estimation of kerogen porosity in source rocks as a function of thermal transformation example from the mowry shale in the powder river basin of wyoming evaluations of porosity relevant to hydrocarbon storage capacity in kerogen rich mudrocks i e source rocks have thus far been plagued with ambiguity in large part because conventional core and petrophysical techniques were not designed for this rock type the growing recognition of an intraparticle organic nanopore system that is related to thermal maturity is beginning to clarify this ambiguity this mode of porosity likely evolved with the thermal transformation of labile kerogen and probably neither depends nor interacts except perhaps chemically with previously assumed matrix or mineral porosity that is dominated by bound water and that may be largely irrelevant to hydrocarbon storage capacity in these rocks to address this newly recognized and important nonmatrix kerogen pore system that is arguably the dominant hydrocarbon storage and mobility network in these rocks we introduce a relatively simple kinetic model that describes porosity development within kerogen as a function of thermal maturation kerogen porosity development is estimated within the upper albian mowry shale in the powder river basin of wyoming to illustrate the approach relevant storage capacity is considered to have evolved with thermal decomposition of organic matter during catagenesis where we estimate that kerogen porosity does not typically exceed 3 of bulk rock volume modeled oil in place estimates are comparable to residual oil estimates from pyrolysis data s1 at lower maturities but exceed pyrolytic s1 yields at higher maturities we hypothesize therefore that a subsurface kinetic porosity model might represent a means to account for s1 losses at surface conditions and to circumvent difficulties surrounding estimations of expulsion efficiencies that are inherent to more traditional mass balance calculations

revised models for determining toc in shale play example from devonian duvernay shale western canada sedimentary basin abstract determination of total organic carbon toc is essential in unconventional shale resource play evaluation indirect method such as petrophysical approach can provide a fast convenient and cost efffective means for toc estimation from well logs among the publically available approaches the logr method is a popular one in conventional source rock evaluation and has been applied to unconventional resource play evaluation by many practitioners careful examination of the method finds that improvements can be made for a better toc estimation with relaxed limitations this study proposes the following revisions on the original logr method 1 allowing estimation of petrophysical parameters from the targeted source rock rather an assumed linear approximation 2 using additional logs to improve toc prediction and 3 replacing lom level of organic metamorphism unit with a more commonly used thermal indicator tmax for convenience depending on data or preference the choice of using different porosity logs density versus sonic and parameter estimation methods cross plot method versus data driven approaches makes the revised method flexible for application we present the revisions along with application examples from the devonian duvernay shale in the western canada sedimentary basin to demonstrate the application of the improved logr method in shale gas evaluation comparison of the results from the revised method and the original one reveals that the revised models provide better and unbiased estimates of toc with a higher correlation coefficient and bell shaped residues centered at zero

influential factors and model of shale pore evolution a case study of a continental shale from the ordos basin abstract pore characteristics have a significant influence on the occurrence and enrichment of shale gas therefore these characteristics are key parameters in shale reservoir evaluation and have important research significance taking a continental shale sample from the ordos basin china as an example this research used low pressure co2 n2 adsorption high pressure mercury intrusion porosimetry mip vitrinite reflectance ro analysis hydrocarbon generation measurements x ray diffraction analysis and argon ion polishing field emission scanning electron microscopy aip fesem in conjunction with a thermal simulation experiment to study pore characteristics through the above analyses this study achieved a whole aperture dynamic characterization of the shale pores and discussed the characteristics of the shale pore distribution and evolution through geological history then the factors influencing pore evolution were analysed and a pore evolution model was established the results showed that the micropores and mesopores provided the majority of the surface area in the sample while the mesopores and macropores provided the majority of the pore volume in the sample during the thermal simulation experiment pore evolution was dominated by the hydrocarbon generation by organic matter the transformation of minerals and compaction according to the pore evolution characteristics and the main influential factors during the thermal simulation experiment the pore evolution model can be divided into four stages the characteristics of the micropores mesopores macropores and the influential factors differ in each stage

porosity and pore size distribution in mudrocks from the belle fourche and second white specks formations in alberta canada the distribution of porosity was examined on seven drill cores from west central alberta encompassing the belle fourche and second white specks formations these cenomanian turonian mudrocks from the western canada sedimentary basin exhibit good organic richness 2 wt total organic carbon and marine kerogen type ii with limited kerogen type iii with the increasing thermal maturity from approximately 0 43 vitrinite reflectance ro to approximately 0 90 ro the total porosity decreases from approximately 9 to approximately 1 vol this change translates to a reduction in total pore volume from approximately 0 05 to approximately 0 005 cm3 g and is accompanied by changes in relative proportions of micropore mesopore and macropore volumes variations in total porosity for the seven cores with different thermal maturities across alberta are mainly related to mesoporosity and macroporosity although the in core variations in total porosity are mainly related to microporosity in general organic matter micropores contribute to the overall microporosity in the seven cores across the study area the increase in the total pore volumes is in accordance with an increasing concentration of quartz although increasing concentrations of chlorite and kaolinite may contribute to greater abundance of micropores in the seven cores the in core variations suggest that greater contents of kaolinite and illite may contribute to increasing mesopore volumes variations in pore volumes and pore size distribution with depth within individual cores representing specific thermal maturity level differ from what is observed laterally when cores of various thermal maturity levels across alberta are compared indicating complex controls on porosity systems

organic matter mineral composition pore size and gas sorption capacity of lacustrine mudstones implications for the shale oil and gas exploration in the dongying depression eastern china because clay minerals and pore size distribution are important for oil and gas accumulation in lacustrine mudstone reservoirs this study aimed to characterize the pore size distribution in lacustrine mudstone reveal the importance of clay minerals in gas sorption capacity gsc provide insights into the primary gsc controls for lacustrine mudstones and discuss the shale oil and gas resource potential and possible risks in their future production a total of 256 core samples from the lower paleogene sequence of the dongying depression in the bohai bay basin in china were analyzed to determine organic richness and hydrocarbon generation potential a series of analyses was conducted on a suite of 28 mudstone samples from the s121 well to investigate the mineral composition pore size distribution and primary controls on gsc scanning electron microscopy and x ray diffraction were used to observe the microscopic characteristics and identify various minerals nitrogen adsorption experiments at low temperatures and a methane isothermal adsorption test were conducted to study the pore sizes and gas adsorption capacities experimental results show that the majority of the samples were rich in type ii and i kerogen with moderate to high hydrocarbon generation potential and are thermally mature in the main oil window the contents of illite and mixed layer illite smectite i s are high 40 in these lacustrine mudstones the pores were mainly thin long and bottleneck shaped and dominated by type iv and h2 hysteresis loop characteristics the abundance of quartz feldspar illite and mixed layer i s all presented a positive correlation with their brunauer emmett teller surface area and total pore volume whereas the abundance of carbonate minerals dominated by calcite showed a negative correlation the volume of micropores and clay minerals were the main factors controlling gscs the results highlight the importance of clay minerals including the illite and mixed layer i s in the lacustrine mudstones because of their considerable gsc high content of illite and mixed layer i s in lacustrine mudstone is in favor of gas storage whereas at the same time it is not conducive to shale gas development because of its reducing the brittleness of shale the paleogene of dongying depression has shale oil and gas resources however several key geological factors including pore size distributions pore diameters oil density and low brittleness may pose risks in shale oil and gas development

some pragmatic perspectives in source rock geochemistry abstract conceptual advances in petroleum source rock geochemistry made during the last decade are reviewed and some problem areas in analytical geochemistry are outlined areas of discussion include views of source rocks based on assessment of hydrocarbon expulsion kinetic models of kerogen maturation vitrinite reflectance evolution and a discussion of the data dilemma facing modern source rock geochemistry the increased application of petroleum geochemistry to the quantitative solution of geological problems is stressed

variation in organic matter quality and maturity in draupne formation source rocks from the oseberg field region offshore norway abstract detailed characterization of the kerogens from closely spaced samples from the draupne formation penetrated by two wells a and b in the oseberg field region has been carried out by geochemical and petrographic methods for selected samples the c15 hydrocarbon fraction has been examined by gc and gc ms petrographic analyses by transmitted light and uv excitation fluorescence methods demonstrate that the organic matter in all samples from both wells consists predominantly of amorphous material total organic carbon contents and hydrogen indices indicate an overall trend of decreasing kerogen quality with increasing depth for the draupne formation in well a similar data for samples from well b demonstrated generally inferior kerogen quality maturation level for the organic matter of the draupne formation in well a is slightly higher than that in well b while both draupne sections are within the limits for an immature source rock with a type ii kerogen gc and gc ms analysis showed that the samples from well b were enriched in lighter hydrocarbons as compared to samples from well a it is suggested that this may be due to minor staining of the former samples by migrated light hydrocarbons from the underlying upper jurassic sandstone reservoir a correlation between the two sections of draupne formation based on organic facies characteristics indicate a general correspondance between the lowermost part of the section in well a and the section in well b

rock physics modeling for the elastic properties of organic shale at different maturity stages abstractmodeling the elastic properties of organic shale has been of long standing interest for source rocks and unconventional reservoir characterization organic shales exhibit significant variabilities in rock texture and reservoir properties at different maturity stages subsequently affecting their elastic responses we have developed a new rock physics modeling scheme honoring the maturity levels immature mature and overmature which are constrained by the evolution of the physical properties of organic shale upon kerogen maturation in particular at different maturity stages the manners in which the compliant organic materials interact with the inorganic mineral matrix are characterized by different effective medium theories on the basis of the developed rock physics templates organic shales have different elastic behaviors at different maturity stages ignoring the impact of kerogen maturation is insufficient to adequately characterize the elasticity of the whole organic shale system mode

discussion on the method for determining bet specific surface area in argillaceous source rocks samples of argillaceous source rocks were taken at different depth in dongying sag and pretreated with different methods contrastive analysis to those samples by using n2 adsorption pyrolysis x ray diffraction detection has been made so as to discuss the validity and credibility of the detection method for specific surface area ssa and work for the study on shale gas preservation characteristics the source rocks were treated with hydrogen peroxide and chloroform it is found that the average toc content in the source rock samples treated with hydrogen peroxide decreased than that of the original sample by 61 3 on average for the removal of organic matter in particle state and surface adsorption state whereas decreased by 20 9 in the samples treated with chloroform for the dissolved organic matter organic matter in intergranular pores and physical adsorbed removal accordingly the average bet specific surface area increased by 77 5 in the samples treated with hydrogen peroxide than that of the original sample whereas increased by 22 0 in the samples treated with chloroform which shows that the organic matter on the specific surface of source rocks can be effectively removed and bet specific surface area extended both with chloroform and hydrogen peroxide treatment nonetheless further analysis shows that the samples treated with chloroform contain the same mineral compositions as the original samples while the samples treated with hydrogen peroxide have considerably different mineral compositions from the original samples thus breaking up the original rock structure and the mineral content of the source rocks based on the study and analysis above it is the best choice to select the chloroform treatment to the bulk rock samples for detecting the bet specific surface area which is possible not only to effectively remove organic matter but also keep the original mineral structure of the rock thus obtaining true in situ external specific surface area of source rocks and providing reliable parameters for the study of shale gas occurrence state

