川西坳陷的复合构造与油气关系

川西坳陷受多期构造事件影响,较普遍地存在同轴叠加型、横跨型和斜接型等复合构造。这些复合构造形成时间早,有利于天然气在须家河组砂岩致密化之前适时运移、聚集成藏。构造的复合有利于形成破裂构造。这些破裂构造一是改善了储层的渗流条件,提高了气井产能;二是沟通了深层源岩与浅层储层,形成远源型气藏。川西坳陷大断裂是在多期次构造事件中复合形成的,造成了气藏的破坏。在远离大断裂面的区域,因储层非均质性,有可能残存有中、小型气藏。

Compound structures and hydrocarbons in western Sichuan depression

Compound structures, such as coaxial superimposed, cross-over and mitre types, are common in western Sichuan depression as a result of multistage tectonic events. They have been formed early, thus would have been favorable for timely migration and accumulation of gas prior to the tightening of Xujiahe Formation sandstones. Compounding of structures would be favorable for the formation of crush structures, which would have improved the percolating conditions of the reservoirs and productivity of gas wells, and would have established communication between deep source rocks and shallow reservoirs, leading to the formation of gas pools far from their sources. The large fracture in western Sichuan depression has been formed as a result of multistage tectonic events and has led to the destruction of gas pools. Medium and small gas pools might have been preserved in areas far from the large fracture, due to the inhomogeneity of the reservoirs.