Tectonic Characteristics and Accumulation Study in Oil and Gas Reservoirs in Steep Slope Belt-With LD6 Structure in Bohai Oil Field as an Example

A medium-sized oilfield has been found in LD6 structure in recent years in Bohai sea. This structure is a stratified structural reservoir, located in steep slope in the center and south part of Liaodong low uplift. It has multilayer oil-bearing stratra in vertical, forming a typical stepped steep slope belt oil and gas reservoir. Strike-slip faults play an important role on the the structure forming, sandstone development, fault sealing and hydrocarbon migration of the LD6 structure. Structure transformation has an important role on sedimentary unloading and development of excellent quality sandstone reservoirs, which forms the material base of the best LD6 reservoir on the center and south Liaodong low uplift. The Liaozhong fault-1 goes along the same direction as the region strikeslip fault. The fault controlling the trap has strike-slip compressive characteristics, which is the key for fault lateral sealing. Oil and gas abundance are quite different between the North and South Block, the lower part of Dong-2 Member and Dong-3 Member. The hydrocarbon migration capability of extensional fault and sealing ability of controlling trap faults determined the differential hydrocarbon accumulation in the lower part of Dong-2 Member in South block of LD6 structure.