Identification of some diterpenoid hydrocarbons in petroleum

19-Norisopimarane and isopimarane have been synthesized from isopimara-9(11), 15-diene-3β, 19-diol. Analysis of the alkane fractions of an Australian crude oil by GC-MS showed the presence of nine diterpenoid hydrocarbons (diterpanes), of which one was bicyclic two were tricyclic and six were tetracyclic.19-Norisopimarane and isopimarane were identified by comparison of their mass spectra and GC retention times with those of the synthetic standards. ent-Beyerane, 16a(H)-phyllocladane, 16)β(H)-phyllocladane, ent-16α(H)-kaurane and labdane were also identified by comparison with authentic reference compounds. The remaining two compounds were tentatively identified as rimuane and as a 17-nortetracyclic diterpane on the basis of mass spectral evidence. The diterpanes are probably derived from conifer resins.     

Aliphatic and diterpenoid hydrocarbons and their individual carbon isotope compositions in coals from the Liaohe Basin, China

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.     

Molecular composition and chemosystematic aspects of Cretaceous amber from the Amazonas,Araripe and Recôncavo basins,Brazil

Amber occurrences in Brazil are rare. In this regard, the molecular composition of three such fossil resin samples from Brazilian Cretaceous sedimentary basins has been analyzed to determine the botanical origin of the resins. The samples were collected from the Amazonas (Alter do Chão Formation), Araripe (Santana Formation, Crato Member) and Recôncavo (Maracangalha Formation, Caruaçu Member) basins. The mono-, sesqui- and diterpenoids in the extracts were used as chemosystematic markers when compared with terpenoids in extant conifers. The compounds were mainly diterpenoids and their degradation products from the labdane, podocarpane, pimarane and isopimarane classes, in addition to paraffins, methoxyphenols and carboxylic acids. Tetracyclic diterpenoids such as phyllocladane, kaurenol and kauranol were also present. The biomarker compositions are certainly typical for conifers and, given the absence of triterpenoids and diterpenoids such as ozic acid, angiosperms can be excluded as a botanical source. The absence of phenolic diterpenoids (ferruginol, totarol) and their derivatives excludes podocarpaceous affinities for the ambers from the Amazonas and Araripe basins. The fossil records of the embedding sediments (e.g. Araucariaceae pollen and leaves) support the proposal of an Araucariacae origin for these ambers, but Cupressaceae and Cheirolepidiaceae cannot be excluded. On the other hand, the presence of phyllocladane and kaurane derivatives is evidence for Araucariaceae or Podocarpaceae origins for the amber from the Recôncavo basin, but Cupressaceae cannot be excluded.     

Structure and origin of terpenoid hydrocarbons in some German coals

Hydrocarbon extracts of coal samples from major coal fields in West Germany have been investigated by gas chromatography-mass spectrometry (GC/MS). The samples are of Carboniferous and Tertiary age and derive from limnic and paralic environments, the Saar District, the Ruhr Area and the Lower Rhine Basin.Differences in facies, maturity and age reflected in the distribution patterns of the extracted alkylcyclohexanes. An unexpected occurrence of cyclic diterpenoid hydrocarbons in some samples of Carboniferous age has been found. The tetracyclic compounds mainly show phyllocladane type structures and can serve as source indicators.Hydrocarbons obtained from chemical degradation of the macromolecular material of the samples also revealed phyllocladane-type compounds which are normally associated to resins of modern and extinct familes of conifers. Origin and structural variations of this class of hydrocarbons are discussed in terms of maturity and palaeobotanical implications.     

