evaluation of kinetic uncertainty in numerical models of petroleum generation oil prone marine petroleum source rocks contain type i or type ii kerogen having rock eval pyrolysis hydrogen indices greater than 600 or 300 600 mg hydrocarbon g total organic carbon hi mg hc g toc respectively samples from 29 marine source rocks worldwide that contain mainly type ii kerogen hi 230 786 mg hc g toc were subjected to open system programmed pyrolysis to determine the activation energy distributions for petroleum generation assuming a burial heating rate of 1c m y for each measured activation energy distribution the calculated average temperature for 50 fractional conversion of the kerogen in the samples to petroleum is approximately 136 7c but the range spans about 30c 121 151c fifty two outcrop samples of thermally immature jurassic oxford clay formation were collected from five locations in the united kingdom to determine the variations of kinetic response for one source rock unit the samples contain mainly type i or type ii kerogens hi 230 774 mg hc g toc at a heating rate of 1c m y the calculated temperatures for 50 fractional conversion of the oxford clay kerogens to petroleum differ by as much as 23c 127 150c the data indicate that kerogen type as defined by hydrogen index is not systematically linked to kinetic response and that default kinetics for the thermal decomposition of type i or type ii kerogen can introduce unacceptable errors into numerical simulations furthermore custom kinetics based on one or a few samples may be inadequate to account for variations in organofacies within a source rock we propose three methods to evaluate the uncertainty contributed by kerogen kinetics to numerical simulations 1 use the average kinetic distribution for multiple samples of source rock and the standard deviation for each activation energy in that distribution 2 use source rock kinetics determined at several locations to describe different parts of the study area and 3 use a weighted average method that combines kinetics for samples from different locations in the source rock unit by giving the activation energy distribution for each sample a weight proportional to its rock eval pyrolysis s2 yield hydrocarbons generated by pyrolytic degradation of organic matter

the cenomanian turonian oceanic anoxic event in the south atlantic new insights from a geochemical study of dsdp site 530a abstract one of the key objectives of deep sea drilling project dsdp leg 75 was to shed light on the underlying causes of cretaceous oceanic anoxia in the south atlantic by addressing two major hypotheses productivity productivity driven anoxia vs enhanced ocean stratification leading to preservation of organic matter and black shale deposition here we present a detailed geochemical dataset from sediments deposited during the cenomanian turonian c t transition and the global oceanic anoxic event 2 oae 2 at dsdp site 530a located off shore namibia southeast angola basin north of walvis ridge to characterise the succession of alternating black and green shales at this site and to reconstruct the evolution of their paleoenvironmental setting we have combined data derived from investigations on bulk organic matter biomarkers and the inorganic fraction the location of the c t boundary itself is biostratigraphically not well constrained due to the carbonate poor but organic matter rich facies of these sediments the bulk 13corg record and compound specific 13c data in combination with published as well as new biostratigraphic data enabled us to locate more precisely the c t boundary at dsdp site 530a the compound specific 13c record is the first of this kind reported from c t black shales in the south atlantic it is employed for paleoenvironmental reconstructions and chemostratigraphic correlation to other c t sections in order to discuss the paleoceanographic aspects and implications of the observations at dsdp site 530a in a broader context e g with regard to the potential trigger mechanisms of oae 2 global changes in black shale deposition and climate on a stratigraphic level an approximation and monitoring of the syndepositional degree of oxygen depletion within the sediments bottom waters in comparison to the upper water column is achieved by comparing normalised concentrations of redox sensitive trace elements with the abundance of highly source specific molecular compounds these biomarkers are derived from photoautotrophic and simultaneously anoxygenic green sulphur bacteria chlorobiacea and are interpreted as paleoindicators for events of photic zone euxinia in contrast to a number of other oae 2 sections that are characterised by continuous black shale sequences dsdp site 530a represents a highly dynamic setting where newly deposited black shales were repeatedly exposed to conditions of subtle bottom water re oxidation presumably leading to their progressive alteration into green shales the frequent alternation between both facies and the related anoxic to slight oxygenated conditions can be best explained by variations in vertical extent of an oxygen minimum zone in response to changes in a highly productive western continental margin setting driven by upwelling