a data driven model for studying kerogen kinetics with application examples from canadian sedimentary basins abstract source rock is an essential element in unconventional resource play evaluation while kerogen kinetics is one of the most important components in source rock evaluation traditional approach for determining oil generation kinetics is done through laboratory pyrolysis analysis by mimicking the hydrocarbon generation processes with variable accelerated heating rates thus the thermal energy required for hydrocarbon generation under geological conditions is inferred study suggests that for a given kerogen type numerical kinetic models derived from a limited number of laboratory tests may result in unacceptable errors because of under representation of variation in activation energy related to organic facies change and source rock heterogeneity as economic margin of developing an unconventional resource play can be small business success often depends on early identification of favourable area a quick and robust method for resource play evaluation is critical this study proposes a data driven statistical approach that utilizes existing rock eval toc data by fitting the measured hydrogen index and tmax to an exponential model the model is designed so that all parameters have an explicit physical meaning and the ranges of parameter values are predictable once the empirical statistical model is established hydrocarbon transformation ratio can be calculated to represent the hydrocarbon generation kinetics of the source rock the main advantage of the proposed approach is the utilization of widely available rock eval datasets so that 1 no additional specifically designed laboratory pyrolysis experiments are required 2 the uncertainty due to facies variation or source rock heterogeneity nature and poor data quality human can be quantified through the statistical analysis of a large dataset and 3 validation for temperature and geothermal rates in situ pressure and other environmental conditions is not necessary as the input data for the model are all based on naturally matured samples rock eval datasets from four well known canadian source rock intervals representing the most common kerogen types are tested and used as examples to demonstrate the application of the proposed method the examined source rocks with different kerogen types show distinct kinetic behaviours and this is consistent with models derived from laboratory tests applications also indicate that the proposed method appears to be robust and convenient for modelling kerogen kinetics from rock eval data directly

late gas generation potential for different types of shale source rocks implications from pyrolysis experiments abstract gas generation from shale source rocks typically occurs via cracking of both kerogen and retained oils such that it is difficult to predict and compare gas generation potentials of different shales because they are related not only to the kerogen type but also to the oil expulsion efficiency in this study five different shale kerogen samples were pyrolyzed in sealed gold tubes to investigate how kerogen type and oil expulsion efficiency affect their gas generation after oil window maturity the results illustrate that the maximum extractable organic matter eom and gas generation potentials of different original shale kerogens o kerogen in a closed system vary widely in the range of 229 790 mg g tocok and 308 594 ml g tocok respectively however the gas yields of different residual shale kerogens r kerogen with a starting equivalent vitrinite reflectance eqvro value of approximately 1 22 are quite similar and vary between 131 and 145 ml g tocrk pyrolysis experiments also reveal that the late gas generation potential eqvro 1 22 of shale is mainly controlled by the amount of retained eoms rather than kerogen type when the shale source rocks containing types i and ii kerogens have the same amount of retained eoms their gas generation potentials are quite similar under most geological conditions the late gas generation potentials of shale source rocks normalized to the toc of matured shale at 1 22 eqvro tocshale vary approximately in the range of 180 300 ml g tocshale to reach a gas content of 3 m3 ton shale for the present day overmature shale gas exploration in the lower palaeozoic shales of south china a conservative present day toc tocpd value of 2 0 is proposed as a screening parameter that can eliminate the risk of insufficient gas generation potential as much as possible

a revised method for reconstructing the hydrocarbon generation and expulsion history and evaluating the hydrocarbon resource potential example from the first member of the qingshankou formation in the northern songliao basin northeast china abstract reconstructing the hydrocarbon generation and expulsion history of source rocks is an essential part of evaluating the hydrocarbon resource potential by genetic method the hydrocarbon generation potential method is an efficient tool for quantifying the hydrocarbon generation and expulsion characteristics of source rock and evaluating the hydrocarbon resource potential based on rock eval data although various revised versions of the method are publicly available the following problems remain to be resolved a the method is subjective b implicit limitations are observed and c rock mass loss is not considered which may result in unacceptable errors in this study we propose a revised hydrocarbon generation potential method expressions for calculating the original rock mass go original total organic carbon toco transformation ratio tr hydrocarbon expulsion ratio er and hydrocarbon expulsion efficiency f were developed and incorporated into the hydrocarbon generation and expulsion history reconstruction and hydrocarbon resource potential evaluation and these expressions combined conventional and unconventional resource evaluations systematically with objective and accurate results the first member of the qingshankou formation k2qn1 in the northern songliao basin northeast china was used as an example to demonstrate the application of the proposed method the results have been compared with the unrevised method using the same rock eval data sets and verified with previous reports to demonstrate its reliability the results also indicate that the hydrocarbon generation threshold hgt and hydrocarbon expulsion threshold het of k2qn1 are ro 0 4 and ro 0 6 respectively three hydrocarbon generation and expulsion peak stages were identified k2n 81 74 ma k2m 74 66 ma and n2t 66 0 ma the hydrocarbon generation and expulsion centers of k2qn1 are mainly the qijia gulong sag and sanzhao sag the resource potentials of conventional oil unconventional tight oil and shale oil associated with k2qn1 source rocks in the northern songliao basin are 8 15 108 t 22 97 108 t and 62 1 108 t respectively

geochemical truths in large data sets i geochemical screening data abstract organic geochemistry especially when undertaken on a well by well or outcrop by outcrop basis arguably lacks statistically significant numbers of analyses to establish reliable trends can a reliable vitrinite reflectance vs depth trend be established from say 12 analysed samples when the number of analysed samples are in the hundreds or even thousands much clearer general trends are established and anomalous measurements more readily recognised interpretation of anomalies is itself highly instructive but forms another paper in this paper a global data set of some 5000 source rock samples is assembled from the open literature and released data e g open file reports and the results discussed to produce practical oil industry interpretations from basic screening data a complex conclusion can be extracted from simple data sets and are supported by mass balance and kinetic theory it is concluded that interpretation always falls back on a comparison of new data with pre existing knowledge in the form of tables and plots total organic carbon toc values are generally log normally distributed so that using mean standard deviation values will under estimate the upside potential when fed into risked probabilistic hydrocarbon charge prediction models kerogen type is initially best determined using plots of rock eval s 2 vs toc rather than the hydrogen index hi s 2 toc vs oxygen index oi s 3 toc or pseudo van krevelen plot the intercept of the s 2 vs toc plot predicts the average dead carbon inertinite content of the source rock set with the slope corresponding to the hydrogen index of the labile component hi l maturity trends of the hydrogen index vs t max or r o show reversals at high maturities as supported by the kinetics of the thermal breakdown of the three standard kerogen types at elevated maturities type iii kerogens have higher hydrogen indices than types i and ii kerogens a feature that must be taken into account when correcting mature kerogens to their original hi values hi o the reduction in hydrogen index is a measure of generation with the corresponding increase in production index pi s 1 s 1 s 2 being effectively a measure of hydrocarbon retention a cross plot of hi vs pi can be interpreted in terms of expulsion efficiencies expelled generated minus retained hydrocarbon measured data support a pore saturation and or generation pressure driven process for expulsion and indicate a limiting pore saturation equivalent to a production index of 0 6 for rich 2 toc source rocks

heterogeneity of free and occluded bitumen in a natural maturity sequence from oligocene lake enspel abstract sedimentation in oligocene lake enspel was rapidly terminated by a basaltic lava flow this introduced a preservational barrier while imparting a natural flash pyrolysis during which the organic matter in underlying stratigraphic units was subjected to rapid thermal maturation resulting in hydrocarbon generation samples from these strata exhibit a steep maturity gradient 0 25 1 07 optical vitrinite reflectance or ro over uniform organofacies this offers the opportunity to investigate bitumen generation during rapid thermal maturation mechanistically in particular the nature of bitumen 2 occluded bitumen which is only recoverable after the digestion of the mineral matrix and was frequently dismissed as an artifact of incomplete extraction elaborate sequential extraction of the contact metamorphic sequence of oil shales at enspel revealed systematic changes in bitumen composition these trend progressively towards those of occluded bitumen which exhibits a systematically elevated thermal maturity a higher degree of catalytic biomarker rearrangement and the conspicuous absence of molecular signatures from vascular plants that are present in the free bitumen one plausible explanation involves a contribution of allochthonous clay adsorbed organic matter to bitumen 2 this could represent a mixture of older reworked bitumen and an early diagenetic snapshot of clay adsorbed organic matter alternatively a close association of early generated bitumen with clay minerals may have led to enhanced isomerization and catalytically influenced uniformization of alkane signatures deviations from the expected relationships between various thermal maturity parameters suggest variable dependence on the time pressure temperature pathway i e metamorphic facies the maturation of organic matter likely behaves differently under a contact metamorphic regime or during rapid subsidence and exhumation as compared to slow maturation during regional subsidence our data also suggest that geologically brief shallow intrusive or extrusive magmatism might not be as destructive to the sedimentary hydrocarbon inventory as hitherto thought this study draws attention to the small scale compositional heterogeneity of bitumen that can be studied using sequential extraction methods more importantly it suggests that occluded bitumen could potentially harbor information on organic matter that pre dates in situ primary productivity and may be derived from allochthonous biomass and detrital input

shale oil resource potential and oil mobility characteristics of the eocene oligocene shahejie formation jiyang super depression bohai bay basin of china abstract oil mobility in liquid rich shale is crucial for economic success of resource development the characteristics of the host rock and the properties of oil fluids are two primary factors controlling fluid mobility organic geochemistry data allows examination of both resource potential and oil mobility we propose data driven empirical models in this paper to describe hydrocarbon resource potential with respect to oil mobility the proposed methods were applied to a dataset collected from the eocene oligocene es3 and es4 source rock units in four recent shale oil exploration wells in the jiyang super depression of the bohai bay basin the dataset results from standard programmed pyrolysis of whole rock samples as well as solvent extracted replicates of 139 core samples was studied to examine the source rock characteristics and shale oil resource potential bulk geochemical characteristics and thermal decomposition trends allow for sub division of the samples into two groups a samples with high initial hydrogen index 800 mg hc g toc and average present day toc of 4 07 from ly1 and ny1 wells in a distal facies and b samples with slightly lower initial hydrogen index about 700 mg hc g toc and average toc of 3 11 from fy1 and l69 wells in a transitional facies three different categories of oil resource with respect to oil mobility can be defined adsorbed restricted and movable based on organic geochemical characteristics and their variations in the stratigraphic intervals represented by the samples in the four wells we show that expulsion efficiency is a good indicator of hydrocarbon retention in source rock reservoir and that the two wells in the distal facies have higher total resource potentials with abundant movable oil resource than the two wells in the transitional facies the total oil potential is separated into three types of oil resource to show oil mobility thus providing more information for business decision

flexural subsidence and basement tectonics of the cretaceous western interior basin united states the flexural subsidence history recorded in cenomanian to early campanian 97 to 80 ma strata in the cretaceous u s western interior basin was studied with two dimensional flexural backstripping techniques results indicate that the flexural subsidence resulting from thrust loading was superimposed on epeirogenic subsidence in the foreland basin the flexural component exhibits significant spatial and temporal variations along both the strike and dip relative to the sevier thrust belt the greatest cumulative subsidence occurred in southwestern wyoming and northern utah concurrent subsidence in northwestern montana and southern utah was insignificant temporal trends in subsidence also show a distinct regional pattern from the cenomanian to late turonian 97 to 90 ma subsidence rates were high in utah and much lower in wyoming and montana in contrast during the coniacian and santonian 90 to 85 ma subsidence accelerated rapidly in wyoming increased slightly in montana and decreased in utah we suggest that these spatially and temporally varying subsidence patterns reflect the interplay of several geodynamic factors including 1 temporal and spatial variation in emplacement of the thrust loads 2 segmentation of the basement into adjacent blocks with different rheological properties 3 reactivation of basement fault trends and 4 regional dynamic topographic effects

geological controls on matrix permeability of devonian gas shales in the horn river and liard basins northeastern british columbia canada abstract controls of matrix permeability are investigated for devonian gas shales from the horn river and liard basins in northeastern british columbia canada mineralogy is varied with high carbonate high quartz and moderate quartz carbonate and clay rich strata quartz content varies between 2 and 73 carbonate varies between 1 and 93 and clay varies between 3 and 33 the toc content ranges between 0 3 and 6 wt and porosity varies between about 1 and 7 for horn river basin samples quartz is mainly biogenic in origin derived from radiolarians toc content increases with the quartz content suggesting the toc and quartz both are derived from siliceous phytoplankton a positive relationship between porosity and quartz content is due to the positive relationship between quartz and toc matrix permeability parallel to bedding varies between 7 5e 02 and 7 1e 07 md at an effective stress of 15 mpa variation in permeability is due to a complex combination of factors that includes origin and distribution of minerals pore size distribution and fabric mercury intrusion capillary curves indicate that the higher matrix permeability values 2e 03 md occurs in samples that contain interconnected pore apertures greater than 16 m even when these samples may contain less macropores than low permeability samples the fabric of high permeability samples can be either isotropic or anisotropic however permeability of anisotropic samples is more sensitive to changes in effective stress than isotropic samples more highly anisotropic samples contain moderate amounts of quartz carbonate and in some clay high permeability samples that contain a more balanced ratio between micro meso and macroporosity would not only have faster flow rates but also greater access to sorbed gas within the microporosity compared to samples that lack mesopores several muskwa samples compared to evie and besa river samples contain higher quartz moderate clay and high toc content coupled with high permeability less sensitivity to effective stress and balanced ratios between micro meso and macroporosity would be a lower exploration risk due a greater propensity to fracture the ability to produce and store hydrocarbons due to higher toc contents and greater communication between macropores and micropores in the organic and clay fractions

