance basin western colorado the model presented here simulates a network of parallel and sequential reactions that describe the structural and chemical transformation of lignin derived sedimentary organic matter som and the resulting generation of mobile species from shallow burial to approximately low volatile bituminous rank the model is calibrated to the upper cretaceous williams fork formation coal of the piceance basin at the multi well experiment mwx site assuming this coal is largely derived from lignin the model calculates the content of functional groups on the residual molecular species c h and o elemental weight percents of the residual species and moles of residual molecular species and mobile species including components of natural gas through time the model is generally more sensitive to initial molecular structure of the lignin derived molecule and the h2o content of the system than to initial temperature as the former affect the fundamental reaction paths the model is used to estimate that a total of 314 trillion cubic feet tcf of methane is generated by the williams fork coal over the basin history

a new evaluation of palaeo heat flows and eroded thicknesses for the carboniferous ruhr basin western germany palaeo heat flows and thicknesses of eroded carboniferous overburden in the coal bearing ruhr basin western germany were estimated using one dimensional basin modelling techniques thermal and burial histories for 11 localities were calibrated by comparing measured and calculated vitrinite reflectance data based on the assumption of pre tectonic maturation in contrast to former studies the kinetic easy r0 approach applied for the calculation of vitrinite reflectance lopatin s tti algorithm was used in addition for one well in order to demonstrate the impact of the selection of the algorithm for vitrinite reflectance calculation on the simulation results simulated palaeo heat flows for the time of maximum burial most probably in the stephanian range from 64 to 83 mw m2 and decrease towards the south these heat flows are lower than values computed during earlier studies but are still relatively high in comparison to recent foreland basins the regional distribution of palaeo heat flows indicates that the crust beneath the ruhr basin was relatively thin and thickened towards the south at the end of the carboniferous after the stephanian 2200 3500 m of carboniferous overburden were eroded an observed southward increase in eroded thicknesses is caused by an uplift of the area studied which decreased towards the north at the end of the variscan folding large thicknesses of deposited and later eroded carboniferous sediments have to be postulated to explain the maturity data even along the present southern margin of the ruhr basin this indicates that the late carboniferous sediments originally extended far to the south geological arguments suggest that the deposition of carboniferous sediments in the entire ruhr basin continued until the stephanian

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

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

coalbed methane accumulation and dissipation patterns a case study of the junggar basin nw china abstract the junggar basin is a potential replacement area of coalbed methane cbm development in china to improve the efficiency of cbm exploration we investigated cbm accumulation and dissipation patterns of coal profiles located in the northwestern southern eastern and central junggar basin based on the following criteria burial depth hydrogeological zone cbm origin cbm phase and cbm migration type we identified four types of cbm accumulation patterns 1 a self sourcing cbm pattern containing adsorbed gas of biogenic origin from shallow depth coal within a weak runoff zone 2 an endogenic migration pattern containing adsorbed gas of thermogenic origin from the medium and deep coals within a stagnant zone 3 an exogenic migration pattern containing adsorbed gas of thermogenic origin from deep coal within a stagnant zone and 4 an exogenic migration pattern containing adsorbed and free gas of thermogenic origin from ultra deep coal within a stagnant zone we also identified two types of cbm dissipation patterns 1 shallow depth coal within a runoff zone with mixed origin cbm and 2 shallow and medium deep coal seams with mixed origin cbm cbm migration in low rank coals was more substantial than that adsorbed in high rank coal cbm in shallow coal could easily escape in the absence of closed structures or hydrogeological seals cbm reservoirs occurred in deep coal where oversaturated gas may accumulate future exploration should focus on gas water sealing structures in shallow coalbeds cbm that occurred in adsorbed and free phases and other unconventional natural gas dominated by free gas in the coal stratum should be co explored and co developed

