摘要
Based on the analysis of the geochemical characteristics of light hydrocarbon in natural gas in the middle member of the West Sichuan depression,the authors analyse the applications in studying the light hydrocarbon in the area.The features of C6 and C7 indicate that the natural gas is coal-related gas.The heptane and isoheptane qualitative analysis and the Mango quantity approach(Ro=0.83%~1.59%) show that this natural gas is mature and highly mature gas.The benzene/hexane and the benzene cyclohexane values show that the migration phases are the water-dissolving phase and separate phase.The water-dissolving phase strengthens with depth decreasing from T3x2 Formation to Middle Jurassic.The migration phase is a separate phase in sallow formations of Upper Jurassic and Cretaceous System.The correlation of natural gas and source rocks indicate that the natural gas in T3x2 Formation origins from T3x2 Formation source rocks,and the natural gas in T3x4 Formation mainly origins T3x4 Formation source rocks and some maybe derive from T3x5 Formation source rocks and seldom derive from T3x3 Formation source rock.The natural gas in Jurassic System and Cretaceous System mainly origins T3x5 Formation source rocks and some derives from T3x4 Formation source rocks.