Fu Jiamo

Peculiarities of salt lake sediments as potential source rocks in China

Abstract Hypersaline lake sediments are widely distributed in China and can be good sources for petroleum. The Palaeogene sediments of the Jianghan Basin in Eastern China are a typical example composed of salt lake evaporite-clastic facies in fault-subsided basins. Their organic matter is variable, but is dominated by Type II kerogen. The biological marker characteristics of core extracts and oils from the Jianghan Basin include: (i) low OEP values for n -alkanes and, occasionally, an even-odd predominance, (ii) a high concentration of phytane, (iii) a relatively high gammacerane/17α(H),21β(H)-hopane ratio and (iv) abundant, mainly nickel, porphyrins. Sample Guang-33 (K-33) is typical of the immature oils found in the Jianghan Basin. Geological and geochemical data both indicate that it was generated from source rocks in the maturity range R 0 0.45–0.55%. Its characteristics are similar to those of immature source rocks, with high concentrations of phytane, steranes, triterpanes and nickel porphyrins, and, for an oil, extremely low values for molecular parameters of maturity, such as C 29 20S/(20S + 20R) 14α(H),17α(H)-steranes, C 32 22S/(22S + 22R) 17α(H),21β(H)-hopanes and DPEP/(DPEP + Etio) porphyrins.

Organic geochemical characteristics of major types of terrestrial petroleum source rocks in China

Summary Terrestrial source rocks, deposited under non-marine conditions in continental environments, have been divided into five major groups: Group A, sedimentary formations of big lake basins in the interior of the Chinese plate; Group B, lacustrine clastic formations in fault-bounded basins; Group C, salt lake evaporite-clastic formations in fault-bounded basins; Group D, lagoonal-lacustrine volcano-clastic formations of intermontane basins; and Group E, paralic coal-bearing formations of platform areas. The abundance, type and evolutionary characteristics of the organic matter, as well as the biomarker characteristics of various groups of source rocks are discussed briefly. There are several problems relating to evaluation of hydrocarbon prospects in terrestrial sedimentary basins, including the origin of Type I kerogens and their hydrocarbon potentials, immature oils, and coal-bearing formations as potential source rocks.

Distribution of polycyclic aromatic hydrocarbons in aerosols and dustfall in Macao.

Polycyclic aromatic hydrocarbons (PAHs), widespread environmental pollutants, have been measured in aerosols and dustfall in Macao. In this paper, we compare concentration distributions and determine the partitioning of PAHs in aerosols and dustfall for different areas, sampling times and sampling heights. The results demonstrate that the concentrations of ΣPAHs in aerosols and dustfall vary at the different sites and heights. The concentrations of ΣPAHs and most of the individual PAHs in aerosols at night were higher than those in the daytime when using the unit of μg/g and lower than those when using the unit of μg m-3. It is shown that the distribution of individual PAHs in aerosols differs significantly from that in dustfall.

Sulphur-containing compounds in sulphur-rich crude oils from hypersaline lake sediments and their geochemical implications

Three sulphur-rich commercial crude oils have been studied, which contain sulphur as high as up to 4–12%. These samples were collected from Tertiary hypersaline lake sediments of the Jianghan Basin, Hubei Province at different depths, but above the oil generation threshold (2200m). FPD-GC and GC-MS data show that aromatic fractions of the crude oils are composed of different homologues of sulphur-containing compounds, including long-chain normal alkyl-thiophenes and-thiolanes, long-chain isoprenoid-thiophenes and -thiolanes, and benzothiophenes. It is worth noting that the distribution patterns of long-chain alkyl-thiophenes and -thiolanes from two shallow-seated crude oils are quite similar to those of normal alkanes showing marked even-odd predominance. It seems that the even-odd predominance of sulphur-containing compounds decreases with increasing burial depth of the crude oils. The major component of aliphatic fraction is phytane, and similarly the major peaks of aromatic fractions also represent C20 isoprenoid thiophenes.Some preliminary conclusions have been drawn from the above discussion: (1) Abundant sulphur-containing compounds may be used as an indicator of low mature or immature crude oils produced from hypersaline lake sediments; (2) Sulphur-containing compounds are considered to be early diagenetic products of reactions between elemental sulphur or sulfides and alkanes or their precursors (phytols, fatty acids, alcohols, etc.), or of bacterial activities, but not direct inputs of organisms.

A geochemical investigation of crude oils from Eastern Pearl River Mouth Basin, South China Sea

