Strike slip fault zone characteristics of northwestern margin and geology meaning for oil-gas in Moliqing Fault Depression

Structural,sedimentary characteristics and rules of oil and gas accumulation in Moliqing Fault Depression were analyzed.Then the evolution characteristics and meanings for oil and gas exploration of strike slip fault zone in the northwestern margin were summarized.The results show that the northwestern margin fault is a high-angle strike-slip and tensional fracture in basin forming period which is inversed by extrusion stress action in Neogene.Then the strike slip fault zone of northwestern margin is formed in which many structures such as sub-thrust faults being of strike-slip nature,compressive fold and flower liking structure are developed.From a macroscopic point of view,the northwestern margin fault has gone through two evolution stages: early strike-slip extension and lately strike-slip extrusion.The strike slip fault of northwestern margin has great significance for the oil-gas exploration: the favorable formation conditions for effective reservoir bodies of underwater fans are created by the deep fault through providing tectonic environment of large slope,effective source and preservation conditions,and oil and gas productivity is high in braid channel micro-facies of middle fan.The effective traps for oil and gas accumulation are provided by factors as structure traps inside the fault zone and oil and gas sealed by thrusting fault;the strike slip fault zone in the northwestern margin is made to be a favorable oil and gas accumulation zone by effective allocation of various conditions.