中国石油生产的展顾

本文分析了中国石油生产近20年变化的原因,对一些学者认为80年代中国会成为超级产油大国,后又悲观断定80年代中国可能变成石油净进口国作了评述。同时对90年代中国石油生产前景作了初步展望。     

Methane‐related microbial gypsum calcitization in stromatolites of a marine evaporative setting (Münder Formation,Upper Jurassic,Hils Syncline,north Germany)

Fossil stromatolites may reveal information about their hydrochemical palaeoenvironment, provided that assignment to a specific microbial community and a corresponding biogeochemical mechanism of formation can be made. Tithonian stromatolites of the Münder Formation at Thüste, north Germany, have traditionally been considered as formed by intertidal cyanobacterial communities. However, thin sections of the stromatolites show elongated angular traces of former gypsum crystals in a dense arrangement, but no algal or cyanobacterial filament traces. Moreover, high Fe²⁺ and Mn²⁺ contents, oxygen‐isotope and sulphur‐isotope ratios of carbonate‐bound sulphates, and sulphurized hydrocarbon biomarkers of the stromatolitic carbonate indicate that CaCO₃ precipitation occurred near the oxic–anoxic interface as a result of intensive bacterial sulphur cycling rather than photosynthetic activity. Furthermore, anaerobic oxidation of methane by Archaea may have driven CaCO₃ precipitation in deeper parts of the biofilm community, as reflected by high concentrations of squalane with a strongly negative δ¹³C in conjunction with evaporite pseudomorphs showing extremely low δ¹³C_Carb ratios. Consequently, the Thüste stromatolites are now interpreted as having initially formed by gypsum impregnation of biofilms. Subsequently, early Mg‐calcitic calcitization within the biofilms occurred because of combined bacterial iron, manganese and sulphate reduction, with an increasing contribution of anaerobic oxidation of methane with depth. This model plausibly explains the prominent preservation of signals derived from oxygen‐independent metabolic pathways, whereas virtually no geochemical record exists for an aerobic community that may, nevertheless, have prevailed at the stromatolite surface. Photic‐zone stromatolites with a prominent signal of anaerobic oxidation of methane may be common in, and indicative of, oxygen‐depleted sulphate‐bearing environments with high rates of methane production, conditions that possibly were fulfilled at the Archaean to Proterozoic transition.     

藏南白垩系黑-红层沉积岩有机质组成分布特征

对藏南江孜县床得剖面白垩系黑层和红层沉积岩进行的有机地球化学研究表明,黑层有机碳含量高于红层5～10倍,红层和黑层饱和烃主峰碳数分别为nC25和nC23;黑层和红层沉积有机质的母质来源都以水生植物和菌藻类等低等生物为主,陆源有机质的输入非常有限;但饱和烃的分布和主峰碳数的差异可能反映了有机母源物质在种群方面的差异,而这种差异可能主要是水体温度存在差异造成的,即红层发育时期水体温度可能高于黑层沉积时期.而在高温度条件下,水生生物和陆生植物的生长发育受到限制,造成原始有机质产率和有机质沉积保存量低可能是红层沉积岩形成的主要原因.     

The effects of gas flaring on crops in the Niger Delta,Nigeria

Flaring of associated gas from oil exploitation has several consequences on the environment. This study explores the spatial variability effects of gas flaring on the growth and development of cassava (Manihot esculenta), waterleaf (Talinum triangulare), and pepper (Piper spp.) crops commonly cultivated in the Niger Delta, Nigeria. Data was collected on soil and atmospheric temperature and moisture at a 20-m interval, starting at 40 m from the flare point to a distance of 140 m. Lengths and widths of crop leaves, height of crop plants and cassava yields were measured at the specified distances. The amino acid, ascorbic acid, starch, and sugar constituents of the cassava yields were determined. The results suggest that a spatial gradient exists in the effects of gas flares on crop development. Retardation in crop development manifests in decreased dimensions of leaf lengths and widths of cassava and pepper crops closer to the gas flare point. Statistical analysis also confirms that cassava yields are higher at locations further away from the flare point. In addition, the amount of starch and ascorbic acid in cassava decreased when the plant is grown closer to the gas flare. High temperatures around the gas flare appear to be the most likely cause of this retardation. The waterleaf crop, on the other hand, appears to thrive better around the gas flare point.     

A summary of the geology and oil habitat of the Eastern Flank Hydrocarbon Province of South Oman

The Eastern Flank Hydrocarbon Province borders the southeastern edge of the South Oman Salt Basin in the southern part of Oman. An intensive exploration programme by PDO over the past seven years has led to the discovery of almost 2 × 10⁹ m³ of oil with current production of some 15000 m³/d from six fields.In stark contrast to other oil habitats of the Arabian Peninsula, the main play involves rock units and geological events ranging in age from Late Precambrian to Quaternary Times, while trap development and charging are closely related to syn-tectonic salt dissolution.The principal reservoirs and seals are poorly consolidated, Palaeozoic clastics which drape, due to salt dissolution, over residual ‘cores’ principally composed of either Lower Palaeozoic sandstones (Haima Group), or Late Proterozoic carbonates (Huqf Group), or some combination of these. Oils have been geochemically correlated with algal source rocks of the Huqf Eastern Flank. Structures are considered to have been ‘charged’ from Late Mesozoic times onwards in conjunction with progressive subsurface salt removal and the onset of maturation of local source rocks. The effectiveness of ‘charging’ along the retreating salt edge is indicated by the small percentage of dry wells.Major oil zones are found in both anticlinal and truncation traps which are commonly developed around sandstone (Haima Group) cores. Oils show a wide range of characteristics but are typically heavy, early expulsion crudes, high sulphur with little associated gas. Bacterial transformation is not uncommon.Producing reservoirs mainly occur at relatively shallow depths (600–1200 m). Primary recovery factors of around 7% reflect the high density and viscosity of the Eastern Flank crudes and have initiated interest in Enhanced Oil Recovery (EOR) techniques. Two such pilot projects, involving steam and polymer flooding, are due to commence in 1984 and, if successful, will substantially increase the reserve base of these fields.     

