are time and temperature the only constraints to the simulation of organic matter maturation abstract confined pyrolysis hydrous pyrolysis and high pressure hydrous pyrolysis were performed with various samples toarcian shale and kerogen woodford shale and kerogen manakam coal and under different experimental conditions in order to test the effects of pyrolysis variables on the simulation of maturation of organic matter results show that i experimental time and temperature are not exchangeable parameters as suggested by first order kinetic law models ii increasing confining pressure 300 1300 bars in gold cell experiments performed on woodford samples has a limited influence on the reduction rate of the oil potential the tsom total soluble organic matter yield and the structure of the polars iii the presence of excess liquid water 0 100 weight in confined pyrolysis experiments does not significantly influence organic matter maturation however comparisons with classic hydrous pyrolysis 200 weight water could indicate major differences in timing and composition of the tsom bitumen expelled fraction as well as of the solid residue it appears that excess water is not necessary to simulate organic matter maturation when the system is sufficiently confined hydrous pyrolysis conditions low partial pressure of products delay woodford kerogen conversion in addition results concerning the mahakam coal suggest that the structure of the organic matter plays an important role concerning the water effect iv increasing water pressure in hydrous conditions 220 1300 bars drastically lowers and delays woodford kerogen maturation quantitative analysis of the water produced during confined pyrolysis and comparison of the extent of aromatization in hydrous and confined pyrolysis suggests that two competing hydrogen transfer mechanisms occur during organic matter pyrolysis this study shows that additional parameters must be defined when comparing the results of the experimental simulation of organic matter maturation

late wisconsinan stratigraphy and chronology of southern st george s bay newfoundland a re appraisal reply brookes identifies two points of difference in his discussion of our re appraisal of the late wisconsinan stratigraphy and chronology of southern st george s bay newfoundland i the applicability of our sedimentological model and ii the relation of sediments to late glacial sea level the latter point is the subject of a manuscript submitted for review to this journal incorporating 91 radiocarbon dates from onshore and offshore marine records 19 of which are reported for the first time we therefore restrict our rebuttal to what we believe are the critical disagreements in field observations and interpretations that underpin the two points of difference and invite readers to visit the contentious coastal sections to compare published accounts access to these sites is described in several field guides to southern st george s bay liverman and batterson 1995 liverman et al 2001 in our paper we explicitly state that for 80 of the 39 km long coastal exposure our non ridge sections p 866 our observations broadly confirm earlier interpretations by brookes 1969 1974 1977 and macclintock and twenhofel 1940 with the one important exception that we found no evidence for glacial readvance following initial deglaciation and marine submergence of the present coastline in almost 100 logged sections through non ridge exposures we did not encounter an upper till or ice contact gravels robinsons head drift indicative of a glacial readvance instead we described laterally continuous moderately to well sorted planar bedded and trough cross bedded fine gravel capping sections which we interpreted as glaciofluvial outwash p 859 figs 4 5 c consequently our deglacial depositional model for a large part of the coast of southern st george s bay is neither compatible with nor applicable to published sedimentary sequences in the remaining 20 of coastal exposure our ridge sections p 866 our mapping revealed complex sedimentary sequences of interbedded diamicton gravel and mud above

fractured tight sandstone oil and gas reservoirs a new play type in the dongpu depression bohai bay basin china although conventional reservoirs dominate the bohai basin china a new type of sandstone reservoir also exists in the dongpu depression that has a low matrix porosity tight in which natural fractures govern both permeability and porosity these fractured sandstones are located on a structurally modified buried hill underlying paleogene mudstones and are truncated along an angular unconformity the fractured sandstone oils of the triassic liujiagou heshanggou and ermaying formations are derived from the paleogene shahejie formation which reached peak oil generation and expulsion during the oligocene to early miocene 32 8 15 6 ma gas was generated primarily during the paleogene from carboniferous and permian coals petrographic evidence suggests that oil and gas emplacement followed the compaction and cementation of the triassic sandstone reservoirs fluid inclusion evidence and burial history analysis suggest that fractures developed before oil emplacement but may have coincided with peak gas generation which suggests that oil and gas mainly migrated and accumulated in fractures

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

sedimentary association of alternated mudstones and tight sandstones in china s oil and gas bearing basins and its natural gas accumulation abstract oil and gas resources are abundant in china s continental sedimentary basins where the main task of exploration has been finding oil for many years in recent years however new discoveries of large scale natural gas have been successively obtained the natural gas mainly exists in the sedimentary association of alternated mudstones and tight sandstones and is dominantly low permeability tight sand gas through the in depth study on gas reservoir analysis diagenetic evolution source rock distribution and hydrocarbon generating behavior natural gas generation and accumulation it is concluded that during the major subsiding stage of large scale lake basins the multicyclic subsiding process of the lake surface controls the development of high quality source rocks the wide distribution of sands and the superimposition of the two types of rocks in the vertical direction the lacustrine muddy source rocks are developed including mud shale carbonaceous mudstone and coal bed which are in the medium high evolution stage and produce mainly gas and the gas generation intensity is high through the analysis of the subsidence evolution processes of the carboniferous permian systems transitional marine continental facies in the ordos basin and the triassic xujiahe formation continental facies in the sichuan basin it is concluded that the widely distributed sandbodies of delta facies although with tight properties are interbedded with source rocks and easy to accumulate natural gases the natural gas is migrated and accumulated within small distance and is characterized by large area accumulation because of the strong hydrocarbon generation capacity big thickness and stable distribution of the underlying mud shale the potential of gas resources should not be underestimated the geocyclicity of china s continental sedimentary basins controls the sedimentary association of alternated mudstones and tight sandstones resulting in superimposed accumulations of shale gas and tight sand gas

