鄂尔多斯盆地苏里格气田上古生界天然气地球化学及成藏特征

苏里格气田是鄂尔多斯盆地上古生界内发现的大型岩性气藏。天然气中甲烷占绝对优势，干燥系数低，为湿气。灭然气的单体碳同位素具有碳数越高，同位素越审的特点，且正构烷烃碳同位素具有δ^13C1〈δ^13C3〈δ^13C2〈δ^13C4的规律。甲烷碳同位素与甲烷含量旱正相关，与乙烷含量为负相关。根据天然气单体碳同值素及其含垣变化，认为苏里格天然气属煤成气。天然气中含少量CO2气，多为有机成因。苏里格气田二叠系气藏的形成与演化可划分为石炭一二叠纪至中侏罗世气源岩沉积埋藏阶段、晚侏岁世至白垩纪天然气形成阶段和第三纪至现今的保存改造阶段。

Geochemistry and accumulation of the Upper Palaeozoic natural gas in the Sulige Gas Field,Ordos Basin

The Sulige Gas Field is a giant litholitic gas reservoir in the Upper Palaeozoic strata in the Ordos Basin. The determinations of gas chromatography indicates a kind of humid gas with lower dryness and dominant methane. The carbon isotopes in n-alkane exhibit a trend of δ13C1＜δ13C3＜δ13C2＜δ13C4. There is a positive correlation between the carbon isotopes and methane contents, and a negative correlation between the carbon isotopes and ethane contents. The variations in the contents of carbon isotopes show that the natural gas from the Sulige Gas Field is a kind of coal-derived gas of organic origin and contains minor amount of CO2. The Permian gas reservoirs went through the deposition and burial of the source rocks during the Carboniferous-Permian to the Middle Jurassic, formation of the gas during the Late Jurassic to the Cretaceous, and preservation and modification of the gas from the Tertiary onwards.