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1.
Hydrous pyrolysis (HP) experiments were used to investigate the petroleum composition and quality of petroleum generated from a Brazilian lacustrine source rock containing Type I kerogen with increasing thermal maturity. The tested sample was of Aptian age from the Araripe Basin (NE-Brazil). The temperatures (280–360 °C) and times (12–132 h) employed in the experiments simulated petroleum generation and expulsion (i.e., oil window) prior to secondary gas generation from the cracking of oil. Results show that similar to other oil prone source rocks, kerogen initially decomposes in part to a polar rich bitumen, which decomposes in part to hydrocarbon rich oil. These two overall reactions overlap with one another and have been recognized in oil shale retorting and natural petroleum generation. During bitumen decomposition to oil, some of the bitumen is converted to pyrobitumen, which results in an increase in the apparent kerogen (i.e., insoluble carbon) content with increasing maturation.The petroleum composition and its quality (i.e., API gravity, gas/oil ratio, C15+ fractions, alkane distribution, and sulfur content) are affected by thermal maturation within the oil window. API gravity, C15+ fractions and gas/oil ratios generated by HP are similar to those of natural petroleum considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous age. API gravity of the HP expelled oils shows a complex relationship with increasing thermal maturation that is most influenced by the expulsion of asphaltenes. C15+ fractions (i.e., saturates, aromatics, resins and asphaltenes) show that expelled oils and bitumen are compositionally separate organic phases with no overlap in composition. Gas/oil ratios (GOR) initially decrease from 508–131 m3/m3 during bitumen generation and remain essentially constant (81–84 m3/m3) to the end of oil generation. This constancy in GOR is different from the continuous increase through the oil window observed in anhydrous pyrolysis experiments. Alkane distributions of the HP expelled oils are similar to those of natural crude oils considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous age. Isoprenoid and n-alkane ratios (i.e., pristane/n-C17 and phytane/n-C18) decrease with increasing thermal maturity as observed in natural crude oils. Pristane/phytane ratios remain constant with increasing thermal maturity through the oil window, with ratios being slightly higher in the expelled oils relative to those in the bitumen. Generated hydrocarbon gases are similar to natural gases associated with crude oils considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous, with the exception of elevated ethane contents. The general overall agreement in composition of natural and hydrous pyrolysis petroleum of lacustrine source rocks observed in this study supports the utility of HP to better characterize petroleum systems and the effects of maturation and expulsion on petroleum composition and quality.  相似文献   

2.
Relatively little work has been published on the correlation between the light hydrocarbon distributions in reservoir fluids and their proposed source rocks [Philippi, G. T. (1981)]. The aim of our work was to study this relationship in detail for samples from Mid-Norway. The main source rocks offshore Mid-Norway are the marine shales of the Late Jurassic Spekk Formation and the coals and paralic shales of the Early Jurassic Åre Formation. Reliable light hydrocarbon (C4–C13) data for source rock samples were acquired by thermal extraction-GC of the source rocks. Of these, notably the hydrocarbons in the C6–C8 range (routinely measured in test fluids) were used to discriminate between the Spekk and Åre Formation samples. A total of twenty-six samples from the Spekk Formation and twenty-four samples from the Åre Formation at different maturity levels and facies were analyzed. In general, the two source rock types differ in their light hydrocarbon composition by the presence of relatively more aromatics and cyclohexanes in the Åre samples, while the Spekk samples are richer in cyclopentanes and acyclic hydrocarbons. We show that source rock facies is a more important indicator of light hydrocarbon composition than maturity variation. Differences in the chemical composition, which can be used to discriminate between the two source rocks, were supported by differences in the carbon isotope composition of individual components of the same fraction, as determined by GHM-IR-MS analysis of eleven samples. Further, the light hydrocarbon compositions of reservoir fluids (oils and condensates) were compared with those for the source rock(s). Sixty-six gas chromatograms of oils and condensates, representing most of the known petroleum accumulations in Mid-Norway, were collected. Of these, five oil samples were selected for detailed isotopic analysis of individual components (GC-IR-MS). When using a classification scheme based on data from sediment samples, data for the light hydrocarbon fraction of oils and condensates indicate that the Spekk Formation is the dominant source for most of the fields from Mid-Norway, with a significant contribution from the Åre Formation being detected principally in one field. Differences in the chemical composition of the C6–C8 fractions were supported by differences in the carbon isotope composition of individual components, which also discriminate between the oils. Although the classification diagrams used in this study are based on source rock data from Mid-Norway, the method can be applied to other areas, providing that the diagrams are calibrated with source rock data from the area of interest.  相似文献   