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

investigation of methane sorption of overmature wufeng longmaxi shale in the jiaoshiba area eastern sichuan basin china abstract in china shale gas of production capacity 203 000 m3 per day has been identified in well jy1 in the upper ordovician wufeng formation shale o3w and the lower silurian longmaxi formation shale s1l jiaoshiba area sichuan basin however the adsorbed gas capacity and the relative ratio between free gas and adsorbed gas are unknown in the jiaoshiba area and this is important for further shale gas exploration and development and different adsorption models need to be calibrated very well to praise the sorption capacity the samples were obtained from the well jy1 sorption isotherm experiments were performed at a range of pressures up to 17 mpa and temperatures up to 90 c to determine the effects of toc moisture and clay minerals on methane adsorption capacity the methane maxima adsorbed capacity values have a clear positive relationship with toc clay content displays a weak correlation with methane adsorbed amounts normalized to toc indicating that clay minerals are a minor contributor to shale adsorption capacity moisture reduces methane sorption capacity by around 20 both the supercritical dubinin radushkevich sdr based and the langmuir based excess adsorption models are used to fit measured adsorption isotherms most of the methane adsorption phase density values fitted by both models are greater than the density of liquid phase methane at its boiling points 424 mg cm3 for the langmuir based model a fixed adsorption density of 424 or 373 mg cm3 was used in fitting the experimental data which will result in higher maximum adsorbed capacity values for the sdr based model maxima adsorbed capacity values remain stable and have nothing to do with sorption phase density

expelled oils and their impacts on rock eval data interpretation eocene qianjiang formation in jianghan basin china abstract source rock samples can be contaminated by expelled oils from nearby mature source rocks or from the organic rich laminae within the same source rock units the contaminations on the rock eval samples could produce a false high s1 peak a high production index pi a suppressed tmax and other anomalies identifying the samples affected by expelled oils assessing and correcting the impacts are crucial in source rock study for shale oil shale gas resource evaluation this study analyzes the rock eval 6 results of 43 core samples from two recent shale oil exploration wells of the eocene qianjiang formation a confined source rock unit embedded with salt intervals formed in a hypersaline lacustrine setting in central china the geochemical anomalies of the affected samples are shown through the available samples in this study criteria for identifying the affected samples are discussed and impacts on the conventional rock eval parameters and subsequent estimation of kinetic parameters presented this study provides insights into rock eval data interpretation particularly in source rock evaluation for estimating shale oil resources

experimental investigation of changes in methane adsorption of bitumen free woodford shale with thermal maturation induced by hydrous pyrolysis this study quantifies the effects of organic matter om thermal maturity on methane ch4 sorption on the basis of five samples that were artificially matured through hydrous pyrolysis achieved by heating samples of immature woodford shale under five different time temperature conditions ch4 sorption isotherms at 35 degrees c 50 degrees c and 65 degrees c and pressures up to 14 mpa on dry solvent extracted samples of the artificially matured woodford shale were measured the results showed that ch4 sorption capacity normalized to toc varied with thermal maturity following1 the trend maximum oil 367 degrees c oil cracking 400 degrees c maximum bitumen early oil 333 degrees c early bitumen 300 degrees c immature stage 130 degrees c the langmuir constants for the samples at maximum oil and oil cracking stages are larger than the values for the bitumen forming stages the total pore volume determined by n 2 physisorption at 77 k increases with increased maturation mesopores 2 50 nm in width were created during the thermal conversion of organic matter and a dramatic increase in porosity appeared when maximum bitumen and maximum oil generation stages were reached a linear relationship between thermal maturity and brunauer emmett teller bet surface area suggests that the observed increase in ch4 sorption capacity may be the result of mesopores produced during om conversion no obvious difference is observed in pore size distribution and pore volume for samples with pores 2 0 nm with the increase of thermal maturity based on co2 physisorption at 273 k the isosteric heat of adsorption and the standard entropy for artificially matured samples ranged from 17 9 kj mol 1 to 21 9 kj mol 1 and from 85 4 j mol 1 k 1 to 101 8 j mol 1 k 1 respectively these values are similar to the values of immature woodford kerogen concentrate previously observed but are larger than naturally matured organic rich shales high temperature hydrous pyrolysis might have induced lewis acid sites on both organic and mineral surfaces resulting to some extent in chemical interactions between the adsorption site and the methane c h bonds the formation of abundant mesopores 2 50 nm within organic matter during organic matter thermal maturation makes a great contribution to the increase in both bet surface area and pore volume and a significant increase in 2 6 nm pores occurs at maximum oil generation and oil cracking to gas ultimately controlling the methane adsorption capacity therefore consideration of pore size effects and thermal maturity is very important for gas in place gip prediction in organic rich shales c 2014 elsevier ltd all rights reserved

microstructural characterization of pores in marine shales of the lower silurian longmaxi formation southeastern sichuan basin china abstract understanding the complexities of sedimentary pore systems is the key to understanding the mechanisms that lead to shale gas accumulation in this study the microstructures networks and connectivity of pores in marine shales of the longmaxi formation in the southeastern sichuan basin are investigated using a combination of qualitative and quantitative methods 2d and 3d characterizations of the formation provide an opportunity to describe the types of pores pore networks and pore connectivity in these shales the study s results show that nearly all pores are nanosized and that organic matter om pores are the most common but also include interparticle interp pores intraparticle intrap pores and micro fracture pores reconstructed 3d models show that there is limited connectivity of pores gas adsorption analysis and statistical results indicate that nearly 95 of the pores are micro to meso scale and account for approximately 23 and 73 of the pore space respectively a combination of image processing and calculations also shows that om pores account for approximately 87 of all pores and as such the pore networks are dominated by om pores om pores are associated with discontinuous occurrences of organic matter which results in relatively poor connectivity

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

major and trace element geochemistry of the lacustrine organic rich shales from the upper triassic chang 7 member in the southwestern ordos basin china implications for paleoenvironment and organic matter accumulation abstract lacustrine organic rich shales are widespread in the upper triassic yanchang formation chang 7 member of the ordos basin however information on the short term climate evolution within the chang 7 member is still lacking and the mechanism of organic accumulation in the shales remains controversial to address these issues this study analyzes the palaeoenvironment and depositional setting of different intervals in the chang 7 member of the southwestern ordos basin and constrains the main control factors on accumulation and preservation of organic matter based on organic major and trace element data the lower chang 73 shale which contains a high abundance of thermally mature type i and ii kerogen has excellent original hydrocarbon generative potential the lower chang 73 interval has the most humid climatic condition the strongest weathering condition a euxinic bottom water condition a high paleo productivity and a low terrigenous input during the period of upper chang 73 and chang 72 the climate became somewhat drier and hotter which was marked by relatively weak weathering conditions suboxic to anoxic conditions low paleoproductivity and high terrigenous input the chang 71 was characterized by a moderately humid climate moderate weathering conditions paleoproductivity and terrigenous input the relationship among the primary productivity redox conditions clastic influx indicators and toc content suggests that primary productivity was the most critical factor controlling the enrichment of organic matter the high primary productivity during the early chang 73 interval was probably driven by the deposition of volcanic ash and was influenced by marine incursion events a warm and humid paleoclimate combined with input of volcanic ash and seawater resulted in eutrophic nutrient rich and stratified surface water during the early chang 73 period which led to algal blooms with high primary productivity a stratified water column with high primary productivity together with oxygen deficit bottom water conditions and low terrigenous input resulted in the greatest enrichment of organic matter in the lower part of chang 73 shale

testing reproducibility of vitrinite and solid bitumen reflectance measurements in north american unconventional source rock reservoir petroleum systems abstract an interlaboratory study ils was conducted to test reproducibility of vitrinite and solid bitumen reflectance measurements in six mudrock samples from united states unconventional source rock reservoir petroleum systems samples selected from the marcellus haynesville eagle ford barnett bakken and woodford are representative of resource plays currently under exploitation in north america all samples are from marine depositional environments are thermally mature tmax 445 c and have moderate to high organic matter content 2 9 11 6 wt toc their organic matter is dominated by solid bitumen which contains intraparticle nano porosity visual evaluation of organic nano porosity pore sizes 1 0 produced lowest r values generally 0 5 absolute reflectance similar to a prior ils for similar samples other traditional approaches to outlier removal outside mean 1 5 interquartile range and outside f10 to f90 percentile range also produced similar r values standard deviation values

depositional mechanisms and organic matter in mowry shale cretaceous wyoming four lithofacies which accumulated under different depositional conditions can be distinguished in the lower cretaceous mowry shale of wyoming type and amount of organic matter in these lithofacies are governed largely by sediment transport mechanisms nearshore silt and mud containing terrestrial organic matter were deposited in a prodelta environment by tractive processes and from suspension these sediments along with terrestrial organic matter were redistributed by waning bottom flows over a dysaerobic slope pelagically deposited muds containing marine derived organic matter accumulated between flow events muds farthest offshore accumulated in dysaerobic and anaerobic water by pelagic settling in a region unaffected by bottom currents these muds contain predom nantly marine derived organic matter petroleum source potential increases in a southeastward direction across west and central wyoming this trend results from differential input of marine and terrestrial organic matter clastic dilution and postdepositional biodegradation

