drimane type compounds in source rocks and fluids from fluvial deltaic depositional settings in the north west shelf of australia abstract fluvial deltaic petroleum systems with gas prone source rocks are difficult to assess because the released fluids generally lack biomarkers and this limits the implementation of traditional organic geochemistry screening however there are a number of compound classes yet to be investigated in order to establish novel parameters for correlation studies in fluvial deltaic geological settings in this study we have focused on drimane skeleton molecules c15 decalins particularly the compounds 1 2 2 5 5 pentamethyl trans decalin and 1 1 2 5 5 pentamethyl trans decalin termed herein as rearranged drimanes rd1 and rd2 respectively and drimane d in source rock extracts and fluids from fluvial deltaic petroleum systems in the carnarvon basin north west shelf of australia nws we have calculated the ratio rd1 rd2 d as proposed by ji et al ji l he c zhang m wu y li x 2016 bicyclic alkanes in source rocks of the triassic yanchang formation in the ordos basin and their inconsistency in oil source correlation marine and petroleum geology 72 359 373 and compared their results with samples from the nws our compilation of rearranged drimane ratios for a variety of lithologies suggests clay catalysed rearrangement of c15 decalins in siliciclastic source rocks from fluvial deltaic depositional environments therefore the mineral content seems to be a key factor controlling the isomerisation of decalins samples with higher clay content such as claystone from the brigadier formation have higher rd1 rd2 d ratios 6 and higher c29 diasterane c29 sterane 1 1 compared to silty claystone from the legendre formation 2 and 0 8 respectively the effects exerted by thermal maturity of the source rock and redox conditions of the depositional environment require further investigation although samples from the yanchang fomation and la luna formation where deposition occurred under more reducing conditions exhibit lower rearranged drimane ratios

australasian asphaltite strandings their origin reviewed in light of the effects of weathering and biodegradation on their biomarker and isotopic profiles abstract asphaltites long known to strand along the coastline of southern australia and as distantly as new zealand and macquarie island are widely regarded as artefacts of submarine oil seepage their remarkably uniform composition suggests a common source marine shale containing sulphur rich type ii kerogen probably deposited during an early cretaceous oceanic anoxic event oae suitable hydrocarbon kitchens may exist in the offshore bight and otway basins the physical character of the asphaltites including laminations and flow structures and their degree of alteration which is not the result of biodegradation or extensive water washing suggest an origin from subsurface tar mats subsequently exposed by the incision of submarine canyons with the possible formation of asphaltic volcanoes api gravities of 4 18 impart quasi neutral buoyancy implying many asphaltites were submerged drifters prior to stranding their degree of weathering reflecting at least in part the residence time in the marine environment for any individual asphaltite specimen this will depend on the proximity of the seafloor seep to the stranding site an important consideration when attempting to locate their point of origin this study investigates the hydrocarbon biomarker signatures and n alkane 13 c profiles of asphaltite specimens from stranding sites on the eyre peninsula n 2 kangaroo island n 4 and the limestone coast n 3 south australia and the south island of new zealand n 2 sub samples of the interior and weathered surface of each specimen were analysed no distinction could be made between strandings based on their source dependent molecular and isotopic signatures confirming their common origin comparison of the interior and exterior sub samples revealed subtle although consistent differences given their degree of degradation and isotopic variance these australasian asphaltites seem to be products of low intensity seeps in the ceduna sub basin of the bight basin and or morum sub basin of the otway basin

diagenetic behavior of barite in a coastal upwelling setting 1 multiproxy data from odp hole 1017e point conception california provide an excellent opportunity to examine the behavior of barium within a well characterized sedimentary system bariumexcess is generally considered to be a productivity proxy however in nearshore environments baexcess records can be compromised by both sediment provenance and barite remobilization for the last 60 kyr odp hole 1017e exhibits significant changes both in primary productivity driven by coastal upwelling and in the sediment redox chemistry of underlying sediments significant barite enrichment occurs at an active diagenetic front that marks the boundary between sulfate rich and sulfate poor pore waters this boundary also intersects a sediment facies change from deposition of relatively coarse grained sediment before 35 ka to an interval of fine grained organic rich sediment after i e interstadial event 8 changes in diffusion rates associated with the sediment facies change cause a strong but misleading correlation between a mobile zone of barite enrichment and rapid climate change thus within the baexcess record at odp hole 1017e is a history of redox chemistry that has corrupted the paleoproductivity record of babiogenic

