experimental determination of dynamic pore throat structure characteristics in a tight gas sandstone formation with consideration of effective stress abstract in this study a robust and pragmatic technique has been developed to experimentally quantify the dynamic characteristics of microscopic pore throat structure with consideration of effective stress in a tight gas sandstone formation more specifically porosity and permeability of highly heterogeneous core samples collected from a tight gas reservoir were measured and then thin section analysis as well as other analyses with the scanning electron microscopy and x ray diffraction techniques were performed to identify and classify the particle composition grain size clay minerals and pore and throat types subsequently pore throat structure such as its connectivity radius and size distributions were determined by conducting pressure controlled mercury injection and rate controlled mercury injection tests respectively in addition the nuclear magnetic resonance nmr technique is employed to examine effect of stress sensitivity on porosity and permeability as well as pore and throat radius under different pore pressures by decreasing the pore pressure from 30 0 to 1 0 mpa and the corresponding effective stress was increased from 0 to 29 0 mpa as such the pores and throats become smaller and the average proportion of volume controlled by nano scale throat with the radius less than 100 nm increased from 48 01 to 48 90 while the average volumetric proportion controlled by micron scale and submicron scale throats was decreased from 46 57 to 46 37 the shrinkage of pores and throats resulted in an average reduction for porosity and absolute permeability from 10 43 to 6 84 and from 0 01237 to 0 00501 md respectively moreover samples with a lower permeability showed more serious permeability damage illustrating that they experience a stronger stress sensitivity than those with a higher permeability

the characteristics of movable fluid in the triassic lacustrine tight oil reservoir a case study of the chang 7 member of xin anbian block ordos basin china abstract the micropore throat structure of a tight oil reservoir is complex and its movable fluid distribution differs from that of a conventional reservoir by using nuclear magnetic resonance nmr and centrifugation the movable fluid distribution in the chang 7 tight reservoir in the xin anbian block of the ordos basin was quantitatively evaluated combined with the results of the physical property and high pressure mercury intrusion experiments the effects of the porosity permeability pore size distribution and micropore throat structure on the movable fluid distribution in the chang 7 tight reservoir were analyzed the nmr results show that the t2 spectral morphology of the chang 7 tight oil reservoir in the xin anbian block can be characterized by three main patterns with different amplitudes of front and post peaks the front peak corresponds to the scale of small pores and the post peak corresponds to the scale of large pores based on the three t2 spectrum patterns the chang 7 tight reservoir can be divided into three types type 1 reservoir with more small pores and fewer large pores type 2 reservoir with similar amounts of small and large pores and type 3 reservoir with fewer small pores and more large pores thus the characteristics of these three types of reservoirs can be determined the movable fluid parameters were calculated by nmr and centrifugation the movable fluid saturation of the type 1 reservoir is low with an average of 20 38 and the average movable fluid porosity is 1 47 the type 2 and type 3 reservoirs have higher movable fluid contents of 40 79 and 47 04 respectively the average movable fluid porosities of the type 2 and type 3 reservoirs are 3 37 and 3 48 respectively the greater number of small pores and smaller number of large pores in the type 1 reservoir result in weak correlations of the movable fluid with the physical properties and pore throat structure parameters the movable fluid saturation is negatively correlated with the maximum pore radius mainstream throat radius and maximum mercury saturation and is strongly positively correlated only with the porosity of the large pores as the number of large pores increases the movable fluid saturation strongly correlates with the property parameters pore size distribution and pore throat structure parameters in the type 2 and type 3 reservoirs the movable fluid saturations are positively affected by the maximum pore radius median radius mainstream throat radius and effective porosity but are strongly negatively correlated only with the radius mean value these results indicate that the fluid mobility of these two types of reservoirs can be promoted by the pore throat system to obtain favorable seepage characteristics

geologic framework of the mississippian barnett shale barnett paleozoic total petroleum system bend arch fort worth basin texas this article describes the primary geologic characteristics and criteria of the barnett shale and barnett paleozoic total petroleum system tps of the fort worth basin used to define two geographic areas of the barnett shale for petroleum resource assessment from these two areas referred to as assessment units the u s geological survey estimated a mean volume of about 26 tcf of undiscovered technically recoverable hydrocarbon gas in the barnett shale the mississippian barnett shale is the primary source rock for oil and gas produced from paleozoic reservoir rocks in the bend arch fort worth basin area and is also one of the most significant gas producing formations in texas subsurface mapping from well logs and commercial databases and petroleum geochemistry demonstrate that the barnett shale is organic rich and thermally mature for hydrocarbon generation over most of the bend arch fort worth basin area in the northeastern and structurally deepest part of the fort worth basin adjacent to the muenster arch the formation is more than 1000 ft 305 m thick and interbedded with thick limestone units westward it thins rapidly over the mississippian chappel shelf to only a few tens of feet the barnett paleozoic tps is identified where thermally mature barnett shale has generated large volumes of hydrocarbons and is 1 contained within the barnett shale unconventional continuous accumulation and 2 expelled and distributed among numerous conventional clastic and carbonate rock reservoirs of paleozoic age vitrinite reflectance ro measurements show little correlation with present day burial depth contours of equal ro values measured from barnett shale and typing of produced hydrocarbons indicate significant uplift and erosion furthermore the thermal history of the formation was enhanced by hydrothermal events along the ouachita thrust front and mineral wells newark east fault system stratigraphy and thermal maturity define two gas producing assessment units for the barnett shale 1 a greater newark east fracture barrier continuous barnett shale gas assessment unit encompassing an area of optimal gas production where dense impermeable limestones enclose thick 300 ft 91 m barnett shale that is within the gas generation window ro 1 1 and 2 an extended continuous barnett shale gas assessment unit covering an area where the barnett shale is within the gas generation window but is less than 300 ft 91 m thick and either one or both of the overlying and underlying limestone barriers are absent

surface energy balance and melt thresholds over 11 years at taylor glacier antarctica 11 years ablation 18 cm a 1 was dominated by sublimation with very few occurrences of melt 42 days during 11 years results also indicated that above freezing air temperatures did not necessarily result in melt and in turn melt occurred during subfreezing air temperatures under some conditions for air temperatures near freezing low wind speed was critically important for melt initiation according to the model subsurface melt away from rocks and sediment in the ice occurred three times more frequently than surface melt occurs no deeper than 50 cm below the glacier surface and was small never exceeding 8 by mass the magnitude of subsurface melting and the energy balance indicate that taylor glacier ice is intermediate in optical properties between snow and blue ice

the enigma of oil and gas field growth growth in estimates of recovery in discovered fields is an important source of annual additions to united states proved reserves this paper examines historical field growth and presents estimates of future additions to proved reserves from fields discovered before 1992 field level data permitted the sample to be partitioned on the basis of recent field growth patterns into outlier and common field sets and analyzed separately the outlier field set accounted for less than 15 of resources yet grew proportionately six times as much as the common fields because the outlier field set contained large old heavy oil fields and old low permeability gas fields its future growth is expected to be particularly sensitive to prices a lower bound of a range of estimates of futu e growth was calculated by applying monotone growth functions computed from the common field set to all fields higher growth estimates were obtained by extrapolating growth of the common field set and assuming the outlier fields would maintain the same share of total growth that occurred from 1978 through 1991 by 2020 the two estimates for additions to reserves from pre 1992 fields are 23 and 32 billion bbl of oil in oil fields and 142 and 195 tcf of gas in gas fields

factors controlling prolific gas production from low permeability sandstone reservoirs implications for resource assessment prospect development and risk analysis low permeability reservoirs from the greater green river basin of southwest wyoming are not part of a continuous type gas accumulation or a basin center gas system in which productivity is dependent on the development of enigmatic sweet spots instead gas fields in this basin occur in low permeability poor quality reservoir rocks in conventional traps we examined all significant gas fields in the greater green river basin and conclude that they all occur in conventional structural stratigraphic or combination traps we illustrate this by examining several large gas fields in the greater green river basin and suggest that observations derived from the greater green river basin provide insight to low permeability gas charged sandstones in other basins we present evidence that the basin is neither regionally gas saturated nor is it near irreducible water saturation water production is both common and widespread low permeability reservoirs have unique petrophysical properties and failure to fully understand these attributes has led to a misunderstanding of fluid distributions in the subsurface an understanding of multiphase effective permeability to gas as a function of both varying water saturation and overburden stress is required to fully appreciate the controls on gas field distribution as well as the controls on individual well and reservoir performance low permeability gas systems such as those found in the greater green river basin do not require a paradigm shift in terms of hydrocarbon systems as some have advocated we conclude that low permeability gas systems similar to those found in the greater green river basin should be evaluated in a manner similar to and consistent with conventional hydrocarbon systems to date resource assessments in the greater green river basin have assumed a widespread continuous type resource distribution failure to recognize some of the fundamental elements of low permeability reservoirs has led to an underappreciation of the risks associated with exploration and development investment decisions in these settings and likely a significant overestimation of available resource levels

hydrocarbon generation and expulsion characteristics of eocene source rocks in the huilu area northern pearl river mouth basin south china sea implications for tight oil potential abstract in recent years new oil reservoirs have been discovered in the eocene tight sandstone of the huilu area northern part of the pearl river mouth basin south china sea indicating good prospects for tight oil exploration in the area exploration has shown that the huilu area contains two main sets of source rocks the eocene wenchang e2w and enping e2e formations to satisfy the requirements for further exploration in the huilu area particularly for tight oil in eocene sand reservoirs it is necessary to re examine and analyze the hydrocarbon generation and expulsion characteristics based on mass balance this study investigated the hydrocarbon generation and expulsion characteristics as well as the tight oil resource potential using geological and geochemical data and a modified conceptual model for generation and expulsion the results show that the threshold and peak expulsion of the e2w source rocks are at 0 6 vitrinite reflectance and 0 9 vitrinite reflectance respectively there were five hydrocarbon expulsion centers located in the western eastern and northern huizhou sag and the southern and northern lufeng sag the hydrocarbon yields attributed to e2w source rocks are 2 4 1011 tons and 1 6 1011 tons respectively with an expulsion efficiency of 65 the e2e source rock threshold and peak expulsion are at 0 65 vitrinite reflectance and 0 93 vitrinite reflectance respectively with hydrocarbon expulsion centers located in the centers of the huizhou and lufeng sags the yields attributed to e2e source rocks are 1 1 1011 tons and 0 2 1011 tons respectively with an expulsion efficiency of 20 using an accumulation coefficient of 7 13 the eocene tight reservoirs could contain approximately 1 3 1010 tons to 2 3 1010 tons with an average of 1 8 1010 tons of in place tight oil resources highest recoverable coefficient can reach 17 18 indicating that there is significant tight oil potential in the eocene strata of the huilu area

surface albedo measurements over snow and blue ice in thematic mapper bands 2 and 4 in dronning maud land antarctica ground based observations of broadband narrowband in landsat thematic mapper bands 2 0 52 0 60 m and 4 0 76 0 90 m and bidirectional reflectance are used to study the albedo of blue ice and snow the measured broadband albedos for blue ice and snow are 0 60 and 0 78 respectively the narrowband albedos in bands 2 and 4 for snow are 0 97 and 0 86 respectively and for blue ice are 0 87 and 0 51 respectively the measurements are point values and used to verify existing weighting functions between the broadband and narrowband albedos blue ice data do not comply with the existing functions furthermore a new function for blue ice is derived a simple two stream model is used to illustrate the behavior of the snow and ice albedo as a function of reflection and absorption the bidirectional reflectance measurements are used to derive bidirectional reflectance distribution functions brdfs for snow and blue ice the brdf of blue ice exhibits a maximum brightening in the forward limb around a zenith angle close to the solar zenith angle indicating specular reflectance of blue ice which is not visible for snow and glacier ice surfaces

