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1.
Pyrolysis of asphaltenes from crude oils yields significant amounts of crude oil-like material. Studies of asphaltenes and their pyrolysis products from biodegraded and non-biodegraded oils show that biodegradation does not affect the composition of asphaltene. The overall composition of the oil produced from them on pyrolysis is similar to, yet significantly different from, that of the parent oil. From these compositional differences, it is concluded that asphaltene and its pyrolysis products contain geochemical information which is characteristic, and therefore may shed light on the history of the oil prior to asphaltene formation. 相似文献
2.
Hydrous pyrolysis of asphaltenes has been tested as a method to reconstruct the chemical composition of biodegraded oils and oil seeps. The asphaltenes of three oils (a nondegraded oil, a biodegraded oil, and a biodegraded oil seep) from the Monterey Formation were studied. Results show that the aliphatic fraction generated by hydrous pyrolysis is very similar in chemical composition to the non-degraded oil. This makes the method very useful in correlation studies of biodegraded and nondegraded oils. It also allows to roughly estimate the maturity of the source of the biodegraded oil or oil seep. 相似文献
3.
Biodegradation and migrational fractionation of oils from the Eastern Carpathians, Poland 总被引：1，自引：0，他引：1
Nineteen oil samples from Silesian Unit of the eastern Carpathian Overthrust have been characterised geochemically in order to determine the causes of compositional differences among them and elucidating the processes responsible for their differences. Some of analysed crude oils have undergone post-emplacement alteration in the reservoir such as biodegradation and evaporative fractionation. This explains much of the chemical and physical properties variability across individual fields from one tectonic unit. Geochemical correlation based on biomarker distributions showed a close relationship between all oils (included biodegraded oils). However, data based on the whole oil GC analysis of selected oils suggest that the process of evaporative fractionation may change the composition of lower molecular weight hydrocarbons of the oils in this region. This paper outlines the probable mechanisms for oil mixing in the region and describes how this can lead to observable lateral differences in the composition of oils. 相似文献
4.
Eric Lehne Volker Dieckmann Rolando di Primio Andreas Fuhrmann Brian Horsfield 《Organic Geochemistry》2009,40(5):604-616
Asphaltenes extracted from crude oils are proposed to possess structural features of the related source rock kerogen. For the present study micro-scale sealed vessel pyrolysis (MSSV) and combustion isotope ratio mass spectrometry (GC–C–IRMS) were used to compare gas generation from a whole rock (type II-S kerogen) from southern Italy with that from related sulfur rich asphaltenes isolated from a low maturity heavy crude oil. The purpose of was to determine whether experimental pyrolysis of oil asphaltenes can be used to predict the timing and the chemical and isotopic composition of hydrocarbon gases generated from genetically related kerogen in the source rock during burial maturation. The results show that parameters such as (gas to oil ratio) GOR and oil and gas formation timing are very similar for these two sample types, whereas gas composition, product aromaticity and sulfur content are remarkably different. Slight differences in GOR are mainly due to differences in gas formation characteristics at very high levels of thermal alteration. Secondary gas formation from the whole rock covers a much broader temperature range under geological conditions than that from the asphaltene products. However, it is remarkable that both the onset and the maximum temperature are nearly identical under geological conditions. The observed differences in gas generation characteristics are supported by discrepancies in the carbon isotopic characteristics of the gas range compounds and indicate different precursors and/or mechanisms for gas generated from whole rock and asphaltenes. 相似文献
5.
Ger Van Graas 《Organic Geochemistry》1986,10(4-6)
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
6.
