New Understanding of Hydrocarbon Potential and Hydrocarbon Accumulation Stages of Reservoirs of Cambrian Gaotai Formation in Eastern Sichuan Basin
The eastern Sichuan Basin is rich in Cambrian oil and gas resources,but the drilling exploration of Gaotai Formation has not made great progress in recent years.By analyzing the fluid inclusion characteristics of the Cambrian Gaotai Formation,it is of great significance to identify the hydrocarbon accumulation of the Gaotai Formation and the Lower Paleozoic gas exploration potential in the eastern Sichuan Basin.The characteristics of fluid inclusions in the study area were analyzed by means of microscope observation combined with the indirect projection dating method of fluid inclusions homogenization temperature-burial history to further determine the hydrocarbon accumulation period.The results show that the host minerals of fluid inclusions in the Cambrian Gaotai Formation are fissure filled calcite and dissolved pore filled calcite,and the homogenization temperature of inclusions ranges from 117.8 ℃ to 205.1 ℃.The charging periods mainly include the initial hydrocarbon generation charging period,the peak oil generation charging period and the crude oil cracking charging period,forming three"episodic"oil and gas charging modes,first low and then high.The three phases of fluid activity correspond to the Late Permian-Early Triassic,Middle Triassic-Early Jurassic and Middle Jurassic respectively.Comprehensive analysis of structural conditions shows that the gas bearing capacity of the Cambrian Gaotai Formation in the eastern Sichuan area is poor,but it is conducive to the migration and accumulation of natural gas in the upper middle and shallow strata,which may be the next exploration direction in this area.
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