integrated nmr and fe sem methods for pore structure characterization of shahejie shale from the dongying depression bohai bay basin abstract of particular importance for shale reservoirs is the evaluation of pore structure characteristics that significantly influence a reservoir s storage capacity and flow mechanisms due to the presence of multiscale pore sizes in shale reservoirs a series of experiments including total organic carbon toc rock eval analysis x ray diffraction xrd field emission scanning electron microscopy fe sem and nuclear magnetic resonance nmr were conducted on shale samples from the lower submember of the third member es3l and upper submember of the fourth member of the eocene shahejie formation es4u in the dongying depression bohai bay basin the results indicate that calcite averaging 30 5 and clay averaging 29 1 are the dominant minerals based on analysis of geochemistry data the organic matter type of ly1 is i and ii four main types of reservoir spaces are observed in ly1 intercrystalline pores dissolved pores intergranular pores and microfractures shale samples in the study area have a wide range of pore size distributions and complex pore structures because of the wide range of transversal relaxation time t2 distributions and messy t2 curves of the nmr experiment per the nmr results the percentage of micropores mesopores and macropores ms1 ms2 and ms3 were calculated and the relationships between these proportions and pore structure parameters porosity permeability t2 cutoff value t2 geometric mean value and structural characteristics were investigated ms1 increased with a decrease of t2 cutoff values and geometric mean values suggesting that shale samples with higher ms2 and ms3 have better pore structures and strong percolation potential under similar porosity conditions samples with high permeability have a larger ms3 value laminated and layered shale samples have larger values of ms2 and ms3 than massive shale therefore ms1 ms2 and ms3 are useful to indicate the quality of pore structures the smaller the ms1 the better the pore structure finally taking three representative shale samples as an example the relationships between ms1 ms2 and ms3 and the effectiveness of the reservoir were discussed using the logging profile of ly1 the research concludes that ms1 ms2 and ms3 are effective nmr parameters for evaluating the effectiveness of the reservoir

history of the newark east field and the barnett shale as a gas reservoir david martineau is a certified petroleum geologist and received his b s degree in geology from the university of texas in 1960 he joined pitts in 1972 and is the exploration manager pitts has been involved in the barnett play since its inception prior to pitts he worked for prudential drilling funds and coastal states gas producing company now el paso in 2006 the newark east field was the largest producing gas field in texas and according to the energy information administration eia latest reserves estimate eia 2006 tables b2 and b4 newark east field ranks third in the nation and second in the nation in terms of production the newark east field has generated considerable attention because the gas is produced from the barnett shale as opposed to conventional sandstone conglomerate or carbonate reservoirs the field was discovered in 1981 by mitchell energy corporation mec in wise county texas located in the fort worth basin in north central texas george mitchell founder and chief executive officer of mec had the vision and leadership behind mec s continued exploration and research for the correct technology to extract gas from this unconventional gas reservoir dan steward was the chief geologist for mec during the critical exploration development of the barnett shale and was honored by aapg with the 2007 outstanding explorer award the development of the field started slowly and only 100 wells were completed between 1981 and 1990 in 1998 a major breakthrough in completion technique occurred when water fracturing replaced gel fracturing from 1997 to 2006 more than 5829 wells were put on production and hundreds of additional wells were drilled completed or waiting on a pipeline the field has been divided into two areas 1 the original core area where the barnett sits on top of the viola limestone

volcanic rocks as prolific gas reservoir a case study from the qingshen gas field in the songliao basin ne china abstract the qingshen gas field with over 100 billion cubic meters bcms of proven gas reserves was discovered recently in the upper jurassic lower cretaceous strata of the songliao basin northeastern china the stratigraphic relationships and gas chemical compositions indicate mixed gas sources dominantly from the upper jurassic lower cretaceous coals and associated dark mudstones underlying the gas reservoirs with minor contribution from deep inorganic sources the gas reservoirs consist mainly of volcanic rocks rhyolite and tuff with some production also from the conglomerate gas charge into these largely volcanic rock reservoirs appears to coincide with the peak gas generation in the deep upper jurassic lower cretaceous coal measures the presence of several thick lacustrine mudstone beds in the upper cretaceous strata as regional caprocks and relatively mild structural deformation since the late cretaceous are among the favorable conditions for the preservation of large volume of natural gases in these relatively deep gas reservoirs the gas yields are the highest in the paleomorphological highs where fractures and secondary porosity are well developed in the gas reservoirs

should sibumasu be renamed sibuma the case for a discrete gondwana derived block embracing western myanmar upper peninsular thailand and ne sumatra the luxi nujiang suture which extends from yunnan into myanmar is shown to continue into thailand and the malacca strait it forms the eastern boundary of a discrete block here called the irrawaddy block which was formerly considered to be part of gondwana derived sibumasu it has a distinct palaeozoic succession with thick lower permian glacially influenced diamictite bearing marine mass flow intervals deposited at the gondwana margin the rest of sibumasu east of the suture also has local thin lower permian diamictite units however they have been interpreted as ice rafted deposits laid down at a greater distance from the gondwana margin in ne sumatra a diamictite bearing carboniferous lower permian succession has also been described as of mass flow origin and it is suggested that it is also part of the irrawaddy block it requires that the bounding suture is aligned se beneath the malacca strait in the late cretaceous palaeogene the dextral india australia oceanic transform propagated onshore as a strike slip fault bounding on the east the north going india plate it disrupted the irrawaddy block and for much of its length coincided with the line of the earlier suture insofar as the acronym sibumasu was coined to include sumatra consideration should be given to renaming this block sibuma

monterey formation porcelanite reservoirs of the elk hills field kern county california oil and gas production from monterey formation porcelanite at the elk hills field in california s san joaquin basin occurs from intervals that have quartz phase mineralogy however characteristics differ from chert and porcelanite reservoirs of the coastal california monterey formation in that matrix porosity is more typical of the opal ct phase petroleum storage is mostly in the matrix and natural fracture patterns are dominantly small scale several elk hills reservoirs located on two large anticlines produce from porcelanite the 29r ab and 31s d are the most productive porcelanite reservoirs each having cumulative oil production of about 40 million bbl although interbedded with siliceous shale sandstone and dolomite most of the porous reservoir rock is laminated porcelanite porosity averages between 20 and 25 and is evenly distributed throughout the porcelanite as extremely small pores ranging in size from 1 to 10 m matrix permeability averages 0 8 md but flow of oil and gas is enhanced through fractures parallel with and perpendicular to bedding higher than anticipated porosity may be in part due to migration of hydrocarbons into the porcelanite reservoirs while still in opal ct phase mineralogy the dissolution of opal ct and precipitation of quartz occurs in place and the resulting quartz phase mineral structure mimicks the porous opal ct framework

architecture of a sandstone uranium reservoir and the spatial distribution of its internal carbonaceous debris a case study of the zhiluo formation eastern ordos basin northern china abstract the sandstone of the middle jurassic zhiluo formation in the eastern ordos basin provides the opportunity for conducting a critical case study of the architecture and internal carbonaceous debris cd distribution of a sandstone uranium reservoir located in a field outcrop in shiwan the 16 24 m thick outcrop section is a sandstone dominated subaqueous distributary channel succession in which six lithofacies types se st sm sp sh and fl occur in a predictable order of repeated fining upward cycles these facies emphasize that the dominant structures had been deposited under lower flow regime conditions various groups of associated facies have been identified as six distinct architectural elements intrachannel units longitudinal bar transverse bar diagonal bar dune complex and abandoned channel deposits within a framework of five orders of bounding surfaces these elements with specific lithofacies associations and spatial relationships indicate that the subaqueous distributary channel had involved in four stages of formation channel occurring channel flooding channel waning and channel abandonment moreover as one of the most significant reductants in the sandstone succession the cd occurs in the form of channel lags and is concentrated in the middle and lower parts of the lag deposit zones the spatial distribution of cd within the studied succession is controlled by the sandstone architecture and the cd rich zones are preserved exclusively upon the basal surfaces of intrachannel units longitudinal and transverse bars this study can be helpful for exploring the distribution of metallogenic flow field as well as the restriction of the reductants on interlayer oxidation

continuous hydrocarbon accumulation over a large area as a distinguishing characteristic of unconventional petroleum the ordos basin north central china abstract global petroleum exploration is currently undergoing a strategic shift from conventional to unconventional hydrocarbon resources unconventional hydrocarbons in tight reservoirs show characteristics distinct from those of conventional hydrocarbon sources hosted in structural and stratigraphic traps the characteristic features include the following a hydrocarbon source and reservoir coexist porosity and permeability are ultra low nano pore throats are widely distributed hydrocarbon bearing reservoir bodies are continuously distributed there is no obvious trap boundary buoyancy and hydrodynamics have only a minor effect and darcy s law does not apply phase separation is poor there is no uniform oil gas water interface or pressure system and oil or gas saturation varies examples of unconventional hydrocarbon accumulations are the mesozoic tight sandstone oil province and the upper paleozoic tight sandstone gas province in the ordos basin north central china generally continuous hydrocarbon accumulation over a large area is a distinguishing characteristic of unconventional hydrocarbon sources because of the great potential of unconventional petroleum resources it is believed that research on such resources will be at the forefront of the future development of petroleum geology

high resolution sequence stratigraphy sedimentology and reservoir quality evaluation of the yaojia formation in the longxi area of the western slope songliao basin china abstract delta front sand bodies with large remaining hydrocarbon reserves are widespread in the upper cretaceous yaojia formation in the longxi area of the western slope songliao basin china high resolution sequence stratigraphy and sedimentology are performed based on core observations well logs and seismic profile interpretations an evaluation of the reservoir quality of the yaojia formation is critical for further petroleum exploration and development the yaojia formation is interpreted as a third order sequence comprising a transgressive systems tract tst and a regressive systems tract rst which spans 4 5 myr during the late cretaceous within this third order sequence nine fourth order sequences fs9 fs1 are recognized the average duration of a fourth order sequence is approximately 0 5 myr the tst fs9 fs5 mostly comprises subaqueous distributary channel fills mouth bars and distal bars which pass upward into shallow lake facies of the tst top fs5 the rst fs4 fs1 mainly contains subaqueous distributary channel and interdistributary bay deposits based on thin sections x ray diffraction xrd scanning electron microscope sem and high pressure mercury intrusion hpmi analyses a petrographic study is conducted to explore the impact of the sedimentary cyclicity and facies changes on reservoir quality the yaojia sandstones are mainly composed of lithic arkoses and feldspathic litharenites the sandstone cements mostly include calcite illite chlorite and secondary quartz occurring as grain coating or filling pores the yaojia sandstones have average core plug porosity of 18 55 and permeability of 100 77 10 3 m2 which results from abundant intergranular pores and dissolved pores with good connectivity due to the relatively coarser sediments and abundant dissolved pores in the feldspars the fs4 fs1 sandstones have better reservoir quality than the fs9 fs5 sandstones developing relatively higher porosity and permeability especially the fs1 and fs2 sandstones the source reservoir cap rock assemblages were formed with the adjoining semi deep lake mudstones that were developed in the nenjiang and qingshankou formations this study reveals the deposition and distribution of the delta front sand bodies of the yaojia formation within a sequence stratigraphic framework as well as the factors controlling the yaojia sandstones reservoir quality the research is of great significance for the further exploration of the yaojia formation in the longxi area as well as in other similar lacustrine contexts

combining rate controlled porosimetry and nmr to probe full range pore throat structures and their evolution features in tight sands a case study in the songliao basin china abstract to better understand reservoir quality and to produce accurate petrophysical interpretations it is necessary to understand complex and heterogeneous pore throat structures in tight sands and to develop a technique to reveal the full range of pore and throat distributions in this study in order to characterize the features and evolutions of pore throat structures nine samples from the lower cretaceous tight gas sandstone in the songliao basin of china are measured by nuclear magnetic resonance nmr rate controlled porosimetry rcp and scanning electron microscopy sem throats with bifractal structures are found in these tight sands and can be divided into a backbone formation bf region and a percolation region using rcp data because i throats in the percolation region record treelike pore structures and are predominant in small pore spaces and ii a good correlation exists between nmr derived t 2 relaxation times and the rcp derived radius of throats the throat distribution obtained via rcp can be used to calibrate the nmr psd and then to partition the psd into distributions of pore bodies and throats these data indicate that i throats are more common than pore bodies in pore spaces of tight sands with lower permeability ii pore bodies are connected to throats from both the bf and percolation regions in which the fluid mobility in pore bodies is mainly controlled by the pore to throat ratio ptr which is related to the intersection throat of these two regions and iii compaction dissolution clay cementation and sediment properties e g rock compositions have different impacts on the evolutions of pore bodies and throats in which larger ptr values in tight sands are mainly produced by compaction and pore bridging clay cementation and lower contents of pore bodies are commonly related to abundant plastic compositions and pore bridging clay cementation

