a molecular organic carbon isotope record of miocene climate changes the difference in carbon 13 13c contents of hopane and sterane biomarkers in the monterey formation naples beach california parallels the miocene inorganic record of the change in 18o 18o reflecting the miocene evolution from a well mixed to a highly stratified photic zone upper 100 meters in the pacific steranes 13c 25 4 0 7 per mil versus the pee dee belemnite standard from shallow photic zone organisms do not change isotopically throughout the miocene in contrast sulfur bound c35 hopanes likely derived from bacterial plankton living at the base of the photic zone have systematically decreasing 13c concentrations in middle and late miocene samples 13c 29 5 to 31 5 per mil consistent with the middle miocene formation of a carbon dioxide rich cold water mass at the base of the photic zone

borehole sampling of fracture populations compensating for borehole sampling bias in crystalline bedrock aquifers mirror lake grafton county new hampshire abstract the clustering of orientations of hydraulically conductive fractures in bedrock at the mirror lake new hampshire fractured rock study site was investigated by comparing the orientations of fracture populations in two subvertical borehole arrays with those mapped on four adjacent subvertical roadcuts in the boreholes and the roadcuts the orientation of fracture populations appears very similar after borehole data are compensated for undersampling of steeply dipping fractures compensated borehole and pavement fracture data indicate a northeast striking population of fractures with varying dips concentrated near that of the local foliation in the adjacent rock the data show no correlation between fracture density fractures linear meter and distance from lithologic contacts in both the boreholes and the roadcuts the population of water producing borehole fractures is too small 28 out of 610 fractures to roadcuts the population comparisons however the orientation of large aperture fractures which contains all the producing fractures contains two or three subsidiary clusters in orientation frequency that are not evident in stereographic projections of the entire population containing all aperture sizes further these subsidiary orientation clusters do not coincide with the dominant subhorizontal and subvertical regional fracture orientations

the diagenetic fate of taraxer 14 ene and oleanene isomers abstract the extractable organic matter in holocene to early miocene deep sea sediments from site 645 odp leg 105 in baffin bay contains almost exclusively biological markers of terrigenous origin pentacyclic triterpenoids of the ursene and amyrin oleanene type often occur as the most abundant compounds in the aliphatic hydrocarbon ketone and alcohol fractions of the sediment extract a specific diagenetic reaction involves the conversion of taraxer 14 ene into olean 12 ene in the upper 700 metres of the sedimentary sequence the taraxerene to oleanene conversion is complete before the onset of isomerisation of diasterenes at c 20 in the sediment as well as in laboratory simulation experiments olean 12 ene further isomerises to olean 13 18 ene and olean 18 ene the latter of which may be the direct precursor of 18 h and 18 h oleanane found in sediments containing more mature organic matter and in crude oils the subsurface interconversion of these triterpenoid skeletons indicate that oleanane does not necessarily start life as an oleanoid

decelerating holocene sea level rise and its influence on southwest florida coastal evolution a transgressive regressive stratigraphy abstract the ten thousand islands tti are a myriad of low relief mangrove islands that lie along the low energy subtropical southwest florida coast the region has been subjected to a relative rise in holocene sea level which has continuously decelerated to its present rate data derived from surface and subsurface sampling indicate that the holocene sediment package of the tti area consists of two sediment sequences the lower sequence is transgressive and was generated as coastal salt marsh and or terrestrial environments were submerged and replaced by a shallow coastal marine setting the upper sediment sequence consists primarily of 1 biogenic shallowing upwards sequences or 2 thickened mangrove peat layers reflecting island emergence and shoreline stabilization respectively island emergence compartmentalized the area further reducing wave and current energy and promoting the infilling of the protected bays through deposition of organic rich shelly mudstone and wackestone based on coastal stratigraphy and 14c dates the formation of his transgressive regressive sediment sequence is directly related to changing rates of holocene sea level rise reported to have occurred between 3 500 and 3 200 ybp continued regressive sedimentation could eventually generate a 5 10 m thick transgressive regressive sediment couplet with an aerial extent of over 300 km2 in roughly 10 000 years this externally forced sediment couplet compares remarkably well to individual small scale transgressive regressive cycles which repeat tens to hundreds of times throughout the geologic record see james 1984 the results of this study thus support the allocyclic mechanism as a viable working hypothesis for the generation of these small scale rock cycles

high latitude hydrological changes during the eocene thermal maximum 2 abstract the eocene hyperthermals including the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 represent extreme global warming events 56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations an initial study on petm characteristics in the arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound specific carbon and hydrogen isotopic 2h 1h records from sedimentary leaf wax lipids in this study we apply this isotopic and hydrological approach on sediments deposited during etm2 from the lomonosov ridge integrated ocean drilling program expedition 302 our results show similar 2h 1h changes during etm2 as during the petm with a period of 2h enrichment 20 relative to pre event values just prior to the negative carbon isotope shift cie that is often taken as the onset of the hyperthermal and more negative lipid 2h values 15 during peak warming notably lipid 2h enrichment at the base of the event is coeval with colder tex 86 h temperatures if 2h 1h values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation the observed local relationship between temperature and 2h 1h values for the body of etm2 is precisely the opposite of what would be predicted using a simple rayleigh isotope distillation model assuming a meridional vapor trajectory and a reduction in equator pole temperature gradients overall a negative correlation exists between the average chain length of n alkanes and 2h 1h suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes the negative correlation falls across three separate intervals the base of the event the initial cie and during the h2 hyperthermal of which the assignment is not fully certain three possible mechanisms potentially explain 2h enriched signals at the base of the event including 1 intense local drying and cooling leading to evaporative 2h enrichment 2 changes in frequency intensity of storm events and its impact on high latitude amount effects and 3 changes in low latitude temperatures evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases generation of similar high resolution isotopic and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early eocene hyperthermals

tracing early charged oils and exploration directions for the wenchang a sag western pearl river mouth basin offshore south china sea the wenchang a sag is the largest petroleum producing sub depression in the western pearl river mouth basin offshore south china sea the eocene wenchang formation and the early oligocene enping formation are the two major source rocks in the sag the oil discoveries in this region mainly originated from the enping fm how to objectively estimate the petroleum potential of the wenchang fm and trace the wenchang oils has long been the focus of research and exploration in this region in this paper inclusion oils obtained from reservoir sandstones as well as typical reservoir oils and potential source rocks were investigated by systematic geochemical methods oil oil and oil source rock correlations indicate that inclusion oils in the central and marginal areas of the wenchang a sag had similar geochemical characteristics and mainly originated from the wenchang source rocks the reservoir oils in the central area are derived mainly from the enping source rocks while in the marginal areas they have mixed characteristics of both the enping and wenchang formations combining the tectonic sedimentary evolution and petroleum generation histories it is concluded that the two source rocks in the wenchang a sag have generated oils but in the central areas the main stage of oil generation of the wenchang fm was much earlier than the formation time of the traps resulting in the dissipation of most of the early generated wenchang sourced oils in the marginal areas the main stage of oil generation of the wenchang fm was later and the wenchang oils not only could be captured as fluid inclusions in the reservoir quartz grains but also migrated and accumulated into oil pools in which they mixed with the enping sourced oils the early lithological and structural traps in the central and marginal areas of the wenchang a sag especially in the northern part of the shenhu uplift are the most prospective areas for further exploration of the sag

the oleananes origin maturation and limits of occurence in southern nigeria sedimentary basins oleananes occur within well defined age and paleogeographic boundaries in the sedimentary province of southern nigeria thus signifying that the biomarkers may be analogous to index fossils in anambra syncline lower benue trough the biomarkers are found in rocks which are as old as late upper cretaceous in tertiary niger delta the concentration composition and distribution of the oleananes in rocks and oils are determined mainly by palaeodepositional environment and thermal history and are independent of age and geographical location of specific samples oleanane content varies with increasing burial depth with peak concentration coinciding within rm range 0 4 0 6 implying early generation of hydrocarbons from the basin s typically resin rich kerogens it is evident that the oleanane content parameter is superior to the hopane and sterane isomerisation indices for monitoring thermal maturation in the delta and for differentiating paralic from paralic marine source facies as well as early from late generated oils