3.
《Organic Geochemistry》1999,30(2-3):119-132
High molecular weight (HMW) hydrocarbons (>C40) and asphaltenes are important constituents of petroleum and can cause problems related to crystallization and deposition of paraffin waxes during production and transportation as well as in the formation of tar mats. However, traditional methods to isolate asphaltene fractions, by adding 40 volumes in excess of low boiling point solvents such as pentane, hexane or heptane, can produce asphaltene fractions which are contaminated with a significant amount of microcrystalline waxes (>C40). The presence of these microcrystalline waxes in the asphaltene fractions has the potential to provide misleading and ambiguous results in modeling and treatment programs. The sub-surface phase behaviour of an asphaltene fraction will be quite different from that of a wax-contaminated asphaltene fraction. Similarly accurate modelling of wax drop-out requires information on pure wax fractions and not asphaltene-dominated fractions. Hence the goal of this paper is to describe a novel method for the preparation of wax-free asphaltene fractions. In addition, this method provides a quantitative subdivision of the wax fraction into pentane soluble and insoluble waxes which, when correlated with physical properties of crude oil such as viscosity, pour point, cloud point, etc., may help explain causes of wax deposition during production, transportation and storage of petroleum.  相似文献   

4.
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   

5.
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   

6.
The Athabasca oil sand bitumen, and its major component fractions, have been heated with and without added montmorillonite to simulate natural geological diagenesis. The products of the treatment of the whole bitumen were found to be essentially the sum of the products of the treatment of the component parts. The saturated hydrocarbon fraction underwent little change, with only minor cracking apparent. Some cracking and polymerization of the aromatic hydrocarbon fraction was noted. Geochemical analysis of these products indicated that the simulation had caused a continuation of the normal petroleum maturation sequence towards coke and gas. Treatment of the polar fraction and asphaltenes caused a continuation of the maturation sequence towards a ‘crude oil’, further treatment of which continued towards coke and gas. Geochemical examination of this ‘crude oil’ yielded information on the past history of the bitumen from the time of asphaltene formation. The geochemical evidence indicates that the Athabasca bitumen may have originated in an unusual marine environment, and that the maturation and exodus from its source rock differed from that of conventional crude oils. The overall results indicate that, except for the maturation of the polar and asphaltene fractions, the bio-degradation of a crude oil is not reversible by diagenetic means.  相似文献   

7.
A significant quantity of hydrocarbons (including alkanes) is occluded in the skeleton of the asphaltene molecule. The hydrocarbons are probably remnants of the “original oil” which had been retained within the asphaltene matrix and protected from the secondary alteration processes that occurred subsequently in the oil reservoirs. In this work we report that oxidation of asphaltenes by stirring with 30%H2O2–HAc or NaIO4–NaH2PO4 can release nC7-soluble oxidized products, including the occluded hydrocarbons. Characterization of the nC7-soluble fractions of oxidized products can be applied to highlight some geochemical problems, such as in studies of oil–oil correlation, oil–source correlation and secondary alterations of oil reservoirs. It will be especially useful to recover the original geochemical information of some oil reservoirs heavily degraded by post-depositional processes.  相似文献   