the tectonic evolution of the south atlantic from late jurassic to present an improved tectonic database for the south atlantic has been compiled by combining magnetic anomaly geosat altimetry and onshore geologic data we used this database to obtain a revised plate kinematic model starting with a new fit reconstruction for the continents around the south atlantic we present a high resolution isochron map from chron m4 to present fit reconstructions of south america and africa that require rigid continental plates result in substantial misfits either in the southern south atlantic or in the equatorial atlantic to achieve a fit without gaps we assume a combination of complex rift and strike slip movements 1 along the south american parana chacos basin deformation zone 2 within marginal basins in south america salado colorado basin and 3 along the benue trough niger rift system in africa these faults are presumed to have been active before or during the breakup of the continents our model describes a successive unzipping of rift zones starting in the southern south atlantic between 150 ma tithonian and approximately 130 ma hauterivian rifting propagated to 38 s causing tectonic movements within the colorado and salado basins subsequently between 130 ma and chron m4 126 5 ma the tip of the south atlantic rift moved to 28 s resulting in intracontinental deformation along the parana chacos basin deformation zone between chron m4 and chron mo 118 7 ma rifting propagated into the benue trough and niger rift inducing rift and strike slip motion after chron mo the equatorial atlantic began to open while rifting and strike slip motion still occurred in the benue trough and niger rift since chron 34 84 ma the opening of the south atlantic is characterized by simple divergence of two rigid continental plates

relating petroleum system and play development to basin evolution west african south atlantic basins abstract sedimentary basins can be classified according to their structural genesis and evolutionary history and the latter can be linked to petroleum system and play development we propose an approach in which we use the established concepts in a new way breaking basins down into their natural basin cycle division then defining the characteristics of each basin cycle including the type of petroleum systems and plays they may contain and comparing them with similar basin cycles in other basins thereby providing a means to learn through a greater population of perhaps not immediately obvious analogues furthermore we introduce the use of the trajectory plot as a new tool in such an analysis this methodology has been applied to the west african south atlantic marginal basins between cameroon and angola and we demonstrate that the similar tectonostratigraphic evolution of the individual basins along this margin has led to the development of similar types of petroleum systems and play level s consequently we can make analogue comparisons among these basins in order to evaluate and predict the presence of potential yet undiscovered hydrocarbon accumulations in less well explored parts of the margin

bulk kinetic parameters and structural moieties of asphaltenes and kerogens from a sulphur rich source rock sequence and related petroleums non isothermal open system pyrolysis gas chromatography and bulk petroleum generation experiments were performed on type ii s petroleum asphaltenes source rock asphaltenes and related kerogens to evaluate petroleum composition and generation timing the results show that contrary to convention there are significant differences in the reactivity between petroleum asphaltenes and their related kerogens in the studied type ii s petroleum system and these samples yield kinetic models that predict onset peak and completion of petroleum generation under different temperatures petroleum asphaltenes and source rock asphaltenes are less stable and show tighter petroleum formation windows than kerogens when extrapolated to geological heating rates source rock asphaltene related kerogen and oil asphaltene pyrolysates possess structural differences as revealed in the aromaticity and organic sulphur content aromaticity was highest in pyrolysates of source rock asphaltenes intermediate in kerogen pyrolysates and lowest in pyrolysates from petroleum asphaltenes in addition the highest organic sulphur content was identified in kerogen pyrolysates whereas pyrolysates of both source rock and petroleum asphaltenes are similar in organic sulphur content thus the amount of organic sulphur is not proportional to the reactivity of petroleum generation from asphaltenes at lower thermal stress it is more likely that kerogens and asphaltenes possess different configurations and types of sulphur bonds resulting in cracking of covalent bonds at different levels of thermal stress