华北地区石炭、二叠系腐殖煤中的四环二萜烷

从华北西部和南部五个煤矿取得的石炭、二叠系腐殖煤的饱和烃馏分中,经GC和GC/MS分析，检测出了较丰富的二萜类生物标志物。根据质谱特征与卡瓦保留值，并对照文献谱图，确认其中包括五个具有贝壳松烷骨架的四环二萜烷(即ent-白叶烷、16α(H)-和16β(H)-扁枝烷、16α(H)-和16β(H)-贝壳松烷)，以及一个三环的异海松烷。一个完整的四环二萜烷系列在我国华北石炭、二叠系腐殖煤中的发现在北半球很可能属首次。这些二萜类内组成在时间和空间上的差异分布，可能反映古植物群演化与分布的变化。扁枝烷和贝壳松烷的立体化学构型，可提供重要的有机成熟度信息。     

辽河盆地煤系地层中特高含量的二萜类及其地质意义

从辽河盆地东部凹陷下第三系沙三段煤系烃源岩中检出了特高含量的海松烷,脱氢松香烷等三环二萜烷和扁枝烷等四环二萜烷类化合物,此外还检测到了奥利烯、乌散烯等罕见的三萜类。上述三类化合物尽管出现在同一套地层中,但它们的主要来源并不完全相同,其中三环二萜和四环二萜类分别以裸子植物和蕨类植物为主要来源,而五环三萜类则主要来源于被子植物。说明辽河盆地下第三系沙三段煤系地层中母质输入的多样性和复杂性。     

四环聚异戊二烯类化合物:中国东部断陷湖盆新分子化石

渤海湾盆地海域断陷湖盆歧口凹陷古近系烃源岩及原油样品中,检测出丰富的四环聚异戊二烯类化合物。四环聚异戊二烯类化合物（C₃₀TPP）具有两个异构体,能有效地区分渤海湾盆地海域歧口凹陷沙三段（Es₃）烃源岩和沙一段（Es₁）烃源岩形成的混源原油,是湖相原油的油源对比研究中的新分子化石。四环聚异戊二烯类化合物与水体盐度之间有密切关系,沉积环境水体盐度越高,其丰度越高。随热演化程度增大,原油的四环聚异戊二烯类化合物（TPP）丰度逐渐降低。四环聚异戊二烯类化合物（TPP）具有湖相有机质输入的很强专属性,可用于判识湖相原油研究,在研究湖相沉积环境有机质的油源对比、沉积环境及热演化规律中具有重要地质-地球化学意义。     

Geochemical Evidence for Coal and Carbonaceous Mudstone as the Possible Major Oil Source Rock in the Jurassic Turpan Basin,Northwest China

Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analysis of the 20 crude oils and 40 source rocks from the Turpan Basin, some data have been obtained as follows: carbon preference index and methylphenanthrene index of the Jurassic oils are 1.16–1.45 and 0.28–0.80, and the ααα C29 sterane 20S/(20S+20R) and C29 sterane ββ/(ββ+αα) are 0.44–0.51 and 0.4–0.54 respectively, which show the normal maturity of oils; the vitrinite reflectance of the source rocks from the Xishanyao to Badaowan Formations range from 0.47% to 0.97%, which indicate immature to mature thermal evolutionary stage and sufficient conditions for generating mass mature oil. The effect of hydrocarbon expulsion should be considered when studying the source of coal-derived oil by using Biomarkers. Biomarkers in the Jurassic oils from the basin are similar to those in the coals and carbonaceous mudstones, with a strong predominant content of pristane, relatively high ratio of C15/C16 sesquiterpenoids (>1), a relatively high content of low carbon number tricyclic terpanes and C24 tetracyclic terpane, little gammacerane and C29 Ts detected, an absolute predominant content of C29 sterane and a relatively high content of diasterane. However, the opposite characteristics are shown in mudstones, with an approximately equal content of pristane and phytane, relatively low ratio of C15/C16 sesquiterpenoids (<1), a relatively high content of high carbon number tricyclic terpanes and a low content of C24 tetracyclic terpane, peaks of gammacerane and C29 Ts detected obviously and an increasing C27 sterane content. All of these characteristics identify the coals and carbonaceous mudstones as the possible major oil source rocks in this area, and they were formed in the stronger oxidizing environment with shallower water than mudstones.     