multibeam bathymetry of glaciated terrain off southwest newfoundland abstract inner st george s bay newfoundland was mapped in 1988 using a suite of conventional geophysical and sampling tools the quaternary deposits sea level history and holocene littoral sediments were described in a series of papers in 1995 part of the previously mapped area was imaged using a multibeam mapping system the resulting high resolution images of bathymetry and backscatter are interpreted with reference to the previously collected data the multibeam imagery shows a late wisconsinan morainal bank that has been modified by marine processes during and following a t2 5 m postglacial sea level lowstand two types of terrain occur on the morainal bank in the extreme west where morainal till is close to the seabed the image shows areas with high reflectivity and rough texture that consist of bouldery gravel farther east the flanks of the moraine are buried by a prograded wedge of sediment eroded from the bank during the holocene transgression and transported towards the adjacent basin by waves and currents here areas of relatively smooth seabed on the multibeam bathymetry image consist of either mobile rippled poorly sorted gravel high reflectivity or sand lower reflectivity the image shows a submarine valley which according to the previous data was glacially overdeepened and subsequently partly filled by glacial marine and postglacial sediments shallow areas with high reflectivity on either side of the valley are seafloor exposures of a draped glacial marine unit that was deposited when the former ice margin was located close to the present coast between 13 3 and 10 8 ka an area of mounded morphology and high backscatter located below the level of the postglacial sea level lowstand is interpreted as till that has not been modified by wave processes the multibeam bathymetry and backscatter images reveal the inadequacies of the previous map that was compiled using data from conventional survey techniques

hydrothermal venting in magma deserts the ultraslow spreading gakkel and southwest indian ridges 1 detailed hydrothermal surveys over ridges with spreading rates of 50 150 mm yr have found a linear relation between spreading rate and the spatial frequency of hydrothermal venting but the validity of this relation at slow and ultraslow ridges is unproved here we compare hydrothermal plume surveys along three sections of the gakkel ridge arctic ocean and the southwest indian ridge swir to determine if hydrothermal activity is similarly distributed among these ultraslow ridge sections and if these distributions follow the hypothesized linear trend derived from surveys along fast ridges along the gakkel ridge most apparent vent sites occur on volcanic highs and the extraordinarily weak vertical density gradient of the deep arctic permits plumes to rise above the axial bathymetry individual plumes can thus be extensively dispersed along axis to distances 200 km and 75 of the total axial length surveyed is overlain by plumes detailed mapping of these plumes points to only 9 10 active sites in 850 km however yielding a site frequency fs sites 100 km of ridge length of 1 1 1 2 plumes detected along the swir are considerably less extensive for two reasons an apparent paucity of active vent fields on volcanic highs and a normal deep ocean density gradient that prevents extended plume rise along a western swir section 10 23 e we identify 3 8 sites so fs 0 3 0 8 along a previously surveyed 440 km section of the eastern swir 58 66 e 6 sites yield fs 1 3 plotting spreading rate us versus fs the ultraslow ridges and eight other ridge sections spanning the global range of spreading rate establish a robust linear trend fs 0 98 0 015us implying that the long term heat supply is the first order control on the global distribution of hydrothermal activity normalizing fs to the delivery rate of basaltic magma suggests that ultraslow ridges are several times more efficient than faster spreading ridges in supporting active vent fields this increased efficiency could derive from some combination of three dimensional magma focusing at volcanic centers deep mining of heat from gabbroic intrusions and direct cooling of the upper mantle and nonmagmatic heat supplied by exothermic serpentinization

geochemical constraints on the modes of carbonate precipitation in peridotites from the logatchev hydrothermal vent field and gakkel ridge the ultramafic hosted logatchev hydrothermal field lhf at 15 n on the mid atlantic ridge and the arctic gakkel ridge gr feature carbonate precipitates aragonite calcite and dolomite in voids and fractures within different types of host rocks we present chemical and sr isotopic compositions of these different carbonates to examine the conditions that led to their formation our data reveal that different processes have led to the precipitation of carbonates in the various settings seawater like 87sr 86sr ratios for aragonite in serpentinites 0 70909 to 0 70917 from the lhf are similar to those of aragonite from the gr 0 70912 to 0 70917 and indicate aragonite precipitation from seawater at ambient conditions at both sites aragonite veins in sulfide breccias from lhf also have seawater like sr isotope compositions 0 70909 to 0 70915 however their rare earth element ree patterns show a clear positive europium eu anomaly indicative of a small 1 hydrothermal contribution in contrast to aragonite dolomite from the lhf has precipitated at much higher temperatures 100 c and yet its 87sr 86sr ratios 0 70896 to 0 70907 are only slightly lower than those of aragonite even higher temperatures are calculated for the precipitation of deformed calcite veins in serpentine talc fault schists form north of the lhf these calcites show unradiogenic 87sr 86sr ratios 0 70460 to 0 70499 indicative of precipitation from evolved hydrothermal fluids a simple mixing model based on sr mass balance and enthalpy conservation indicates strongly variable conditions of fluid mixing and heat transfers involved in carbonate formation dolomite precipitated from a mixture of 97 seawater and 3 hydrothermal fluid that should have had a temperature of approximately 14 c assuming that no heat was transferred the much higher apparent precipitation temperatures based on oxygen isotopes 100 c may be indicative of conductive heating probably of seawater prior to mixing the hydrothermal calcite in the fault schist has precipitated from a mixture of 67 hydrothermal fluid and 33 seawater which should have had an isenthalpic mixing temperature of 250 c the significantly lower temperatures calculated from oxygen isotopes are likely due to conductive cooling of hydrothermal fluid discharging along faults rare earth element patterns corroborate the results of the mixing model since the hydrothermal calcite which formed from waters with the greatest hydrothermal contribution has ree patterns that closely resemble those of vent fluids from the lhf our results demonstrate for the first time that 1 precipitation from pure seawater 2 conductive heating of seawater and 3 conductive cooling of hydrothermal fluids in the sub seafloor all can lead to carbonate precipitation within a single ultramafic hosted hydrothermal system