8.
The solubility of a 44° API (0.806 sp. gr.) whole crude oil has been measured in methane with water present at temperatures of 50 to 250°C and pressures of 740 to 14,852 psi, as have the solubilities of two high molecular weight petroleum distillation fractions at temperatures of 50 to 250°C and pressures of 4482 to 25,266 psi. Both increases in pressure and temperature increase the solubility of crude oil and petroleum distillation fractions in methane, the effect of pressure being greater than that of temperature. Unexpectedly high solubility levels (0.5–1.5 grams of oil per liter of methane—at laboratory temperature and pressure) were measured at moderate conditions (50–200°C and 5076–14504 psi). Similar results were found for the petroleum distillation fractions, one of which was the highest molecular weight material of petroleum (material boiling above 266°C at 6 microns pressure). Unexpectedly mild conditions (100°C and 15,200 psi; 200°C and 7513 psi) resulted in cosolubility of crude oil and methane. Under these conditions, samples of the gas-rich phase gave solubility values of 4 to 5 g/l, or greater.Qualitative analyses of the crude-oil solute samples showed that at low pressure and temperature equilibration conditions, the solute condensate would be enriched in C5–C15 range hydrocarbons and in saturated hydrocarbons in the C15+ fraction. With increases in temperature and especially pressure, these tendencies were reversed, and the solute condensate became identical to the starting crude oil.The data of this study, compared to that of previous studies, shows that methane, with water present, has a much greater carrying capacity for crude oil than in dry systems. The presence of water also drastically lowers the temperature and pressure conditions required for cosolubility.The data of this and/or previous studies demonstrate that the addition of carbon dioxide, ethane, propane, or butane to methane also has a strong positive effect on crude oil solubility, as does the presence of fine grained rocks.The n-paraffin distributions (as well as the overall composition) of the solute condensates are controlled by the temperature and pressure of solution and exsolution, as well as by the composition of the original starting material. It appears quite possible that primary migration by gaseous solution could ‘strip’ a source rock of crude-oil like components leaving behind a bitumen totally unlike the migrated crude oil. The data of this study demonstrate previous criticisms of primary petroleum migration by gas solution are invalid; that primary migration by gaseous solution cannot occur because methane cannot dissolve sufficient volumes of crude oil or cannot dissolve the highest molecular weight components of petroleum (tars and asphaltenes).  相似文献   

9.
Biomarker distributions in a suite of asphaltenes and kerogens have been analysed by flash pyrolysis directly coupled to a GCMS system. Attention has been focussed on biomarkers of the sterane and triterpane types. The sample suite under investigation consists of sediments with different kerogen types and some crude oils. Biomarker distributions in the pyrolysates have been compared with the “free” biomarkers in the corresponding saturated hydrocarbon fractions.The analyses show significant differences between the distributions of the free biomarkers and those in the pyrolysates. The latter have lower amounts of steranes while diasteranes are absent or present at low concentrations only. In the triterpane traces a shift of maximum intensity from C30 (free compounds) to C27/C29 is observed. Furthermore, the pyrolysates contain a set of triterpenes (not present among the free compounds), and there is a selective loss of “non-regular” triterpanes that are present in the saturated hydrocarbon fractions. The observed differences between pyrolysates and free hydrocarbons can be explained partly by the processes occurring during pyrolysis such as bond rupture and subsequent stabilisation of primary pyrolysis products. To a certain extent these differences also show that maturation processes occurring in sediments have effects on free biomarker molecules different from those on molecules that are enclosed in a macromolecular matrix (kerogen or asphaltenes).Differences between biomarker distributions of asphaltene and kerogen pyrolysates are relatively small. A comparison with the pyrolysates from extracted whole sediments suggests that these differences are mainly caused by interactions between the organic material and the mineral matrix during pyrolysis.Oil asphaltenes behave differently from sediment asphaltenes as their pyrolysates are more similar to the corresponding saturated hydrocarbon fractions, i.e. the differences described above are observed to a much smaller extent. This different behaviour appears to be the result of coprecipitation of a part of the maltene fraction with the oil asphaltenes.  相似文献   

10.
A new maturity parameter determined on both oil and bitumen samples, the asphaltene Tmax, is proposed and discussed. This parameter could be very useful to address the maturity of the source rock. The asphaltene Tmax is measured by programmed Rock-Eval pyrolysis, using a modified temperature program. Some phases of the experimental procedure, such as the asphaltene preparation and the Rock-Eval measurement substratum choice, are crucial in order to achieve reliable data. Laboratory simulations were carried out in order to assess the possible effects of both primary and secondary migration on asphaltene Tmaxin the expelled oil: the original value of the asphaltene Tmax in the bitumen is not substantially modified and it is very close to that measured on kerogen. Examples of the determination of asphaltene Tmax on many samples, collected from different areas and with different organic matter composition, are given. Results show that Tmax values from oil asphaltenes are reasonable indicators of source rock maturity.  相似文献   

11.
柯坪隆起区是塔里木盆地海相烃源岩露头发育较好的地区之一,但相关的油气研究报道不多。本文详细研究了塔里木盆地柯坪隆起区油苗的有机地球化学特征并进行了相关的成因分析。阿克苏油苗经历了严重的生物降解作用,饱和烃生物标志物所能提供的成因信息十分有限。原油沥青质组分及储层吸附/包裹烃受后生作用影响较小,综合分析油苗沥青质热解产物与吸附/包裹烃的生物标志物及其碳同位素组成可以获得更多有效的成因信息。研究结果表明,阿克苏油苗与其储层吸附/包裹烃具有不同来源。油苗、沥青质以及沥青质热解产物的碳同位素特征与已经报道的多数海相原油及其沥青质较为接近,与典型的寒武系烃源来源的原油差异显著。而储层吸附/包裹烃与已报道的典型寒武系烃源岩来源油的生物标志物及碳同位素特征比较类似,可能形成于较高的热演化阶段。  相似文献   

