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1.
乌兰花凹陷是二连盆地南部新发现的富油凹陷,对乌兰花凹陷原油物理性质和地球化学性质进行了系统的分析以揭示其特征及来源。原油物理性质显示,乌兰花凹陷原油比重（API gravity）介于20.2°~40.0°之间,主体为正常原油。原油生物标志化合物参数表明,不同构造带之间原油特征存在差异,可以划分为两类原油。一类以土牧尔构造带原油为主,具有低姥值比（Pr/Ph）和C21/C23三环萜烷,相对较高的伽马蜡烷/C31藿烷和规则甾烷/C30藿烷的特征,原油主要为烃源岩在成熟阶段早期的产物,主要以藻类来源为主。另一类原油包括赛乌苏和红井构造带原油,具有高姥值比（Pr/Ph）和C21/C23三环萜烷,相对较低的伽马蜡烷/C31藿烷和规则甾烷/C30藿烷,主要为陆源有机质和藻类有机质混合来源,原油具有更高的成熟度。原油碳同位素和正构烷烃单体烃碳同位素表明这两类原油应是一套烃源岩在不同成熟阶段的产物,原油主要来源于南洼槽阿尔善组烃源岩。阿尔善组烃源岩的非均质性和成熟度导致了两类原油的差异。   相似文献   

2.
Geochemical characterisation of 18 crude oils from the Potwar Basin (Upper Indus), Pakistan is carried out in this study. Their relative thermal maturities, environment of deposition, source of organic matter (OM) and the extent of biodegradation based on the hydrocarbon (HC) distributions are investigated. A detailed oil-oil correlation of the area is established. Gas chromatography-mass spectrometry (GC-MS) analyses and bulk stable carbon and hydrogen isotopic compositions of saturated and aromatic HC fractions reveals three compositional groups of oils. Most of the oils from the basin are typically generated from shallow marine source rocks. However, group A contains terrigenous OM deposited under highly oxic/fluvio-deltaic conditions reflected by high pristane/phytane (Pr/Ph), C30 diahopane/C29Ts, diahopane/hopane and diasterane/sterane ratios and low dibenzothiophene (DBT)/phenanthrene (P) ratios. The abundance of C19-tricyclic and C24-tetracyclic terpanes are consistent with a predominant terrigenous OM source for group A. Saturated HC biomarker parameters from the rest of the oils show a predominant marine origin, however groups B and C are clearly separated by bulk δ13C and δD and the distributions of the saturated HC fractions supporting variations in source and environment of deposition of their respective source rocks. Moreover, various saturated HC biomarker ratios such as steranes/hopanes, diasteranes/steranes, C23-tricyclic/C30 hopane, C28-tricyclic/C30 hopane, total tricyclic terpanes/hopanes and C31(R + S)/C30 hopane show that two different groups are present. These biomarker ratios show that group B oils are generated from clastic-rich source rocks deposited under more suboxic depositional environments compared to group C oils. Group C oils show a relatively higher input of algal mixed with terrigenous OM, supported by the abundance of extended tricyclic terpanes (up to C41+) and steranes.Biomarker thermal maturity parameters mostly reached to their equilibrium values indicating that the source rocks for Potwar Basin oils must have reached the early to peak oil generation window, while aromatic HC parameters suggest up to late oil window thermal maturity. The extent of biodegradation of the Potwar Basin oils is determined using various saturated HC parameters and variations in bulk properties such as API gravity. Groups A and C oils are not biodegraded and show mature HC profiles, while some of the oils from group B show minor levels of biodegradation consistent with high Pr/n-C17, Ph/n-C18 and low API gravities.  相似文献   