late triassic paleomagnetic result from the baoshan terrane west yunnan of china implication for orientation of the east paleotethys suture zone and timing of the sibumasu indochina collision abstract in order to better understand the paleogeographic position of the baoshan terrane in the northernmost part of the sibumasu block during formation of the pangea supercontinent a paleomagnetic study has been conducted on late triassic basaltic lavas from the southern part of the baoshan terrane in the west yunnan region of southwest china following detailed rock magnetic investigations and progressive thermal demagnetization stable characteristic remanent magnetizations chrms were successfully isolated from late triassic niuhetang lava flows the chrms are of dual polarity and pass fold and reversal tests with magnetic carriers dominated by magnetite and subordinate oxidation induced hematite we thus interpret them as a primary remanence this new paleomagnetic result indicates that the baoshan terrane was located at low paleolatitudes of 15 n in the northern hemisphere during late triassic times together with available paleomagnetic data from the baoshan terrane and surrounding areas a wider paleomagnetic comparison supports the view that the east paleotethys ocean separated the sibumasu and indochina blocks and closed no later than late triassic times we argue that the currently approximately north to south directed changning menglian suture zone is very likely to have been oriented nearly east to west at the time of the sibumasu indochina collision

assessing aquitard hydraulic performance from hydrocarbon migration indicators surat and bowen basins australia abstract basin hydrodynamic assessment methods are being applied to australia s developing coal seam gas csg to liquefied natural gas lng export developments in the queensland s bowen and surat basins technical challenges include the need to predict the cumulative impacts of csg production on formation pressure in adjacent great artesian basin aquifers and assess to what degree if any there may be fugitive methane liberated from the reservoir but not captured by production wells both these challenges require an understanding of the distribution of aquitard hydraulic sealing performance we use hydrocarbon systems analysis to illuminate basin scale geological seal performance of the low permeability strata and provide baseline data on hydrocarbons in groundwater we collected indicators of hydrocarbons including 1 drill stem wireline and production test sample analysis 2 staining fluorescence and streaming hydrocarbon occurrences from drill cuttings and core and 3 mud log gas detector data this data was allocated to stratigraphic horizons mapped and compared to the geographic stratigraphic location of source rocks conventional and unconventional reservoired hydrocarbons and aquitard sealing strata and faults we found asymmetric trapping of conventional hydrocarbon reservoirs with eastern basin leakage and western basin preservation indications of some thermogenic gas in the walloon coal measures exist yet maturity indicators are sub thermogenic suggesting that although much of the walloon coal measures gas is biogenic thermogenic gas may have previously migrated into the walloon coal measures from elsewhere stratigraphically below the walloon coal measures hydrocarbon migration indicators are often clustered along lineations such as the moonie goondiwindi and burunga leichhardt fault systems at the top of the walloon coal measures hydrocarbon migration indicators are clustered along the northeastern subcrop edge of the basin where the muddy strata at the top are either thin or eroded suggesting vertical leakage occurred to the overlying springbok sandstone aquifer whilst we can see where seals are either more or less effective at this stage we cannot make a quantitative assessment of background methane flux to surface or potential future proportional allocation of methane flux to natural vs anthropogenic causes

lacustrine tight oil accumulation characteristics permian lucaogou formation in jimusaer sag junggar basin abstract the permian lucaogou formation of jimusaer sag in the southeast region of the junggar basin is a typical area recently attracting tight oil reservoir research efforts in china commercial oil has been obtained from many wells in this region the main lithological formation comprises thick mudstones two sweet spots exhibiting high porosity and permeability are interbedded in the mudstones the sweet spots comprise alternating thin layers of silt fine sandstones carbonatites and mudstones numerous core samples were analyzed to establish the hydrocarbon generation and storage potential of lucaogou formation s lithological units in this region the test results indicate that although the tight sandstones have a certain hydrocarbon generation potential mudstones are evidently higher quality source rocks the silt fine sandstones reservoir quality is best among the three rock types biomarker evidence shows the difference between the upper and the lower section lucaogou formation oil corresponding to the mudstone layer extracts within the upper and lower sweet spot respectively despite its thickness the thick bedded mudstone average thickness 80 m between the upper and lower sweet spots does not appear to contribute to the oil reservoirs since the distance between the thick mudstone and the sweet spot is quite large and the entire formation has generally low permeability migrating from the thick mudstone to the sweet spot is difficult hence oil in the sweet spots can be concluded to be from the adjacent mudstone to our knowledge this is the first study reporting this finding

east flank of the sibumasu block in nw thailand and myanmar and its possible northward continuation into yunnan a review and suggested tectono stratigraphic interpretation abstract the east flank of the sibumasu block was a passive continental margin and in nw thailand is marked by the absence of the autochthonous middle permian triassic platform carbonates which are widespread across the rest of sibumasu further west instead the carbonates are represented by hemipelagic cherts mudstones and sandstones including turbidites during the northward drift of sibumasu following its early permian rifting from gondwana an accretionary complex was present where palaeotethyan pelagic rocks as old as devonian were subducted beneath the sukhothai volcanic arc at the time of sibumasu s collision with the sukhothai arc beginning in the middle triassic the accretionary complex was thrust westwards across the east flank of sibumasu it is suggested that in the late triassic the thrust pile which had been the accretionary complex underwent erosion and was the source of terrigenous clastic rocks deposited further west in a foredeep basin the boundary of sibumasu s east flank with the permo triassic carbonate platform further west is the arcuate mae ping nam teng fault system notwithstanding later cenozoic strike slip displacement those faults as well as the mae yuam fault are interpreted to have had an earlier history of westward directed indosinian thrusting northwards in myanmar and yunnan the sibumasu permo triassic carbonate shelf continues as the shan plateau and baoshan block the east flank is represented by the changning menglian belt and the palaeotethys cryptic suture in thailand possibly joins with the lancangjiang suture

hydrogeochemistry and gas compositions of the uinta basin a regional scale overview the geochemistry of formation fluids water and hydrocarbon gases in the uinta basin utah is evaluated at the regional scale based on fluid sampling and compilation of past records the deep formation water is dominated by na cl type where halite dissolution has the greatest effects on water chemistry its distribution and composition is controlled by both the lithology of geological formations and regional hydrodynamics the origin of the saline waters in the southeastern basin is interpreted to be a mix of ancient evaporatively concentrated seawater with meteoric water recharged in the geological past which has experienced water rock interactions at the basin scale three dimensional mapping of the dissolved solid contents further reveals that 1 in the northern uinta basin bordering the uinta mountains significant flushing of the deep basinal brines up to 6 km 3 7 mi depth by meteoric water has occurred and 2 in the central basin groundwater discharge areas along the green river valley regional upwelling of saline waters from 2 to 3 km 1 2 to 1 8 mi depth is occurring moreover gas composition and water gas stable isotope characteristics in the central to southeastern basin indicate the presence of a deep thermogenic and regionally continuous gas deposit in particular gases sampled in this region from the wasatch formation and mesaverde group indicate a similar source rock type iii kerogen of the deeply buried thermally mature mesaverde group in the central to northern basin as well as migration from the natural buttes gas field toward the southeastern basin evidence for biogenic methane formation is observed only in the upper green river formation in the central to northern uinta basin here the organic rich immature green river shales experience meteoric water invasions and formation fluid chemistry and stable isotope compositions are diagnostic of microbial methanogenesis

the permian fusulinoidean faunas of the sibumasu and baoshan blocks their implications for the paleogeographic and paleoclimatologic reconstruction of the cimmerian continent abstract permian fusulinoidean faunas occur in mainly four stratigraphic levels in the baoshan block of west yunnan and the sibumasu block of southeast asia which constituted part of the eastern cimmerian continent the oldest fauna from the upper part of the dingjiazhai formation in the baoshan block consists of pseudofusulina eoparafusulina and a new boultoniid genus and is assignable to the yakhtashian artinskian the second one which occurs in the basal part of the ratburi limestone and its equivalent strata in the sibumasu block is represented by monodiexodina and is probably referable to the bolorian kungurian the third fauna composed of eopolydiexodina rugososchwagerina yangchienia chusenella jinzhangia and several other genera is dated to the murgabian wordian and occurs in the lower part of the shazipo and daaozi formations in the baoshan block and the main part of the ratburi limestone in the sibumasu block the youngest fauna of probably dzhulfian wuchiapingian age is found in the upper part of the ratburi limestone and contains nanlingella reichelina codonofusiella and a few staffellid genera a smaller foraminiferal genus shanita found from the upper part of the ratburi limestone and the upper part of the shazipo formation is also an important element of the foraminiferal assemblage near the midian dzhulfian capitanian wuchiapingian boundary in the baoshan and sibumasu blocks in the eastern cimmerian continent low generic diversity throughout the permian and the paucity of tethys characterizing neoschwagerinid and verbeekinid genera during middle permian time are two remarkable features of the permian fusulinoidean faunas in the cimmerian continent the generic diversity of permian fusulinoidean faunas in space and time gradually increases from the early permian to late middle permian as well as from the eastern cimmerian areas to western ones the temporal increase of the generic diversity can be explained by the northward drift of the cimmerian continent during permian time in contrast the lower generic diversity of the eastern cimmerian permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude thus the western cimmerian continent was more proximal to the tropical tethyan domain than its eastern part in addition the middle permian cimmerian paleobiogeographic region is likely to be subdivided into two subregions the western tethyan cimmerian and the eastern gondwanan cimmerian based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity the scarce occurrence or total absence of these essentially tethys indicating fusulinoideans in the baoshan and sibumasu blocks suggests that the eastern cimmerian continent was still far from the equatoro tropical cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the permian the eastern cimmerian areas finally migrated into a tropical zone by the late triassic judging from well developed carnian sponge coral buildups in the chaiburi formation in the sibumasu block

natural hydraulic fracturing of tight gas sandstone reservoirs piceance basin colorado natural fractures form preferred pathways for basinal fluid flow and associated heat and mass transport in gas sandstone reservoirs with low matrix permeability fractures provide flow pathways between organic rich source and reservoir layers during gas charge and between matrix pores hydraulic fractures and the well bore during production while the formation of natural fractures has previously been associated with gas generation and pore fluid pressure increase through a process referred to as natural hydraulic fracturing other driving mechanisms such as stress changes by tectonic or exhumation processes remained viable alternatives to test whether these mechanisms contributed to fracture development we investigated the spatial and temporal distribution of fracture formation and its relationship to gas generation migration and charge in sandstone of the cretaceous mesaverde group across the entire production interval on a basinwide scale using fluid inclusion microthermometry of crack seal fracture cement formed concurrently with fracture opening we observed temperature trends that when compared with temperature evolution models of the formation date fracture formation between 41 and 6 ma in the northern and between 39 and 6 ma in the southern piceance basin the onset of fracture formation 20 30 m y prior to maximum burial eliminates changes in stress state associated with exhumation as a mechanism for triggering the onset of fracture formation instead calculated paleo pore fluid pressures of 40 90 mpa 5800 13 000 psi during fracture opening and the presence of methane rich inclusions in fracture cement suggest that fracture formation was aided by high pore fluid pressures during gas generation in organic rich shales and coals and associated charging of adjacent and interlayered sandstone reservoirs a 10 20 m y age progression in the onset of fracture formation from deeper to shallower horizons of the mesaverde group is consistent with gas generation and onset of fracture formation activated by burial temperature with limited upward migration of gas at this stage of reservoir evolution this age progression with depth is inconsistent with fracture formation triggered by changes in stress conditions associated with tectonic or structural processes expected to affect the entire formation synchronously our observations are thus most consistent with fracture formation by natural hydraulic fracturing in response to gas generation in interbedded source layers and reservoir charge based on widespread observations of fractures with similar structural and diagenetic attributes we consider natural hydraulic fracture formation in response to thermocatalytic gas generation to be a fundamental mode of brittle failure in otherwise structurally quiescent basins