mesozoic and cenozoic tectono thermal reconstruction of the western bohai bay basin east china with implications for hydrocarbon generation and migration abstract studies on the tectono thermal evolution of the western bohai bay basin wbbb including the jizhong sub basin and cangxian uplift are important for further petroleum exploration and exploitation this study aims to reconstruct the tectono thermal history of the wbbb based on a combination of 125 vitrinite reflectance ro data and seven apatite fission track aft and nine apatite u th he ahe ages the effective aft ages range from 60 3 to 97 0 ma with mean track lengths of 10 86 12 64 m the variable single grain aft ages are explained to be due to the parameter dpar the effective ahe ages range from 21 1 ma to 75 0 ma two rapid cooling events revealed by the thermal modeling results occurred during the early late cretaceous 130 90 ma and late eocene early miocene 40 18 ma respectively the fuping complex which is located in the western margin of the wbbb and mainly composed of the paleo proterozoic high grade gneisses experienced the intensive extension detachment during the early late cretaceous along with the subduction of the izanagi plate that was probably responsible for the first cooling event the second cooling event was caused by the subduction of the pacific plate during the middle eocene early miocene 43 23 ma as well as the collision of the indian and eurasian plates and the rollback of the subducting pacific plate during the early miocene 23 18 ma the wbbb experienced two heat flow peaks of 75 and 80 mw m2 during the early cretaceous and the late eocene respectively during the late eocene early miocene rapid subsidence in the baxian depression one secondary tectonic unit of the jizhong sub basin coupled with the rapid uplift in the cangxian uplift caused the shahejie formation of the middle upper eocene to generate gas during the early miocene meanwhile tectonic movement during the early miocene also caused faults to become migration paths as revealed by the homogenization temperature of the fluid inclusion this study provides new insights regarding the tectonic and hydrocarbon evolution of the wbbb

the postglacial relative sea level lowstand in newfoundland relative sea level in coastal regions of newfoundland fell from late glacial maximum levels to postglacial minima in several phases i an early period of high relative sea level when late wisconsinan ice was at the coast and discharging meltwater plumes into the ocean ii a period of rapidly falling relative sea level during which glaciers retreated inland and iii a period without glacier ice during which relative sea level continued to fall but at decreasing rates falling relative sea level caused fluvial incision of glacial deposits in some coastal embayments and culminated with the construction of lowstand marine deltas these deltas were submerged during the subsequent holocene transgression seismic reflection data from selected deltas show that they comprise wedges of sediment with prograded seaward dipping foreset style internal reflections the depth of the relative sea level lowstand varies spatially and it was diachronous it occurred relatively early and deep in peripheral regio

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

submarine moraines in newfoundland coastal waters implications for the deglaciation of newfoundland and adjacent areas abstract submarine moraines near modern coasts of newfoundland show regional variations in architecture off the west coast arcuate moraines in shallow water were altered to varying degrees by postglacial sea level lowering off the southwest coast arcuate moraines on deep fiord mouth sills interdigitate with glaciomarine deposits whose maximum age is 14 17 ka bp off the northeast coast submarine moraines are absent at the mouths of the deep fiords morainal ridges outside the fiords are coast parallel it is proposed that the moraines formed during deglaciation of the region the late wisconsinan ice sheet extended to the edge of the continental shelf and was divided into catchments with fast flow concentrated in deep channels ice calved back along channels isolating the newfoundland ice cap and ice caps on the offshore banks ca 14 ka drawdown from the interior was localized in fiords and ice margins stabilized just offshore forming the submarine moraines described here off the southwest coasts the ice margin was maintained for up to 1 5 ka at fiord mouths off the northeast coast many of the deep wide fiords are without sills and retreat was nearly continual until the margin stabilized at fiord heads just before 13 ka

crustal evolution of the mid atlantic ridge near the fifteen twenty fracture zone in the last 5 ma author posting american geophysical union 2003 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in geochemistry geophysics geosystems 4 2003 1024 doi 10 1029 2002gc000364