Effect of water washing on hydrocarbon compositions of petroleum sandstone reservoir rocks in Tarim Basin, NW China

Gross compositions and distribution of saturated and aromatic hydrocarbons in Carboniferous sandstone reservoire rocks in oil and water zones for Tzhong-10 well of the Zhongyang Uplift in the Tarim Basin were studied in dteail by means of Rock-Eval Pyrolysis,thin-chromatograph-flame ionization detection(TLC-FID),gas chromatography,gas chromatography-mass spectrometry.The results suggest that the gross composition of reservoir hydrocarbons between the oil zone and the water zone show significant differences,Water wahing has a dramatic effect on saturated hydrocarbon blomarkers,especially drimane series compounds,Drimane series compounds in the water zone have been depleted completely.However,the contents of tricyclic iterpanes and pentacyclic triterpanes tend to decrease slightly,but the water-zone reservoir hydrocarbons contian a large amount of gammacerane.This suggests that gammacerane be more resistant to water washing than diterpanes and homohopanes.The contents of pregnane,homopregrane,diasteranes relastively decrease as a result of water washing.Water washing has a noticeable effect on polycyclic aromatic hydrocarbon compounds,especially aromatic sulfur compounds,and the contents of dibenzothiophene series compounds and benzonaplyiothipophene decrease significantly as a result of water washing.However,the conterts of bicyclic and tricyclic aromatic hydrocarbons decrase slightly and those of tetracyclic and pentacyclic aromatic hydrocarbons,especially benzofluoranthene and benzopyrenes,increase markedly owing to adecrease in light aromatie hydrocarbons as a result of water washing.     

高分子量烃油气化探方法的模拟实验研究——以黄海沉积物为例

传统上认为大分子烃类很难通过微渗漏方式逸散到地表,但已有研究表明高分子量烃类也可以逸散到现代沉积物中。本文基于黄海现代沉积物与典型原油地球化学特征的不同,将二者进行正交配比,系统研究不同配比产物的组成特征。结果表明:随着配比实验中原油比例的增大,正构烷烃和部分芳烃的色谱指纹呈现规律性变化,其正构烷烃奇偶优势逐渐消失,烷基芳烃丰度随之增加;三环萜烷、藿烷、规则甾烷等化合物的绝对浓度,以及二苯并噻吩/菲等的比值也呈现规律性变化,其中三环帖烷、C_(24)四环萜烷/C_(26)三环萜烷和三环萜烷/藿烷三者的变化明显且平稳,其数值范围均在0~3.0,适合用于渗逸图版。将研究区采集的未知样品与配比产物的组成特征进行对比,在排除外源污染的情况下可定性判识该研究区是否存在地下油气藏;将样品的相关参数投到图版上,有望进一步定量判识样品中渗入原油的比例。该方法可以作为常规油气化探的补充,在油气藏评价方面提供诸多信息,甚至在环境污染监控等领域有望获得推广。     

Phyllocladane in brown coal from Handlová, Slovakia: Isolation and structural characterization

Aliphatic diterpenes were isolated from brown coal from Handlová, Slovakia, using microwave assisted extraction of mechanically activated coal powder. The parameters of the extraction procedure were optimized to get the target compounds in high yield. The total extract was separated using adsorption chromatography. GC–MS revealed tetracyclic and tricyclic diterpanes in the aliphatic fraction; they were identified as 16α(H)-phyllocladane (83%), isopimarane (11%), 18-norisopimarane (4%), abietane (2%) and fichtelite (<0.1%). It was found that more than 2 g of the most abundant diterpane, 16α(H)-phyllocladane could be extracted from 1 kg of Handlová coal. Because of the scarcity of relevant analytical data, 16α(H)-phyllocladane was thoroughly characterized by spectroscopic and chromatographic methods. A complete set of ¹H and ¹³C NMR data is given including their comparison with published values and ab initio calculations. EI mass and IR spectra of 16α(H)-phyllocladane are shown and discussed. Kováts retention indices measured on two common GC stationary phases are also given.     