an experimental study of crude oil alteration in reservoir rocks by water washing abstract the objective of this research was to establish the effect of water washing on the physical and chemical properties of crude oils to simulate water washing under reservoir conditions crude oil was washed in sandstone and limestone cores by as much as 240 liters of a degassed bacteria free water over a period of up to 149 days at 90 c 194 f under a confining pressure of 138 bars 2000 psi in a flow through core holder unit the water washed oils were recovered by soxhlet extraction compared to the original oils water washed oils show lower api gravities lower concentrations of light aromatic compounds such as phenanthrene and dibenzothiophene lower metal and sulfur content lower light paraffins with respect to heavy paraffins and isoprenoids more negative stable carbon isotopic ratios for the nso fraction lower diterpane content relative to triterpane content lower c 27 steranes relative to c 30 hopane and 4 methyl sterane and altered bicyclic alkane and aromatic steroid biomarkers oils washed in limestone cores show a more severe reduction in api gravity and loss of aromatics than those in sandstone cores these changes can be used to discern the effects of water washing from those caused by biodegradation deasphalting and maturation of related crude oils diterpane triterpane and sterane biomarkers are little affected by water washing and therefore can be used to correlate water washed oils with related unaltered oils and source rocks and to assess the depositional environments of the source rocks for the water washed oils although these experiments did not produce tarmat tarmat formation by water washing over geological time cannot be ruled out the api gravity sulfur and metal content of oils may be reduced by water injection

molecular measurements of maturity for lias δ shales in n w germany abstract the extractable aliphatic and aromatic hydrocarbons of twenty four lias shales from n w germany have been analysed by gas chromatography mass spectrometry particular attention has been paid to seven molecular measurements of thermal maturation which are based on appropriate ratios of the concentrations and products of certain reactions a sequence of increasing maturity towards the area of the bramscher massiv was determined because the reactions involved occur at different rates they reach completion at different levels of maturity and at variable distance from the centre of the bramscher massiv as defined by iso vitrinite reflectance contours reported previously for rhaetic lias and malm shales this has allowed the designation of zones of increasing maturity the molecular measurements appear more reliable assessors of maturity than vitrinite reflectance for samples less mature than the zone of oil generation but are not applicable to samples from within this zone because the reactions concerned have normally reached completion a mathematical model suggests that the maturity of samples less mature than a vitrinite reflectance of 1 can adequately be explained by substantial subsidence during early and middle cretaceous followed by major uplift and inversion in late cretaceous time without recourse to further heating from a deep seated igneous intrusion

effects of storm duration and oblique wave attack on open filters underneath rock armoured slopes abstract underneath rock slopes of rubble mound structures often one or more granular filter layers are present these filter layers prevent base material washout in contrast to traditional filters geometrically open filters allow for some movement of base material in order to design such open filters the amount of erosion and accretion of base material needs to be predicted based on 2d physical model tests van gent and wolters 2015 presented a method to estimate the erosion and accretion of sand underneath rock slopes since the developed method was only valid for perpendicular wave attack a new study has been performed to assess effects of oblique wave attack on the amount of erosion and accretion of sand underneath a rock slope for that purpose 3d physical model tests were performed in a wave basin with 5 different wave angle between 0 perpendicular wave attack and 75 based on the test results it was shown how the effects of wave obliquity can be taken into account in the design of open filters in addition the effect of the storm duration on open filters has been studied this led to an extended design method to predict the amount of erosion and accretion of sand underneath rock slopes under wave loading

chemical changes of fluid inclusion oil trapped during the evolution of an oil reservoir jabiru 1a case study timor sea australia abstract this study of the jabiru oil field timor sea australia shows how the variability of visual properties of fluid inclusions in palaeo oil zones can be mapped to identify internal structures that result from fluid interactions in the reservoir variability in the attributes of oil inclusion assemblages oias is greater within an inferred palaeo gas cap zone 1 and current residual zone zone 3 and less within the current oil zone zone 2 in zone 3 where water imbibed a higher proportion of oias with visual white fluorescing oil inclusions correlates with less mono aromatic compounds and a higher abundance of polar compounds determined on a bulk extract of inclusion oil using high performance liquid chromatography hplc the ch 2 ch 3 ratios and water contents determined by fourier transform infrared spectroscopy ft ir are higher in zone 1 where gas drained there is a higher proportion of oias with visual yellow fluorescing oil inclusions and these correlate with low hplc mono aromatic and moderate polar contents and low ft ir ch 2 ch 3 ratios and water contents interpretation of the grains with oil inclusions goi and pressure volume temperature composition pvtx fluid inclusion data suggests that a gas saturated blue fluorescing palaeo oil was present in the three zones at the same pressure temperature fluid inclusion forming event pt 1 lighter gas saturated blue fluorescing oil was present in zone 2 but was rarer in zones 1 and 3 at the later fluid inclusion forming event pt 2 the yellow and white inclusion oils trapped in zones 1 and 3 respectively are gas depleted and interpreted to result from the interaction between non movable residual oil around grains with the surrounding gas and water respectively comparison between the pvtx data and the published burial curve suggests that most of the fluid inclusions were trapped during two different hot fluid flow events the full oil column is interpreted to have been present during early mid tertiary the palaeo oil column was reduced during the late miocene by imbibition of water in the present residual zone and drainage of gas at the top of the reservoir