a new late glacial sea level record for st george s bay newfoundland a new relative sea level curve is presented for st george s bay southwest newfoundland based on i a revised stratigraphic framework and depositional model for glacial and marine deposits exposed in coastal sections and ii 19 new radiocarbon dates on shells from emerged and submerged marine deposits including fossiliferous diamictons the data produce a type b sea level curve falling steeply from an extrapolated marine limit of 105 m above sea level at 14 0 14 c ka bp passing below modern sea level at 10 6 14 c ka bp to a lowstand of 25 m at 9 4 14 ck a bp and rising again close to modern sea level by 5 0 14 c ka bp marine limits in the northern part of the bay have lower elevations 27 65 m due to delayed ice retreat of up to 1 2 ka between 12 8 and at least 12 3 14 c ka bp glaciofluvial outwash graded to falling sea levels between 27 and 17 m above present throughout the bay whereas lowstand deltas were constructed in sheltered locations at the outlets of major river systems when sea level was 25 m below present establishment of the sea level lowstand at 9 4 14 c ka bp is supported by new seismic data and radiocarbon dates from st george s bay and also from white bear bay on the south coast of newfoundland short term fluctuations in emergence rates of 1 2 m century between 12 5 and 9 5 14 c ka bp are attributed to variable eustatic sea level rise superimposed on a declining local glacio isostatic adjustment

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

lower limit of hydrocarbon generation in source rocks a case study from the dongpu depression bohai bay basin east china abstract with the increasing demand for hydrocarbons exploration tends to be deeper and unconventional resources however whether there are the lower limits for exploration depth or thermal maturity ro appears to be particularly essential it is of considerable significance to determine the lower limit of hydrocarbon generation llhg since this limit can provide guidelines for hydrocarbon potential estimation according to the mechanisms of hydrocarbon generation and expulsion five methods are combined to determine and verify the llhg whose values can be expressed by llhg ro and llhg h source rock samples from the paleogene shahejie formation es in the dongpu depression were taken as an example to determine the llhg and then controlling factors of the llhg were discussed llhg ro values for es range from 3 23 to 3 97 average 3 71 and llhg h values range from 5244 m to 5525 m average 5433 m regionally llhg values display obvious differences between the northern and southern of depression llhg values in the north are roughly larger than those in the south in the northern depression the llhg ro values are ranging from 3 61 to 3 97 average 3 81 and llhg h values are ranging from 5415 m to 5545 m average 5488 m however in the southern part the llhg ro values range from 3 20 to 3 74 average 3 48 and the llhg h values range from 5265 m to 5375 m average 5278 m the main controlling factors for llhg diversity between the north and the south of depression are organic matter om type and abundance formation temperature and pressure

experimental study on the pressure dependence of vitrinite maturation we conducted the first systematic experiments over a pressure range of 0 5 to 20 0 kbar at temperatures of 200 to 350 c and run durations of 2 4 and 7 days to investigate the influence of pressure on vitrinite reflectance the data indicate that applied pressure lowers vitrinite reflectance the suppression appears to be stronger under wet than under dry conditions in addition high pressure favors liptinite preservation at temperatures 300 c whereas at the same temperature range yet at low pressure liptinite is decomposed our data fit an empirical rate equation which expresses rr as a function of pressure temperature and time the derived equation satisfactorily describes our experiments and enables extrapolations to geological timescales values of rr calculated for a pressure of 0 5 kbar are remarkably consistant with previous numerical pressure independent models a literature review shows that previous experimental data and field observations are inconsistent regarding the effect of pressure on vitrinite maturation this and some previous studies suggest that vitrinite maturation is suppressed by increased pressure whereas other workers regarded pressure as having little influence on the rate of coalification we suggest that original virinite composition experimental design and natural environment tectonic regime play important roles regarding the effects of pressure on vitrinite maturation interpretation of geothermal histories of sedimentary rocks based on vitrinite reflectance data must therefore include evaluation of the pressure otherwise vitrinite reflectance data from high pressure terranes should be interpreted with caution if used as a quantitative paleogeothermometer

late glacial stratigraphy and history of the gulf of st lawrence reply the three dimensional configuration of the quaternary sediments in the gulf of st lawrence is described based on analysis of 8000 km of high resolution seismic reflection data complemented by anal

present temperature field and cenozoic thermal history in the dongpu depression bohai bay basin north china abstract the dongpu depression is located in the southern bohai bay basin north china and it has abundant oil and gas reserves there has been no systematic documentation of this depression s temperature field and thermal history in this article the present geothermal gradient and heat flow were calculated for 68 wells on the basis of 892 formation testing data from 523 wells moreover the cenozoic thermal history was reconstructed using 466 vitrinite reflectance data from 105 wells the results show that the dongpu depression is characterized by a medium temperature field between stable and active tectonic areas with an average geothermal gradient of 34 8 c km and an average heat flow of 66 8 mw m2 the temperature field in the dongpu depression is significantly controlled by the changyuan huanghe and lanliao basement faults and thin lithosphere thickness the geothermal gradient twice experienced high peaks one peak was during the shahejie 3 formation depositional period ranging from 45 c km to 48 c km and the second peak was in the middle and late of the dongying formation depositional period ranging from 39 c km to 40 c km revealing that the dongpu depression experienced two strong tectonic rifts during the geothermal gradient high peak periods the geothermal gradient began to decrease from the neogene and the geothermal gradient is 31 34 c km at the present day in addition these results reveal that source rock thermal evolution is controlled by the paleo temperature field of the dongying formation depositional period in the dongpu depression this study may provide a geothermal basis for deep oil and gas resource evaluation in the dongpu depression

