oceanographic dynamics and the end of the last interglacial in the subpolar north atlantic the last interglacial interval was terminated by the inception of a long progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth however the feedbacks internal dynamics and global teleconnections associated with declining northern summer insolation remain incompletely understood here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre spg circulation of the north atlantic ocean detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from ocean drilling program site 984 south of iceland reveal repeated progressive cold water mass expansions into subpolar latitudes during the last peak interglacial interval marine isotope substage 5e these movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern arctic front and associated with rapid changes in the strength of the spg this persistent millennial scale oceanographic oscillation accompanied a long term cooling trend at a time of slowly declining northern summer insolation providing an early link in the propagation of those insolation changes globally and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent 100 ka

accessibility and mobility of hydrocarbons in lacustrine shale solvent flow through extraction experiments on eocene oil shales from bohai bay basin eastern china abstract in order to examine the mobility of hydrocarbons in a lacustrine shale oil system three cylindrical core plugs from the eocene shahejie formation lacustrine shale oil system in the jiyang depression were sequentially extracted with dichloromethane dcm in flow through experiments under controlled stress conditions in a tri axial flow cell orientations of the three sample plugs were perpendicular to bedding 1 and parallel to bedding 2 and 3 post experiment micro ct analysis confirmed three different flow patterns cross bedding flow 1 minor bedding parallel flow 2 and extensive bedding parallel flow along open fractures 3 extraction times were 28 days 7 days and 3 days for samples 1 2 and 3 respectively sequential series of extracts from the samples were analyzed using gas chromatography for comparison hydrocarbon compositions were also determined on bulk extracts of powdered original sister sample material and the residues after flow through experiments the mobilities of hydrocarbons are controlled by the flow direction and fracture intensity and orientations for sample 1 dcm flow through extraction yielded mostly hydrocarbons associated with matrix kerogen this flow extracted bitumen was found to be much heavier than that extracted from the other two samples and to have a lower mobility the hydrocarbons extracted from the sample 2 were the lightest for sample 3 containing micro fractures along the bedding planes the extraction process was apparently very effective not only dissolving hc from the fractures but also some hc from the kerogen the characteristic hydrocarbon compositions of the samples were essentially retained in all extracts although lighter hydrocarbons

pore network characteristics of lacustrine shales in the dongpu depression bohai bay basin china with implications for oil retention abstract pore development and the location of retained hydrocarbons are key topics to understand the shale oil system in an attempt to investigate pore network characteristics and oil retention in lacustrine shales 24 samples from the es3 shales in the dongpu depression bohai bay basin were subjected to mineralogical petrological geochemistry and pore structure investigations using x ray diffraction xrd thin section field emission scanning electronic microscope fe sem n2 adsorption desorption after removing retained oil by solvent extraction 12 selected samples were again analyzed by rock eval pyrolysis and n2 adsorption desorption experiment according to the mineral compositions and petrological characteristics six types of lithofacies are identified in the es3 shales in the dongpu depression laminated calcareous shales lenticular calcareous shales laminated argillaceous shales massive argillaceous shales laminated siliceous shales and massive siliceous shales geochemical characteristics of these shales are quite different as calcareous laminated shales have higher toc contents than massive argillaceous and siliceous shales interparticle pores intraparticle pores organic matter pores and fracture pores are observed in the studied samples while bitumens were found retaining in well connected pore network the n2 adsorption desorption experiments on samples before and after solvent extraction reveal the different pore structure characteristics in six lithofacies and the occurrence of oil in lacustrine shales in general pore volumes within pore diameter range of 1 7 10nm and 10 200nm of samples show increase after solvent extraction indicating that large and small pores in shales both play important roles in oil retention oil retained in shales can be divided as free and heavy fractions as from the pyrolysis results in lacustrine shales larger pores are main storage space for hydrocarbon larger pores in different lithologies have similar capacity for free oil retention while those in calcareous and argillaceous shales are more efficient for heavy oil retention for both free and heavy oil small pores in argillaceous shales are efficient for their storage

petroleum generation and charge history of the northern dongying depression bohai bay basin china insight from integrated fluid inclusion analysis and basin modelling abstract the petroleum generation and charge history of the northern dongying depression bohai bay basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling one and two dimensional basin modelling was performed to unravel the oil generation history of the eocene shahejie formation es3 and es4 source rocks based on the reconstruction of the burial thermal and maturity history calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the es4 source rocks began to generate oil at around 35 ma reached a maturity level of 0 7 ro at 31 30 ma and a peak hydrocarbon generation at 24 23 ma the lower interval of the es3 source rocks began to generate oil at around 33 32 ma and reached a maturity of 0 7 ro at about 27 26 ma oil generation from the lower es3 and upper es4 source rocks occurred in three phases with the first phase from approximately 30 20 ma the second phase from approximately 20 5 ma and the third phase from 5 ma to the present day the first and third phases were the two predominant phases of intense oil generation samples from the es3 and es4 reservoir intervals in 12 wells at depth intervals between 2677 7 m and 4323 0 m were investigated using an integrated fluid inclusion workflow including petrography fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern dongying depression abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography fluorescence spectroscopy and microthermometry data two episodes of oil charge were determined at 24 20 ma and 4 3 ma respectively with the second episode being the predominant period for the oil accumulation in the northern dongying depression the oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence the expelled oil was then charged to the already established traps in the northern dongying depression the proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation migration and accumulation