water washing of proterozoic oil in the midcontinent rift system whole oil gas chromatography shows that petroleum inclusions trapped in 1 05 ga veins in the midcontinent rift experienced variable water washing but no significant biodegradation or phase separation by comparing our results with published experimental data we estimate that water petroleum ratios varied from 200 1 to much greater than 9000 1 extreme water washing with water petroleum ratios very much greater than 9000 1 likely produced pyrobitumen solid hydrocarbon that was locally trapped as primary inclusions in vein calcite hydrothermal ore deposits with their extremely high water rock ratios are one of the best places to search for end member water washed petroleum sedimentary basins however with their variable water rock ratios also have a wide range of water petroleum ratios which significantly affect the composition of crude oils along the flow path between source rock and trap water petroleum ratios may be a useful concept to help evaluate crude oil compositions in a variety of settings

physical model of scour at the toe of rock armoured structures abstract toe structures are a common feature in coastal rock armoured structures both safeguarding the structure against scour at the toe and providing support to the armour layer the toe structure itself is often comprised of rocks as well hence generally some form of scour protection such as a filter layer or a geotextile is applied underneath the toe structure currently there is a lack of available methods to judge the necessity of these kinds of costly scour protection measures underneath the toe structure in this paper a unique data set from physical model tests of scour at the toe of rock armoured structures is presented the bed level change is measured by a laser scanner across the entirety of the sand bed including underneath the structure additionally the temporal development of the scour at the glass wall of the flume is measured using an innovative combination of video imagery and a deep learning algorithm the sand diameter is not varied in the physical model tests in all tests scour was observed both in front of the structure and underneath the structure two expressions have been derived that give estimates for both kinds of scour and thus can give insight into the necessity of scour protection underneath the toe structure

mixing and biodegradation of hydrocarbons in the daerqi oilfield baiyinchagan depression northern china abstract crude oils in the daerqi oilfield vary greatly in viscosities including normal viscous and highly viscous oils they are also dramatically different in thermal maturity from immature to mature based on biomarker parameters according to bulk and molecular geochemical characteristics crude oils can be classified into three groups in this oilfield group i oils are mature and derived from the deeply buried and relatively old source rocks within the tengger formation and the second member of the arshan formation of early cretaceous age group ii oils are immature to marginally mature and derived from the relatively young source rocks that experienced shallow burial within the first member of the duhongmu formation of earlier cretaceous age group iii oils are mixtures of group i and group ii oils with dominance of the group i oils 70 the viscosity is low for the non biodegraded group i and group iii oils 7 1 24 mpa s but very high for the non biodegraded group ii oils e g 433 104 mpa s for the representative oil da12o1 the group iii oils are similar to the group i oils in gross properties e g gross composition and viscosity but are similar to group ii oils in terms of their molecular maturity parameters the oil reservoirs are currently at a shallow depth

numerical modelling of the erosion and deposition of sand inside a filter layer abstract this paper treats the numerical modelling of the behaviour of a sand core covered by rocks and exposed to waves the associated displacement of the rock is also studied a design that allows for erosion and deposition of the sand core beneath a rock layer in a coastal structure requires an accurate prediction method to assure that the amount of erosion remains within acceptable limits this work presents a numerical model that is capable of describing the erosion and deposition patterns inside of an open filter of rock on top of sand the hydraulic loading is that of incident irregular waves and the open filters are surface piercing due to the few experimental data sets on sediment transport inside of rock layers a sediment transport formulation has been proposed based on a matching between the numerical model and experimental data on the profile deformation inside an open filter the rock layer on top of a sand core introduces a correction term in the exner equation the continuity equation for sediment and change in bed level the correction term originates from the fact that the sand can only be deposited in the pores of the filter material the numerical model is validated against additional data sets on the erosion and deposition patterns inside of an open filter a few cases are defined to study the effect of the sinking of the filter into the erosion hole the numerical model is also applied to several application cases the response of the core material sand to changes in the wave period and wave height is considered the effect of different layouts of the filter is studied in order to investigate the effect of different filter profiles on the resulting erosion finally it is studied how much the design of a hydraulically closed filter can be relaxed to obtain a reduction in the design requirements of the filter thickness while the deformation to the sand core remains acceptably small