δ2 triterpenes early intermediates in the diagenesis of terrigenous triterpenoids a series of 2 triterpenoids oleana 2 12 diene oleana 2 13 18 diene oleana 2 18 diene ursa 2 12 diene and taraxera 2 14 diene has been identified in holocene buried mangrove sediments florida usa by comparison of the mass spectra of and by co injections with authentic standards in the oligocene brandon lignite vermont usa oleana 2 12 diene and oleana 2 13 18 diene were also identified along with two a ring contracted amyrin derivatives by comparison with the sedimentary occurrence of related analogues of oxyallobetulin and betulin and the demonstrated diagenetic formation of lup 2 ene from lupan 3 one these novel terrigenous biological markers are considered diagenetic products formed by dehydration of precursor molecules such as and amyrin and taraxerol the identification of these early intermediates brings us one step closer to the full understanding of the diagenetic fate of terrigenous triterpenoids

sterane isomerisation and moretane hopane ratios in crude oils derived from tertiary source rocks the extent of sterane isomerisation reactions and the moretane hopane ratios of 234 crude oils taken world wide from a wide variety of source rocks of differing geological ages have been measured this data indicates that in 78 crude oils derived from tertiary source rocks sterane isomerisation reactions as determined by the 20s 20s 20r ration of the c29 5 h 14 h 17 h normal steranes and the c29 iso iso normal ratio iso 5 h 14 h 17 h are mainly incomplete and sometimes considerably so in addition the same crude oils have 17 h 21 h moretane 17 h 21 h hopane ratios which are significantly greater predominantly in the range 0 10 0 30 than those of crude oils derived from older mature source rocks mainly less than 0 1 this data for crude oils lends support to the hypothesis proposed by mackenzie and mckenzie 1983 for source rock extracts that the time temperature constraints of sterane isomerisation reactions are such that the time available for isomerisation in tertiary sediments is generally insufficient despite generation of crude oil at relatively high temperatures an alternative hypothesis is that the incomplete sterane isomerisation of tertiary crude oils may be due to generation of these crude oils from their deltaic land plant containing source rocks under low heating conditions a third hypothesis proposes that the tertiary crude oils may have picked up the incompletely isomerised steranes from immature sediments during migration although possible in particular instances such a mechanism does not appear to be generally applicable since in that case the phenomenon would then appear to be restricted to the tertiary the higher moretane hopane ratios of the tertiary crude oils could suggest that constraints similar to those applying in sterane isomerisation also operate in the conversion of moretane to 17 h hopane

genetic correlation of biodegraded crude oils from lower assam india using biomarker compositions abstract crude oils occurring in the tertiary reservoirs of the assam basin are waxy of deltaic origin and similar to a number of oil occurrences in south east asia in lower assam however crude oils occurring at shallow depths in various structures have been biodegraded and are heavy highly aromatic and depleted in n alkanes and isoprenoid alkanes the loss of these alkanes makes geochemical interpretation of these data with regard to source maturity and correlations difficult the biomarkers of the sterane terpane and phenanthrene series in these oils remain unaffected by biodegradation and their distributions show that the oils have originated from predominantly terrestrial organic matter higher plant contributions and deltaic environments of deposition can be inferred from the high concentrations of oleanane and bicadinanes the oils are genetically correlatable on the bsis of their biomarker fingerprints they are mature and were generated from source rocks during the late categenetic phase the occurrence of the oil pools in immature rocks suggests migration of oils from deep seated mature source rocks probably through faults acting as conduits followed apparently by alteration in shallow accumulations

empirical and numerical approaches for geomechanical characterization of coal seam reservoirs abstract the effects of fractures or joints on geomechanical properties of coal when transitioning from small samples to larger field scales have long been recognized two geomechanical characterization methodologies for of a coal seam for reservoir engineering are presented which attempt to account for these scale effect the first is a well established empirical rock mass classification method the geological strength index gsi the second is a newly developed numerical technique termed the synthetic rock mass srm gsi was developed to empirically account for the influence of rock joint density and joint surface conditions on the behaviour of the rock mass the established gsi to strength and deformation theories are reviewed and an approach to account for joint stiffness based on the minimum confining stress is presented the srm approach to jointed rock mass geomechanical characterization is a numerical modeling technique which combines the bonded particle model for rock and discrete fracture network simulation the intact or matrix of the srm is calibrated to laboratory data the dfn inserted creating a numerical representation of the rock mass which can then be tested at any scale in each case the approaches attempt to geomechanically characterize strength modulus etc the large scale behaviour of the coal seam where the properties can then be used for continuum type simulation reservoir simulation borehole stability etc

hydrologic properties of coal beds in the powder river basin montana ii aquifer test analysis abstract a multiple well aquifer test to determine anisotropic transmissivity was conducted on a coal bed in the powder river basin southeastern montana as part of a multidisciplinary investigation to determine hydrologic conditions of coal beds in the area for the test three wells were drilled equidistant from and at different angles to a production well tapping the flowers goodale coal seam a 7 6 m thick seam confined at a depth of about 110 m the test was conducted by air lift pumping for 9 h and water levels were monitored in the three observation wells using pressure transducers drawdown data collected early in the test were affected by interporosity flow between the coal fracture network and the matrix but later data were suitable to determine aquifer anisotropy as the slopes of the late time semilog time drawdown curves are nearly identical and the zero drawdown intercepts are different the maximum transmissivity trending n87 e is 14 9 m 2 d and the minimum transmissivity 6 8 m 2 d giving an anisotropy ratio of 2 2 1 combined specific storage of the fractures and matrix is 2 10 5 m and of the fracture network alone 5 10 6 m the principal direction of the anisotropy tensor is not aligned with the face cleats but instead is aligned with another fracture set and with dominant east west tectonic compression results of the test indicate that the flowers goodale coal bed is more permeable than many coals in the powder river basin but the anisotropy ratio and specific storage are similar to those found for other coal beds in the basin

biomarker signatures of the iconic glossopteris plant abstract glossopteris is the quintessential marker plant that dominated the forests of the southern hemisphere continents during the permian before their abrupt extinction at the close of the palaeozoic fossilized leaf and stem remains of glossopteris plants collected from the permian succession of eastern india were analysed to recognize the molecular signatures of solvent extractable and non extractable organic matter lipid derived aliphatic and aromatic biomarkers were studied using gc ms and gc gc tofms while tetramethylammonium hydroxide tmah thermochemolysis with gc ms and gc gc tofms was used to reveal lignin precursors the thermal maturity indices indicate low thermal rank for both samples the presence of aromatic diterpanes in the leaf extract suggests that the glossopteris plant was able to biosynthesize abietic acid and related plant terpenoids the thermochemolysis products thermochemolysates of the samples contain monomethoxy and dimethoxybenzene derivatives produced from p hydroxyphenyl and guaiacyl units of lignin respectively which are the main constituents of extant gymnosperm lignin the thermochemolysates indicate that lignin biosynthesis had evolved in glossopteris

a high resolution historical record of holocene anoxygenic primary production in the black sea i reconstruct the historical record of anoxygenic primary production in the black sea over the last 8200 years by an analysis of chlorobium carotenoids in sediments anoxygenic photosynthesis in the black sea occurs only when hydrogen sulfide containing deep water penetrates the euphotic zone the data show that the black sea has experienced large fluctuations in the extent of anoxygenic primary production and therefore the depth of the h2s chemocline throughout much of the holocene changes in the depth of the h2s chemocline also shift the dominant phytoplankton populations in the water column to noncarbonate bearing species and result in the formation of intense dark bands in sediments

characteristics and origins of coal cleat a review abstract cleats are natural opening mode fractures in coal beds they account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations because permeability and stimulation success are commonly limiting factors in gas well performance knowledge of cleat characteristics and origins is essential for successful exploration and production although the coal cleat literature spans at least 160 years mining issues have been the principal focus and quantitative data are almost exclusively limited to orientation and spacing information few data are available on apertures heights lengths connectivity and the relation of cleat formation to diagenesis characteristics that are critical to permeability moreover recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well studied parameters can yield insight into coal permeability more effective predictions of cleat patterns will come from advances in understanding cleat origins although cleat formation has been speculatively attributed to diagenetic and or tectonic processes a viable mechanical process for creating cleats has yet to be demonstrated progress in this area may come from recent developments in fracture mechanics and in coal geochemistry