3.
The stable hydrogen isotopic compositions (δD) of selected aliphatic hydrocarbons (n-alkanes and isoprenoids) in eight crude oils of similar source and thermal maturity from the Upper Indus Basin (Pakistan) were measured. The oils are derived from a source rock deposited in a shallow marine environment. The low level of biodegradation under natural reservoir conditions was established on the basis of biomarker and aromatic hydrocarbon distributions. A plot of pristane/n-C17 alkane (Pr/n-C17) and/or phytane/n-C18 alkane (Ph/n-C18) ratios against American Petroleum Institute (API) gravity shows an inverse correlation. High Pr/n-C17 and Ph/n-C18 values and low API gravity values in some of the oils are consistent with relatively low levels of biodegradation. For the same oils, δD values for the n-alkanes relative to the isoprenoids are enriched in deuterium (D). The data are consistent with the removal of D-depleted low molecular weight (LMW) n-alkanes (C14–C22) from the oils. The δD values of isoprenoids do not change with progressive biodegradation and are similar for all the samples. The average D enrichment for n-alkanes with respect to the isoprenoids is found to be as much as 35‰ for the most biodegraded sample. For example, the moderately biodegraded oils show an unresolved complex mixture (UCM), loss of LMW n-alkanes (<C15) and moderate changes in the alkyl naphthalene distributions. The relative susceptibility of alkyl naphthalenes at low levels of biodegradation is discussed. The alkyl naphthalene biodegradation ratios were determined to assess the effect of biodegradation. The dimethyl, trimethyl and tetramethyl naphthalene biodegradation ratios show significant differences with increasing extent of biodegradation.  相似文献   

4.
Variations in the carbon isotopic composition (δ13C) of pristane, phytane, n-heptadecane (n-C17), C29 ααα 20R sterane, and aryl isoprenoids provide evidence for a diverse community of algal and bacterial organisms in organic matter of the Upper Ordovician Maquoketa Group of the Illinois Basin. Carbon isotopic compositions of pristane and phytane from the Maquoketa are positively covariant (r = 0.964), suggesting that these compounds were derived from a common source inferred to be primary producers (algae) from the oxygenated photic zone. A variation of 3‰ in δ13C values (−31 to −34‰) for pristane and phytane indicates that primary producers utilized variable sources of inorganic carbon. Average isotopic compositions of n-C17 (−32‰) and C29 ααα 20R sterane (−31‰) are enriched in 13C relative to pristane and phytane (−33‰) suggesting that these compounds were derived from a subordinate group of primary producers, most likely eukaryotic algae. In addition, a substantial enrichment of 13C in aryl isoprenoids (−14 to −18‰) and the identification of tetramethylbenzene in pyrolytic products of Maquoketa kerogen indicate a contribution from photosynthetic green sulfur bacteria to the organic matter. The presence of anaerobic, photosynthetic green sulfur bacteria in organic matter of the Maquoketa indicates that anoxic conditions extended into the photic zone.The δ13C of n-alkanes and the identification of an unusual suite of straight-chain n-alkylarenes in the m/z 133 fragmentograms of Ordovician rocks rich in Gloeocapsomorpha prisca (G. prisca) indicate that G. prisca did not contribute to the organic matter of the Maquoketa Group.  相似文献   

