Forming mechanism of low porosity-permeability gas pool and exploratory potential in West Sichuan depression

摘要

Since late Triassic, the west depression where is located in the west Sichuan basin, has undergone to structural events six times and developed five types of primary basins with different properties. The stacking of those basins, resulting in change of sedimentary fades and petrophysical property, structural deformation and fractural distribution, and fluid property and stress field, forms different kind of gas pools dominated by Xujiahe super-pressure gas source. Gas generation, migration and accumulation in west depression are a complex and united dynamic balance system. The mechanism can be summarized as rich source rock, timely uplift and 3 kinds of gas migration models. According to the gas forming mechanism, Xujiahe-2nd structural-fracture gas pool, Shaximiao structural-diagenetic gas pool and Penglaizhen lithologic gas pool are developed in the area. The area with rich gas resource should be our further main exploration domain and target in the near future.