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鄂尔多斯盆地二叠系山西组海陆过渡相页岩是重要的页岩气勘探层位,为了深入研究山西组海陆过渡相页岩含气性及气体地球化学特征,选取2口钻井岩芯样品进行了现场解析气量测定、解析气组分和稳定碳同位素分析以及相关有机地球化学分析,认为山西组海陆过渡相页岩具备页岩气生成的良好地质条件.研究结果表明:山西组页岩有机质丰度较高(TOC为1.73%~3.09%),干酪根类型为Ⅲ型,并处于成熟—高成熟演化阶段;解析气中,甲烷体积分数为80.07%~96.29%,平均值为88.79%,甲烷和乙烷的碳同位素值分别介于-49.2‰~-36.9‰和-17.1‰~-15.4‰之间,碳同位素均具有δ~(13)C_1<δ~(13)C_2的正序分布特征,属于有机热成因气;山西组页岩解析气含量平均值为0.38 m3/t,处于已具备页岩气生产能力的四川盆地五峰组—龙马溪组页岩解析气含量范围之内,表明鄂尔多斯盆地山西组海陆过渡相页岩具有较好的页岩气勘探潜力.
In order to study the gas-bearing and geochemical characteristics of the continental-continental transitional shale in Shanxi Formation, two samples of core-drilling cores were selected for the marine-continental transitional shale of the Permian Shanxi Formation in Ordos Basin. Analytical gas analysis, gas composition analysis, stable carbon isotope analysis and related organic geochemical analysis show that the Shanxi-continental transitional-phase shale has favorable geological conditions for shale gas generation.The results show that the organic matter abundance (TOC was 1.73% ~ 3.09%), and kerogen type was type Ⅲ, and was in the stage of mature-high maturity evolution. In the analytic gas, the volume fraction of methane was 80.07% ~ 96.29% with an average of 88.79% The carbon isotope values of ethane range from -49.2 ‰ to -36.9 ‰ and -17.1 ‰ to -15.4 ‰, respectively. The carbon isotopes have the positive sequence distribution of δ ~ (13) C_1 <δ ~ (13) Which belongs to organic pyrogenic gas. The average content of analytic gas in shale of Shanxi is 0.38 m3 / t, which is within the analytic gas content of shale of Wufeng Formation-Longmaxi Formation in Sichuan Basin that has shale gas production capacity, indicating that the Ordos Basin Shanxi group of continental transitional shale It has good exploration potential shale gas.