shallow erosion beneath turbidity currents and its impact on the architectural development of turbidite sheet systems erosion by turbidity currents changes the morphology of the sea floor the relief of the scoured surface may affect the dynamics of the flow and thereby the pattern of deposition this could in turn affect flow and deposition patterns in subsequent events this study investigates shallow centimetre to decimetre scale erosion beneath turbidite sheet sandstones of the oligocene macigno formation of north west italy where erosion and deposition are variably coupled at the bed scale in a net aggradational setting the research focus was on i the recognition of scour edges and erosive surfaces ii quantification of spatial differences in the amount of erosion and iii an investigation of how this differential erosion can be compensated by the deposits directly overlying the erosional surfaces where they can be observed scour edges commonly have sills of the overlying sandstone intruding beneath blocks and wings of the substrate that is being eroded a consequence of this de laminating scouring style is that erosional surfaces are bedding parallel when followed away from the scour edges giving the appearance of normal conformable bed bases despite their cryptic nature such bedding parallel scour surfaces can be recognized by comparing serial detailed sedimentary logs here 16 bed parallel scour surfaces were identified in a succession comprising 95 beds different styles of compensation by the overlying turbidite beds are defined based on differential sedimentation inside and outside of the scour relief it is found that differential erosion is on average under compensated by differential sedimentation in some cases the overlying deposits anti compensate being thinner at the location where more erosion has occurred unequal spatial distribution of differential erosion in the study area combines with sedimentary under compensation to result in a trend of accumulating section thickness differences over multiple beds in one ca 25 m thick package the maximum cumulative change in lateral gradient during some 20 events reached 0 17 before being reset by a single event this process can be interpreted either as a lobe compensation effect or as a scour enhancement effect depending on the orientation of the palaeohorizontal datum if allowed to proceed the latter process could force the system past a channellization threshold prompting a change from sheet to channelled architecture this type of shallow substrate scouring and differential deposition is likely to be an important process in the build up of sheet turbidite sandstone units and could play a major role in autocyclic adjustment of local sea floor gradients

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 1 source rock characterization detailed mapping of the tertiary strata of the dongying depression bohai bay basin reveals that oil shales and dark mudstones in the es4 and es3 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in the niuzhuang sag whereas source rocks along the niuzhuang south slope are currently immature or marginally mature for the generation of conventional oils this study examined the molecular characteristics for a number of biomarker compound classes and related these to either source facies change or different burial and thermal maturation an important observation made during this study is the significant variation in the relative distributions and absolute concentrations of a wide range of aliphatic and aromatic hydrocarbon markers in the rock extracts as a function of burial depth this variation may potentially explain the uncertainty associated with the maturity assessment and genetic modeling for so called immature oils that are usually defined on the basis of alkane biomarker isomerization ratios and the presence of biomarkers with biological configurations

formation of bedding parallel fibrous calcite veins in laminated source rocks of the eocene dongying depression a growth model based on petrographic observations abstract bedding parallel fibrous calcite veins commonly referred to as beefs are widely developed within eocene lacustrine laminated organic rich source rocks in the dongying depression of bohai bay basin east china understanding the formation of this type vein is essential to elucidate the diagenetic evolution and fluid migration in muddy source rocks this study investigates the mechanism s of growth of bedding parallel veins in hydrocarbon source rocks of the es4 upper and the es3 lower units in the dongying depression based on systematic observations of macro and micro scale features both in veins and their wall rocks combined with x ray diffraction and analyses of geochemical indicators the source rocks are heterogeneous in both composition and structure the beefs mainly occur in laminated rocks consisting of organic rich laminae which occur together with horizontally continuous banded lamalginites and rare carbonate rich laminae overall corresponding to high toc low carbonate contents and low maturity average ro 0 57 most beefs are embedded in the neighboring lamalginites of organic rich laminae with low clay mineral contents the beefs are products of diagenesis accompanying burial and both the initial fracture opening and subsequent dilation represent early stages of hydrocarbon generation and expulsion the presence of bedding parallel bituminite veins and the median plane or parting is evidence for horizontally oriented hydrofracturing due to fluid overpressure in turn fluid overpressure reflects the generation and primary migration of hydrocarbon bearing fluids hydrocarbon generation organic matter evolution and clay mineral dehydration illitization of smectite were responsible for the fluid overpressure crystal growth within the beefs was a continuous process with an antitaxial growth direction and there was no growth competition between adjacent fibres these observations indicate that the crystal growth and fracture dilation were synchronous and growth space was limited the force exerted by crystallizing vein fill contributed to the high fluid pressure suggesting that fibrous vein minerals actively promoted further dilation as the veins grew vein dilation accompanied the migration of hydrocarbon bearing fluids evinced by the occurrence of primary hydrocarbon inclusions found in the fibrous calcites therefore the hydrocarbon bearing fluids were present at the time of horizontal fluid flow from the start of fracture opening to the end of the dilation

how to find high quality petroleum source rocks in saline lacustrine basins a case study from the cenozoic qaidam basin nw china abstract despite having made significant contributions to global hydrocarbon occurrences source rocks in saline lacustrine basins show great mineralogical and organic geochemical heterogeneity and the controlling mechanism is weakly studied here we use the cenozoic qaidam basin as an example to compare the organic and inorganic parameters of fine grained sediments in different lacustrine facies and to figure out the characterization and distribution of effective petroleum source rocks in saline lacustrine systems organic inorganic database of six selected boreholes show that in the bench margin high gradient lacustrine system fine grained sediments in sublittoral brackish mesosaline zones containing low chlorides

