Abstract:

Oil and gas seepages and asphalt shows are not rate from the Lower Cambrian to the Cretaceous in the Chuxiong Basin.An analysis of Sazhi plaeo-reservoirs in the basin reveals that they were destroyed mainly because of surface exposure caused by later structural uplifting and large-scale erosion.Extensional fractures induced by later compression and thrusting connected the reservoirs with the surface and therefore also contributed a lot to the destruction of the reservoirs.There are two types of reservoir space.One is original pores which dominate the lower part of the reservoir(the Upper Triassic),and the other is fractures which are predominant in the lower part of the reservoir(the Jurassic).Bitumen occurring in the pores of the lower reservoir interval is believed to be the remnant of early-formed lithologic-stratigraphic reservoirs,indicating that the slope and uplift zones are the favorable places for the formation of paleo-lithologic-stratigraphic reservoirs as they are regarded as the final destination of oil and gas migration.

Key words: pore-type reservoir space, fracture-type reservoir space, condition of hydrocarbon accumulation, Sazhi paleo-reservoir, Chuxiong Basin