hydrocarbon generation and expulsion characteristics of the source rocks in the third member of the upper triassic xujiahe formation and its effect on conventional and unconventional hydrocarbon resource potential in the sichuan basin abstract the third member of the upper triassic xujiahe formation t3x3 is a typical source reservoir cap unit for natural gas exploration in the sichuan basin however most previous studies mainly focused on the t3x3 as a source rock ignoring its role as a reservoir as a result the evaluation of hydrocarbon resource potential was not accurate this study established a hydrocarbon generation and expulsion model through analyzing the geological and geochemical characteristics of the t3x3 source rocks and calculated the resource potential of conventional gas tight gas and shale gas systematically with combining the lower boundary of buoyancy dominated accumulation lbba the results indicated that the thickness of the source rocks dominated by mudstone was distributed widely with an average value of more than 45 m the sedimentary environment was salty lacustrine deposits they have a high content of total organic carbon toc with an average value of 4 80 wt the kerogen is mainly type iii with minor type ii and the thermal evolution has entered the high to over mature stage the hydrocarbon generation threshold was determined to be 0 5 ro while the hydrocarbon expulsion threshold and the lbba were determined to be 0 83 ro and 1 12 ro respectively the efficiency of hydrocarbon expulsion was relatively high with an average of about 56 also the maximum hydrocarbon generation and expulsion intensity reached to 110 108 m3 km2 and 53 108 m3 km2 the amounts of hydrocarbon generation expulsion and residual associated with the t3x3 source rocks were 125 68 1012m3 70 38 1012m3 and 55 30 1012m3 respectively under the criterion condition of the lbba the conventional gas resource was 7 21 1010m3 the tight gas resource was 294 34 1010m3 and the shale gas resource was 2488 50 1010m3 it indicated good prospects for exploration

the circulation of the levantine intermediate water in the algerian basin markedly different scenarios have been proposed for the circulation of the levantine intermediate water liw in the southern part of the western mediterranean sea discrepancies result from the fact that large temperature and salinity values which characterize liw are encountered both in the vicinity of sardinia and off algeria thus it was assumed that the circulation of liw was divided into two major branches one northward along the sardinian continental slope and the other across the algerian basin being dissatisfied with such a branch image of the circulation we have put forth hypotheses millot 1985 1987 which now appear to be supported by the results of the mediprod 5 experiment conducted in june 1986 we propose a scheme for the circulation of liw in the algerian basin wherein a gravity flow is constrained by the topography around sardinia and is subjected to sporadic spreading toward the open basin due to erosion of this vein by mesoscale eddies therefore it seems admissible that no branch of liw flows off the algerian coast

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

nile damming as plausible cause of extinction and drop in abundance of deep sea shrimp in the western mediterranean over broad spatial scales abstract greatly increased retention of flow in nile river reservoirs was initiated in 1964 after completion of the aswan high dam which induced important oceanographic changes in the mediterranean sea including deep waters below a depth of 150 m based on an analysis of data series starting in the 1940s 1950s the giant red shrimp aristaeomorpha foliacea has become locally extinct off of the catalonian coasts and elsewhere in the northwestern mediterranean at depths of 400 900 m with a simultaneous and significant drop in the catches of red shrimp aristeus antennatus in the second half of the 1960s the extinction and sharp decline of deep shrimp populations off catalonian coast at ca 3200 km westwards from nile delta followed the 1964 drop in nile discharge with a delay of ca 3 5 yrs breakpoint analysis applied to data series the breakpoints detected in the second half of 1960s both in nile runoff and shrimps abundance were independent of climatic events in the study area e g changes in nao and occurred before the increase in fishing effort off catalonian coasts breakpoint in 1973 1974 the levantine intermediate water liw inhabited by a foliacea in the western basin had significant temperature t and salinity s increases in the 1950 1970 period and nile damming has contributed about 45 of the total s increase of western mediterranean deep water masses from the 1960s to the late 1990s skliris and lascaratos 2004 this had to increase for instance liw salinity at its formation site in the eastern mediterranean nile damming was probably a triggering factor for the extinction drop in abundance of deep sea shrimp off catalonian coasts

the barnett shale compositional fractionation associated with intraformational petroleum migration retention and expulsion abstract the marathon 1 mesquite well was drilled in hamilton county texas targeting the barnett shale with late oil window maturity combining a large suite of petrologic and high resolution organic geochemical analyses on 120 core samples we have been able to document qualitatively and quantitatively the effects of petroleum retention within and expulsion from five intervals within the barnett shale lithological heterogeneities control the composition and amount of retained fluids the sorption of oil by solid organic matter is important in all intervals applying empirical formulas we have been able to demonstrate not only that retention is primarily controlled by total organic carbon toc but also that the live or labile component rather than dead or inert carbon constitutes the most active sorptive sites additional retention in the micropores provided by biogenic microcrystalline quartz sponge spicules accounts for the sweet spot defined by an oil crossover in the 9 14 m 30 ft thick second interval the fluorescing oil occurring in the axial chamber of the sponge spicules and that sorbed on organic particles are together enriched in saturated hydrocarbons whereas the dispersed oil from the adjacent interval 3 is depleted in this compound class mass balance calculations reveal that short distance migration of petroleum into this reservoir interval second fractionates the generated oil into a higher quality oil by preferential retention in the order polar compounds aromatic hydrocarbons saturated hydrocarbons within the underlying organic matter and clay rich third interval source unit furthermore molecular fractionation i e a preferential expulsion of lower molecular weight hydrocarbons n alkanes could be calculated an additional practical result for source rock assessment is that corrected s2 petroleum generated by pyrolysis and toc values should be calculated by combining rock eval pyrolysis data on whole rocks and rocks following soxhlet extraction using parameters based on unextracted rock only the expulsion of petroleum is systematically overestimated and the degree of kerogen conversion is therefore concomitantly underestimated