Diversities in biomarker compositions of Carboniferous–Permian humic coals in the Ordos Basin,China

The molecular composition of Carboniferous–Permian coals in the maturity range from 0.66 to 1.63% vitrinite reflectance has been analysed using organic geochemistry to investigate the factors influencing the biomarker compositions of humic coals. The Carboniferous–Permian coal has a variable organofacies and is mainly humic-prone. There is a significant difference in the distribution of saturated and aromatic hydrocarbons in these coals, which can be divided into three types. The Group A coals have biomarker compositions typical of humic coal, characterised by high Pr/Ph ratios, a lower abundance of tricyclic terpanes with a decreasing distribution from C₁₉ tricyclic terpane to C₂₄ tricyclic terpane and a high number of terrigenous-related biomarkers, such as C₂₄ tetracyclic terpane and C₂₉ steranes. The biomarker composition of Group B coals, which were deposited in a suboxic environment, have a higher abundance of rearranged hopanes than observed in Group A coals. In contrast, in Group C coals, the Pr/Ph ratio is less than 1.0, and the sterane and terpane distributions are very different from those in groups A and B. Group C coals generally have abnormally abundant tricyclic terpanes with a normal distribution maximising at the C₂₃ peak; C₂₇ steranes predominates in the m/z 217 mass fragmentograms. The relationships between biomarker compositions, thermal maturity, Pr/Ph ratios and depositional environments, indicate that the biomarker compositions of Carboniferous–Permian coals in Ordos Basin are mainly related to their depositional environment. This leads to the conclusion that the biomarker compositions of groups A and B coals collected from Shanxi and Taiyuan formations in the northern Ordos Basin are mainly related to their marine–terrigenous transitional environment, whereas the biomarker compositions for the Group C coals from Carboniferous strata and Shanxi Formation in the eastern Ordos Basin are associated with marine incursions.     

Hydrocarbons in western North Atlantic surface sediments

High concentrations of hydrocarbons (500–3000 μg/g dry weight) together with a complex and wide molecular weight range of composition, and low ¹⁴C activity of δ¹⁴C = ?833 ± 50%. strongly indicate that fossil fuel hydrocarbons make up the bulk of hydrocarbons in and near the New York Bight dump site areas. The composition and concentrations of hydrocarbons in Hudson Channel sediments suggest some transport of dump site hydrocarbons to areas in the channel midway to the edge of the continental shelf. Sediments at 16 stations in other areas of the continental shelf, continental slope and abyssal plain have hydrocarbon concentrations and compositions indicating that no more than 1 μg/g dry weight of fossil fuel hydrocarbons are present.N-alkanes from land sources were among the most predominant hydrocarbons in all samples except those in the New York Bight region. Their presence in abyssal plain surface sediments documents transport of some land derived organic matter to these deep ocean areas. Two 25-carbon cycloalkenes are among the more predominant hydrocarbons in continental shelf surface sediments except for the dump site areas. These two compounds are present in lower concentrations in slope sediments and are not detected in abyssal plain sediments.     

Reconstruction of floral changes during deposition of the Miocene Embalut coal from Kutai Basin,Mahakam Delta,East Kalimantan,Indonesia by use of aromatic hydrocarbon composition and stable carbon isotope ratios of organic matter

The distribution of aromatic hydrocarbons and stable carbon isotope ratios of organic matter in a series of nine Miocene Embalut coal samples obtained from nine coal seams of Kutai Basin, East Kalimantan, Indonesia were studied. The rank of the Embalut coals ranged from lignites to low rank sub-bituminous coals (0.36–0.50% Rr), based on measurements of huminite reflectance. The aromatic hydrocarbon fractions of all coal samples were dominated by cadalene in the lower boiling point range and picene derivatives in the higher boiling point range of the gas chromatograms. Cadalene can be attributed to the contribution of Dipterocarpaceae and various hydrated picenes to the contribution of additional angiosperms to the coal forming vegetation. The picenes originate from alpha- and beta-amyrin. However, in some coal samples minor amounts of simonellite and retene were also detected which argues for an additional contribution of gymnosperms (conifers) to coal forming vegetation preferentially in the Middle Miocene and at the beginning of the Late Miocene. The results of stable carbon isotope ratios (δ¹³C) in most of the coal samples are consistent with their origin from angiosperms (δ¹³C between ?27.0‰ and ?28.0‰). During the Miocene the climate of Mahakam Delta was not uniformly moist and cooler than the present day climate. This would have been favourable for the growth of conifers, especially in the montane forests. The contribution of conifers to the Embalut coals might be a result of the cool Middle/Late Miocene climate during peat accumulation in the Kutai Basin.     

