松辽盆地梨树断陷天然气地球化学特征及成因探讨

Geochemical characteristics and origin of natural gas in Lishu Fault Depression,Songliao Basin

通过系统测试松辽盆地梨树断陷3个气田和3个油气田天然气的化学组成以及碳同位素组成,分析了天然气的组成特征与平面分布特征,综合判断了各油气田天然气的成因类型。梨树断陷的天然气以烃类为主,CO2含量低,烃类气体和CO2均为有机成因,可以分为3种成因类型。第一类为不同成熟度的油型气的混合气,主要分布在北部斜坡带的皮家气田和中央构造带的八屋、四五家子油气田,碳同位素多发生了倒转;第二类为高—过成熟阶段形成的煤成气,分布在中央构造带南端的孤家子气田和东南斜坡带的新立油气田,具有负碳同位素系列;第三类为油型气和煤成气的混合气,分布在中央构造带的后五家户气田。

Based on the analyses of natural gases from three gas fields and three oil fields, the composition and plane distribution of natural gases in the Lishu Fault Depression of the Songliao Basin were discussed and the ge- netic types of gas were identified. Natural gas in the Lishu Fault Depression contains significant alkane gases and a little nonhydrocarbon gases, especially CO2. Alkane gases and COa were organic genesis and there were three genetic types of alkane gases in the Lishu Fault Depression. The first type was mixed by oil-type gases with differ- ent maturities, mainly located in Pijia gas field, Bawu and Siwujia oil fields, with partly reserved order of δ13 C. The second type was coal gases with high and over maturity, located in Gujiazi gas field and Xinli oil field, with reversed order of δ13C. The third type was mixed by oil-type gas and coal gas, located in Houwujiahu gas field.