adsorbed and free hydrocarbons in unconventional shale reservoir a new insight from nmr t1 t2 maps abstract characterizing free and adsorbed hydrocarbon is crucial for the resources assessment and mobility evaluation of shale oil plays the complex feature of hydrogen bearing components in shale reservoirs requires new analytical methods to study the occurrences of different states of hydrocarbons in this study forty core samples from five shale oil research wells in the jiyang depression of china were analyzed using various analytical tools including nuclear magnetic resonance nmr t1 t2 mapping leco total organic carbon toc analysis routine and special programmed rock eval pyrolysis solvent extraction and fractionation as well as mercury injection capillary pressure micp experiments additional experiments were conducted on a powdered shale for nmr t1 t2 maps under four states as received after being dried at 110 c after special programmed pyrolysis to 350 c and after solvent extraction the results showed that residual water signals in the nmr t1 t2 map disappeared after being dried at 110 c free oil signals decreased dramatically when the sample was thermally treated to 350 c while adsorbed oil signals decreased sharply after solvent extraction a good accordance was observed between the organic hydrogen t2 spectra and three modes of rock eval pyrograms representing free hydrocarbons adsorbed hydrocarbons and hydrocarbons from kerogen bitumen decomposition a positive correlation was also found between the intensity of nmr t1 t2 map signals and the free and adsorbed hydrocarbon contents from geochemical analysis t2 cut off values of adsorbed hydrocarbons and free hydrocarbons were determined to be 0 2 ms and 1 ms respectively core samples with a high oil saturation index porosity and relative content of hydrocarbons display a low t1 t2 ratio indicative of a high shale oil mobility as a complementary method to the rock eval analysis nmr t1 t2 mapping is a non destructive technique for the characterization of adsorbed and free hydrocarbons at the core scale with limited sample preparation the results of this study are helpful for nmr characterization of shale reservoirs

polyphase thermal evolution in the infra cambrian ara group south oman salt basin as deduced by maturity of solid reservoir bitumen petrographic and organic geochemical analyses on solid reservoir bitumen from the late precambrian to early cambrian ara group indicate polyphase thermal evolution in the south oman salt basin sosb the ara group constitutes a complex petroleum system in the deep subsurface 3 5 km of interior oman salt diapirs encase isolated partly highly overpressured carbonate bodies intra salt stringers which represent a predominantly self charging hydrocarbon system a large number of stringer cores show that reservoir quality is decreased by the presence of solid reservoir bitumen by using different microscopy techniques this solid reservoir bitumen has been identified within pores pore throats and microfractures of the carbonates solid bitumen reflectance measurements brr were converted to vitrinite reflectance vrr using a new improved calibration vitrinite reflectance geothermometry shows that maximum paleo temperatures have a highly heterogeneous distribution paleo temperatures of 380 c were obtained from coke like solid reservoir bitumen which most likely formed from thermal cracking of oil in our model this process is related to hydrothermal fluids deriving from deeper pre salt strata of the sosb which entered the intra salt carbonate stringers during times of basement tectonic activity via hydrofractures this caused the formation of high maturities pyrobitumens in close vicinity to the fractures and precipitation of migrabitumens with increasing distance to the ht source which is supported by the geochemical composition of the solid reservoir bitumens the influx of these fluids into the carbonate stringers is considered to represent a major contribution to their strong overpressures 2007 elsevier ltd all rights reserved

organic fades in recent sediments of carbonate platforms southwestern puerto rico and northern belize abstract our organic facies model of a platform environment is based on the analysis of 1 total organic carbon 2 visual protokerogen types and hydrogen indices of the sediments 3 sediment mineralogy and grain size and 4 reef patterns water circulation and relief of the adjacent land toc values are lowest on reefs and outer platforms 0 2 intermediate in sediments fringing carbonate islands 0 5 2 0 on sea grass meadows 0 5 0 7 and in forereef lagoons 0 1 0 7 highest in inner platform lagoons 0 5 5 0 and mangrove swamps 2 7 3 5 paniculate organic matter comprises structured terrestrial marine and amorphous types on average terrestrial material accounts for 28 of om in puerto rico and 12 in belize the mean hydrogen index of the sediment is 355 mg hydrocarbons g toc in puerto rico and 719 in belize this study indicates that toc values are mainly related to platform subenvironment while om types are controlled by distance from the shoreline organic facies dominated by structural terrestrial om occur closer to the shore whereas toward the shelf margin marine and amorphous om contents increase

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

sedimentary environmental controls on petrology and organic matter accumulation in the upper fourth member of the shahejie formation paleogene dongying depression bohai bay basin china abstract the upper fourth member of the eocene shahejie formation es4s is a typical example of a bohai bay basin lacustrine shale these sedimentary units are characterized by markedly different mineral compositions compared to marine siliciclastic shales thus understanding the characteristics and sedimentary environment of lacustrine shales enables analysis of their origin enrichment of organic matter om distribution of organic rich shales and exploration targets for shale oil and gas based on thin sections and field emission scanning electron microscope observations from well core samples combined with x ray diffraction and geochemistry the mineralogy lithofacies organic and geochemical characteristics as well as the sedimentary environment of the es4s shale are analyzed in this paper the results show that across the study area the es4s shale is mainly composed of calcite clay minerals and quartz but also contains subordinate dolomite feldspar pyrite and anhydrite on the basis of mineral composition total organic carbon toc content and sedimentary structures eight lithofacies are identified the toc content of samples ranges between 0 15 and 11 4 with an average of 2 27 while om primarily consists of type i kerogen based on paleoclimate and paleosalinity data as well as redox conditions and primary productivity the sedimentary environment of the es4s shale can be further divided into four intervals intervals i ii iii and iv and these four intervals have large differences rather than persistently warm damp climate and reducing condition the evolution of these intervals is also analyzed in detail in this study and the controls on lithofacies and om accumulation are also discussed the results of this study suggest that the development of mineral compositions and frequent vertical lithofacies associations are strongly controlled by the cyclic evolution of the sedimentary environment thus the accumulation of om occurs as the result of a number of inter connected factors including primary productivity terrestrial inputs and variation in oxidizing reducing conditions across a given interval these factors can either work together or one can play a leading role