12.
通过对生排烃模拟实验产物 (残留油和排出油 )中正构烷烃单体碳同位素组成的测定,揭示出生排烃过程中正构烷烃碳同位素组成的变化特征。研究表明,生烃初期,液态正构烷烃主要来自干酪根的初次裂解,它们的碳同位素组成不论是在排出油中还是在残留油中,随温度的变化都不明显,呈现较相似的分布特征;在生烃高峰期,早期形成的沥青质和非烃等组分的二次裂解以及高碳数正构烷烃可能存在的裂解,使得正构烷烃单体碳同位素组成明显富集13 C,尤其在高碳数部分呈现出较大的差异。另外,实验结果显示排烃作用对液态正烷烃单体碳同位素组成的影响不太显著。  相似文献   

13.
Combined with the actual geological settings, tight oil is the oil that occurs in shale or tight reservoirs, which has permeability less than 1 mD and is interbedded with or close to shale, including tight dolomitic oil and shale oil. The Fengcheng area (FA), at the northwest margin of the Junggar Basin, northwest China, has made significant progress in the tight oil exploration of the Fengcheng (P1f) Formation recently, which indicates that the tight oil resources have good exploration prospects. Whereas the lack of recognition of hydrocarbon generation and expulsion characteristics of Permian P1f source rocks results in the misunderstanding of tight oil resource potential. Based on the comprehensive analysis of geological and geochemical characteristics of wells, seismic inversion, sedimentary facies, tectonic burial depth, etc., the characteristics of P1f source rocks were investigated, and the horizontal distributions of the following aspects were predicted: the thickness of source rocks, abundance and type of organic matter. And on this basis, an improved hydrocarbon generation potential methodology together with basin simulation techniques was applied to unravel the petroleum generation and expulsion characteristics of P1f source rocks in FA. Results show that the P1f source rocks distribute widely (up to 2039 km2), are thick (up to 260 m), have high total organic content (TOC, ranging from 0.15 to 4 wt%), are dominated by type II kerogen and have entered into low mature–mature stage. The modeling results indicate that the source rocks reached hydrocarbon generation threshold and hydrocarbon expulsion threshold at 0.5% Ro and 0.85% Ro and the comprehensive hydrocarbon expulsion efficiency was about 46%. The amount of generation and expulsion from the P1f source rocks was 31.85 × 108 and 15.31 × 108 t, respectively, with a residual amount of 16.54 × 108 t within the source rocks. Volumetrically, the geological resource of shale oil is up to 15.65 × 108 t. Small differences between the amounts calculated by the volumetric method compared with that by hydrocarbon generation potential methodology may be due to other oil accumulations present within interbedded sands associated with the oil shales. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

