Fan Pu

Geochemical characteristics of aromatic hydrocarbons of crude oils and source rocks from different sedimentary environments

The aromatic hydrocarbons from a significant number of oils and source rocks of different source materials and depositional environments have been analysed by GC and GC-MS. Variations in the distributions of the naphthalenes, phenanthrenes, fluorenes, dibenzofurans, dibenzothiophenes, naphthobenzothiophenes and triaromatic steroid hydrocarbons can be used to differentiate samples on the basis of whether they are derived from marine or terrestrial source materials. Furthermore the nature of the depositional environments in terms of salinity or carbonate vs shale can be distinguished on the basis of variations in the distributions of these compounds and the relative proportions of individual components within the total aromatic hydrocarbon fraction.

Novel biomarkers found in South Florida Basin

Abstract Several novel series of aryl isoprenoids, have been observed in the Sunniland Limestone of South Florida Basin (U.S.A.). All of these compounds have the same series of homologous key ions, m/z 91 + 14n (n = 0–10). The compositions and distributions of trimethylalkylbenzenes (1-alkyl-2,3,6-trimethylbenzenes) are reported and discussed in this paper. Their application to various organic geochemical problems are also discussed, particularly their use as indicators of organic facies and maturity of sedimentary organic matter.

Thermal history of the periphery of the Junggar Basin, Northwestern China

Geochemical analyses of rock core samples show that the basin periphery has experienced low thermal stress; present-day heat flows are in the range of 25-35 mW/m 2 and have not been significantly higher than the worldwide mean of approx. 63 mW/m 2 since the mid-Permian. Present day heat flows were determined from corrected borehole temperatures and rock thermal conductivities. Paleo-heat flows were determined by first-order reaction kinetic modeling of several geochemical paleothermometers (vitrinite reflectance, clay mineral diagenesis and relative proportions of sterane and hopane biological marker diastereomers)

CHARACTERISTICS OF BIOMARKERS IN THE RECENT SEDIMENT FROM QINGHAI LAKE, NORTHWEST CHINA

The occurrence of biomarker hydrocarbons in the Recent sediment of Qinghai Lake was investigated. It was found that the distribution of these biomarkers in Qinghai Lake, a semi-saline water lake, is unusual. The distribution of n-alkanes is predominated by high carbon-numbered alkanes with a high OEP (CPI) value. Two series of bicyclic sesquiterpanes derived from micro-organisms, e.g. algae or bacteria, were detected. The occurrence of tricyclic and tetracyclic terpenoids is characterized by the input of the organic matter from aquatic organisms. The conversion from hopenes existing in bacteria and blue-green algae into hopanes is put forward in this paper. C27C29 regular steranes, 4-methylsteroids, diasteranes, pregnanes, norsteroids and secosteranes were found in abundance in the sedimentary samples. Another important contribution of this paper is towards the geochemistry of amino acids in the Recent sediment of Qinghai Lake. The composition, distribution and evolution of the amino acids in the lacustrine sediments will be discussed in detail. It was found that several ratios of different amino acids have a clear diagenesis trend in the two cores studied. The racemization reaction of amino acids and their application in the geochemistry will also be discussed. The racemization of alanine and leucine were employed in this study to calculate the age of the sediment samples, with satisfactory result.

Biomarker characteristics of nonmarine oils in China

Abstract The present paper deals with the origin of non-marine oils in China. Since the formation of their source rocks, is greatly affected by paleoclimate and sedimentary environments, crude oils originated from such source rocks display different molecular characteristics. This paper attempts to identify these continental environments by using various geochemical parameters (OEP, Pr/Ph and biomarkers). In fact the distribution of hopanes with different carbon numbers is influenced by the characteristics of the original organic matter and by diagenetic transformations of sedimentary environments. As for biological markers, tricyclic terpanes, progesteranes and 4 methyl steranes are particularly abundant in saline depositional environments. On the other hand, onoceranes, 8,14-secohopanes, spirotriterpanes, tarxeranes, γ-lupanes and oleananes are specifically found in crude oils derived from swamp or very shallow lagoon facies. By studying recent sediments of different depositional environments it is therefore possible to establish effective models for reconstructing paleoenvironments.

Biomarkers of Upper Sinian cyanobacterial dolostones in southwest China

Abstract In the present paper, eight core samples of cyanobacterial dolostone from the Dengying Formation (Sinian) of the Weiyuan Gas Field, Sichuan, southwest China, have been studied organically and geochemically. It has been shown that the following biomarker compound exist. C12C37n-alkanes, which have an even-carbon-numbered predominance of n-alkanes with a major constituent of n-C16 or C18, and a less-than-one value of Pr/Ph; C29 tricyclic diterpanes; C27C30 hopanes and gammacerene in high abundance; steranes with C29 as the predominating component; C12C30 alkyl cyclohexanes; naphthalenes; phenanthrenes; diphenyls; pyrene; triaromatic steranes and alkylbenzenes with a long branched alkyl chain; in aromatic fraction, of which naphthalenes and phenanthrenes are the major compounds. It is strongly suggested that these biomarkers were derived from micropalaeoplants and algae, and that they are important environmental indicators.

Petroleum geochemistry of the Talimu Basin

Abstract The Talimu Basin in China consists of a Paleozoic platform and a Meso-Cenozoic land block series. On the basis of sedimentological and tectonic studies of the Talimu Basin, it is proposed in this paper that two different kinds of oil-generating sub-basins and source beds are present, and responsible for the formation and accumulation of both marine and nonmarine hydrocarbons. A preliminary evaluation for different source beds within the basin has been carried out using the disciplines of sedimentology, lithofacies-paleogeography and organic geochemistry. We distinguish various depositional settings, with different oxidation and/or reduction features, by showing systematic differences in relative molecular distributions. These include characteristic facies-related biomarkers, such as tricyclic terpanes, pregpanes, fluorenes, dibenzofurans and dibenzothiophenes. Types of organic matter in source rocks are revealed by the presence/absence of land plant-derived biomarkers, including pimarane, abietane, dehydroabietane, fluoranthenes, chrysenes and perylenes. Kerogens, from black mudstones of the Saergan Formation and the Yingan Formation at the northwestern margin of the basin, have been selected for detailed examination of their hydrocarbon potential. Favorable regions for hydrocarbon prospecting in the basin are also discussed.

Biomarkers and Other Hydrocarbons in Upper Sinian Stromatolitic Dolostones from Southwest China

Upper Sinian stromatolitic dolostones from southwest China have been analyzed for biomarkers in their aliphatic and aromatic hydrocarbon fractions. The biomarkers identified are mainly as follows: bicyclic sesquiterpanes, tricyclic terpanes, pentacyclic triterpanes, 8,14-secohopanes, hopane sulfides, alkylcyclohexanes, steranes, triaromatic steroids, aromatized hopanes, and long-chain alkylbenzenes. Other aromatic hydrocarbons which may be used as maturity indicators were also identified, including naphthalenes, phenanthrenes and biphenyls. The relationships between the aforementioned compounds and their microbial precursors, depositional environment and thermal maturity are discussed.