enrichment and distribution of shale oil in the cretaceous qingshankou formation songliao basin northeast china abstract the songliao basin is a large scale petroliferous basin in china with a gradual decline in conventional oil production the exploration and development of replacement resources in the basin is becoming increasingly important previous studies have shown that the cretaceous qingshankou formation k2qn has favorable geological conditions for the formation of shale oil thus shale oil in the qingshankou formation represents a promising and practical replacement resource for conventional oil in this study geological field surveys core observation sample tests and the analysis of well logs were applied to study the geochemical and reservoir characteristics of shales identify shale oil beds build shale oil enrichment models and classify favorable exploration areas of shale oil from the cretaceous qingshankou formation the organic matter content is high in shales from the first member of the cretaceous qingshankou formation k2qn1 with average total organic carbon toc content exceeding 2 the organic matter is mainly derived from lower aquatic organisms in a reducing brackish to fresh water environment resulting in mostly type i kerogen the vitrinite reflectance ro and the temperature at which the maximum is release of hydrocarbons from cracking of kerogen occurred during pyrolysis tmax respectively range from 0 5 to 1 1 and from 430 c to 450 c indicating that the k2qn1 shales are in the low mature to mature stage ro ranges from 0 5 to 1 2 and currently generating a large amount of oil the favorable depth for oil generation and expulsion is 1800 2200 m and 1900 2500 m respectively as determined by basin modeling the reserving space of the k2qn1 shale oil includes micropores and mircofractures the micropore reservoirs are developed in shales interbedded with siltstones exhibiting high gamma ray gr high resistivity rt low density den and slightly abnormal spontaneous potential sp in the well logging curves the microfracture reservoirs are mainly thick shales with high rt high ac acoustic transit time high gr low den and abnormal sp based on the shale distribution geochemical characteristics reservoir types fracture development and the process of shale oil generation and enrichment the southern taikang and northern da an are classified as two favorable shale oil exploration areas in the songliao basin

analysis of the charging process of the lacustrine tight oil reservoir in the triassic chang 6 member in the southwest ordos basin china with the success of bakken tight oil tight sandstone oil and shale oil and eagle ford tight oil in north america tight oil has become a research focus in petroleum geology in china tight oil reservoirs are predominantly distributed in lacustrine basins the triassic chang 6 member is the main production layer of tight oil in the ordos basin in which the episodes timing and drive of tight oil charging have been analyzed through the petrography fluorescence micro spectrometry micro thermometry and trapping pressure simulations of fluid inclusions in the reservoir beds several conclusions have been reached in this paper first aqueous inclusions with five peaks of homogenization temperatures and oil inclusions with three peaks of homogenization temperatures occurred in the chang 6 reservoir beds the oil inclusions are mostly distributed in fractures that cut across and occur within the quartz grains in the quartz overgrowth and calcite cements and the fractures that occur within the feldspar

some aspects of the organic geochemistry of petroleum fluids the most important influences on the compositions of petroleum fluids are in many cases the composition of a petroleum sample may allow the depositional environment of its source rock and its temperature history before and after expulsion to be determined this information assists the search for more petroleum in a region we suggest that this approach should be used more frequently to validate models of petroleum generation and migration in the second part of the paper we discuss the origin and nature of the differences in petroleum composition which are frequently found within individual petroleum reservoirs petroleum accumulations in permeable reservoirs are normally found to be inmechanical equilibrium and verticalchemical equilibrium this is manifested by constant subsurface fluid density at any given depth across the accumulation and increases in subsurface density with depth known as gravitational segregation however even in permeable reservoirs lateral differences in composition inherited from the reservoir filling process are not totally eliminated by mixing processes such as diffusion and convection thus lateral chemical equilibrium is often not achieved and lateral compositional variations are observed in present day oil and gas reservoirs these observations are justified in terms of order of magnitude estimates for the rates at which reservoirwide mixing occurs a case history is presented

geochemical effects of primary migration of petroleum in kimmeridge source rocks from brae field area north sea ii molecular composition of alkylated naphthalenes phenanthrenes benzo and dibenzothiophenes abstract variations with depth in the quantitative distributions of di and tricyclic alkylaromatic hydrocarbons and sulfur heterocycles determined for a total of thirty two core samples from two thick shale intervals and thirteen thin interbedded shale layers of the upper jurassic age kimmeridge clay formation brae field area north sea reveal in part the effects of depletion with hydrocarbon expulsion trends of increasing depletion with approach to the nearest shale sandstone contacts as documented by a decrease in carbon normalized yields are more distinctive for the alkylnaphthalenes as compared to the alkylphenanthrenes and alkyldibenzothiophenes but less drastic than previously observed for long chain alkanes cf part i leythaeuser et al 1988 lowest yields consistently were encountered at the outermost 1 2 metres of the thick shale intervals and for the thin shale layers where the relative expulsion efficiencies were much higher for c15 to c30n alkanes 80 95 than for c2 and c3 alkylnaphthalenes 30 40 in contrast c2 and c3 alkylbenzothiophene yields were higher in these shale portions than further inside the thick shale which is interpreted to result from a post expulsion selective replenishment from the adjacent oil accumulation expulsion was not associated with any detectable fractionation among c1 and c3 alkylnaphthalenes or c1 and c2 alkylphenanthrenes as evidenced by a mass balance approach and concentration ratios of individual alkylaromatic isomers commonly used as maturity indicators based on a reconstruction of the quantitative distributions of aromatic hydrocarbons and sulfur aromatics expelled from thin shale layers from early mature through to mature stages of thermal evolution it was verified that the methylphenanthrene index mpi 1 and methyldibenzothiophene ratio mdr of the expelled oil reflects the average of the maturity levels during which the source rock has expelled petroleum