study on the cretaceous turbidite and reservoir features in the qingshankou formation in northern songliao basin ne china abstract based on analysis of well and drilling data cores sediment grains and 3d seismic data four types of turbidites slope fan channelized laminated and sublacustrine fan turbidite are identified in members 1 and 2 of the qingshankou formation in northern songliao basin the slope fan turbidite is located in members 1 and 2 of the qingshankou formation it is dominated by silt and fine sand and is distributed in an sn trending ribbon zone along the slope break at delta front in the western part of the basin the channelized turbidite is located at the bottom of member 1 of the qingshankou formation it is dominated by silt and fine sand and is distributed in an sn trending strip shaped zone along the qijia gulong sag with funnel shaped sublacustrine fans at the end the laminated turbidite body is located in member 2 of the qingshankou formation it is dominated by siltstone and argillaceous siltstone and is distributed continuously in a tongue shaped zone along the northern delta front towards the lacustrine region with belt like distributaries at the central part and sublacustrine fans at the end low permeability and low yield lithologic reservoirs are formed near the delta front within the slope fan turbidite and channelized turbidite there are sweet spots in local regions where reservoir reform techniques are required to attain high industrial yields laminated turbidite and sublacustrine fans can form unconventional and continuous reservoirs that generally have no natural productivity industrial production is impossible until horizontal drilling and multistage volume fracturing are employed therefore the research results are important to the exploration of unconventional oil and gas reservoirs in northern songliao basin

comprehensive 1000 year climatic history from an intermediate depth ice core from the south dome of berkner island antarctica methods dating and first results a 181 m deep ice core drilled in 1994 95 on the south dome of berkner island antarctica was analyzed for stable isotopes major ions and microparticle concentrations samples for ion chromatography were prepared by using a novel technique of filling decontaminated sample from a device for continuous ice core melting directly into the sample vials the core was dated through identification of volcanic horizons and interpolative layer counting the core together with a similar core from the north dome reveals a 1000 year history of relatively stable climate temporal variations in the two cores deviate from each other owing to changing patterns of regional scale circulation the best correspondence between them is found for msa delta 18 o accumulation rate and a sea salt proxy show only negligible correlation which suggests a complex meteorological setting increasing annual accumulation is observed for the last 100 years a period of increased sea salt concentrations started around ad 1405 as has also been observed in other cores microparticle concentrations are on average 1220 particles 1 0 mu m diameter ml 1 they are enhanced from ad 1200 to 1350 possibly because of a higher atmospheric mineral dust load or because local volcanic activity was stronger than previously thought microparticles and nh4 show marked but multiple and very irregular sub annual peaks long term stacking of 1 year data intervals yields seasonal maxima in austral spring or mid summer respectively post depositional redistribution was observed for msa no3 and f at volcanic horizons

spontaneous potential key to understanding continuous and conventional gas in upper cretaceous sandstones deep eastern greater green river basin southwest wyoming spontaneous potential sp log data from wells in the deep eastern greater green river basin ggrb suggest that what appears to be overpressured pervasive gas at high saturation in upper cretaceous sandstones outside conventional fields is gassy water with gas present at uneconomically low saturation sandstones of the lewis shale and mesaverde group within conventional trap fields in the deep eastern ggrb exhibit normal sp deflections indicating saline formation water with low formation water resistivity that yields calculated water saturations less than 50 however in deep basin areas outside conventional traps these upper cretaceous sandstones generally exhibit reversed sp signatures reflecting anomalously low salinity formation water with anomalously high that yields calculated greater than 60 uneconomically low gas saturations are corroborated by lack of commercial gas production from reversed sp sandstones despite 1 prominent gas shows during drilling 2 significant overpressure and 3 log measured porosity and resistivity that often are indistinguishable from those observed with commercially productive normal sp sandstones within conventional traps anomalously low salinity water in deep basin sandstones outside conventional traps is proposed to result from dilution of original saline formation water by fresh water expelled during smectite clay conversion to illite with increasing temperature burial depth low permeability of deep basin sandstones retards escape of the added fresh water which contributes to overpressure and to deceptively high formation resistivity although the upward transition to more saline formation water is gradational mapped top of reversed sp cuts across stratigraphic boundaries with relief exceeding 2000 ft 610 m it is unclear whether regional continuous gas in reversed sp sandstones has been at low saturation since the onset of gas migration or whether saturations were higher prior to the influx of fresh water what is reasonably certain is that subsequent to gas migration fresh water influx in the deep basin regionally diluted original saline formation water outside conventional traps similar formation water salinity of normal sp sandstones of the lewis shale and mesaverde group within deep basin conventional traps suggests that high saturation gas and associated irreducible saline formation water in these fields are locked in accumulations unaffected by subsequent fresh water influx

testing the basin centered gas accumulation model using fluid inclusion observations southern piceance basin colorado the upper cretaceous mesaverde group in the piceance basin colorado is considered a continuous basin centered gas accumulation in which gas charge of the low permeability sandstone occurs under high pore fluid pressure in response to gas generation high gas pressure favors formation of pervasive systems of opening mode fractures this view contrasts with thatofothermodelsoflow permeabilitygasreservoirsinwhich gas migrates by buoyant drive and accumulates in conventional traps with fractures an incidental attribute of these reservoirs we tested the aspects of the basin centered gas accumulation model as it applies to the piceance basin by determining the timing of fracturegrowth and associated temperature pressure and fluid composition conditions using microthermometry and raman microspectrometry of fluid inclusions trapped in fracture cement that formed during fracture growth trapping temperatures of methane saturated aqueous fluid inclusions record systematic temperature trends that increase from approximately 140 to 185 c and then decrease to approximately 158 c over time which indicates fracture growth during maximum burial conditions calculated pore fluid pressures for methanerich aqueous inclusions of 55 to 110 mpa 7977 15 954 psi indicate fracture growth under near lithostatic pressure conditions consistent with fracture growth during active gas maturation and charge lack of systematic pore fluid pressure trends

determination of static and dynamic characteristics of microscopic pore throat structure in a tight oil bearing sandstone formation in this study an integrated and practical framework has been developed to quantify the static and dynamic characteristics of microscopic pore throat structure in a tight oil bearing sandstone formation experimentally thin sections were prepared out of core samples collected from a tight formation while corresponding analyses were respectively performed by using the scanning electron microscopy sem and x ray diffraction xrd techniques in addition to pore types and clay minerals the size fraction and distribution of grains were identified and classified pore and throat size distributions were then determined by using pressure controlled mercury injection pmi and rate controlled mercury injection rmi respectively to quantify the changes in microscopic pore throat structure after brine flow tests subsequently displacement experiments of waterflooding and surfactant flooding were performed to determine the upper and lower cutoff value of the movable throat radius rock grains primarily containing fine sand and silt are found to possess complex compositions while both intergranular pores and intragranular dissolution pores are dominant nano throats may have developed in a tight formation due to small radii of pores and throats compared to the pore size distribution throat radius is found to be reduced by 13 9 after brine flow tests while the cutoff value of movable throat can be decreased to 0 019 m from 0 033 m by using a surfactant

coupling relationship between tight sandstone reservoir and gas charging an example from lower permian taiyuan formation in kangning field northeastern ordos basin china abstract the lower permian taiyuan formation is a lithic abundant tight gas sandstone reservoir in the kangning field northeastern ordos basin to clarify the gas accumulation process in tight gas sands the relationship between the densification of taiyuan formation sandstones and gas charging is analyzed core porosities of the taiyuan formation are mostly below 10 and air permeabilities are below 1 md the sandstone reservoirs are characterized by strong heterogeneity dissolution pores and large amounts of micropores in clay minerals dominate the storage space this porosity is the result of the impact of diagenesis porosity evolution modeling confirmed well the prediction of the period of sandstone densification 225 215 ma based on the basin analysis as well as diagenetic calibration strong compaction dominated the physical property porosity and permeability reduction with cementation as a subordinate factor the integration of burial history and fluid inclusion data suggested that large quantities of gas migrated into the taiyuan sandstone reservoirs from 176 ma to 80 ma when the reservoirs were already tight porosity

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

three deep resource plays in the san joaquin valley compared with the bakken formation a continuous oil accumulation is one that is pervasive throughout a large area and is not affected by natural hydrodynamic influences three source rocks in the san joaquin valley of california are actively producing hydrocarbons and represent potential continuous oil accumulations the monterey kreyenhagen and moreno formations the energy information administration announced in 2014 that there are potentially 15 billion bbl of recoverable oil in the monterey formation in california spiking huge interest such a resource would make the monterey by far the largest continuous oil accumulation in north america this number has since been reduced dramatically to 600 million bbl of oil for the state and 21 million bbl of oil within the san joaquin valley in this study the subsurface character of the bakken formation of north dakota is compared with the three source rocks in the san joaquin valley at oil window depths to characterize these reservoirs hundreds of well logs core descriptions and mud logs were studied a technique to rank character of oil show data was developed in which interesting possibly interesting or not interesting wells were located on thermal maturity maps interesting wells have significant oil shows whereas not interesting wells have minor or no shows in the bakken formation the character of the oil show correlates with well productivity applying this same classification to the san joaquin valley source rocks leads to a more disappointing conclusion although there are oil shows in the source rocks of the san joaquin valley at oil window depths suggesting the presence of a continuous oil accumulation the distribution of shows is both laterally and vertically heterogeneous and not predictable moreover recent attempts to produce from source rocks at these depths have not been economically successful we conclude that the three source rocks in the san joaquin valley represent heterogeneous and discontinuous oil accumulations at oil window depths in the subsurface likely there are billions of barrels of oil in these discontinuous oil accumulations source rocks in the bakken are rated as world class source rocks in the san joaquin valley are good to excellent quality however the quality of the oil shows in the san joaquin valley appears poorer than the bakken formation it is possible that effective drainage between the source rocks and the up dip reservoirs has left large volumes of the source rocks at oil window depths with only residual oil saturation complex structural and stratigraphic architecture heterogeneity and continuity create issues of predictability for optimal areas to target rapid rates of subsidence over the past few million years and accompanying thrusting and folding resulted in a complex subsurface pressure regime the lack of clear hydraulic fracture targets analogous to the middle bakken further complicates drilling decisions and likely deliverability in addition the oil windows in the san joaquin valley are significantly deeper than the bakken formation which would result in substantially higher well cost recent drilling results support this study and suggest that heterogeneous and discontinuous oil accumulations in the san joaquin are unlikely to become economic without dramatic changes in technology

chemometric differentiation of crude oil families in the san joaquin basin california chemometric analyses of geochemical data for 165 crude oil samples from the san joaquin basin identify genetically distinct oil families and their inferred source rocks and provide insight into migration pathways reservoir compartments and filling histories in the first part of the study 17 source related biomarker and stable carbon isotope ratios were evaluated using a chemometric decision tree cdt to identify families in the second part ascendant hierarchical clustering was applied to terpane mass chromatograms for the samples to compare with the cdt results the results from the two methods are remarkably similar despite differing data input and assumptions recognized source rocks for the oil families include the 1 eocene kreyenhagen formation 2 eocene tumey formation 3 4 upper and lower parts of the miocene monterey formation buttonwillow depocenter and 5 6 upper and lower parts of the miocene monterey formation tejon depocenter ascendant hierarchical clustering identifies 22 oil families in the basin as corroborated by independent data such as carbon isotope ratios sample location reservoir unit and thermal maturity maps from a three dimensional basin and petroleum system model five families originated from the eocene kreyenhagen formation source rock and three families came from the overlying eocene tumey formation fourteen families migrated from the upper and lower parts of the miocene monterey formation source rocks within the buttonwillow and tejon depocenters north and south of the bakersfield arch the eocene and miocene families show little cross stratigraphic migration because of seals within and between the source rocks the data do not exclude the possibility that some families described as originating from the monterey formation actually came from source rock in the temblor formation