14.
A detailed organic geochemical study; utilising petrography, biomarker hydrocarbon analysis and high temperature GC analysis of extractable wax hydrocarbon constituents was performed on four marginally oil window-mature source rocks from the Shahejie Formation (Eocene), Damintun depression in eastern China. The main maceral components in the source rocks were vitrinite, liptinite and exinite, with vitrinite being more abundant (>50 vol.%) in organic-lean samples whose TOC contents were between 1 and 2 wt.%. Large differences in pristane/phytane ratios suggested that the organic-rich samples were deposited in a less oxic depositional environment than that for the organic-lean rocks. The distribution of extractable wax hydrocarbons, determined by high temperature GC, showed a marked difference between these two sample types. The organic-rich samples contained high molecular weight hydrocarbons (HMWHCs) dominated by macrocrystalline n-alkanes (n-C23–n-C37, typically maximising at n-C29), while the organic-lean samples contained lower amounts of extractable wax hydrocarbons but were relatively rich in microcrystalline components (> n-C35). In all source rocks (Es3 and Es4), a noticeable odd-over-even predominance (OEP) of n-alkane chain lengths (up to n-C65) was evident, consistent with a direct biological origin for the long n-alkyl chains. They were most probably formed during diagenesis from decarboxylation of predominantly even-carbon-numbered aliphatic acids originating from higher plant or lacustrine algal sources and/or were directly biosynthesised in hydrocarbon form. At least two other homologous series of branched/cyclic HMWHCs were observed, one of which was confirmed as a series of branched alkanes (probably methyl-branched). The carbon number distribution patterns of HMWHCs may be primarily controlled by thermal maturity and biogenic source input as well as being influenced by diagenetic reactions governed by depositional environmental conditions, as shown previously [Carlson, R.M.K., Teerman, S.C., Moldowan, J.M., Jacobson, S.R., Chan, E.I., Dorrough, K.S., Seetoo, W.C., Mertani, B., 1993. High temperature gas chromatography of high wax oils. In: Indonesian Petroleum Association, 22nd Annual Convention Proceedings. Jakarta, Indonesian, pp. 483–507. Carlson, R.M.K., Jacobsen, S.R., Moldowan, J.M., Chan E.I., 1994. Potential application of high temperature gas chromatography to Middle Eastern petroleum exploration and production. In: Al-Husseini, M.I. (Ed.), Geo'94, Vol 1., Selected Middle East Papers from The Middle East Petroleum Geoscience Conference, 1994; Gulf PetroLink. Manama, Bahrain, pp. 258–267]. Our study indicates for the first time that Es3 source rocks as well as Es4 facies contain HMWHCs. The distributions of extractable wax hydrocarbons suggest that both Es4 and Es3 members may potentially serve as important parent source rocks for generating waxy petroleum in this region.  相似文献   

15.
In certain areas, relatively large accumulations of liquid hydrocarbons have been attributed to coals. Evaluating the source rock potential of coal requires definition of both the generative potential (quantity and composition of generated hydrocarbons), and expulsion efficiency. Hydrous pyrolysis experiments were completed using Tertiary lignites (Ro < 0.35%) from North Dakota and the Far East to evaluate the source rock potential of coal. The North Dakota lignite is vitrinite-rich (93%) and liptinite-poor (3%); the Far East lignite is liptinite-rich (32% of total maceral content). These lignites have Hydrogen Index values of 123 and 483 mg HC/g OC, respectively. Differences in oil-pyrolysate yield, composition, and temperature of maximum pyrolysate yield from hydrous pyrolysis experiments for these two lignites are related to the type and amount of liptinite and vitrinite macerals. A maximum of 48 and 158 mg oil-pyrolysate/g OC is generated and expelled from the North Dakota and Far East lignites, respectively. Although these lignites consist predominantly of gas-prone vitrinitic components, their organic-rich nature can compensate for their poor convertibility to liquid hydrocarbons. The composition of these artificially generated oil-pyrolysates are similar to some non-marine oils, suggesting that this type of organic matter can be a significant contributor to many oils. Although the overall composition of the generated products from the two lignites is similar, the distribution of these products is significantly different. Homologous series of methyl ketones and alkyl benzenes have been identified in both oil-pyrolysates. Their presence and characteristic distribution suggest that microbial degradation occurred during the formation of these lignites. Although many coals generate significate amounts of liquid hydrocarbons that are similar to naturally occurring oils, poor explusion efficiency limits their source rock potential. Significant amounts of liquid products are assimilated by the vitrinitic matrix of most coals prior to expulsion, severely limiting the amount of petroleum available for migration and reservoir accumulation. However, adequate expulsion may occur in certain liptinite-rich coals or coals occurring in unique depositional settings.  相似文献   

16.
In the lower parts of oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation are oil-bearing layers newly found in oil exploration in the Ordos Basin.Based on GC,GC-MS analyses of saturated hydrocarbons from crude oils and source rocks,reservoir fluid inclusions and BasinMod,the origin of crude oils,accumulation period and accumulation models are discussed in combination with other petroleum geology data in this paper.The result shows that(1) there are two different types of crude oils in oil reservoir Chang 9 in the Longdong and Jiyuan regions:crude oils of typeⅠ(Well D86,Well A44,Well A75,Well B227,Well X62 and Well Z150) are mainly de-rived from the Chang 7 source rocks(including mudstones and shales) and distributed in the Jiyuan and Longdong regions;those of typeⅡ(Well Z14 and Well Y427),are distributed in the Longdong region,which are derived from the Chang 9 source rocks.Crude oils from oil reservoir Chang 10 in the Shanbei region are mainly derived from the Chang-9 source rocks;(2) there are two phases of hydrocarbon filling in oil reservoir Chang 9 in the Jiyuan and Longdong regions and oil reservoir Chang 10 in the Shanbei region:The first phase started at the early stage of J2z.The process of hydrocarbon filling was discontinuous in the Late Jurassic,because of the tectonic-thermal event in the Ordos Basin.The second phase was the main accumulation period,and hydrocarbons began to accumulate from the late stage of J2a to the middle-late of K1,mainly at the middle-late stage of K1;(3) there exist two types of accu-mulation models in oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation:source rocks of the reservoirs in oil reservoir Chang 9 in the Jiyuan region and oil reservoir Chang 10 in the Shanbei region,the mixed type of reservoirs on the lateral side of source rocks and source rocks of the reservoirs in oil reservoir Chang 9 in the Long-dong region.  相似文献   