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

comparison of three series of organic matter of continental origin abstract three series of sediments containing land plant derived organic matter were studied they include wells from mahakam delta indonesia miocene douala basin cameroon upper cretaceous and eastern paris basin france paleozoic all of the kerogens and coals isolated from these series can be related to type iii in a van krevelen diagram however they obviously differ in terms of chemical structure as reflected by their pyrolysis gc patterns and by their bitumen composition these observations indicate the variations in the nature of land plant derived sedimentary organic matter and thus differences in quantity and composition of the hydrocarbons which are are released upon maturation based on hydrocarbons potential of the insoluble organic matter and on pyrolysis gc there is no reason to disregard coals and to favor shales as potential source rocks in these two deltaic sequences moreover we assume that the bitumen depletion in coal samples is a reflection of loss by migration which is favored in coals when compared to shales the gc patterns of the residual saturates compared to the pyrolysis gc patterns of the related insoluble coals suggest that migration of hydrocarbons proceeds in these coals without any significant alteration of their distribution at least in the c15 range

kinetic modelling of petroleum formation and cracking implications from the high pressure high temperature elgin field uk north sea in this paper we use a case study to test the simulation of generation migration and cracking of petroleum fluids by a 2d compositional basin simulator using kinetic models based on chemical classes of compounds the selected area is the high pressure 1100 bar high temperature 190 c elgin field in the north sea this study is mainly focused on kinetic modelling of secondary cracking because in this zone paraffinic condensates with almost 50 c6 alkanes were recently discovered whereas only gas c5 was expected given the high temperature conditions the detailed hydrocarbon composition observed today in the fulmar sands reservoir of the elgin field is compared with the results of several simulations aimed at testing the influence of jurassic source rocks retention properties kinetic parameters and temperature variations on the predicted composition of fluids the influence of pressure was neglected in the modelling on the basis of results published in the literature results show that in this north sea area primary cracking of the kerogen into oil is completed whichever source rock is considered and that secondary cracking of accumulated petroleum compounds in the reservoir is presently in progress under these conditions source rock type and retention during primary and secondary migration have little influence on the present oil composition the occurrence of a monophasic paraffinic fluid in the elgin reservoir despite the high temperature is due to its very recent increase from 160 c to over 180 c in the last million years the fluid composition evolves rapidly and our compositional kinetic scheme accounts correctly for the presence of c6 hydrocarbons in these geological conditions first results using the compositional kinetic scheme of behar et al behar f kressman s rudkiewicz j l vandenbroucke m 1991 experimental simulation in a confined system and kinetic modelling of kerogen and oil cracking organic geochemistry 19 1 3 173 189 for secondary cracking showed a reasonably good fit between calculated and observed detailed fluid composition except for methylated aromatics which are overestimated and methane which is underestimated a recent comparison of kinetic parameters obtained from pyrolysis experiments on model compounds showed that it is not realistic to assume as done previously the same frequency factor for all chemical classes of compounds the higher stability of methylated aromatics relative to saturates observed under laboratory conditions would be extended to geological conditions a second set of simulations using frequency factors and activation energies obtained on these model compounds gave a better fit for methylated aromatics however methane is still strongly underestimated and reasons which could explain this discrepancy are discussed

relationship between the fluorescence color of oil inclusions and thermal maturity in the dongying depression bohai bay basin china part 1 fluorescence evolution of oil in the context of hydrous pyrolysis experiments with increasing maturity abstract the fluorescence evolution of oils has been measured by simulation of petroleum generation and expulsion in a half closed system using hydrous pyrolysis based on four oil prone source rocks type i and ii kerogens from the dongying depression bohai bay basin china the results suggest that the fluorescence characteristics of expelled oil are independent of oil prone kerogen types but are strongly related to oil generation and expulsion processes which are controlled by thermal maturity of source rocks the fluorescence spectral parameters max q650 500 and qf 535 of expelled oils show no obvious variation or even show gradual redshifts when the highest max occurs at peak bitumen generation depending on the expulsion process a blueshift of fluorescence color occurs only during the main oil generation and expulsion stage which immediately follows the peak bitumen generation stage however the expelled oil mainly exhibits green to yellow fluorescence colors 500 nm

millennial to centennial scale climate periodicities and forcing mechanisms in the westernmost mediterranean for the past 20 000 yr abstract cyclostratigraphic analysis conducted on a continuous high resolution marine record from the western most mediterranean reveals well identified paleoclimate cycles for the last 20 000 yr the detrital proxies used si al ti al zr al mg al k al rb al are related to different sediment transport mechanisms including eolian dust and fluvial runoff which involve fluctuations in the atmosphere hydrosphere systems these fluctuations are accompanied by changes in marine productivity supported by ba al and bottom water redox conditions cu al v al zn al fe al mn al u th spectral analysis conducted using the lomb scargle periodogram and the achieved significance level implemented with the permutation test allowed us to establish major periodicities at 1300 1515 2000 and 5000 yr and secondary peaks at 650 1087 and 3000 yr some of these cycles also agree with those previously described in the north atlantic ocean and circum mediterranean records the periodicities obtained at 2000 and 5000 yr support a global connection with records distributed at high mid and low latitudes associated with solar activity monsoonal regime and orbital forcing the 1300 and 1515 yr cycles appear to be linked with north atlantic climate variability and the african monsoon system thus the analyzed record provides evidence of climate cycles and plausible forcing mechanisms coupled with ocean atmosphere fluctuations