oil charging model and controlling factors revealed by an online nuclear magnetic resonance nmr system abstract it is very difficult to simulate the charging process of crude oil under experimental conditions due to the low porosity and permeability of tight sandstone however simulations are important for revealing the mechanism of formation of tight oil and the oil water distribution characteristics as well as for enhancing the oil recovery efficiency in this study we established a new method called nuclear magnetic resonance coupling displacement nmr dp to simulate the tight oil charging process online the nmr dp method has the advantages of high precision velocity recyclability and the ability to reflect the distribution of fluids in the micropores of a tight rock we conducted a simulation experiment involving the charging of crude oil into eight sandstone samples from gaotaizi in the qijia longhupao area of the songliao basin the results of this experiment were combined with those of microscopic measurements conducted on the pore structure i e nuclear magnetic resonance nitrogen adsorption high pressure and rate controlled mercury injections and micron computed tomography in this way we clarified the charging process and its controlling factors e g physical properties and wettability and established a tight oil charging model the results indicate that the oil charging saturation was controlled by several factors including the charging pressure physical properties pore throat structure and mineral composition of the rock a smaller radius of the pore throat corresponded to a lower oil charging saturation and higher starting pressure gradient the lower the content of clay and carbonate minerals and the higher the content of feldspar mineral the higher the oil saturation oil mainly occurred in the larger pores while residual water mainly occurred in the smaller pores the charging process was divided into four stages an exponential rapid growth stage a logarithmic slow growth stage a linear slow growth stage and a quasi stationary stage the method established in this paper is expected to be helpful for analyzing the distribution law of oil and water in tight sandstone areas thereby aiding in the prediction of sweet spots and development of tight oil

geologic significance and optimization technique of sweet spots in unconventional shale systems abstract crude oil in unconventional shale systems present as tight oil and shale oil accumulates inside an oil kitchen in formations with coexistent sources and reservoirs organic matter present in oil shale is not yet mature and requires heating to convert it into crude oil oil exploration in shale systems involves the exploration of shale oil retained in source rocks and tight oil rich zones located near source rocks tight oil is a type of realistic unconventional oil resources in china the marked increase in potential shale oil reserves and exploration of these reserves will result in a shale oil revolution similar to that experienced for shale gas based on a systematic comparison of geologic features of shale systems in the us and china the geologic significance of the sweet spots in shale systems is proposed this zone contains an abundance of unconventional oil in shale systems that can be explored and developed under current economic and technical conditions the sweet spot zone refers to the zone in the tight oil rich zone which has industrial value within the scope of matured high quality source rocks on the plane the sweet spot interval refers to the high productivity interval of tight oil which has industrial value through artificial stimulation the main aim of oil exploration in shale formations is to identify the sweet spots the distribution of the economic sweet spots in shale systems is evaluated by overlapping the geologic engineering and economic sweet spots resource assessment techniques the identification of logging data properties high resolution 3d seismic surveys horizontal well production from well pads and artificial reservoir development of sweet spots in oil bearing shale formations can assist efficient development of oil globally shale formations contain a significant volume of oil reserves currently stimulated reservoir volume srv techniques in horizontal wells in marine shale gas formations in the united states have average peak productivity cycles of 10 15 years to achieve commecial oil production in lacustrine shale systems in china it is important to utilize large formation thicknesses and the high abundance of organic matter in addition the development of practical and economic techniques will result in an increase of productivity of tight oil and shale oil by 30 50 million tons as well as the economic development of oil in lacustrine shale systems in china

petrofacies prediction and 3 d geological model in tight gas sandstone reservoirs by integration of well logs and geostatistical modeling abstract these effective reservoir rocks that can have sufficient porosity and permeability and hydrocarbon accumulations determine economic reserves and high yield of tight oil and gas understanding the origin and distribution of these effective reservoir rocks is important for sorting out sweet spots in tight reservoirs multiple scale analyses from the microscopic via drill core to single wellbore have been conducted to examine reservoir heterogeneity of the upper paleozoic shanxi formation in the southeastern ordos basin five sandstone petrofacies have been defined in terms of texture and framework composition detrital matrix diagenesis and pore types quartz arenite tuffaceous quartz arenite ductile lithic lean sub litharenite ductile lithic rich sandstone and tightly carbonate cemented sandstone the various petrofacies show fundamentally different pathways of diagenetic and reservoir quality evolutions due to the complexity of texture and detrital composition in the shanxi formation directly related to the provenance and depositional environment quartz arenites and ductile grain lean sub litharenites both form effective reservoir rocks by translating petrofacies to well log signatures corrected from petrographic and core analysis data a model based on factor analysis has been built to predict petrofacies at the well scale for investigating the distribution of each petrofacies at the field scale sequential indicator simulation method has been used to construct a 3 d petrofacies model with facies conditioning the isopach maps of quartz arenites and ductile lithic lean sub litharenites have been made from the 3 d petrofacies model to quantify their areal distributions and to define the sweet spots by combining isopach maps of these effective reservoir rocks and gas production data from well tests the concept of reservoir petrofacies is an important tool for the characterization of tight sandstone reservoirs

tight oil accumulation mechanisms of the lucaogou formation in the jimsar sag nw china insights from pore network modeling and physical experiments abstract pore network modeling and physical experiments were employed to understand the migration and accumulation of tight oil in the lucaogou formation of the jimsar sag junggar basin china the pore structure characteristics of tight rock samples were statistically analyzed from which some representative network models were constructed the estimated petrophysical properties of these networks e g porosity permeability and pore throat size distribution agree well with those obtained from experiments which justified the effectiveness of our models the experiments and simulations of oil migration into tight rocks suggest that there are mainly two different types of accumulation patterns i e rapid growth pattern and consistent growth pattern which are characterized by s shaped and modified s shaped correlations of oil saturation and pressure gradient respectively oil accumulation mainly occurs in the middle stage however the increment of oil saturation of consistent growth pattern is much slower than that of rapid growth pattern the water oil relative permeability curves which describe the fluid transport capabilities during oil migration were also computed from simulations the effects of coordination number aspect ratio as well as clay volume were analyzed results show that a core sample having better connectivity and more homogeneous pores and throats facilitates the oil migration however a higher clay volume impedes oil accumulation and decreases the final oil saturation this work not only provides a better understanding of tight oil accumulation mechanisms but also supplies an alternative avenue to study multiphase flow in tight rocks

the phuket terrane a late palaeozoic rift at the margin of sibumasu abstract it is widely accepted that sibumasu rifted from gondwana in the late palaeozoic but the rifts themselves have not previously been documented in southeast asia this paper identifies the pre middle permian kaeng krachan group of upper peninsular thailand as the infill of one such rift which is given the name phuket terrane indirect evidence suggests the rift infill is several kilometres thick and glacially influenced diamictites are conspicuous in the succession there are significant similarities with the 3 km thick pre middle permian rift infill of the carnarvon basin of western australia east of the khlong marui fault belt the succession is thinner and diamictites are a minor component a tectono stratigraphic model is proposed involving gondwana glaciers dropping their load at the present western margin of the phuket terrane from where it was re sedimented in the rapidly subsiding marine rift basin it is suggested that the khlong marui fault formed part of the eastern boundary of the rift system the three pagodas fault belt similarly juxtaposes different pre middle permian successions rifting ceased in the early permian and a passive margin formed as the mesotethys ocean widened the upper part of the kaeng krachan group and the overlying ratburi limestone representing the post rift sequence

tectonic depositional and diagenetic history of monterey formation miocene central san joaquin basin california the miocene monterey formation in the central san joaquin basin of california consists of biogenic siliceous rocks with a significant terrigenous clastic component correlation of electric logs in conjunction with analysis of outcrop sections core samples and paleontologic data suggests that deposition of the monterey was controlled by an interplay of basin geometry san andreas related tectonics fluctuations in sea level and changes in climate the basin is bounded on the east by the sierran magmatic arc complex and on the west by the san andreas fault during the late saucesian through early mohnian 20 10 ma the basin was reshaped by tectonism related to the migrating mendocino triple junction creating a broad gently sloping shelf to the east that cut off the supply of clastics to the central basin with the subsequent evolution of the san andreas fault the salinian block was emplaced along the western basin margin restricting the seaway and permitting low oxygen nutrient rich waters to occupy the basin as a result laminated organic rich fine grained pelagic to hemipelagic sediments of the monterey formation were deposited a warmer climate during saucesian through luisian time with less intensive upwelling le to more calcareous less siliceous sedimentation a cooling trend during late miocene time 10 5 ma increased upwelling activity diatom productivity in the water column and deposition of diatomaceous debris although turbidites accumulated on the basin floor and terrigenous clastics were deposited on the eastern shelf relatively undiluted diatomaceous deposits developed on outer shelves and slopes atop anticlinal banks generated by wrench tectonism and in some areas of the basin floor a mid mohnian eustatic sea level rise caused fine grained deposition to extend onto the eastern shelf slightly later a mid late mohnian period of exceptionally cool temperatures resulted in the most extensive development of upwelling related siliceous sediments throughout the basin with diagenesis these deposits formed the siliceous shales and porcelanites of the monterey formation high sedimentation rates coincident with a eustatic drop in sea level led to clastic progradation in latest miocene time as the basin filled analysis of organic matter from cores of the monterey formation shows that kerogen type reflects overall sedimentation trends samples from northern and eastern areas contain abundant terrestrial organic matter whereas samples from western areas mostly contain marine kerogens source potential is thus strongly influenced by geographic locality as well as lithology maturity of kerogen was assessed using vitrinite reflectance thermal alteration indices and pyrolysis techniques the latter two appear to be the more reliable indicators of organic matter maturity in the monterey formation of the san joaquin valley although much of the monterey formation in the study area may be thermally immature portions are probably generating hydrocarbons today in deep synclinal areas

a review of shale wettability characterization using spontaneous imbibition experiments abstract wettability is an important reservoir property that can affect the distribution and migration of geofluids within shale reservoirs which significantly influences the occurrence state of methane in shale pore systems and the selection of fracturing fluids during shale gas exploitation the wettability characteristics of organic matter om rich shale are much more complicated than those of conventional reservoir rocks with a relatively homogeneous composition in addition the low porosity and extremely low permeability as well as the strong heterogeneity of shale complicate the evaluation of shale wettability as a result traditional wettability tests including contact angle measurements and oil water displacement experiments are inapplicable for shale samples consequently spontaneous imbibition experiments become a practical and effective way to establish the wettability characteristics of different shales this paper reviews shale wettability characterization using spontaneous imbibition experiments and discusses the close relationship between shale wettability and pore structure as reported in the literature most shale samples can imbibe both water and oil which indicates the co existence of water wet and oil wet connected pore spaces and the mixed wet property of shales however different shales show a range of oil and water imbibition behaviors indicating the wettability differences amongst them this review reveals that the development degrees of water and oil wet pores within shale determine its wettability as well as its imbibition behaviors and four simplified pore network models are proposed for more water wet more oil wet mixed wet and intermediate wet shale samples respectively this work also shows the pronounced effects of thermal maturity on shale pore structure development and shale wettability characteristics consequently a simplified and empirical wettability evolution model with four stages only considering the effect of thermal maturity is established in this study

