Abstract:Based on the unconformity contact type, distribution law, structural characteristics and transport type of the buried hill top in Shulu Sag, Jizhong depression, the vertical karst zoning characteristics of the semi-weathered rock layer under unconformity are described. On this basis, the thermal evolution of source rocks and hydrocarbon migration in typical section are simulated, and the migration and accumulation modes of oil and gas in buried hills are summarized. The results show that there are four contact types, five structural types and three transport types in the unconformity of buried hill in shulu sag, among which the slope area and the west of the depression area are mainly of lateral type, the local structural high point of the slope area and high-in-sag is of lateral and trap type, and the uplift area is of lateral and vertical type. Under the unconformity, the semi-weathered rock can be divided into epigenetic karst zone, vertical percolation zone and three horizontal undercurrent zones. The vertical percolation zone developed at the top of the buried hill is the main transport layer for oil and gas migration along the unconformity surface, and the multi-stage horizontal undercurrent zone developed in the inner reservoir is the potential channel for oil and gas migration to the inner reservoir. Differences in thermal evolution of deep and shallow source rocks and whether they are in contact with thin-layer conglomerates lead to differences in oil and gas charging in buried hills of slope areas and depression area. The slope area has a hydrocarbon migration and accumulation mode of efficient transfer of thin-layer conglomerate, lateral migration of unconformity, transfer to inner reservoir in the horizontal undercurrent zone, upward transmission of forward fault, reverse fault trap hydrocarbon.