Variation in microbial biomass and community structure in sediments of peter the great bay (sea of japan/east sea), as estimated from fatty acid biomarkers

Variation in the microbial biomass and community structure found in sediment of heavily polluted bays and the adjacent unpolluted areas were examined using phospholipid fatty acid analysis. Total microbial biomass and microbial community structure were responding to environmental determinants, sediment grain size, depth of sediment, and pollution due to petroleum hydrocarbons. The marker fatty acids of microeukaryotes and prokaryotes - aerobic, anaerobic, and sulfate-reducing bacteria -were detected in sediments of the areas studied. Analysis of the fatty acid profiles revealed wide variations in the community structure in sediments, depending on the extent of pollution, sediment depth, and sediment grain size. The abundance of specific bacterial fatty acids points to the dominance of prokaryotic organisms, whose composition differed among the stations. Fatty acid distributions in sediments suggest the high contribution of aerobic bacteria. Sediments of polluted sites were significantly enriched with anaerobic bacteria in comparison with clean areas. The contribution of this bacterial group increased with the depth of sediments. Anaerobic bacteria were predominantly present in muddy sediments, as evidenced from the fatty acid profiles. Relatively high concentrations of marker fatty acids of sulfate-reducing bacteria were associated with organic pollution in this site. Specific fatty acids of microeukaryotes were more abundant in surface sediments than in deeper sediment layers. Among the microeukaryotes, diatoms were an important component. Significant amounts of bacterial biomass, the predominance of bacterial biomarker fatty acids with abundance of anaerobic and sulfate-reducing bacteria are indicative of a prokaryotic consortium responsive to organic pollution.     

Exchange flow of oil and sea-water in a ruptured submarine pipeline

The rupture of a submarine oil pipeline starts various mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and sea-water is difficult to estimate. A simple mathematical model has been developed and laboratory experiments have been carried out to obtain an insight into the density-driven exchange flow and to determine the leak rate. The mathematical model is predictive and takes account of the effects of friction, inclination of the pipeline, and inertia of the fluid. The experiments were done in a horizontal model pipeline. Theoretical and experimental results are in satisfactory agreement.     

Facies recognition of some Tertiary coals applied to prediction of oil source rock occurrence

Coals are oil source rocks in many of the Tertiary basins of Southeast Asia. The precursors of these hydrogen rich and oxygen poor coals are coastal plain peats which have mainly developed in an everwet and tropical climate. In these environments water flow and reworking can concentrate liptinitic kerogen in preference to vitrinitic kerogen. The distribution, petrography and chemistry of the coaly Miocene source rocks present in the Kutai Basin are described. The recognition of environmental controls on the accumulation of potentially oil-prone coals and coaly shales in deltaic environments is an aid to predictive source bed recognition in petroleum exploration. Comments on the environment of deposition of coaly sediments in the basins of the Norwegian Sea are discussed with reference to their possible oil and/or gas sourcing potential. The Triassic - Jurassic coals of the Haltenbanken area may become more oil-prone towards the delta margins, and facies mapping could aid oil exploration in this area.     

Uncertainty in predictions of oil spill trajectories in open sea

A method is introduced to calculate and to account for the uncertainties in the predictions of oil spill trajectories using a classic oil spill model. The method considers the output of the oil spill model as a function of random variables, which are the input parameters, and calculates the standard deviation of the output results which gives a measure of the uncertainty of the model given the uncertainties of the input parameters.Instead of a single trajectory that is calculated by the oil spill model using the mean values of the parameters, a band of trajectories can be defined when various simulations are done taking into account the uncertainties of the input parameters. This band of trajectories defines envelopes of the trajectories that are likely to be followed by the spill given the uncertainties of the input.The method is applied to an oil spill that occurred in open sea near Madeira Islands, in the Atlantic Ocean, in December 1989. The simulations allow the understanding of how a change in the wind direction drove the spill towards the Islands.The envelope of likely trajectories that is obtained with the uncertainty modelling shows a band of trajectories that is in better agreement with the observations than the single trajectory simulated by the oil spill model, based on mean parameters.     

Detection of DNA damage in mussels and sea urchins exposed to crude oil using comet assay

The single-cell microgel electrophoresis assay or the comet assay was used to evaluate DNA damage of dispersed crude oil on sea urchins (Strongylocentrotus droebachiensis) and mussels (Mytilus edulis L.). Sea urchins were exposed to 0.06 and 0.25 mg/L dispersed crude oil in a continuous flow system, while the mussels were exposed to 0.015, 0.06 and 0.25 mg/L dispersed crude oil. Sea urchin coelomocytes and mussel haemocytes were sampled after 4 and 5 weeks exposure, respectively. In the sea urchin coelomocytes, there was a significant concentration-related increase in the percentage of DNA in comet tail. In mussel haemocytes, there was a significantly higher percentage of DNA in comet tail for all treatments compared to the control. The responses were concentration-related up to 0.06 mg/L oil. The two highest exposure concentrations of mussels were not significantly different from each other. These results indicate that the comet assay can be used for biomonitoring of DNA damage in marine invertebrates following oil contamination.