solar heating rates and temperature profiles in antarctic snow and ice observations of temperature maxima at about 10 cm depth in cold antarctic snow during summer have previously been explained by proposing that solar heating is distributed with depth whereas thermal infrared cooling is localized at the surface the solid state greenhouse an increase in temperature from the surface to 10 cm depth t 4 k found by rusin 1961 on the antarctic plateau was successfully reproduced by schlatter 1972 in a combined radiative transfer and heat transfer model

total petroleum system assessment of undiscovered resources in the giant barnett shale continuous unconventional gas accumulation fort worth basin texas undiscovered natural gas having potential for additions to reserves in the mississippian barnett shale of the fort worth basin north central texas was assessed using the total petroleum system assessment unit concept and a cell based methodology for continuous type unconventional resources the barnett paleozoic total petroleum system is defined in the bend arch fort worth basin as encompassing the area in which the organic rich barnett is the primary source rock for oil and gas produced from paleozoic carbonate and clastic reservoirs exploration technology and drilling in the barnett shale play have rapidly evolved in recent years with about 3500 vertical and 1000 horizontal wells completed in the barnett through 2005 and more than 85 of the them completed since 1999 using framework geology and historical production data assessment of the barnett shale was performed by the u s geological survey using vertical wells at the peak of vertical well completions and before a transition to completions with horizontal wells the assessment was performed after 1 mapping critical geological and geochemical parameters to define assessment unit areas with future potential 2 defining distributions of drainage area cell size and estimating ultimate recovery per cell and 3 estimating future success rates two assessment units are defined and assessed for the barnett shale continuous gas accumulation resulting in a total mean undiscovered volume having potential for additions to reserves of 26 2 tcfg the greater newark east fracture barrier continuous barnett shale gas assessment unit represents a core producing area where thick organic rich siliceous barnett shale is within the thermal window for gas generation ro 1 1 and is overlain and underlain by impermeable limestone barriers pennsylvanian marble falls limestone and ordovician viola limestone respectively that serve to confine induced fractures during well completion to maximize gas recovery the extended continuous barnett shale gas assessment unit which had been less explored defines a geographic area where barnett shale is 1 within the thermal window for gas generation 2 greater than 100 ft 30 m thick and 3 where at least one impermeable limestone barrier is absent mean undiscovered gas having potential for additions to reserves in the greater newark east assessment unit is estimated at 14 6 tcf and in the less tested extended assessment unit a mean resource is estimated at 11 6 tcfg a third hypothetical basin arch barnett shale oil assessment unit was defined but not assessed because of a lack of production data

pore structure wettability and spontaneous imbibition of woodford shale permian basin west texas abstract even after more than 30 years of exploration and production low total recovery of shale gas

wettability and connectivity of overmature shales in the fuling gas field sichuan basin china the fuling gas field in sichuan basin china has produced greater than 1 5 1010 m3 0 53 tcf of natural gas from overmature upper ordovician wufeng and lower silurian longmaxi shales to systemically investigate the characteristics of wettability and connectivity and to understand the underlying causes of production behavior we study five samples of wufeng and longmaxi shales with different total organic carbon contents and mineral compositions complementary approaches include mercury intrusion capillary pressure micp contact angle measurement spontaneous imbibition and saturated diffusion and tracer both nonsorbing and sorbing migration mapped via laser ablation inductively coupled plasma mass spectrometry according to measured contact angles and imbibition tests conducted on aqueous deionized water and brine and oleic n decane phases wufeng and longmaxi shales are strongly oil wet and moderately strong water wet the lower boundary of estimated permeability obtained from n decane imbibition can reach 137 nd which is higher than the geometric mean permeability derived from the micp method 5 5 68 8 nd effective diffusion coefficients of the wufeng and longmaxi shales are in the range of 10 13 m2 s 1 1 10 12 ft2 s tests of imbibition and saturated diffusion using tracer containing brine show that concentrations of nanometer sized tracers decrease rapidly a factor of 10 over a migration distance of a few millimeters from the sample edge suggesting the presence of poorly edge connected water wet pores sparsely connected hydrophilic pores mixed wettability and highly restricted pathways collectively contribute to the limited migration of nano sized tracers which probably results in the production behavior of initial steep decline and low overall recovery in the fuling gas field

reevaluating the source and accumulation of tight oil in the middle permian lucaogou formation of the junggar basin china abstract the middle permian lucaogou formation in the jimusar sag junggar basin nw china is a world class example of tight oil accumulations in lacustrine sedimentary sequences previous studies have indicated that the main oil accumulation mechanism in this system is near source accumulation within upper and lower sweet spots i e reservoirs here we reveal the complexity of oil source and accumulation in this tight oil system is greater than previously thought a set of mudstones are developed between the upper and lower sweet spots of the lucaogou formation and are thus termed the middle section mudstones they have previously been little studied as few intervened reservoir rocks are developed within the sequences here we report their oil generation and contribution for the first time the mudstones are 97 182 m thick and have total organic carbon contents of 0 67 12 31 wt the kerogen is mainly type ii with small amounts of types i and iii and is in the mature stage these data suggest that the middle section mudstones have good hydrocarbon generation potential oil source correlations reveal a complex history of tight oil migration and accumulation the oils generated in the upper part of the middle section mudstones migrated northward to the basin margins and southeastward to the basin center in contrast oil generated in the lower part of the middle section mudstones migrated westward to the west central and central regions the oil migration resulted in complex tight oil accumulation which reflects the reservoir heterogeneity our data suggest that such reservoir heterogeneity appears to be typical of tight oil accumulations in continental lacustrine basins in the study area future evaluation exploration and exploitation of tight oil should also focus on the middle section mudstones and associated sweet spots in addition to the commonly acknowledged upper and lower sweet spots

ice core records as sea ice proxies an evaluation from the weddell sea region of antarctica 1 ice core records of methanesulfonic acid msa from three sites around the weddell sea are investigated for their potential as sea ice proxies it is found that the amount of msa reaching the ice core sites decreases following years of increased winter sea ice in the weddell sea opposite to the expected relationship if msa is to be used as a sea ice proxy it is also shown that this negative msa sea ice relationship cannot be explained by the influence that the extensive summer ice pack in the weddell sea has on msa production area and transport distance a historical record of sea ice from the northern weddell sea shows that the negative relationship between msa and winter sea ice exists over interannual 7 year period and multidecadal 20 year period timescales national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis data suggest that this negative relationship is most likely due to variations in the strength of cold offshore wind anomalies traveling across the weddell sea which act to synergistically increase sea ice extent sie while decreasing msa delivery to the ice core sites hence our findings show that in some locations atmospheric transport strength rather than sea ice conditions is the dominant factor that determines the msa signal preserved in near coastal ice cores a cautious approach is thus required in using ice core msa for reconstructing past sea ice conditions including the need for networks of ice core records and multiproxy studies to assess the significance of past msa changes at different locations around antarctica

resource potential and core area prediction of lacustrine tight oil the triassic yanchang formation in ordos basin china unlike liquid rich hydrocarbons in marine shale systems in north america the triassic yanchang oil is preserved in tight sandstone reservoirs deposited in a lacustrine setting the tight reservoir covers an area of 30 000 km2 11 600 mi2 and is characterized by ultralow permeability 0 001 1 00 md 0 001 10 3 1 00 10 3 m2 a low subsurface pressure coefficient 0 6 0 8 and low single well yield several tons 10 40 bbl to 10 tons 70 bbl per day the reservoir also features a high content of quartz feldspar and carbonate averaging 70 80 and low crude oil density of 0 84 g cm3 36 5 api with an oil saturation of approximately 60 80 for the first time this study employs the assessment of petroleum in place resources based on the genesis and statistics predicting method gspm and estimated ultimate recovery method for the tight oil in the ordos basin the advantage of gspm over previously reported methodologies is the suitable combination of genetic and statistical methods to estimate proximally sourced tight oil the results show that the total in place resource potential of the investigated tight oil is approximately 42 26 108 t 295 82 108 bbl with an average abundance of 15 104 t km2 99 104 bbl mi2 the recoverable resources for the 50 probability of the chang 7 tight oil accumulation is 3 11 108 t 21 77 108 bbl in the ordos basin the top two grades of the chang 7 tight oil core area cover the total area of three layers comprising 12 745 km2 4921 mi2 with 22 51 108 t 157 57 108 bbl of in situ resources furthermore the four most promising zones have been identified

characteristics and distribution of continental tight oil in china abstract tight oil in china is mainly distributed in mesozoic cenozoic continental petroliferous basins either generally occurs in tight sandstone or tight carbonate reservoirs which are paragenetic to or in contact with lacustrine petroleum source rocks by the end of 2016 the continental tight oil in china has established an annual production capacity of 1 55 million tons and a cumulative oil production of 2 52 million tons in 2016 the continental tight oil production in china was about 800 000 tons by analyzing the characterization of the tight oil in ordos basin songliao basin jungar basin the organic rich shale in china were formed in multiple geological periods including the permian triassic jurassic cretaceous neogene and paleogene in freshwater semi saline to hyper saline lacustrine depositional setting they are generally tens of meters to several hundreds of meters thick have total organic carbon toc contents of 0 4 16 and thermal maturity of 0 4 1 4 algal bloom as results of volcanism low sedimentation rate transgression and stratification of water body are prominent factors controlling the formation of organic rich shales tight oil reservoirs in china mainly include tight sandstone tight carbonate rock tight sedimentary tuff etc all of which are characterized by strong heterogeneity and poor petrophysical properties with in situ porosity and permeability generally no more 12 and 1 10 3 m2 respectively they are also characterized by tight pore throat systems of nano to micro scales with pore throat diameters in the range of 80 1800 nm and complex pore structures the producing reservoirs have pressure coefficients between 0 7 and 1 8 covering under pressure to over pressure crude oil properties vary greatly with densities ranging from 0 75 to 0 92 g cm3 it is believed that the abundance and effectiveness of hydrocarbon supply controls the formation of oil saturation and tight oil sweet spots are generally in or near the areas with high hydrocarbon expulsion intensities in addition the quality of the source rock and the type of source reservoir control the distribution of the sweet spots and storage space and movable fluid guarantee the formation of the sweet spot area of high oil saturation sweet spots are often developed in local mini structural highs under a broad and gentle sloped background continental tight oil in china has estimated geological resource of 14 66 109 tons with a technically recoverable resource of 1 45 109 tons tight oil is mainly distributed in ordos basin songliao basin bohai bay basin junggar basin and qaidam basin within the mesozoic and cenozoic formations overall china has a relatively large tight oil reserve and good exploration prospect

main factors controlling marine shale gas enrichment and high yield wells in south china a case study of the fuling shale gas field abstract the marine shale in south china is characterized by multiple layers a wide distribution and a large amount of resources however the characterization of the enrichment degree of marine shale gas and the main factors affecting the enrichment and high yield wells are still unclear which seriously affects the process of shale gas exploration and development in south china we integrated a large amount of drilling data core analysis data seismic data as well as gas testing results from fuling shale gas field to study the shale gas bearing properties the results suggest that any single parameter is insufficient to accurately characterize the gas bearing properties consequently we propose to integrate multiple parameters including total hydrocarbon values gas content gas saturation porosity pore diameters formation pressure coefficient and resistivity to comprehensively evaluate shale gas content and determine the origins of shale gas enrichment for the lower section of wufeng longmaxi formation in the fuling shale gas field we infer that the depositional environment and shale reservoir characteristic are the major factors affecting the stratigraphic variation of shale gas enrichment the differences of structural deformation and uplift and erosion in the later period are the main factors leading to differential enrichment in the lateral direction in factors affecting high yield well the completion parameters such as the lateral placement and lateral length of horizontal wells are the major factors affecting the test production