impact of hydrocarbon expulsion efficiency of continental shale upon shale oil accumulations in eastern china abstract core samples were taken from two formations the qingshankou formation in northern songliao basin and the third member of the shahejie formation of zhanhua sag to carry out a study of impact of hydrocarbon expulsion from continental shale upon shale oil accumulations in eastern china total organic carbon toc and pyrolysis data of these samples were used to establish an evaluation criterion with absolute and relative oil content indexes for determining oil potential of shale as a result a correspondence relationship between shale oil content and organic types was established factors that may affect oil content of shale were discussed through study of fractures pore development minerals and lithological assemblage of the samples the results show that oil content of mature petroleum source rocks is firstly controlled by fracture growth and secondly by pore development they played both negative and positive roles in hydrocarbon flow and accumulation in shale overpressure caused by hydrocarbon generation and existence of organic acid corrosion are two important factors affecting the formation of fractures and pores in shale respectively intervals with type i organic matter are not favorable shale oil exploration targets because they contain little oil shale with type i organic matter tends to generate large amount of hydrocarbon but these hydrocarbon will escape with a high efficiency through over pressurized fractures caused by hydrocarbon generation and lack of pore space which in turn is the result of absence of oxygen that is essential for forming organic acid to create secondary pores in shale on the contrary intervals with type ii organic matters are potential shale oil exploration targets for that they offered just right conditions for oil to stay inside higher content of oxygen that is helpful in forming organic acid moderate hydrocarbon generation capacity that will not cause over pressurized fractures in shale with secondary pores while intervals with type iii organic matter bear no exploration significance due to the fact that this type of kerogen produces less oil because of low hydrocarbon generation capacity and unfavorable molecular configuration shale intervals with thin sandstone interbeds provide favorable passageways for dissolved carbonate by organic acid to flow out avoiding secondary precipitation the pores left behind can be excellent space for generated hydrocarbon to linger around these interbeds are also favorable for later reservoir stimulation measures such as hydraulic fracturing shale oil exploration shall be focused on finding sweet spots with greater pores which are the main reservoir space

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

late quaternary sedimentation in st george s bay southwest newfoundland acoustic stratigraphy and seabed deposits shallow seismic reflection data collected in st george s bay southwest newfoundland reveal a complex pattern of subsurface topography and acoustic facies two basins in the inner bay are underlain by glacially overdeepened valleys that extend to depths in excess of 180 m within the thick quaternary sequence in the inner bay we recognize eight acoustic units units 1 ice contact 2 subaqueous outwash and 3 draped glaciomarine record the presence and retreat of a major late wisconsinan ice margin unit 4 postglacial mud has resulted from reworking of glaciogenic sediments in response to changes in relative sea level unit 5 postglacial sand is a shoreface deposit on the seaward front of the former moraine unit 6 postglacial delta was formed by fluvial reworking of glaciogenic sediments during the postglacial lowstand of relative sea level unit 7 postglacial barrier platform comprises seaward fining clinoform prisms that have prograded into the basins and underlie gravel beach ridge pla

correlation of natural gas by use of carbon isotopic distribution between hydrocarbon components the natural distribution of carbon isotopes between hydrocarbon gas components is used for 1 determining a gas s maturity 2 correlating a reservoired gas to its source 3 correlating one reservoired gas with another and 4 recognizing gas mixtures calculated separations of carbon isotopes between the normal alkane components of a natural gas have been related to source rock maturity by use of a single continuous diagram independent of source type actual data from a wide variety of geologic settings and geologic ages confirm this relationship and demonstrate its applicability to the source rock levels of organic metamorphism ranging from 8 to 13 covering the entire range of oil and wet gas generation at greater maturities the wet gas components are found to undergo thermal degradation losing their usefulness for correlation three examples showing indigenous gas west texas non indigenous gas gippsland basin australia and gas mixtures from multiple sources southeastern alberta illustrate exploration applications

atomic h c ratio of kerogen as an estimate of thermal maturity and organic matter conversion in recent years the atomic h c hydrogen to carbon ratio of kerogen as a way to assess the quality of organic matter in source rocks has been overlooked in favor of the more easily determined rock eval hydrogen index rock eval pyrolysis provides fast inexpensive quantitative mg hc g rock data without requiring kerogen isolation from the rock because of the general scatter in the data many source rock interpreters consider rock eval pyrolysis to be a screening analysis in this paper i describe the benefits of using h c ratios in source rock evaluations and present new correlations between atomic h c ratios and thermal maturity organic matter conversion and expulsion volumetrics atomic h c ratios of pyrolyzed kerogens have been correlated to the extent of thermal conversion of organic matter for both type i and type ii kerogens the excellent agreement between stoichiometric calculated hydrogen and carbon loss to observed losses from hydrous pyrolysis maturation experiments suggests that kerogen h c ratios are excellent indicators of thermal maturity for end member kerogen types these data also offer a method to estimate percent organic matter conversion provided that both the initial and present h c ratios of the kerogen are known present h c ratios can be measured and initial h c ratios can be reasonably estimated from microscopic organic analysis of kerogen for oil prone source rocks typical immature type i kerogens have h c ratios of 1 35 1 50 whereas type ii kerogens have h c ratios of 1 20 1 35 correlations of the amount of expelled oil in hydrous pyrolysis experiments to atomic h c ratio of the spent kerogen offer exploration geologists a quick estimate of oil expulsion volumes based on hydrous pyrolysis experiments measured h c ratios and calculated original toc total organic carbon values first order volumetric approximations were made on three basins containing mature source rocks results compared favorably with published approximate oil in place estimates for the williston basin bakken shale los angeles basin nodular shale and the illinois basin new albany shale

