Abstract:

The steep slope zone is an important structural belt for hydrocarbon exploration in half graben-like sag, and the structural-lithologic composite traps are developed in this zone. These  traps are important prospecting areas. However, it is very complex in structure, sedimentary facies and control factors on distribution of the structural-lithologic composite traps in this zone. Taking Shinan steep slope of Bozhong sag as an example, this paper focuses on the genesis and distribution regularity of the structural-lithologic composite traps in the steep slope zone. There are four types of structurallithologic composite traps developing in the Shinan steep slope zone, and they are updip punch-out trap, downdip punch-out trap, lateral punchout trap and physical property sealing trap. The distribution are controlled by the types and location of slope break zones, collocation relations of direction of drainage system and palaeogeomorphology, and as well as base level change. The steep slope break zone showing corner-like in plane is the most optimal field of the hydrocarbon exploration of the structural-lithologic composite trap. The structural-lithologic composite traps, which develop in the various series of strata and are distributed widely, are helpful to supplement shortages of the singular structural trap slope zone and reduce the exploration risk of the Shinan steep slope zone.   The thinking of the structural-lithologic composite trap exploration should be built in the early exploration phase in the Shinan steep slope zone.

Key words: structural-lithologic composite trap, fault slope break zone, steep slope break zone, Palaeogene, Bozhong sag