organic matter maturation under the influence of a deep intrusive heat source a natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock toarcian shale northern germany four shallow boreholes were drilled in the hils syncline northern germany in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen type ii bearing source rock the holes penetrated the carbonceous lias shales posidonia shale lower toarcian and part of the adjacent dogger and lias mudstones the maturity of the organic matter in the cores recovered ranges from immature 0 48 r0 to overmature 1 45 r0 due to location of the hils syncline in the vicinity of the vlotho massif which is deep seated intrusive body facies variations of the lias within the short geographical distances in the study area are negligible organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the lias shales kerogen bitumen etc and on the evidence of a uniform initial composition of these sediments in the study area dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations about 50 of the initial kerogen was transformed into oil gas and inorganic compounds during the vitrinite reflectance increase from 0 48 to 0 88 ro and only marginally more during the maturity increase from 0 88 to 1 45 ro only a small portion of the generated material remained in the source rock even at a relatively early stage of generation 0 68 ro expulsion efficiency of oil plus gas reached a value of 86 at the end of the main generation stage 0 88 ro

identification of sequence stratigraphy in the dongying formation of the liaoxi low uplift bohai bay basin china a change in sea level or lake level causes a change in accommodation space and sediment compensation which then controls the formation and evolution of sequences a multidisciplinary approach ba

fractures of lacustrine shale reservoirs the zhanhua depression in the bohai bay basin eastern china abstract fractures play a vital role in the exploration and development of shale oil and gas by providing effective space for shale reservoirs and significantly improving the fluid flow capability core observations microscopic analyses of thin sections scanning electron microscopy and formation microscanner imaging fmi were used to determine the types causes of formation and development characteristics of the fractures in lacustrine shale reservoirs in the lower part of the paleogene shahejie formation es 3 in the zhanhua depression bohai bay basin eastern china x ray diffraction xrd analysis total organic carbon toc measurements and porosity and permeability measurements were used to study the controlling factors of the fractures in the shale reservoirs and to analyze the impact of the fractures on the shale reservoirs properties and subsequent exploration and development the studied shale reservoir mainly displays tectonic fractures as well as various types of non tectonic fractures the non tectonic fractures mainly include over pressure fractures diagenetic fractures inter layer bedding fractures and fractures of mixed origins in the study area the tectonic fractures which were formed under the combined action of tensile and shear stress display the following characteristics the dip angle of the tectonic fractures varies significantly unfilled or half filled effective fractures have a high proportion these fractures are mainly oriented in the ne sw nne ssw and wnw ese directions with fractures in the ne sw direction accounting for the highest proportion the tectonic and non tectonic fracture development is affected by multiple types of factors such as the presence of faults mineral composition lithology abnormal pressure and organic matter content abnormally high pore pressure is a very important factor in the development of non tectonic fracture it is inferred that the over pressure is mainly related to hydrocarbon generation during thermal evolution fractures effectively improve the porosity and permeability of the shale reservoirs and the enhancement of permeability is particularly significant the current stress field affects the fluid flow capability of the fracture reservoirs and the present maximum principal stress in zhanhua depression is oriented in the nee sww direction which has a small angle with fractures in ne sw direction we propose that the fractures in this direction have the greatest connectivity and thus are a high priority target for petroleum exploration and development

petrographic and geochemical characterization of microfacies in a lacustrine shale oil system in the dongying sag jiyang depression bohai bay basin eastern china abstract petrology and rock eval analyses have been conducted in the lower third and upper fourth members lower es3 and upper es4 of the shahejie fm source rock intervals in well fanye1 in the dongying sag jiyang depression bohai bay basin eastern china the organic matter in rocks intersected by this well is dominated by lamalginite and bituminite and most samples contain type i or ii kerogen microfacies a h has been identified according to their organic mineral composition and structure using polished thin sections under microscopy the form and location of hydrocarbon residue occurrences mainly as solid bitumen with fluorescence are different in those microfacies microfacies a which is dominant in well fanye 1 is calcareous mudstone without lamination and the hydrocarbon residue is dispersed through the rock with some being present in subtle microfractures microfacies b and f are mostly composed of shale with adsorbed hydrocarbon indicated by fluorescence along mineral grains microfacies c is laminated argillaceous carbonate with hydrocarbon residue mainly occurring in thin microfractures along the bedding plane microfacies d and e are mainly carbonate and microfacies d is laminated with micrite and sparite and hydrocarbon residue occurrence is not only in the microfractures along the bedding but also in the micropores among the grains in the sparite layers which is the main place for hydrocarbon residue occurrence in microfacies type e without lamination microfacies g and h are both micrite microfacies g shows bioturbation and hydrocarbon residue occurs within small irregular microfractures along the bedding planes and pores only a little solid bitumen without fluorescence has been observed in microfacies h the rock eval oil saturation index osi s1 100 toc value is variable because of the different characteristics of these hydrocarbon residue occurrences osi values in microfacies a are normally high 74 8 242 8 mg hc g toc average of 117 2 mg hc g toc and likely much higher if microfractures develop 200 mg hc g toc osi values averaging 43 7 mg hc g toc are lowest in microfacies f because of adsorption on the shales and osi values are the highest in microfacies d 371 3 mg hc g toc and e 199 9 mg hc g toc since the hydrocarbon residues are stored both in microfractures and pores between the grains both osi values are high in microfacies g and h because of low toc content the combination of petrographic and osi analysis appear to be a promising tool for characterizing shale oil systems