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

organic geochemical characterisation of depositional palaeoenvironments of source rocks and oils in brazilian marginal basins abstract an investigation of bulk isotopic and molecular features of a wide selection of source rocks and oils from brazilian marginal basins ranging from lower cretaceous to tertiary in age provides a number of organic geochemical criteria that characterise and distinguish their depositional palaeo environments the methods employed include evaluation of organic carbon contents rock eval pyrolysis vitrinite reflectance measurements determination of carbon isotope ratios elemental and visual kerogen analysis assessment of oils and solvent extracts by liquid and gas chromatography and quantitative biological marker investigations using gc ms for aliphatic hydrocarbons and uv vis spectrophotometry for metalloporphyrins selected data were evaluated using principal component analysis the results enable the recognition and differentiation of seven depositional regimes lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate marine deltaic marine highly anoxic with a predominance of calcareous mudstone lithology and marine anoxic with predominance of siliciclastic lithology diagnostic features in the biological markers from these depositional environments include the carbon number distributions of n alkanes pristane phytane ratios absolute concentrations of carotane higher acyclic isoprenoids c 30 hopane and steranes and the abundance of the latter relative to 4 methylsteranes the occurrence and abundance of particular biological markers such as gammacerane tricyclic and tetracyclic terpanes 18 h oleanane 28 30 bisnorhopane and 25 28 30 trisnorhopane and the relative abundances of nickel and vanadyl porphyrins

predicting the generation of heavy oils in carbonate evaporitic environments using pyrolysis methods abstract a series of low maturity kerogen and asphaltene samples of a sulphur rich mediterranean carbonate source rock sequence as well as two associated oil samples were analysed by different pyrolysis methods the source rock was characterised by the occurrence of four different lithotypes three of which possessed source potential elemental analysis revealed that each source lithofacies contained a distinct kerogen type comprising type i s for shale intercalations type ii s in the laminated lithofacies and low sulphur type ii in the pure carbonate portions of the source rock pyrolysis gas chromatography using coupled fid and hecd detectors provided a more detailed insight into kerogen asphaltene composition than afforded by rock eval pyrolysis bulk kinetic analysis demonstrated that asphaltenes and type i s kerogens were the most labile species present in the source rocks type ii s kerogens often quoted as the major source of heavy oils were the most stable of the sulphur rich organic matter types the occurrence of various kerogen types with differing stabilities in the carbonate source rock analysed as determined by bulk pyrolysis fid implies that peak hydrocarbon generation in the source rock sequence is not confined to a single temperature but rather to a relatively large temperature range of roughly 20 c combination of bulk hydrocarbon generation kinetics and a multistep pyrolysis approach demonstrated that for carbonate evaporitic environments it is necessary to differentiate between early and late maturity products this is because the lower energies 46 49 kcal mol which may be attributed to s c bond cleavage reactions are empirically of greater importance especially in view of the fact that they may represent the main generation stage under natural conditions

evidence of a large upper cretaceous depocentre across the continent ocean boundary of the congo angola basin implications for palaeo drainage and potential ultra deep source rocks abstract the analysis of 2d deep seismic reflection profiles across the slope and abyssal plain of the angola oceanic basin reveals the existence of a significant and formerly unknown depocentre beneath the giant cenozoic congo deep sea fan between 7000 m and 9000 m depth deposited directly onto the aptian oceanic crust the unit which is up to 2 5 km thick and extends for more than 200 km basinwards of the continent ocean boundary is probably aged albian turonian its radial fan shaped depocentre is centred on the present day congo river outlet and contains at least 0 2 mio km 3 of sediments these observations and the results from flexural modelling indicate that 1 the location of the congo river s outlet has remained fairly stable since the late cretaceous and 2 the basal unit was indeed sourced by a palaeo congo river probably located nearby the present day one thus the atlantic sedimentary system related to the exoreism of the congo river is much older than previously thought thermal modelling indicates that the maturation history of this upper cretaceous deposits is highly influenced by the interaction between the initial high heat flow of the young oceanic crust and further increase in sediment supply due to the progradation of the overlying tertiary deep sea fan during the miocene hence despite low present day heat flow values should the unit have source rock potential its basal section may be currently generating hydrocarbons all in all the results from our models also suggest that the interplay between an initially high heat flow and the further high sediment supply in areas of major river input may be a key factor for the thermal maturation of potential source rocks deposited onto a present day cold oceanic crust

