application of organic facies studies to sedimentary basin analysis a case study from the yitong graben china abstract an organic facies is defined in this paper as a mappable stratigraphic unit containing organic matter om of a particular genetic type in certain abundance several concepts concerning organic facies are proposed and their significance in basin analysis is discussed in detail a combined sedimentological and organic geochemical investigation has been carried out in the yitong graben and four organic facies and one organic parafacies have been recognized distinct organic basin fill sequences obfs and organic facies association ofa were developed in different sub units of this graben which indicates that the yitong graben had undergone two tectonic subsidence cycles such tectonic subsidence patterns could not have been found out without detailed organic facies analysis confirming that organic facies especially obfs and ofa study is a very useful tool not only for prediction and three dimensional mapping of petroleum source rocks but also for sedimentary basin analysis

sublacustrine gravity induced deposits the diversity of external geometries and origins abstract our current knowledge of deep water depositional systems is mainly built of extensive achievements obtained from marine basins although lacustrine basins are important oil gas productive areas of the world gravity induced deposits in these basins are poorly understood in the literature when compared with those documented in marine basins based on new insights from 3d seismic data this paper attempts to investigate the effect of the interaction between gravity induced flows and lake floor topography on the resulting external geometry of gravity induced deposits in the cretaceous qingshankou and nenjiang formations of the songliao basin slb eight different shapes of gravity induced deposits were identified in the slb and which were in turn grouped into four distinct categories according to external shape internal architecture and spatial assembly 1 channel fan complexes 2 fan form complexes 3 strip form complexes and 4 pond form complexes furthermore fan form complexes can be subdivided into four subcategories isolated fan with compressional ridges isolated fan without compressional ridges mother son fans and stacked fans strip form complexes can be subdivided into two subcategories including strip form controlled by gully system and strip form controlled by growth faults sediment transport mechanism density flows or mass transport flows and lake floor topography together influence the pathways runout distances discharge places and internal characteristics of gravity induced deposits which could ultimately influence external geometries of gravity induced deposits in the slb consequently sublacustrine gravity induced deposits does not exhibit classic fan like geometry frequent and powerful hyperpycnal flows associated with flood events are fairly common and develop channel distal fan complexes mtds exhibit various external geometries which are significantly affected by growth faults slope gullies gradient and basin floor irregularities the new depositional model built from the slb is vital to understanding the distribution of gravity flow deposits in a sublacustrine slope

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

post rift anomalous thermal flux in the songliao basin ne china as revealed from fission track thermochronology and tectonic analysis abstract the songliao basin in northeastern china contains a nearly complete cretaceous sedimentary record it offers an unparalleled opportunity for studying the thermal behavior of a rifting basin adjacent to a subduction zone during various stages of its evolution the post rift thermal history of the songliao basin is here documented by systematic apatite and zircon fission track analyses on newly exhumed sandstone samples from the upper cretaceous quantou and qingshankou formations the combination of thermochronology results and stratigraphic records indicates that there was an unambiguous post rift thermal overprinting event in the songliao basin during the deposition of the nenjiang formation at 85 80 ma this fossil thermal anomaly has not been previously recognized from organic maturity indicators and or subsidence modeling the zircon fission track results indicate an estimated maximum paleo temperature as high as 170 220 c near the daqing placanticline fission track analyses of sampled apatites further define a restricted thermal anomaly in the central part of the basin based on the context of local lithospheric structure and adjacent plate tectonic history we conclude that the late cretaceous westward subduction of the paleo pacific plate not only produced vertical motions and directly controlled the topography of the songliao lake but also dominated the mantle heat flow beneath east asia this finding has significant implications for the evolution of thermal flux in the basin