geochemical characterization of organic facies in the dugi otok basin the adriatic sea yugoslavia sediments in the dugi otok basin are predominantly of upper and lower cretaceous age to characterize the organic facies we used geochemical analyses of core samples from different wells and a few outcrop samples geochemical data indicate that the carbonate sequences of the lower cretaceous represent a good source rock section with a high potential for petroleum the source rocks consist both of dark grey uniform micritic limestones and highly bituminous laminated limestones they are associated with oil stains and bitumen impregnations the organic matter is predominantly of marine origin algal sapropelic with a minor input of terrestrial components the extract contents of the samples are anomalously high but contain variable amounts of hydrocarbons and low saturated aromatic hydrocarbon ratios the maturation stage is immature to marginally mature as characterized by a high proportion of resins and asphaltenes with high sulphur content an even predominance of n alkanes a high ratio of acyclic isoprenoids to n alkanes pr ph 1 and a tmax around 430 c the organic facies in the dugi otok basin varies as it is possible to find both organic rich and oxidized organic lean sediments differences in organic facies have been caused by many changes in the depositional environment with tectonic processes contributing to the heterogeneity of the organic facies

modelling the petroleum generation and migration of the third member of the shahejie formation es3 in the banqiao depression of bohai bay basin eastern china abstract the mudstones in the third member of the shahejie formation es3 are the primary source rocks in the banqiao depression of bohai bay basin they are rich in organic matter with total organic carbon toc content up to 3 5 the sandstones in the es3 member are the deepest proven hydrocarbon reservoir rocks with measured porosity and permeability values ranging from 3 6 to 32 4 and from 0 01 md to 3283 7 md respectively one two and three dimensional basin modelling studies were performed to analyse the petroleum generation and migration history of the es3 member in the banqiao depression based on the reconstruction of the burial thermal and maturity history in order to evaluate the remaining potential of this petroleum province the modelling results are calibrated with measured vitrinite reflectance ro borehole temperatures and some drilling results of 63 wells in the study area calibration of the model with thermal maturity and borehole temperature data indicates that the present day heat flow in the banqiao depression varies from 59 8 mw m2 to 61 7 mw m2 and the paleo heat flow increased from 65 ma to 50 4 ma reached a peak heat flow values of approximately 75 mw m2 at 50 4 ma and then decreased exponentially from 50 4 ma to present day the source rocks of the es3 member are presently in a stage of oil and condensate generation with maturity from 0 5 to 1 8 ro and had maturity from 0 5 to 1 25 ro at the end of the dongying formation ed deposition 26 ma oil generation 0 5 ro in the es3 member began from about 37 ma to 34 ma and the peak hydrocarbon generation 1 0 ro occurred approximately from 30 ma to 15 ma the modelled hydrocarbon expulsion evolution suggested that the timing of hydrocarbon expulsion from the es3 member source rocks began from 31 ma to 10 ma with the peak hydrocarbon expulsion shortly after 26 ma secondary petroleum migration pathways in the es3 member of the banqiao depression are modelled based on the structure surfaces at 26 ma and present day respectively the migration history modelling results have accurately predicted the petroleum occurrences within the es3 member of the banqiao depression based on the calibration with drilling results of 10 oil producing wells one well with oil shows and 52 dry holes six favorable zones of oil accumulations in the es3 member of the banqiao depression are identified especially oil accumulation zones i and ii due to their proximity to the generative kitchens short oil migration distances and the presence of a powerful drive force

the origin of pyrobitumens in upper devonian leduc formation gas reservoirs alberta canada an optical and eds study of oil to gas transformation pyrobitumens are common within deep basin devonian carbonate gas reservoirs of the western canada sedimentary basin incident light microscopy and sem eds have been used to study the origin of pyrobitumens from upper devonian isolated reefs of the leduc formation west central alberta reflectance properties romax and romin coke microtextures and relative s c ratios are used to classify the pyrobitumens in portions of reservoir units where nso enriched low aromaticity crudes may have been dominant oil to gas transformations produced mainly low reflecting isotropic to fine grained mosaic coke microtextures within the reservoir pyrobitumens type a in contrast where normal crudes were most likely dominant in the reservoir units prior to thermal cracking pyrobitumens with high bireflectance and very anisotropic coarse flow to domain cokes dominate type b oil to gas cracking within some of the reservoir units resulted in overpressuring and is represented by highly deformed pyrobitumens with fibrous coke textures and high bireflectance relative concentrations of type a and b pyrobitumens vary vertically and temporally in some of the reefal buildups the variations in the dominant pyrobitumen types are attributed to crude oil alteration which preceded crude oil to gas transformation e g tar mats in some zones whereas other zones may have been altered contemporaneously with crude oil cracking the later may have resulted from the oxidation and sulphur enrichment of the crude oil during thermochemical sulphate reduction this reaction is prevalent within devonian evaporite carbonate strata of the western canada sedimentary basin generating copious volumes of h2s the interaction between crude oil and sulphur enriched highly alkaline fluids is suggested by the presence of high s c very fine grained late stage calcined needle cokes within brecciated pyrobitumens

