Fluid inclusions in the Xichang Basin and their applications in oil-gas exploration

Abstract

Fluid inclusions are commonly observed in various stages during the diagenetic evolution and the generation, migration and accumulation of hydrocarbons in Lower Permian carbonate rocks in the Xichang Basin, providing direct physico-chemical evidence for the process. Altogether seven stages can be recognized, i.e., the penecontemporaneous, early and mid-late diagenetic stages, the epidiagenetic stage and the early, middle and late reburying stages. Karst and dissolution pores and structural fissures developed during the epidiagenetic and reburying stages constitute the major reservoirs for hydrocarbon accumulation. Oil generation and migration began in the early reburying stage in Late Permian time and developed to its climax in the middle reburying stage in the Triassic period, followed by extensive generation and migration of natural gases during the late stage of reburying in the Jurassic and later periods. The generation, migration and accumulation of hydrocarbons are closely related to Hercynian basalt eruption and Indosinian and Yenshanian tecto-magmatism.