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1.
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
2.
R.P. Philp 《Geochimica et cosmochimica acta》1983,47(2):267-275
The aliphatic hydrocarbon fractions of sixty oils from the San Jorges Basin, Argentina have been analysed by computerized-gas chromatography-mass spectrometry. The initial aim of this study was the correlation of the oils using sterane and triterpane biomarkers. The oils could be divided into four groups which were distinguished by the relative proportions of regular to demethylated hopanes. Although it has been previously suggested that the demethylated hopanes found in oils could have resulted from biotransformation of the oils in the reservoir, in this basin the possibility that these compounds originated directly from the source beds cannot be entirely eliminated since the oils do not appear to be extensively biodegraded on the basis of their aliphatic hydrocarbon distributions. An alternative theory for the hydrocarbon distributions observed in these oils, is initially biodegradation of the oils in the reservoir followed by addition of non-degraded oil to produce a mixture of degraded and non-degraded oil. 相似文献
3.
Hans Peter Nytoft 《Organic Geochemistry》2011,42(5):520-539
Novel side chain methylated and hexacyclic hopanes have been identified in coals and oils from around the world. Extended hopanes (>C32) with an additional methyl in the side chain (“isohopanes”) were identified by comparison with synthetic standards. The major C33-C35 isohopanes are 31-methylbishomohopanes, 32-methyltrishomohopanes and 33-methyltetrakishomohopanes. Extended hopanes methylated at C-29 were not detected. The 17α(H),21β(H)-31-methyltrishomohopanes show four peaks on gas chromatography because of the extra asymmetric carbon at C-31. Like regular hopanes, the isohopanes extend beyond C35. Low concentrations of novel hexacyclic hopanes having 35 or more carbons were also detected in oils and coal extracts. The C35 hexacyclic hopanes were identified as 29-cyclopentylhopanes. Isohopanes are released from the kerogen by hydrous pyrolysis and hydropyrolysis. The 22S/(22S + 22R) ratio for 31-methylbishomohopanes and other isohopanes is around 0.60 at equilibrium in geological samples. They isomerize slightly more slowly than regular C33 hopanes. Isohop-17(21)-enes, 2α-methylisohopanes and two series of rearranged isohopanes were tentatively identified. Isohopanes can be biodegraded to form the corresponding 25-norhopanes. When 25-norhopanes are not formed, the isohopanes are much more resistant to biodegradation than regular hopanes. In biodegraded oil seeps from Greece, 30-norisohopanes were tentatively assigned. The composition and relative abundance of C33 and C34 isohopanes in a worldwide set of coals and crude oils was determined. Isohopanes are abundant in coal and coal-generated oils, where they can account for more than 5% of all extended hopanes, and low in abundance in oils from source rocks deposited under anoxic conditions. 相似文献
4.
We have investigated the distributions of alkylcarbazoles in a series of crude oils with different biodegradation extents,
in combination with biomarker parameters, stable carbon isotopic ratios and viscosities. The analyses showed that slight biodegradation
has little effect on alkylcarbazoles. The concentrations of C0-, C1-, and C2-carbazoles seem to display a slight decrease with biodegradation through the moderately biodegraded stage, and an abrupt
decrease to the heavily biodegraded stage. The relative concentrations of C0-, C1-, and C2-carbazoles do not show any apparent change in the non-heavily biodegraded stages, but through non-heavily biodegraded to
heavily biodegraded stages, the percentages of C0- and C1-carbazoles decrease, and those of C2-carbazoles increase significantly, which may indicate that C2-carbazoles are more resistant to biodegradation than lower homologous species. As to C2-carbazole isomers, the relative concentrations of the pyrrolic N-H-shielded, pyrrolic N−H partially shielded and pyrrolic
N-H-exposed isomers do not show any obvious variation in the non-heavily biodegraded oil, but there is an abrupt change through
the mid-biodegraded stage to the heavily biodegraded stage.