middle eocene paleohydrology of the dongying depression in eastern china from sedimentological and geochemical signatures of lacustrine mudstone previous understanding that stratigraphic variability in lacustrine sequences is primarily caused by depositional processes governed by regional tectonics and climatic change remains to be tested on microscopic scale here we study the upper fourth member es4u of the eocene shahejie formation the major source rock of the dongying depression eastern china in order to understand stratigraphic heterogeneity and tectonic and climate controls on depositional processes in lacustrine mudstone our study integrates core descriptions microscopic observations and studies of mineralogy toc and chemical weathering proxies of cia and ln al2o3 na2o from two full bore cores and correlation of gamma ray logs from six wells across the depression we identified four major lithofacies including the interbedded evaporite and mudstone deposited in a shallow salt lake the silt bearing clay rich mudstone deposited in a pro delta environment within a shallow open lake the laminated calcareous mudstone deposited in a deep stratified meromictic lake with frequent earthquake activities and the massive calcareous mudstone deposited in a shallow and oxygenated lake the es4u member changed from the interbedded evaporite and mudstone dominated lithofacies association to silt bearing clay rich mudstone dominated lithofacies association and then laminated calcareous mudstone dominated lithofacies association suggesting basin wide changes in depositional processes lake level lake water chemistry and paleohydrology we suggest that these changes reflect balance between sediment and water supply and potential accommodation of the lake basin which were governed by paleoclimate in the lake drainage and extensional tectonics we infer that during the deposition of the es4u member the lake basin evolved from an underfilled lake basin with salty lake water under arid climate to a shallow balanced fill lake basin when climate became humid then to a deep balanced fill basin with stratified bottom lake water when climate became more humid and the basin was deepened by tectonic activity this study demonstrates that climate and tectonics both control paleolimnological changes and depositional processes of lacustrine mudstone

the influence of solid reservoir bitumen on reservoir quality 1 reservoir bitumen precipitates in pore systems from the alteration of trapped or migrating oil in carbonate and siliciclastic reservoirs reservoir bitumen is not readily identified on typical log suites where it is read as open porosity which has hampered its broad recognition as a reservoir altering cement when present as a solid it can be as influential on reservoir quality as carbonate silica or authigenic clay cements and should therefore be evaluated as part of the diagenetic evolution of any pore system whenever encountered five morphotypes of reservoir bitumen have been identified and named droplets carpets peanut brittle vesicular and digitate data from east texas gulf coast and west african examples indicate that reservoir bitumen can significantly reduce total effective porosity permeability can be significantly reduced by restricted or closed pore throats and by fines migration even when bitumen occurs in only moderate amounts the occurrence and distribution of bitumen on well field and regional scales can range from uniform and predictable to irregular and unpredictable but mappable through examination of core and cuttings within a trap bitumen can cause heterogeneity and form permeability barriers not related to depositional facies or pre bitumen diagenesis and reservoir quality it economic importance must be recognized when reservoir parameters are adversely affected impacting reserves calculations recovery factors and secondary recovery programs on a regional scale predictive models can be developed to determine the areas of a trend or portions of a stratigraphic section that are most likely to be affected and these models can be incorporated with other data for evaluating expected reservoir quality in regional play assessments

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in toarcian source rocks of different maturities abstract this study is part of a comprehensive research program on the generation and migration of petroleum from the organic rich posidonia shale lower toarcian jurassic of the hils syncline northern germany four cores of the complete posidonia shale with varying amounts of underlying pliensbachian and overlying aalenian mudstones provided the sample base depending upon their distance from a presumed subjacent heat source the vlotho massif the cores display progressive levels of increasing thermal maturation with r 0 values 0 48 0 68 0 88 and 1 45 which span the limits of the oil generation window primary stratigraphic lithologic and petrographic attributes of the four sections are all very similar each includes a lower marlstone member about 5 m thick overlain by 11 31 m of calcareous clay shale clay minerals calcite pyrite kerogen and quartz are the principal constituents thus there is no evidence that depositional conditions of the posidonia shale varied significantly over the sampled area the omnipresence of framboidal pyrite clearly formed from the activity of sulphate reducing bacteria at or near the depositional interface is strong evidence that uniform reducing anoxic conditions were persistent at all localities this conclusion supports the assumption that initially each section was identical in overall properties and that significant differences observed in geochemistry organic macerals and other properties are directly related to the variable levels of thermal maturation kerogen from the least mature section r o 0 48 is type ii and composed of alginite a alginite b liptodetrinite bituminite and some terrestrial sporinite vitrinite and inertinite macerals with increasing maturation the alginite macerals exhibit a progressive change in morphology and fluorescence properties alginite of the least mature section displays a strong green fluorescence at 0 68 r o alginite macerals exhibit yellow orange fluorescence and are structurally well preserved although geochemical data indicate generation and loss of large amounts of oil at 0 88 r o hydrocarbon generation is almost complete and few primary alginites remain they have been transformed into secondary liptinites designated as metaalginite which have similar fluorescence colours at the highest maturation level 1 45 r o metaalginites are only weakly fluorescent with a shift toward red colours calcite and or bitumen filled bedding plane micro and macrofractures occur exclusively in the organic rich posidonia shale at maturity levels of 0 68 r o and above such features are totally absent in the immature posidonia section and in the adjacent organic poor mudstones this observation indicates that the fractures developed in direct response to overpressuring i e pore pressure exceeding lithologic load related to oil and gas generation in the source rock the fractures undoubtedly provided important expulsion conduits for generated products

experimental study of fluid transport processes in the matrix system of the european organic rich shales ii posidonia shale lower toarcian northern germany abstract a laboratory study has been conducted to investigate the transport of gases he ar ch 4 and water in the matrix of lower toarcian posidonia shale samples from three shallow boreholes in northern germany the maturity of the organic matter of the shale samples ranged between 0 53 and 1 45 vitrinite reflectance vr r the measurements were performed at effective stresses ranging between 6 and 37 mpa and a temperature of 45 c the effects of different controlling factors including permeating fluid maturity anisotropy moisture content and effective stress on the fluid conductivity were analyzed and discussed permeability coefficients measured perpendicular and parallel to bedding 3 10 22 to 9 7 10 17 m 2 were within the range previously reported for other shales and mudstones they exhibited a strong dependence on permeating fluid maturity anisotropy moisture content and effective stress the permeability coefficients measured with helium as permeate were consistently higher up to two times than those measured with argon and methane permeability coefficients measured with water were up to three orders of magnitude lower than klinkenberg corrected gas permeability coefficients measured with helium and methane under similar experimental conditions among the samples studied the lowest porosity and permeability coefficients were measured on samples of intermediate thermal maturity 0 88 vr r oil window permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding permeability coefficients measured with he and ch 4 on a dry sample were up to two times higher than those measured on a sample with the as received moisture content all samples showed a nonlinear reduction in permeability parallel to bedding with increasing effective stress 6 37 mpa the permeability anisotropy and stress dependence of permeability were controlled by the mineralogy