numerical simulation of the thermal maturation oil generation and migration in the songliao basin northeastern china abstract the discovery of the giant daqing oil field in the songliao basin led to the realisation of the significant petroleum potential of non marine basins in order to reconstruct the basin evolution and oil formation an integrated organic geochemical basin modelling study along a regional transect across the songliao basin was conducted it provided a regional heat flow evolution model and revealed post orogenic or late syn orogenic maturation in the central depression and pre orogenic maturation in the southeast uplift zone kinetic parameters of petroleum generation for the lacustrine source formations are the basis for the simulation of oil generation and migration in the songliao basin using the principle activation energy peaking at 54 kcal mol and a pre exponential factor of about 4 2 1027 ma 1 the simulation obtained a relatively good match with the measured transformation ratios the qingshankou formation in the west and east central depressions constituted the major source in the basin major oil generation migration and accumulation occurred during the early tertiary in the west central depression the generated oils migrated upwards into the yaojia formation followed by the updip migration into the daqing anticline and towards the local structural high along the west slope in contrast the oil migration in the east central depression was dominated by the downward movement from the lower member of the qingshankou formation followed by the updip migration towards the caoyang anticline the simulated oil accumulations are in good agreement with discovered oil fields implying a potential application of the model for prediction and evaluation of new exploration targets in the basin

structural style and its relation to hydrocarbon exploration in the songliao basin northeast china the songliao basin in northeast china is a mesozoic rift basin characterized by mesozoic and cenozoic hydrocarbon systems the songliao basin was initiated by southeast to northwest lithospheric extension during the late jurassic the extensional phase was dominated by two fault sets l shallow to moderately dipping normal faults and 2 steeply dipping transfer faults the extensional structures are characterized by half grabens a second short extensional tectonic overprinting phase occurred during the early qingshankou early albian 100 to 97 ma faults that occur in the quantou formation and the qingshankou formation are growth faults t2 faults which trend mostly nnw and occur predominantly at the sites of basement faults and structural bend zones located between sag and uplift and basement uplifts the basin broadly subsided during the denglouku quantou aptian 125 to 100 ma and the late qingshankou late albian 97 to 94 ma to yaojia nenjiang cenomanian to campanian 94 to 73 ma respectively positive inverted structures developed during the late cretaceous to the cenozoic in the songliao basin these are classified into two types positive inversion structures controlled by reactivation of early normal faults and inversion structures not controlled by earlier faults the major extensional structures exerted a range of controls on both sedimentation and deformation during the subsequent phases of basin evolution two thermotectonic rifting events during the late jurassic and early qingshankou play a major role in organic matter thermal evolution the timing of formation of structural traps in the basin matches that of hydrocarbon generation and migration structural traps formed during late jurassic early qingshankou and late cretaceous to paleocene 73 to 56 ma late jurassic organic rich source rock reached its peak oil generation from the time of deposition of member deng 3 4 of the denglouku formation 119 to 116 ma to that of member qing 1 of the qingshankou formation 100 to 97 ma qing 1 of the qingshankou formation and nen 1 of the nenjiang formation organic rich source rocks reached their peak oil generation from the time of deposition of the upper mingshui formation to that of the upper yi an formation and from the time of deposition of the taikang formation to that of deposition of the quarternary respectively

fault linkage patterns and their control on the formation of the petroleum systems of the erlian basin eastern china abstract fault linkage patterns in rift basins are very common while the process of fault linkage may be very short it changes sedimentation patterns before and after linkage and controls the development of half grabens the propagation and growth of boundary faults can be divided into a simple fault propagation pattern and a fault growth linkage pattern based on structural style sedimentation patterns and oil source correlations in the erlian basin three types of grabens and petroleum systems can be identified the abei graben is controlled by a single boundary fault and forms an independent petroleum system the saihantala graben is controlled by several linked faults which also has an independent petroleum system the wuliyasitai depression controlled by two boundary fault segments which results in two petroleum systems as not all half grabens develop one petroleum system they may therefore have two or more systems the relay ramps between fault segments before linkage are the locations of deposition of sands and conglomerates and consequently are the focus areas for stratigraphic lithologic trap exploration