recent changes in deep water formation and spreading in the eastern mediterranean sea a review abstract observations of the last decade testify that the characteristics of the deep thermohaline circulation in the eastern mediterranean sea have changed thoroughly the source of the most dense waters of the basin has moved from the adriatic to the aegean sea this new source has proved to be very efficient since the estimated formation rate for the period 1989 95 was more than 1 sv about three times more than the dense water formation rate of the adriatic sea these new waters with hydrological characteristics that are warmer and more saline have replaced almost 20 of the older deep waters of the basin and have uplifted the deep isopycnals by about 500 m this major event can be attributed to important meteorological anomalies in the eastern mediterranean and to changes of circulation patterns the extended dry period of 1988 93 and the exceptionally cold winters of 1987 and 1992 93 created favorable conditions for increased formation of dense water in the aegean furthermore changes in the circulation patterns in the intermediate water range levantine intermediate water liw and cretan intermediate water themselves possibly linked to meteorological anomalies appear to have played an important role in the redistribution of salt as a result of an interruption to exchanges between the ionian and levantine basin the salinities in the latter started to rise high salinity waters were diverted into the aegean malanotte rizzoli p manca b b ribera dacala m theocharis a 1998 the eastern mediterranean in the 80s and in the 90s the big transition emerged from the poem bc observational evidence rapport du commission international de la mer medittanee 35 174 175 and the westward transport of liw was reduced an additional effect of the deep water discharge from the aegean and the resulting uplifting of mid depth waters was to lower salinities in the liw layer this effect is most strongly felt in the ionian sea a 3 d primitive equation numerical model for the eastern mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient these results indicate that the observed changes can be at least partially explained as a response of the eastern mediterranean and more specifically of the aegean to atmospheric forcing variability

the western mediterranean deep water a proxy for climate change reconstructions of mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the north atlantic and the western mediterranean deep water wmdw formed in the gulf of lions in winter because of consistent air sea heat fluxes over these areas strongly correlated to the north atlantic oscillation nao

interaction of coal and oil in confined pyrolysis experiments insight from the yields and carbon isotopes of gas and liquid hydrocarbons abstract isothermal confined gold capsule pyrolysis experiments were performed for coal alone oil alone and coal plus oil with oil coal ratios ranging from 0 006 to 0 171 at 315 c 345 c and 375 c respectively and 50 mpa for 72 h in the experiment for coal plus oil the amounts and compositions of hydrocarbon gases are substantially different from those predicted from the results in the experiments for oil alone and coal alone the results of these experiments demonstrate that kerogen and oil do not crack separately in the experiments of coal plus oil the interaction between kerogen and oil components leads to the generation of hydrocarbon gases with oil coal ratio increasing the amounts of individual and total hydrocarbon gases decrease at first and then increase rapidly up to several times those calculated from the yields of these components in the experiments for oil alone and coal alone the c1 c1 5 ratios of hydrocarbon gases decrease and are increasingly lower than those calculated from the yields of hydrocarbon gases in the experiments for oil alone and coal alone the amount and carbon isotopes of individual n alkane demonstrate that the free liquid n alkanes were incorporated into kerogen and replaced the bound liquid n alkanes covalently bonded alkyl groups in kerogen carbon isotopes of hydrocarbon gases further suggest that the bound liquid n alkanes in kerogen preferentially crack into hydrocarbon gases

petroleum secondary migration and accumulation in the central junggar basin northwest china insights from basin modeling the timing of petroleum generation migration and accumulation in the central junggar basin has been evaluated using basin modeling technology to decipher the processes of petroleum secondary migration and accumulation in the jurassic carrier beds during the yanshan and himalayan orogenies during the early yanshan orogeny j2 j3 crude oils sourced mainly from the permian source rocks migrated laterally from depocenters to adjacent structural high points during the late yanshan orogeny cretaceous eocene the hydrocarbon secondary migration pattern changed significantly specifically in the cretaceous a large scale regional second phase of generation and migration occurred in the western part of the central junggar basin in the eastern part of the central junggar basin crude oils emplaced in the depressions migrated mainly to the eastern uplifts in the early tertiary oils in the source kitchens generally began migrating to the north and mixed with the jurassic generated hydrocarbons during the himalayan orogeny neogene quaternary this migration was strengthened continually the modeled results agree with migration associated geochemical information of the jurassic accumulations integration of the regional geological setting and some petroleum geology data suggest that the jurassic tectonic high points and facies change and unconformity associated subtle traps are of crucial importance for current oil exploration both overpressured bodies in the triassic and permian systems and volcanic rock reservoirs of the carboniferous basement in the uplifts have important implications for future natural oil and gas exploration this work should help reduce exploration risk in this region

proterozoic source rocks sedimentology and organic characteristics of the velkerri formation northern territory australia the velkerri formation 1 43 ga in northern australia is one of the organically richest pro terozoic successions in australia and over the last 10 yr has been a target for oil exploration this formation is predominantly a glauconitic marine shale deposited in restricted to anoxic conditions in a deep water pro delta slope to basin environment the velkerri formation is composed of superimposed sediment couplets made up of laminated black organic rich mud shales total organic carbon toc 4 6 and laminated gray green organically lean mud shales toc 2 the couplets stack at scales ranging from centimeters to meters of particular interest are three black organic rich mud shales in the middle velkerri member tens of meters thick and correlatable over much of the drilled area of the basin their high organic contents reflect changes in organic productivity vs the rate of sediment supply and not fluctuating oxygen levels in the bottom waters or changes in water depth extractability and rock eval data show more efficient expulsion of hydrocarbons from the upper two of the three organic rich units in the middle velkerri evidence also exists for local intraformational migration of hydrocarbons into siltstone layers nevertheless the middle velkerri has very low permeability and porosity and still retains a significant fraction of its generated hydrocarbons especially in the lower portions of the middle velkerri where a volcanogenic provenance led to the early blocking of pore throats by clay diagenesis during early burial this study emphasizes the high quality of middle proterozoic source rocks for petroleum exploration in northern australia the main problem is finding traps that can preserve hydrocarbons over the long periods of time since the rocks became charged with hydrocarbons

