subsidence maturation and migration history of the tampen spur area abstract a complete study of the petroleum system of the tampen spur area has been carried out the approach used was a two dimensional temispack analysis of a seismic line crossing the area where various hypotheses could be tested and later applied in a three dimensional sense the profile crosses from the deepest part of the tampen graben across the visund ridge and the marflo ridge to the sogn graben in the east four source rocks have been taken into account two marine the draupne the most prolific and the heather and two deltaic the brent and the dunlin two different prospect types can be defined the brent at the top of the tilted blocks and heather sand bodies at the foot of the eroded tilted blocks various hypotheses about the geometry of these sand bodies and about the contact between the rich draupne source rocks and the sands have been tested maturation started in the middle cretaceous between 100 ma in the deepest eastern part of the section sogn graben and 80 ma for the draupne on the tampen spur west graben at this time the structures were already sealed by the cretaceous shales apart from the visund ridge all the prospects are currently in the condensate or gas window overpressures are compatible with large closed faults more data are required about the possible sealing of minor faults before any conclusions can be drawn there is no easy migration path from the rich draupne rocks to the brent reservoir and various hypotheses are discussed to explain the regional petroleum potential one possible explanation for the regional charge is the contribution of the other source rocks the heather the brent and the dunlin

comparative studies of the kinetic parameters of various algaenans and kerogens via open system pyrolyses abstract kinetic parameters were determined for the first time via open system pyrolyses on algaenans highly resistant biomacromolecules that are selectively preserved during kerogen formation isolated from extant microalgae parallel studies were also carried out on 10 kerogens exhibiting with one exception a low level of maturity these kerogens included samples chiefly derived from the selective preservation of the above algaenans and samples mainly or almost exclusively derived from the natural vulcanization pathway important differences in activation energy e a distributions were observed between the four algaenans investigated and correlated with their chemical structures the kerogens predominantly derived from algaenan selective preservation pula alginite ne 70 and bj 248 torbanites rundle oil shale also exhibited pronounced differences in e a distributions these distributions provided i information on the diversity of the source materials and ii reflected the occurrence of important differences in chemical structures and thermal behaviour between three of the tested kerogens even though they are all classified as low maturity type i the kimmeridge clay samples and the lorca oil shale showed broad e a distributions shifted to low energies when compared with the above algaenans and kerogens such shifts reflect an important or even almost exclusive for some of these kerogens contribution of materials originating from sulphur incorporation into various lipids during early diagenesis finally the kinetic data derived for the nine low maturity fossil samples were extrapolated to a very low geological heating rate of 3 c ma 1 and the generation rate curves and cumulative yield curves thus obtained were compared

some potential applications of pyrolysis to basin studies a variety of pyrolysis systems can be used to obtain source rock evaluation and other data systems with bulk flow capabilities are best used to screen samples for subsequent detailed analysis but data must be interpreted in the light of possible mineral pyrolysate interactions non indigenous hydrocarbons can be detected by the same techniques but pyrolysis fid gc or alternatively pyrolysis gc plus pyrolysis bulk flow are required to identify and differentiate migrated hydrocarbons and refined petroleum products screening can be carried out in the laboratory or at the well location in the latter case data can be used for on site decision making as well as providing the groundwork for subsequent geochemical studies pyrolysis fid gc provides the most comprehensive means for screening in both laboratory and well site situations for detailed geochemical analysis pyrolysis gc is the most versatile technique providing both quantitative and qualitative ways to identify kerogen type classify bitumens and recognize contamination

hydrocarbon generation and migration from jurassic source rocks in the e shetland basin and viking graben of the northern north sea in the e shetland basin oil generation began 65 ma ago peak oil generation maturity occurs today at 3250 m 0 7 r 0 and was first reached 40 50 ma ago the oil generation threshold is at 2500 m highest oil saturations in the kimmeridge clay occur at 0 8 r 0 oil expulsion efficiencies are 20 30 oil phase migration has probably occurred through oil wet kerogen laminae and through interconnected large pores aided by low oil water interfacial tensions oil migrated along strong lateral fluid pressure gradients from overpressured source rocks in half grabens to jurassic reservoirs in tilted fault blocks in the viking graben the kimmeridge clay is at oil floor maturity below 4500 m oil and peak oil generation began 7c 80 and 55 65 ma ago respectively 40 ma ago the kimmeridge clay passed through peak generation and gas generation by cracking of oil had begun peak dry gas generation from brent coals occurs today below 5000 m and began 40 ma ago the frigg field gas probably generated from late jurassic source rocks migrated through microfractures in overpressured mudstones below 3500 m above 3500 m methane probably migrated in aqueous solution and was exsolved in the early tertiary aquifer