palaeoenvironmental conditions during deposition of the upper cretaceous oil shale sequences in the songliao basin ne china implications from geochemical analysis abstract excellent hydrocarbon source rocks oil shales containing type i organic matter om were deposited in the continental songliao rift basin during the late cretaceous a major contribution of aquatic organisms dinoflagellates green algae botryococcus and minor input from macrophytes and land plants to om accumulation is indicated by n alkane distribution steroid composition and 13 c values of individual biomarkers microbial communities included heterotrophic bacteria cyanobacteria and chemoautotrophic bacteria as well as purple and green sulfur bacteria the presence of methanotrophic bacteria is indicated by 13 c depleted methyl hopane the sediments were deposited in a eutrophic alkaline palaeolake highly reducing saline bottom water conditions and a stratified water column existed during om accumulation of the qingshankou formation and member 1 of the nenjiang formation this is indicated by low pristane phytane gammacerane index and mttc ratios and the presence of carotane and aryl isoprenoids however an abrupt change in environmental conditions during deposition of member 2 of the nenjiang formation is indicated by significant changes in salinity and redox sensitive biomarker ratios a freshwater environment and suboxic conditions in the deep water prevailed during this period higher input of terrigenous om occurred during deposition of the upper nenjiang formation good oil to source rock correlation was obtained using biomarker fingerprints of oil stained sandstone from the quantou formation and oil shales from the qingshankou formation based on the extent of isomerisation of c 31 hopanes the oil was most probably derived from oil shales of the qingshankou formation in deeper parts of the basin

rapid continuous streaking of tremor in cascadia nonvolcanic tremor is a recently discovered weak seismic signal associated with slow slip on a fault plane and has potential to answer many questions about how faults move its spatiotemporal distribution however is complex and varies over different time scales and the causal physical mechanisms remain unclear here we use a beam backprojection method to show rapid continuous slip parallel streaking of tremor over time scales of several minutes to an hour during the may 2008 episodic tremor and slip event in the cascadia subduction zone the streaks propagate across distances up to 65 km primarily parallel to the slip direction of the subduction zone both updip and downdip at velocities ranging from 30 to 200 km h we explore mainly two models that may explain such continuous tremor streaking the first involves interaction of slowly migrating creep front with slip parallel linear structures on the fault the second is pressure driven fluid flow through structurally controlled conduits on the fault both can be consistent with the observed propagation velocities and geometries although the second one requires unlikely condition in addition we put this new observation in the context of the overall variability of tremor behavior observed over different time scales

pyrite morphology in the first member of the late cretaceous qingshankou formation songliao basin northeast china abstract the study of sedimentary pyrite morphological characteristics provides useful information on depositional environments and early diagenic processes and can be used as an indicator of redox conditions in ancient lake bottom waters the results of this study in the songliao basin in northeastern china show that euhedral crystals and framboids are the dominant pyrite forms in the mudstones of the first member of the qingshankou formation k2qn1 the framboidal size distribution indicates that during the deposition of k2qn1 redox conditions in the bottom water fluctuated from oxic dysoxic to euxinic anoxic to oxic dysoxic the presence of euxinic anoxic bottom water suggests that an anoxic event developed in the songliao ancient lake and continued for 196 ka the development of an anoxic bottom environment was the most important factor in hydrocarbon source rock formation in the songliao basin

formation and evolution of nonmarine petroleum in songliao basin china in large lake basins source rocks containing sapropelic kerogen have a high transformation ratio and a high potential for petroleum and they offer the material basis for the formation of a large nonmarine oil field on the basis of geologic and geochemical data and the results of thermal simulation of kerogen it is confirmed that the maturation sequence of kerogen is type i type ii and type iii

application of aromatic compounds as maturity indicators in source rocks and crude oils concentration ratios of aromatic compounds such as naphthalenes phenanthrenes and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils generally these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl aromatic homologues towards thermally more stable isomers a combination of both concepts in the methylphenanthrene index mpi resulted in an excellent maturity parameter as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance rm between 0 65 and 1 4 i e in the zone of oil formation in cases that rm measurements were ambiguous this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance rc values from the mpi on the other hand for potential petroleum source rocks reaching maturity at relatively low temperatures the influence of the organic matter type on the aromatic distributions cannot be neglected consequently organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils since the impact of the organic facies is strongly reduced with increasing maturity aromatic maturity parameters are particularly useful in the maturity evaluation of post mature crude oils and condensates in contrast to biological markers substantially higher concentrations of the key alkyl aromatics persist at elevated maturation levels thus aromatic maturity parameters should be considered as versatile tools in organic maturation studies and can complement established maturity indicators based on steranes and terpanes

