英吉苏凹陷英南2气藏天然气成因判识

Genesis Recognition of Yingnan 2 Gas Reservoir in Yingjisu Sag of Tarim Basin

摘要: 依据英南2井天然气组分特征、碳同位素特征及成藏时间等方面的研究,对英南2气藏成因进行了探讨,认为英南2气藏为一经后期调整的次生气藏。天然气为奥陶纪晚期—志留纪早期生成并保存在志留系和奥陶系上部储层中的凝析气、原油伴生气和加里东末期生成的干气的混合气,也可能有一些原油裂解气的混入。石油伴生气和凝析气是英南2井天然气高氮、富集重烃的根本原因。后期裂解干气的注入是英南2井天然气碳同位素较重的主要原因之一。扩散作用在华力西—印支期这一漫长地质时间内为奥陶系和志留系气藏保持其湿气藏特征和氮气的富集起到了重要作用。喜马拉雅晚期,古生界气藏沿断层运移到侏罗系聚集成藏,并在进入侏罗系储层后有少量的煤成气混入,进一步使天然气碳同位素变重。

Abstract: According to the study on components and its isotopes of natural gas in Yingnan 2 gas reservoir and the formation time,the paper discuss the genesis of Yingnan 2 gas reservoir,and reckon that it is a secondary gas pool formed by adjustment in the geologic history.The gas in Yingnan 2 gas pool is commixed by condensate gas,associated gas,kerogen cracking gas,and oil cracking gas.The condensate gas and associated gas are the main components and the key cause of high N2 and fixed hydrocarbon contents.