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通过对川西地区上三叠统须家河组地球化学特征的研究,其天然气组成主要以烃类气体为主,甲烷的含量在80%~91%,天然气组成特征为碳、氢同位素较轻,δ13C1介于-35‰~-32‰,δ13C2H6介于-25‰~-23‰;δDCH4介于-164‰~-154‰,δDC2H6介于-137‰~-125‰;天然气的干燥系数(C1/C1-5)介于0.89~0.98,普遍大于0.95,为干气。由于须家河组天然气中不含有H2S,天然气中甲烷碳同位素值与干燥系数之间成正相关关系,表明须家河组天然气属于典型的煤成气。
Based on the study of the geochemical characteristics of the Upper Triassic Xujiahe Formation in western Sichuan, the natural gas is dominated by hydrocarbon gas with a methane content of 80% -91%. The natural gas is characterized by a relatively low level of carbon and hydrogen isotopes, δ13C1 ranged from -35 ‰ to -32 ‰, δ13C2H6 ranged from -25 ‰ to -23 ‰, δDCH4 ranged from -164 ‰ to -154 ‰ and δDC2H6 ranged from -137 ‰ to -125 ‰. Natural gas drying coefficients (C1 / C1-5) ranged from 0.89 to 0.98, generally greater than 0.95 for dry gas. As the natural gas in Xujiahe Formation does not contain any H2S, the carbon isotope value of methane in natural gas is positively correlated with the drying coefficient, indicating that the natural gas in Xujiahe Formation is a typical coal-formed gas.