This project was financially supported by the Youth Knowledge-Innovation Foundation of CNPC (No. 00Z1304). 相似文献
5.
借助色谱- 质谱（GC- MS）和色谱- 质谱- 质谱（GC- MS- MS）分析,对黔南坳陷凯里残余油藏凯棠和洛棉剖面上储层沥青中的烃类组成进行了系统分析,以判断其所遭受生物降解作用的程度,探寻在极端降解原油中是否还存在原生生物标志物,为这类原油的油源研究开拓新的途径和方法。结果表明：凯棠剖面上的储层沥青中尽管仍可检测到较为完整的C19- 30三环萜烷和C27- 35藿烷系列,但C19- 29脱甲基三环萜烷系列和C26- 34 25- 降藿烷系列丰富而完整,甾烷系列中C21- 22低分子量甾烷和重排甾烷优势明显,这一系列特征表明这些沥青遭受了剧烈生物降解作用的改造。但三芳甾类仍保存完好,依据原油生物降解程度的评判标准,判断其生物降解级别介于8~9级之间。洛棉剖面上的储层沥青中藿烷系列基本消失殆尽,三环萜烷系列及其脱甲基产物和25- 降藿烷系列的分布因极端生物降解作用而发生显著变异,某些化合物如C23T、C24T、C23NTE和C28- 29NH成为优势成员;甾烷系列中C21- 22低分子量甾烷占绝对优势,三芳甾类完全消失,据此判断该剖面上沥青的生物降解级别已达到10级或更严重。由于这两个剖面上的沥青遭受了极端生物降解作用的改造,常用的甾、萜类生物标志物完全失去了实用价值。但是,在所分析的这些沥青中都检测到三个系列的C27- 35 8,14- 开环藿烷系列,它们与塔里木盆地塔中地区海相端元油中存在的同类标志物的分布特征相似。正常海相端元油和极端生物降解沥青中同时检测到这三个系列的8,14- 开环藿烷,这一事实表明这类生物标志物在成因上具有原生性,而与生物降解作用无关。此外,在极端生物降解作用沥青中的完好保存,表明它们具有极强的抗生物降解能力,因而它们在此类原油的油源研究中可能具有潜在的实用价值。 相似文献
6.
《Applied Geochemistry》2002,17(1):1-10
The aliphatic hydrocarbon composition (acyclic isoprenoids, hopanoids and steroids) of oils from the most productive fields in the southern geological Province of Cuba have been studied. This province is defined by its position with respect to the Cretaceous overthrust belt generated during the formation of oceanic crust along the axis of the proto-Caribbean Basin. The relative abundances of 18α(H)-22,29,30-trisnorneohopane, gammacerane and diasteranes suggest that Pina oils are related to the carbonate oils from the Placetas Unit in the northern province (low Ts/(Ts+Tm) and C27,29 rr/(rr+sd) ratios). The Cristales and Jatibonico oils exhibit some differentiating features such as higher Ts/(Ts+Tm) and absence of gammacerane. The oils from this province do not exhibit significant differences in either hopane, C32 22S/(S+R) and C30 αβ/(αβ+βα), or sterane, C29 αα 20S/(S+R), maturity ratios. However, the relative content of 5α(H),14β(H),17β(H)-cholestanes (C29 ββ/(ββ+αα) ratio) indicates that Pina oils are more mature than Cristales and Jatibonico oils. Several of these oils (Cristales, Jatibonico and Pina 26) are heavily biodegraded, lacking n-alkanes, norpristane, pristane and phytane (the two former oils do not contain acyclic isoprenoid hydrocarbons). Other biodegradation products, the 25-norhopanes, are found in all the oils. Their occurrence is probably due to mixing of severely biodegraded oil residues with undegraded crude oils during accumulation in the reservoir. 相似文献
7.