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

geochemical effects of primary migration of petroleum in kimmeridge source rocks from brae field area north sea i gross composition of c15 soluble organic matter and molecular composition of c15 saturated hydrocarbons in mature oil prone source rocks of the upper jurassic kimmeridge clay in the brae field area north sea the yield and the gross composition of solvent extractabte pctroleum likc compounds as well as the molecular proportions of c15 saturated hydrocarbons are primarily controlled by the effects of hydrocarbon expulsion during primary migration within sample series extending from shale centres towards adjacent reservoir sandstones regular and pronounced yield decreases have been documented as well as marked compositional changes for c15 soluble organic matter and its compound class fractions saturated hydrocarbons aromatic hydrocarbons nso compounds and for normal and isoprenoid alkanes relative migration losses indicating relative expulsion efficiencies were determined for the c15 alkanes throughout the outer five meters of thick shales relative expulsion efficiencies increase regularly and drastically for all compounds considered e g exceeding 90 for the c15 n alkanes in the outermost shale samples samples from thin 5 50 cm shale layers interbedded between reservoir sandstones reveal similarly high expulsion efficiencies for n alkanes the degree of depletion remains uniform throughout the molecular range c15 to c30i e no compositional fractionation occurred during primary migration which is interpreted to reflect expulsion of oil as a single phase fluid a simple conceptual model is proposed to explain the mechanisms and relationships of generation and expulsion processes in time and space a geochemically relevant conclusion is that the c15 soluble organic matter recovered by solvent extraction of mature source rocks represents only a portion of the total non volatile petroleum like material originally generated

organic geochemistry of carboniferous source rocks and their generated oils from the eastern junggar basin nw china abstract carboniferous source rocks have been gaining increasing attention after the discovery of the kelameili gasfield in the eastern junggar basin in 2005 two sets of source rocks within the lower carboniferous dishuiquan formation c 1d and upper carboniferous batamayineishan formation c 2b respectively have been identified in this area in this paper clear differences between these two source rocks are demonstrated in molecular and carbon isotopic compositions the c 1d source rocks in comparison with the c 2b source rocks have remarkably lower pr n c 17 ratio higher ts ts tm and c 30 diahopane c 30 diahopane c 30 hopane ratios lower concentration of c 24 tetracyclic terpane relative to c 23 and c 26 tricyclic terpanes and higher gammacerane c 31 hopane ratio 13 c values of individual n alkanes decrease with carbon number for c 1d source rocks while the opposite is true for c 2b source rocks among the 10 oils collected from the studied area four were generated exclusively from c 1d source rocks while the others were mainly derived from c 1d source rocks but contaminated by a small or trace amount of oil components which were derived from the c 2b middle permian pingdiquan formation p 2p and lower jurassic source rocks the free adsorbed and inclusion oils from three oil containing volcanic reservoir rocks within the c 2b formation generally correlate with c 1d source rocks based on molecular and carbon isotopic data however the three types of oil from the same reservoir rock vary significantly in molecular and carbon isotopic compositions reflecting facies and maturity changes of charging oil during the reservoir filling

primary migration behaviour of hydrocarbons from laboratory experiments to geological situations through fluid flow models abstract primary migration is a complex process involving coupled fluid generation and mass transfer in low permeable rocks joint experimental and modelling work have been performed in order to better understand this problem eventually experimental results have been modelled and extrapolated to geological conditions maturation and expulsion experiments have been carried out with water saturated immature type ii source rocks from the paris basin with sample weights up to 3 kg temperatures were stepwise increased from 20 c to 285 330 or 380 c at constant hydrostatic pressures of respectively 17 or 55 mpa during up to 5000 h during the experiments generated fluids expelled out of the heating cell and were sampled prior to a complete analysis mass balances were checked on hydrocarbon gases liquid hydrocarbons co 2 and water meanwhile closed system pyrolysis experiments were performed on isolated kerogen extracted from the same source rocks they allowed us to derive a compositional kinetic cracking reaction network it was then possible to tackle the expulsion of fluids out of the source rock the kinetic scheme provides a guideline to understand the generation of fluids from kerogen the expulsion experiments provide an insight into the expulsion mechanisms no axial stress has been applied to the samples in the experiments therefore the influence of rock compaction due to effective stress was not studied in these experiments a numerical model of expulsion has been set up based on volume and mass balance conservation equations in the source rock the volume is assumed to vary as solid kerogen transforms to liquid products and solid residue the mass of each compound is kept in balance as it is created or destroyed through primary and secondary cracking and expelled through multiphase fluid flow therefore depending on pressure temperature and composition fluids in the source rock are split into several phases following a thermodynamical equation of state all mobile phases flow according to darcy s law experiments were modelled the best fit being achieved with the following conditions all fluids including water co 2 and hydrocarbons are allowed to form a multiphase mixture the heavy compounds resins and asphaltenes are in a single very viscous phase and are less easily expelled as most of them are cracked inside the source rock extrapolations to geological pressure and temperature conditions were performed afterwards in order to check the phase behaviour and the expulsion efficiency