5.
Carbon isotopic compositions were determined by GC–IRMS for individual n-alkanes in crude oils and the free, adsorbed and inclusion oils recovered by sequential extraction from reservoir rocks in the Tazhong Uplift and Tahe oilfield in the Tabei Uplift of Tarim Basin as well as extracts of the Cambrian–Ordovician source rocks in the basin. The variations of the δ13C values of individual n-alkanes among the 15 oils from the Tazhong Uplift and among the 15 oils from the Triassic and Carboniferous sandstone reservoirs and the 21 oils from the Ordovician carbonate reservoirs in the Tahe oilfield demonstrate that these marine oils are derived from two end member source rocks. The major proportion of these marine oils is derived from the type A source rocks with low δ13C values while a minor proportion is derived from the type B source rocks with high δ13C values. Type A source rocks are within either the Cambrian–Lower Ordovician or the Middle–Upper Ordovician strata (not drilled so far) while type B source rocks are within the Cambrian–Lower Ordovician strata, as found in boreholes TD2 and Fang 1. In addition, the three oils from the Cretaceous sandstone reservoirs in the Tahe oilfield with exceptionally high Pr/Ph ratio and δ13C values of individual n-alkanes are derived, or mainly derived, from the Triassic–Jurassic terrigenous source rocks located in Quka Depression.The difference of the δ13C values of individual n-alkanes among the free, adsorbed and inclusion oils in the reservoir rocks and corresponding crude oils reflects source variation during the reservoir filling process. In general, the initial oil charge is derived from the type B source rocks with high δ13C values while the later oil charge is derived from the type A source rocks with low δ13C values.The δ13C values of individual n-alkanes do not simply correlate with the biomarker parameters for the marine oils in the Tazhong Uplift and Tahe oilfield, suggesting that molecular parameters alone are not adequate for reliable oil-source correlation for high maturity oils with complex mixing.  相似文献   

6.
Abundant tricyclic diterpanes (i.e., pimarane, dehydroabietane and simonellite) and tetracyclic diterpanes (e.g., phyllocladane) were detected in coal samples from the third member of the Shahejie Formation, Lower-Eogene, Liaohe Basin, China. Gas chromatography–isotope ratio mass spectrometry (GC–IRMS) analyses show that the carbon isotopic composition of terrigenous tricyclic and tetracyclic diterpenoid hydrocarbons are about 4–6‰ enriched in 13C compared to n-alkanes in the same samples. In addition, the pimaranes and phyllocladane have comparatively narrow stable carbon isotopic compositions among the different samples, with a slightly wider range in δ13C compositions for the abietanes (i.e., abietane, dehydroabietane and simonellite). The n-alkanes and triterpenoids reflect the δ13C compositions of higher plant wax.  相似文献   

7.
Isotopic compositions of carbon-bound hydrogen in individual n-alkanes and acyclic isoprenoid alkanes, from a number of crude oil samples, were measured using gas chromatography-thermal conversion-isotope ratio mass spectrometry. The precision of this technique is better than 3‰ for most alkanes, compared to the large range of δD variation among the samples (up to 160‰). The oils were selected from major genetic oil families in the Western Canada Sedimentary Basin, with source rocks ranging in age from Ordovician (and possibly Cambrian) to Cretaceous. The hydrogen isotopic composition of alkanes in crude oils is controlled by three factors: isotopic compositions of biosynthetic precursors, source water δD values, and postdepositional processes. The inherited difference in the lipid's biosynthetic origins and/or pathways is reflected by a small hydrogen isotopic variability within n-alkanes, but much larger differences in the δD values between n-alkanes and pristane/phytane. The shift toward lighter hydrogen isotopic compositions from Paleozoic to Upper Cretaceous oils in the WCSB reflects a special depositional setting and/or a minor contribution of terrestrial organic matter. The strong influence of source water δD values is demonstrated by the distinctively lower δD values of lacustrine oils than marine oils, and also by the high values for oils with source rocks deposited in evaporative environments. Thermal maturation may alter the δD values of the alkanes in the oil to some extent, but secondary oil migration does not appear to have had any significant impact. The fact that oils derived from source rocks that could be of Cambrian age still retain a strong signature of the hydrogen isotopic compositions of source organic matter, and source water, indicates that δD values are very useful for oil-source correlation and for paleoenvironmental reconstructions.  相似文献   