17.
A suite of 27 oils from the Qinjiatun–Qikeshu oilfields in the Lishu Fault Depression of the Songliao Basin was analyzed using whole oil gas chromatography. In combination with the relative distribution of C27, C28, and C29 regular steranes, detailed geochemical analyses of light hydrocarbons in oil samples revealed crude oils characterized by the dual input of lower aquatic organisms and higher terrestrial plants. Several light hydrocarbon indicators suggest that the liquid hydrocarbons have maturities equivalent to vitrinite reflectances of around 0.78%–0.93%. This is consistent with the maturity determination of steranes C29 20S/(20S + 20R) and C29 ααβ/(ααα + αββ). Crude oils derived from the two distinct oilfields likely both have source rocks deposited in a lacustrine environment based on light hydrocarbon parameters and on higher molecular weight hydrocarbon parameters. The results show that light hydrocarbon data in crude oils can provide important information for understanding the geochemical characteristics of the Qinjiatun–Qikeshu oils during geologic evolution.  相似文献   

18.
<正>The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution.For this reason,the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area.Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks,i.e.,heavy oils are distributed in the TZ47-15 well-block in the North Slope while normal and light oils in the No.Ⅰfault belt and the TZ16 well-block,which means that the oil properties are controlled by structural patterns.Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks,suggesting a good genetic relationship. However,the compound specific isotope of n-alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the Mid-Upper Ordovician and the Cambrian-Lower Ordovician source rocks.Most Silurian oils have a record of secondary alterations like earlier biodegradation,including the occurrence of "UCM" humps in the total ion current(TIC) chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils,and regular changes in the abundances of light and heavy components from the structural low to the structural high.The fact that the Silurian oils are enriched in chain alkanes,e.g.,n-alkanes and 25-norhopane,suggests that they were mixed oils of the earlier degraded oils with the later normal oils.It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions.The migration and accumulation models of these oils in the TZ47-15 well-blocks,the No.Ⅰfault belt and the TZ16 well-block are different from but related to each other.The investigation of the origin of the mixed oils and the hydrocarbon migration and accumulation mechanisms in different charging periods is of great significance to petroleum exploration in this area.  相似文献   

19.
Asphaltenes and NSO fractions from a variety of oils and tar sands have been characterized by pyrolysis-gas chromatography (Py---GC) using both flame ionization and flame photometric detectors. Organosulphur compounds were not always produced by pyrolysis of the asphaltenes isolated from the biodegraded tar sand extracts although pyrolysis of the NSO fractions produced a series of thiophenes from all of the samples examined. These observations suggest that under certain conditions, asphaltene fractions may be affected by biodegradation, leading to preferential removal of the sulphur containing compounds. In addition, it was observed that Py---GC of asphaltenes permitted oils to be differentiated on the basis of their source rock lithology. Oils derived from carbonate source rocks produced thiophene/benzothiopene ratios <1 whilst the same ratio was >1 for oils derived from shales. Thiophene/dibenzothiophene ratios could be used in a similar manner.  相似文献   

20.
Pyrolysis kinetics are determined for a series of asphaltene samples associated with different types of kerogens. The activation energy distributions obtained for asphaltenes related to type I kerogens cover a wide range, with significant hydrocarbon generation with activation energies above 350 kJ/mol. The ranges of activation energy distributions are relatively narrow for asphaltenes associated with type II and III kerogens, with little hydrocarbons generated with activation energies above 350 kJ/mol. If the type of associated kerogen can be reasonably constrained, the pyrolysis kinetics of the asphaltenes is potentially a very useful tool for assessing the maturity levels of reservoired oils. The results of pyrolysis kinetics indicate that there is still significant potential for asphaltenes to regenerate hydrocarbons.  相似文献   

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