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

effect of thermal maturity on elastic properties of kerogen abstractwe have performed spatially continuous nanodynamic mechanical analysis on four organic rich shale samples with different thermal maturities to extract the elastic modulus of the kerogen particles aliquots were rigorously prepared and three scans were acquired from each aliquot subcritical nitrogen adsorption pore characterization was performed to determine the abundance of kerogen hosted porosity to fully characterize the pore system of samples from the oil window toluene and then chloroform extraction were performed to remove the pore filling hydrocarbons prior to nitrogen adsorption the statistical distribution of the measured modulus values was analyzed to extract the properties of the shale particles in mature samples from the peak oil generation or gas window the kerogen porosity was the dominant pore morphology we found that significant lowering of the kerogen particle modulus resulted from intraparticle kerogen porosity the kerogen particle modulus in mature samples was measured a

a model for porosity evolution in shale reservoirs an example from the upper devonian duvernay formation western canada sedimentary basin the influence of thermal maturity on porosity in shale samples from the upper devonian duvernay formation is examined the samples span a maturity range from immature to the wet gas window porosity decreases from immature to the oil window primarily because of compaction relatively high porosity of wet gas window samples is ascribed to formation of secondary organic pores feldspar dissolution pores and primary pore preservation by the quartz framework the final decline in the porosity of the dry gas window samples is explained by greater compaction the disappearance of secondary organic pores and feldspar dissolution pores porosity correlates positively to quartz content and negatively to carbonate content no relationship was evident between porosity and clay or total organic carbon content no obvious correlations exist between rock composition and permeability except that sio2 content shows a weakly positive correlation to permeability permeability is highest in immature samples which have the greatest pore and pore throat sizes nitrogen adsorption and mercury injection analysis show that pore and pore throat sizes decrease with increasing maturity visible pores imaged by scanning electron microscopy and helium ion microscopy exist as organic pores including bubblelike pores developed within organic matter om and fissure type pores intraparticle pores mainly developed within carbonate grains and interparticle pores either within a clay rich matrix or between rigid mineral grains in immature samples the primary pores are interparticle pores between clay minerals and other mineral grains the om fissures are ubiquitous in oil window samples and secondary bubblelike om hosted pores are well developed within gas window samples

organic matter hosted pore system in the wufeng longmaxi o3w s11 shale jiaoshiba area eastern sichuan basin china abstract the first commercial shale gas with the capability to produce 203 000 cubic meters per day were discovered in the wufeng longmaxi o 3 w s 1 l shale namely the upper ordovician wufeng shale o 3 w and the lower silurian longmaxi shale s 1 l of well jy1 jiaoshiba area eastern sichuan basin china in this study fe sem co 2 and n 2 sorption and micp were used to characterize the pore morphology type size and specific surface area of the wufeng longmaxi shale we focused our research on well jy1 to establish a standard well cross section to allow comparison with well studied gas shales such as barnett marcellus kimmeridge clay and others fe sem visible mineral pore sizes range from 4 nm to 3416 nm with an average of 118 nm within the wufeng longmaxi shale om hosted pore sizes vary from 5 nm to 1021 nm with an average of 68 nm within the wufeng longmaxi shale micropore volumes vary from 0 0048 cm 3 g to 0 0078 cm 3 g with an average of 0 0059 cm 3 g mesopore volumes range from 0 0108 cm 3 g to 0 0166 cm 3 g with an average of 0 0139 cm 3 g macropore volumes range from 0 00005 cm 3 g to 0 00274 cm 3 g with an average of 0 00108 cm 3 g and surface areas range from 22 05 m 2 g to 36 37 m 2 g with an average of 27 68 m 2 g the average pore diameters of wufeng longmaxi shales range from 5 31 nm to 7 40 nm toc has a significant effect on bulk shale porosity porosity measured by fe sem ranges from 0 46 to 1 54 but covers only a small fraction of the shale total porosity as the fe sem detection limit is in a m range the majority of shale pore space pores 2 and n 2 adsorption and have an obvious relationship with the toc therefore the wufeng longmaxi shale has a predominantly organic matter pore system

a depositional model for offshore deposits of the lower blue gate member mancos shale uinta basin utah usa depositional models that use heterogeneity in mud dominated successions to distinguish and diagnose environments within the offshore realm are still in their infancy despite significant recent advances in understanding the complex and dynamic processes of mud deposition six cored intervals of the main body of the mancos shale the lower blue gate member uinta basin were examined sedimentologically stratigraphically and geochemically in order to evaluate facies heterogeneity and depositional mechanisms unique sedimentological and geochemical features are used to identify three offshore environments of deposition the prodelta the mudbelt and the sediment starved shelf prodelta deposits consist of interlaminated siltstone and sandstone and exhibit variable and stressed trace fossil assemblages and indicators of high sedimentation rates the prodelta was dominated by river fed hyperpycnal flow mudbelt deposits consist of interlaminated siltstone and sandstone and are characterized by higher bioturbation indices and more diverse trace fossil assemblages ripples scours truncations and normally graded laminations are abundant in prodelta and mudbelt deposits indicating dynamic current conditions mudbelt sediment dispersal was achieved by both combined flow above storm wave base and current enhanced and wave enhanced sediment gravity flows below storm wave base sediment starved shelf deposits are dominantly siltstone to claystone with the highest calcite and organic content bioturbation is limited to absent sediment starved shelf deposits were the result of a combination of shelfal currents and hypopycnal settling of sediment despite representing the smallest volume sediment starved shelf deposits are the most prospective for shale hydrocarbon resource development due to elevated organic and carbonate content sediment starved shelf deposits are found in either retrogradational to aggradational parasequence sets or early distal aggradational to progradational parasequence sets bounding the maximum flooding surface an improved framework classification of offshore mudstone depositional processes based on diagnostic sedimentary criteria advances our predictive ability in complex and dynamic mud dominated environments and informs resource prospectivity

a new thermal extraction protocol to evaluate liquid rich unconventional oil in place and in situ fluid chemistry abstract assessing oil in place and the proportion of oil that is producible are two critical measurements in evaluating liquid rich unconventional well and play economics current methodologies to evaluate oil in place oip include log calculated estimates petroleum systems charge modeling and direct geochemical measurements the standard open system programmed pyrolysis method has been modified to remove a broader range of thermally extracted free and adsorbed hydrocarbons and non hydrocarbons in liquid rich unconventional plays the added isotherms with a relatively low temperature start results in additional free hydrocarbon s1 peaks the extra s1 peaks are used to assist in evaluating in situ hydrocarbon quality examination of as received and post solvent extracted programmed pyrolysis data from replicate samples indicates a significant amount of solvent extractable free hydrocarbon is not captured in the s1 and rolls over into the s2 peak this observation suggests the s1 peak may not represent total oil in place less evaporative losses this paper examines a new multi step high resolution on column thermal extraction system to provide an inexpensive screening tool to map zones of higher in place oil and evaluate chemical characteristics which can be used to assist in estimating productivity the thermal extraction unit is coupled to a flame ionization detector fid by a short uncoated capillary column to generate a high resolution thermal extraction profile thermogram with four temperature fractions the area under each thermal peak provides direct measurements of volatized hydrocarbon and non hydrocarbon compounds examination of individual compounds within each thermal fraction demonstrates multi step thermal extraction is not a simple fractional distillation but also is impacted by inorganic and organic interactions if we assume each thermal fraction represents oil compounds with increased complexity then one can use peak area ratios to estimate in situ fluid make up and the proportion of in situ oil that can be considered producible with completions enhancement

the nature of porosity in organic rich mudstones of the upper jurassic kimmeridge clay formation north sea offshore united kingdom abstract analyses of organic rich mudstones from wells that penetrated the upper jurassic kimmeridge clay formation offshore united kingdom were performed to evaluate the nature of both organic and inorganic rock constituents and their relation to porosity in this world class source rock the formation is at varying levels of thermal maturity ranging from immature in the shallowest core samples to mature in the deepest core samples the intent of this study was to evaluate porosity as a function of both organic macerals and thermal maturity at least four distinct types of organic macerals were observed in petrographic and sem analyses and they all were present across the study area the macerals include in decreasing abundance 1 bituminite admixed with clays 2 elongate lamellar masses alginite or bituminite with small quartz feldspar and clay entrained within it 3 terrestrial vitrinite fusinite semifusinite grains and 4 tasmanites microfossils although pores in all maceral types were observed on ion milled surfaces of all samples the pores largely nanopores with some micropores vary as a function of maceral type importantly pores in the macerals do not vary systematically as a function of thermal maturity insofar as organic pores are of similar size and shape in both the immature and mature kimmeridge rocks if any organic pores developed during the generation of hydrocarbons they were apparently not preserved possibly because of the highly ductile nature of much of the rock constituents of kimmeridge mudstones clays and organic material inorganic pores largely micropores with some nanopores have been observed in all kimmeridge mudstones these pores particularly interparticle i e between clay platelets and intraparticle i e in framboidal pyrite in partially dissolved detrital k feldspar and in both detrital and authigenic dolomite are noteworthy because they compose much of the observable porosity in the shales in both immature and mature samples the absence of a systematic increase in organic porosity as a function of either maceral type or thermal maturity indicates that such porosity was probably unrelated to hydrocarbon generation instead much of the porosity within mudstones of the kimmeridge appears to be largely intraparticle and interparticle adjacent to inorganic constituents so the petroleum storage potential in these organic rich mudstones largely resides in inorganic pores

empirical relationship between gas composition and thermal maturity in eagle ford shale south texas organic rich and carbonate rich eagle ford shale is a self sourced oil and gas reservoir with little alteration of gas chemistry as might be affected by petroleum expulsion and migration as such it provides an ideal natural laboratory to quantify the compositional variation of gases generated from oil prone type ii kerogen during thermal maturation the chemical composition of the gas released from rock crushing was conducted and integrated with rock eval pyrolysis to define the empirical relationship between gas compositional parameters and thermal maturity in this study from 10 wells in the eagle ford shale in south texas we collected 74 core samples having a range of thermal maturity the measured maximum temperature tmax values of hydrocarbons generated in rock eval pyrolysis range from 427 c to 494 c 800 f to 921 f and the calculated equivalent vitrinite reflectance roe values range from 0 51 to 1 73 based on tmax values total organic carbon content ranges from 0 3 to 8 53 with an average of 3 12 standard deviation of 1 77 burial depth is from 2989 6 to 13 827 3 ft 911 2 to 4214 6 m our results showed that gas composition in the eagle ford shale is mainly controlled by thermal maturity and three stages of gas generation are identified based on the c1 and c2 concentrations of the gases released by rock crushing from eagle ford shale core samples the three stages of gas generation correspond to the following processes of organic matter conversion 1 kerogen and bitumen thermal cracking to crude oil 2 bitumen and heavy crude oil thermal cracking to light oil and 3 light oil cracking to gas methane rich gas and an abundance of branched butane and pentane are generated in light oil cracking to gas resulting in high c1 c2 c1 c2 c3 i c4 n c4 and i c5 n c5 ratios increased cracking of normal alkanes such as n butane and n pentane occurs in the light oil cracking to gas empirical equations between gas compositional parameters and thermal maturity tmax or roe are obtained for oil prone type ii the c1 c2 c1 c2 c1 c2 c3 and i c4 n c4 ratios are the five best parameters for determining thermal maturity with an exponentially derived r2 value of 0 74 the composition of gas produced from the eagle ford shale following hydraulic fracturing is used to validate the empirical equations calculated thermal regime for the oil production based on the produced gas is located at the peak of oil generation and the beginning of light oil cracking to gas corresponding to tmax from 454 c to 464 c 849 f to 867 f or at an roe ranging from 1 01 to 1 19 empirical equations provide a basis for interpretation of mud gas logging data and produced gas composition

a new method for assessing tight oil with application to the lucaogou formation in the jimusaer depression junggar basin china this study proposes a new method for estimating tight oil resources in a closed petroleum system using an alternative mass balance model the proposed approach primarily derives resource estimates based on a large volume of rock eval pyrolysis data in addition to leveraging the cost effective straightforward and rapid process the proposed method has the flexibility to assess the potential of different types of resources including organic rich tight shale oil and organic lean tight oil the method is validated by assessing the oil resource potential of the middle permian lucaogou formation p2l in the jimusaer depression junggar basin china results indicate that the p2l contains 1 62 109 t 11 91 109 bbl of organic rich and 2 88 109 t 21 17 109 bbl of organic lean tight oil of the organic rich tight oil 21 comprises free oil resources amounting to 0 343 109 t 2 521 109 bbl the proposed approach deals sufficiently with the different resources in a petroleum system well and provides a useful tool for estimating the resource potential of an unconventional play

paleozoic accretionary orogenesis in the eastern beishan orogen constraints from zircon u pb and 40ar 39ar geochronology abstract the continental growth mechanism of the altaids in central asia is still in controversy between models of continuous subduction accretion versus punctuated accretion by closure of multiple oceanic basins the beishan orogenic belt located in the southern altaids is a natural laboratory to address this controversy key questions that are heavily debated are the closure time and subduction polarity of former oceans the emplacement time of ophiolites and the styles of accretion and collision this paper reports new structural data u pb and ar ar ages from the eastern beishan orogen that provide information on the accretion process and tectonic affiliation of various terranes our geochronological and structural results show that the younging direction of accretion was northwards and the subduction zone dipped southwards under the northern margin of the shuangyingshan micro continent this long lived and continuous accretion process formed the hanshan accretionary prism our field investigations show that the emplacement of the xiaohuangshan ophiolite was controlled by oceanic crust subduction beneath the forearc accretionary prism of the shuangyingshan mazongshan composite arc to the south moreover we address the age and terrane affiliation of lithologies in the eastern beishan orogen through detrital zircon geochronology of meta sedimentary rocks we provide new information on the ages subduction polarities and affiliation of constituent structural units as well as a new model of tectonic evolution of the eastern beishan orogen the accretionary processes and crustal growth of central asia were the result of multiple sequences of accretion and collision of manifold terranes