sediment deposits in the cape basin indications for shifting ocean currents the benguela current system running off southwest africa is one of the world s largest upwelling regions the current has strongly influenced sedimentary features on the continental margin to unravel its development seismic stratigraphy tied to drilling results from ocean drilling program leg 175 sites 10851087 was established four units southern cape basin scb 1 to scb 4 were defined for the cenozoic sediments the upper unit scb 1 1 5 ma characterized by continuous high amplitude reflectors represents global cooling and glacial interglacial cycles unit scb 2 14 ma distinguished by low amplitude reflections is associated with the onset of the upwelling system and establishment of the modern circulation pattern in the cape basin slump scarps are concentrated along the middle and upper shelf slope suggesting they are caused by a combination of mass movements triggered by bottom currents and slope instabilities because of increased deposition associated with the upwelling a westward extension and or movement of upwelling filaments is interpreted from the observed seaward shift of scarp locations with time erosion associated with stronger currents probably thinned unit scb 2 in the south the two lower units scb 3 and scb 4 56 ma probably represent material eroded from the shelf break and deposited during a major oligoceneearly miocene regression that is consistent with a significant uplift of southern africa the basal reflector scb d of unit scb 4 is associated with the prominent reflector d or l described in previous publications

source rock characteristics and compositional kinetic models of cretaceous organic rich black shales offshore southwestern africa abstract the source rock potential of cretaceous organic rich whole rock samples from deep sea drilling project dsdp wells offshore southwestern africa was investigated using bulk and quantitative pyrolysis techniques the sample material was taken from organic rich intervals of aptian albian and turonian aged core samples from dsdp site 364 offshore angola dsdp well 530a north of the walvis ridge offshore namibia and dsdp well 361 offshore south africa the analytical program included toc rock eval pyrolysis gc bulk kinetics and micro scale sealed vessel pyrolysis mssv experiments the results were used to determine differences in the source rock petroleum type organofacies petroleum composition gas oil ratio gor and pressure volume temperature pvt behavior of hydrocarbons generated from these black shales for petroleum system modeling purposes the investigated aptian and albian organic rich shales proved to contain excellent quality marine kerogens the highest source rock potential was identified in sapropelic shales in dsdp well 364 containing very homogeneous type ii and organic sulfur rich type iis kerogen they generate p n a low wax oils and low gor sulfur rich oils whereas type iii kerogen rich silty sandstones of dsdp well 361 show a potential for gas condensate generation bulk kinetic experiments on these samples indicate that the organic sulfur contents influence kerogen transformation rates type iis kerogen being the least stable south of the walvis ridge the turonian contains predominantly a type iii kerogen north of the walvis ridge the turonian black shales contain type ii kerogen and have the potential to generate p n a low and high wax oils the latter with a high gor at high maturity our results provide the first compositional kinetic description of cretaceous organic rich black shales and demonstrate the excellent source rock potential especially of the aptian aged source rock that has been recognized in a number of the south atlantic offshore basins

structural evolution of the orange basin gravity driven system offshore namibia the orange basin records the development of the late jurassic to present day volcanic rifted passive margin of namibia regional extension is recorded by a late jurassic to lower cretaceous syn rift megasequence which is separated from a cretaceous to present day post rift megasequence by the late hauterivian ca 130 ma break up unconformity the late cretaceous post rift evolution of the basin is characterized by episodic gravitational collapse of the margin gravitational collapse is recorded as a series of shale detached gravity slide systems consisting of an up dip extensional domain that is linked to a down dip zone of contraction domain along a thin basal detachment of turonian age the extensional domain is characterized by basinward dipping listric faults that sole into the basal detachment the contractional domain consists of landward dipping listric faults and strongly asymmetric basinward verging thrust related folds growth stratal patterns suggest that the gravitational collapse of the margin was short lived spanning from the coniacian ca 90 ma to the santonian ca 83 ma structural restorations of the main gravity driven system show a lack of balance between up dip extension 24 km and down dip shortening 16 km gravity sliding in the namibian margin is interpreted to have occurred as a series of episodic short lived gravity sliding between the cenomanian ca 100 ma and the campanian ca 80 ma gravity sliding and spreading are interpreted to be the result of episodic cratonic uplift combined with differential thermal subsidence sliding may have also been favoured by the presence of an efficient detachment layer in turonian source rocks