Jing Zhao Zewen Liao Lühui Zhang Patrice Creux Chupeng Yang Anna Chrostowska Haizu Zhang Alain Graciaa 《Applied Geochemistry》2010
Being the heaviest fraction of crude oils, asphaltenes are liable to aggregate, and other molecules in the oils can be steadily adsorbed onto, and even occluded inside the macromolecular structures of the asphaltenes. These occluded compounds inside the asphaltenes can survive over geological time in oil reservoirs owing to effective protection by the macromolecular structures of the asphaltenes. The asphaltenes of a crude oil (ZG31) from the central Tarim Basin, NW China, were hierarchically degraded by increasing the amount of H2O2/CH3COOH to release the occluded compounds. Besides the common components, series of even numbered n-alk-1-enes and 3-ethylalkanes were detected among the occluded compounds. Comparison of the biomarker distributions and the compound-specific C isotopic results between the compounds from the maltenes and those from the occluded fraction, the ZG31 reservoir was suggested to have been charged multiple times, with different charges being derived from different strata of source rocks. 相似文献
7.
More than 100 crude oils and 12 oil sands from Alberta, Canada, from stratigraphie units ranging in age from Upper Cretaceous to Middle Devonian, were processed to separate the asphaltenes which were then analysed for C, H, N, O and S and the ESR spectra run to determine g-value, spin number and line width. A factor analysis of these data, together with selected crude oil and reservoir properties, was interpreted in terms of a number of non-thermal processes which can affect the content and composition of asphaltenes during and after thermal maturation. Experiments on the effect of temperature on the signal intensity of free radicals indicate that more than half, and possibly all, the free radicals observed in asphaltenes must arise from charge transfer or closely related equilibria. An important solvent effect is demonstrated in further experiments, in which the more polar the solvent, the more the solvent dispersive forces overcome the associative forces of the asphaltene layers thus leading to lower molecular weights and a change in the charge transfer forces responsible for the ESR signal. The average molecular weight of asphaltenes from heavy, asphaltic, biodegraded crude oils and oil sands is considerably greater than the average molecular weight of asphaltenes from the more paraffinic, mature, non-biodegraded crude oils, and it seems likely that the differences in molecular weight of these asphaltenes are due to the solvent effect of the crude oils, and thus the laboratory observations have been confirmed in the Alberta basin. 相似文献
8.
Measurements of the absolute and relative concentrations of nitrogen-containing compounds in crude oils from different reservoir strata (Ordovician, Silurian and Carboniferous) in the Tazhong region of the Tarim Basin, Xinjiang, China, showed that even though there are quite a number of factors affecting the distributional and compositional characteristics of neutral nitrogen-containing compounds in crude oils, the distributional and compositional characteristics of crude oils whose source conditions are approximate to one another are influenced mainly by the migration and fractionation effects in the process of formation of oil reservoirs. In addition, crude oils in the Tazhong region show obvious migration-fractionation effects in the vertical direction. Carboniferous crude oils are characterized by high migration parameters and low compound concentrations, just in contrast to Ordovician crude oils. This indicates that crude oils from shallow-level oil reservoirs were derived from those of deep-level oil reservoirs via faults, unconformable contact or carrier beds. Crude oils from the Tazhong region show some migration-fractionation effects in the lateral direction, but mixing of crude oils derived from different hydrocarbon source rocks in the process of formation of oil reservoirs made it more complicated the migration and accumulation of crude oils, as well as the formation of oil reservoirs. 相似文献
9.
We generalized experimental data on the structural group composition and macrostructural characteristics of high-molecular compounds (HMCs)—hydrocarbons, resins, and asphaltenes—from more than 180 crude oil samples extracted from different oil fields of Eurasia. Most of oil resin molecules contain 1–3 structural blocks, each consisting of 0–3 aromatic and 0–5 naphthenic rings in different combinations, with the total number of rings in each block not exceeding 5–6. The average molecular weights of resins are no more than 100–1500 a.m.u. Asphaltenes differ from resins from the same source in the larger number of structural blocks (mainly tri- or tetracyclic aromatic) in molecule (up to five), lower degrees of substitution of aromatic cores, and smaller portions of carbon atoms in saturated fragments. The average molecular weights of asphaltenes measured by naphthalene cryoscopy do not exceed 2500 a.m.u. Owing to intermolecular interactions, HMCs form various associates and polymolecular particles, including quasi-crystalline “batches” and multibatch aggregates. Spontaneous disintegration and formation of such particles make the oils dynamically equilibrium polydisperse systems. We have developed the main regularities of compositional and structural changes of HMCs depending on the depth of occurrence, age, and lithologic composition of oil-bearing deposits. Being chemically labile heteroatomic substances, petroleum HMCs are more rapidly subjected to compositional and structural transformations than hydrocarbons, i.e., are more responsive to changes in strata conditions. 相似文献
10.
