川西坳陷上三叠统天然气成藏主控因素及形成模式

Main controlling factors and patterns of gas accumulation in the Upper Triassic of the western Sichuan Depression

苏永进 唐跃刚 张世华 房新娜

Su Yongjin Tang Yuegang Zhang Shihua Fang Xinna

在对川西坳陷上三叠统天然气藏的形成机理及构造演化特征进行分析的基础上,对沉积储层和圈闭发育特征研究,运用成藏动力学的原理和方法,系统归纳川西坳陷上三叠统天然气成藏的主控因素,划分成藏体系并总结形成模式。综合研究认为,川西坳陷上三叠统须家河组具备形成大中型气(田)藏的条件;充足的烃源岩和较高的生气强度、良好的输导条件、适时的古隆起和古斜坡、圈闭发育、大面积分布的巨厚储层、优良的保存封盖条件是控制上三叠统天然气成藏的主要因素;上三叠统包括下部和上部两个成藏体系,下部成藏体系包括高压驱赶和低压吸拉两种天然气成藏模式,上部成藏体系主要以毛细管导入、水溶气运移释放和浮力顺优势通道输导等3种天然气成藏模式为主,不同模式具有不同的成藏动力学机制和不同的分布特征。

Based on the analysis of the Upper Triassic structural evolution features in the western Sichuan Depression,a study of sedimentary reservoirs and trap development features is carried out in this paper.By using the theories and methods of pool-forming dynamics,we identify the main controlling factors of gas accumulation,divide plays,and present several pooling patterns.The Upper Triassic Xujiahe Formation in the western Sichuan Depression possesses the conditions for the development of giant or medium-sized gas pool/fields.The main controlling factors of gas accumulation in the Upper Triassic are abundant sources,relatively high gas generation intensity,favorable migration conditions,good timing of paleouplifts and paleoslopes,well-developed traps,widely-distributed thick reservoirs and favorable preservation and sealing conditions.Two plays are recognized in the Upper Triassic,including an upper play and a lower play.The lower one is featured by high pressure driving and low pressure attraction,while the upper one is characterized by capillary imbibition,migration and release of water-soluble gas and transporting by buoyancy through preferential pathways.Different modes have different dynamic mechanisms of pool-forming and different distribution characteristics.

10.11743/ogg20100117