distinct evolution trends of nanometer scale pores displayed by the pyrolysis of organic matter rich lacustrine shales implications for the pore development mechanisms abstract organic matter om compositions greatly affect hydrocarbon generation and expulsion processes which are critical for the organic porosity development in shale lacustrine shale samples of low thermal maturity were pyrolyzed using two pyrolysis systems closed and semi closed systems pore development was measured by low pressure gas adsorption and field emission scanning electron microscopy fe sem and bulk porosity was modeled utilizing organic geochemical data the gas adsorption analysis indicated that shale samples of different om compositions differed in pore volume evolution with thermal maturity mainly related to the different amounts of hydrocarbon generated and expelled residual bitumen significantly reduced the pore volume of om rich oil generative shale samples and restricted the micro meso and macro pore volumes to different extents calculations and experiments both showed that om rich and oil generative shale experienced a greater increase in pore volume after the oil peak in addition it was observed that variations in the main pore types were associated both with shale compositions and with exerted overburden pressure increase in overburden pressure were found to greatly facilitate the development of nanometer size spongy and complex om pores in shales containing type kerogens possibly as a result of the expulsion of gaseous hydrocarbons by contrast the shale with abundant type kerogen tended mainly to develop relatively large pores following oil expulsion regardless of overburden pressure the modeled organic porosity of pyrolyzed samples of type iii om was similar to the porosity of geological shale but the porosity of om rich oil generative shale samples with high expulsion efficiency at the oil generation stage was two to three times the measured porosity of the geological shale in some cases the higher modeled shale porosity might be related to the higher expulsion efficiency for geological shales of expulsion efficiency comparable to the pyrolyzed samples geological processes e g compaction and cementation may have greatly reduced the om associated pore volume

shelf sandstones in the mowry shale evidence for deposition during cretaceous sea level falls two previously undescribed sandstone beds in the lower cretaceous mowry shale in north central wyoming form elongate retrogradational bodies meters thick and tens of kilometers in length that are encased in shale the sandstones were deposited under different depth and oxygen conditions than were the shales the sands are extensively bioturbated and contain wave induced features oscillation ripples and hummocky stratification whereas the surrounding muds contain few biogenic structures and lack evidence of wave motion mowry sandstone units are interpreted to have been deposited by storms in shallow 10 to 30 m oxygenated water the shales that encompass these sandstones were deposited largely from turbid bottom flows in dysaerobic and anaerobic water a drop in sea level is postulated to have promoted deposition of each sandstone bed on sections of the shelf where muds had accumulated previously below wave base in oxygen poor water during low water level this region was exposed to well oxygenated water and to the effects of storms subsequent sea level rise shifted the locus of sand deposition wave base and the intersection of oxygen boundaries with the seafloor in a shoreward direction the retrogradational geometry of each sand body is explained by the shoreward migration of sand deposition during sea level rise

organic nanopore structure and fractal characteristics of wufeng and lower member of longmaxi shales in southeastern sichuan china abstract organic nanopores in shale gas reservoirs are the main storage space for free gas and adsorbed gas and directly affect the occurrence mode and movement of shale gas in this study field emission scanning electron microscopy fe sem low pressure gas n2 and co2 adsorption and mercury injection capillary pressure micp analyses were performed and interpreted with statistical and fractal analyses to investigate the organic pore structure in the upper ordovician wufeng shale o3w and the lower silurian lower member of longmaxi shale s1l it was found that organic pores in 15 samples from 8 layers of the wufeng longmaxi shale section are usually developed in discrete organic matter particles organic matter associated with clay minerals and organic matter associated with pyrite framboids the size shape and quantity of organic pores vary greatly the organic pores in wufeng formation layer 1 are densely developed in organic matter particles with relatively small sizes and irregular shapes the organic pores in the lower part of the lower member of longmaxi formation layers 3 4 and 5 are less developed and have relatively larger pore sizes with an elliptical shape in contrast the organic pores in the upper part of the lower member of longmaxi formation layers 6 7 8 and 9 are the least developed with elliptical shapes and pore sizes in between the two cases above a higher value of fractal dimension refers a more complex form and this value of whole organic pores with full range of sizes dwop is the largest and followed by organic macropores dop 50 organic pores with pore sizes between 4 nm and 50 nm dop4 50 and organic pores with pore sizes less than 4 nm dop

model assisted rock eval data interpretation for source rock evaluation examples from producing and potential shale gas resource plays abstract rock eval pyrolysis has been widely accepted by the petroleum industry as a useful technique for a quick easy and cost effective source rock evaluation however there are misconceptions and misuse of some of the existing rock eval parameters due to implicit underlying assumptions or poor understanding of the limitations which could lead to erroneous conclusions data interpretation from a perspective of hydrocarbon generation kinetics may facilitate better interpretation of the hydrocarbon generation capacity of a source rock from its thermal stability and transformational behaviors we present a model assisted approach for data interpretation from which data scatters can be viewed not only for the remaining petroleum generation potential of individual samples but also for data specific thermal decomposition path as a whole to verify whether the data come from a single kerogen population with similar kinetics and associated generation potentials moreover we propose a concept of dimensionless toc and s2 variables that effectively removes the thermal maturity overprint in the traditional toc vs s2 plot used for the determination of the kerogen type the dimensionless variables are defined by rescaling the parameters against their original values before thermal decomposition on a dimensionless plot data points from the same genetic population of source rocks align on a single line regardless of their thermal maturation levels this article demonstrates the methods and the proposed approaches for studying oil generation kinetics and resource potential using traditional rock eval data through examples from selected producing and potential shale gas plays in canadian sedimentary basins and elsewhere

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

influence of experimental temperature and duration of laboratory confined thermal maturation experiments on the evolution of the porosity of organic rich source rocks abstract to investigate the influence of the duration temperature pairs chosen for laboratory thermal maturations on the evolution of the organic matter om and porosity of the clay rich source rocks with increasing maturity long duration 104 days thermal maturations bulk molecular geochemical om characterization rock eval gc tcd gc ms and nitrogen adsorption porosimetry were applied on six type ii mudstones from the kimmeridge clay formation these results were compared with shorter duration experiments 72 h previously carried out the results show that the increase in the duration of thermal maturation experiments enhanced the degradation of heavy polar om components into saturated and aromatic hydrocarbons leading to the production of similar amounts of extractible om eom enriched in saturated and aromatic hydrocarbons then in preventing the early breaking of low energy bonds the lower temperature used for the longer duration experiments led to a less pronounced early cracking of om resulting in a different timing of gas generation this process did not influence the general evolution of the pore volume which increased during gas generation whatever the duration temperature pair chosen for maturation experiments highly oil prone samples formed lower pore volumes during gas generation increasing the duration of thermal maturation seemed nevertheless to influence the amplitude and the timing of pore alteration events that occur during gas generation leading to slightly different pore size distributions and pore volumes between short and long duration experiments however these differences remain limited suggesting that results from different time duration experiments can be easily compared

a new method for predicting sweet spots of shale oil using conventional well logs abstract in this paper a new method called sweet spot index ssi is proposed by the combination of shale oil mobility and shale reservoir fracability to predict the vertical distribution of shale oil sweet spots using conventional logs in the ssi method logging evaluation models for toc s1 volatile petroleum and mineral content are initially established mobile oil content is obtained by subtracting the amount of adsorbed oil from the total oil content which is the s1 value after the recovery of light and heavy hydrocarbons the adsorbed oil content is calculated based on the oil adsorption model established by a stepwise pyrolysis experiment the formation fracability is estimated by a combination of estimates of brittle mineral content and young s modulus formations with higher brittleness and lower young s modulus are considered better simulation candidates the ssi value is the product of the normalized mobility and the fracability index which minimizes the section of just an organic matter sweet spot i e high oil content or an inorganic sweet spot i e easily fractured and has the advantage of accurately predicting its vertical distribution in the case study the new method is successfully implemented to predict sweet spots of the es3l lower sub member of the third member of the eocene shahejie formation in the bonan sag bohai bay basin china the lower limit value of ssi is set to 0 1 based on its relationship with shale oil production the effectiveness reliability and adaptability of the ssi method have been verified by three wells in the bonan sag

silica diagenesis porosity evolution and mechanical behavior in siliceous mudstones mowry shale cretaceous rocky mountains u s a quartz in mudstones of the mowry shale cretaceous rocky mountain region takes several forms extrabasinal detrital silt some with transported overgrowths replacement of skeletal debris minor overgrowth on detrital quartz and replaced radiolaria pore filling in the intragranular pores of allochems and authigenic microquartz that is dispersed through the clay size matrix the matrix dispersed microquartz has cl character similar to the overgrowths with which it is intergrown supporting the interpretation that it is authigenic and pore filling radiolaria are widely observed in these mudrocks but are poorly preserved by partial mineral replacement quartz dolomite calcite pyrite we interpret dissolved radiolaria and possibly now cryptic diatoms as the likely source of silica for the overgrowths and microquartz through a reaction pathway that entailed the formation of opal ct lepispheres that subsequently recrystallized to microquartz a newly devised variation of the igv intergranular volume concept a parameter igvm is applied for partitioning the causes of porosity decline in mudstones all of the samples examined contain authigenic microquartz which averages around 40 of the rock volume the large volume of microquartz together with the volumes of surviving intergranular pores and pore filling solid hydrocarbon constrain the porosity to around 50 at the time of initial lepisphere formation despite the exceptional abundance of cement overall porosity decline is compaction dominated the presence of significant volumes of cement has implications for mechanical rock properties in the mowry shale which is expected to manifest brittle behavior where cements are most prominently developed

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

estimating organic maturity from well logs upper cretaceous austin chalk texas gulf coast abstract the austin chalk is both a source rock for oil and a fractured reservoir and the evaluation of its organic maturity from well logs could be an aid to exploration and production geochemical and core measurements have shown three zones of organic maturity for source materials 1 an immature zone above 6000 ft 2 a peak generation and accumulation zone from 6000 to 7000 ft and 3 a mature expulsion and migration zone below 7000 ft the response of common well logs identifies these zones true resistivity rt is low in the immature zone increases to a maximum in the accumulation zone and decreases to intermediate values in the migration zone density and neutron porosities are different in the immature zone but are nearly equal in the accumulation and migration zones correlations with conventional core analyses indicate that rt values between 9 and 40 ohm m in the migration zone reflect a moveable oil saturation of 10 to 20 in the rock matrix the moveable saturation provides oil from the matrix to fractures and is essential for sustained oil production therefore the log evaluation of moveable oil could be important in exploration

a dual porosity model for evaluating petroleum resource potential in unconventional tight shale plays with application to utica shale quebec canada unconventional tight to shale reservoirs vary from tight sandstone siltstone to organic rich mudstone shale commonly with mixed lithologies in such reservoir systems matrix pores and organic pores with different origins and distinct physical and chemical properties co exist for hydrocarbon storage traditional resource assessment methods designed for conventional reservoirs cannot handle the two pore systems properly this study proposes a dual porosity model to respond to the need for a new method in assessing hydrocarbon resource potential in such reservoir systems the dual porosity model treats the two types of pores separately and derives the resource estimates from different sources of data thus better characterizing unconventional reservoirs with complicated pore systems the new method also has the flexibility of assessing resource potential for the entire spectrum of mixed lithologies ranging from a complete tight to a pure source rock organic rich shale mudstone reservoir the proposed method is illustrated through the assessment of the in place petroleum resource potential in the upper ordovician utica shale of southern quebec canada the results of the application suggest that the proposed approach effectively handles the two pore systems in tight shale reservoirs effectively and provides a useful tool for estimating resource potential in unconventional plays