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
11.
This paper deals with natural temperature records in the heavy (asphaltenes) and the light fractions (C7—light hydrocarbons) of petroleum. Two sets of marine oils formed from different source rocks and petroleum systems were studied using asphaltene kinetics and light hydrocarbon analysis. Both fractions have been reported to contain information about the temperature the respective oils have been exposed to in the subsurface. These indicated temperatures generally correspond to the conditions in the source rock when expulsion occurred. Bulk kinetic analysis of reservoir oil asphaltenes as well as light hydrocarbon (LH) analysis (of dimethylpentanes) were used here in order to evaluate the expulsion temperatures. Surprisingly, when considering information coming from both fractions, an inverse trend between LHs expulsion temperatures (Ctemp) and asphaltenes (Tasph.) can be observed—high Tasph (asphaltene temperatures) occur with low LH Ctemp (light hydrocarbon expulsion temperatures) and low Tasph can be observed when Ctemp is high. These differences are of fundamental importance for the use of such geochemical data in calibrating numerical basin models. The reason for this inverse behaviour is possibly due to the different expulsion behaviour of light hydrocarbons and the heavy fraction of oils, especially when the source rocks contain only moderate amounts of organic matter. In addition it has to be considered that the temperature predictions obtained using asphaltene kinetic analysis are related to the onset temperature of petroleum expulsion, while light hydrocarbons provide, at best, average expulsion temperatures. 相似文献
12.
The objective of this study is to demonstrate the basic characteristics of Bacillus SP3 and evaluate its effect on different crude oils. Strain SP3 is a motile, gram-positive, spore-producing rod that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain SP3 grew at high temperatures up to 58℃ at the pH range of 5.5–8.5. Strain SP3 grew facultatively and could use different organic substrates, and produce some metabolites such as 4-hydroxy-4-methyl-2-pentanone, methyl-2-nitrogen benzene and 1, 2-benzenedicarboxylic acid bis ester. Laboratory studies have demonstrated that the strain converted and degraded different components and changed the physical and chemical properties of crude oils. Strain SP3 degraded crude oil and the growth of bacteria on crude oil resulted in loss of aromatic hydrocarbons, resins and asphaltenes. The bioconversion of crude oils would lead to an enrichment in lighter hydrocarbons and an overall redistribution of saturate hydrocarbons. The interactions of microorganisms with crude oils are variable, depending on the microbial species and the chemical compositions of crude oils. 相似文献
13.
柴达木盆地原油碳同位素组成的主控因素与成因类型 总被引：9，自引：5，他引：9
对采集于柴达木盆地16个油田的40个原油进行了碳同位素测定,研究了它们碳同位素组成特征、主控因素及其成因类型。结果表明,柴达木盆地西部地区和北部地区原油碳同位素组成具有显著的差别,西部地区原油富集13C,北部地区原油富集12C。研究发现,成油环境(如盐度和湿度)是决定西部盐湖相原油碳同位素组成及其变化的主要因素,母源性质则控制了北部淡水湖沼相原油的碳同位素组成和变化。根据原油的碳同位素组成和Ph/nC18比值特征,将柴达木盆地原油划分为五种成因类型。 相似文献
14.
A group of 44 crudes from the Eastern Venezuela Basin have been analyzed for their content of saturated and aromatic hydrocarbons, resins, and asphaltenes, and studied for their variation of viscosity with temperature. With respect to a general trend, heavy oils that flow with ease, and light oils that flow with difficulty have been found. A ‘limiting value’ of 2.3 of saturates/asphaltenes separates oils whose viscosity can be changed with ease or difficulty by chemical means. 相似文献
15.