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

long chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments long chain n c37 c39 alkenones and alkyl alkenoates are biological markers for sediment inputs of algae from the class prymnesiophyceae which includes the coccolithophorids these compounds have been recognized in many recent and ancient marine sediments but in only a few living algal species notably the ubiquitous coccolithophorid emiliania huxleyi the proven value of long chain alkenones in palaeotemperature assessment prompts an evaluation of their sedimentary record especially their correspondence with coccolithophorid fossils in ancient marine sediments synthesis of available micropalaeontological and molecular data suggests that morphologically related species of the genera crenalithus dictyococcites emiliania gephyrocapsa pseudoemiliania and reticulofenestra all belonging to the family gephyrocapsaceae were potential biological sources of alkenones and alkyl alkenoates in marine sediments deposited since the eocene 45 ma the occurrence of alkenones in cenomanian and albian sediments devoid of nannofossils may be presumed to reflect contributions from ancestors of the gephyrocapsaceae although an investigation of cretaceous samples containing both coccoliths and alkenones would provide further evidence of this proposed correspondence the combination of palaeontological and molecular chemotaxonomic information offers a novel approach to the evaluation of the phylogenetic lineages that link living and extinct algae

discrete element modelling of deformation and damage of a roadway driven along an unstable goaf a case study abstract roadways driven alongside a previously extracted longwall panel goaf are a common situation in underground coal mining the unstable goaf can have a significant detrimental impact on the stability of the roadway this paper presents a combined srm udec trigon numerical approach to investigate the failure mechanism of a roadway driven alongside an unstable goaf the synthetic rock mass srm method is used to derive the rock mass properties and the newly developed udec trigon approach is used for simulating brittle fracture and consequent roadway damage the results indicate that the roadway suffers asymmetric damage characterized by a major rib convexity a severe floor heave and a relatively stable roof with limited fracturing this failure mechanism is consistent with field observations a quantitative evaluation of the damage around the roadway indicates that shear failure plays a major role in the roadway damage our study suggests that the proposed combination of srm and the udec trigon is well suited to the evaluation of failure mechanisms around underground coal mine excavations

data model comparison reveals key environmental changes leading to cenomanian turonian oceanic anoxic event 2 abstract the middle cretaceous was a period characterized by elevated sea floor spreading rates enhanced volcanism high atmospheric co2 levels warming temperatures and the peak eustatic highstand of the mesozoic two well known perturbations in the global carbon cycle mark this interval the cenomanian turonian oceanic anoxic event 2 oae2 and the mid cenomanian event mce although studies during the past two decades have arrived at a consensus that the caribbean large igneous province lip likely played a key role in triggering oae2 arguably the most significant perturbation of the late cretaceous the detailed environmental developments during the mid late cenomanian leading up to it have only recently been the focus of investigations this study based on previous studies of the middle cenomanian early turonian climate tectonics sea level and carbon isotope chemostratigraphy tests plausible environmental scenarios to explain the behavior of the middle cenomanian to early turonian carbon cycle via isotope mass balance calculation in a simple carbon cycle box model the model experiments successfully reproduce two distinctive features observed in the mid late cenomanian 13c curves 1 decoupling of 13ccarb and 13corg reflecting increasing isotope fractionation in response to steadily rising pco2 driven by enhanced volcanic degassing of mantle derived co2 which likely preceded the presumed peak volcanism of the caribbean lip and 2 a long lived secondary positive excursion that documents enhanced organic carbon burial in shallow shelf seas that expanded during global sea level rise and highstand we demonstrate a plausible combination of environmental forcings that pre conditioned the mid cretaceous ocean atmosphere system for a massive perturbation oae2

the central myanmar burma oil family composition and implications for source abstract geochemical characteristics of 31 miocene through eocene oils seeps an eocene coal and an eocene resin from the central myanmar burma basin system are examined the oils seeps vary widely in api gravity 8 52 sulfur concentration 26 3550 ppm 13 c 27 6 to 23 4 and molecular composition this variability is caused by varying amounts of biodegradation superimposed upon a single genetic oil family and the difference between aliphatic and aromatic hydrocarbon carbon isotope ratios i e 13 c arom 13 c aliph provides a useful gauge of the extent of biodegradation the projected geochemical characteristics of unaltered central myanmar oils are as follows a api gravity 35 37 b s 0 05 0 10 c 13 c aliph 27 8 to 27 6 d 24 ethylcholestanes are the dominant steranes and e 20s 24 ethyldiacholestane various bicadinanes and oleanane are present the ratio of 18 h 22 29 30 trisnorneohopane to 17 h 22 29 30 trisnorhopane t s t m is postulated as a maturity parameter and on this basis relative bicadinane concentration increases and the trans trans trans cis cis trans bicadinane ratio decreases with increasing thermal maturity in this oil set geologic arguments suggest a deep paleogene source for these oils two geochemical arguments that support this inference are a the occurrence of saturated and unsaturated c 15 and c 30 cadinane monomers and dimers in pyrolyzates of an eocene resin and the kerogen from an eocene coal and b identical compound specific carbon isotope ratios for selected isoprenoids and n alkanes in a typical central myanmar oil and the hydrous pyrolyzate expelled from an eocene coal we propose an eocene resinous shale coal source for these oils with the oldest eocene reservoirs filling first and the youngest miocene reservoirs filling last consistent with the observation that the least mature oils are present in the oldest reservoirs according to this model surface seepage and near surface oil could result from subsurface traps that are filled to spillpoint

structural effects on the strength of new zealand coal abstract to define the behaviour of rocks under stress certain material properties are required to characterise deformation and failure the laboratory unconfined compressive strength ucs and triaxial behaviour forms the basis of many failure criteria and pillar strength equations it has been well established that the ucs of rocks is greatly influenced by sample size and structural discontinuities this is particularly true for coal which has a microscale fracture pattern cleat throughout its fabric the aim of this study was to investigate the relationship between strength and structure and relate this to field performance results from laboratory strength tests with petrographic and thermal analysis were collated with other test data on the coal samples were selected from a thick sub bituminous coal seam in the waikato coal measures this coal is a relatively weak compared to strength data from published sources and it has a defined cleat system the coal was found to vary in composition throughout the seam section with strength differences partially attributed to material variations as well as preparation and structural controls the thick seams are mined by a modified room and pillar method which leaves slender yield pillars on retreat these pillars are essentially large scale ucs samples in the field the geometry of the pillars was recorded on completion of mining and the cleat was mapped where possible it was found that the laboratory results and the historical case study information correlated well with pillar strength formulae however when compared to the slender yield pillars it did not predict performance numerical modelling also failed to represent the observed behaviour this suggests a different mechanism is involved which is possibly structurally controlled where the intact strength of the coal appears to be less important than the structure and geometry of the excavation

topographic stress perturbations in southern davis mountains west texas 1 polarity reversal of principal stresses 1 we have applied a previously developed analytical stress model to interpret subsurface stress conditions inferred from acoustic televiewer logs obtained in two municipal water wells located in a valley in the southern davis mountains near alpine texas the appearance of stress induced breakouts with orientations that shift by 90 at two different depths in one of the wells is explained by results from exact solutions for the effects of valleys on gravity and tectonically induced subsurface stresses the theoretical results demonstrate that above a reference depth termed the hinge point a location that is dependent on poisson s ratio valley shape and magnitude of the maximum horizontal tectonic stress normal to the long axis of the valley horizontal stresses parallel to the valley axis are greater than those normal to it at depths below this hinge point the situation reverses and horizontal stresses normal to the valley axis are greater than those parallel to it application of the theoretical model at alpine is accommodated by the fact that nearby earthquake focal mechanisms establish an extensional stress regime with the regional maximum horizontal principal stress aligned perpendicular to the valley axis we conclude that the localized stress field associated with a valley setting can be highly variable and that breakouts need to be examined in this context when estimating the orientations and magnitudes of regional principal stresses