assessment and zonation of regional crustal stability in and around the dam region of the three gorges project on the yangtze river the scale of the three georges project tgp on the yangtze river ensures that it will have enormous social and economic consequences determining the safety of the tgp is an essential consideration and conducting the assessment and zonation of regional crustal stability has a crucial role in determining the success or failure of the tgp in the future in this paper the assessment of regional crustal stability places much emphasis on tectonic stability and the stability of partial foundations rock and soil masses and surface slopes which include landslides collapses etc related to fracture activity is also taken into consideration the evaluation and zonation of regional crustal stability was conducted on two scales and scopes the dam region and the vicinity of the tgp about 310 000 km2 and the dam region of the tgp about 30 000 km2 on the basis of tectonic zonation and present crustal stress field analysis fuzzy mathematics was used to perform quantitative and comprehensive evaluations of crustal stability and then the zonation of crustal stability in the study region combined with a theoretical geological study was made the results of the assessment and zonation of the crustal stability can be summarized as follows 1 the general crustal stability of the dam region is in a less stable stable state and the sandouping dam site is on a relatively stable landmass and 2 the sandouping dam site is on an ancient integrated granite body belonging to a stable i landmass therefore from the view of assessment and zonation of regional crustal stability a large scale hydropower station can be constructed at sandouping

the importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs abstract the effect of shale composition and fabric upon pore structure and ch 4 sorption is investigated for potential shale gas reservoirs in the western canadian sedimentary basin wcsb devonian mississippian d m and jurassic shales have complex heterogeneous pore volume distributions as identified by low pressure co 2 and n 2 sorption and high pressure hg porosimetry thermally mature d m shales 1 6 2 5 vro have dubinin radushkevich d r co 2 micropore volumes ranging between 0 3 and 1 2 cc 100 g and n 2 bet surface areas of 5 31 m 2 g jurassic shales which are invariably of lower thermal maturity ranging from 0 9 to 1 3 vro than d m shales have smaller d r co 2 micropore volumes and n 2 bet surface areas typically in the range of 0 23 0 63 cc 100 g co 2 and 1 9 m 2 g n 2 high pressure ch 4 isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon toc content methane sorption in d m shales increases with increasing toc and micropore volume indicating that microporosity associated with the organic fraction is a primary control upon ch 4 sorption sorption capacities for jurassic shales however can be in part unrelated to micropore volume the large sorbed gas capacities of organic rich jurassic shales independent of surface area imply a portion of ch 4 is stored by solution in matrix bituminite solute ch 4 is not an important contributor to gas storage in d m shales structural transformation of d m organic matter has occurred during thermal diagenesis creating and or opening up microporosity onto which gas can sorb as such d m shales sorb more ch 4 per weight percent wt toc than jurassic shales inorganic material influences modal pore size total porosity and sorption characteristics of shales clay minerals are capable of sorbing gas to their internal structure the amount of which is dependent on clay type illite and montmorillonite have co 2 micropore volumes of 0 78 and 0 79 cc 100 g n 2 bet surface areas of 25 and 30 m 2 g and sorb 2 9 and 2 1 cc g of ch 4 respectively dry basis a reflection of microporosity between irregular surfaces of clay platelets and possibly related to the size of the clay crystals themselves mercury porosimetry analyses show that total porosities are larger in clay rich shales compared to silica rich shales due to open porosity associated with the aluminosilicate fraction clay rich sediments low si al ratios have unimodal pore size distributions

latest jurassic early cretaceous events and the late cimmerian unconformity in north sea area each of several regional or local unconformities may have been identified locally as the late cimmerian unconformity a supposed major break at the base of the valhall formation or roedby formation over most of the north sea the base of the valhall formation is isochronous and conformable with underlying sediments it is detected on seismic reflection profiles because it represents a widespread facies change marking the late ryazanian transgression most of the unconformities are of eustatic origin and the effects of eustatic sea level changes were never completely masked by local tectonics thus in the modeling of individual oil fields the possibility of sedimentary breaks occurring can be predicted in part by reference to regional or eustatic events modified journal abstract