genetic sequence stratigraphic framework depositional style and hydrocarbon occurrence of the upper cretaceous qyn formations in the songliao lacustrine basin northeastern china the qingshankou yaojia and nenjiang qyn formations in the songliao basin of northeastern china can be used to illustrate the application of sequence stratigraphic analysis in a lacustrine setting and to provide a good example of hydrocarbon occurrence in a lacustrine stratigraphic framework the qyn genetic stratigraphic sequence bounded by maximum flooding surfaces or beds is a low frequency second order sequence or supercycle in a lacustrine basin with a ramp margin use of subaerial unconformity and transgressive surfaces allows further subdivision of the qyn sequence into a progradational systems tract lowstand prograding complex and retrogradational systems tract delta system styles are dominated by the physiography and relative intensity of fluvial and wave rocesses q1 and n1 maximum flooding related deposits used to identify the qyn genetic stratigraphic sequence boundaries are the main petroleum source rocks and regional seals and play an important role in determining hydrocarbon distribution in the songliao basin the y1 lowstand prograding complex and y2 3 retrogradational systems tract in the northern part of the basin are the most important reservoir and producing intervals within the qyn sequence

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

high resolution geochemical analysis of organic matter accumulation in the qingshankou formation upper cretaceous songliao basin ne china abstract in the well known continental songliao basin the oil shale successions of the cretaceous qingshankou formation are excellent source rocks for oil the oil shale layers with high toc total organic carbon contents developed at the bottom of the formation they are divided into the lower oil shale toc up to 18 3 and the upper oil shale layer toc up to 14 4 the oil shale layers and accompanying mudstones are investigated by high resolution analyses of drill cores by pyrolysis organic petrology organic and inorganic geochemistry the results demonstrate the predominance of type i kerogen derived from algal microbial mats i e lamalginite however increased proportions of plant derived organic matter are indicated by rock eval parameters and the presence of vitrinite in the upper oil shale as evidenced from lower concentrations of hopanes higher sinking rates of organic matter om are suggested to have been responsible for a lower extent of microbial degradation during accumulation of the lower oil shale unit the environmental conditions are characterized by anoxic saline bottom water overlain by an extended zone of freshwater favorable for om production and preservation under these preconditions oil shale thickness and quality are governed by primary productivity related to accommodation space and nutrient supply redox conditions within the water column are the key factor controlling organic matter preservation

an organic geochemical investigation of crude oils from shanganning jianghan chaidamu and zhungeer basins people s republic of china abstract eighteen oils from four different oil producing basins in china have been characterized using a variety of organic geochemical techniques the source materials for these oils were deposited under a variety of environmental conditions and this study investigates the use of geochemical parameters in differentiating the resultant oils the parameters discussed are based on relative amounts and distributions of both individual and groups of biomarkers including organosulphur compounds and the carbon isotopic composition of the aliphatic and aromatic fractions examination of the oils showed that those from the zhungeer basin thought to be derived from source rocks formed in a brackish lacustrine environment possessed high concentrations of tricyclic terpanes relative to pentacyclic hopanes and a predominance of 24 methyl and 24 ethylcholestanes c28 and c29 respectively over cholestanes c27 which were virtually absent oils believed to be derived from source rocks deposited in the saline depositional environment of the jianghan basin were characterized by a large amount of gammacerane relative to 17 21 30 homohopanes c31 22r and 22s in general those oils considered to be derived from source rocks deposited in fresh water lacustrine environments shanganning and chaidamu basins had small amounts of tricyclic terpanes relative to pentacyclic hopanes the presence of an unknown c30 pentacyclic terpane small amounts of extended hopanes c31 c35 relative to 17 21 hopane and relatively large amounts of 24 ethylcholestanes 20r and 20s relative to total stearanes it appears therefore that the distribution of biomarkers may be used to differentiate oils derived from different lacustrine environments