origin and diagenetic transformations of c25 and c30 highly branched isoprenoid sulphur compounds further evidence for the formation of organically bound sulphur during early diagenesis abstract a number of c25 and c30 highly branched isoprenoid hbi sulphur compounds e g thiolanes 1 oxo thiolanes thiophenes and benzo b thiophenes with 2 6 10 14 tetramethyl 7 3 methylpentyl pentadecane and 2 6 10 14 18 pentamethyl 7 3 methylpentyl nonadecane carbon skeletons were identified in sediments ranging from holocene to upper cretaceous these identifications are based on mass spectral characterisation desulphurisation and in some cases by comparison of mass spectral and relative retention time data with those of authentic standards the presence of unsaturated c25 and c30 hbi thiolanes in a recent sediment from the black sea age 3 6 10 3 a strongly supports their formation during early diagenesis the co occurrence of hbi polyenes c25 and c30 and unsaturated hbi thiolanes c25 and c30 possessing two double bonds less than the corresponding hbi polyenes in this recent sediment testifies to the formation of unsaturated hbi thiolanes by a reaction of inorganic sulphur species with double bonds of the hbi polyenes furthermore a diagenetic scheme for hbi sulphur compounds is proposed based on the identification of hbi sulphur compounds in sediment samples with different maturity levels

occurrence of polycadinene in fossil and recent resins abstract dammars produced by dipterocarpaceae growing in southeast asia are partly composed of a macromolecule with a polycadinene structure this polymer is the precursor of many specific compounds encountered in crude oils and sediment extracts from south asia until recently there was no evidence for a more widespread geographical occurrence of this resinous polymer using different pyrolysis methods it is shown that the polymers present in a resinite from utah usa and in resins contained in resin canals of eocene fossil fruits from germany and england are also polycadinenes the fossil fruits were undoubtedly produced by ancient representatives of mastixioid cornaceae a group of plants which was widespread in the tertiary of europe and north america and which is not related to dipterocarpaceae these findings extend the known occurrence and origin of the sesquiterpenoid type resin polymer it is to be expected that catagenetic products of these resin polymers should be present in oils coals and sediment extracts from areas outside southeast asia

hydrologic properties of coal beds in the powder river basin montana i geophysical log analysis as part of a multidisciplinary investigation designed to assess the implications of coal bed methane development on water resources for the powder river basin of southeastern montana six wells were drilled through paleocene age coal beds along a 31km east west transect within the tongue river drainage basin analysis of geophysical logs obtained in these wells provides insight into the hydrostratigraphic characteristics of the coal and interbedded siliciclastic rocks and their possible interaction with the local stress field natural gamma and electrical resistivity logs were effective in distinguishing individual coal beds full waveform sonic logs were used to determine elastic properties of the coal and an attendant estimate of aquifer storage is in reasonable agreement with that computed from a pumping test inspection of magnetically oriented images of the borehole walls generated from both acoustic and optical televiewers and comparison with coal cores infer a face cleat orientation of approximately n338e in close agreement with regional lineament patterns and the northeast trend of the nearby tongue river the local tectonic stress field in this physiographic province as inferred from a nearby 1984 earthquake denotes an oblique strike slip faulting regime with dominant east west compression and north south extension these stress directions are coincident with those of the primary fracture sets identified from the televiewer logs and also with the principle axes of the drawdown ellipse produced from a complementary aquifer test but oblique to apparent cleat orientation consequently examination of these geophysical logs within the context of local hydrologic characteristics indicates that transverse transmissivity anisotropy in these coals is predominantly controlled by bedding configuration and perhaps a mechanical response to the contemporary stress field rather than solely by cleat structure published by elsevier b v

petroleum source bed evaluation of tertiary niger delta reply a total of 63 sidewall and drill cutting shale samples obtained from a depth slice of 800 to 3650 m in two onshore and two offshore wells located respectively in the eastern and western niger delta basin nigeria were analyzed for organic matter type concentration and thermal maturity dominant sedimentary kerogens were the humic and mixed types organic carbon contents of the sediments ranged from 0 4 to 4 4 and the degree of thermal evolution as evidenced by vitrinite reflectance r sub 0 odd even ratios oer 2c sub 29 c sub 28 c sub 30 and variations of the ratios of the concentration of soluble organic matter to total organic carbon content som toc were within the ranges 0 2 to 0 7 4 0 to 1 0 and 10 to 240 respectively on the basis of the variation of the maturation parameters the onset of mature source beds in the onshore and offshore delta were delimited at approximately 3375 and 2900 m respectively the inferred threshold temperature was about 95 sup 0 c the results of the present study support the hypothesis that the main source beds of the niger delta basin are the deeply buried paralic or paralic marine facies

quantitative diamondoid analysis indicates oil cosourcing from a deep petroleum system onshore niger delta basin the niger delta basin is one of the most prolific hydrocarbon provinces in the world yet the origin of the vast amounts of oil and gas found in the numerous sub basins across the delta remains contested a total of 180 oil samples from more than 40 oil fields in the niger delta were analyzed by gas chromatography gc gc mass spectrometry gc ms and selected samples by gc tandem mass spectrometry gc msms the interpreted thermal maturity and source depositional environments of these hydrocarbons show significant variation depending on the components analyzed and allow no clear correlation to a single source rock but rather imply extensive mixed contributions diamondoid hydrocarbon parameters were used for the first time on these paleogene neogene reservoired oils to investigate source thermal maturity and mixing effects and to perform cross correlations of these oils the diamondoid abundances and distributions support the hypothesis of co sourcing of oil from a thermally cracked sub delta type ii marine source which was then mixed with oils of relatively lower maturities in the paleogene neogene reservoirs future geochemical interpretations should treat the niger delta oils as potential mixtures of oils of variable maturities from different sources often with the most important source biomarkers depleted because of the extent of thermal cracking

geochemical characteristics of tertiary coal bearing source rocks in xihu depression east china sea basin abstract this study aims at investigating hydrocarbon generation potential and biological organic source for the tertiary coal bearing source rocks of pinghu formation middle upper eocene in xihu depression east china sea shelf basin another goal is to differentiate coal and mudstone with respect to their geochemical properties the coal bearing sequence has a variable organofacies and is mainly gas prone the coals and carbonaceous mudstones in comparison with mudstones have a higher liquid hydrocarbon generation potential as reflected by evidently higher hi values averaging 286 mg hc g c and h c atomic ratios round 0 9 the molecular composition in the coal bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes dominant c29 sterane over c27 and c28 homologues and high amount of terrigenous related aromatic biomarkers such as retene cadalene and 1 7 dimethylphenanthrene indicating a predominantly terrigenous organic source the source rocks show high pr ph ratios ranging mostly from 3 5 to 8 5 and low mdbts mdbfs ratios