developmental geology of coalbed methane from shallow to deep in rocky mountain basins and in cook inlet matanuska basin alaska u s a and canada abstract the rocky mountain basins of western north america contain vast deposits of coal of cretaceous through early tertiary age coalbed methane is produced in rocky mountain basins at depths ranging from 45 m 150 ft to 1 981 m 6 500 ft from coal of lignite to low volatile bituminous rank although some production has been established in almost all rocky mountain basins commercial production occurs in only a few despite more than two decades of exploration for coalbed methane in the rocky mountain region it is still difficult to predict production characteristics of coalbed methane wells prior to drilling commonly cited problems include low permeabilities high water production and coals that are significantly undersaturated with respect to methane sources of coalbed gases can be early biogenic formed during the early stages of coalification thermogenic formed during the main stages of coalification or late stage biogenic formed as a result of the reintroduction of methane generating bacteria by groundwater after uplift and erosion examples of all three types of coalbed gases and combinations of more than one type can be found in the rocky mountain region coals in the rocky mountain region achieved their present ranks largely as a result of burial beneath sediments that accumulated during the laramide orogeny late cretaceous through the end of the eocene or shortly after thermal events since the end of the orogeny have also locally elevated coal ranks coal beds in the upper part of high volatile a bituminous rank or greater commonly occur within much more extensive basin centered gas deposits which cover large areas of the deeper parts of most rocky mountain basins within these basin centered deposits all lithologies including coals sandstones and shales are gas saturated and very little water is produced the interbedded coals and carbonaceous shales are probably the source of much of this gas basin centered gas deposits become overpressured from hydrocarbon generation as they form and this overpressuring is probably responsible for driving out most of the water sandstone permeabilities are low in part because of diagenesis caused by highly reactive water given off during the early stages of coalification coals within these basin centered deposits commonly have high gas contents and produce little water but they generally occur at depths greater than 5 000 ft and have low permeabilities significant uplift and removal of overburden has occurred throughout the rocky mountain region since the end of the eocene and much of this erosion occurred after regional uplift began about 10 ma the removal of overburden generally causes methane saturation levels in coals to decrease and thus a significant drop in pressure is required to initiate methane production the most successful coalbed methane production in the rocky mountain region occurs in areas where gas contents were increased by post eocene thermal events and or the generation of late stage biogenic gas methane generating bacteria were apparently reintroduced into the coals in some areas after uplift and erosion and subsequent changes in pressure and temperature allowed surface waters to rewater the coals groundwater may also help open up cleat systems making coals more permeable to methane if water production is excessive however the economics of producing methane are impacted by the cost of water disposal

organic geochemistry of surface sediments from the huanghe estuary and adjacent bohai sea china abstract surface sediment samples collected in may 1985 in the huanghe river and in the bohai sea and in the estuary mixing zone between river and marine waters were analyzed for fatty acids and aliphatic hydrocarbons sediments are characterized by low organic contents 0 06 0 39 of dry sediment total fatty acid concentrations vary from 2 9 to 18 1 g g 1 dry sediment lower values are found in the mixing zone whereas higher ones are observed in the marine area the spatial distribution of the relative importance of high molecular weight compounds c24 confirms that significant amounts of continental derived material are deposited in the mixing zone the presence of substantial amounts of unsaturated fatty acids such as n c20 5 and n c22 6 indicates well preserved organic matter from both phytoplankton and zooplankton sediments from both river and mixing zone show low and equal concentrations of microbial molecular markers from 0 09 to 0 74 g g 1 sum of iso and anteiso c15 c17 fatty acids marine sediments are characterized by much higher amounts of microbial organic material evidenced by high microbial marker concentrations reaching values up to 1 39 g g 1 total non aromatic hydrocarbons account for 1 9 4 3 of dry sediment representing from 0 08 to 0 34 of the organic carbon these concentrations are low compared to those of other estuarine sediments n alkane distribution patterns support a predominant origin from terrestrial plants cpi 3 1 7 9 some riverine and marine sediments show a predominance of n c17 indicating contributions from freshwater and marine planktons the analytical results indicate some contamination of the marine environment by petroleum products

provenance of silt and clay within sandy deposits of the lithuanian coastal zone baltic sea abstract mineralogical analysis of the silt and clay fraction of sandy deposits of 37 surface samples and grain size data are used to interpret sediment sources acting in the se baltic sea along the lithuanian coast mineralogical composition was determined using x ray diffraction xrd methods grain size distribution was obtained by standard dry sieving and pipette techniques for identification of sources we combined known compositional information of possible sources with logical models for mineral combinations related to regional geological provinces and processes supported by results of correlation and factor principal component analyses between minerals grain size parameters and bathymetric features of the area the main sources supplying sediment into the area are 1 the sambian peninsula to the south 2 the nemunas river whose discharge passes through the curonian lagoon and 3 late pleistocene till erosion on the sea floor in the north and at the olando kepure shore cliffs the general pattern of spatial distribution related to the identified sources for the fine grained sediment fraction is interpreted as a shore parallel transport of suspended matter flowing northwards in the southeastern part of the baltic sea