Occurrences and distributions of branched alkylbenzenes in the Dongsheng sedimentary uranium ore deposits,China

A series of branched alkylbenzene ranging from C₁₅ to C₁₉ with several isomers (2–5) at each carbon number were identified in sediments from the Dongsheng sedimentary uranium ore deposits, Ordos Basin, China. The distribution patterns of the branched alkylbenzenes show significant differences in the sample extracts. The branched alkylbenzenes from organic-rich argillites and coals range from C₁₅ to C₁₉ homologues, in which the C₁₇ or C₁₈ dominated. On the other hand, the C₁₉ branched alkylbenzenes dominated in the sandstone/siltstone extracts. The obvious differences of the branched alkylbenzene distributions between the uranium-host sandstones/siltstones and the interbedded barren organic-rich mudstones/coals probably indicate their potential use as biological markers associated with particular depositional environments and/or maturity diagenetic processes. Possible origins for these branched alkylbenzenes include interaction of simple aromatic compounds with, or cyclization and aromatization reactions of, these linear lipid precursors such as fatty acids, methyl alkanoates, wax esters or alkanes/alkenes that occur naturally in carbonaceous sediments. The possible simple aromatic compounds may include substituted benzenes, functionalized compounds such as phenols that are bound to kerogen at the benzyl position, and phenols that are decomposition products derived from aquatic and terrestrial sources. The distributions of methyl alkanoates and n-alkanes were found to be different between organic-rich mudstone/coal and sandstone/siltstone. From this result, it can be concluded that such differences of the alkylbenzene distributions were mainly resulting from the differences of organic precursors, although maturity effect and radiolytic alteration cannot be completely excluded.     

Molecular compositions of weathered petroleum and comparison with its possible source

Two surface outcrop samples and three drill core samples of oil-impregnated sandstone from the P.R. Spring Seep, Uinta Basin, Utah were analyzed. These oils exhibit in common the entire homologous series of tricyclic diterpane hydrocarbons, which have been previously described only in extracts from the Mahogany Ledge Member of the Green River Formation. Hopane and a series of degraded hopanes are also present in the oil samples, while steranes are conspicuously absent. Aliphatic alkanes are present only in the deepest core sample.The cycloalkanes are apparently not readily utilized by the petroleum oxidizing microbes, and therefore survive the weathering process. Tricyclic and tetracyclic alkylated diterpanes are unchanged, whereas the series from norhopane through tetrakisnorhopane may be interpreted as progressive bacterial degradation of the hopane molecule.The occurrence and distribution of tricyclic diterpanes, of tetracyclic diterpanes and pentacyclic triterpanes is similar to the stratigraphically nearby Mahogany Ledge Member, suggesting that the oil shales were the source rocks for the oil now exposed as the P.R. Spring Seep. The absence of steranes, which are abundant in the oil shales, is puzzling.     