a revised method for organic porosity estimation in shale reservoirs using rock eval data example from duvernay formation in the western canada sedimentary basin studies suggest that nanometer scale pores exist in organic matter as a result of thermal decomposition of kerogen depending on the host rock lithology organic pores could be the primary storage for hydrocarbon accumulation in unconventional petroleum plays although various methods are publicly available estimation of organic porosity remains a challenge because the procedures involve certain simplification or some implicit assumptions on the calculation of initial total organic carbon toc in this study we propose a revised method to address some of these issues a model of estimating hydrocarbon expulsion efficiency is developed and incorporated into the calculation of initial toc thus producing an estimate of organic porosity with an improved mass balance the method has been tested and compared with estimates using other methods based on a rock eval data set in the literature an application of the method to a large data set from the upper devonian duvernay formation petroleum system in the western canada sedimentary basin reveals that the modification has a significant effect on the estimated organic porosity this study also indicates that organic porosity in the duvernay formation ranges greatly from none in immature intervals to 6 in highly mature and organic rich shale intervals scanning electron microscope images of immature and mature organic rich shale samples of the duvernay formation show a progressive increase in organic porosity with increasing thermal maturity supporting the proposed model calculation the presence of a large volume of organic porosity in mature shale intervals suggests a significant amount of hydrocarbon may be stored in the organic nanopores in the duvernay formation

a practical model for organic richness from porosity and resistivity logs a practical method the delta log r technique for identifying and calculating total organic carbon in organic rich rocks has been developed using well logs the method employs the overlaying of a properly scaled porosity log generally the sonic transit time curve on a resistivity curve preferably from a deep reading tool in water saturated organic lean rocks the two curves parallel each other and can be overlain since both curves respond to variations in formation porosity however in either hydrocarbon reservoir rocks or organic rich non reservoir rocks a separation between the curves occurs using the gamma ray curve reservoir intervals can be identified and eliminated from the analysis the separation in organic rich intervals results from two effects the orosity curve responds to the presence of low density low velocity kerogen and the resistivity curve responds to the formation fluid in an immature organic rich rock where no hydrocarbons have been generated the observed curve separation is due solely to the porosity curve response in mature source rocks in addition to the porosity curve response the resistivity increases because of the presence of generated hydrocarbons the magnitude of the curve separation in non reservoirs is calibrated to total organic carbon and maturity and allows for depth profiling of organic richness in the absence of sample data this method allows organic richness to be accurately assessed in a wide variety of lithologies and maturities using common well logs

atomic h c ratio of kerogen as an estimate of thermal maturity and organic matter conversion in recent years the atomic h c hydrogen to carbon ratio of kerogen as a way to assess the quality of organic matter in source rocks has been overlooked in favor of the more easily determined rock eval hydrogen index rock eval pyrolysis provides fast inexpensive quantitative mg hc g rock data without requiring kerogen isolation from the rock because of the general scatter in the data many source rock interpreters consider rock eval pyrolysis to be a screening analysis in this paper i describe the benefits of using h c ratios in source rock evaluations and present new correlations between atomic h c ratios and thermal maturity organic matter conversion and expulsion volumetrics atomic h c ratios of pyrolyzed kerogens have been correlated to the extent of thermal conversion of organic matter for both type i and type ii kerogens the excellent agreement between stoichiometric calculated hydrogen and carbon loss to observed losses from hydrous pyrolysis maturation experiments suggests that kerogen h c ratios are excellent indicators of thermal maturity for end member kerogen types these data also offer a method to estimate percent organic matter conversion provided that both the initial and present h c ratios of the kerogen are known present h c ratios can be measured and initial h c ratios can be reasonably estimated from microscopic organic analysis of kerogen for oil prone source rocks typical immature type i kerogens have h c ratios of 1 35 1 50 whereas type ii kerogens have h c ratios of 1 20 1 35 correlations of the amount of expelled oil in hydrous pyrolysis experiments to atomic h c ratio of the spent kerogen offer exploration geologists a quick estimate of oil expulsion volumes based on hydrous pyrolysis experiments measured h c ratios and calculated original toc total organic carbon values first order volumetric approximations were made on three basins containing mature source rocks results compared favorably with published approximate oil in place estimates for the williston basin bakken shale los angeles basin nodular shale and the illinois basin new albany shale

the effect of moisture on the methane adsorption capacity of shales a study case in the eastern qaidam basin in china this study investigated the effects of moisture on high pressure methane adsorption in carboniferous shales from the qaidam basin china the shale characteristics including the organic inorganic compositions and pore structure volume and surface distribution were obtained using various techniques gibbs adsorption measurements were performed over a pressure range up to 6 mpa and temperatures of 308 15 k on dry samples and moisture equilibrated samples to analyze the correlations between organic inorganic matter pore structure and moisture content on the methane sorption capacity compared to dry samples the sorption capacity of wet samples 0 44 2 52 of water content is reduced from 19 7 5 3 to 36 1 6 1 langmuir fitting is conducted to investigate moisture dependent variations of adsorbed methane density langmuir pressure and volume by combining the pore volume and surface distribution analyses our observations suggested that the main competition sites for ch4 h2o covered pores of approximately 2 7 nm whereas the effective sites for methane and water were predominantly distributed within smaller 10 nm respectively regarding the compositional correlations the impact of moisture on the amount of adsorbed methane shows a roughly linearly decreasing trend with increasing toc content ranging from 0 62 to 2 88 whereas the correlation between the moisture effect and various inorganic components is more complicated further fitting results indicate that illite smectite mixed formations are closely related to the methane capacity whereas the illite content show an evident connection to the pore structural volume and surface variations in the presence of moisture

petroleum retention in the mandal formation central graben norway abstract upper jurassic organic matter rich marine shales of the mandal formation have charged major petroleum accumulations in the north sea central graben including the giant ekofisk field which straddles the graben axis recent exploration of marginal basin positions such as the mandal high area or the sogne basin has been less successful raising the question as to whether charging is an issue possibly related to high thermal stability of the source organic matter or delayed expulsion from source to carrier the mandal formation is in part a very prolific source rock containing mainly type ii organic matter with

lowstand deltas in the frontier formation powder river basin wyoming implications for sequence stratigraphic models deposits of lowstand deltas formed on the floor of the cretaceous interior seaway of north america are found in the cenomanian lower belle fourche member of the frontier formation central wyoming sandstones located in similar distal basin locations hundreds of kilometers basinward of highstand shoreline deposits form important hydrocarbon reservoirs isolated within marine shales but interpretation of their origin has been highly controversial the distribution geometry and internal facies of these sandstones are documented by an extensive outcrop study and regional subsurface correlations to develop genetic facies models for these deposits this integrated record of lithofacies ichnofacies palynofacies paleocurrent data bedding relationships and isolith maps incorporates observations from nearly 100 measured outcrop sections and about 550 subsurface well logs four episodes of sediment progradation and subsequent transgression each left behind gradually upward coarsening deltaic sandstones that have eroded tops these deltaic sandstones have a lobate to elongate geometry basinward dipping internal clinoform bedding radiating paleocurrents a low to moderate degree of shallow marine burrowing and show variable wave influence and tidal influence on deposition delta plain paralic and nonmarine facies have been eroded from the top of deltaic successions erosion surfaces capping progradational deltaic successions are the only stratal discontinuities that can be mapped regionally and they appear to record transgressive ravinement enhanced over areas of structural uplift compared with lowstand surfaces of erosion which record the bypass of sediments basinward low accommodation during lowstands left little room for sandstones to stack vertically and successive episodes of delta progradation were offset along strike more tide influenced delta deposits formed within shoreline embayments begin page 262 defined by the topography of older wave influenced delta lobes and subtle syndepositional deformation of the basin floor standard sequence stratigraphic terminology is difficult to use in broad lowstand systems like the frontier formation because sandstones do not show simple vertical stacking patterns major stratal discontinuities can form by processes other than lowstand fluvial erosion and minor syndepositional deformation of the basin floor exerts a first order influence on depositional and sediment preservation patterns although many basin distal sandstones have been interpreted to be deposits of offshore bars shelf isolated valley fills and stranded shorelines the frontier formation examples documented here suggest that many of these deposits may be top eroded deltas formed where rivers delivered sediment to lowstand coastlines the external geometry and internal heterogeneities of hydrocarbon reservoirs found in these types of deposits reflect processes active on the low accommodation deltaic shoreline even in cases where subsequent ravinement has significantly truncated the deposits during transgression

development of organic pores in the longmaxi formation overmature shales combined effects of thermal maturity and organic matter composition abstract organic pores are considered to be the dominant contributors to total porosity and hydrocarbon storage in many source rock unconventional reservoirs in this study organic petrology focused ion beam environmental scanning electron microscopy fib sem and low pressure n2 adsorption and desorption were used to analyze six shale samples obtained from the shuanghe section changning county and wells ys118 and jy2 in the sichuan basin china results of point counting under the microscope show that alginite including type i and ii is most abundant followed by bitumen and zooclasts of graptolites the contents of alginite i alginite ii and bitumen range from 12 vol to 48 vol from 5 vol to 35 vol and from 30 vol to 48 vol respectively only few pores were found in graptolites thermal maturity macerals and palynomorphs have strong influences on the development of organic pores in the analyzed samples organic pores 10 nm in shale with a maturity of 2 5 ro in addition characteristics of organic pore in different maceral types are studied based on sem and low pressure n2 adsorption and desorption generally alginite i and solid bitumen have larger and more abundant organic pores than other macerals alginite i and solid bitumen have approximately same porosity 13 0 vol and same mean pore size 180 nm pores in a lginite i are elongated and lattice like arranged however pores in bitumen are spongy and vesicle pores with respected to alginite i alginite ii has a more complicated pattern of organic pore development some unicellular alginite ii grains contain very few nanopores whereas some aggregated alginite ii host plenty of nanoscale organic pores detailed studies on the palynomorphs of macerals suggested that alginite i is sourced from benthic algae and alginite ii are derived from phytoplankton by comparing the development of organic pores in different palynomorphs it was concluded that palynomorphs derived from different algae precursors and with distinct hydrocarbon potentials and hydrocarbon generating characteristics affect the development of organic pores in alginite macerals in the over mature stage

the neuquen super basin with more than 6000 m of sedimentary thickness and several superimposed petroleum systems the neuquen basin of argentina has all the elements to be considered a super basin the basin developed during the triassic early jurassic in a rift environment that generated a localized petroleum system continued subsidence during the early jurassic resulted in the first marine ingression los molles formation total organic carbon toc 1 7 this unit matured 120 to 55 m y a before the formation of major structures with the exception of the huincul high a fast marine flooding in a retroarc setting occurred during the latest jurassic early cretaceous at its base lies the vaca muerta formation a 50 to 1000 m thick world class source rock composed by calcareous shales and marls toc 2 9 this unit reached maturity at 95 ma when the only traps available were structures along the huincul high or stratigraphic a new marine ingression occurred during the early cretaceous depositing bituminous shales and marls agrio formation toc 2 5 that matured during the paleogene these superimposed petroleum systems combined with different structural settings gave rise to numerous plays and trapping configurations that resulted in the discovery of 14 billion boe in addition the unconventional potential of the vaca muerta is now being developed with estimated resources of 91 5 tcf and 14 3 billion bbl of oil the neuquen basin has gone through three main phases of development conventional tight and unconventional after a century of production the basin still shows a wide variety of opportunities for both conventional and world class unconventional plays