petroleum migration faults and overpressure part ii case history the haltenbanken petroleum province offshore norway abstract petroleum inclusion and geochemical data from core extracts were applied to deduce a model for oil migration overpressure development and palaeo leakage of oil from currently dry structures in the haltenbanken vest area the existence of fluorescent oil type inclusions in quartz in the smorbukk asgard 2 field suggest that oil migrated into this structure 70 50 million years before present ma bp this is also the case for the dry structures 6506 12 4 6506 11 3 and 6506 11 1 west of the main smorbukk fault zone black oil inclusions with medium gas oil ratio gor occur in these fields together with condensate type petroleum inclusions this suggests that the dry structures transformed from containing oil to condensate before leakage petroleum extracted from inclusions in these structures and in nearby fields have identical marine type ii kerogen signatures source rocks at the spekk formation level in the current drainage area of smorbukk and these dry structures were immature 70 50 ma bp and the smorbukk sor asgard 3 field did not fill at this early time thus oil must initially have entered into smorbukk from areas to the w sw through the currently pressure sealing smorbukk fault zone which today marks the westward limit of the smorbukk field diagenesis in this fault zone caused the much later overpressure development and petroleum was lost from the 6506 12 4 6506 11 3 and 6506 11 1 structures as overpressure built up regionally petroleum loss from these structures with their often thick seals must have occurred via self propagating open fracture induced mechanisms lack of petroleum in the cretaceous strata above these structures suggests that leakage occurred to even shallower strata this could imply that the cretaceous strata in halten vest were overpressured at the time of leakage in contrast the oil in the cretaceous lysing and lange formation above the jurassic reservoirs in smorbukk and smorbukk sor most likely originated based on geochemistry and gors from the jurassic reservoirs below and not from cretaceous strata this migration event would have been facilitated if it occurred before these sands became overpressured as they are today modelling suggests that the spekk formation became mature in the smorbukk sor region

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

temporal evolution of the water mass properties during the eastern mediterranean transient emt in the aegean sea 1 we present time series of temperature and salinity of the aegean sea using the data sets for the period from 1991 to 1996 from 15 oceanographic cruises to depict the temporal variability of the water masses of the aegean sea this period covers an interesting large scale change in the thermohaline circulation in the eastern mediterranean and the aegean sea this change is known as the eastern mediterranean transient emt and was first described during early 1990s our analysis reveals that very dense water formation in the central aegean sea is partially due to the anomalous decrease in winter atmospheric temperature although this alone cannot completely account for the formation of the dense water a synchronous increase in surface salinity accompanied by low temperature values in the winter months is also necessary for the emt event to occur

migration of c1 c8 hydrocarbons in marine sediments abstract light hydrocarbon c 1 c 8 profiles are compared for three wells of varying maturities two immature dsdp wells site 397 near the canary islands and site 530a near the walvis ridge in the south east atlantic and a mature well the east cameron well in the texas gulf coast primary migration of c 1 and c 2 appears to be occurring in all of the sedimentary rocks examined primary migration of c 3 components becomes important only as fine grained sedimentary rocks enter the catagenetic hydrocarbon generation zone or over short distances in more permeable sections lateral migration along bedding planes was more important than vertical migration in sedimentary rocks of all maturities the lightest methane ethane and propane gases hydrocarbon show greater fractionation than do the c 4 c 8 alkanes which generally show minimal fractionation during the migrational process subsurface diffusion coefficients for these p p b quantities of c 2 c 5 alkanes from immature sediments from dsdp site 530 are estimated to be several orders of magnitude less than values reported in the literature for diffusion of much larger amounts of these compounds from mature water wet sediments into air or sandstones since our calculations suggest light hydrocarbons are present in amounts less than their reported solubilities in pure water at 25 c we postulate that the sediment organic matter has a substantial effect on retarding the movement of these light hydrocarbons

petroleum generation kinetics for permian lacustrine source rocks in the junggar basin nw china abstract the junggar basin is a major oil producing province in china most of the oil originated from permian lacustrine oil prone source rocks in the basin kinetic parameters for oil and gas generation were obtained from confined pyrolysis experiments using gold capsules at heating rates of 20 c h and 2 c h on kerogen samples from two permian lacustrine oil prone source rocks j23s3 and ss1s3 having hydrogen indices of 663 and 698 mg hc g toc respectively the kinetic properties for oil and gas generation vary substantially between these two source rocks assuming a burial heating rate of 5 c my the temperature for 50 transformation ratio to oil is 132 c for j23s3 and 168 c for ss1s3 the maximum oil yields are about 604 and 770 mg g toc while the maximum yields of total gaseous hydrocarbons are about 306 and 348 mg g toc for j23s3 and ss1s3 respectively gaseous hydrocarbons from the confined pyrolysis experiments include primary cracking components from kerogen and secondary cracking components from the generated oil the secondary cracking gaseous hydrocarbons comprise up to 84 9 and 95 1 of the total respectively for the two source rocks in the highest temperature experiments a practical method estimates the amount of gaseous hydrocarbons generated from these source rocks under geological conditions based on 1 kinetic parameters for gas generation obtained from kerogen confined pyrolysis experiments in the present study 2 the maximum yield of gaseous hydrocarbons from oil confined pyrolysis experiments from previous studies and 3 the maximum amount of expelled oil the maximum amounts of expelled oil range from 509 588 and 724 750 mg g toc with oil expulsion efficiencies in the ranges 84 3 97 4 and 94 0 97 4 for j23s3 and ss1s3 respectively assuming that the amounts of retained oil range from 30 160 and 50 110 mg g toc for the two source rocks after oil expulsion based on the amounts of extracted bitumen consequently the maximum yields of total gaseous hydrocarbons could be in the ranges 53 1 87 0 and 25 5 36 8 mg g toc respectively for j23s3 and ss1s3 in nature using the kinetic parameters for these two source rocks determined from pyrolysis experiments oil and gas generation and expulsion were modeled for source rocks within the lower permian fengcheng p 1f and middle permian lower wuerhe formations p 2w in the central area of the mahu depression the source kitchen for most oilfields in the basin