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

petroleum resources in the nanpu sag bohai bay basin eastern china the nanpu sag is an important secondary tectonic division of the bohai bay basin and has an area of 1532 km2 591 mi2 of which 1000 km2 386 mi2 has been explored near bohai recently exploration has gradually shifted from continental to beach to shallow marine settings with significant exploration breakthroughs having occurred in the nanpu 1 2 and 3 tectonic belts indicating good resource potential however a systematic resource assessment has yet to be performed which strongly restricts the exploration progress in this study we improved upon the pareto model and reevaluated the area s resource potential using two new methods in one method the traps are divided into several types including structural stratigraphic and buried hill traps to predict their individual resource potential and total resources of this area in the other method the normalized fluid potential is used to divide the area into several accumulation systems to calculate the resource potential the nanpu sag resources are estimated at 1 45 109 t 10 6 109 bbl which represents an increase of approximately 2 70 108 t 19 8 108 bbl compared with previous evaluations because of the increase in exploration maturity and information validation the main residual resource is distributed in beach to shallow marine settings the stratigraphic and buried hill traps present better resource potential using the trap type method such information can guide the direction of exploration and selection of potential traps

shale oil occurring between salt intervals in the dongpu depression bohai bay basin china abstract the saline mudstone sequence of the paleogene shahejie formation in the dongpu depression of bohai bay basin is a major source rock for conventional hydrocarbons however shale oil having a density of 0 9 g cm 3 and a viscosity of 21 mpa s has also been discovered and is being produced from these mudstones to better understand the occurrence of such shale oil geochemical petrological and mineralogical investigations were carried out on a suite of saline mudstone samples by using rock eval x ray diffraction and sem the shahejie formation samples analyzed in the current study are characterized by type ii kerogen with lesser amounts of types i and iii such that petroleum generation ranges from fair to excellent in general terms with the exception of es1 uppermost member which is immature to marginally mature for oil generation the sequence studied ranges from mature for oil generation to mature for wet gas generation on the basis of vitrinite reflectance data the most prospective depths for shale oil condensate generation are between 2300 and 4000 m depth in area studied the saline mudstones comprise mainly clay minerals followed by carbonates quartz and feldspar based solely on the brittle mineral index the amounts of carbonate and quartz in many of the samples lead to a similar or greater suitability for hydraulic fracturing than for many haynesville woodford and upper bakken shales sem studies show that abundant micro fractures commonly occur in the mudstones and these include tectonic fractures bedding plane fractures shrinkage fractures and over pressured fractures for the es3 m middle third member unit shale oil prospectivity is likely to be enhanced around the towns of wl wenliu lt liutun and hbz hubuzhai due to the increased frequency of tectonic fractures which would contribute to oil storage and flow mineral interparticle mineral intraparticle and organic matter pores are well developed in the rocks studied mineral dissolution has created secondary pores in some areas such that reservoir capacity is increased the increased concentration of organic acids between 2800 and 3500 m is likely to lead to enhanced shale oil prospectivity the micro fractures and dissolution pores are probably the main reservoirs for shale oil accumulation the association of these features with saline facies potentially offers an exploration tool for further shale oil occurrences in the studied area as well as in other areas containing similar lithologies

geology of china and adjacent regions an introduction abstract this introduction outlines the papers collected in the special issue geology of china and adjacent regions the papers focus on scientific issues from archean to cenozoic geology in the areas including northwest pacific to western central orogenic belt concerning tectonics geophysics petrology geochemistry mineral deposit and energy resources a tectonic framework of china and adjacent regions is briefly introduced

barriers barrier platforms and spillover deposits in st george s bay newfoundland paraglacial sedimentation on the flanks of a deep coastal basin abstract st george s bay and adjacent coastal areas of southwest newfoundland contain thick sequences of late quaternary glaciogenic sediments and have been subject to relative sea level fluctuations over a rang of 70 m during the past 13 5 ka glaciogenic sediments have been mobilized by littoral processes to form two types of deposits these are 1 the prograded barrier beach and spit at stephenville and flat island respectively which are associated with large subaqueous sandy platforms and 2 a wedge of well stratified sand and gravel on the landward flank of the shallow sill which extends across st george s bay at an average depth of about 25 m the subaerial barriers and spits are composed of gravel beach ridges overlain locally by thin aeolian deposits with freshwater and salt marsh peats in swales these barriers developed during the last several thousand years as relative sea level approached its present position from an early postglacial minimum of approximately 25 m the prerequisite for beach ridge formation was the deposition of large sandy subaqueous platforms which appear on shallow seismic reflection records as clinoform wedges prograded into the deep basin of inner st george s bay the barrier platform at stephenville is constructed across a deep submarine valley the flat island barrier platform sits on the flank of a glacially overdeepened trough partly filled by glacial and postglacial sediments and envelops a delta formed during the early postglacial low stand of relative sea level the platform and barrier together constitute a thick coastal sequence coarsening up from sandy mud at the base to gravel at the top the wedge of well stratified coarse sediment up to 50 m thick situated on the landward flank of the shallow sill overlies older glaciogenic sediments and passes laterally into postglacial basin muds steep foreset reflections dipping 10 20 are evident on shallow seismic reflection records suggesting that the wedge was formed by spillover of sediment entrained by wave and current action into the relatively deep basins of the inner bay active gravel ripples testify to the continued mobility of coarse sediment on the sill the formation of the spillover deposits barriers and platforms demonstrates the potential for glacially overdeepened basins to host thick heterogeneous coarse grained coastal and inner shelf deposits