characterization of organic matter fractions in an unconventional tight gas siltstone reservoir abstract this paper on core samples collected from the triassic montney formation tight gas reservoir in the western canadian sedimentary basin wcsb illustrates that operationally defined s1 and s2 hydrocarbon peaks from conventional rock eval analysis may not adequately characterize the organic constituents of unconventional reservoir rocks modification of the thermal recipe for rock eval analysis in conjunction with manual peak integration provides important information with significance for the evaluation of reservoir quality an adapted method of the analysis herein called the extended slow heating esh cycle was developed in which the heating rate was slowed to 10 c per minute over an extended temperature range from 150 to 650 c for montney core samples within the wet gas window this method provided quantitative distinctions between major organic matter om components of the rock we show that the traditional s1 and s2 peaks can now be quantitatively divided into three components s1 esh free light oil s2a esh fluid like hydrocarbon residue fhr and s2b esh residual carbon solid bitumen more refractory consolidated bitumen pyrobitumen the majority of the total organic carbon toc in the studied montney core samples consists of solid bitumen that represents a former liquid oil phase which migrated into the larger paleo intergranular pore spaces physicochemical changes to the oil led to the precipitation of asphaltene aggregates subsequent diagenetic and thermal cracking processes further consolidated these asphaltene aggregates into lumps of solid bitumen or pyrobitumen at higher thermal maturity solid bitumen obstructs porosity and hinders fluid flow and thus shows strong negative correlations with reservoir qualities such as porosity and pore throat size although the fhr fraction constitutes a small portion of the total rock mass and volume in montney samples it has important implications for reservoir quality this fraction represents a thin film of condensed heavy molecular hydrocarbon residue covering surfaces of the present time pore spaces and may represent the lighter component of the paleo oil that migrated into tight interstices in the montney reservoir the fhr fraction potentially plays an important role in wettability alteration by creating hydrophobic matrix pore networks in portions of the reservoir that were not already filled with solid bitumen

guidelines for assessing the petroleum potential of coaly source rocks using rock eval pyrolysis abstract coaly source rocks are sufficiently different from marine and lacustrine source rocks in their organic matter characteristics to warrant separate guidelines for their assessment using rock eval pyrolysis the rank threshold for oil generation is indicated by the increase in bi s1 toc at rank sr 9 10 tmax 420 430 c ro 0 55 0 6 and the threshold for oil expulsion is indicated by the peak in qi s1 s2 toc at rank sr 11 12 5 tmax 430 440 c ro 0 65 0 85 the pronounced rank related increase in hi s2 toc prior to oil expulsion renders the use of immature samples inappropriate for source rock characterisation a more realistic indication of the petroleum generative potential and oil expulsion efficiency of coaly source rocks can be gained from samples near the onset of expulsion alternatively effective hi values i e his near the onset of expulsion can be estimated by translating the measured his of immature samples along the maturation pathway defined by the new zealand or other defined coal band coaly source rocks comprise a continuum of coaly lithologies including coals shaly coals and coaly mudstones determination of the total genetic potential of coaly source rock sequences is best made using lithology based samples near the onset of expulsion

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

primary migration by diffusion through kerogen i model experiments with organic coated rocks abstract laboratory experiments were performed to assess diffusion through kerogen as a mechanism of hydrocarbon transport through fine grained rocks such transport can be important in primary migration within source rocks and in leakage through seals to test the concept of diffusion through organic matter networks model experiments were performed in which hydrocarbon diffusion was measured through austin chalk cores that had been coated with a monolayer of fatty acids hydrocarbon fluxes through the coated cores were compared to hydrocarbon fluxes through uncoated austin chalk cores results showed that the organic coating enhanced transport through the core by a hundredfold over diffusion through its water filled pore space alone

a study of the holzener asphaltkalk northern germany observations regarding the distribution composition and origin of organic matter in an exhumed petroleum reservoir abstract the holzener asphalkalk deposit is located on the southwestern flank of the hils syncline northern germany it consists of a series of kimmeridgian portlandian bitumen impregnated limestones cumulative thickness of nearly 200 m overlain unconformably by neocomian claystones and underlain by older jurassic and triassic sediments the most bitumen rich limestone layers have been extensively mined with the result that there is three dimensional access to what is probably an exhumed series of stacked petroleum reservoirs geochemical petrological and petrophysical techniques were used to gain some insight into the distribution and the source of the organic matter in two of the 13 layers of the deposit most disseminated organic matter was found to be soluble in organic solvents and rich in non hydrocarbons its distribution appears to be controlled by ooid versus carbonate matrix abundances the occurrence of fractures and degree of impregnation small meso to micro pores have high bitumen saturations whereas large pores meso to macro have much lower saturations mature petroleum is thought to have once filled all pores but alteration has probably removed as much as 85 of it mainly from the large pores regional geochemical considerations pyrolysis and stable carbon isotope data indicate that the original petroleum was most probably derived from the underlying posidonia shale toarcian source rock asphaltene pyrolysis data indicate that an algal lacustrine co source might have also contributed to the deposit