《Applied Geochemistry》2005,20(10):1974-1983
Problems related to the crystallization and deposition of heavy organic fractions during production, transportation and storage of crude oils can lead to considerable financial losses for the petroleum industry. The heavy organic fractions may include paraffins or waxes, resins, asphaltenes, and organometallic compounds that exist in crude oils in various quantities, states, and forms. The severity of the deposition problems varies widely and depends on factors such as the crude oil composition, operating conditions in the reservoir and production procedures. Problems associated with the solid deposits may be encountered anywhere in the production process from the reservoir to the refinery. In this paper, it is proposed to focus on production problems associated with certain fields in Tunisia. The problems manifested themselves through the accumulation of solid deposits in the storage tanks at a Tunisian terminal and originated from the mixtures of various crude oils transported to the terminal by pipeline. The principal analytical method for the characterization of the solids was high temperature gas chromatography following concentration of the wax fraction through a modification of the conventional acetone precipitation technique. 相似文献
16.
Simon C George Christopher J Boreham Sandra A Minifie Stan C Teerman 《Organic Geochemistry》2002,33(12)
A suite of 18 oils from the Barrow Island oilfield, Australia, and a non-biodegraded reference oil have been analysed compositionally in order to detail the effect of minor to moderate biodegradation on C5 to C9 hydrocarbons. Carbon isotopic data for individual low molecular weight hydrocarbons were also obtained for six of the oils. The Barrow Island oils came from different production wells, reservoir horizons, and compartments, but have a common source (the Upper Jurassic Dingo Claystone Formation), with some organo-facies differences. Hydrocarbon ratios based on hopanes, steranes, alkylnaphthalenes and alkylphenanthrenes indicate thermal maturities of about 0.8% Rc for most of the oils. The co-occurrence in all the oils of relatively high amounts of 25-norhopanes with C5 to C9 hydrocarbons, aromatic hydrocarbons and cyclic alkanes implies that the oils are the result of multiple charging, with a heavily biodegraded charge being overprinted by fresher and more pristine oil. The later oil charge was itself variably biodegraded, leading to significant compositional variations across the oilfield, which help delineate compartmentalisation. Biodegradation resulted in strong depletion of n-alkanes (>95%) from most of the oils. Benzene and toluene were partially or completely removed from the Barrow Island oils by water washing. However, hydrocarbons with lower water solubility were either not affected by water washing, or water washing had only a minor effect. There are three main controls on the susceptibility to biodegradation of cyclic, branched and aromatic low molecular weight hydrocarbons: carbon skeleton, degree of alkylation, and position of alkylation. Firstly, ring preference ratios at C6 and C7 show that isoalkanes are retained preferentially relative to alkylcyclohexanes, and to some extent alkylcyclopentanes. Dimethylpentanes are substantially more resistant to biodegradation than most dimethylcyclopentanes, but methylhexanes are depleted faster than methylpentanes and dimethylcyclopentanes. For C8 and C9 hydrocarbons, alkylcyclohexanes are more resistant to biodegradation than linear alkanes. Secondly, there is a trend of lower susceptibility to biodegradation with greater alkyl substitution for isoalkanes, alkylcyclohexanes, alkylcyclopentanes and alkylbenzenes. Thirdly, the position of alkylation has a strong control, with adjacent methyl groups reducing the susceptibility of an isomer to biodegradation. 1,2,3-Trimethylbenzene is the most resistant of the C3 alkylbenzene isomers during moderate biodegradation. 2-Methylalkanes are the most susceptible branched alkanes to biodegradation, 3-methylalkanes are the most resistant and 4-methylalkanes have intermediate resistance. Therefore, terminal methyl groups are more prone to bacterial attack compared to mid-chain isomers, and C3 carbon chains are more readily utilised than C2 carbon chains. 1,1-Dimethylcyclopentane and 1,1-dimethylcyclohexane are the most resistant of the alkylcyclohexanes and alkylcyclopentanes to biodegradation. The straight-chained and branched C5–C9 alkanes are isotopically light (depleted in 13C) relative to cycloalkanes and aromatic hydrocarbons. The effects of biodegradation consistently lead to enrichment in 13C for each remaining hydrocarbon, due to preferential removal of 12C. Differences in the rates of biodegradation of low molecular weight hydrocarbons shown by compositional data are also reflected in the level of enrichment in 13C. The carbon isotopic effects of biodegradation show a decreasing level of isotopic enrichments in 13C with increasing molecular weight. This suggests that the kinetic isotope effect associated with biodegradation is site-specific and often related to a terminal carbon, where its impact on the isotopic composition becomes progressively ‘diluted’ with increasing carbon number. 相似文献
17.