Distribution Patterns of Pentacyclic TriterpenoidHydrocarbons in Low-Mature Source Rocksfrom Eastern China

Four typical distribution patterns of pentacyclic triterpenoid hydrocarbons (types A-D) are distinguished in the low-mature source rocks from eastern China. Type A has a relatively high content of pentacyclic triterpenes. It exists in immature sediments and the distribution and abundance of triterpenes vary with the maturity of the sediments. An unknown C30 triterpene (UCT2) has also been detected in very shallow sediments. This compound is very unstable and disappears rapidly with the increase of depth. Type B is characterized by a relatively high amount of 17α(H), 21β(H)-30-homohopane. This kind of distribution pattern is common in coals and terrestrial sediments of low maturity. Type C has a relatively high content of diahopane and neohopane series. The analysis shows that this distribution pattern may have an indirect relationship with the input of higher plants despite its microbial source. There are C30-unconfirmed triterpane (UCT2) and a relatively high content of C35 hopane in type D. The dist     

Organic geochemistry and petrography of Tertiary coals and carbonaceous shales from Argentina

A series of eight Tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0.50 and 0.58% were extracted, fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by GC and GC-MS. Additionally, a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation.The saturated hydrocarbon fractions displayed the typical n-alkane distribution for coals of this rank, with CPI values between 2.0 and 3.1. Among the branched/cyclic compounds, pristane and α, β-homohopane were recognised as relevant components pointing to an oxic depositional environment. Detection of benzohopanes (C₃₂–C₃₅) in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass. Taking into consideration the Pr/Ph ratios, ash contents and microscopical characteristics of the samples, aspects of the possible degradation of hopanetetrol to homohopane are discussed. Resin-derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and, although minor compounds, they are interpreted to be a sign of the contribution of Podocarpaceae and Araucareaceae to the coal swamp.Aromatic compounds were dominated by alkylnaphthalene derivatives, presumably formed by C-ring cleavage and aromatisation of higher plant-derived pentacyclic triterpenois, which were main components in the high-boiling range of the fractions investigated. Angiosperms (especially Fagaceae) are postulated as source for these polycyclic compounds and, hence, for some of the polyalkylated aromatic bicyclics detected.     

Origin and distribution of biomarkers in the sulphur rich Utrillas coal basin – Teruel mining district – Spain

The Utrillas coal facies are located in the Maestrazgo basin in NE Spain. This mining district of Teruel contains sub-bituminous deposits from the Middle Albian (Lower Cretaceous 105 Ma) in areas near a delta estuary with abundant sulphur. The high sulphur content is due to an influx of sulphate caused by the geological recycling of Triassic gypsum from the catchment area into the delta estuary. In some outcrops, the weathered coal reveals leonardite deposits. The depositional environment of the basin originated coals, some of which are currently mined. The organic matter of the coals has been the object of scattered reports. Studies have focused on bulk pyrolysis parameters and microscopic observation in Utrillas samples, as well as the inorganic and insoluble organic fraction.We analysed the organic soluble extract of the Utrillas coals using GC–MS in order to characterize their aliphatic, aromatic and organosulphur compounds. The biomarker distribution allowed us to recognize different inputs, assess their depositional palaeoenvironment and finally determine their degree of maturity. In particular, homologous series of hopanes related to eubacteria were present. Biomarkers characteristic of higher plant inputs were also widely distributed (e.g. phyllocladane or C₂₉ steranes). The presence of linear alkylbenzenes allowed us to recognize the palaeodepositional reducing environments where they were deposited. Specifically, thienylhopanes were associated with sulphur-reducing environments. Finally, the abundance of unsaturated biomarkers such as diacholestenes indicated low-maturity coals. Various aromatic ratios such as the methylphenanthrene index also suggested diagenesis in the initial stage.     

现代沼泽沉积物中三、四环萜类的分布及演化特征

对甘南和滇池现代沼泽沉积物中三、四环萜类的研究表明:在现代沼泽沉积物中,具类海松烷骨架的化合物以海松烷型化合物数量最多,而松香烷型化全物数量较少;长链三环萜烷中存在C₂₁C₂₃和C₂₄化合物以C₂₃为顶点的倒“V”字型分布,正常四环萜烷呈以高碳数为主峰的“阶梯型”分布,有意义的的是样品中均含脱-A-羽扇烷和壳松烷四环萜烷。在早期成岩过程,海松烷型二萜类主要是形成烯烃和烷烃,而松香烷型二萜类主要是芳构化作用。