recognition and quantification of the effects of primary migration in a jurassic clastic source rock from the norwegian continental shelf a detailed quantitative geochemical study was made of a mature jurassic clastic source rock sequence in order to attempt to recognize and quantify petroleum migration effects two different quantitative approaches were followed to monitor primary migration effects on both the bitumen 1 e g whole rock extract and the bitumen 2 e g isolated kerogen extract fractions these methods were a comparisons of toc normalized extract yields and quantified molecular compositions of petroleums from both tightly carbonate cemented zones and those from less cemented zones and b comparison of petroleums from shale laminae vs those from interbedded siltstone laminae on this basis it was possible to assess apparent primary migration efficiency relative expulsion efficiencies in certain shale samples and relative import efficiencies in siltstone bands ranged from 11 total extract to 85 saturated hydrocarbons and individual n alkanes no carbon number dependent fractionation effects were observed for n alkanes of bitumen 1 in the c15 to c35 range i e expulsion efficiencies were independent of carbon number suggesting bulk oil flow with chromatographic modification as the predominant transport mechanism

prediction of petroleum formation the influence of laboratory heating rates on kinetic parameters and geological extrapolations while major variations in predictions of petroleum formation timing are supposed to be related to the burial history of the source rock and the type of organic matter preserved therein it is often ignored that the laboratory techniques used to obtain reliable kinetic parameters for the description of petroleum formation and its extrapolation to natural conditions can be problematic in the present paper bulk petroleum generation by open system programmed temperature pyrolysis of green river shale toarcian shale and westfalian coal samples has been studied comparatively at heating rates of 0 1 0 7 5 0 15 0 and 25 0 k min in order to evaluate the influence of laboratory heating rates on kinetic parameters and geological extrapolations kinetic parameters were calculated from three sets of pyrolytic generation rate versus temperature curves measured at either 0 1 0 7 and 5 0 0 7 5 0 and 15 0 or 5 0 15 0 and 25 0 k min using both the distributed and the tmax shift model frequency factors and dominant activation energies derived from the tmax shift model are found to decrease systematically in going from sets of slow to fast heating rates for type ii and iii kerogens this decrease of kinetic parameters is confirmed by the distributed model for algal kerogens of type i the distributed model cannot be applied the decrease of kinetic parameters results from increasing delay in heat transfer between the inert gas stream and the sample with increasing rate of heating reducing the sample weight can partly but not fully compensate this effect by using the natural maturation series of westphalian coals and toarcian shales it was possible to illustrate that geological extrapolations from slow heating rate experiments fit much better to natural petroleum formation than those from fast heating rates the latter lead to temperature predictions which are too low by 30 40 c which in turn would result in a 1000 m failure when predicting the oil window depth in an average sedimentary basins

genetic classification of petroleum systems our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories 1 charge factor supercharged normally charged or undercharged 2 migration drainage style vertically drained or laterally drained and 3 entrapment style high impedance or low impedance the charge factor is estimated on the basis of the richness and volumetrics of mature source rocks the source potential index spi which combines source rock richness and thickness into a single parameter is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity in extensively explored basins a positive correlation exists between the magnitude of spi and basin wide petroleum reserves the migration drainage style is determined from the structural and stratigraphic framework of a basin vertical migration drainage which occurs mainly through faults and fracture systems breaching a seal is characteristic of petroleum systems contained within rift basins deltaic sequences salt dome provinces wrench basins and fold and thrust belts in contrast lateral migration drainage is dominant wherever stratigraphically continuous seal reservoir doublets extend over a very large area in a tectonically stable province e g commonly foreland or intracratonic platform basins recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the hydrocarbon kitchens the entrapment style which is also dependent on the structural framework and the presence and effectiveness of seals describes the degree of resistance i e impedance working against dispersion of the petroleum charge application of these working concepts should help to significantly reduce geologic risk particularly in new ventures type exploration