The hydrocarbon occurrences of asphalts, heavy oils and oil shales in the Dead Sea area and the possible genetic relation between them have been studied. The similarity in organochemical characteristics, i.e., the elemental composition of asphaltenes, the distribution pattern of the saturated hydrocarbons and the predominance of V (over Ni)-porphyrins in both the oils and the asphalts indicate a close relation between them. On the other hand, dissimilarities in the same organochemical characteristics in both the asphalts and the oil shale exclude the hypotheses that asphalt was generated and expelled from the oil shales or that the shales were contaminated by oils. Water washing and biodegradation are considered to be the processes through which preferential depletion of hydrocarbons occurred, altering the oils to asphalts. The burial of the degraded asphalt to a relatively great depth resulted in a secondary generation of small amounts of light saturated hydrocarbons in these asphalts. The oils, which are thought to be the precursors of the asphalts, have either been flushed into the Dead Sea depression from the surrounding elevated areas or have seeped upwards from deep local accumulations in the graben. 相似文献
18.
Qin Kuangzong 《Organic Geochemistry》1988,13(4-6)
Two Chinese immature oil shales from the continental deposits of kerogen type I and II have been thermally treated combined with the technique of supercritical fluid extraction at 630–650 K and 15–25 MPa in a semi-continuous laboratory scale apparatus. Toluence is selected as the solvent. Up to 70–80% of the kerogen matrix can be converted to a thermal bitumen and extracted simultaneously. The chemical structural parameters from the NMR, IR, XRD, ESR and EA analyses of the kerogen and the thermal bitumen show striking resemblance in nature. It implies that the thermal bitumen is primarily a depolymerized product of the kerogen. Based on the GC/MS spectra of the aliphatic eluate of the thermal bitumen, the predominance of the odd/even ratio of the alkanes and the epimeric ratios, such as 20S(20S + 20R) of C-29 steranes and 22S/(22S + 22R) of C-32 terpanes, show that the maturity of the thermal bitumen from these oil shales is comparable to that of commercial immature oils from East China. The thermal bitumen is thought to be an intermediate product of the thermal degradation of kerogen.Since the thermal bitumen is mainly composed of asphaltenes and resins, it has a structure of gel. The gel-state bitumen may turn to sol-state readily due to its low aromaticity and polarity, or due to selective adsorption of asphaltenes by clay minerals. Then the migration potential of the bitumen is enhanced.Consequently, under favorable geological conditions, the thermal depolymerization of kerogen seems to be a probable mechanism to explain the formation of immature oils. 相似文献
19.
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
20.
东濮凹陷原油、油砂抽提物与油气包裹体地球化学对比及其意义 总被引：9，自引：0，他引：9
通过对东濮凹陷桥口构造Q27井和Q55井原油、油砂抽提物和油气包裹体族组成和分子地球化学对比．可以发现：(1)油砂抽提物由于含蜡量高，非烃、沥青质含量低，其饱和烃、芳烃含量甚至比原油高，非烃、沥青质含量甚至比原油低；(2)Q27原油样与从同一井段内采取的油砂抽提物甾、萜烷分布特征存在着较为明显的差异，表明采油井段的原油地球化学组成是不均一的；(3)两口井的油气包裹体甾、萜烷分子指标，包括油源指标和成熟度指标，与油砂抽提物和原油也均有明显的差异，表明在油气注入过程中原油的油源和成熟度是不断变化的。尽管该地区的原油均来自沙三段，但在不同时间注入的原油可能来自不同“亚层”或“不同分布区域”的沙三段烃源岩。 相似文献