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Analysis Of Metabolites Of Microbial Degradation Of Crude Oil

Posted on:2014-02-01Degree:MasterType:Thesis
Country:ChinaCandidate:X B GuoFull Text:PDF
GTID:2250330401480618Subject:Institute of Geochemistry
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With the increasing demand for energy in the modern world and the continuous development of oil-gas exploration technology, petroleum geologists pay more attention to the heavy oil resources gradually. Biodegradation is an important subordinate change process of the crude oil in the reservoir, which is also one of the main mechanisms of crude oil densifying. The crude oil in most of the world has been suffered from various degrees of biodegradation, which has seriously changed the physical and chemical properties of crude oil. That results in greater uncertainty in the identification of crude oil’s maturity and in the course of routine oil sources correlation. And it becomes one of the most difficult problems in the current research on oil sources. Therefore, the study on the feature, the formation mechnism and conditions of the microbe degrades chemical composition of crude oil has been a hot area of petroleum geochemistry. In the geological conditions, the formation of the crude oil’s biodegradation may result from the two mechanisms, aerobic degradation and anaerobic degradation. In the circumstances of the reservior elevated to the near-surface, aerobic degradation plays a leading role. However, in the circumstances of the reservior in deep-surface, anaerobic degradation plays a leading role. For research geochemical characteristics’ changes and differences in the process of aerobic degradation aerobic degradation converted to anaerobic degradation and anaerobic degradation of crude oil, taking quantitutive analysis to absolutely concentration of the various biomakers, that have a very important significance in ascertaining the fundamental reasons of making geochemistry feature differences in anaerobic degradation and anaerobic degradation of crude oil, in establishing quantitive evaluation model of biodegradation and in clarifying the mechanism of biological degradation.It can also predict the impact of biological degradation, decline the exploration risk, what’s more, can provide the basis for the programe in the development of oil fields.This paper is divided into four parts.The first part is introduction. The second part is the process of microbe degradation of crude oil and equipment analysis. The third part is the analysis of result. And the last part is conclusion and understanding.This thesis mainly analyses before and after three models of biodegradation of crude oil, ethnic components of crude oil, various biomakers and non-hydrocarbon acid components monocarboxylic acids’ changes and so on in the laboratory conditions. And then study how aerobic and anaerobic microbes degradate crud oil under the laboratory conditions and inquire the mechanism of microbe degradation of crude oil.The results are as follows:(1) After microbe’s degradation of crude oil, its ethnic composition change,the relative percentages of saturated hydrocarbon decrease, the relative percentages of aromatic, non-hydrocarbon and asphaltene rise. Saturation/aromatic ration decreases. (2) Biodegradation of a saturated hydrocarbon has its own sequence:the n-alkane>isoprenoids>hopanoids,the n-alkanel(the carbon numbers less than21>the n-alkane (the carbon numbers more than22).(3) After the biodegradation, the concentration of hopanes and sterane decrease unremarkable which results from greatly exhausting the normal alkane. In crude oil which degraded slightly, the biomarker parameters of hopanes and sterane still have geochemical significance.(4) Anaerobic microorganism can use crude oil directly as its carbon source. Sulfate-reducing bacteria can degrade saturated hydrocarbons and aromatic hydrocarbons. Anaerobic microorganism can degrade aromatics more earier than the hydrocarbon degrading bacteria(aerobic bacteria), however, the methane-producing bacteria can degrade chain alkanes more easier than the sulfate-reducing bacteria.(5) Anti-biodegradation of aromatics capacity is not strong.In aerobic degradation of crude oil, when the normal alkane is not complete degraded, the series naphthalene’s degradation has begun; however,in the anaerobic degradation, the normal alkane and naphthalene’s degradations begin at the same time.(6) It is quite different between monocarboxylic acids’ carbon number distribution and the n-alkane’s carbon number distribution. And the components of low-carbon hold absolute superiority. It means that the peak of n-hexadecan oil acid is the main peak which shows strong even carbon predominace. However, the content of the high carbon components(>C22) is low. Going through the biodegradation, the carbon number distribution of monocarboxylic fatty acid has no changes. The process of biodegradation is so complicated that monocarboxylic fatty acid series from different degradation period may have different distribution patterns.
Keywords/Search Tags:biodegradation, bulk compositions, biomarker, n-monocarboxylic fattyacids
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