低阶煤生物成因气与热成因气模拟及其结构演化研究

发布时间：2018-07-12 20:29

本文选题：生物成因气 + 热成因气　；参考：《中国矿业大学》2016年博士论文

【摘要】：本文以吐哈盆地大南湖和准噶尔盆地阜康矿区内的低阶煤为研究对象,在煤岩煤质、孔隙结构、元素和矿物组成分析的基础上,开展了低阶煤生物成因气与热成因气模拟,分析了两种模拟方式产出气的组分、产率以及碳氢同位素组成特征,找到了煤岩遭受降解的生物标志化合物证据,提出了具有次生生物作用的生物气成因综合判据,阐释了低阶煤生物降解结构演化机制,揭示了热解烷烃气碳同位素变化的原因,分析了热解烷烃气组分、碳同位素组成与结构演化的关系。主要的研究成果如下:(1)生物降解产出气主要以CH4和CO2为主,几乎不含重烃气,且随降解时间的延续,两者含量变化具有同步效应,均呈现“波折式”缓慢上升。生物气的δ13C1值越轻,δ13CCO2值越重,两者呈“镜像”对称关系,主要由于气体同位素组成对母质的继承效应,使得轻碳同位素被分馏到CH4中,重碳同位素被分馏到CO2中。(2)煤中的可溶和不可溶有机质在生物作用的过程中均会遭受生物降解,生物降解方式是多元化的,其改造作用使得长链正构烷烃“波浪式”地逐级向低碳数方向偏移;在低阶煤可溶有机质中检测到了与生物改造作用有关的C29-藿稀、C30-藿稀和C29~C32—ββ生物藿烷系列,以及C24四环二萜烷和C31~C34五环三萜等生物标志化合物,为生物成因气的判识提供了有力证据。(3)生物降解过程中,微生物对脂族结构降解力度较大,芳香结构在一定程度上也可以降解,且发现生物降解作用具有两面性,即可促进也可阻碍芳构化进程。(4)热解过程中CH4、C2H6和C3H8的碳同位素变化的原因,在Ro,max2.0%之前主要是脂链倾向性断裂造成的,Ro,max2.0%以后可能主要是含重碳同位素的环内物质被脱除进入产物造成的。而且Ro,max=1.3%和2.0%是热解烷烃气组分、碳同位素组成与结构演化的分界点。论文的研究成果对于丰富和完善低煤阶储层煤层气成因机理具有指导作用。
[Abstract]:Based on the analysis of coal quality, pore structure, element and mineral composition of low-rank coal in the mining area of Donanhu Lake and Junggar Basin in Turpan-Hami Basin, the biogenic gas and thermal gas of low-rank coal are simulated. In this paper, the composition, yield and hydrocarbon isotopic composition of gas produced by two simulation methods are analyzed. The evidence of biomarker for coal and rock degradation is found, and a comprehensive criterion of biogas genesis with secondary biological action is put forward. The evolution mechanism of biodegradable structure of low-rank coal is explained, the reason of carbon isotope variation in pyrolytic alkane gas is revealed, and the relationship between composition, carbon isotope composition and structure evolution of pyrolytic alkane gas is analyzed. The main results are as follows: (1) Ch _ 4 and CO _ 2 are the main biodegradable gas, almost no heavy hydrocarbon gas, and with the degradation time, the changes of the two contents have the synchronous effect, both of which show a "zigzag" slow rise. The lighter the 未 13C1 value of biogas, the heavier 未 13CCO _ 2 value is. The two have a "mirror" symmetry relationship. Mainly due to the inheritance effect of gas isotopic composition to parent material, light carbon isotopes are fractionated into Ch _ 4. Heavy carbon isotopes are fractionated into CO2. (2) both soluble and insoluble organic matter in coal are biodegradable in the process of biological action. The modification resulted in the "wave-like" shift of long-chain n-alkanes to the direction of low carbon number, and the series of C29- and C32- 尾 biocarianes related to biotransformation were detected in the dissolved organic matter of low-rank coal. The biomarkers C24 tetracyclic diterpene and C31C34 pentacyclic triterpenoids provide strong evidence for the identification of biogenic gases. (3) in the process of biodegradation, the biodegradation of lipids is strong by microorganisms. The aromatic structure can also be degraded to a certain extent, and it is found that biodegradation has two sides, which can not only promote or hinder the process of aromatization. (4) the reasons for the carbon isotope changes of Ch _ 4C _ 2H _ 6 and C _ 3H _ 8 during pyrolysis. After Romax 2.0%, which was mainly caused by the tendency fracture of lipid chain, it may be mainly caused by the removal of the material in the ring containing heavy carbon isotope into the product. In addition, 1.3% and 2.0% of Roomax are the boundary points between the composition of pyrolytic alkane gas, the composition of carbon isotope and the evolution of structure. The research results of this paper can be used to enrich and perfect the formation mechanism of coalbed methane in low rank reservoirs.
【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.13

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