Abstract A thorough petroleum exploration of the Pearl River Mouth Basin (PRMB), South China Sea, began in 1983. At present, several oilfields have been found in the PRMB, mainly distributed in Dongsha Massif, Huizhou and Xijiang Depressions as well as Huilu Lowhigh, and one of them has been developed recently. The crude oils found in the basin can be classified into two types. One is normal waxy type, and the other is cyclic type, which may be caused by minor biodegration and is restricted to the Liuhua District of Dongsha Massif. However, on the basis of geochemical characteristics, all the crude oils are thermally mature, indicating that they are derived from source rocks which have entered the main oil generation period but their maturity is not high enough to reach the overmature stage. Moreover, in the biomarker distribution, the oils also share many similarities. Almost all the oils contain abundant C 30 4-methylsteranes with 24-ethyl side chain, ubiquitous oleanane and lower concentration of gammacerane, and possess high ratios of Ni/V, pristane to phytane and C 30 hopane over total C 29 steranes as well as high paraffin wax and low sulphur content, indicating that they originated from terrestrial organic matter deposited in lacustrine and marsh coal-forming environments. However, some characteristics resemble Brazilian offshore oils of salinewater lacustrine environment. The oils found in the PRMB can also be classified into three main genetic types based on the relative values of pristane over phytane ratio, C 29 sterane preference and the composition of the carbon isotope. Type I oils occurred in the Huizhou and the Xijiang Depressions and their adjacent Dongsha Massif. It has higher ratios of pristane to phytane (1.80–5.54 and 3.21 on the average scale) and heavier carbon isotopic composition, indicating that their source rocks contain much more abundant terrestrial higher plant input. Type II, encountered in Huilu Lowhigh and its bounding area of Dongsha Massif, has moderate ratios of pristane to phytane (1.78–2.94 and 2.39) and C 29 sterane similar to Type I. Type III is distributed in the Liuhua District of Dongsha Massif and has lower pristane to phytane ratios (ranging from 1.49 to 1.97), smaller C 29 sterane preference, higher C 30 4-methylsterane content and lighter carbon isotopic composition (less than −29%) even though they have undergone minor biodegration, implying that the source rocks of the oils are enriched with lacustrine organism input.

Determination of trace elements in crude oils and organic materials extracted from oil-forming source rocks in China by INAA

A combination of Soxhlet extraction, column chromatography and INAA with GC and GC-MS was used in this work for the study of the abundance patterns of 36 trace elements and their correlation in nearly 100 samples of crude oil and organic materials extracted from oil-forming source rocks from 10 main Chinese oilfields. The low V/Ni ratios of 0.01 to 0.3 state the oil-forming continent environment. The geochemical significance hinted from other trace element abundances is also briefly discussed.

Biomarker Compounds as Indicators of Paleoenvironments

In an attempt to assess the paleoenvironments of terrestrial sediments, some twenty-two representative Chinese non-marine sediment samples were studied using the molecular organic geochemistry method. The sediment samples studied include oilshale, shale, mudstone and glauber salt from Tertiary to Cretaceous in age. Judging from geological /geochemical data and paleosalinity data, the samples studied are of lacustrine sedimentary origin and can be divided into three different types: fresh water, brackish and saline /hypersaline lake sediments. The aliphatic fractions were separated from the extracts of the samples and analysed by means of GC and GC /MS instruments, giving a number of parameters such as relative abundances of alkanes and cycloalkanes as shown in the mass chromatograms.

Organic inclusions and their relations to oil and gas occurrences

Abstract 154 core and outcrop samples of Proterozoic and Palaeozoic reservoir and non-reservoir strata were collected from Renqui, Subei, Guangxi, Sichuan, etc. Organic inclusions contained in the samples were studied by means of polarized light microscope, fluorescence microscope, micro-cooling-heating stage and compositional analysis. According to HC phase, colour, refractive index and fluorescent properties, organic inclusions can be classified as two braod types: HC inclusions and HC-containing inclusions, which can be further subdivided into eight subtypes. Also discussed in this paper are the types and peculiarities of organic inclusions, as well as the composition of gases, parameters for organic molecules and paleotemperature, which are considered to be useful indicators for oil and gas migration, evolution and prospective evaluation. Some typical examples are also given in this study.

Preliminary Study of Extractable Organic Matter in Aerosols from Beijing and Guiyang, China

Abstract The solvent-extractable compounds (lipids) of four samples, which were collected from a western suburb of Beijing and in the city of Guiyang, P.R. China, respectively, using a standard high volume air sampler, were investigated to determine the distributions of hydrocarbon compounds. The preliminary results show that all samples contain aliphatic hydrocarbons including n-alkanes, steranes and terpanes, probably derived from either biogenic sources (vascular plant wax input) and/or fossil fuel contamination (coal, crude oil, etc.). However, β-carotane found in the Guiyang aerosol samples may originate from geological or petroleum sources. Polynuclear aromatic hydrocarbons, which are considered to be combustion products from fossil fuels such as petroleum and, especially in this case, coal burning, are also widely distributed in all samples. Furthermore, some apparent fractionation phenomena of organic compounds are observed in samples from different heights above ground.

Geochemical Characteristics of Sphagnum Brown Coal A Possible Oil-generating Precursor

A preliminary study of newly discovered sphagnum brown coal from the Jingsuo Basin, Yunnan Province, China, which is quite rich in montan wax, indicates the predominance of highern-alkane homologues and aromatized triterpenoid components. Aromatic hydrocarbons are composed mainly of pentacyclic and tetracyclic di-, tri- and tetra-aromatic components, which are obviously diagenetically related to higher plant-derived triterpenoids naturally occurring in the biosphere. Because the sphagnum brown coal still remains in the highly immature stage, it seems that the progressive diagenetic aromatization of the higher plant-derived triterpenoids may start at a very early stage.