对渤海湾盆地一系列生物降解原油的色谱-质谱分析结果表明,庙西凹陷PL15-8D与PL9-4井四个严重生物降解原油三环萜烷系列分布较为异常,主要表现为以C23为主峰的后峰型、C20与C23为主峰的微弱双峰型以及以C20与C24为主峰的双峰型分布模式。强烈的生物降解作用导致C19~C23三环萜烷优先于C24+三环萜烷被不同程度地侵蚀,是形成这一异常分布的根本原因。三环萜烷系列相对丰度与绝对浓度的变化规律表明,不同碳数三环萜烷的生物降解作用同时发生,但其降解速率有明显差别,即抗生物降解能力不同。三环萜烷系列化合物（除C20三环萜烷以外）的抗生物降解能力具有随碳数增加而增强的趋势,而C20三环萜烷抗降解能力似乎强于C21~C23三环萜烷。原油中未检测到脱甲基三环萜烷,表明三环萜烷的降解并非通过微生物的脱甲基化作用,推测其降解途径是微生物氧化三环萜烷C环支链末端的甲基,形成对应的羧酸化合物。四个原油样品甾烷、藿烷与三环萜烷被微生物严重侵蚀,不能用于油源对比研究,而三芳甾烷未受生物降解影响,可作为研究区严重生物降解原油油源对比的有效指标。 相似文献
8.
通过对TZ62井原油进行热模拟实验,探讨热演化程度对原油中重排藿烷类化合物形成分布的影响及其地球化学意义。实验发现：在400～500 ℃阶段,随着热演化程度的增加,原油中高碳数微晶蜡类长链化合物热裂解和原油中的沥青质热降解作用对重排藿烷的形成具有贡献作用。在500～550 ℃对应的原油裂解高峰阶段,藿烷类化合物浓度明显降低,且17α(H)-藿烷比重排藿烷类化合物具有更快的热裂解速率。在温度为550～600 ℃阶段,较高的热演化程度对17α(H)-藿烷甲基重排作用形成重排藿烷具有贡献作用。重排藿烷参数(17α(H)-重排藿烷/17α(H)-藿烷、Ts/Tm)在400～500 ℃变化较弱,几乎不受热演化程度的影响;在500～550 ℃的原油裂解高峰阶段,逐渐增大;在550～600 ℃发生反转,逐渐减小。重排藿烷参数可作为高成熟阶段原油成熟度判识的有效参数,其有效应用范围是生油窗晚期至原油裂解高峰期。 相似文献
9.
Origin and occurrence of 25-norhopanes: a statistical study 总被引：1，自引：0，他引：1
The alkane fraction of more than 200 rocks, biodegraded oils and non-biodegraded oils, have been analysed by means of computerized GC-MS, in order to investigate the effect of natural biodegradation on the occurrence of “demethylated hopanes”, i.e. 17α-25-norhopanes. The results obtained indicate that 25-norhopanes are preexisting biomarkers the concentration of which is enhanced by selective biodegradation of more readily degradable homologs, i.e. regular hopanes, rather than by demethylation of hopanes in reservoirs. However, the use of 25-norhopane enrichment as a palaebiodegradation indicator in apparently non-biodegraded oils is still valuable providing the initial background content in the corresponding source rocks is known. Furthermore, 25-norhopanes appear to be diagnostic of specific environmental conditions (marine and lacustrine source rocks, dysoxic and not very hypersaline). Lastly, one other (novel) bacterially resistant rearranged hopanoic compound, namely a C29 neohopane, is applicable for both biodegradation and maturation evaluation. 相似文献
10.