bicyclic alkanes in source rocks of the triassic yanchang formation in the ordos basin and their inconsistency in oil source correlation abstract the triassic yanchang formation is the main source rocks for mesozoic oil in ordos basin the formation includes 10 oil bearing beds ch 1 ch 10 that each can be further divided into two to three intervals abundant c12 c14 and c15 c16 bicyclic alkanes have been detected in the formation in the xifeng oilfield ordos basin the c12 c14 group is dominated by c12 and c13 and the c15 c16 group contains abundant c15 the groups show three distribution patterns a the c12 c14 group is the major component in the non source rocks of the ch 7 1 and ch 8 1 intervals b both groups are abundant and are common in source rocks of the ch 7 3 interval and c the c15 c16 group is the major component in source rocks of the ch 7 3 interval and also in sediments that contain type or partial sapropel type 1 organic matter om in the ch 7 2 and ch 8 1 intervals although thermal maturities of the source rocks in the ch 7 section are similar they show significant differences with respect to the drimane isomerisation index which indicates that the drimane rearrangement is controlled by thermal evolution of the sediments but may also be closely related to the depositional environment this study determined that reducing environments are more conducive to preservation of drimane than oxic environments the drimane isomerisation index and the value of the hopane parameter tm ts are positively correlated the parameter tm ts varies over a wide range within the sequence and the large variations may be a result of terrigenous om input by turbidity currents and or gravity flows mixed with the autochthonous sediments abundant homodrimane in both source rocks may reflect reducing environments in deep lakes and major input of higher plant om organic rich shale and oil shale in the ch 7 3 interval of the yanchang formation are the primary sources of oil in reservoirs in the xifeng area the crude oil is rich in bicyclic alkanes that are dominated by c15 c16 as source rocks with pattern c for bicyclic alkanes which indicates an origin mainly from the ch 7 3 interval the main peaks in all of the crude oils are associated with 8 h drimane and lower abundance of rearranged drimane however most of the source rocks have a main peak associated with 8 h homodrimane or rearranged drimane weak microbial action selective degradation and water washing may be the cause of the significant difference in bicyclic sesquiterpane composition between the crude oil and the source rocks the result suggests that oil source correlations based on the bicyclic sesquiterpanes are questionable

granular slopes with open filters under wave loading abstract permeable hydraulic structures that consist of rock material typically contain granular filters in one or more layers these filters are normally geometrically tight to prevent material washout geometrically tight filters are often difficult to realize in the field and expensive an alternative is a geometrically open filter a geometrically open filter has a large ratio of the size of toplayer material rock and underlayer material e g sand and is designed in such a way that only minimal base material loss or settlement occurs potential applications of open filters include bed protections toe structures and slope protections proper guidelines on the design of open filters under wave loading could lead to significant cost and material savings and to more practical applications of filters in the field physical model tests were conducted in a wave flume of deltares the analysis of the tests with 1 4 and 1 7 slopes and fixed test durations of 3 h

suction removal of sediment from between armor blocks ii waves when a stone armor layer on a sand bed is exposed to flow the sand underneath will be agitated by the flow turbulence when the flow velocity reaches a critical value the sand will be sucked winnowed out from between the armor blocks in a previous investigation we studied suction removal of sediment in steady currents the present study is an extension of our previous investigation to waves the critical condition for the onset of suction is determined it is found that the onset of suction is governed by three parameters 1 the sediment mobility number based on the sediment size 2 the ratio of sediment size to stone size d d and 3 the keulegan carpenter kc number based on the armor block stone size the variation of the critical mobility number for suction as a function of d d and kc is determined for the ranges of the parameters 0 001 d d 1 and 1 kc 50 the case of steady current is included as a reference case the effect of waves superimposed on current the effect of a multilaye

a comparison between excess barium and barite as indicators of carbon export 1 since dymond et al 1992 proposed the paleoproductivity algorithm based on bio ba which relies on a strong correlation between ba and organic carbon fluxes in sediment traps this proxy has been applied in many paleoproductivity studies barite the main carrier of particulate barium in the water column and the phase associated with carbon export has also been suggested as a reliable paleoproductivity proxy in some locations we demonstrate that baexcess total barium minus the fraction associated with terrigenous material frequently overestimates babarite barium associated with the mineral barite most likely due to the inclusion of barium from phases other than barite and terrigenous silicates e g carbonate organic matter opal fe mn oxides and hydroxides a comparison between overlying oceanic carbon export and carbon export derived from baexcess shows that the dymond et al 1992 algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14 c and chlorophyll a measurements of primary production this relationship varies by ocean basin but with the application of the appropriate f ratio to 14 c and chlorophyll a primary production estimates the plot of babarite accumulation and carbon export for the equatorial pacific atlantic and southern ocean converges to a global relationship that can be used to reconstruct paleo carbon export index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 4825 oceanography biological and chemical geochemistry keywords paleoproductivity barite export production excess barium marine sediments citation eagle m a paytan k r arrigo g van dijken and r w murray a comparison between excess barium and barite as indicators of carbon export paleoceanography 18 1 1021 doi 10 1029 2002pa000793 2003

laboratory observations of flow and sediment transport induced by plunging regular waves 1 two parallel experiments involving the evolution and runup induced by plunging regular waves near the shoreline of a sloping bed are considered 1 a rigid bed experiment allowing direct hot film measurements of bed shear stresses and 2 a sediment bed experiment allowing for the measurement of pore water pressures as well as observation of sediment suspension and bed morphological changes both experiments utilize the same initial bed profile and wave forcing the experiments show that the mean bed shear stresses experienced onshore of incipient breaking are amplified by nearly a factor of 2 relative to prebreaking conditions whereas their corresponding turbulent fluctuations are amplified even more strongly by a factor of 5 6 the plunging processes lead to a series of vortices whose formation may be explained as the result of shear layer instability measurements show that these vortices can significantly enhance peaks in the offshore directed bed shear stresses moreover near bed pore pressure measurements indicate that these vortices cause large upward directed pressure gradients which in turn produce a corresponding series of suspended sediment plumes shoreward of the initial breaking event these findings are related to the induced morphological changes over both short and long time scales the present results are also compared and contrasted with previous experiments utilizing a similar methodology but involving plunging solitary waves