the factors controlling the abundance and migration of heavy versus light oils as constrained by data from the gulf of suez part i the effect of expelled petroleum composition pvt properties and petroleum system geometry abstract in the gulf of suez gos petroleum systems the main factors which control the abundance and migration of heavy vs light oils are a the composition and pvt properties of the expelled fluids b the geometry of the petroleum systems and c reservoir flow processes compositional and pvt modeling of the expelled petroleum fluids from the brown limestone and the thebes formation carbonate source rocks show the following the fluids expelled below a transformation ratio of 0 5 are heavy oils stock tank api gravity 10 20 have a low gor and contain 20 25 asphaltenes these fluids are formed from source rocks which have mainly low to intermediate sulfur content and normal thermal stability the further expelled fluids up to a transformation ratio of around 0 97 are bubble point behaving fluids oils with stock tank api from 20 50 and gor 300 800 scf bbl and display a progressive decrease in asphaltene content the latest 3 expelled fluids represent dew point behaving fluids gas condensates the heavy low gor oils expelled below a transformation ratio of 0 5 have a very low saturation pressure and are not prone to asphaltene precipitation unless they are mixed with higher gor fluids the pvt properties of these early expelled oils permit their efficient migration this is consistent with an overabundance of low maturity asphaltenes in the gos discovered heavy oils the tendency for asphaltene precipitation is increased for the fluids expelled above a transformation ratio of 0 5 due to both a decrease in their asphaltene content and an increase in gor geometrically imposed mixing of fluids with large maturity induced compositional differences and reservoir flow processes have a significant effect on the pvt behavior of the migrating fluids on asphaltene precipitation and on the distribution of heavy vs light oils

experimental investigation of oil generation retention and expulsion within type ii kerogen dominated marine shales insights from gold tube nonhydrous pyrolysis of barnett and woodford shales using miniature core plugs abstract although oil retention has recently emerged as a key topic of unconventional shale resource assessment oil retention and expulsion controls in organic rich shales during thermal maturation remain poorly constrained this study presents an experimental comparison of oil generation retention and expulsion in two immature type ii kerogen dominated marine shales the mississippian barnett shale and the upper devonian lower mississippian woodford shale mainly with respect to the combined effects of the organic macerals and rock fabric involved in both cases miniature core plugs drilled from the given samples were isothermally pyrolyzed at 130 to 425 c for 72 h under a confining pressure of 68 mpa during gold tube nonhydrous pyrolysis corresponding to the thermally immature early stage of the oil window the main stage of the oil window the late stage of the oil window the main stage of oil cracking to wet gas and the late stage of oil cracking yields of generated oil retained oil and expelled oil for the two studied samples were systematically quantified on the basis of mass balance calculation of measured oil and gas yields as well as rock eval analyses on pyrolyzed subsamples through the six stages of petroleum formation investigated the principal difference in oil generation was observed in the two studied samples with approximately 38 to 68 greater yields of generated oil equivalent to 130 mg oil g toco for the woodford shale when it evolved into the main and late stages of the oil window these elevated yields of generated oil for the woodford shale were compensated for by additional oil generation resulting from conversion of abundant type i kerogen like algae such as tasmanites and leiosphaeridia which lag in onset and have a shorter period of petroleum generation upon maturation as a response to the difference in oil generation oil retention was found to be significantly enhanced for the woodford shale at equivalent stages with 0 2 to 1 7 times more free oil equivalent to 24 105 mg oil g toco and 0 7 to 3 9 times more sorbed oil equivalent to 58 76 mg oil g toco being retained than that of the barnett shale although this effect was not pronounced for oil expulsion in contrast to the barnett shale relatively low expelled oil yields and expulsion efficiencies both indicate highly limited oil expulsion in the woodford shale implying that the woodford shale whose mineral composition and lithofacies are similar to those of the barnett shale may have a relatively low permeability rock fabric to prevent oil from being expelled furthermore not only significantly higher oil saturation index osi values but also a wider range of maturity at which the oil crossover effect osi 100 mg g toc occurs is expected for the woodford shale when extrapolation to a geological setting occurs these data suggest that the presence of abundant type i kerogen like algae and relatively low permeability rock fabric in the woodford shale are critical to significant oil retention during oil generation and expulsion which jointly raise the possibility of potential commercial shale oil within type ii kerogen dominated marine shales

geophysical properties of cap rocks in qiongdongnan basin south china sea abstract based on measured petrophysical properties and statistical methods relationship between petrophysical properties and well log and seismic parameters are established empirically to evaluate the quality of cap rocks in qiongdongnan basin good cap rocks show high density and low sonic travel time four zones can be divided vertically according to displacement pressures in qiongdongnan basin best seal quality is found in the depth range of 2000 4000 m the ya 13 1 structure has excellent cap rock which contributes to its abundant gas accumulation

