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阐明鄂尔多斯盆地东胜气田天然气地球化学特征并厘清其天然气成因及来源.基于该气田的6口井及前人已经发表的其它主要气田25口井天然气组分、碳等同位素特征,轻烃组分特征及实际地质背景,对该气田天然气地球化学特征及来源进行了较详细分析,认为东胜气田天然气具有与上古生界其它气田相似的成因,为典型的煤成气;该气田天然气组分、同位素及轻烃特征与其南部苏里格气区存在明显差异,该气田天然气主要来自于其下伏煤系并非来自于南部烃源岩.研究结果表明:东胜气田天然气以烷烃气为主,表现为干气,天然气中甲烷体积分数为93.69%~93.96%,乙烷体积分数为3.57%~3.71%,丙烷体积分数为0.85%~0.92%,丁烷体积分数为0.21%~0.37%;含少量非烃气体CO_2和N_2;烷烃气碳同位素具有正碳同位素系列,表现为原生特点;C_7轻烃化合物表现为甲基环己烷优势,庚烷值及异庚烷值分布区间分别为14.3%~16.0%和1.9%~2.6%,结合碳同位素认为该气田为烃源岩成熟-高成熟过渡带阶段形成的天然气;天然气K_1值[K_1=(2-甲基己烷+2,3-二甲基戊烷)/(3-甲基己烷+2,4-二甲基戊烷)]为1.2.
The geochemical characteristics of natural gas in Dongsheng gas field of Ordos Basin and the origin and origin of natural gas are clarified.According to the natural gas composition, carbon isotopic characteristics of 25 wells in 6 wells of the gas field and other major gas fields previously published, the light hydrocarbon component Characteristics and actual geological background of the gas field, the geochemical characteristics and sources of natural gas in the gas field are analyzed in detail. The gas in Dongsheng gas field is similar to other gas fields in the Upper Paleozoic and is typical coal gas. The natural gas components, The characteristics of isotopes and light hydrocarbons are significantly different from those in the southern Sulige gas area, where the natural gas mainly comes from the underlying coal measures and not from the southern source rocks. The results show that the natural gas in Dongsheng gas field is dominated by alkane gas, In dry gas, the volume fraction of methane in natural gas is 93.69% -93.96%, the volume fraction of ethane is 3.57% -3.71%, the volume fraction of propane is 0.85% -0.92%, and the volume fraction of butane is 0.21% -0.37% Non-hydrocarbon gases CO_2 and N_2; the carbon isotopes of alkanes have a positive carbon isotope series, showing native characteristics; C_7 light hydrocarbon compounds showed the advantages of methylcyclohexane, heptane and isoheptane values Cloths range from 14.3% to 16.0% and 1.9% to 2.6%, respectively. Combined with carbon isotope, it is considered that this gas field is natural gas formed at maturity-high maturity transition zone of source rock. The K_1 value of natural gas [K_1 = (2-methylhexane + 2,3-dimethylpentane) / (3-methylhexane + 2,4-dimethylpentane)] was 1.2.