Light hydrocarbons (LHs) are one of the main petroleum fractions in crude oils, and carry much information regarding the genetic origin and alteration of crude oils. But secondary alterations—especially biodegradation—have a significant effect on the composition of LHs in crude oils. Because most of the LHs affected in oils underwent only slight biodegradation (rank 1 on the biodegradation scale), the variation of LHs can be used to describe more the refined features of biodegradation. Here, 23 crude oils from the Dawanqi Oilfield in the Tarim Basin, NW China, eleven of which have been biodegraded to different extents, were analyzed in order to investigate the effect of slight to minor biodegradation on C6–C7 LHs. The study results showed that biodegradation resulted in the prior depletion of straight-chained alkanes, followed by branched alkanes. In slight and minor biodegraded oils, such biodegradation scale could not sufficiently affect C6–C7 cycloalkanes. For branched C6–C7 alkanes, generally, monomethylalkanes are biodegraded earlier than dimethylalkanes and trimethylalkanes, which indicates that branched alkanes are more resistant to biodegradation, with the increase of substituted methyl groups on parent rings. The degree of alkylation is one of the primary controlling factors on the biodegradation of C6–C7 LHs. There is a particular case: although 2,2,3-trimethylbutane has a relative higher alkylation degree, 2,2-dimethylpentane is more resistant to biodegradation than 2,2,3-trimethylbutane. 2,2-Dimethylpentane is the most resistant to biodegradation in branched C6–C7 alkanes. Furthermore, the 2-methylpentane/3-methylpentane and 2-methylhexane/3-methylhexane ratios decreased steadily with increasing biodegradation, which implies that isomers of bilateral methyl groups are more prone to bacterial attack relative to mid-chain isomers. The position of the alkyls on the carbon skeleton is also one of the critical factors controlling the rate of biodegradation. With increasing biodegradation, Mango’s LH parameters K1 values decrease and K2 values increase, the values of n-heptane and isoheptane decrease, and the indices of methylcyclohexane and cyclohexane increase. LH parameters should be applied cautiously for the biodegraded oils. Because biodegraded samples belong to slight or minor biodegraded oils, the values of n-heptane and isoheptane from Dawanqi Oilfield can better reflect and determine the “Biodegraded” zone. When the heptane value is 0–21 and the isoheptane value is 0–2.6, the crude oil in Dawanqi Oilfield is defined as the “Biodegraded” zone. 相似文献
11.
The Qinjiatun and Qikeshu oilfields are new Mesozoic petroleum exploration targets in Lishu Fault Depression of Songliao Basin, northeastern China. Currently, researches on geochemistry of crude oils from Qinjiatun and Qikeshu oilfields have not been performed and the genesis of oils is still uncertain. Based on bulk analyses, the crude oils in the Qinjiatun and Qikeshu oilfields of Lishu Fault Depression from the Lower Cretaceous can be classified as three types. TypeⅠoils, from Quantou and Denglouku formations of Qikeshu oilfield, are characterized by high C24tetracyclic terpane/C26tricyclic terpanes ratios, low gammacerance/C30hopane ratios, tricyclic terpanes/hopanes ratios, C29Ts/C29norhopane ratios and 17α(H)-diahopane/17α(H)-hopane ratios, indicating a brackish lacustrine facies. TypeⅡoils, from Shahezi Formation of Qikeshu oilfield show low C24tetracyclic terpane/C26tricyclic terpanes, high gammacerance/C30hopane ratios, tricyclic terpanes/hopanes ratios, C29Ts/C29 norhopane and C30diahopane/C30hopane ratios, thus suggesting that they originated from source rocks deposited in a weak reducing brackish lacustrine environment, or clay-rich sediments. Type oilsⅢ, from some wells of Qikeshu oilfield have geochemical characteristics intermediate between those two types and may be mixture of typeⅠand Ⅱoils. 相似文献
12.