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

ion microprobe dating of zircons from active dayingshan volcano tengchong se tibetan plateau time scales and nature of magma chamber storage abstract the rare occurrences of active volcanoes on the tibetan plateau provide a unique opportunity to investigate time scales of magma chamber processes for post collisional potassic volcanism this research utilizes high spatial resolution u th disequilibrium dating methods to date zircons from the active dayingshan volcano tengchong se tibetan plateau which erupted last during the holocene zircon crystal ages can be used to provide constraints on the magma chamber storage time measured zircon interiors yielded an isochron age of 87 5 6 5 ka while zircon outermost rims yielded an isochron age of 58 13 ka the calculated zircon crystal storage time for the most recent eruption is 48 ka at least two separate late pleistocene zircon crystallization events have occurred where the older age population represents antecrysts remobilized from an earlier magmatic episode but protracted crystallization cannot be ruled out regardless the similarity in zircon age populations between dayingshan volcano and maanshan volcano 13 km apart in the tengchong volcanic field suggests a synchronous thermal history of the magma reservoir possibly in an extensive interconnected magma chamber beneath the tengchong volcanic field

mesozoic break up of sw gondwana implications for regional hydrocarbon potential of the southern south atlantic abstract this work provides new palinspastic palaeofacies reconstructions of sw gondwana incorporating rotation of a falkland malvinas microplate we discuss the implications of this for the tectonic evolution of the southern south atlantic and hence for the regional hydrocarbon potential existing gondwana reconstructions display good fits of major continents but poorly constrained fits of microcontinents in most continental reconstructions the falkland malvinas plateau was assumed to be a rigid fragment of pre permian south american crust however it has been suggested on the basis of palaeomagnetic data that the falkland malvinas islands were rotated by 180 after 190 ma this rotation hypothesis has been successfully tested on the basis of devonian stratigraphy and palaeontology permian stratigraphy and sedimentology and late palaeozoic and early mesozoic structure making it unlikely that the plateau behaved as a rigid structure during breakup we have explored the consequences of accepting this hypothesis for the tectonic evolution of sw gondwana by compiling new palaeogeographic maps for the permian cretaceous of the southern atlantic area to achieve a realistic close fit we have devised a pre rift proxy for the ocean continent boundary for the south atlantic in order to produce the best fit it is necessary to subdivide south america into four plates the consequences of this are far reaching our work suggests that although sedimentary basins were initiated at different times three major tectonic phases can be recognised in regional terms these can be thought of as pre syn and post rift during the pre rift time until the late triassic the area was dominated by compressional tectonism and formed part of the gondwana foreland the falkland malvinas islands lay east of africa the falkland malvinas plateau was 33 shorter and patagonia was displaced east with respect to the rest of south america in part along the line of the gastre fault system potential source facies are dominantly post glacial black shales of late permian age deposited in lacustrine or hyposaline marine environments these rocks would also be an effective regional seal sandstones deposited in the late permian would be dominantly volcaniclastic with poor reservoir qualities triassic sandstones tend to be more mature there was significant extension from about 210 ma end triassic until the south atlantic opened at about 130 ma early cretaceous in the early syn rift phase extension was accompanied by strike slip faulting and block rotation later extension was accompanied by extrusion of large volumes of lava early opening of the south atlantic was oblique which created basins at high angle to the trend of the ocean on the argentine margin and resulted in microplate rotation in ne brazil intermittent physical barriers controlled deposition of upper jurassic cretaceous anoxic sediments during breakup some of these mudrock units are effective seals with likely regional extent during crustal reorganisation clastic sediments changed from a uniform volcaniclastic provenance to local derivation with variable reservoir quality in the late rift and early post rift phase continental extension changed from oblique to normal and basins developed parallel to the continental margins of the south atlantic this change coincides with the main rifting in the equatorial basins of brazil and the early impact of the santa helena plume it resulted in widespread development of unconformities the abandonment of the reconcavo tucano jatoba rift and the end of ne brazil plate rotation which remained attached to south america there was extensive deposition of evaporites concentrated in but not restricted to the area north of the rio grande rise walvis ridge widespread deposits can be used to define potential regional elements of hydrocarbon systems and to provide a framework for relating more local elements our main conclusion is that the regional hydrocarbon potential of the southern south atlantic has been constrained by the tectonic evolution