source rock analysis and petroleum geochemistry of the trym discovery norwegian north sea a middle jurassic coal sourced petroleum system abstract the 3 7 4 well trym in the norwegian part of the sogne basin north sea discovered condensates in middle jurassic reservoir sandstones and in addition penetrated four middle jurassic coal seams 0 14 0 56 m thick the precursor peats of the coals which have a complex vitrinite and inertinite rich composition accumulated in coastal plain mires and the depositional conditions of the peats influenced the source rock potential of the resulting coals vitrinite reflectance values from 0 86 0 87 r o and an average t max of 438 c indicate that the coals are thermally mature but they may be interpreted only to be in the early phase of petroleum generation the hydrogen indices of the coals are generally below 200 and crude oil saturation of the coals may have been hindered by an uneven in seam distribution of favourable hydrogen indices 200 coupled with the comparatively thick seams condensate source rock correlations indicate a similarity between the trym condensates and extracts from the coals in the 3 7 4 well and stable carbon isotope data infer a common source for the trym condensates and the condensates and oils from the harald and lulita fields in the danish part of the sogne basin the harald and lulita fields have recently been proven to represent a middle jurassic coal sourced petroleum system the lulu bryne lulu petroleum system and the trym condensate discovery is thus another example of this petroleum system which may be more widespread in the central graben

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

the effect of interbedding on shale reservoir properties north sea oil is overwhelmingly generated in shales of the upper jurassic basal cretaceous kimmeridge clay formation once generated the oil is expelled and ultimately migrates to accumulate in sandstone or carbonate reservoirs the source rock shales however still contain the portion of the oil that was not expelled as a consequence such shales and juxtaposed non source lithofacies can form the targets for the exploration of unconventional oil in this paper we examine part of the kimmeridge clay formation as a hybrid shale resource system within which hot shale and organic lean sandstone and siltstone intervals are intimately interbedded this hybrid system can contain a greater volume of oil because of the increased storage capacity due to larger matrix porosities of the sand silt interbeds together with a lower adsorptive affinity in the interbedded sandstone the relationship between the estimated volume percentages of sand and mudstone and free oil determined from rock eval s1 yields is used to place limits on the drainage of oil from source mudstone to reservoir sand at the decimeter scale these data are used to determine oil saturations in interbedded sand mudstone sequences at peak oil maturity higher values of free hydrocarbon as evidenced by the s1 value in mudstone suggest that more oil is being retained in the mudstone while higher s1 values in the interbedded sands suggest the oil is being drained to saturate the larger pore spaces high silica content in the interbeds confirms the brittleness in this mudstone sandstone lithofacies an important factor to be considered for fracture stimulation to successfully work in a hybrid system the key points of this hybrid unconventional system are the thickness storage capacity and the possibility to capture a portion of the expelled as well as retained oil

source rock heterogeneity of the upper jurassic draupne formation north viking graben and its relevance to petroleum generation studies abstract the upper jurassic draupne formation in the north viking graben north sea has been studied to identify lateral and vertical variations in source rock characteristics and their effect on the timing of petroleum generation fourteen source rock samples from the western flank of the graben and five from the eastern flank were analysed using rock eval analysis microscopy open system pyrolysis gas chromatography and kinetic experiments two major organic facies with different petroleum generation characteristics were identified a stratigraphically higher thermally less stable facies corresponding to a type ii kerogen with hi hydrogen index values of 350 mg hc g toc and a stratigraphically lower more stable type ii iii facies with hi values

phase fractionation and oil condensate mass balance in the south marsh island block 208 239 area offshore louisiana abstract phase fractionation can strongly deplete oil of its volatile compounds in a regular and characteristic fashion this process has affected oils to a remarkably uniform extent throughout the 30 15 km south marsh island 208 239 and vermilion 30 31 area including the tiger shoal starfak mound point lighthouse point amber trinity shoal and aquamarine fields just offshore louisiana fractionation of the original parent oil likely occurred in the deep relatively flat lying rob l sand that underlies the area and produced gas washed oils mean api 33 and gas condensates mean api 50 in a volume ratio of 1 3 5 both fractionated oil and vapor migrated from the fractionation site to shallower reservoirs however the estimated ultimate production ratio of gas washed oil to gas condensate in this group of fields is 1 0 32 about 11 times higher than would be expected on mass balance considerations alone thus there is an apparent deficiency of producible gas condensate relative to the amount of producible oil for the entire study area and for every field in that area in the case of the tiger shoal field the ratio of industry estimated ultimately producible oil to gas condensate is 1 1 1 based on the production data we conclude that either there is an additional 6 4 10 6 m 3 43 mmbbl of undiscovered and or unproduced condensate in the area or that condensate has escaped preferentially in vapor form to the seafloor the well studied and nearly depleted tiger shoal field provides a good example of how chemical data can be analyzed in a way that contributes insight into the phase fractionation process and the remaining exploration potential of an area

