焉耆盆地含油气系统的演化

焉耆盆地位于塔里木盆地和吐哈盆地之间,其含油气系统经历了侏罗纪—白垩纪的形成与破坏阶段和第三纪—第四纪的活化与再建阶段。侏罗系水西沟群煤系在八道湾组沉积末时,进入生油门限,标志着焉耆盆地含油气系统的形成。燕山运动中晚期,侏罗系大规模冲隆及剥蚀,侏罗系源岩生烃作用终止,含油气系统被破坏。喜山期,盆地进入挤压阶段,随着第三系沉积厚度的不断加大,侏罗系源岩开始二次生烃,原含油气系统得以活化与重建。由于构造演化不均衡,南部凹陷具有“早期成藏,破坏严重,二次生油范围小,砂体不发育,油气富集程度低”的特点;北部凹陷具有“早期成藏,破坏较弱,二次生烃范围大,砂体发育,油气富集程度较高”的特点。因此,油气勘探时,应注意南、北凹陷的含油气系统特点,区别对待。

EVOLUTION OF PETROLEUM SYSTEM IN YANQI BASIN

Yanqi Basin is stituated between Tarim Basin and Tarpan-Harmi Basin.Its petrolenm system underwent the formation and destruction during Jurassic Cretaceous, the activation and reconstruction during Tertiary Quaternary. The petroleum system of the basin formed in the end of Badaowan Formation depositional stage,and was destroyed by a large scale of thrust uplift and denudation of the Jurassic System in mid late Yenshan stage,and the oil generation process was stoped. In Himalaya period,the basin was compressed.As Tertiary deposits increased,Jurassic source rocks started secondary hydrocarbon generation, thus resulting in the activation and reconstruction of the petroleum system. The inhomogeneous structurral evolution resulted in the charactoristics of early stage pool forming,serious pool destruction, small range of secondary oil generation, and poorly developed sand bodies and lower hydrocarbon enrichnrent of the south sag of the basin. Things are opposite for the north sag. These characteristics should be taken into account in hydrocarbon exploration.