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

reconnaissance study of the ancient zaire congo deep sea fan zaiango project analysis of more than 19 000 km of multichannel seismic reflection data from the zaiango project covering the zaire deep sea fan allowed us to identify the oceanic crust and five seismostratigraphic units on the basin floor and abyssal plain in the absence of a direct stratigraphic tie the time frame is provided by long distance correlations a stratigraphic model for the evolution of the zaire deep sea fan is proposed a widespread major regional unconformity representing probably the eocene oligocene transition marks a drastic change of sedimentation pattern in the basin floor a pelagic aggradational sequence albian eocene overlying the oceanic crust gives way to an onlapping prograding sequence of turbidite deposits oligocene recent this change marks the onset of the ancient zaire deep sea fan triggered by the climatic change related to the greenhouse icehouse shift at the eocene oligocene transition which was responsible for a drastic increase in continental erosion and terrigenous sedimentary supply to the margin the volume of the fan is at least 0 7 mkm 3 much broader and thicker than formerly assumed a short lived episode of rapid facies progradation

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

pvt and phase behaviour analysis in petroleum exploration abstract this paper describes the application of pvt data routinely determined for almost all conventional oil tests with respect to petroleum exploration in a broader context the use of pvt and phase behaviour analysis focuses on phase envelope evolution as a function of source rock maturity and secondary migration using both laboratory analyses and natural examples from the ekofisk eldfisk and snorre fields as well as data from the tampen spur area and barents sea in general pvt analysis is demonstrated to be applicable for relative maturity estimation recognition of mixing effects volumetric evaluation of complex reservoir filling histories and as a screening tool for oil population characterisation pvt analysis is used in this paper as a tool complementary to organic geochemistry allowing the integration and interpretation of data reflecting fluid response to geological conditions on a regional scale

deep sampling and testing in soft stratified clay a 37 m thick layer of stratified clay encountered during a site investigation at swann s bridge near the sea coast at limavady northern ireland is one of the deepest and thickest layers of this type of material recorded in ireland a study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline the clay was deposited in a fresh water glacial lake formed approximately 13 000 bp the 37 m layer of clay can be divided into two separate zones the lower zone was deposited as a series of laminated layers of sand silt and clay whereas the upper zone was deposited as a largely homogeneous mixture a comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit the results obtained from these tests were complex and confusing particularly the results of tests done on samples from the lower zone the results of one dimensional compression tests unconsolidated und

a new approach to bridge the effect of organofacies variations on kinetic modelling and geological extrapolations abstract reliable prediction of petroleum formation is impeded by significant variations in organofacies that result from varying conditions during source rock deposition basin simulation programs can model lateral variations but are limited in their ability to account for vertical variations due to the impact on computation time and lack of representative kinetic parameters here we present a model that merges the petroleum formation characteristics of different organofacies vertically distributed in a heterogeneous source rock prior to kinetic modelling this approach allows the evaluation of one single overall kinetic model that accounts for the different petroleum generation characteristics of a variety of organofacies preserved in a source rock and balance the different petroleum formation processes according to their importance within the different organofacies bulk petroleum generation kinetics were determined on eleven draupne formation samples taken from a well in the tampen spur area using programmed temperature open system pyrolysis at 0 1 0 7 and 5 0 k min the samples covered the entire draupne formation from its bottom to its top in the studied well individual measurements taken at the same heating rate were summed to one pyrolysis yield curve and normalized to the average rock eval s2 value the three summed curves were then used as input to determine a kinetic model that is representative of the draupne formation in this well enhanced kinetic modelling was applied in order to account for the expected variations of frequency factors after geological extrapolation the resulting kinetic model represents the petroleum generation characteristics of the entire draupne formation in the study area accounting for the variability in source potential across organofacies

