Abstract:

According to the research made on fluid inclusions in Lower Permian carbonate rocks in Xichang Basin,the fluid inclusions could form in every stage of reservoir diagenetic evolution,hydrocarbon generation,migration and accumulation.This could be the direct evidence for the formation environment and development stages of reservoir porosity,and for hydrocarbon generation, migration and accumulation.The study on diagenetic cements and pore-filling minerals of fluid inclusions in different stages shows that the evolution of Lower Permian source rocks and reservoir porosity development underwent following seven diagenetic stagesl,namely penecontemporaneous,early diagenetic,mid-late diasenetic,epidiagenetic,early,middle and late reburial stages.The epidiagenetic karst porosity, early reburial deep dissolution porosity and middle-late structural cracks constituted the main oil and gas reservoir spaces in hydrocarbon accumulation period. Hydrocarbon generation and primary migration occurred during LatePermian(i.e.early reburial stage); large amounts of hydrocarbon migrated and accumulated during the Triassic(middle reburial stage) and most of natural gas migration and accumulation took place in Jurassic(late reburial sarge) and thereafter.Hydrocarbon generation,migration and accumulation in the study area were closely related to Hereynian basalt eruption,and the tectonics and magmatic intrusion of indo-China and Yenshanian.