The effect of biodegradation on polycyclic aromatic hydrocarbons in reservoired oils from the Liaohe basin, NE China 总被引：3，自引：0，他引：3
Haiping Huang Bernard F.J. Bowler Thomas B.P. Oldenburg Steve R. Larter 《Organic Geochemistry》2004,35(11-12):1619
The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) has been studied in oil columns from the Liaohe basin, NE China, characterized by varied degrees of biodegradation. The Es3 oil column has undergone light to moderate biodegradation – ranging from levels 2 to 5 on the [Peters, K.E., Moldowan, J.M., 1993. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. Prentice Hall, Englewood Cliffs, NJ, p. 363] scale (abbreviated as ‘PM level’) – while the shallower Es1 column has undergone more severe biodegradation, ranging from PM level 5 to 8. Both columns show excellent vertical biodegradation gradients, with degree of biodegradation increasing with increasing depth toward the oil–water contact (OWC). The compositional gradients in the oil columns imply mass transport control on degradation rates, with degradation occurring primarily at the OWC. The diffusion of hydrocarbons to the OWC zone will be the ultimate control on the maximum degradation rate. The chemical composition and physical properties of the reservoired oils, and the ‘degradation sequence’ of chemical components are determined by mixing of fresh oil with biodegraded oil.The PAH concentrations and molecular distributions in the reservoired oils from these biodegraded columns show systematic changes with increasing degree of biodegradation. The C3+-alkylbenzenes are the first compounds to be depleted in the aromatic fraction. Concentrations of the C0–5-alkylnaphthalenes and the C0–3-alkylphenanthrenes decrease markedly during PM levels 3–5, while significant isomer variations occur at more advanced stages of biodegradation (>PM level 4).The degree of alkylation is a critical factor controlling the rate of biodegradation; in most cases the rate decreases with increasing number of alkyl substituents. However, we have observed that C3-naphthalenes concentrations decrease faster than those of C2-naphthalenes, and methylphenanthrenes concentrations decrease faster than that of phenanthrene. Demethylation of a substituted compound is inferred as a possible reaction in the biodegradation process.Differential degradation of specific alkylated isomers was observed in our sample set. The relative susceptibility of the individual dimethylnaphthalene, trimethylnaphthalene, tetramethylnaphthalene, pentamethylnaphthalene, methylphenanthrene, dimethylphenanthrene and trimethylphenanthrene isomers to biodegradation was determined. The C20 and C21 short side-chained triaromatic steroid hydrocarbons are degraded more readily than their C26–28 long side-chained counterparts. The C21–22-monoaromatic steroid hydrocarbons (MAS) appear to be more resistant to biodegradation than the C27–29-MAS.Interestingly, the most thermally stable PAH isomers are more susceptible to biodegradation than less thermally stable isomers, suggesting that selectivity during biodegradation is not solely controlled by thermodynamic stability and that susceptibility to biodegradation may be related to stereochemical structure. Many commonly used aromatic hydrocarbon maturity parameters are no longer valid after biodegradation to PM level 4 although some ratios change later than others. The distribution of PAHs coupled with knowledge of their biodegradation characteristics constitutes a useful probe for the study of biodegradation processes and can provide insight into the mechanisms of biodegradation of reservoired oil. 相似文献
13.
John K. Volkman Robert Alexander Robert Ian Kagi Rohinton A. Noble Carry Wayne Woodhouse 《Geochimica et cosmochimica acta》1983,47(12):2091-2105
A suite of crude oils and petroleum source rock extracts from the Barrow Sub-basin of Western Australia have been analysed for biological marker compounds by capillary GC-MS, and for volatile hydrocarbons by whole oil capillary GC. These analyses were used to calculate values for twenty-three biomarker parameters in order to assess aspects of source type, maturity, migration and biodegradation of the hydrocarbons.The crude oils had a source in the Upper Jurassic Dingo Claystone formation. These hydrocarbons accumulated in the reservoir sands and in some cases were biodegraded. Several accumulation and biodegradation episodes have been recognised while the basin continued to subside, which resulted in a suite of oils showing marked differences in composition. 相似文献
14.