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

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 3 estimating hydrocarbon expulsion from the shahejie formation abstract based on the distribution and geochemical characteristics of potential source rocks in the niuzhuang and guangbei sags and the niuzhuang south slope bohai bay basin the quantities of hydrocarbons expelled from the eocene oligocene shahejie formation were evaluated using a mass balance approach the results confirm that most of the hydrocarbons in the study area were generated and expelled from the shahejie formation source rocks in the niuzhuang sag the algae rich saline brackish water lacustrine es 4 oil shales of the shahejie formation from the bamianhe to wangjiagang region along the niuzhuang south slope exhibit excellent potential for early hydrocarbon generation but they are not the major source for proven oil reserves in the bamianhe region the source rocks for most of the known oil reserves in the study area occur in the es 4 mudstones in the deep part of the niuzhuang sag thus the commonly assumed origin of so called immature oils from source rocks shallower than the conventional oil window in this area needs revision

lake type controls on petroleum source rock potential in nonmarine basins based on numerous empirical observations of lacustrine basin strata we propose a three fold classification of lacustrine facies associations that accounts for the most important features of lacustrine petroleum source rocks and provides a predictive framework for exploration in nonmarine basins where lacustrine facies are incompletely delineated 1 the fluvial lacustrine facies association is characterized by freshwater lacustrine mudstones interbedded with fluvial deltaic deposits commonly including coal shoreline progradation dominates basin fill resulting in the stacking of indistinctly expressed cycles up to 10 m thick in map view the deposits may be regionally widespread but laterally discontinuous and contain strong facies contrasts transported terrestrial organic matter contributes to mixed type i iii kerogens that generate waxy oil type i kerogen is hydrogen rich and oil prone type iii kerogen is hydrogen poor and mainly gas prone the luman tongue of the green river formation wyoming and the honyanchi formation junggar basin china provide examples of this facies association which is also present in the songliao basin of northeastern china the central sumatra basin and the cretaceous doba doseo basins in west central africa 2 the fluctuating profundal facies association represents a combination of progradational and aggradational basin fill and includes some of the world s richest source rocks deposits are regionally extensive in map view having relatively homogenous source facies containing oil prone type i kerogen examples include the laney member of the green river formation wyoming the lucaogou formation junggar basin china the bucomazi formation offshore west africa and the lagoa feia formation campos basin brazil 3 the evaporative facies association represents dominantly aggradational fill related to desiccation cycles in saline to hypersaline lakes and may include evaporite and eolianite deposits sublittoral organic rich mudstone facies are relatively thin but may be begin page 1034 quite rich and widespread the highest organic enrichment coincides with the deepest lake stages low input of land plant organic matter results in minimal lateral contrasts in organic content in some cases a distinctive type i s sulfur rich kerogen may generate oil at thermal maturities as low as 0 45 vitrinite reflectance equivalent examples include the wilkins peak member of the green river formation wyoming the jingjingzigou formation junggar basin china the jianghan and qaidam basins china and the blanca lila formation argentina

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 1 source rock characterization and quantitative assessment abstract in the prolific zhanhua depression of the bohai bay basin eastern china over 76 of the proven petroleum reserves occur in the neogene guantao and minhuazhen formations detailed geological and geochemical mapping of the phanerozoic strata in this area reveals that oil shales and dark mudstones in the es4 es3 and es1 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in several discrete sag areas bounded by extensive basement related fault networks in contrast source rocks along the paleo topographic highs are currently immature with respect to the generation of conventional oils this study examined the key molecular characteristics for the common isoprenoid hopanoid and steroid biomarkers in relation to source facies variations in lacustrine sediments the hydrocarbon source potential and expulsion efficiency for each of the source rock units were evaluated which integrated the source rock characteristics with regional thermal subsidence and sediment burial an important observation made during this study is the striking contrast between the source potential and proven oil reserves within each stratigraphic section illustrating how significant the migration of hydrocarbon fluids derived from deep mature source kitchens through over 2000 m of fine grained formations must have been to form several giant oil accumulations in the shallow strata these results support the concept of the neogene fault fracture mesh petroleum plays proposed by zhang et al 2004 marine petroleum geology 21 651 668 and the vital role that the faults and fracture systems have in controlling hydrocarbon migration conduits and accumulation habitat in this rift basin

pyrobitumen occurrence and formation in a cambro ordovician sandstone reservoir fahud salt basin north oman the cambro ordovician barik sandstone reservoirs in the fahud salt basin in oman contain bitumen which may fill up to 40 of the porosity in well jaleel 1 this bitumen was isolated according to kerogen procedure and typed by nmr elemental analysis and density measurements the isolated bitumen is characterized by 1 a highly aromatic character nmr 75 caro h c atomic ratio 0 65 2 a very high sulphur content 4 2 and 3 a relatively high density 1 3 1 4 g cm3 the insolubility and the reflectivity of the bitumen 1 2 vr qualify it as a low mature pyrobitumen the combination of rock eval and density data was used to calculate the actual volume of the pyrobitumen in the rock as a percentage of porosity it was found that the pyrobitumen volume shows a negative correlation with total porosity indicating that small pores are more invaded by bitumen than larger ones finally closed system pyrolysis experiments performed on oils with different nso contents indicate that an in situ oil with a very high content of nso compounds is required to generate such large amounts of pyrobitumen in the pore system these observations suggest that the precursor oil of the current pyrobitumen was a very heavy oil tentatively assumed to be the result of a severe biodegradation basin modeling shows that the reservoir was charged already in devonian times a major uplift brought the oil accumulation near the surface during the carboniferous and a rather regular burial to the present day position 4500 m 140 c loosveld et al 1996 this scenario involving a residence time at shallow depth strengthens the biodegradation hypothesis the numerical modeling which involves the ifp kinetic model for secondary oil cracking suggests that pyrobitumen formation is a very recent event inclusion of pyrobitumen particles within quartz overgrowth containing fluid inclusions provides an upper temperature limit for the beginning of pyrobitumen formation which comforts the result of kinetic modelling