review of plausible chemical migration pathways in australian coal seam gas basins abstract coal seam gas csg or coal bed methane production has grown exponentially in australia over the last two decades with currently nearly 7000 productive wells and another 18 750 wells planned over the next five to ten years to address concerns over environmental contamination by hydraulic fracture fluids hff attributed to i incidents involving poor surface handling of hff and other fluids with potential migration pathways in soil and shallow groundwater and ii leakage pathways arising from hff injection into coal seams and unintended migration of these chemicals the national assessment of chemicals associated with coal seam gas extraction in australia the assessment was undertaken the assessment included a review of international studies on unconventional gas migration pathways to provide prior knowledge and comparison for use in the australian study the international literature highlighted that accidents with hff were mainly due to surface operations and included leaking equipment and spills contamination risks of groundwater from hydraulic fracturing itself were found to be very small based on analysis of micro seismic and groundwater hydrochemistry data geologic modelling of vertical fracture growth further reveals a low risk of leakage pathways developing in aquifers confined by deep shale formations this is due to limitations on the fracture growth vertically across aquitards often hundreds of meters thick retention within the shale of limited amounts of injected fluid and preferential fracture growth at shallow depths in the horizontal direction these arguments are broadly applicable to australian csg basins however important differences exist such as the reduced thickness in australia of the aquitards that separate the targeted gas resource from groundwater also hydraulic fracturing in australian coal seams is practised only when permeabilities are too low for gas extraction to be economical without stimulation from the nearly 10 000 csg wells drilled in the bowen and surat basins in queensland only 6 have received hydraulic fracturing to date the reduced risk of leakage pathways developing during csg production in australian basins is further corroborated by geologic criteria based on modelling and observations criteria include encountering certain favourable conditions during drilling injection i e i interfaces such as natural fractures faults and bedding planes which promote offsetting and branching or rock layers with higher fracture toughness causing the cessation or reduction in fracture growth ii narrow fractures due to a relatively higher elastic modulus leading to higher viscous flow loss iii high permeability layers and iv overlying layer s with a higher confining stress in addition to the leakage pathways considered in north american shale gas basins involving i pre existing fractures and faults or ii flow up the production well due to poor casing or cementing plausible chemical migration pathways in australian csg basins are due to iii connectivity via a fracture in or extended out of the coal seam formation between csg wells and water bores co located in the same formation and iv poor integrity water bores enhancing inter aquifer connectivity these plausible pathways are described and used in subsequent work as the basis of risk assessments for contamination at the local and regional scale

the biomarker composition of some crude oils from sumatra abstract crude oils from the north central and south sumatra basins have been analysed using gc and gc ms techniques and the biomarker compositions of the crude oils have been used to classify the samples into three types one oil from the north sumatra basin contained 3 methylhexadecane 2 methylhexadecane pristane and phytane in similar abundances regular steranes and 24 n propylcholestanes indicative of an algal contribution a series of 30 norhopanes and an absence of plant derived pentacyclic triterpanes these features have been interpreted as indicating a marine carbonate depositional setting two crude oils from the central sumatra basin are waxy crudes with abundant botryococcane pristane phytane and abundant 4 methyl 24 ethylcholestanes relative to dinosteranes these features suggest a brackish lacustrine depositional setting one light oil from the north sumatra basin and two crude oils from the south sumatra basin have abundant pristane compared with n c 17 and a high pristane phytane value the saturated polycyclic compounds are dominated by bicadinanes and other pentacyclic triterpanes of land plant origin the presence of abundant oleananes in these samples has been interpreted as evidence for deltaic near shore depositional setting these results show that crude oils from the sumatran region have source rocks with a range of depositional environments however the major oil fields are associated with lacustrine source rocks

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

mid chain branched mono and dimethyl alkanes in hot spring cyanobacterial mats a direct biogenic source for branched alkanes in ancient sediments hot spring cyanobacterial mats from yellowstone national park u s a and the orakei korako thermal area new zealand have been found to contain suites of monomethyl alkanes compounds frequently reported in cultured and natural populations of cyanobacteria the complete range of possible structural isomers for mid chain branching for c17 c18 and c16 c18 alkanes occurs in the two mats respectively several c19 dimethyl and c20 multibranched alkanes were also observed as major hydrocarbons of the orakei korako mat the recognition of series of mid chain branched alkanes in modern cyanobacterial mats suggests that their occurrence in ancient sediments may reflect direct biogenic contributions rather than formation by diagenetic processes

onocerane and other triterpenoids in late cretaceous sediments from the upper benue trough nigeria tectonic and palaeoenvironmental implications abstract the aliphatic hydrocarbon bitumen fraction has been investigated in late cretaceous outcrop samples from the upper benue trough inundated by the sea only during the maximum mid cretaceous transgression thermal maturity in nearly all formations is pre oil window indicating only limited mainly tertiary burial the santonian deformation a significant thermal influence to the south west appears to have had little effect here onocerane i is the dominant triterpenoid in the pindiga formation but is absent elsewhere its origin is uncertain but it appears to be associated with deposition in a restricted basin possibly a brackish lagoon receiving dominantly terrestrial organic input a review of possible natural product precursor compounds suggests onoceradiene from a fern like plant was a likely source even carbon number predominance of n alkanes in the range c 16 to c 22 in some formations is tentatively interpreted to indicate hypersalinity

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

tertiary oils from upper assam basin india a geochemical study using terrigenous biomarkers abstract the upper assam basin in northeast india is a tertiary sub basin of the assam arakan basin hydrocarbons are present in the langpar formation upper palaeocene lakadong member of the sylhet formation lower eocene and the barail oligocene tipam lower miocene and girujan middle miocene formations in the basin a detailed study to understand the nature and origin of the oils from different stratigraphic horizons using terrigenous and other biomarkers has been carried out further the variation in maturities of oils occurring in different stratigraphic horizons has also been studied the study shows that rearranged oleananes oleananes and bicadinanes are present in these oils implying land plant input to their source rocks the oils have been classified into different groups using ratios of rearranged oleananes oleananes bicadinanes and steranes indicating presence of multiple source rocks in the basin with subtle variation in characteristics maturity studies show that oils from younger horizons barail tipam and girujan are more mature than oils from older horizons langpar and lakadong there is an apparent mismatch in maturity of oils as measured by different biomarker maturity parameters this is due to the mixing of two different charges of oils having different maturities and generated from two different source rock kitchens in the same reservoir principal component analysis pca of biomarker data has also been able to classify the oils into various groups a new parameter has been developed using ratios of rearranged oleananes for determining maturity of these oils

fault type predictions from stress distributions on planetary surfaces importance of fault initiation depth faults on planetary surfaces initiate at depth where stresses due to the weight of overburden are important consequently the prediction of fault type from calculated stresses at depth can yield different faults than those predicted using the surface criteria commonly employed in geophysical models for elastic plate flexure models of mascon loading on the moon stresses calculated at the surface predict that the most likely faulting is strike slip for which there is no direct evidence at a distance from the basin center where grabens are found modifying these plate flexure calculations to account for the weak surface layer of ejecta megaregolith 1 3 km thick that overlies the relatively strong lunar lithosphere results in model stresses in the outer layers of the moon tens of bars that are an order of magnitude lower than in the lithosphere hundreds of bars because faults bounding lunar grabens initiate at the mechanical discontinuity between the megaregolith and lithosphere and because the reverse faults likely responsible for wrinkle ridges probably initiate at the basalt basin floor contact 0 5 2 km deep model stresses must be calculated at these depths superposing nonisotropic stresses due to the weight of the overburden at the depths of these mechanical discontinuities with plate flexure model stresses correctly predicts maximum stress differences in an interior zone of expected wrinkle ridges surrounded by a zone of concentric normal faults or grabens and effectively eliminates the strike slip zone in agreement with observations the absence of strike slip faults from almost all planetary and satellite surfaces may be explainable if lithospheric deformation model stresses are calculated at important shallow crustal mechanical discontinuities where the maximum compressive stress is vertical thereby favoring the formation of normal faults if true mechanical discontinuities in the shallow crusts of planets and satellites play an extremely important and hitherto unrecognized role in the formation of structures observed on their surfaces