8.
Biodegraded oils are widely distributed in the Liaohe basin, China. In order to develop effective oil-source correlation tools specifically for the biodegraded oils, carbon isotopic compositions of individual n-alkanes from crude oils and their asphaltene pyrolysates have been determined using the gas chromatography–isotope ratio mass spectrometry technique. No significant fractionation in the stable carbon isotopic ratios of n-alkanes in the pyrolysates of oil asphaltenes was found for anhydrous pyrolysis carried out at temperatures below 340°C. This suggests that the stable carbon isotopic distribution of n-alkanes (particularly in the C16–C29 range) in the asphaltene pyrolysates can be used as a correlation tool for severely biodegraded oils from the Liaohe Basin. Comparison of the n-alkane isotopic compositions of the oils with those of asphaltene pyrolysates shows that this is a viable method for the differentiation of organic facies variation and post-generation alterations.  相似文献   

9.
《Applied Geochemistry》2005,20(10):1875-1889
Based on the systematic analyses of light hydrocarbon, saturate, aromatic fractions and C isotopes of over 40 oil samples along with related Tertiary source rocks collected from the western Qaidam basin, the geochemical characteristics of the Tertiary saline lacustrine oils in this region was investigated. The oils are characterized by bimodal n-alkane distributions with odd-to-even (C11–C17) and even-to-odd (C18–C28) predominance, low Pr/Ph (mostly lower than 0.6), high concentration of gammacerane, C35 hopane and methylated MTTCs, reflecting the high salinity and anoxic setting typical of a saline lacustrine depositional environment. Mango’s K1 values in the saline oils are highly variable (0.99–1.63), and could be associated with the facies-dependent parameters such as Pr/Ph and gammacerane indexes. Compared with other Tertiary oils, the studied Tertiary saline oils are marked by enhanced C28 sterane abundance (30% or more of C27–C29 homologues), possibly derived from halophilic algae. It is noted that the geochemical parameters of the oils in various oilfields exhibit regular spatial changes, which are consistent with the depositional phase variations of the source rocks. The oils have uncommon heavy C isotopic ratios (−24‰ to −26‰) and a flat shape of the individual n-alkane isotope profile, and show isotopic characteristics similar to marine organic matter. The appearance of oleanane and high 24/(24 + 27)-norcholestane ratios (0.57–0.87) in the saline oils and source rocks confirm a Tertiary organic source.  相似文献   

10.
Siliceous sourced Tertiary oils from the Circum-Pacific area of Japan, Russia and the U.S.A. have a heavy carbon isotope composition, monomodal n-alkane distributions, and nearly identical regular sterane compositions with a predominance of C27 homologues. These are consistent with open marine depositional environments dominated by diatomaceous organic matter. However, a number of alkane and biomarker parameters such as Pr/Ph, CPI, relative concentration of 28,30-bisnorhopane, and the C35/C34 homohopane ratio indicate more oxic depositional environments for the source rocks of Japan and Russia. In contrast to the California Monterey Formation sourced oils, petroleums with low maturity levels from the North Sakhalin basin, Russia and the Akita basin, Japan have lower concentrations of asphaltenes and sulphur and are characterized by higher API gravities. A correlation of extractable organic matter from source rocks vs the least matured petroleums demonstrates that oil expulsion in siliceous shales of the Akita basin occurs at a maturity level corresponding to Ro≥0.65%, which is in the range of the conventional oil window (Ro = 0.6−1.1%).  相似文献   

11.
The extent of sterane isomerisation reactions and the moretane/hopane ratios of 234 crude oils, taken world wide, from a wide variety of source rocks of differing geological ages, have been measured.This data indicates that in 78 crude oils derived from Tertiary source rocks, sterane isomerisation reactions as determined by the 20S/(20S + 20R) ration of the C29 5α(H), 14α(H), 17α(H) normal-steranes and the C29 iso/(iso + normal) ratio [iso = 5α (H), 14β(H), 17β(H)] are mainly incomplete and sometimes considerably so. In addition, the same crude oils have 17β(H), 21α(H)-moretane/17α(H), 21β(H)-hopane ratios which are significantly greater (predominantly in the range 0.10–0.30) than those of crude oils derived from older, mature source rocks (mainly less than 0.1).This data, for crude oils, lends support to the hypothesis, proposed by Mackenzie and McKenzie (1983) for source rock extracts, that the time/temperature constraints of sterane isomerisation reactions are such that the time available for isomerisation in Tertiary sediments is generally insufficient, despite generation of crude oil at relatively high temperatures.An alternative hypothesis is that the incomplete sterane isomerisation of Tertiary crude oils may be due to generation of these crude oils from their deltaic, land plant-containing source rocks under low heating conditions.A third hypothesis proposes that the Tertiary crude oils may have picked up the incompletely isomerised steranes from immature sediments during migration. Although possible in particular instances, such a mechanism does not appear to be generally applicable since, in that case, the phenomenon would then appear to be restricted to the Tertiary.The higher moretane/hopane ratios of the Tertiary crude oils could suggest that constraints, similar to those applying in sterane isomerisation, also operate in the conversion of moretane to 17α(H)-hopane.  相似文献   