fault fracture mesh petroleum plays in the jiyang superdepression of the bohai bay basin eastern china abstract based on the results of laboratory simulation experiments and field observations the concept of fault fracture mesh petroleum play is proposed to explain the secondary petroleum accumulations in the neogene reservoirs of the jiyang superdepression bohai bay basin eastern china a well defined fault fracture mesh petroleum play usually contains three basic elements an oil source network at the base a transient storage for migrating hydrocarbons in the middle and a petroleum accumulation network at the top the oil source network provides fairways for hydrocarbons generated in a deep source to migrate vertically upward to shallow strata often consisting of primary faults and fracture zones and or regional unconformities in direct contact with mature petroleum source beds and secondary faults intercepting lenticular fluvial sandstones the transient storages for migrating hydrocarbons include the thick porous mat or sheet like sandstones deposited under the fluvial braided stream setting and occurring over relatively large geographic areas these sandstones serve as temporary storage spaces through which deep sourced petroleum fluids migrate further either laterally or vertically into shallower reservoirs the upper petroleum accumulation network provides suitable habitats for oil and gas accumulation comprising structural lithologic stratigraphic and combination traps the jiyang superdepression of the bohai bay basin hosts several excellent examples of the fault fracture mesh petroleum play where hydrocarbons in the neogene reservoirs were derived either directly from eocene oligocene source rocks or from the redistribution of pre existing oil accumulations in the deeper reservoirs reactivation of basement involved faults and regional unconformities provided conduits for channeling the pre neogene hydrocarbons into the shallow strata the magnitudes and frequencies of the faulting activities and their relative timings to those of peak oil generation and expulsion were critical factors for controlling the quantities of hydrocarbons transmitted to the neogene strata the thick sandstones and conglomerates in the lower guantao formation acted as excellent transient storages for the deep sourced oils which were then trapped to form accumulations in the shallow structural lithologic stratigraphic and combination traps of the guantao ng minhuazhen nm formations with the recent discovery of several giant oilfields in the shallow neogene reservoirs both onshore and offshore bohai bay basin the proposed fault fracture mesh petroleum play concept helps the exploration geologists to modify and clarify long held traditional concepts of petroleum play types in this basin and expand upon the new exploration horizons of the shallow subtle petroleum traps

kinetics of oil group type generation and expulsion an integrated application to dongying depression bohai bay basin china pyrolysis of two kerogens isolated from the e2 3s 3 3 and e2 3s 1 4 source rocks in the niuzhuang sag dongying depression bohai bay basin china was performed in a confined system the products were extracted with solvent and separated using micro column chromatography into group type fractions saturates aromatics resins and asphaltenes with the kerogen residue in each case undergoing swelling with a variety of solvents the kinetics for generation and retention of crude oil and its group type fractions from the kerogens were studied and the kinetic parameters applied to modeling generation and retention of crude oil and its fractions from the e2 3s 3 3 and e2 3s 1 4 source rocks on the basis of burial and thermal history of the niuzhuang sag the results show that the normal oil was generated at about 4 26 ma and 24 85 ma ago but expelled at about 3 96 ma and 17 46 ma ago respectively from e2 3s 3 3 and e2 3s 1 4 source rocks the current proportions of the expelled saturates aromatics and nsos are about 60 15 and 25 respectively

geochemistry and correlation of oils and source rocks in banqiao sag huanghua depression northern china abstract located in the western part of huanghua depression s central segment in the bohai bay basin the banqiao sag is a significant sedimentary basin the crude oil produced has low density low viscosity low sulfur and high wax content crude oil types include conventional crude as well as condensate oil gas light oil and low maturity oil four possible source rocks are present within the banqiao sag however at present the oil source is not very clear rock eval pyrolysis stable carbon isotope composition and biomarker analysis were conducted on 26 source rock core samples in the banqiao sag to evaluate their characteristics results indicate that the shahejie formation 43 32 8 ma has source rocks that can be graded between poor to excellent quality they were deposited in a marine based reducing environment and rich in organic matter sha 1 member es1 and sha 3 member es3 are considered thermally immature to mature based on various maturity indicators 17 crude oil samples from the banqiao sag were compared with these rocks biomarkers and stable carbon isotope parameters the analyzed crude oils were divided into 4 groups based on carbon isotope composition and q type cluster analysis qca there are two sets of effective hydrocarbon source rocks in the study area s shahejie group i e es1x and es3 contributing to the oil found in the structural belts oil and source rock correlation results indicate that group b1 oil is probably derived from highly mature es3 group b2 oil is most likely derived from a mixed mature es3 and early mature es1 group b3 oil is derived from es3 in tanggu xingang buried hill structural belts and from es1 in immature or low mature stage in banqiao sag group b4 oil is derived from mature es3 in banqiao sag with little early mature es1 this study can highly benefit future oil and gas exploration work in the banqiao sag