1000 year ice core records from berkner island antarctica two medium depth ice cores were retrieved from berkner island by a joint project between the alfred wegener institut and the british antarctic survey in the 1994 95 field season a151mdeep core from the northern dome reinwarthho he of berkner island spans 700 years while a 181m deep core from the southern dome thyssenho he spans approximately 1200 years both cores display clear seasonal cycles in electrical conductivity measurements allowing dating by annual layer counting and the calculation of accumulation profiles stable isotope measurements both d18o and dd together with the accumulation data allow us to estimate changes in climate for most of the past millennium the data show multi decadal variability around a generally stable long term mean in addition a full suite of major chemistry measurements is available to define the history of aerosol deposition at these sites again there is little evidence that the chemistry of the sites has changed over the past six centuries finally we suggest that the southern dome with an ice thickness of 950m is an ideal site from which to gain a climate history of the late stages of the last glacial and the deglaciation for comparison with the records from the deep antarctic ice cores and with other intermediate depth cores such as taylor dome and siple dome

resource assessment perspectives for unconventional gas systems concepts are described for assessing those unconventional gas sys tems that can also be defined as continuous accumulations contin uous gas accumulations exist more or less independently of the wa ter column and do not owe their existence directly to the buoyancy of gas in water they cannot be represented in terms of individual countable fields or pools delineated by downdip water contacts for these reasons traditional resource assessment methods based on es timating the sizes and numbers of undiscovered discrete fields can not be applied to continuous accumulations specialized assessment methods are required unconventional gas systems that are also continuous accumu lations include coalbed methane basin centered gas so called tight gas fractured shale and chalk gas and gas hydrates deep basin and bacterial gas systems may or may not be continuous accumu lations depending on their geologic setting two basic resource assessment approaches have been em ployed for continuous accumulations the first approach is based on estimates of gas in place a volumetric estimate of total gas in place is commonly coupled with an overall recovery factor to nar row the assessment scope from a treatment of gas volumes residing in sedimentary strata to a prediction of potential additions to re serves the second approach is based on the production perfor mance of continuous gas reservoirs as shown empirically by wells and reservoir simulation models in these methods production characteristics as opposed to gas in place are the foundation for forecasts of potential additions to reserves

twentieth century sea ice variability in the weddell sea and its effect on moisture transport evidence from a coastal east antarctic ice core record high resolution study of deuterium excess d excess sea salt sodium ss na and methane sulfonic acid msa in an ice core from coastal dronning maud land cdml east antarctica revealed the

reservoir characterization of an organic rich dolomitic tight oil reservoir the lower cretaceous xiagou formation in the qingxi sag jiuquan basin nw china abstract this study presents the reservoir characterization of the unconventional organic rich dolomitic tight oil reservoir of the lower cretaceous xiagou formation in the qingxi sag jiuquan basin to better describe pore characteristics and understand contributors to pore development of the mixed siliciclastic carbonate reservoirs samples were examined by thin section x ray diffraction xrd analysis total organic carbon toc and rock eval pyrolysis porosity and permeability measurement field emission scanning electron microscopy fesem and nuclear magnetic resonance nmr four types of laminations including carbonate lamination siliceous lamination argillaceous lamination and organic matter lamination are developed the average toc of 1 67 and calculated ro of 0 72 0 96 indicate that the xiagou source rocks are qualifed oil source various types of pores with different sizes and micro fractures are observed in such tight mixed siliciclastic carbonate reservoirs compared to mudstone shale and tight sandstone the tight and mixed siliciclastic carbonate reservoirs are characterized by 1 widely developed and multiple types of lamina structure 2 various pore types without secondary om pores generated by organic matter conversion 3 wide pore size distributions and 4 abundant and multiple genetic types of micro fractures the difference in mineral composition is the primary cause of different pore structure characteristics dolomitic mudstone is dominated by interlayer pore of clay mineral while argillaceous dolomite is characterized by interparticle fractures interparticle pores and micro fractures including shrinked micro fracture in dolomitic siltstone the residual intergranular pore and intergranular dissolved pore are the most common pores the nanopore occurs widely in all lithologies but the proportion of micrometers scale pores and macro scale nanopore increases from dolomitic mudstone to argillaceous dolomite and dolomitic siltstone the positive correlation between porosity permeability and toc indicate the existence of pores or micro fractures within or along the edge of organic matters the similar thermal maturity level ro 0 72 0 96 eliminates maturation as a variable in porosity development in the studying area the lithofacies associations with high quality source rocks and reservoirs relatively high porosity and permeability or rich in brittle minerals are the favorable targets

organic geochemistry of the woodford shale southeastern oklahoma how variable can shales be woodford shale samples obtained from a cored outcrop in southeastern oklahoma were geochemically analyzed to determine vertical variations of organic facies thermal maturity and an evaluation of their depositional environments total organic carbon values ranged from 5 01 to 14 81 indicating a good source rock potential in this area the woodford shale is marginally mature as indicated by vitrinite reflectance values rock eval data revealed that the samples are dominated by type ii kerogen biomarker ratios based on pristane phytane steranes and hopanes show a mix of marine and terrigenous organic matter high salinity conditions and water density stratification also prevailed during deposition of this formation as indicated by the presence of gammacerane the woodford shale was subdivided into lower middle and upper members based on the integration of geochemical and geologic data moreover the presence and extent of photic zone anoxia pza were determined by the presence of aryl isoprenoids the lower and upper woodford shale members were deposited under dysoxic to suboxic conditions and episodic periods of pza the middle member was deposited under anoxic conditions and persistent pza in addition aryl isoprenoids helped infer the position of the chemocline during deposition of the different members the relative hydrocarbon potential parameter was used in determining transgressive and regressive cycles within the woodford shale this study undoubtedly demonstrates the significant lithologic and chemical variability that occurs within shales the application of this workflow to regional studies can have a direct influence on exploration and production activities in shale gas systems

petroleum geology of the giant elm coulee field williston basin the elm coulee field of the williston basin is a giant oil discovery in the middle bakken formation devonian mississippian discovered in 2000 horizontal drilling began in the field in 2000 and to date more than 600 wells have been drilled the estimated ultimate recovery for the field is more than 200 million bbl of oil 31 8 million m3 the bakken formation in the field area consists of three members 1 upper shale 2 middle silty dolostone and 3 lower siltstone the total bakken interval ranges in thickness from 10 to 50 ft 3 1 to 15 3 m over the field area the upper shale is dark gray to black hard siliceous slightly calcareous pyritic and fissile the shale consists of dark organic kerogen minor clay silt size quartz and some calcite and dolomite the kerogen consists mainly of amorphous material and the organic material is distributed evenly throughout the shale interval not concentrated in laminations or lenses the upper shale ranges in thickness from 6 to 10 ft 1 8 to 3 1 m over the field area the middle member consists of a silty dolostone and ranges in thickness from 10 to 40 ft 3 1 to 12 2 m the lower member in the elm coulee field consists of brownish gray argillaceous organic rich siltstone burrowing and brachiopod fragments are common in the lower member this facies is equivalent to the lower bakken black shale facies on the northern side of the field and is interpreted to be an updip landward equivalent to the deeper water black shale facies the lower member ranges in thickness from 2 to 6 ft 0 61 to 1 8 m based on the abundance of fossil content and amount of burrowing the members of the bakken formation are interpreted to have been deposited under aerobic middle member common burrows and rare fossils dsyaerobic lower member common fossils and lesser amount of burrows and anaerobic conditions upper member rare fossils and burrows the main reservoir in elm coulee field is the middle member which has low matrix porosity and permeability and is found at depths of 8500 to 10 500 ft 2593 to 3203 m the current field limits cover approximately 450 mi2 1165 km2 the middle bakken porosities range from 3 to 9 and permeabilities average 0 04 md overall the reservoir quality in the middle bakken improves upward as the amount of clay matrix decreases the middle bakken is interpreted to be a dolomitized carbonate shoal deposit based on subsurface mapping and dolomite lithology the main production is interpreted to come from matrix permeability in the field area occasional vertical and horizontal fractures are noted in cores the vertical pay ranges in thickness from 8 to 14 ft 2 4 to 4 3 m the bakken is slightly overpressured with a pressure gradient of 0 53 psi ft 0 02 kpa m horizontal wells are drilled on 640 to 1280 ac 259 to 518 4 ha spacing units long single laterals dual laterals and trilaterals have all been drilled in the field the horizontal intervals are sand gel and water fracture stimulated initial production ranges from 200 to 1900 bopd 31 8 to 302 1 m3 day initial potential rates for vertical wells are generally less than 100 bopd 15 9 m3 day the upper bakken shale probably also contributes to the overall production in the field the exact contribution is unknown but estimated to be less than 20 of the total production the elm coulee field illustrates that the bakken petroleum system has enormous potential for future oil discoveries in the williston basin

controlling factors on the formation and distribution of sweet spot areas of marine gas shales in south china and a preliminary discussion on unconventional petroleum sedimentology abstract shale gas resources in china are abundant with the marine shales accounting for the largest proportion i e 13 1012 m3 the wufeng longmaxi shale system deposited across the late ordovician and early silurian transition in south china is currently the target for shale gas exploration and development in china its annual output in 2018 reached 10 8 109 m3 making china the largest shale gas production region outside north america within this shale system the sweet spot intervals of shale gas formed vertically and sweet spot areas of shale gas formed regionally the sweet spot intervals occur mainly at the bottom of the wufeng longmaxi shale and are 10 40 m in thickness the sweet spot interval is characterized by high total organic carbon toc and gas contents relatively high porosity high brittle mineral content and abundant lamination fissures and fractures the formation of shale gas sweet spot intervals is mainly controlled by four factors in south china they are anoxic shelf environment abundant nano pores in organic matter sealed roof and floor strata and abundant lamination and high silica content in shale respectively as the regional extension of the sweet spot intervals the formation of the sweet spot area requires all the controlling factors for the sweet spot interval it was born in regional anoxic shelf with stable tectonics and preserved in relatively stable tectonic zones three sweet spot areas are identified for the wufeng longmaxi shale in south china i e fuling weiyuan fushun yongchuan and changning zhaotong areas the total area is about 2 104 km2 with technically recoverable resources of 3 3 1012 m3 in addition with the rapid progresses of exploration and development of unconventional petroleum resources such as shale gas the petroleum industry around the world extends to unconventional petroleum resources gradually accomplishing an important change of petroleum geology research focus from conventional to unconventional unconventional petroleum geology research focuses on continuously or semi continuously distributed sweet spot areas for which the formation would be the result of coupling sedimentology from several geological events such as global or regional tectonic activity volcanic eruption climate change anoxic water biotic mass extinction and radiation and gravity current it is necessary to innovatively construct new insights of unconventional petroleum sedimentology in order to enrich and improve the petroleum sedimentology research and its application therefore the concept of unconventional petroleum sedimentology is proposed and its research task method aim and importance are preliminarily discussed

the upper paleozoic coalbed methane system in the qinshui basin china the coalbed methane resource is very abundant in qinshui basin 3 28 1012 m3 114 tcf the investigation on the upper paleozoic coalbed methane system is a guide to the exploration and development of coalbed methane the upper paleozoic coalbed methane system in the qinshui basin is sealed by a low permeability roof and floor strata comprising mudstone siltstone and bauxite of the carboniferous benxi formation and the permian shanxi and xiashihezi formations the overburden is the lower permian xiashihezi formation and the upper permian triassic and middle jurassic clastic deposits the source and reservoir rocks are the carboniferous permian coal seams the hydrocarbon generation of the source rocks reached its first peak in the late triassic the highest maturity was about ro 1 2 under a normal paleogeothermal gradient 2 3c 100 m 1 1 1 7f 100 ft a tectonic thermal event during the jurassic and cretaceous yanshanian orogeny enhanced the coal maturity and caused a second peak of hydrocarbon generation varying igneous intrusions caused the coal maturity to be higher in the southern northern and eastern parts of the qinshui basin instead of the central and western parts the highest maturity was greater than ro 4 in the jincheng area the migrated thermogenetic coalbed methane accumulated in the reservoirs in which abnormally high reservoir pressure exists locally under the hydrodynamic drive because of the different hydrodynamic background and sealing condition the distribution of coalbed methane content is inhomogeneous the reservoir is undersaturated with gas in most areas based on the coalbed methane system investigation we assessed the coalbed methane producibility in different parts of the qinshui basin and the major producibility area is in the southern part of the basin

