Hydrocarbon sources and accumulation processes in intra-platform of the fourth member of Dengying Formation in northern Sichuan Basin

Hydrocarbon sources and accumulation processes in intra-platform of the fourth member of Dengying Formation in northern Sichuan Basin

Blog Article

The intra-platform of the fourth member of the Dengying Formation in the Upper Sinian of the Sichuan Basin is an important area for gas exploration.To clarify the hydrocarbon accumulation and enrichment patterns and distribution characteristics in this region, a study was conducted on the hydrocarbon sources and accumulation processes based on geochemical characteristics of natural gas and bitumen, thin-section observation, and fluid inclusion analysis of the intra-platform and platform margin areas.The results indicated that: (1) Compared to the platform margin areas in the fourth member of the Dengying Formation in northern Sichuan Basin, the intra-platform exhibited higher amounts of carbon isotopes in bitumen and natural gas methane and ethane, with smaller amounts of isotopes in hydrogen.

This indicated that the oil and gas in the intra-platform mainly originated from a mixed source of the Qiongzhusi Formation and Sinian hydrocarbon source rocks, with a larger contribution from the Sinian source rocks.(2) There were two phases of oil charging Hunting Boots and two phases of natural gas charging in the oil and gas reservoirs in the intra-platform of the fourth member of the Dengying Formation in northern Sichuan Basin.The first phase of low-maturity oil charging occurred in the Late Caledonian, the second phase of large-scale crude oil charging took place from the Late Permian to the Middle Triassic, the third phase involved crude oil pyrolysis gas charging during the Middle to Late Jurassic, and the fourth phase was natural gas adjustment charging in the Cretaceous.

(3) The Tongnanba area has long been located in the lower part of the paleostructure from the oil accumulation to the gas accumulation period.The crude oil and natural gas from the paleo-oil and gas reservoirs continuously adjusted and migrated towards a higher position Kettle in the front of Micang Mountain, resulting in the loss of paleo-gas reservoirs in the Tongnanba area, which now has relatively poor gas content.The Nanjiang area had a more favorable source and reservoir configuration, remaining in the higher part of the paleostructure during the main oil and gas generation periods.

It continuously received natural gas charging, and the fault sealing was good, which was conducive to gas reservoir preservation and oil and gas accumulation.Therefore, the Nanjiang area in the intra-platform is the next favorable exploration zone in the fourth member of the Dengying Formation in northern Sichuan Basin.