the micro scale simulation of maturation outline of a new technique and its potential applications a micro analytical technique has been developed for artifically maturing sedimentary organic matter and then quantifying the major components generated during this process in a single analytical step such a capability is well suited for examining the compositional relationships between kerogens and petroleums determining reaction kinetics and making precursor product mass balances according to this technique simulations are made using sealed glass capillary tubes heated here for three days at 300 c 330 c and 350 c pyrolysis products are then released directly into a combined thermovaporisation pyrolysis gc instrument and the major components of the entire c1 yto c35 range can be quantified in a single step using gas chromatography alkene yields are very low and pyrolysates are oil like this is exemplified by the fact that then c9 c19 alkane distribution range of simulated whole petroleum chromatograms from originally immaturegloeocapsamorpha typz alginite a resembles that seen in crude oils generated from this same kerogen type in nature sealed tube experiments usingbotryococcus type alginite a generated a high wax pyrolysate the relative abundance ofn alkanes in the c2 c32 range of many kerogen pyrolysates does not appear to change significantly despite an approximately fifteen fold difference inn alkane yield between the 300 c and 350 c experiments kerogens which are paraffinic oil prone and whose pyrolysates are very rich inn alkanes might therefore generate petroleums in nature with a fixed wet gas c2 c4 to oil c5 ratio alginite b in a greenland shale is much more thermally labile than eitherbotryococcus type alginite a orgloeocapsamorpha type alginite a the mass balance capabilities of the technique have been tested using alum shale kerogen two gas chromatograms were obtained one for the free compounds generated during simulation and one for the high temperature pyrolysate of the kerogen residue for each heating experiment precursor product relationships were qualitatively assessed and dead carbon formation was quantified in this exercise

late cretaceous anoxic events in the brazilian continental margin abstract a combined geochemical and micropalaeontological study of cenomanian to maastrichtian pelitic sediments from the brazilian continental margin has been undertaken the organic carbon contents rock eval pyrolysis results and biological marker distributions together with the taxonomic selection and distribution patterns of microfossil assemblages indicate that intermittent anoxic events occurred in the brazilian marginal basins during the cenomanian santonian with deposition taking place in progressively deeper waters from neritic to bathyal such events are characterised by the following 1 i a predominance among the benthonic foraminifera of low diversity small sized specimens mainly composed of gavelinellids buliminids and nodosariids indicating dysaerobic bottom conditions 2 ii levels with virtually no benthonic foraminifera and a well developed planktonic biota foraminifera radiolarians and diatoms indicating anaerobic bottom conditions with oxygenated surface waters 3 iii the occurrence of organic rich calcareous mudstone sediments 4 iv features in the biological marker distributions such as high concentrations of 28 30 bisnorhopane and 25 28 30 trisnorhopane up to 130 ppm a predominance of phytane over pristane and medium to high concentrations of nickel and vanadyl porphyrins up to ca 5700 ppm the widely recognized cenomanian turonian and santonian oceanic anoxic events schlanger and jenkyns 1976 ryan and cita 1977 and jenkyns 1980 are therefore manifest in the cassipore ceara sergipe alagoas and campos basins within the brazilian continental margin as is the presence of such events in the coniacian in contrast the campanian maastrichtian appears to be a time interval when deposition under oxygenated conditions produced sediments with low organic carbon contents and poor hydrocarbon source potential containing highly diversified and abundant calcareous and agglutinated benthonic foraminifera

organic geochemical evaluation of cretaceous shale samples from the orange basin south africa abstract organic geochemical evaluation of thirty two aptian to campanian shale samples from seven wells drilled on the shelf of the orange basin southwestern atlantic margin was carried out in order to determine their origin depositional environment thermal maturity and hydrocarbon potential the shale samples selected to represent highstand lowstand and transgressive systems tracts were analysed by rock eval pyrolysis for total organic c characteristics and by gas chromatography gc and gas chromatography mass spectrometry gc ms for n alkanes aliphatic isoprenoid hydrocarbons and biomarkers steranes hopanes and tricylic terpanes for most of the shale samples rock eval data hydrogen hi and oxygen index oi point to mainly type iii terrigenous organic matter only a few samples of turonian age reveal a higher proportion of marine organic matter being classified as type ii iii or type ii biomarker parameters suggest that the samples are deposited under suboxic to oxic environmental conditions rock eval data and biomarker maturity parameters assign for most of the samples a maturity level at the beginning of the oil window with some more mature samples of aptian albian and cenomanian age the hydrocarbon generation potential is low for most of the shelf shales as indicated by the s2 s3 ratio and hi values exceptions are some samples of turonian and aptian age