temporal trends of aliphatic and polyaromatic hydrocarbons in the bohai sea china evidence from the sedimentary record abstract this work reports the historical trends and sources of aliphatic hydrocarbons ahs and polycyclic aromatic hydrocarbons pahs in two 210 pb dated sediment cores extracted from the central mud areas of bohai sea bohai the toc tn ratio of the bulk organic matter om and the composition of the n alkanes suggest that the sedimentary organic matter was of mixed marine and terrigenous sources the coarser sediment grain size and decreasing c n ratios since 1976 could be attributed to the relocation of the yellow river mouth causing a decreased influence of yellow river derived sediments and associated om into the central bohai the concentration of total 16 pahs in the two cores ranged from 34 2 202 ng g mean 91 5 for bc1 and from 53 3 186 ng g mean 103 for bc2 with a high abundance of 2 3 ring pahs perylene in the two cores mainly originated from terrigenous sources via riverine discharge and thus could be potentially related to changes in the sediment load from the yellow river into the bohai over time petroleum inputs could be revealed by ratios of methylphenanthrenes to phenanthrene mp p and the patterns of more stable geochemical biomarkers hopanes and steranes along the two cores in addition to the presence of unresolved complex mixtures ucm in the surface layers source diagnostic ratios of pahs indicated a pyrogenic origin from biomass and coal combustion with a minor petroleum contribution downcore trends of compositional pahs profiles were in agreement with the socio economic development in china in the past decades this temporal variation of sedimentary pahs can also reflect a different evolution stage of energy structure in china as compared with those of the western developed countries

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

yangtze river sediments from source to sink traced with clay mineralogy abstract river bed sediments were collected from the main stream and major tributaries of the yangtze river for clay mineralogy study surface sediments from the yarlung zangbo river on the tibetan plateau were also examined for comparison the results show that the clay mineral compositions of the yangtze river display a similar pattern through the whole truck stream with illite being dominant kaolinite and chlorite being lesser abundant and smectite being minor component clay mineralogy shows distinct differences in the tributaries which correspond to the heterogeneous source rocks and weathering intensity of the drainage the illite crystallity and the illite chemical weathering index 5 a 10 a peak ratio both increase downstream indicating a increasing trend of hydrolysis along the river it also indicates that the upperstream of the drainage is characterized with physical weathering while the middle and lower reaches are controlled by chemical weathering process in accordance with the result derived by the illite indexes sediment input from upperstream including yalong jiang dadu he min jiang and jialing jiang accounts for the major sediment load whereas wu jiang xiang jiang gan jiang and dongting lake provide relatively less sediments

karst depressions as geoarchaeological archives the palaeoenvironmental reconstruction of zominthos central crete based on geophysical prospection sedimentological investigations and gis abstract sediment filled karst depressions e g dolines have rarely been used as geoarchives in greece due to an uncertainty about the thickness of accumulations and their vague suitability for palaeoenvironmental research however such terrestrial proxy data sources can yield important records for the analysis of the holocene landscape history a multi method approach was applied in order to evaluate the potential of colluvial fillings for reconstructing the geoarchaeological landscape in mount ida central crete subsequent to an area wide survey of appropriate karst hollows through remote sensing and gis analyses geophysical prospection refraction seismics earth resistivity tomography was conducted at the most promising archive locations selective percussion drilling within the sinkholes provided vibra cores for mineralogical and sedimentological investigations grain size distribution heavy and light minerals x ray diffraction thin sections as well as ams 14 c dates as demonstrated by the results the dolines are partially filled by loose material up to 20 m b s and thus offer valuable information about the environmental history the diversified sediment constitution indicates several geomorphodynamic oscillations and a polygenetic nature of the colluvial fills xrd spectra of clay minerals and quartz grain morphology both indicate a significant aeolian dust contribution to soil formation and pedo sediments glass shards and substantially heterogeneous heavy mineral compositions point to supra regional origin and external volcanogenic deposits minoan eruption of santorini 3 6 ka regarding the hitherto discussed distribution of z2 tephra in the mediterranean the spatial fallout must be revised as great amounts have also been deposited in the high mountains of crete moreover the redeposition of the sedimentary fills proves to be comparatively young since most materials were accumulated within the dolines post eruptively huge and previously unknown subsurface archaeological remains strongly suggest that year around settlement in the mid holocene might have been possible under better climatic conditions the results imply that karst depressions serve as suitable geoarchives particularly when investigated within a multi method approach

