Hydrocarbon source and accumulation in Upper Triassic to Lower Jurassic in the Tongnanba area, northeastern Sichuan Basin

Abstract

The research of natural gas is limited in the Upper Triassic to Lower Jurassic in the northeastern Sichuan Basin for a long time, with the source and accumulation of natural gas still being controversial. Based on a case study of the northeastern Sichuan Basin, the source of natural gas is discussed through the analysis of fluid inclusion and biomarker data, and the hydrocarbon accumulation is analyzed. It reveals that the gas is mainly from Permian marine source rocks in the Changxing Formation and Triassic terrestrial source rocks in the Xujiahe Formation. Two filling models of the hydrocarbon are put forward. One filling stage dated from the Middle to Late Jurassic, natural gas, generated in marine strata, accumulated in the reservoir of the Xujiahe Formation through the large boundary faults. The other filling stage is in the early Cretaceous, a large amount of natural gas generated by source rocks in the Xujiahe Formation, accumulated in the reservoirs of the same formation, and natural gas, generated by marine source rocks, can also be accumulated in reservoirs of Xujiahe Formation through the boundary faults.