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

integrated reservoir petrophysical and seismic simulation of co2 storage in coal beds in this paper we present results of an integrated simulation study to assess the effectiveness of seismic imaging for monitoring co2 sequestration we considered two scenarios in the first injected co2 remained confined within a shallow coal formation in the second the sequestered co2 gas leaked through a semi permeable shale layer to an overlying sand unit sealed above in both scenarios the co2 injection process resulted in enhanced production of coal bed methane the reservoir and seismic simulations required the construction of 3d geologic and facies models the estimations of seismic velocities based on rock physics correlations and the development of geostatistical dual porosity reservoir descriptions of the coal and overlying shale and sand units we ran the 3d reservoir simulations with gem 2008 10 an equation of state compositional reservoir simulator from computer modeling group with the capability to model adsorption of injected co2 in coal desorption of ch4 and matrix shrinkage swel

coal cleat domains and domain boundaries in the allegheny plateau of west virginia regional face cleats cutting pennsylvanian and permian coal seams in the allegheny plateau of west virginia can be divided into domains separated by boundaries that are sharply defined along most of their lengths domains and domain boundaries are established based on cleat trends number of regional cleat sets and relative chronology of cleat set development regional cleats of each set show a common trend and abutting relationships between multiple sets within a domain describe a progressive history of changing stress fields and cleat development boundaries dividing the in situ directions of horizontal principal stress are coincident with cleat domain boundaries suggesting a common and persistent controlling factor uniform trends of face cleats within domains and ab upt changes in cleat signature across domain boundaries can be spatially related to regional basement structures and a depositional hinge line within the coal bearing and underlying mississippian rocks in addition fold structures in coal and underlying sedimentary rocks across the allegheny plateau commonly terminate or change trend abruptly at joint domain boundaries in some cases regions of common fold trends in coal bearing rocks are contained within specific domains face cleat trends commonly differ from joint trends in rocks immediately bounding coal seams however one domain boundary in coal can be traced into mississippian rocks through the unconformity at the base of the pennsylvanian section in this case mississippian and pennsylvanian joint trends differ it follows tha joint domain boundaries can extend downward through rocks of different lithologies as well as coincide with conformable and unconformable stratigraphic boundaries

environmental and vegetational changes recorded in sedimentary leaf wax n alkanes across the cretaceous paleogene boundary at loma capiro central cuba abstract the stable carbon isotopic compositions 13c and chain length distribution acl and n c31 n c29 n c31 of sedimentary leaf wax n alkanes were investigated across the cretaceous paleogene k pg boundary at loma capiro central cuba to reconstruct paleoenvironmental changes that are recorded in terrestrial higher plants the stratigraphic profiles of the n alkane 13c values show a negative excursion in the lowermost paleocene although its magnitude is much smaller 0 3 than the global signals 1 5 to 2 0 in the surface ocean atmospheric carbon reservoir relations between the n alkane 13c values and the c31 c29 c31 ratios exhibit two different trends suggesting that our 13c records are likely affected by two types of paleoenvironmental factors in addition to the 13c variations in the exogenous carbon reservoir rare occurrence of terrigenous organic matter that is usually transported by rivers suggests that the n alkanes at loma capiro are likely to have been transported by trade winds which recorded paleoenvironmental conditions of the northwestern part of the african continent the n alkane 13c values show a parallel decrease with the acl and c31 c29 c31 values in the first 37 000 yr following the k pg boundary such decreases are consistent with plant physiological responses to reduced net evaporation suggesting a possible influence of the impact induced warm humid condition in the early paleocene in contrast the n alkane 13c values are negatively correlated with the c31 c29 c31 ratios from 40 000 to 67 000 yr after the k pg boundary this time period matches well with that required for the recovery of terrestrial floras from the k pg mass extinction to those with diversity equivalent to the late cretaceous suggesting that the n alkane signals are also likely affected by the plant diversification process after the mass extinction

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

carbon and hydrogen isotopic compositions of n alkanes as a tool in petroleum exploration compound specific isotope analysis csia of individual organic compounds is a powerful but underutilized tool in petroleum exploration when integrated with other organic geochemical methodologies it can provide evidence of fluid histories including source maturity charge history and reservoir processes that can support field development planning and exploration efforts the purpose of this chapter is to provide a review of the methodologies used for generating carbon and hydrogen isotope data for mid and high molecular weight n alkanes we discuss the factors that control stable carbon and hydrogen isotope compositions of n alkanes and related compounds in sedimentary and petroleum systems and review current and future applications of this methodology for petroleum exploration we discuss basin specific case studies that demonstrate the usefulness of csia either when addressing particular aspects of petroleum exploration e g charge evaluation source rock oil correlation and investigation of maturity and in reservoir processes or when this technique is used to corroborate interpretations from integrated petroleum systems analysis providing unique insights which may not be revealed when using other methods csia of n alkanes and related n alkyl structures can provide independent data to strengthen petroleum systems concepts from generation and expulsion of fluids from source rock to charge history connectivity and in reservoir processes

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

state of lithospheric stress and borehole stability at deep sea drilling project site 504b eastern equatorial pacific hole 504b in the eastern equatorial pacific is the deepest hole to penetrate oceanic basement extending more than 1500 m beneath the seafloor two borehole televiewer bhtv logs were obtained in this hole one through the upper 1000 m of basement during deep sea drilling project leg 83 and the other extending an additional 260 m deeper into the crust during ocean drilling program leg 111 the two bhtv records have been combined and processed in terms of both acoustic amplitude and travel time in order to evaluate the extent and distribution of rock failure along the borehole wall a histogram of borehole enlargements versus azimuth depicts a dominant breakout azimuth of n122 5 e which corresponds to the direction of minimum principal stress sh and correlates well with stress orientations inferred from solutions to regional earthquake focal mechanisms furthermore the bimodality of this histogram with a secondary mode orthogonal to sh indicates that a significant number of enlargements are coalesced tensile fractures occurring along the orientation of sh the maximum principal stress the appearance of this orthogonal bimodal distribution suggests that the regional horizontal stress field is highly anisotropic a condition supported by seismic data which show all of the earthquakes in the area to be strike slip the frequency of borehole enlargements increases with increasing depth and depicts a systematic structural deterioration of the well bore the tensile fractures along the sh azimuth contribute to this degradation and appear to be induced by thermal stresses due to the injection of cold water into hot rock the frequency of these extensional features does not increase with depth rather their appearances can be directly correlated with shipboard efforts at deliberately cooling the well and or with the sudden resumption of drilling after the hole had been allowed to reequilibrate thermally for several days these latter borehole enlargements are more pronounced then those commonly associated with hydraulic fracturing the mechanisms for fracture initiation and growth based upon temperature contrasts between the well bore fluid and the adjacent rock may enhance rock failure

prediction of compressional wave velocity using regression and neural network modeling and estimation of stress orientation in bokaro coalfield india velocity of compressional wave v p of coal and non coal lithology is predicted from five wells from the bokaro coalfield cf india shear sonic travel time logs are not recorded for all wells under the study area shear wave velocity vs is available only for two wells one from east and other from west bokaro cf the major lithologies of this cf are dominated by coal shaly coal of barakar formation this paper focuses on the a relationship between vp and vs b prediction of vp using regression and neural network modeling and c estimation of maximum horizontal stress from image log coal characterizes with low acoustic impedance ai as compared to the overlying and underlying strata the cross plot between ai and vp vs is able to identify coal shaly coal shale and sandstone from wells in bokaro cf the relationship between vp and vs is obtained with excellent goodness of fit r 2 ranging from 0 90 to 0 93 linear multiple regression and multi layered feed forward neural network mlfn models are developed for prediction vp from two wells using four input log parameters gamma ray resistivity bulk density and neutron porosity regression model predicted vp shows poor fit from r 2 0 28 to good fit r 2 0 79 with the observed velocity mlfn model predicted vp indicates satisfactory to good r2 values varying from 0 62 to 0 92 with the observed velocity maximum horizontal stress orientation from a well at west bokaro cf is studied from formation micro imager fmi log breakouts and drilling induced fractures difs are identified from the fmi log breakout length of 4 5 m is oriented towards n60 w whereas the orientation of difs for a cumulative length of 26 5 m is varying from n15 e to n35 e the mean maximum horizontal stress in this cf is towards n28 e

determination of vertical hydraulic conductivity of aquitards in a multilayered leaky system using water level signals in adjacent aquifers summary this paper presents a methodology for determining the vertical hydraulic conductivity k v of an aquitard in a multilayered leaky system based on the harmonic analysis of arbitrary water level fluctuations in aquifers as a result k v of the aquitard is expressed as a function of the phase shift of water level signals measured in the two adjacent aquifers based on this expression we propose a robust method to calculate k v by employing linear regression analysis of logarithm transformed frequencies and phases the frequencies where the k v is calculated are identified by coherence analysis the proposed methods are validated by a synthetic case study and are then applied to the westbourne and birkhead aquitards which form part of a five layered leaky system in the eromanga basin australia