Crude oil samples from two basins were analyzed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) to better understand the compositional heterogeneity of branched-cyclic hydrocarbons. GC×GC–TOFMS and conventional GC–MS results were compared. GC×GC–TOFMS revealed a wide range of compounds, including tricyclic, tetracyclic and pentacyclic terpane series, rearranged hopanes, methyl hopanes, secohopanes, onoceranes and steranes. Assignment of methyl hopane and 8,14-secohopane series other than onocerane isomers was only possible due to the high peak capacity and sensitivity of GC×GC. The oils comprised a mixture of two end members: non-biodegraded oil with abundant tricyclic terpanes and hopanes, and severely biodegraded oil with abundant 8,14-secohopane and demethylated tricyclic terpanes. A predominance of two distinct series, 3β-methylhopane and onocerane, was detected only in the lacustrine samples (classification based on biomarker parameters). In contrast, the predominance of a 2α-methylhopane series and lack of onocerane were found only for the marine oil sample. The results suggest that the distribution of 3β- and 2α-methylhopane series and the presence or absence of onocerane isomers reflect genetic differences in the source organic matter and that these compounds are new classes of biomarkers that can used as depositional paleoenvironment proxies. 相似文献
15.
China has a number of petroliferous lacustrine sedimentary basins of varying salinity and age (mainly Eocene). A geochemical investigation has been undertaken on several oils and source rocks from the Eocene lacustrine Biyang Basin. The distributions of n-alkanes, isoprenoids, steranes, and terpanes have been studied and used to characterize the sedimentary environment of deposition, maturity, biodegradation and undertake possible correlations. The ratios of C30-hopane/gammacerane, 4-methyl-steranes/regular steranes, steranes/hopanes, C21 tricyclic/C30 hopane are proposed to be indicative of the depositional environment whereas ß-carotane appears to be a source related indicator. The geochemical data obtained in this study suggest that the major source rocks in the Biyang Basin were deposited in a saline/hypersaline depositional environment. 相似文献
16.
G.T. Philippi 《Geochimica et cosmochimica acta》1981,45(9):1495-1513
A new method has been devised, based on high resolution GLC component analyses of the C6-C7 hydrocarbons from shales and from crude oils, whereby composition parameters in an oil are compared with the corresponding parameters in a shale. Ideally, a given composition parameter should have the same value for a crude oil and the source rock which generated and expelled that crude oil. A Similarity Coefficient has been devised, to measure the degree of correlation between crude oil and source rock hydrocarbons or between the hydrocarbons from different groups of crude oils. The maximum value of the Similarity Coefficient is 1.00, and the theoretical minimum is a positive fraction close to zero. Based on the natural variation in composition of primary (not biodegraded) crude oils of the same basin and origin, it was found that if the Similarity Coefficient is about 0.80 or higher, correlation between the natural hydrocarbons considered is good. If the Similarity Coefficient is less than 0.73, correlation is poor.Based on strict rules for sample selection (e.g. maturity of shales and lack of biodegradation in the oils), ten presumed crude oil-source formation pairs were selected. Most of these pairs have high Similarity Coefficients of 0.80 or more. Erroneous crude oil-source rock combinations from areas with more than one source formation, as in West Texas, have low Similarity Coefficients. This indicates that the crude oil-source formation correlation method based on the Similarity Coefficient generally is functioning properly. 相似文献
17.
R. Paul Philp Trevor D. Gilbert Jane Friedrich 《Geochimica et cosmochimica acta》1981,45(7):1173-1180
Bicyclanes previously reported only in heavily biodegraded Texas Gulf Coast crudes have been found to be ubiquitous in Australian crude oils of non-marine origin from four different basins. The compounds are present in oils, thought to be derived from the same or similar sources, that have undergone varying degrees of biodegradation. They are also found to be present in oils of different geological age. In addition a series of tricyclic diterpenoid hydrocarbons was common to four oils from the Gippsland Basin. Four of these compounds had the molecular formula C20H34 and mass spectral fragmentation patterns suggested they were mono-unsaturated diterpenoids. The presence of unsaturated diterpenoids in crude oils appears to be a unique observation. It is proposed that the diterpenoids may be the source of the bicyclanes also observed in these oils. 相似文献
18.
