Hydrocarbon enrichment regularity of marine carbonate in Sichuan Basin

Sichuan Basin, as one of the six atmospheric regions in China, has made outstanding contribution to the rapid development of natural gas in China. The thickness of marine craton deposits is 4000-7000 m, and marine carbonate rocks are the main gas enrichment strata. In order to further guide the direction and target of natural gas exploration for marine carbonate rocks in the basin, the authors, based on previous research results and many years'exploration experience and starting with key geological factors controlling hydrocarbon accumulation, have systematically summarized the regularity of natural gas enrichment in marine carbonate rocks in Sichuan Basin, and reached some conclusion:"source control" on the whole controls complementary distribution of source rocks in space, and vertical and horizontal distribution of natural gas shows that the gas-bearing property of reservoirs which are close to source rocks in vertical direction is generally better, and the horizontal distribution of oil and gas reservoirs around high-quality source rocks (gas or oil center) is circular; the "facies-controlled" favorable sedimentary facies zone has obviously controlled reservoir development and natural gas enrichment, that is, there exist "facies-controlled reservoir and reservoir-controlled reservoir"; the karstification improves carbonate rocks, i.e., improves reservoir permeability conditions of gas reservoirs; inheritance development of paleo-uplift controls the early migration and accumulation of oil and gas reservoirs; and present structure plays an important role in controlling the readjustment and redistribution of gas reservoirs. By comprehensively applying the regularity of natural gas enrichment, Sichuan Basin has made several major discoveries and breakthroughs and submitted proven reserves exceeding trillion square meters, which has greatly promoted the rapid development of natural gas in China.