well bore breakouts and in situ stress the detailed cross sectional shape of stress induced well bore breakouts has been studied using specially processed ultrasonic borehole televiewer data we show breakout shapes for a variety of rock types and introduce a simple elastic failure model which explains many features of the observations both the observations and calculations indicate that the breakouts define relatively broad and flat curvilinear surfaces which enlarge the borehole in the direction of minimum horizontal compression this work supports the hypothesis that breakouts result from shear failure of the rock where the compressive stress concentration around the well bore is greatest and that breakouts can be used to determine the orientation of the horizontal principal stresses in situ

occurrence of 20r and 20s δ8 14 and δ14 5α h sterenes and the origin of 5α h 14β h 17β h steranes in an immature sediment abstract series of 20r and 20s 8 14 and 145 h sterenes have been identified in an immature marl from a hypersaline deposit northern apennines italy by co injection studies with authentic compounds these alkenes co occur with 13 17 5 h spirosterenes and transient 20r and 20s 14 5 h 17 h sterenes the source of these isomeric steroid alkenes is probably 7 and 8 14 5 h sterols via 2 7 2 8 14 and 2 14 5 h steradienes reduction processes in the sediment via the 14 5 h 17 h sterenes can give rise to the c 20 isomeric 5 h 14 h 17 h steranes present in anomalously high relative abundances from a thermal maturity viewpoint this diagenetic pathway is supported by laboratory rearrangement hydrogenation experiments of 5 h cholest 7 ene and from considerations of carbon number distributions of various steroid hydrocarbons in the sediment extract

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

effects of chemical preparation protocols on δ13c values of plant fossil samples abstract for over a half century studies of the stable carbon isotope compositions of plant fossils have provided noteworthy conclusions about the evolution of earth climate however different preparation protocols were used prior to carbon isotope analysis of plant fossils and the accuracy of measured 13c 12c ratios may strongly depend on them we have applied the most frequently used chemical preparation protocols to frenelopsis leaves from four cretaceous localities of western europe our results indicate that procedures to extract plant fossils from sediments are not adequate to retrieve the original plant 13c values the use of schulze s reagent to bleach cuticles in paleobotany allows misleading 13c values of specimens from a same locality with positive shifts of up to 13 6 and increases intra specimen and inter specimen variances sample treatment involving hcl or hcl hf gives consistent 13c mean values for a same leaf and for leaves from a same sedimentary bed however although hf does not provide any advantage in removing potential contamination sources it alters plant fossil tissues slightly increasing the intra and inter leaf variances of 13c values our results indicate that processing plant fossils with hcl only is the most accurate and conservative way to retrieve original 13c values

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

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

tertiary deltaic and lacustrine organic facies comparison of biomarker and kerogen distributions abstract biological marker and kerogen compositional data in tertiary deltaic and lacustrine settings were compared and contrasted the two settings are represented by a coals and organic carbon rich shales in a ick deltaic sequence from the far east constituting three distinct organic facies and b humic coals and spropelic oil shales in a restricted intermontane freshwater lacustrine sequence from western montana u s a constituting two distinct organic facies wedistinguish the organic facies in each depositional setting by systematic differences in gross compound class distributions kerogen and infrared spectral characteristics molecular character of pyrolyzates sterane carbon number distribution and sterane hopane ratios the kerogens of the three deltaic organic facies are characterized by varying quantities of vitrinite resinite sporinite cutinite and fluorescent amorphinite triterpane distributions reveal numerous terrigenous compounds including oleanane oleanenes and unidentified c 30 presumably resin derived components the two organic facies of the freshwater lacustrine setting are distinguishedased upon either a vitrinite or an alganite fluorescent amorphinite predominance in the kerogen numerous characteristics facies related markers are also present including dehydroabietane land plant resins and 4 methylsteranes perhaps from freshwater dinoflagellate input the available molecular and petrographic data are evaluated and characteristics are proposed for distinguishing five organic facies of these two depositional settings the successful simultaneous use of molecular geochemistry and organic petrography in this study provides a format for refining the organic facies concept

dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum abstract the steroidal alkanes of a selection of sediments and oils have been examined by gc ms with multiple metastable reaction monitoring specific 4 methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates an immature marine oil shale and two mature marine oils of triassic to early cretaceous age contained high concentrations of c30 steranes comprising desmethyl 24 ethyl 4 methylcholestane and 4 23 24 trimethylcholestane dinosterane isomers an immature non marine oil shale and two non marine oils of cretaceous to eocene age contained stereoisomers of 24 ethyl 4 methylcholestane as the dominant c30 steranes reaction monitoring analyses in gc ms are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

using geological strength index gsi to model uncertainty in rock mass properties of coal for cbm ecbm reservoir geomechanics abstract the use of geostatistics has become an important concept to characterize uncertainty in reservoir simulations only recently has the concept been applied to geomechanics and coupled reservoir geomechanical simulations the work presented here describes how the geological strength index gsi is used to represent the fractured reservoir properties of a coalseam reservoir and link changes in flow properties with stress changes as well as to strength and deformation the approach is demonstrated by using a spherical geostatistical model to create 11 gsi realizations and one constant gsi model two years of primary methane production and then 3 months co 2 storage were simulated using each of the 12 models as inputs much higher cumulative gas and gas production rate profiles were observed for models with a mean gsi below 80 than the 80gsi model all models above 80 gsi show much lower cumulative gas and gas production rates than the 80gsi model the same trend held true for the co 2 injection component of the operation stress path profiles for three monitoring points in the reservoir showed large variability but similar paths whereas monitoring points in the overlying caprock showed very low variability for each realization

oleanane parameter verification by quantitative study of the biomarker occurrence in sediments of the niger delta abstract the variation of the absolute concentration of oleananes in three selevted sedimentary columns of the tertiary niger delta is paralleled by the corresponding oleanane parameter op profile thereby confirming that the latter can be utilized for estimating the relative contribution of terrigenous organic matter it is shown that op features a dynamic range especially at the oil generative window ogw and can precisely delimit the top of the ogw which for the niger delta is shown to coincide approximately with the 80 c isotherm and ro 0 55 this study provides the first direct evidence of the inadequacy of vitrinite reflectance as a maturity parameter for type iii kerogen furthermore based on the new findings an alternative model for oleanene oleanane interconversions in the geosphere is proposed

lineaments and their tectonic implications in rocky mountains and adjacent plains region abstract two orthogonal sets of lineaments in phanerozoic rocks of the rocky mountains and adjacent plains region probably reflect recurrent structural movement along corresponding fractures in the underlying igneous and metamorphic rocks the lineaments seem to have been primarily paleotopographic features that affected the depositional and erosional margins thicknesses and the distribution of lithofacies of phanerozoic strata one set is oriented near the cardinal points of the compass approximately n5 15 e and n75 85 w the other set is oriented diagonally about n50 60 e and n30 40 w at small scales the crosscutting lineaments of either set suggest primarily vertical movements of rectangular blocks along through going rectilinear fractures in the basement rocks at larger scales the differential movement of these blocks apparently was propagated upward through the strata and formed a variety of structures many of which are en echelon blocks in the region moved at different times and they commonly rotated about horizontal axes as indicated by lateral differences in rates of associated sedimentation and by structural features along the lineaments throughout most of the phanerozoic the movements seem to have been mainly along the diagonal set northeast northwest of lineaments but the cardinal set north south east west also influenced the development of laramide structures and the present landscape in the rocky mountain region the structural stresses which were released along the two sets of lineaments may reflect plate movements and they probably are related to orogenies caused either by plate collisions or by rifting and continental fragmentation end of article last page 1349

organic carbon as a palaeoenvironmental indicator in the marine realm recent developments in biogeochemistry have made accessible all information currently known to be present in sedimentary organic compounds i e the carbon skeleton structure the positions of functional groups and stable carbon isotope ratios this combined information has strengthened the applications of sedimentary organic compounds as biomarkers and palaeoenvironmental indicators this review summarizes the most important biomarkers and their applications in reconstructing marine palaeoenvironments and processes the marine environment is characterized by the combined presence of specific compounds such as organic sulphur compounds dinosteroids 24 n propylsteroids even in trace amounts high amounts of c hbi hydrocarbons and the absence of long chain n alkanes with odd over even predominance bicadinanes and specific higher plant triterpenoids e g oleanane furthermore palaeoenvironmental conditions such as photic zone anoxia hypersalinity microbial sulphate reducing activity algal blooming palaeo upwelling and palaeo surface seawater temperature are indicated by molecular and or isotopic characteristics biomarkers from terrestrial sources are included because land derived organic matter is an important contributor to coastal and shallow marine environments a short case study within a holocene terrestrial marine setting florida bay usa is also presented to illustrate the reconstruction of transgressive regressive trends using selected organic compounds

