Abstract: Through the analysis of migration systems in subground rocks, this paper indicates that the oil -gas migration system is consisted of three main element, i.e. the pore, fracture and the pore-fracture combination. This paper puts forward the simple migration system consisting of connecting sand body, fault and unconformity surface, as well as the compound migration system consisting of sand body -unconformity surface, sand body -fault, unconformity surface-fault, or sand body-unconformity surface-fault, and both kinds of subground migration systems provide a three diamentional channel network for oil-gas migration. The type of oil-gas migration systems control the forming pattern of oil-gas reservoir. Connecting sand body migration systems may controls the forming of oil-gas reservoir due to bottom bed over- lap, lithologic pinch out, and/or the fault hairier. The migration system consisting of unconformity surface, sand body- unconformity surface,and/or unconformity surface- fault, may control the forming of the bedrock weathered crust type oil-gas reservoir. The migration system consists of fault, sand body-fault, and/or sand body-unconformity surface, may control formation of oil-gas reservoir due to fault block, anticline, structure-lithologic, and/or fault-lithology.

Key words: oil and gas migration, reservoir formation, pore throat, fracture, fault, unconformity