patterns of displacement along large normal faults implications for basin evolution and fault propagation based on examples from east africa seismic reflection data across six boundary faults from east africa have revealed information about the way boundary faults develop with respect to the synkinematic basin fill previous models of basin fill assume that lateral fault propagation and deposition occur simultaneously which gives rise to along axis onlap of the basin fill onto the prerift basement propagating basin model seismic reflection data from boundary faults in east africa show only rare evidence for along axis broadening of the basins instead the basin margins appear to be fixed from a very early stage in the basin history nonpropagating basin model depocenters shift not by gradual lateral propagation but by abrupt changes in location such observations indicate that boundary fault propagation to near maximum length occurs rapidly during the very early stages of rifting probably by linkage of numerous small faults displacement then builds following the b value earthquake model along the fault during basin development out of phase with the main propagation phase mature fault systems may have experienced several phases of jumps in fault length or the location of fault activity major boundary faults exhibit three basic patterns of evolution these patterns of evolution can have many variants and include 1 simple displacement where maximum displacement is approximately at the center of the fault and decreases gradually toward the fault tips 2 variable along strike displacement that incorporates linkage of in line or en echelon relatively large displacement faults of similar age leaving transverse anticlines and synclines and 3 asymmetric propagation where one tip of a fault remains more or less fixed while the other tip propagates a relatively long distance asymmetric propagation can occur smoothly and gradually or alternatively there can be a jump in the location of the fault and a new fault of different age can form along strike from the older fault eventually the new fault propagates and links with the older fault segment reactivating the older fault to some extent addition ally long lived faults may be composites of fault types 1 3

geochemistry of natural gases in deep strata of the songliao basin ne china chemical composition and stable carbon isotopic studies were undertaken for 27 gas samples from deep strata of the xujiaweizi depression in the songliao basin to investigate their origin gas molecular and carbon isotopic compositions show great variety methane is the main component for all studied samples and its content ranges from 57 4 to 98 2 with an average of 90 1 gas wetness ranges from 0 8 to 16 7 with an average of 2 7 the main non hydrocarbon gases are carbon dioxide and nitrogen with an average of 4 0 and 3 2 respectively carbon isotope data suggest that these deep strata gases are mainly coal type gases mixed with minor amounts of associated oil type gases coal type gases are characterized by heavier carbon isotopic values and drier chemical compositions these gases were generated from the lower cretaceous shahezi formation coals interbedded shales with type iii kerogen during the postmature stage of hydrocarbon generation oil type gases are characterized by lighter carbon isotope and higher wetness which were generated from the lower cretaceous shales with type ii kerogen in the shallow strata during the early mature stage of hydrocarbon generation mixing of two different gases causes unusual carbon isotopic distribution patterns with lighter isotopic values in higher numbered carbons in most gases the discovery of coal type gases in the songliao basin provides new prospects for the exploration in this region

a family of repeating low frequency earthquakes at the downdip edge of tremor and slip we analyze an isolated low frequency earthquake lfe family located at the downdip edge of the main episodic tremor and slip ets zone beneath western washington state the 9000 individual lfes from this repeating family cluster into 198 swarms that recur roughly every week cumulative lfe seismic moment for each swarm correlates strongly with the time until the next swarm suggesting that these lfe swarms are time predictable precise double difference relative locations for 700 individual lfes within this family show a distribution that is approximately 2 km long and 500 m wide elongated parallel to the relative plate convergence direction the distribution of locations 300 m vertical spread lies within a few hundred meters of two different plate interface models and has a similar dip peak to peak lfe s wave amplitudes range from 0 2 to 18 nm individual lfes exhibit a trend of increasing magnitude during swarms with smaller events at the beginning and the largest events toward the end the largest lfes cluster in a small area 300 m radius coincident with maximum lfe density we propose that the less concentrated smaller lfes act to unlock this patch core allowing it to fully rupture in the largest lfes usually toward the end of a swarm we interpret the patch responsible for producing these lfes as a subducted seamount on the downgoing juan de fuca jdf plate lfe locking efficiency slip estimated during 5 years from summing lfe seismic moment divided by plate rate determined slip is at most 20 and is highly concentrated in two 50 m radius locations in the larger patch core estimated individual lfe stress drops range from 1 to 20 kpa but could also be significantly larger

