Geochemical Characteristics And Origin Of Shale Gas In Wufeng Formation-longmaxi Formation In The Southeast Of Chongqing

Based on the analysis of the organic matter abundance,thermal evolution degree,kerogen type,natural gas composition and carbon isotopic characteristics of the study area.The geochemical characteristics of the shale gas and the natural gas genesis of the Wufeng Formation and Longmaxi Formation in the basin and outside are discussed,and the main achievements and knowledge are obtained.The organic carbon content in the southeastern Chongqing is generally greater than2%,and the thermal evolution is high.It is in the mature stage and belongs to the dry gas.Organic type are type?kerogen,only a very small number of type?₁ kerogen.The target horizons are deposited in a reduced environment.The natural gas components in the Sichuan Basin are dominated by methane,and the non-hydrocarbons are mainly N₂ and dry gas.The carbon isotopes of alkanes show?¹³C₁>?¹³C₂,and the carbon isotope values of methane are positively correlated with the isotopic values of ethane.The difference is about 3‰.The shale gas in Longmaxi Formation in Longtan Formation is a mixture of different types of coal gas and Longmaxi Formation in Longtan Formation.The shale gas of Wufeng Formation is the oil type gas of the Longmaxi Formation and the oil type gas of Wufeng Formation mixing.The methane content of the natural gas component outside the Sichuan Basin is mainly methane,and the average content of N₂ is much larger than that of CO₂.Alkane gas carbon isotopes show that?¹³C₁>?¹³C₂ phenomenon.Ethane increases with the increase of methane isotope value,the gap between the two is about 4‰.The methane and ethane carbon isotopes in the Sichuan Basin are slightly heavier than the basin.The shale gas in the Wufeng Formation-Longmaixi Formation in the Sichuan Basin is the homologous different order mixed-source oil-bearing gas reservoirs of the Silurian source rock.