comparison of kinetic analysis of source rocks and kerogen concentrates abstract shales and kerogen concentrates from the green river rundel ohio draupne and phosphoria formations were examined by pyromat ii micropyrolysis and kinetic parameters were determined by the shift in t max discrete distribution modified friedman and modified coats redfern methods overall the shales and corresponding kerogens exhibited very similar kinetic parameters green river rundel and ohio shales and kerogens exhibited principal discrete activation energies of 54 57 kcal mol narrow distributions and t max at 25 c min heating rate around 480 c draupne and phosphoria shales and kerogens exhibited kinetic parameters typical of type ii source rocks principal discrete activation energies of 54 57 kcal mol broad distributions and t max at 25 c min around 459 c the discrete distribution kinetic parameters were used to calculate oil generation at laboratory and geological heating rates each shale and corresponding kerogen exhibited generation curves and 50 generation temperatures that were very similar the principal difference was that the kerogens exhibited slightly more oil generation at low temperatures compared to the corresponding shales some kerogens exhibited curves which were also shifted to slightly lower temperatures than those of the corresponding shales for these specific shales and kerogens the results indicate that kerogen isolation does little to affect the pyrolysis kinetic parameters although from a limited number of samples these results suggest kerogen isolation may not be necessary to derive valid kinetic parameters

oscillatory zoned fayalitic olivine from the lewis cliff 90500 cm2 meteorite abstract a grain of fayalitic olivine with oscillatory fe rich and fe poor zoning occurs in the antarctic lewis cliff 90500 cm meteorite suggesting reaction via diffusion this grain is continuously enclosed by a fine grained rim ranging from 20 to 100 m in thickness phyllosilicates and other hydrous phases occur at three broken edges of the grain as well as within its surrounding rim suggesting in situ alteration via aqueous processes this olivine grain plus its rim provides evidence for both anhydrous reaction that predated the accretion of the meteorite parent body and hydrous alteration that presumably occurred on the parent body

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

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

efficiency of petroleum expulsion from shale source rocks the limited data available on the mechanism and the efficiency of the processes by which petroleum is expelled in the subsurface from source rocks into adjacent reservoir rocks are mostly qualitative1 2 we present here material balance type comparisons of sample series extending from the centre portions of two adjacent hydrocarbon source rock units towards their outer edges3 which enable expulsion efficiencies to be determined in certain parts of the shale the expulsion efficiencies for total extract and its saturated and aromatic hydrocarbon fractions have much higher values than previously thought reaching up to 80 for the total extract which increase towards possible secondary migration avenues the expulsion is associated with fractionation effects such as those based on polarity differences also expulsion efficiencies were found to be related to the degree of hydrocarbon saturation of the pore system they are higher for a rich oil prone source rock unit compared with a poorer quality one which had generated less hydrocarbons

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

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

calculation of petroleum masses generated and expelled from source rocks abstract an algebraic scheme for calculating the masses of petroleum formed in mature source rocks has been constructed the scheme exploits routine geochemical measurements and a basic understanding of the behaviour of sedimentary organic matter at elevated temperatures under both laboratory and subsurface conditions application of these techniques to data from a wide range of source rock types has led to the following general conclusions 1 1 major oil and gas generation from kerogen occurs between 120 and 150 c in the subsurface gas generation continues to temperatures 160 c 2 2 oil prone source rocks with average initial potential 5 kgt 1 of rock and average organic carbon contents 1 5 expel 60 90 of the total oil generated 3 3 oil expulsion from leaner source rocks is less efficient most of the oil generated remains in the source rock it is subsequently converted to lighter components at higher temperatures and expelled in the vapour state 4 4 the major loss of organic carbon from rich oil prone source rocks during generation and expulsion means that the petroleum potential and organic carbon content of mature source rocks are much less than their initial immature values hence the algebraic scheme must be used to calculate the initial values before expelled petroleum masses can be determined