an improved hydrocarbon generation potential method for quantifying hydrocarbon generation and expulsion characteristics with application example of paleogene shahejie formation nanpu sag bohai bay basin abstract to evaluate petroleum resources it is important to quantify the hydrocarbon generation and expulsion characteristics of source rock the hydrocarbon generation potential method is an efficient model for calculating the characteristics of source rocks and evaluating the resource potential the previous hydrocarbon generation potential model was mainly established by measured rock eval pyrolysis data and due to inappropriate preservation measures an important component volatile hydrocarbon content of source rock may be significantly reduced prior methods may therefore not objectively reflect the properties of a source rock and cause unacceptable errors in the resource assessment this study proposes an improved hydrocarbon generation potential method the new method considers the initial hydrogen index hi0 and transformation ratio tr during the evolution of source rocks which can more realistically reflect the hydrocarbon generation and expulsion history of source rocks therefore the hydrocarbon evaporative loss qloss is calibrated and the hydrocarbon generation and expulsion features of source rocks are more accurately evaluated the proposed method is used to examine the effectiveness of the third member of the upper paleogene shahejie formation es3 in nanpu sag by utilizing the improved hydrocarbon generation potential model the hydrocarbon expulsion threshold of the es3 source rock is positioned at ro 0 875 the maximum hydrocarbon generation and expulsion potential qg and qe are 593 78 and 323 78 mg hc g toc respectively and the maximum hydrocarbon expulsion efficiency is 54 the maximum hydrocarbon generation and expulsion intensities are 500 104 t km2 and 250 104 t km2 respectively which locate source rock at the laoyemiao and gaoshangpu structural belts the amounts of generated and expelled hydrocarbon are 13 7 108 t and 6 9 108 t respectively and the resource potential of the tight oil of the es3 in the nanpu sag is 0 69 104 t compared with the previous method the improved hydrocarbon generation potential method limits the maximum qg and calibrates the qloss therefore the new method more objectively reflects the hydrocarbon generation and expulsion characteristics and resource prospect of the source rock

the influence of partial hydrocarbon saturation on porosity and permeability in a palaeogene lacustrine shale hosted oil system of the bohai bay basin eastern china abstract palaeogene calcareous 40 carbonate mudstones ro from 0 56 to 0 88 from the bohai bay basin were studied by combined petrographical geochemical and petrophysical analysis in order to assess and quantify the pore space pore filling and its influence on gas transport capacity toc contents ranged from 1 44 to 5 12 and porosities he determined by helium pycnometry from 1 3 to 6 4 bitumen filled porosity s1 was estimated to range between 0 3 and 2 0 based on rock eval s1 values and an assumed bitumen density of 0 90 g cm3 the true total porosity total he s1 amounts to 1 9 8 5 the in situ oil saturation so was estimated to range between 25 and 52 with two samples l69 1b and l69 2 having relatively high oil saturation 71 and 91 the conductivity of the remaining open pore space was measured on three samples with different orientations and oil saturations from 17 to 24 the effective klinkenberg corrected gas permeability coefficients range between 63 and 2000 ndarcy and permeability is highest parallel to bedding upon loading from 10 to 40 mpa confining pressure the intrinsic permeability coefficients decreased by one order of magnitude revealing a relatively high exponential stress sensitivity coefficient 0 069 mpa 1 and much lower zero stress permeability 1 416 10 6 md than most gas shales this could be due to pore plugging by ductile bitumen

seasonal and spatial variations in the chemistry of a high arctic supraglacial snow cover this paper describes the physical and chemical properties of the snowpack on john evans glacier ellesmere island canadian arctic archipelago and investigates the controls on snowpack solute concentrations and atmospheric deposition the snowpack contains three layers that are traceable across the whole glacier these represent fall accumulation that has been metamorphosed to depth hoar winter accumulation mixed with snow reworked by wind from the underlying depth hoar and spring accumulation mixed with wind reworked snow the seasonal cycle in snow chemistry closely reflects changes in the composition of the atmospheric aerosol at alert with some modification of no 3 concentrations by post depositional processes mean water weighted solute concentrations in the snowpack are largely independent of accumulation while atmospheric deposition tends to increase with accumulation this suggests that for most species wet deposition is the dominant depositional process throughout the year however concentrations of ca 2 and k increase with both accumulation and elevation implying an enhanced input from dry deposition of soil dust above 800 m elevation concentrations of so 4 2 are inversely related to accumulation especially in the winter layer suggesting a significant input from non precipitating events such as dry deposition or riming during this period of very limited snowfall

a preliminary study on the characterization and controlling factors of porosity and pore structure of the permian shales in lower yangtze region eastern china abstract permian organic rich shales occur throughout the lower yangtze region in eastern china and are potentially a future target for shale gas exploration due to the lack of data the gas potential of these permian shales is difficult to evaluate in this study a total of 22 permian shale samples were collected from two wells and their geochemical and rock property porosity characteristics were investigated the results show that the samples have a total organic carbon toc content of 0 6 17 4 wt derived from mainly gas prone kerogen with a vitrinite reflectance ro value ranging from 2 3 to 2 7 total porosity of the samples ranges between 1 and 5 5 the micropore and mesopore surface areas range between 5 41 35 69 m2 g and 3 59 11 23 m2 g respectively micropore and mesopore volumes range between 0 22 1 44 cm3 100 g and 0 67 1 76 cm3 100 g respectively total porosity and pore structure data of these samples show a correlation with toc for samples with toc 12 wt negative correlation relationships were observed toc content strongly impacts gas storage capacity of the permian shales in the lower yangtze region and the preliminary results of the present study have important implications for the shale gas play evaluation in this area

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

nanoscale pore characteristics of the lower cambrian niutitang formation shale a case study from well yuke 1 in the southeast of chongqing china the lower cambrian niutitang formation shale is one of the most important shales being studied for unconventional development in china in this work we focused on 21 core samples of niutitang shale from well yuke 1 in the southeast of chongqing to better understand their vertical reservoir characteristics and pore evolution using complementary approaches of x ray diffraction n2 and co2 adsorption petrology microscope and field emission scanning electron microscopy we conducted a series of analyses for pore volume pore size distribution surface area fractal characterization organic geochemistry petrology and mineralogy results indicate that most micropores 50 nm are composed of organic pores and inorganic pores meso macropore volume per unit of total organic carbon toc content dramatically decreases with an increase of maturity and extent of diagenesis meanwhile the toc normalized micropore volume also rapidly declines after maturity ro values were higher than 3 13 the surface fractal dimension d1 for relative n2 pressure p p0 0 5 with capillary condensation and surface fractal dimension d2 for p p0 0 5 with mono and multi layer adsorption derived from n2 sorption isotherms can be used to indicate the pore characteristics d1 is controlled by the percentages of micropore volume d2 seems to be affected by the clay mineral contents and thermal maturity

dissolution pores in shale and their influence on reservoir quality in damintun depression bohai bay basin east china insights from sem images n2 adsorption and fluid rock interaction experiments abstract shale pore characterization is crucial for understanding the mechanism of shale hydrocarbon accumulation and its effective exploitation x ray diffraction xrd optical microscopy scanning electron microscopy sem pore extraction nitrogen n2 adsorption and fluid rock interaction experiments were used to study the shale pore structure of the fourth member of the paleogene shahejie formation in the damintun depression east china the damintun shale included three types of pores organic matter pores mineral matrix pores and microfractures the dissolution pores were mainly developed between and inside the matrix minerals such as calcite dolomite and feldspar the average shale visible dissolution porosity determined using sem was 1 12 n2 adsorption analysis revealed that the less than 20 nm pores were the main reservoir space in the damintun shale fluid rock interaction experiments indicated that the degrees of dissolution of the calcite and dolomite were similar and stronger than those of the k feldspar and plagioclase the shale with a high content of carbonate minerals calcite and dolomite exhibited more intense dissolution the degree of dissolution pores development was positively correlated with total organic carbon toc and carbonate mineral calcite and dolomite contents the average contribution of the dissolution porosity to the total porosity of the shale was 18 20 however the contribution of the dissolution pores increased with increasing pore size only when the average pore diameter was larger than 12 nm this may be due to the fact that small pores diameter

pore characterization of organic rich lower cambrian shales in qiannan depression of guizhou province southwestern china abstract nine organic rich shale samples of lower cambrian black shales were collected from a recently drilled well in the qiannan depression guizhou province where they are widely distributed with shallower burial depth than in sichuan basin and their geochemistry and pore characterization were investigated the results show that the lower cambrian shales in qiannan depression are organic rich with toc content ranging from 2 81 to 12 9 thermally overmature with equivalent vitrinite reflectance values in the range of 2 92 3 25 and clay contents are high and range from 32 4 to 53 2 the samples have a total helium porosity ranging from 2 46 to 4 13 and total surface area in the range of 9 08 37 19 m2 g the estimated porosity in organic matters defined as the ratio of organic pores to the volume of total organic matters based on the plot of toc vs helium porosity is about 10 for the lower cambrian shales in qiannan depression and is far lower than that of the lower silurian shales 36 in and around sichan basin this indicates that either the organic pores in the lower cambrian shale samples have been more severely compacted than or they did not develop organic pores as abundantly as the lower silurian shales our studies also reveal that the micropore volumes determined by dubinin radushkevich dr equation is usually overestimated and this overestimation is closely related to the non micropore surface area of shales i e the surface area of meso and macro pores however the modified bet equation can remove this overestimation and be conveniently used to evaluate the micropore volumes surface area and the non micropore surface areas of micropore rich shales

recent advances in petroleum geochemistry applied to hydrocarbon exploration this paper presents a critical review of recent advances in the study of generation maturation and migration of petroleum the different source potentials for generating hydrocarbons depend on the type of kerogen in addition to the classic types i ii and iii a residual oxidized organic matter is also observed which has no potential for hydrocarbon generation coal is widely considered as a potential source for gas but some coals may generate sizeable amounts of oil as well the development of routine analytical tools particularly pyrolysis makes possible the preparation of geochemical logs that are the basis for screening samples and for interpreting other analyses among optical techniques the major subjects of discussion concern the nature of amorphous organ c matter which may encompass different chemical types of kerogen and the applicability of vitrinite reflectance techniques to type i and ii kerogens following important advances in identification of biological markers in sediments and crude oils these markers are used for oil source rock correlation and proposed for reconstruction of depositional environment and subsequent thermal evolution migration of hydrocarbons is now better understood and the importance of a hydrocarbon phase migration is widely recognized overpressuring of pore fluids is mainly responsible for expulsion of petroleum geologic models of basin evolution subsidence compaction thermal history and geochemical models hydrocarbon generation and migration become progressively available their integration int a comprehensive model should be one of the major developments in future petroleum exploration

experimental investigation of thermal maturation on shale reservoir properties from hydrous pyrolysis of chang 7 shale ordos basin abstract thermal maturity has a significant impact on hydrocarbon generation and the storage capacity within shales but explicit and quantitative characterization of that impact on continental shales is scarce to better understand how thermal maturation affects the organic and inorganic changes of the continental shale reservoirs hydrous pyrolysis was performed to simulate the maturation process toc rock eval and adsorption isotherms tests were used to obtain various geochemical parameters of the shale solid residues the results indicate that with pyrolysis temperature increasing from ambient temperature to 550 c the vitrinite reflectance increases from 0 5 to 2 5 ro and the toc total organic carbon loss weight reaches 25 regarding porosity the fraction of micro to meso pores in the shale increases with an increase in the pyrolysis temperature whereas the macro pores do not change significantly the total amount of gas adsorption does not necessarily increase as the toc is consumed but the gas adsorption capacity per unit of toc increases with increasing thermal maturity our finding provides theoretical modelling for identifying shale gas development prospective zones according to thermal maturity mapping and for predicting quantitatively the geochemical and inorganic changes that occur with thermal evolution