oblique wave attack on rubble mound breakwaters abstract stability formulae for armour layers of rubble mound breakwaters are usually being applied assuming perpendicular wave attack often the effects of oblique waves are neglected this is however a conservative assumption since the stability of armour slopes generally increases for oblique waves new wave basin tests have been performed to assess the effects of oblique waves on the stability of rock slopes and the stability of cube armoured rubble mound breakwaters the physical model tests were focussed on wave directions between perpendicular 0 and parallel 90 the test programme included tests with long crested waves and tests with short crested waves the results show that for rock slopes the influence of oblique waves is larger for long crested waves based on the test results a design guideline is provided to account for effects of oblique waves on the stability of rock slopes armour layers with a double layer of cubes and armour layers with a single layer of cubes

suction removal of sediment from between armor blocks this paper presents the results of an experimental investigation on suction removal of sediment from between armor blocks stones placed on a loose bed the process of suction has been investigated it was found that the vortices that form in the holes between the armor blocks are key to the process the sediment swept into these vortices is entrained into the main body of the flow by these same vortices the suction removal of sediment from between the armor blocks the critical condition for the onset of suction was determined it was found that the onset of suction is governed by two parameters 1 the shields parameter based on the sediment size and 2 the ratio of sediment size to stone size d d the variation of the critical shields parameter for suction as a function of d d was determined for a broad range of the parameter d d namely 0 001 d d 1 the timescale of the suction process and the downward displacement of stones the general lowering of the armor layer have also been investigated

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

organic geochemistry of impactites from the haughton impact structure devon island nunavut canada organic matter in impactites from the 24 km wide and 39 ma old haughton impact structure canadian high arctic is a mixture of fossil and modern biological components the fossil component represents a conventional oil that was generated from lower palaeozoic marine source material before impact and permeates bedrock dolomites biomarker maturity parameters record the thermal effect of the mid tertiary impact maturity influenced sterane rearranged hopanoid and triaromatic steroid ratios all increase towards the centre of the impact structure where thermal alteration was greatest the heating was probably dominated by an impact related hydrothermal system as such systems last long enough for kinetically based thermal alteration to occur kinetically related biomarker data suggest that the hydrothermal heating lasted for c 5000 years biomarkers are also preserved in dolomite clasts within impact melt breccia and indicate strong thermal alteration modern biological contamination of the rocks is responsible for the superposition of two geochemical signatures which could be cyanobacteria non marine algae or higher plant matter onto the fossil component but they can be recognized and distinguished the data show that the impact structure system holds a record of both the pre impact organic signature and the thermal signature of the impact and thereby indicates that organic geochemistry is a valuable tool in documenting the response of rocks to impacts

origin of an unusual heavy oil from the baiyinchagan depression erlian basin northern china abstract a detailed organic geochemical analysis of six oil samples from the baiyinchagan depression in the erlian basin northern china was carried out in order to evaluate their origin the oils are reservoired at a very shallow depth 223 560 m subsurface and their chemical and physical properties vary greatly ranging from normal to extremely heavy oil the preservation of non biodegraded oil in such a shallow reservoir is possibly related with palaeo pasteurization of the reservoir before uplift maturity difference is not the primary control on the chemical and physical properties of the oils and there is considerable geochemical evidence to suggest the additional influence of in reservoir post accumulation processes such as biodegradation water washing and possibly evaporation whereas some oils appear to be less affected others are moderately biodegraded up to level 4 on the peters and moldowan 1993 scale with sterane distributions largely unaffected and 25 norhopanes undetected contrary to classical biodegradation the unusual heavy oil shows little evidence of biodegradation from aliphatic components water washing is suggested to be the primary process leading to its formation since the severe alteration of soluble aromatic hydrocarbons is observed in addition since the oils have been uplifted significantly after accumulation evaporation and or leakage to modify oil compositions cannot be ruled out

effect of water washing on crude oil compositions crude oils from venezuela oklahoma and new mexico were water washed in the laboratory at temperatures from room temperature to 80 c and with water salinities from 0 to 300 000 mg l in experiments lasting from 7 to 338 hours the effects of water washing were determined by gas chromatographic and gas chromatography mass spectrometric analysis of the residual oil these experiments show that water washing is particularly effective for the c15 fraction and hydrocarbons are removed in the sequence aromatics then n alkanes then naphthenes in the c15 fraction no loss of pristane phytane steranes or terpanes occurs but some aromatics and sulfur compounds especially dibenzothiophene are depleted although water washing reduces api gravity water washing is unlikely to produce tar layers the effects of water washing were simulated with a numerical model based on the equation of diffusion predicted oil water ratios were in good agreement with the experimental values for the light ends and the model suggests that water washing is very fast in the subsurface comparison of oils that appeared to have been water washed in nature with the equivalent unwashed oils showed the expected compositional trends water washing is probably the dominant process affecting crude oil composition in the subsurface when water flows past oils under conditions where bacterial degradation is precluded by temperature 80 c or by lack of dissolved oxygen and the temperatures are too low for thermal cracking