12.
Expulsion of petroleum from source rock is a complex part of the entire migration process. There exist fractional effects on chemical compositions in hydrocarbon expulsion. Does the carbon isotopic fractionation occur during expulsion and to what extent? Here the influence of hydrocarbon expulsion on carbon isotopic compositions of individual n-alkanes from pyrolysates of selected terrestrial kerogens from Tuha basin and Fushun, Liaoning Province of China has been experimentally studied. The pyrogeneration-expulsion experiments were carried out under semi-closed system. The carbon isotopic compositions of individual n-alkanes were measured by GC-IRMS. The main conclusions are as follows. First, there is carbon isotopic fractionation associated with hydrocarbon expulsion from Type III kerogens in Tuha Basin. There exist differences of carbon isotopic compositions between the unexpelled n-alkanes and expelled n-alkanes from Tuha desmocollinite and Tuha mudstone. Second, there is almost no carbon isotopic fractionation associated with hydrocarbon expulsion from Type II kerogens in Fushun and Liaohe Basin. Third, carbon isotopic fractionation in hydrocarbon expulsion should be considered in making oil-source correlation of Type III kerogens at least in the Tuha Basin. Further studies need to be carried out to determine whether this is true in other basins. Fourth, oil and source at different maturity levels cannot be correlated directly for Type III kerogens since the carbon isotopic compositions of expelled hydrocarbons at different temperatures are different. The expelled hydrocarbons are usually lighter (depleted in 13C) than the hydrocarbons remaining in the source rock at the same maturity.  相似文献   

13.
Thirty one crude oil samples from Lower Cretaceous reservoirs in southern Iraq were analyzed using bulk property and molecular methods to determine their maturity and biomarker characteristics, as well as to obtain information on their respective source rocks. All the oils are unaltered, non-biodegraded, have high sulfur content and API gravity is in the range for light to heavy oil (19–40° API). They are characterized by low Pr/Ph values, even/odd predominance and front-end biased n-alkane distributions. Based on these parameters the oils were generated and expelled from a marine carbonate source rock bearing Type II-S kerogen. Compositional similarities of hopane and sterane biomarkers with those from potential source rocks allowed identification of the Upper Jurassic–Lower Cretaceous Sulaiy and Yamama carbonate succession as the effective source beds. A similar composition of normal and isoprenoid hydrocarbons among the oils suggests an origin from a common source rock. However, biomarker maturity ratios indicate a wide range of maturity. This appears to result from the type of burial history of the source rock, characterized by a slow passage through the liquid window interval during an extended period of geologic time.  相似文献   