the effect of analytical particle size on gas adsorption porosimetry of shale abstract gas storage capacity and gas producibility of shale gas reservoirs are critically limited by shale porosity in spite of its importance porosimetric characterization of shale remains challenging due to highly heterogeneous structures small average pore sizes and wide pore size distributions this study utilizes low pressure n 2 and co 2 gas adsorption porosimetry to investigate the evolution of micro and mesopores in a suite of 11 new albany shale samples across a wide range of thermal maturity corresponding to vitrinite reflection r o values from 0 35 to 1 41 mesopore volumes follow a nonlinear evolutionary path starting with a maximum in immature shale sample 472 1 subsequent intermittent minima in mesopore volumes during early and late maturity are consistent with the transformation of kerogen during the early mature stage sample 554 2 and secondary cracking of bitumen oil at the late mature stage sample il2 respectively micropore volumes display a varying trend throughout thermal maturation and are significantly controlled by total organic carbon contents both meso and micropore volumes are positively correlated with clay content and tend to decrease with an increase in feldspar content a reduction in grain size of shale samples for gas adsorption porosimetry prominently enhances mesopore volumes whereas the effects on micropore volumes are variable these findings may be associated with the fact that smaller particles are able to attain complete adsorption equilibrium quickly which in turn reduces experimental artefacts during gas adsorption porosimetry crushing of shale not only alters the shape of gas adsorption hysteresis loops but also tends to tighten the openings of hysteresis loops by enhancing the connectivity of pores and reducing the likelihood of gas being trapped during desorption

hydrocarbon evaporative loss evaluation of lacustrine shale oil based on mass balance method permian lucaogou formation in jimusaer depression junggar basin abstract hydrocarbon evaporative loss evaluation is important for shale oil resource assessment we propose a mass balance model to evaluate the hydrocarbon evaporative loss s1 loss in this study the proposed method is applied to a large rock eval pyrolysis dataset on source rock samples from the lucaogou formation in the jimusaer depression of the junggar basin nw china as a case study to evaluate the s1 loss the results indicate that the s1 loss can range from 0 12 to 7 25 mg g rock corresponding to 11 89 loss of the generated hydrocarbons s1 loss s1 s1 loss due to evaporation before lab analysis it appears that when ro 1 3 s1 loss and s1 loss toc decreases gradually with increasing ro likely corresponding to increasing oil density as results of heterogeneous source rock compositions and increased accommodation space via the creation of organic pores of large specific surface for heavy and large hydrocarbon molecules in oil window when ro 1 3 s1 loss toc begins to increase with increasing ro as more oil crack to gaseous and light hydrocarbons that are more susceptible to evaporative loss in the case of similar ro the relative s1 loss toc varies little among the samples but the absolute s1 loss amount increases with increasing toc restricted by regional geological conditions in this study we focused on the s1 loss for lacustrine type i kerogen only and quantification of evaporative loss for other kerogen types remains a subject for further study

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

pore development of the lower longmaxi shale in the southeastern sichuan basin and its adjacent areas insights from lithofacies identification and organic matter abstract x ray diffraction xrd field emission focusing ion beam scanning electron microscopy fe fib sem nitrogen gas adsorption n2ga and geochemical analyses were performed on the lower longmaxi shale in the southeastern sichuan basin and its adjacent areas to reveal the controls of shale lithofacies and organic matter om on pore development the results showed that the lower longmaxi shale primarily comprises three types of lithofacies based on shale compositions and sedimentary environment om rich siliceous shale orss om moderate mixed shale omms and om lean argillaceous shale olas orss comprises high contents of om and siliceous minerals quartz and feldspar deposited in a deep water shelf and early semi deep water shelf environment while olas consists of high clay mineral and low om contents primarily formed in a shallow water shelf environment omms witness a transition from orss to olas in sedimentary environment and shale components om hosts a higher volume of pores per unit weight compared to inorganic minerals corresponding to 0 1878 ml g and 0 00396 ml g respectively om hosted pores are dominant in orss constituting 72 whereas olas mainly consists of mineral hosted pores comprising 63 2 om hosted and mineral hosted pores in omms exist in similar proportions namely 56 4 and 43 6 respectively differentiated diagenetic paths resulting from sedimentary environment are responsible for the differences in pore development under various shale lithofacies the thermal maturity macerals and abundance of om all play a significant role in the morphology and development of om hosted pores om hosted pores are primarily founded in migrated om mainly sapropelic type instead of structured om mainly humic type in the form of secondary pores that are derived from dry gas generation stage furthermore om hosted pore development in shale gas reservoirs is slowed or even reduced because of the weakening of shale s resistance to compaction resulting from excessively high om content

quantitative evaluation of potential organic matter porosity and hydrocarbon generation and expulsion from mudstone in continental lake basins a case study of dongying sag eastern china abstract this study presents approaches for evaluating potential organic matter porosity and hydrocarbon generation and expulsion in mudstone with strong heterogeneity in organic matter distribution in different evolution conditions of continental lake basins a total of 274 samples from the paleogene system at depth of 2770 3376 m of the niu 38 well in dongying depression eastern china were analyzed based on rock eval pyrolysis to investigate the corresponding potentials of organic matter porosity and hydrocarbon generation and expulsion the study shows that organic matter type controls hydrocarbon generation and expulsion potential in the continental lake basin strong heterogeneity was observed in the total organic carbon distribution among different organic matter types thus leading to significant gaps in hydrocarbon generation and expulsion potential type i organic matter exhibits high hydrocarbon generation and expulsion potential which is distributed within 24 07 105 79 mg g rock generation and 6 67 74 32 mg g rock expulsion with an average of 44 2 mg g rock and 18 91 mg g rock respectively types iii and ii 2 organic matter exhibit limited hydrocarbon generation and expulsion potential particularly type iii the hydrocarbon generation and expulsion potential of types iii and ii 2 organic matter is only distribute within 0 67 2 67 mg g rock generation and 0 32 1 20 mg g rock expulsion respectively thus indicating that these types are basically inert organic matter results show that type i organic matter with an initial total organic carbon content ranging from 6 28 to 22 0 can generate potential organic matter porosity varying from 4 15 to 26 21 capability to generate potential organic matter porosity decreases significantly from type i to types ii 1 ii 2 and iii organic matter initial total organic carbon is only within the range of 0 76 1 47 and potential organic matter porosity is between 0 10 and 0 41 for type iii organic matter the result shows that the potential organic matter pores generated by different organic matter types exhibit considerable differences between the samples in the continental lake basin the described methodology in this work allows a higher resolution in the evaluation on the heterogeneity of hydrocarbon source rock in vertical sequence thus it is an important way in the evaluation of potential source rock in the early exploration of unconventional oil and gas resources in the mudstone

relationships between porosity organic matter and mineral matter in mature organic rich marine mudstones of the belle fourche and second white specks formations in alberta canada abstract this study presents approaches for evaluating hybrid source rock reservoirs within tight rock petroleum systems the emerging hybrid source rock reservoir shale play in the upper cretaceous second white specks and belle fourche formations in central alberta canada is used as an example to evaluate organic and inorganic compositions and their relationships to pore characteristics nineteen samples from a 77 5 m long core were analyzed using organic petrography organic geochemistry several methods of pore characterization and x ray powder diffraction xrd the lower part of the studied section includes quartz and clay rich mudrocks of the belle fourche formation with low carbonate content whereas the upper portion contains calcareous mudrocks of the second white specks formation strata are mineralogically composed of quartz plus albite 18 56 wt carbonates calcite dolomite ankerite 1 65 wt clays illite kaolinite chlorite 15 46 wt and pyrite 2 12 wt petrographic examinations document that organic matter represents marine type ii kerogen partly biodegraded with limited terrestrial input vitrinite reflectance r o 0 74 0 87 t max values 438 446 c and biomarkers indicate mid maturity within the oil window the relatively poor remaining hydrocarbon potential expressed as an s2 value between 2 1 and 6 5 mg hc g rock may result from an estimated 60 83 of the original kerogen having been converted to hydrocarbons with the bulk having migrated to adjacent sandstone reservoirs however the present day remaining total organic carbon toc pd content remains relatively high 1 7 3 6 wt compared with the estimated original toc o of 2 4 5 0 wt the calculated transformation ratio of 60 83 suggests that the remaining 17 40 wt of kerogen is able to generate more hydrocarbons the studied section is a tight reservoir with an average swanson permeability of 3 37 10 5 md measured on two samples and total porosity between 1 7 and 5 0 vol 3 vol on average the upper part of the sandy belle fourche formation with slightly elevated porosity values 3 5 5 vol likely represents the interval with the best reservoir properties in the studied core interval total pore volume ranges between 0 0065 and 0 0200 cm 3 g measured by a combination of helium pycnometry and mercury immersion mesopores 2 50 nm are the most abundant pores and occupy 34 67 of total porosity or a volume of 0 0030 0 0081 cm 3 g in comparison micropores 3 g and macropores 50 nm reach up to 57 with the exception of some samples failing to indicate the presence of this pore fraction volume 0 0000 0 0107 cm 3 g macroporosity is mostly responsible for variations in total porosity as suggested by macroporosity s strongest correlation with total porosity within the section the relatively narrow ranges of toc and minerals contents among measured samples limit our ability to further deconvolute factors that influence changes in total porosity and pore size distribution

quantitative evaluation of toc organic porosity and gas retention distribution in a gas shale play using petroleum system modeling application to the mississippian barnett shale abstract shale reservoirs have not benefited from advanced modeling tools to the extent of conventional resources thus an approach is proposed to integrate key parameters such as total organic carbon toc content methane adsorption and organic porosity in a basin simulator original toc has an impact on both gas generated volume and gas retention within source rocks the conversion of organic matter into hydrocarbons also creates additional intraparticle kerogen porosity in which oil and gas can be stored in this work a method is proposed to calculate the evolution of toc organic porosity and gas retention capacity free versus adsorbed through time in shale gas by means of petroleum system modeling gas adsorption potential on organic material is calculated using a langmuir model which accounts for pressure temperature and remaining solid toc organic porosity is calculated as the result of the change of the organic matter from solid immature kerogen to less dense fluid hydrocarbons during thermal maturation the method is tested on a 3d basin model of the mississippian barnett shale in texas usa the computed organic porosity varies from 0 in immature zones to a maximum of 4 of rock volume in organic rich and mature zones computed retained methane in the lower barnett shale ranges between 20 and 60 scf t from 1 to nearly 3 kg m3 and is mainly concentrated in mature areas of the basin simulated results are consistent with available barnett shale data possible effects of assumptions made in the approach and perspectives are discussed

geochemical screening of source rocks and reservoirs the importance of using the proper analytical program abstract geochemical screening is routinely integrated into larger exploration and sometimes development programs that also include assessments of the geological setting petrophysics mechanical properties of the rock etc the rock eval analytical equipment and its classical basic bulk rock method have been developed mainly to characterize potential source rock intervals in petroleum systems however with the increasing interest in unconventional plays it has been recently demonstrated that the use of modified pyrolysis temperature regimes improves the quantification of hydrocarbons still present in oil impregnated samples in spite of their availability the use of such modified pyrolysis temperature regimes still remains scarce among users of pyrolysis data e g exploration geologists and geochemists reservoir engineers petrophysicists and other geoscientists several cases were selected to portray how different analytical programs are necessary to obtain less biased and more accurate answers to critical questions during prospect and play evaluations and appraisals samples originating from conventional and unconventional plays in the greater permian basin of west texas wolfcamp spraberry formations the dj basin in colorado niobrara formation the williston basin lower bakken shale and source rock reservoirs in the middle east were analysed each using three known different pyrolysis methods namely the institut fran ais du petrole s basic bulk rock reservoir and shale play the shale play and reservoir pyrolysis methods yield oil in place estimates 20 42 higher than those yielded by the basic bulk rock method on the same sample e g for the niobrara formation 87 bbl oil ac ft bulk method 118 bbl oil ac ft reservoir method 119 bbl ac ft shale method for the lower bakken 194 bbl oil ac ft bulk method 246 bbl oil ac ft shale method in addition a mature source rock interval believed to contain gas prone organic matter type iii based solely on toc and pyrolysis data was re interpreted as composed mainly of amorphous oil prone kerogen following a multi component study which included transmitted and reflected light organic petrography these results present unequivocal evidence that underestimating the importance of selecting the proper analytical program can change interpretations dramatically