the influence of pressure on petroleum generation and maturation as suggested by aqueous pyrolysis because fluid pressures are transient in sedimentary basins over geologic time the effect of increasing fluid pressure on organic matter metamorphism is difficult to determine and conflicting opinions exist concerning its influence properly performed aqueous pyrolysis experiments can closely simulate hydrocarbon generation and maturation in nature and thus offer an excellent way to study the influence of pressure such experiments carried out on the retort phosphatic shale member of the lower permian phosphoria formation type ii s organic matter at different constant temperatures demonstrated that increasing pressure significantly retards all aspects of organic matter metamorphism including hydrocarbon generation maturation and thermal destruction this conclusion results from detailed quantitative and qualitative analyses of all products from hydrocarbon generation from the c1 to c4 hydrocarbon gases to the asphaltenes and also from analyses of the reacted rocks we have documented that our aqueous pyrolysis experiments closely simulated natural hydrocarbon generation and maturation thus the data taken as a function of pressure have relevance to the influence of normal and abnormal fluid pressures as related to 1 depths and temperatures of mainstage hydrocarbon generation 2 the thermal destruction of deposits of gas or light oil or their preservation to unexpectedly high maturation ranks and 3 the persistence of measurable to moderate concentrations of c15 hydrocarbons in fine grained rocks even to ultra high maturation ranks

compound specific sulfur isotopes of saline lacustrine oils from the dongpu depression bohai bay basin ne china abstract lacustrine oils from type i ii kerogen from the dongpu depression of bohai bay basin have been characterised by compound specific sulfur isotope and hydrocarbon biomarker analyses the sample suite included sixteen saline lacustrine oils from the northern part of the dongpu depression most of which i e all but two interbedded samples could be separated into four tectonically aligned oil families of1 4 on the basis of differences in their hydrocarbon composition e g high mw n alkanes isoprenoids polycyclic terpenoids the other two oils studied were freshwater lacustrine oils from the south of the dongpu depression the hydrocarbon composition of which indicated a fifth oil family of5 the 34s values of organic sulfur compounds 34soscs in the oils showed several general differences consistent with the five hydrocarbon biomarker defined oil families including the relative magnitude of their 34s values ave 34soscs values of1 19 relatively depleted 34s of2 28 enriched 34s of3 24 intermediate 34s of4 25 intermediate 34s and of5 18 depleted 34s and the respective 34soscs profiles of the oils e g the intermediate 34s values of the lt oils of3 showed little variance with alkylation

recent advances in petroleum geochemistry applied to hydrocarbon exploration this paper presents a critical review of recent advances in the study of generation maturation and migration of petroleum the different source potentials for generating hydrocarbons depend on the type of kerogen in addition to the classic types i ii and iii a residual oxidized organic matter is also observed which has no potential for hydrocarbon generation coal is widely considered as a potential source for gas but some coals may generate sizeable amounts of oil as well the development of routine analytical tools particularly pyrolysis makes possible the preparation of geochemical logs that are the basis for screening samples and for interpreting other analyses among optical techniques the major subjects of discussion concern the nature of amorphous organ c matter which may encompass different chemical types of kerogen and the applicability of vitrinite reflectance techniques to type i and ii kerogens following important advances in identification of biological markers in sediments and crude oils these markers are used for oil source rock correlation and proposed for reconstruction of depositional environment and subsequent thermal evolution migration of hydrocarbons is now better understood and the importance of a hydrocarbon phase migration is widely recognized overpressuring of pore fluids is mainly responsible for expulsion of petroleum geologic models of basin evolution subsidence compaction thermal history and geochemical models hydrocarbon generation and migration become progressively available their integration int a comprehensive model should be one of the major developments in future petroleum exploration

evaluating the influence of tidal currents on the distribution of silt in nara inlet central great barrier reef australia a simple model is developed to infer flood tide dispersal of silt during fair weather conditions from spatial grain size variation of mixed carbonate siliciclastic silt on the bed of nara inlet a 3 km long shallow tropical embayment on the mid shelf of the central great barrier reef region australia the model uses settling velocities calculated for three dominant silt modes 23 28 and 41 m and measured tidal current data to predict the headward transport of silt by a large flood tide modelling was aided by the use of wind and currents 2000 wc2000 freeware a visualisation and analysis tool for vectorial data the model predicts the 23 28 and 41 m modes will be transported minimum headward distances of 1250 950 and 500 m respectively and compares well with the observed silt distribution on the bed the results indicate that under fair weather conditions flood tides control the distribution of silt consistent grain size trends of bulk and siliciclastic silt implies that siliciclastic and carbonate silt sized grains may exhibit similar hydraulic behaviour during transport by flood tides in nara inlet the model may be applied to embayments where fine sediment transport is dominated by flood tides it may also have application in identifying the controls on dispersal and accumulation of particle associated contaminants in embayments characterised by mixed carbonate and siliciclastic sediments

