Research on hydrocarbon accumulation models of gentle slope belt of half graben-A case study of Qibei slope belt

The area in gentle slope belt of half graben has a big area and a gentle slope belt.The sand bodies from far source has the characteristics of big sorting and good physical properties,while the sand bodies from near source has the characteristics of big drainage area and superior hydrocarbon accumulation conditions.The Qibei slope belt has the characteristics of big area and multi-stages.Influenced by the sources in Kongdian,Gangxi and Yanshan,various sand bodies such as braded delta and offshore subaqueous fans were superimposed on multi-stages slope,forming the pattern of full slope sand.The middle,lower slopes are located among the Paleogene effective source rock,with the characteristics of " two-phase infilling,first oil second gas,differ-ential accumulation and upper oil lower gas ", forming the most favorable target exploration area with contiguous distribution and big superimposed area of multilayer systems of lithologic-stratigraphic reservoirs.