evaluation of the rhenium osmium geochronometer in the phosphoria petroleum system bighorn basin of wyoming and montana usa rhenium osmium re os geochronometry is applied to crude oils derived from the permian phosphoria formation of the bighorn basin in wyoming and montana to determine whether the radiogenic age reflects the timing of petroleum generation timing of migration age of the source rock or the timing of thermochemical sulfate reduction tsr the oils selected for this study are interpreted to be derived from the meade peak phosphatic shale and retort phosphatic shale members of the phosphoria formation based on oil oil and oil source rock correlations utilizing bulk properties elemental composition 13c and 34s values and biomarker distributions the 34s values of the oils range from 6 2 to 5 7 with oils heavier than 2 interpreted to be indicative of tsr the re and os isotope data of the phosphoria oils plot in two general trends 1 the main trend n 15 oils yielding a triassic age 239 43 ma with an initial 187os 188os value of 0 85 0 42 and a mean square weighted deviation mswd of 1596 and 2 the torchlight trend n 4 oils yielding a miocene age 9 24 0 39 ma with an initial 187os 188os value of 1 88 0 01 and a mswd of 0 05 the scatter high mswd in the main trend regression is due in part to tsr in reservoirs along the eastern margin of the basin excluding oils that have experienced tsr the regression is significantly improved yielding an age of 211 21 ma with a mswd of 148 this revised age is consistent with some studies that have proposed late triassic as the beginning of phosphoria oil generation and migration and does not seem to reflect the source rock age permian or the timing of re migration late cretaceous to eocene associated with the laramide orogeny the low precision of the revised regression 21 ma is not unexpected for this oil family given the long duration of generation from a large geographic area of mature phosphoria source rock and the possible range in the initial 187os 188os values of the meade peak and retort source units effects of re migration may have contributed to the scatter but thermal cracking and biodegradation likely have had minimal or no effect on the main trend regression the four phosphoria sourced oils from torchlight and lamb fields yield a precise miocene age re os isochron that may reflect the end of tsr in the reservoir due to cooling below a threshold temperature in the last 10 m y from uplift and erosion of overlying rocks the mechanism for the formation of a re os isotopic relationship in a family of crude oils may involve multiple steps in the petroleum generation process bitumen generation from the source rock kerogen may provide a reset of the isotopic chronometer and incremental expulsion of oil over the duration of the oil window may provide some of the variation seen in 187re 188os values from an oil family

controls of oil family distribution and composition in nonmarine petroleum systems a case study from inner mongolia erlian basin northern china abstract the erlian basin is a continental rift basin located in inner mongolia northern china it is a typical representative of cretaceous northeast asian rift system which includes many small petroliferous basins in mongolia republic and northern china although lower cretaceous source rocks are understood to be most important in the erlian petroleum systems the precise identification of these source rock intervals and their determination on oil families distribution and composition are poorly understood in this tectonically complicated nonmarine basin new bulk data have been gathered from source rock intervals oil sands and crude oil samples in eight main oil producing subbasins geochemical analyses indicate that lower cretaceous aershan formation k1ba and tengger 1 formation k1bt1 are two main source intervals in the erlian basin and their source rock facies vary from profundal lacustrine to marginal lacustrine according to biomarker and trace elements calibration the profundal lacustrine facies is characterised by brackish water and anoxic environment which is similar to their correlative oils family 1 oils the marginal lacustrine facies is characterised by freshwater and suboxic environment which sourced the most common family 2 oils meanwhile different maturation processes exercise the second control on oil groups and their compositions the profundal lacustrine source rocks characterised by their sulphur rich kerogens lead to two oil groups group 1 and group 2 oils whose maturity range from low to normal while the marginal lacustrine source rock only lead to normal maturity oils at last biodegradation affected the composition of a certain oils and formed group 4 heavy oils in addition short migration distance in small subbasins made the contamination or fractionation less notable in the erlian basin

origin and mechanism of the formation of the low oil saturation moxizhuang field junggar basin china implication for petroleum exploration in basins having complex histories the moxizhuang field is a small oil field in the central junggar basin containing several low saturation low resistivity oil reservoirs which display a complex correlation between oil saturation and porosity and permeability that is atypical of both the filled and drained reservoirs biomarker associations of crude oil and grains containing oil inclusions gois of both the present day water bearing zones water zones and the oil and water bearing zones low oil saturation pay zones were analyzed to investigate the mechanisms for the formation of the low saturation low resistivity oil accumulations the biomarker assemblage and hierarchical cluster analysis indicate that oil in the moxizhuang field was mostly generated from permian source rock deposited in brackish to hypersaline anoxic environments the pay zones and several water zones display goi values as much as 38 greater than the generally accepted threshold goi value for an oil column 5 these goi values are similar to those for high saturation oil reservoirs in the bohai bay basin and oil zone samples from australian basins suggesting that both pay zones and water zones were high saturation oil reservoirs in the geologic past geologic history analysis shows that the moxizhuang field was located on the north wing of a paleoanticline during oil charge in the late cretaceous to paleogene this anticline has gradually evolved into a south dipping monocline since the neogene causing northward remigration of accumulated oil differential lateral leakage of accumulated oil in different sandstone layers during the remigration phase led to the formation of the water zones with high goi values completely drained reservoirs and the low saturation low resistivity pay zones partially preserved reservoirs and caused the complex correlation between oil saturation and porosity and permeability compared with other postaccumulation physicochemical alteration processes lateral leakage has rarely been recognized recognizing differential lateral leakage of accumulated petroleum with the existence of high quality unfaulted cap rocks has important implication for petroleum exploration in sedimentary basins having complex evolution histories