quantitative evaluation of potential organic matter porosity and hydrocarbon generation and expulsion from mudstone in continental lake basins a case study of dongying sag eastern china abstract this study presents approaches for evaluating potential organic matter porosity and hydrocarbon generation and expulsion in mudstone with strong heterogeneity in organic matter distribution in different evolution conditions of continental lake basins a total of 274 samples from the paleogene system at depth of 2770 3376 m of the niu 38 well in dongying depression eastern china were analyzed based on rock eval pyrolysis to investigate the corresponding potentials of organic matter porosity and hydrocarbon generation and expulsion the study shows that organic matter type controls hydrocarbon generation and expulsion potential in the continental lake basin strong heterogeneity was observed in the total organic carbon distribution among different organic matter types thus leading to significant gaps in hydrocarbon generation and expulsion potential type i organic matter exhibits high hydrocarbon generation and expulsion potential which is distributed within 24 07 105 79 mg g rock generation and 6 67 74 32 mg g rock expulsion with an average of 44 2 mg g rock and 18 91 mg g rock respectively types iii and ii 2 organic matter exhibit limited hydrocarbon generation and expulsion potential particularly type iii the hydrocarbon generation and expulsion potential of types iii and ii 2 organic matter is only distribute within 0 67 2 67 mg g rock generation and 0 32 1 20 mg g rock expulsion respectively thus indicating that these types are basically inert organic matter results show that type i organic matter with an initial total organic carbon content ranging from 6 28 to 22 0 can generate potential organic matter porosity varying from 4 15 to 26 21 capability to generate potential organic matter porosity decreases significantly from type i to types ii 1 ii 2 and iii organic matter initial total organic carbon is only within the range of 0 76 1 47 and potential organic matter porosity is between 0 10 and 0 41 for type iii organic matter the result shows that the potential organic matter pores generated by different organic matter types exhibit considerable differences between the samples in the continental lake basin the described methodology in this work allows a higher resolution in the evaluation on the heterogeneity of hydrocarbon source rock in vertical sequence thus it is an important way in the evaluation of potential source rock in the early exploration of unconventional oil and gas resources in the mudstone

differential preservation of coastal structures on paraglacial shelves holocene deposits of southeastern canada abstract recent work has advanced our understanding of mixed sand gravel littoral systems in glaciated regions new insights include the nature and causes of coastal instability and conditions for preservation of holocene barrier deposits on paraglacial shelves the best preserved relict barrier structures recognized on the inner shelf of southeastern canada are interpreted as postglacial lowstand deposits initiated under stable to slowly rising relative sea level in areas of substantial shelf relief a largely intact early holocene gravel foreland survives at 38 m present water depth its preservation attributed in part to sediment volume and a partially protected location the mechanism by which this structure was abandoned and overstepped is unclear but may be related to accelerating sea level rise in some cases barriers keep pace with sea level rise for some time before being overstepped or reworked landward the duration and extent of preservation depend in part on the deposit volume as smaller accumulations are consumed and reworked more quickly deposit volume is a function of sediment supply accommodation space and headland spacing among other factors where barriers are small and thin beach sediments overtaken by the transgression may be smeared across the shoreface in a thin post transgressive veneer in such settings as along the eastern shore of nova scotia the only coastal units preserved on the shelf are back barrier estuarine facies in flooded valley depressions differential preservation is governed by shelf relief and accommodation space coastal alignment and compartmentalisation sediment supply and barrier volume rate and acceleration of sea level rise wave energy and potential for sediment reworking on the inner shelf

late wisconsinan stratigraphy and chronology at highlands southern st george s bay southwest newfoundland abstract this paper provides detailed sedimentological and chronological data of coastal exposures at highlands in southern st george s bay southwest newfoundland the highlands section shows a coarsening upward sequence from mud to sand and gravel and diamicton and represents an ice distal to ice proximal glaciomarine environment where sediment was introduced via a subglacial meltwater jet and deposited by underflow current flow debris flow and overflow on a grounding line fan diamicton forms a continuous unit along the top of the section grading laterally from structureless to stratified and has characteristics of subglacial sediment gravity flow and rainout depositional processes at one site a fossiliferous diamicton is interpreted to be deposited by rainout through a combination of suspension settling from meltwater plumes and ice rafting with subsequent modification by sediment gravity flow on the fan slope a radiocarbon date of 13 680 90 bp beta 120124 on paired shells from this diamicton is interpreted to represent the date of its emplacement this date lies within the range of all other dates 13 1 14 ka bp on marine organisms from sediments along the coast of southern st george s bay and suggests that deposition of the diamicton was contemporaneous with sedimentation in all areas along the coast evidence to support a previously interpreted late glacial readvance at 12 6 ka bp was not found