采用小太平山同一层位不同深度且连续的油砂样品,对油砂油的地球化学及生物降解特征进行分析。小太平山油砂油在生物降解作用下产生了丰富的25-降霍烷,常规藿烷和甾烷也发生了一系列变化。由于分子结构和稳定性不同,抗降解能力不同,C_(21)/C_(23)三环萜烷、伽马蜡烷/C_(30)藿烷、Ts/Tm、C_(30)重排藿烷/C_(30)藿烷值、αααC_(27)R/αααC_(29)R、C_(28)αααR/C_(29)αααR、C_(29)ααα20R/αββ20S、C_(29)ααα20R/αββ20R、C_(27)重排甾烷/(规则甾烷+重排甾烷)、常规藿烷异构体降解为25-降霍烷的比例,均反映出油砂油的生物降解程度随深度的增加而增大。小太平山油砂油随含水饱和度的增加降解程度增大,证实地层水有利于细菌类微生物的迁移、营养物质的传递,促进原油的生物降解及25-降霍烷的产生。 相似文献
19.
V.A. Kashirtsev I.I. Nesterov V.N. Melenevskii E.A. Fursenko M.O. Kazakov A.V. Lavrenov 《Russian Geology and Geophysics》2013,54(8):958-965
Chromato-mass-spectrometric studies made it possible to identify a wide spectrum of hydrocarbon biomarkers in crude oils from Cenomanian pools of northern West Siberia (Russkoe, Pangodinskoe, Van-Eganskoe, Severo-Komsomol’skoe). The distribution pattern of the main hydrocarbon components (n-alkanes, acyclic isoprenanes, steranes, terpanes) shows that most of the oils underwent intense microbial oxidation. We have established high concentrations of 25-norhopanes typical of high-degree degradation; demethylated hopanes are also revealed in “alkane” crude oils. Among low-molecular chemofossils, bi- and tricyclic mono and sesquiterpanes have been recognized, whose precursors are usually biomolecules synthesized by plants. Unsaturated precursors of mono and sesquiterpanes might have been the starting material for thermocatalytical synthesis of framework adamantanoid structures, whose high concentrations have been found in alkane-free crude oils. 相似文献
20.
Manoj Kumar Sarmah Srinivasan V. Raju 《Journal of the Geological Society of India》2016,87(3):327-336
The crude oils from Oligocene and Miocene formation of upper Assam basin have moderate API gravity and significant wax content. Crude oils from HJN and MKM fields of upper Assam basin are being produced from Oligocene and Miocene sands. These oils are somewhat biodegraded in nature as evidenced from their API gravity, density, bulk composition, GC fingerprints and relative concentrations of compounds in the gasoline range. It is observed from whole oil gas chromatographic data that the lighter hydrocarbons are more effected as a result of biodegradation and water washing than the heavier components. In the gasoline range compounds highest degradation of n-alkanes are observed followed by iso- and cyclo- alkanes. The extent of the effect of biodegradation of the gasoline range compounds in crude oil samples cannot be illustrated by the concentrations of the compounds. The concentrations only describe qualitative differences in molecular composition. This difficulty can be overcome by using parameters called degradative loss (%). This parameter shows exactly how much loss or gain has taken place in the gasoline range compounds. Within the gasoline range compounds, n-alkanes, Benzene baring HJN 15 and MKM 14 and Toluene experienced degradative loss indicating effects of both biodegradation and water washing in these oils. Cyclo-alkanes are least effected by biodegradation followed by iso-alkanes in all the oils. The extent of biodegradation and water washing is different for each oils from HJN and MKM fields as indicated by the degradative loss (%) of the compounds in the gasoline range. 相似文献