sedimentary hydrocarbons from a subtropical marine estuary petrogenic pyrogenic and biogenic hydrocarbons were determined in sediments from 48 sites around charlotte harbor a relatively undeveloped subtropical marine estuary along the south west coast of florida hydrocarbon concentrations generally ranged from 1 to 5 g g 1 which are lower than hydrocarbon values reported for most temperature estuarine sediments but agree well with values reported for sediments from more highly impacted subtropical estuarine systems little evidence of petrogenic or pyrogenic inputs was observed except for certain hot spots associated with marina land development and industrial activities sediments collected during the summer showed enhanced hydrocarbon concentrations over winter samples reflecting increased biogenic input from both marine and terrestrial sources data obtained in this and similar studies suggests that in these subtropical areas a steady state is established between hydrocarbon inputs and microbial degradation

the effect of sedimentary redbeds on coalbed methane occurrence in the xutuan and zhaoji coal mines huaibei coalfield china abstract the lithologies and permeabilities of caprocks have significant effects on coalbed methane cbm preservation to study the controlling effects of redbeds deposits on cbm occurrence in the xutuan and zhaoji coal mines of the huaibei coalfield in china the variations in mineralogical composition microstructure pore structure permeability and diffusion among the redbeds caprock samples neogene clay rock and ordinary coal measure strata sandstone mudstone and siltstone have been investigated the results indicate that redbeds are porous rocks with weaker sealing capabilities than coal strata caprocks allowing cbm to escape from the coal seam the formation of the lithological properties of the redbeds is closely related to their mineralogical composition and diagenesis redbeds are mainly composed of illite 57 64 calcite 25 33 quartz 6 12 muscovite 3 8 and pyrite

the analysis of quartz grain surface features as a complementary method for studying their provenance the guadalete river basin cadiz sw spain abstract the analysis of quartz grain surface features from several sandy deposits of the guadalete river basin guadalete terraces miocene calcarenites and aljibe sandstones have yielded data of considerable value in the study of the provenance of these materials the majority of the quartz grains of the miocene calcarenites present the same primitive surface features as those of the aljibe sandstones generalised polishing of their surface mechanical marks enlarged by solution and many conchoidal fractures and grooves corresponding to the high energy environment in which they were deposited the quartz grains of the guadalete terraces are mainly derived from the miocene calcarenites they show numerous fractures and polished grooves and have undergone a later stage of evolution forming isolated vs and silica deposits corresponding to a final fluvial means of transport these data indicate a possible evolution as follows 1 aljibe sandstones 2 miocene calcarenites 3 fluvial sands of the quaternary terraces of the guadalete river this evolution has been confirmed by study of the heavy mineral associations and the petrology of these materials thus quartz grain surface features may be an extremely useful instrument for studying provenance determining the evolutionary path that various sediments of a region have taken thereby complementing the data yielded by the mineralogy of heavy minerals and regional geology

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

hydrodynamic evolution from quartz microtextures of a beach ridge in qinghai lake china abstract beach ridges are landforms that exist on beach shorelines and can supply abundant information regarding palaeoenvironments to better understand the hydrodynamic processes of beach ridges a quartz microtexture analysis was carried out in this study the microtextural features of a total of 1063 quartz grains from seven beach ridge samples and eight reference samples from rivers a dune and a nearby beach were observed and analysed by scanning electron microscopy the qualitative and quantitative results suggest that the quartz microtextures of the beach ridge samples present more fresh surfaces and percussion marks than the river samples but less angularity the upper sequence samples from the beach ridge present higher values of fresh surfaces and percussion marks and lower dissolution than the lower sequence samples a cluster analysis shows that the hydrodynamic conditions of qinghai lake underwent pronounced changes from weak to strong and then to weak at the present time furthermore quantitative analyses indicate that the beach ridge and river sedimentary environments can be distinguished through the microtextural features of the 250 125 m size fraction however more grain size fractions should be observed and analysed to interpret the hydrodynamic conditions the quartz microtextural analysis of beach ridges may be an effective method reflecting the palaeohydrodynamic conditions

phylogenetic diversity of microbial communities associated with coalbed methane gas from eastern ordos basin china abstract microbial communities associated with biogenic coalbed methane cbm have been investigated extensively by sampling produced water and coal samples however little is known about the microbial communities associated with cbm gas in this study we employed pyrosequencing and real time polymerase chain reaction to investigate the microbial communities in cbm gas from a cbm field associated with ordos basin in china where biogenic cbm had been identified and methanogens and related bacteria had been found to be present in coal and produced water samples the pyrosequencing results revealed that the gom arc i group with 99 3 archaeal sequence reads was the predominant archaea in gas samples the main bacteria present in gas samples were proteobacteria in particular the genus herbaspirillum comprised approximately 76 of bacterial sequences most of the detected bacteria had the potential to degrade aromatic and cellulose derived compounds in coal and promote nitrogen cycling in coalbeds the microbial diversity in gas was lower than that in coal and produced water and significant differences were observed in the microbial communities in gas these results provided insights into the archaeal and bacterial communities associated with cbm gas at this location and may improve our understanding of the current status of archaeal and bacterial communities in cbm fields