observations on internal stability of cohesionless soils introduction internal stability refers to the ability of the coarser fraction of a soil to prevent migration of its finer fraction as a result of seepage flow skempton brogan 1994 report findings from piping tests on four well graded to gap graded sandy gravels flow was imposed in an upward direction without surcharge loading and without vibration an abrupt transition was noted from stable to unstable states defined by the ratio d9 15 d9 85 1 4 4 as postulated by kezdi 1979 and attributed to work published in 1969 the latter concept was conceived independently by de mello 1975 advocated by sherard 1979 for a ratio 4 to 5 and recommended by lowe 1988 for a ratio of 5 it involves splitting the gradation at arbitrary points along the curve to yield d9 15 of the coarse fraction and d9 85 of the fine fraction as illustrated in fig 1 for gradation g3 c in this study we further evaluate the kezdi 1979 criterion through laboratory permeameter testing of five soils fig 1 and table 1 and compare the results with a dataset of 34 gradations extracted from kenney lau 1985 1986 and honjo et al 1996

effective petroleum source rocks of the world stratigraphic distribution and controlling depositional factors six stratigraphic intervals representing one third of phanerozoic time contain petroleum source rocks that have provided more than 90 of the world s discovered original reserves of oil and gas in barrels of oil equivalent the six intervals are 1 silurian generated 9 of the world s reserves 2 upper devonian tournaisian 8 of reserves 3 pennsylvanian lower permian 8 of reserves 4 upper jurassic 25 of reserves 5 middle cretaceous 29 of reserves and 6 oligocene miocene 12 5 of reserves this uneven distribution of source rocks in time displays no obvious cyclicity and the factors that controlled the formation of source rocks vary from interval to interval maps that show facies structural forms and petroleum source rocks were prepared for this study analysis of the maps indicates that several primary factors controlled the areal distribution of source rocks their geochemical type and their effectiveness i e the amounts of discovered original conventionally recoverable reserves of oil and gas generated by these rocks these factors are geologic age paleolatitude of the depositional areas structural forms in which the deposition of source rocks occurred and the evolution of biota the maturation time of these source rocks demonstrates that the majority of discovered oil and gas is very young almost 70 of the world s original reserves of oil and gas has been generated since the coniacian and nearly 50 of the world s petrole m has been generated and trapped since the oligocene the term petroleum as used in this study includes oil gas condensate and gas but does not include bitumen and other solid and semisolid oil derivatives

guidelines for kinetic input to petroleum system models from open system pyrolysis abstract reliable basin and petroleum system models bpsm require accurate kinetic parameters for the conversion of source rock kerogen to petroleum the purpose of this paper is to dispel widespread uncertainty about kinetic input to bpsm by providing guidelines based on interpretation of previously published data for 81 worldwide source rocks containing various kerogen types kinetic response is unrelated to kerogen type as defined by rock eval pyrolysis hydrogen index default kinetics in bpsm software may differ from that for the same kerogen type in different study areas use default kinetics with caution when appropriate measured kinetics are unavailable measure kinetic parameters using thermally immature equivalents of the source rock which may require multiple samples because kerogen kinetics can vary laterally and vertically in each source rock descriptions of depositional environment are insufficient to define kerogen type or kinetic response in different basins optimize multiple run programmed pyrolysis results for both the activation energy ea and frequency factor a assuming a universal value of a rather than optimizing both ea and a can yield temperature errors of 20 c or more when extrapolated to geologic time alternative kinetic models to calculate vitrinite reflectance ro may be more accurate than easy ro for bpsm calibration in the aurora 1 and inigok 1 wells in alaska basin ro and easy rodl more accurately replicates the dogleg in vitrinite reflectance versus depth commonly observed in wells at depths corresponding to 0 7 1 0 ro

biomarker characterisation of an oil and its possible source rock from offshore korea bay basin abstract comparison of biomarker distributions in an oil and in sedimentary rock samples from an offshore well in korea bay basin indicates that an upper jurassic 500 m thick mudstone zone could form the source rock for the oil the organic material in this zone appears to be h rich and of sufficient abundance from pyrolysis measurements to generate oil it seems to derive primarily from bacterial lipids as reflected in high levels of bacterial hopanoids and predominance of amorphous kerogen macerals a higher plant wax contribution to the organic matter is indicated by an oep in n akanes c 20 and there may also be an autochtonous algal contribution sedimentological and biomarker evidence is consistent with input from a river delta prograding into a deep freshwater lake biomarker distributions suggest that pronounced bacterial reworking of allochthonous higher plant material had occurred in probably anoxic conditions high heat flows in a rapidly subsiding extensional basin probably account for the observed extensive aromatisation of monoaromatic steroidal hydrocarbons at a relatively early stage of sterane isomerisation

