高—过成熟页岩中天然气地球化学成因模式与应用

发布时间：2018-02-27 11:50

  本文关键词： 高-过成熟页岩 天然气地球化学 页岩气成因 成因模式 页岩气赋存状态　出处：《中国地质大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：高-过成熟(Ro2.0%)是川渝鄂地区下古生界海相及南华北盆地下二叠统海陆过渡相富有机质页岩的重要特征之一。论文分析了川渝鄂地区下古生界海相和南华北盆地下二叠统海陆过渡相页岩中天然气的地球化学异常和页岩气成因,探讨了下寒武统页岩中氮气来源和富集机理,建立了页岩气演化阶段模型及高含氮页岩气成因模式,提出了页岩气来源及赋存状态的同位素判识方法,主要取得了以下认识:(1)高-过成熟页岩中天然气地球化学特征往往出现煤型气与油型气难以区分的异常现象。海相与海陆过渡相高-过成熟页岩中天然气地球化学的主要差异在于页岩气中的非烃组分,特别是体现在CO_2含量及其碳同位素组成的差异。海陆过渡相页岩气主要分布在CO_2含量大于5%且δ~(13)C(CO_2)值小于-10‰的范围内,而海相页岩气则主要分布在CO_2含量小于5%且δ~(13)C(CO_2)值大于-15‰的范围内。(2)通过对秭地1井下寒武统和南华北盆地下二叠统页岩气中烷烃碳同位素倒转的成因分析,认为两个地区页岩气同位素倒转主要是页岩气在高-过成熟阶段与水及含铁金属发生反应引发的瑞利分馏所导致。四川盆地代表性的龙马溪组页岩气钻井数据表明,页岩气中甲烷、乙烷碳同位素倒转程度与地层压力系数及初始产气量具有良好的正相关关系,对页岩气藏保存程度具有指示意义。(3)在分析了研究区页岩气地球化学特征的基础上建立了页岩气演化阶段模型。结合川渝鄂地区下寒武统页岩气地质特点建立了三种高含氮页岩气成因模式,即有机质热解成因模式、大气成因模式和复合成因模式,并对以上模式的主控因素进行了分析,对下寒武统页岩气勘探具有指导意义。(4)建立了页岩气来源和赋存状态的同位素判识方法,通过研究川渝鄂地区海相页岩气来源组成发现,随着页岩成熟度的增加,页岩气中油裂解气的比例降低。对南华北盆地海陆过渡相页岩气中游离气和吸附气含量进行计算并对比测井解释结果发现,该方法计算结果与测井解释结果具有良好的可对比性。论文系统研究了高-过成熟页岩中天然气地球化学成因及模式,延伸了页岩气地球化学的地质应用,对我国页岩气勘探实践具有一定的参考意义。
[Abstract]:) is one of the important characteristics of the Lower Paleozoic marine facies in Sichuan, Chongqing and Hubei areas and the southern North China basin underground Permian transitional facies rich in organic matter shale. The paper analyses the Lower Paleozoic marine facies and the South North China Basin in Sichuan, Chongqing and Hubei regions. Geochemical anomalies of natural gas in the transitional facies shale of the Permian sea and land and the origin of the shale gas, The source and enrichment mechanism of nitrogen gas in Lower Cambrian shale are discussed. The evolution stage model of shale gas and the genetic model of high nitrogen content shale gas are established, and the isotopic identification method of source and occurrence state of shale gas is put forward. The main results are as follows: (1) the geochemical characteristics of natural gas in the overmature shale often occur abnormal phenomenon that it is difficult to distinguish the coal-type gas from the oil-type gas. The geochemistry of natural gas in the marine and oceanic transitional facies and the over-mature shale. The main difference in science lies in the non-hydrocarbon components of shale gas, In particular, the difference in CO_2 content and carbon isotopic composition shows that the marine and continental transitional shale gas mainly distributes in the range of CO_2 content greater than 5% and 未 ~ (13) C _ (13) C _ (C) _ (CO _ (2)) value less than -10 鈥，

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