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

numerical simulation of coalbed methane generation dissipation and retention in se edge of ordos basin china abstract this paper presents a numerical study on the formation history of coalbed methane cbm reservoir in the southeast edge of ordos basin china the coal seams studied belong to the late palaeozoic coal bearing series these coal seams have a burial history and experienced the process of subsidence rapid subsidence alternated with uplift and then uplift sequentially and underwent the geothermal actions at normal extremely high and then normal temperatures respectively coal organic matter of the coal seams matured in the triassic period and in the late jurassic to early cretaceous period the results from numerical simulation reveal that cbm reservoir evolution history can be classified into five stages namely primary initial stagnant active and dissipative stages in the first primary stage coal rank was very low and there was little methane generated and stored in the coal seams in the second initial stage the coal was converted to middle high volatile bituminous coal as a result a certain amount of methane was generated and began to accumulate in coal seams except part of it escaped from coal seams by diffusion and cap outburst in the third stagnant stage generation of methane was almost stagnant due to the temperature of the coal seam that dropped slightly and the maturation of coal organic matter stopped meanwhile cbm would keep dissipating through diffusion in the fourth active stage coal rank varied from high volatile bituminous coal a to semianthracite which accelerated pyrolysis gas formation and resulted in a large amount of methane generated at a high speed during this period cbm was increasingly accumulated in coal seams although there would be considerable amounts of gas dissipated from the coal seams in the last dissipative stage due to coal seams uplifted at various rates and no more methane generated cbm was continuously dissipated by diffusion throughout the whole coal seams and by permeation at some local areas the simulation provides insights for further interpretation of how many factors that control or affect the cbm reservoir formation history and cbm accumulation these factors include features of coal bearing series characteristics of coal seams physical properties of coal reservoir tectonic evolution history burial history and geothermal conditions etc in particular tectonic evolution history and gas generation are critical under given conditions cbm reservoirs in the study area were developed in different ways and the cbm was accumulated in the reservoirs at different levels for example the west part of study area is favourable for cbm accumulation as a result the gas content of the main coal seams in this region has a maximum of about 28 m3 t at depths of 900 1100 m and generally increases with the increasing of burial depth from the east to the west the coal reservoir is under saturated in the east part where the burial depth is shallower than about 500 m while the west part is saturated there is a close correlation of the lateral distribution of both gas content and saturation to the gas generation in the geological history

thermal maturity and organic composition of pennsylvanian coals and carbonaceous shales north central texas implications for coalbed gas potential thermal maturity was determined for about 120 core cuttings and outcrop samples to investigate the potential for coalbed gas resources in pennsylvanian strata of north central texas shallow 600 m 2000 ft coal and carbonaceous shale cuttings samples from the middle upper pennsylvanian strawn canyon and cisco groups in archer and young counties on the eastern shelf of the midland basin northwest and downdip from the outcrop yielded mean random vitrinite reflectance r o values between about 0 4 and 0 8 this range of r o values indicates rank from subbituminous c to high volatile a bituminous in the shallow subsurface which may be sufficient for early thermogenic gas generation near surface 100 m 300 ft core and outcrop samples of coal from areas of historical underground coal mining in the region yielded similar r o values of 0 5 to 0 8 carbonaceous shale core samples of lower pennsylvanian strata lower atoka group from two deeper wells samples from 1650 m 5400 ft in jack and western wise counties in the western part of the fort worth basin yielded higher r o values of about 1 0 pyrolysis and petrographic data for the lower atoka samples indicate mixed type ii type iii organic matter suggesting generated hydrocarbons may be both gas and oil prone in all other samples organic material is dominated by type iii organic matter vitrinite indicating that generated hydrocarbons should be gas prone individual coal beds are thin at outcrop 1 m 3 3 ft laterally discontinuous and moderately high in ash yield and sulfur content a possible analog for coalbed gas potential in the pennsylvanian section of north central texas occurs on the northeast oklahoma shelf and in the cherokee basin of southeastern kansas where contemporaneous gas producing coal beds are similar in thickness quality and rank