30 norhopanes their occurrence in sediments and crude oils abstract sediments and crude oils have been analysed using gc ms techniques and shown to contain two homologous series of hopanes namely 30 nor 17 h hopanes and 25 30 bisnor 17 h hopanes as well as the common 17 h hopanes homologues c28 to c34 of the 30 nor 17 h hopane series have been identified in crude oils associated with carbonate source rocks the abundances of these hopanes relative to the 17 h hopanes in the soluble organic matter from carbonate sediments has been shown to depend upon sample maturity the more mature samples having higher relative abundances of these norhopanes a comparison of the relative abundances of the norhopanes in the soluble organic matter of sediments and in the hydrocarbon fraction released when the extracted sediments were pyrolysed showed that the 30 nor 17 h hopanes were more abundant in the pyrolysis product these observations indicate that the proportion of norhopanes relative to normal 17 h hopanes in bound form in the kerogen is greater than that present in the soluble form and so kerogen cracking proceeds with increased maturity of the sediments and a relative enrichment of these norhopanes occurs in the soluble fraction the series of 25 30 bisnor 17 h hopanes has been identified in a severely biodegraded crude oil from a putative carbonate source this observation together with the reported occurrence of enriched 25 norhopanes in severely biodegraded crude oils suggests that 25 30 bisnor 17 h hopanes may be biomarkers for severely biodegraded crude oils from carbonate rich source rocks

geochemical characteristics and correlation of oil and nonmarine source rocks from mongolia new bulk and molecular organic geochemical analyses of source rock and oil samples from mongolia indicate the presence of lacustrine sourced petroleum systems in this frontier region samples of potential source rocks include carbonate coal and lacustrine mudstone lithologies that range from paleozoic to mesozoic in age and represent a variety of tectonic settings and depositional environments rock eval and total organic carbon data from these samples reflect generally high quality source rocks including both oil and gas prone kerogen types mainly in the early stages of generation bulk geochemical and biomarker data indicate that lower cretaceous lacustrine mudstone found in core from the zuunbayan field is the most likely source facies for the east gobi basin of southeastern mongolia oil and selected source rock samples from the zuunbayan and tsagan els fields both in the east gobi basin demonstrate geochemical characteristics consistent with nonmarine source environments and indicate strong evidence for algal input into fresh to brackish water source facies including elevated concentrations of unusual hexacyclic and heptacyclic polyprenoids despite similarities between zuunbayan and tsagan els oil samples biomarker parameters suggest higher algal input in facies sourcing zuunbayan oil compared to tsagan els oil tsagan els oil samples are also generated by distinctly more mature source rocks than oil from the zuunbayan field based on sterane and hopane isomerization ratios

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

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

genetic features of petroleum systems in rift basins of eastern china abstract most oil bearing basins in eastern china are mesozoic cenozoic continental rifts which have played a habitat for oil and gas in china investigation of the petroleum systems may give a better understanding of the oil and gas habitats in these basins of the essential elements of the petroleum system the source rock is the most important in rift basins however rift tectonic evolution controls all the essential elements and processes necessary for a petroleum system a four stage evolution model is suggested for the controls in the rift basin a rift basin may consist of sub basins depressions and sub depressions and major moderate and minor uplifts a depression or sub depression has its own depocentre mainly occupied by source rock and all kinds of lacustrine sediments and thus has all the essential elements of a petroleum system however only those depressions or sub depressions which are rich in organic matter and deeply buried to generate oil and gas form petroleum systems immature oil another characteristic complicates the petroleum system in the rift basins three types of oil and gas habitats are described as a result of this analysis of the petroleum systems of the 26 largest oil and gas fields discovered in eastern china rift basins uplifts between oil source centres are the most prospective areas for oil and gas accumulations slopes connecting oil source centres and uplifts are the second and the third type is subtle traps in the oil source centre