Abstract:

Shichang Subsag of Nanpu Sag is an old exploration and development area of Jidong Oilfield,the its main structural reservoir has been proven,and put into development.The next is to find new areas torelay.In this paper,the lithologic reservoir accumulation mode is established through research and analysis of tectonic evolution,sedimentary system and their controlling role on lithologic traps.That provides a theoretical basis for future exploration.In the early Shahejie Formation(Es)period,the provenance was mainly from the bulge on the upthrown side of Baigezhuang fault in the east of subsag.There existed multiple fan-delta systems along the Baigezhuang downthrown side and they prograded far towards the subsag center.Meanwhile,small fan-delta,shallow lake and semi-deep lake sediments distributed along the downthrown side of Xinanzhuang faults in the west.In the late Es,the activity of Baigezhuang fault leaded to the inversion of early strata attitute.And the early downlap sandbody pinched on the slope, forming a updip pinchout type deposition mode.These sand bodies and sub-sag cooperated with west uplift tectonic introversion to form the updip pinchout trap,which formed the most important lithologic reservoirs in Shichang Subsag.These reservoirs have the characteristics of multi-strata-enrichment,large-scale and multi-oil-water systems.

Key words: accumulation mode, lithologic reservoir, Shahejie Formation, Shichang Subsag, Nanpu Sag