14.
The geochemical characteristics of crude oils from Zao-V oil measures in the Shen-jiapu oilfield are systematically described in terms of the fractional composition of crude oils, GC characteristics of saturated hydrocarbon fraction of crude oils and the characteristics of their bio-markers. The deposifional environment, type and evolution of the biological source are also discussed. All pieces of evidence such as low saturated hydrocarbon fraction, high resin and asphalt, high isoprenoid alkane, weak odd-carbon number predominance ( CPI ranging from 1.23 to 1,29, OEP ranging from 1.14 to 1.16) and low sterane and terpane maturity parameters show these crude oils are immature oils. Low Pr/Ph ratios (0.66 -0.88) and high gammacer-ante/C31 hopane ratios ( 0.59 - 0.86 ) indicate the source rocks were formed in a slightly saline to brackish reducing lake depositional environment. Gas chromatographic characteristics of the saturated hydrocarbon fraction and the predominance of C30 hopane in terpane series and C29 sterane in sterane series indicate the biological source of the crude oils is composed mainly of bacterial and algal organic matter, and some algae are perhaps the main contributor of organic matter to the source rocks.  相似文献   

15.
The lower part of Shayi Member (Es1x Sub-Member) composed mainly of dark mudstones and shales is the dominant source rocks for the Lixian Slope. Based on organic petrology, organic and inorganic geochemistry analyses of several mudstone and shale samples selected from Es1x Sub-Member, this research provides an overview on type, origin and thermal maturity of organic matters, as well as depositional environment of Es1x Sub-Member. Kerogen microscopy observation shows that the macerals are dominated by sapropelinite with a significant mixture of vitrinite and inertinite, indicating that aquatic algal-bacterial organic matter inputs are dominate with a significant contribution of terrigenous organic matter inputs. This statement is supported by n-alkane patterns distribution characteristics, high (n-C21 + n-C22)/(n-C28 + n-C29) values (average = 1.77), the plot of high Ph/n-C18 values (average = 4.15) versus low Pr/n-C17 values (average = 1.13), and high proportion of C27 sterane and C29 sterane (average = 37.7 and 42.0%, respectively). In addition, the rather low Pr/Ph values (average = 0.38), high gammacerane index values (average = 0.30), high V/Ni and V/(V + Ni) values (average = 11.84 and 0.89, respectively), high Sr/Ba and Sr/Cu values (average = 8.54 and 108, respectively), indicative of a saline water condition and a anoxic depositional environment. The low C29 sterane ααα 20S/(20S + 20R), C29 sterane αββ/(αββ + ααα), C31 homohopane 22S/(22S + 22R), C32 homohopane 22S/(22S + 22R), Ts/(Ts + Tm) values and relatively high moretane/hopane values show that the level of thermal maturity of organic matters in Es1x Sub-Member are low.  相似文献   

16.
《Applied Geochemistry》2003,18(3):445-456
Since the Shu103 well was successfully drilled in 1995, the Buried Hill reservoir is receiving a new exploration emphasis in the Liaohe Basin, China. The Buried Hill oils can be divided into 3 main types in the Shuguang-Huangxiling area based on their chemical and isotopic compositions. The first type is collected mostly from the Shuguang area. The similarity to the Es4 oils and the Es4 source rock extracts indicates that they were mainly expelled from the fourth member of the Shahejie formation (Es4) in the Chenjia Sag and/or Panshan Sag, deposited in a stratified paleolake system. The second is charactized by a relative high Pr/Ph ratio, low gammacerane content and depletion of 12C in individual n-alkanes. These characteristics represent a typical origin from dominantly freshwater paralic lacustrine sediments. Various biomarker indices of the other Buried Hill oils fall between the former two types. The authors infer that these oils may be derived from the adjacent Qingshui Sag and/or Panshan Sag, and were likely generated from transitional sedimentary facies between well-circulated freshwater paralic lacustrine and relatively closed saline lacustrine.  相似文献   