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

data calibrated migration modelling in the assessment of brent group prospectivity a case study from the veslefrikk area of the norwegian north viking graben abstract a study of the prospectivity around the veslefrikk oil field in block 30 3 of the norwegian north sea included an evaluation of petroleum migration and trapped gas to oil ratios the study followed a procedure which involved the assessment of source rock distribution and quality source rock maturity petroleum generation and expulsion and secondary migration inside a semi regional framework two prospects are discussed 1 b prospect a down faulted hanging wall trap to the west of the veslefrikk horst where the existing discoveries of veslefrikk oseberg east and zeta exist and 2 c prospect a tilted fault block foot wall trap to the south of the huldra discovery 1d thermal modelling coupled to map based petroleum migration analysis and 2d multi layer migration modelling were used in this multi source multi carrier setting to evaluate the petroleum system with the integration of available well and seismic data basin modelling techniques can deliver more confident assessments especially where multiple geological models may exist in this study area data such as temperatures and source rock properties were used to constrain the model input options thereby reducing parameter uncertainty other data such as geochemical fluid to source correlation and observed petroleum distribution and composition served as a validity check for the simulated results from different geological models the use of these data in this case history are discussed and illustrated

aspects of generation and migration of hydrocarbons from coal bearing strata of the hitra formation haltenbanken area offshore norway abstract the haltenbanken area situated 150 200 km offshore mid norway is a proven gas condensate and oil producing province with continuing exploration potential in this structurally and stratigraphically complex area with multiple source rock possibilities we have examined the upper triassic lower jurassic hitra formation to determine its possible contribution to the hydrocarbon pools in the area the 400 m thick hitra formation consists of interbedded shales siltstones sandstones and coal seams in this study conventional cores of the hitra formation from depths varying from 2 4 and 4 6 km have been examined with the objective to obtain a better understanding of hydrocarbon generation migration and expulsion processes in these coals as function of variation in facies and maturity in addition to basic geochemical measurements toc rock eval and gc analysis of c15 saturated hydrocarbons microscopic studies normal and uv reflected light were carried out to determine the abundance and initial distribution of hydrogen rich macerals including fluorescent mobile phases such as exsudatinities geochemical and microscopal evidence was obtained suggesting that some of the interbedded sandstones show indications of impregnation by migrated hydrocarbons some bitumen filled micro fractures were observed extending from the coals towards the adjacent sands a preliminary interpretation of these data is that these fractures represent conduits carrying hydrocarbons from the coal seams towards the sandstones the role of the kerogen type variations on the amount of hydrocarbons generated and the mechanism and efficiency of hydrocarbon expulsion from the coals is discussed

quantitative modelling of hydrocarbon expulsion and quality grading of tight oil lacustrine source rocks case study of qingshankou 1 member central depression southern songliao basin china the quality of source rocks plays an important role in the distribution of tight and conventional oil and gas resources despite voluminous studies on source rock hydrocarbon generation expulsion and overpressure a quality grading system based on hydrocarbon expulsion capacity is yet to be explored such a grading system is expected to be instrumental for tight oil and gas exploration and sweet spot prediction this study tackles the problem by examining late cretaceous lacustrine source rocks of the qingshankou 1 member in the southern songliao basin china by evaluating generated and residual hydrocarbon amounts of the source rock the extent of hydrocarbon expulsion is modelled through a mass balance method the overpressure is estimated using petromod software through correlation between the hydrocarbon expulsion and source rock evaluation parameters total organic carbon toc kerogen type vitrinite reflectance ro and overpressure three classes of high quality effective and ineffective source rocks are established high quality class contains toc 2 type i kerogen ro 1 0 overpressure 7mpa sharp increase of hydrocarbon expulsion along with increasing toc and overpressure and high expulsion value at ro 1 source rocks with toc and ro 0 8 type ii2 iii kerogen overpressure 3mpa and low hydrocarbon expulsion volume are considered ineffective rocks with parameters between the two are considered effective the high quality class shows a strong empirical control on the distribution of tight oil in the songliao basin this is followed by the effective source rock class the ineffective class has no measurable contribution to the tight oil reserves because the hydrocarbon expulsion efficiency of source rocks is controlled by many factors the lower limits of the evaluation parameters in different basins may vary however the classification method of tight source rocks proposed in this paper should be widely applicable

natural fracture cleat and strong adsorption impact on low oil and condensate retention in the carboniferous shales and coals of the western black sea basin of turkey total organic carbon toc values of the carboniferous shales and coals of the western black sea basin of turkey range from 0 72 to 71 52 wt with an average of 32 3 wt and generation potential chance from 0 33 to 184 64 with an average of 82 47 mg hc g rock hydrogen index hi values of the shales and coals range from 24 to 384 mg hc g toc the hi versus pyrolysis temperature at the maximum rate of kerogen conversion plot indicates that the organic matter is type ii iii the calculated vitrinite reflectance equivalent values of the shales and coals range from 0 63 to 1 32 thus the shales and coals of the carboniferous formations are represented by immature effective oil and condensate generation windows the shales and coals of the alacaagzi formation contain high quartz and lower clay oil saturation index osi values of the shales and coals have been calculated as being 0 7 and 12 mg hc g toc indicating possible lack of producible oil and condensate the osi values are lower than those of other coal bearing and marine shales of the world first strong adsorption capacity may be a cause of the lower oil and condensate retention second faults natural fractures and cleats related fluid flows may be important factors in these lower osi ratios the extensional collisional and inverse tectonic stages and diagenetic processes of coalification formed multiple interconnected faults natural opening mode fractures and cleats in the shales and coals thus 15 coalbed methane exploration wells failed to produce any economical coalbed methane