influence of oblique wave attack on wave overtopping and forces on rubble mound breakwater crest walls abstract at the crest of rubble mound structures a crest wall is often present to reduce the consumption of material compared to breakwaters without a crest wall to design the crest wall several methods based on estimates of the hydraulic wave loads are available these methods are focussed on waves that approach breakwaters perpendicular in practice the dominant wave conditions are often not perpendicular but approach the breakwater under an angle oblique waves can significantly reduce the amount of wave overtopping and reduce the wave loads on coastal structures compared to perpendicular waves therefore physical model tests have been performed in a wave basin where the wave loads on crest walls and the wave overtopping discharges have been measured under oblique wave attack design guidelines have been developed to take the reduction due to oblique waves into account together with available methods to predict the wave forces and wave overtopping for perpendicular wave attack the obtained results enable a more advanced design of crest walls

asphalt in iron age excavations from the philistine tel miqne ekron city israel origin and trade routes asphalts found as pure lumps or coatings on potsherds were excavated at the philistine site of tel miqne ekron 12th to 7th century bc in the southern inner coastal plain of israel they were studied using the techniques of petroleum geochemistry and were compared to some natural asphalts from the area dead sea floating blocks israel wadi weida a asphalt jordan and hasbeya lebanon tel miqne ekron bitumens show evidence of weathering indicating biodegradation and oxidation they contain less aromatics and more asphaltenes than dead sea asphalt evaporation and biodegradation are recorded at a molecular level especially via the phenanthrenes and dibenzothiophenes however several isotopic and molecular parameters allowed us to correlate the tel miqne ekron asphalt with the dead sea asphalt from the floating blocks the asphalts of hasbeya and wadi weida a do not match the tel miqne ekron asphalt the latter in particular is much more biodegraded based on its steranes the study shows that the dead sea asphalt was imported to tel miqne ekron over a 500 year period this trade posed no problem in the 7th century bc when philistia israel and judah were at peace as part of the pax assyriaca of the assyrian empire however trade during the 12th century bc is puzzling since the asphalt had to be transported across israelite territory that was hostile to the philistines as indicated in the bible e g samson and delilah david and goliath consequently it seems that profitable commerce surpassed ethnic religious and political conflict as can also be observed in the contemporary world

assessing the syngeneity and indigeneity of hydrocarbons in the 1 4 ga velkerri formation mcarthur basin using slice experiments abstract many applications involving analysis of the hydrocarbons in petroleum systems rely upon the assumption that there has been no contamination of the sample precambrian basins are particularly susceptible to hydrocarbon overprinting from contamination due to both age and commonly a low total organic carbon toc content in this study three cores mcmanus 1 walton 2 and shea 1 from the deep marine 1 46 ga old velkerri formation mcarthur basin were subjected to slice experiments and analysis using gas chromatography mass spectrometry gc ms internal slices had consistent hydrocarbon signals providing strong evidence that the organic matter om in the inner slices was indigenous in all three cores both the aliphatic and aromatic hydrocarbon signatures indicated that the exterior of the core was exposed to contamination from both the drilling and sawing processes this contamination overprinted and had the potential to completely obscure the indigenous hydrocarbon signal highlighting the importance of the removal of the exterior portion of the core prior to analysis even for organic rich rocks aromatic ratios indicated all cores were within the oil window and that mcmanus 1 had the highest maturity and walton 2 the lowest walton 2 was the only core to contain biomarkers above the limit of detection lod evidence of high bacterial input to the om included the presence of hopanes bicyclic sesquiterpanes and monomethyl alkanes steranes were absent or below the lod in all cores suggesting a very low or zero contribution from eukaryotes to this deep water low o 2 depositional environment

is pore water oxygen content decoupled from productivity on the california margin trace element results from ocean drilling program hole 1017e san lucia slope california 1 trace element evidence from the california margin ocean drilling program hole 1017e shows significant changes in sediment redox chemistry at intermediate water depths over the last 60 kyr the influence of export production on intermediate water oxygen content can be distinguished from lateral ventilation through comparisons among proxies representing export production flux percent corg and sediment surface i br and pore water mo ag cd re and u oxygenation proxies sulfate reduction within the uppermost sediment column occurred during late quaternary interstadials and the holocene indicating reduced intermediate water ventilation however sulfate reduction was most intense during major interstadials when productivity was enhanced decoupling between export production and pore water oxygen content is demonstrated during deglaciation when the sediment pore water oxygen content increases without a corresponding reduction in export productivity thus both export production and intermediate water ventilation play a role in oxygen minimum zone processes on the california margin