assessment on tight oil resources in major basins in china abstract large scale commercial development of shale gas and tight oil resources in north american and continuous discoveries of tight oil in china lead to the recognition of the importance of assessment on tight oil resources based on the characteristics of china s tight oil reservoirs and exploration status this paper discusses a workflow focusing on in place resource evaluation in the workflow a resource richness analogy approach rr aa is proposed for assessment of tight oil resources in less explored areas a genesis statistics assessment approach gs aa for lacustrine tight oil resources with strong heterogeneity and regions where more delicate assessment is required and an eur analogy approach eur aa for assessment on recoverable tight oil by fully using available eur data of production wells after analyzing the geological characteristics of the formation of tight oil in the ordos bohai bay songliao junggar sichuan and other major basins the distributions of essential parameters such as reservoir thickness area and porosity have been defined and the parameter evaluation criteria have been established finally the tight oil resource potentials in the major basins in china have been evaluated using one of the three methods and the prospective areas of high resource abundance are outlined in each of basins the results from this study show that china s tight oil resources have a large potential and good exploration future the estimated in place tight oil resources are 12 580 109 tons mainly distributed in the ordos songliao bohai bay and junggar basins 15 most favorable zones are proposed having in place resources of 5 296 109 tons

a basin modeling and organic geochemistry study in the vallecitos syncline san joaquin basin california abstract the vallecitos syncline is a westerly structural extension of the san joaquin basin the vallecitos oil field comprised of eight separate areas that produce from cretaceous and paleogene reservoirs accounted for 5 4 mmb of oil and 5 6 bcf associated of gas through 2010 however exploration for oil and gas in the vallecitos area is challenging due to structural complexity and limited data the purpose of this study is to evaluate whether source rocks are actively generating petroleum in the vallecitos syncline and to improve our understanding of burial history and timing of hydrocarbon generation we conducted biomarker analysis on twenty two oil samples from the vallecitos syncline source related biomarkers show two genetic groups of oil which originated from two different source rocks these results differ from earlier published interpretations in which the kreyenhagen formation is the only source rock in the vallecitos syncline and suggest that the cretaceous moreno formation in the syncline also is an active source rock stratigraphic evidence and modeling suggest that late cenozoic episodes of erosion due to folding and uplift removed significant overburden on the flanks of the syncline to better understand the petroleum systems and clarify the total active source rocks in the area 2d burial histories were generated through the vallecitos syncline a published cross section through the deepest part of the syncline was selected to conduct thermal history basin evolution and migration analyses the 2d model results indicate that the lower kreyenhagen formation has various maturities within the formation at different locations in the present day syncline the basal part of the kreyenhagen formation is in the dry gas window and maturity decreases away from the central part to the flanks it remains immature along shallow portions of the present day flanks in contrast the basal part of the moreno formation achieved extremely high maturity past the gas generation zone but is in the oil generation zone on the flanks of the syncline at shallow depth all of our geochemical and 2d model results suggest that there are two active source rocks in the vallecitos syncline accordingly we propose that there are two active petroleum systems in the vallecitos syncline

geochemical characteristics of crude oil from a tight oil reservoir in the lucaogou formation jimusar sag junggar basin jimusar sag which lies in the junggar basin is an important tight oil study area in china however the properties and origin of the crude oil and the geochemical characteristics of the tight oil from the lucaogou formation have not yet been studied in the present study 23 crude oil samples from the lucaogou formation were collected for analysis including physical properties density and viscosity bulk composition saturated hydrocarbon gas chromatography mass spectrometry and calculation of various biomarker parameters source rock evaluation and porosity permeability analysis were applied to the mudstones and siltstones to analyze the hydrocarbon generation history of the lucaogou source rocks one dimensional basin modeling was performed the oil filling history was also investigated by means of basin modeling and microthermometry biomarkers of suitable source rocks total organic carbon content is 1 summation of the free and volatile hydrocarbon and remaining hydrocarbon generative potential is 6 mg hc g rock and vitrinite reflectance is between 0 7 and 1 were analyzed for oil source correlation the results indicate that low maturity to mature crude oils originated from the source rocks containing terrigenous organic matter which were deposited in a saline lake the source rocks are of mainly type ii kerogen oil in the lower section of the lucaogou formation is relatively dense and viscous and has elevated nonhydrocarbon content in addition a higher proportion of bacteria and algae is shown to have contributed to the formation of crude oil in the lower section when compared with the upper section of the lucaogou formation oil source correlations demonstrate that not all mudstones within the lucaogou formation contribute to oil accumulation thin section observation indicates organic macerals surround the grains of some siltstones within the porous and permeable subsections which proves the siltstones contribute to hydrocarbon generation crude oils from the upper and lower sections mainly originate from thin bedded mudstones interbedded and siltstones within the porous and permeable subsections the mudstones over or beneath the porous and permeable subsections consist of seals and prevent the vertical movement of oil by capillary forces despite being thicker mudstones between the two porous and permeable subsections make no obvious contribution to the oil accumulation because of their low permeability and distance from the porous and permeable subsections which is consistent with the principle of near source charging for tight oil accumulations lucaogou oil has been charged twice once from 235 to 210 ma and again from 180 to 150 ma coinciding with oil generation time

pore type and pore size distribution of tight reservoirs in the permian lucaogou formation of the jimsar sag junggar basin nw china abstract the tight reservoir of the lucaogou formation in the jimsar sag located in the southeastern junggar basin northwest china has been investigated for its great potential tight oil resources in this study petrography and mineralogy pore microstructures and pore size distributions of the samples collected from nine wells were analyzed using x ray diffraction xrd total organic carbon toc thin sections and scanning electron microscopy sem the major rock types were identified as dolomite and siltstone which had different pore type assemblages and various pore size distribution patterns based on the pore origin pores were identified as primary mineral pores dissolved mineral pores primary organic matter pores and secondary organic matter pores their sizes followed a power law distribution regardless of lithological variability or sem magnification however the power law exponent d was associated with lithology and diagenesis as well as hydrocarbon generation in dolomite the decrease in dolomite content and the increase in dolomite particle size were commonly in accordance with the decrease in the power law exponent d compaction and cementation were the principal diagenetic processes that had a crucial effect on the pore size distribution with a large d equal to 2 77 in siltstone the influence of various pore types on the pore size distribution was controlled by diagenesis in which case dissolution and cementation were compensating for their influence with a fluctuating power law exponent d ranging from 1 5 to 2 7

reservoir characterization of a tight oil reservoir the middle jurassic upper shaunavon member in the whitemud and eastbrook pools sw saskatchewan abstract new horizontal drilling and multi stage fracture completion technology have proven successful in unlocking hydrocarbons from previously uneconomic reservoirs in this paper we investigate the application of this new technology to a medium gravity oil sandstone reservoir to enhance the poor oil recovery within the pool but also to evaluate if the pool boundaries can be expanded petrophysical well logs were integrated with detailed core descriptions thin sections and core analysis data to provide insight to the reservoir characteristics and factors controlling production reservoir distribution depositional environments and lateral extent of depositional fairways for the reservoirs the middle jurassic upper shaunavon b sandstone is the main reservoir in the studied whitemud and eastbrook pools in southwest saskatchewan the reservoirs are composed of mixed siliciclastic carbonate shallow marine shoreface deposits which have a strike trend northeast southwest although the pools were discovered in 1953 and 1966 and have cumulative production of 3 3 mmbbls of medium gravity 22 api oil estimated oil recovery is less than 4 the upper shaunavon b sandstone has two main reservoir facies shoreface sandstones with permeabilities in the 0 1 10 md range and relatively thin but high permeability 10 1000 md coquina beds until recently wells targeted mainly the high permeability coquina for its higher production rates and as a means to drain the associated thick lower permeability shoreface sandstone reservoir this study evaluates the upper shaunavon b shoreface sandstone reservoir quality by examining the reservoir properties heterogeneity connectivity and pore volume of the flow units based on core and petrophysical data comparison of production data from wells intersecting both facies of the upper shaunavon b versus wells where the underlying high permeability coquina facies is absent allows a perspective on the impact that the coquina has on the recovery factor in both reservoir types integration of petrophysical well logs detailed core descriptions thin sections and core analysis data provide insight to the facies interpretation reservoir distribution and lateral extent of depositional fairways for both units reservoir characterization of the lower permeability siliciclastic facies at the whitemud and eastbrook pools coupled with recent advances in horizontal drilling and completion technology show that additional drilling opportunities exist within the pools to improve oil recovery but also that oil saturated sandstone reservoirs exist outside the boundaries of the pools recent successes with multi stage fracturing of horizontal wells have confirmed the findings of this study

evaluation of eocene source rock for potential shale oil and gas generation in north cambay basin india abstract source rock potential of 108 representative samples from 3 m intervals over a 324 m thick shale section of middle eocene age from the north cambay basin india have been studied variation in total organic carbon toc and its relationship with loss on ignition loi have been used for initial screening screened samples were subjected to rock eval pyrolysis and organic petrography a toc log indicated wide variation with streaks of elevated toc a 30 m thick organic rich interval starting at 1954 m depth displayed properties consistent with a possible shale oil or gas reservoir toc wt values of the selected samples were found to vary from 0 68 to 3 62 with an average value of 2 2 the modified van krevelen diagram as well as hi vs t max plot indicate prevalence of type ii to type iii kerogen t max measurements ranged from 425 c to 439 c indicating immature to early mature stage which was confirmed by the mean vitrinite reflectance values r o of 0 63 0 65 and 0 67 at 1988 m 1954 m and 1963 m respectively quantification of hydrocarbon generation migration and retention characteristics of the 30 m source rock interval suggests 85 expulsion of hydrocarbon oil in place oip resource of the 30 m source rock was estimated to be 3 23 mmbbls per 640 acres the oil saturation index osi crossover log showed from a geochemical perspective moderate risk for producing the estimated reserve along with well location for tapping the identified resource

analysis of a 3 year meteorological record from the ablation zone of morteratschgletscher switzerland energy and mass balance since 1 october 1995 an automatic weather station has been operated on the tongue of morteratschgletscher switzerland the station stands freely on the ice and sinks with the melting glacier surface it is located at 2100 m a s l and measures air temperature wind speed and direction incoming and reflected solar radiation pressure and snow temperature a sonic ranger mounted to stakes drilled into the ice measures surface height from which melt rates and snow accumulation can be derived in this paper the data for the period 1 october 1995 to 30 september 1998 are used to evaluate the surface energy balance the turbulent energy fluxes are calculated with the bulk method the turbulent exchange coefficient c h is used as a control parameter with c h 0 00127 the calculated melt equals the observed melt which is 17 70 m w e over the 3 years when averaged over the time when melting occurs i e 35 of the time the mean surface heat flux equals 191 w m 2 net shortwave radiation contributes 177 w m 2 net longwave radiation 25 w m 2 the sensible heat flux 31 w m 2 and the latent heat flux 8 w m 2

a benchmark dataset of in situ antarctic surface melt rates and energy balance abstract surface melt on the coastal antarctic ice sheet ais determines the viability of its ice shelves and the stability of the grounded ice sheet but very few in situ melt rate estimates exist to date here we present a benchmark dataset of in situ surface melt rates and energy balance from nine sites in the eastern antarctic peninsula ap and coastal dronning maud land dml east antarctica seven of which are located on ais ice shelves meteorological time series from eight automatic and one staffed weather station neumayer ranging in length from 15 months to almost 24 years serve as input for an energy balance model to obtain consistent surface melt rates and energy balance results we find that surface melt rates exhibit large temporal spatial and process variability intermittent summer melt in coastal dml is primarily driven by absorption of shortwave radiation while non summer melt events in the eastern ap occur during fohn events that force a large downward directed turbulent flux of sensible heat we use the in situ surface melt rate dataset to evaluate melt rates from the regional atmospheric climate model racmo2 and validate a melt product from the quikscat satellite