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

numerical modelling and analysis of the influence of local variation in the thickness of a coal seam on surrounding stresses application to a practical case abstract one of the factors with the most influence in the carrying out of underground coal mining work is the stress state especially when such work is carried out at great depths one of the mining methods in which the influence of stresses becomes most patent is that of sublevel caving for that reason a variety of authors have studied many of the causes which condition the stress state of mining work of this kind at a general level however diverse types of conditioning factors exist at a local level that may substantially vary recorded pressures in the surroundings of the workings using numerical models this paper analyses the specific case of a coal seam mined by the sublevel caving method at a depth of 1000 m which suffers significant increases in stress and major deformations in certain advance headings as a result of variations in the geometry and dimensions of the load itself in particular thinning the results of the research carried out were validated by measuring the stresses in the area under study furthermore on the basis of a retrospective analysis of what was observed in the mine another series of predictive models were analyzed to establish the existing relation between the increase in stress due to thinning of the seam and the depth at which such thinning is situated

groundwater management and coal bed methane development in the powder river basin of montana summary coal bed methane cbm development will eventually pump more than 124 000 ha m of groundwater or more than 40 of the recharge from the coal seam and sandstone aquifers of the montana portion of the powder river basin prb this will relieve the hydrostatic pressure by causing a drawdown in the potentiometric surface and drawing groundwater from storage and natural discharges to release the methane gas a numerical groundwater flow model simulated drawdown that will exceed 90 m in the middle of the cbm fields with 6 m drawdown extending up to 29 km from the fields simulation results indicate that river flux will decrease up to 40 and drawdown will encompass hundreds of wells and springs recovery requires up to 45 years for significant decreases in river flux to recover and is not complete for 200 years cbm development impacts can be mitigated in two ways first reinjecting produced water into depleted coal seams would replenish the lost storage so that recovery would draw less groundwater from long distances second rapid infiltration basins near potentially affected rivers could decrease the short term river flow depletion modeled artificial recharge replaced up to 4000 ha m of deficit in the depleted coal seams and is a feasible option for mitigating some effects of cbm development reinjection would be more effective if the development period were lengthened

thiophenic biomarkers for palaeoenvironmental assessment and molecular stratigraphy reconstruction of ancient depositional environments is an important objective in the earth sciences the complex assemblages of organic molecules in sediments include compounds that can be related to known biochemicals produced by specific biota from well defined habitats1 3 and these chemical fossils are applied frequently to reconstruct palaeoenvironments especially in studies of organic and petroleum geochemistry and in chemical oceanography most of the compounds used in this way are hydro carbons2 4 although oxygenated for example alcohols acids and ketones and nitrogen containing for example porphyrins compounds have also been applied successfully1 2 here we report on the use of organic sulphur compounds as geochemical tools for palaeoenvironmental and stratigraphic assessment depth profiles of specific sulphur compounds related to certain organisms show significant variations reflecting changes both in sources of organic matter and in physical conditions such as salinity of the depositional environment in a number of cases these variations are not otherwise revealed by changes in lithology geochemical bulk data and or absolute and relative amounts of hydrocarbon biological markers moreover several organic sulphur compounds reveal the presence of unprecedented biochemicals in these palaeoenvironments

formation of ultralaminae in marine kerogens via selective preservation of thin resistant outer walls of microalgae abstract transmission electron microscopy tem observations recently revealed the common occurrence of very thin lamellar structures termed ultralaminae in kerogens from source rocks and oil shales so far considered as amorphous ultralaminae in lacustrine kerogens were shown to derive from the selective preservation of the algaenans occurring in the very thin outer walls of various freshwater chlorophyceae the chemical correlation between such algaenans and fossil lacustrine ultralaminae was chiefly based on the production on pyrolysis of n alkylnitriles with a typical distribution bimodal maxima at c 28 and c 16 the origin of marine ultralaminae is investigated in this work to this end spectroscopic and pyrolytic studies were carried out on i the algaenan forming the very thin outer walls of nanochlorum eucaryotum an extant marine chlorophycea and ii two ultralaminae containing marine kerogens from the lower toarcian shales of paris basin fecocourt and bray a high contribution of polymethylenic chains probably linked via ehter bridges was observed in these bio and geopolymers furthermore on pyrolysis they afforded the same n alkylnitriles with the same distribution unimodal maximum at c 13 lack of c 17 compounds fossil ultralaminae in marine kerogens therefore derive from the selective preservation of the algaenan composed very thin outer walls of marine chlorophyceae such as n eucaryotum algaenans from marine and freshwater chlorophyceae and therefore marine and lacustrine ultralaminae should be characterized by sharply distinct n alkylnitrile distributions

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

numerical investigation of the scale effect and anisotropy in the strength and deformability of coal abstract the decrease in strength and stiffness of coal with increase in specimen size has long been recognized as scale effect in this study a synthetic rock mass srm approach has been used to investigate this scale effect and the anisotropy of coal a discrete fracture network dfn for the coal was created and then embedded into bonded particle models to form a range of varying size of srm coal specimens unconfined compression tests on the srm specimens showed that the srm approach is capable of quantitatively reproducing the dependency of the strength and stiffness on the size of the coal specimens the strength and stiffness anisotropy of coal can also be reproduced the numerical results are shown to be in good agreement with published laboratory and field test results

dinosteranes 4 23 24 trimethylsteranes and other biological markers in dinoglagellate rich marine sediments of rhaetian age abstract alkane biological marker distributions and concentrations have been determined in 18 samples from a section of rhaetian age from the bristol trough and a quantitative micropalaeontological analysis carried out taking into account previous geological investigations of the sequence three end member depositional settings have been recognised from changes in total organic carbon content the biological markers and the micropalaeontological composition these depositional environments are attributed as follows the first which occurs in the lower part of the section corresponds to deposition in a supratidal sabkha type setting with the major organic input being of allochthonous origin the second also in the lower part of the section indicates the occurrence of periods of marine incursion with enhanced salinity resulting from evaporation in the upper part of the section marginal marine conditions are apparent with higher organic carbon biological marker and amorphous organic matter contents at the top suggesting the establishment of more stable conditions of oxygen depletion some sediments in the sequence are notable for containing an abundance of cysts of rhaetogonyaulax rhaetica one of the oldest marine dinoflagellates comparison of microfossil abundances with hydrocarbon abundances extends the circumstantial evidence for the dinophyceae being the major biological source of dinosteranes 4 23 24 trimethylcholestanes and some other 4 methyl steranes in marine sediments the presence of dinosteranes and their 24 ethyl counterparts extends the stratigraphic range of occurrence of such components back to the rhaetian c 31 methyl steranes in the sediments from the second depositional setting are tentatively assigned a 4 22 23 24 tetramethyl sterane skeleton and a dinoflagellate origin

application of 1d paleo fluvial process modelling at a basin scale to augment sparse borehole data example of a permian formation in the galilee basin australia