effect of water washing on c15 hydrocarbon fraction of crude oils from northwest palawan philippines recognition and subsequent correlation of biodegraded and or water washed oils with their unaltered counterparts has been a long recognized problem in petroleum geochemistry because water washing and biodegradation can occur concurrently it is difficult to delineate the individual effects of these two oil altering processes especially on the c15 hydrocarbon fraction both processes can cause an oil to become enriched in sulfur and to have a lower api gravity owing to loss of the more volatile components thus the altered oil may appear to be a high sulfur crude of low maturity altered and unaltered oil fractions extracted from cores of a water washed carbonate reservoir offshore northwest palawan were studied to observe the effect of alteration on correla ion parameters water washing resulted in the following changes 1 depletion of 13c in the c15 branched cyclic alkane fraction whereas virtually no change occurred in isotope composition of the aromatic fraction 2 selective loss of dibenzothiophenes followed by loss of aromatic hydrocarbons and 3 virtually no change in steranes or tricyclic and pentacyclic terpanes with the exception of enhancement of 17 agr h norhopane and decrease of 18 agr h trisnorhopane in situations of severe water washing mild biodegradation also occurred as indicated by the loss of n alkanes and possible selective loss of n alkanes having less than 25 carbon atoms relative to branched alkanes cycloalkanes and aromatic components because cycloalkanes and aromatic hydrocarbons are not generally preferentially utilized by bacteria as long as n alkanes are present the changes observed in these two fractions most likely result from water washing because of the potential for extreme compositional changes in the n alkane and aromatic fractions the most useful correlation parameters between the altered and unaltered oils are sterane and terpane distributions stable carbon isotope ratios are also useful however more studies of oils in which water washing is known to have occurred need to be made to explain the general response or various responses of the isotopic composition of oils to water washing

quantitatively predicting the thermal maturity of oil trapped in fluid inclusions based on fluorescence and molecular geochemical data of oil inclusions in the dongying depression bohai bay basin china the fluorescence characteristics of individual oil inclusions and molecular composition analysis of oil inclusions in 20 eocene sandstone samples from the dongying depression were used to assess the relationship between the fluorescence colors of the oil inclusions and their thermal maturity the oil inclusions from the shahejie formation member iii middle submember member iii lower submember and member iv upper submember samples primarily have yellow fluorescence colors 500 nm wavelength of the maximum intensity max 590 nm whereas the oil inclusions in the shahejie formation member iv lower submember reservoir sample only have blue fluorescence 440 nm max 500 nm the molecular maturity parameters from steranes hopanes and aromatic hydrocarbons showed that the oil inclusions with yellow fluorescence colors have relatively low thermal maturities within a narrow range 0 75 0 82 vitrinite reflectance equivalent requ which is significantly lower than that of the sample containing oil inclusions with blue fluorescence colors 1 26 requ the yellow fluorescent oil was interpreted to be related to the main oil generation and expulsion process whereas the blue fluorescent oil was mainly controlled by the thermal cracking process of c14 aromatic hydrocarbons in source rocks reservoirs and oil inclusions this study demonstrates that the fluorescence colors of oil inclusions may be good indicators of thermal maturity in oil systems charged from oil prone source rocks and for the first time makes it possible to quantitatively predict the thermal maturity of oil inclusions based on their fluorescence characteristics however biodegradation water washing phase separation and trapping fractionation should be considered before using this correlation because these processes can also influence fluorescence colors

the organic geochemistry of oil seeps from the sierra de perija eastern foothills lake maracaibo basin venezuela the organic geochemistry of samples from 11 oil seeps was studied the samples were collected from the cachiri area carboniferous region of tule lake maracaibo basin venezuela associated with the tigre fault biomarkers hopanes steranes n alkanes acyclic isoprenoids and aromatic steroids were analyzed using gas chromatography mass spectrometry gc ms these hydrocarbon rich fluids have undergone biodegradation 2 6 on the peters and moldowan scale showing both the partial loss of n alkanes and the microbial degradation of isoprenoids and steranes these oil seeps were generated from a mature calcareous source rock that was deposited in a marine paleoenvironment under reducing conditions moreover these seeps are likely derived from the cretaceous la luna formation that reached a level of maturity near the peak of oil generation in the study area the nature of the studied oil seeps together with the oil generation models reported for this rock unit in the study area suggests that these oils are a mixture of an initially heavy altered oil and a second migrated light crude oil resulting from two generation pulses from the la luna formation evidence for the presence of light oil trapped in the study area should prompt re exploration in the northwestern coast of lake maracaibo in shallow reservoirs previously discarded because they usually demonstrated a lack of light oils