17.
Twenty-seven heavy crude oils of diverse origin were geochemically assessed with respect to both bulk and mlecular composition for the purpose of identifying and quanttfying valid biomarker parameters for low maturity oils. The low thermal maturity level of many of these oils is evident from the bulk and alipathic chromatographic data, and oil sourced from both marine and terrigenous organic matter are represented. Selective metastable ion monitoring (SMIM) was employed to measure separately the distribution of C27, C28, and C29 sterane isomers. The useful maturity indicators include the C29 5α(H) 20S/20R ratio, the relative quantity of the biological sterane configuration in each of the total normal C27, C28, and C29 steranes, and the rearranged to normal sterane ratio. In addition, C27 rearranged steran es appear to form at a faster rate than C28 or C29 rearranged steranes. However, the isomerization of the C27 biological component appears to occur at a slower rate than the C29 counterpart suggesting that the former may be used as a maturity parameter at higher levels of thermal maturation. In the triterpane distributions, the C27 trisnorhopane isomers and the moretane to hopane ratios appear to be both source and maturity related and cannot be used as successful maturity parameters in oils unless they share a common source. The C31+ hopane 22S/22R equilibrium ratio appears to increase with increasing molecular weight (C31–C34).  相似文献   

18.
1IntroductionTheOrdosBasinisthesecondlargestoilandgas bearingbasininChina .ItislocatedinthePaleo zoicplatformandbelongstoacratonbasin ,whichisincongruencewiththePaleozoicdepressionattheedgesoftheplatformandtheMesozoic Cenozoicdepressionwithintheplatform .SincethediscoveryofnaturalgasesinWellShancan 1andWellYu 3in 1989,theassessmentandexplorationofOrdovicianweatheringcrustnaturalgasesintheOrdosBasinhaveattractedextensiveatten tion (YangJunjieetal.,1996 ;DaiJinxingetal.,1997) .Thecentral…  相似文献   

19.
The Masila Basin is an important hydrocarbon province in Yemen, but the origin of hydrocarbons and their generation history are not fully understood. In this regard, 10 crude oils from different petroleum reservoir sections in the Masila Basin were characterized by a variety of biomarker and non-biomarker parameters using GC, GC-MS and stable carbon isotope techniques. Oils from the Masila Basin display pristane/phytane (Pr/Ph) ratios ranging from 1.7 to 2.0, low sulfur content, high C35 homohopane index, relatively high C27 sterane concentrations and relatively high tricyclic terpanes suggesting a marine clay source rock that was deposited in mildly anoxic to suboxic conditions with dominantly algal organic matter. C29 20S/(20S + 20R) steranes and ββ/(ββ + αα) sterane ratios indicate that the Masila oils have reached peak oil window maturity. Another related feature of these oils is the absence of 18α (H)-oleanane, which suggests a source age older than Cretaceous. The carbon isotope compositions are similar to those of the potential source rocks, which range from −25.4‰ to −28.3‰, indicating a marine environment. The new data presented in this paper suggest that the Masila oils constitute one oil family and that the oil originated from the Upper Jurassic Madbi source rock in the basin.  相似文献   

20.
An integrated petrological and geochemical analysis of surface and drilled oil sands was conducted to assess the organic matter origin/type, thermal maturity and paleoenvironment. Petrographic analysis of the oil sand used to establish the relationships between porosity and permeability with bulk density, RQI, NPI and FZI. The strong correlation between reservoir quality index (RQI) and permeability (R2 = 0.98) reveal that porosity has a good correlation to RQI. The biomarker signatures of the analyzed oil reveal predominance of subaquatic‐derived source input with mainly land plant materials. This was indicated based on the average concentration of αααC27:C28:C29 sterane 20R of about 38%, 22% and 40% respectively. This interpretation is also supported by high values of tricyclic terpane/αβC30 hopane and regular sterane/αβC30 hopane. An anoxic condition of deposition within a lacustrine paleoenvironment that attributed to the enhancement of the preservation of the organic matters in the area were indicated based on the low Pr/Ph ratios (average 0.74), low values of αβC31‐22R‐hopane/αβC30 hopane ratios and high C26/C25 tricyclic terpane ratios as well as the presence of gammacerane and a low water salinity. Biomarker maturity parameters show that the extracted oil sand has entered the early oil window stage.  相似文献   

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