Abstract:

It is universal that both the anaerobic bacterial degradation and oxidative bacterial degradation of crude oil exist in the hydrocarbon evelution.They do not only distroy some hydrocarbons,but also reproduce some new hydrocarbons,and even result in new hydrocarbon pools for exploration.A lot of shallow transitional gas pools actually resulted from anaerobic degradation.The products of the anaerobic bacterial degradation of crude oil possess light methane carbon isotope(δ¹³C₁<-5.5%),very light ethane carbon isotope (δ¹³C₂<-4.0%)and the negative anomaly of carbon isotope of separate hydrocarbons (δ¹³C_n<-3.7%～-5.3%).Natural gas produced in central Tarim Basin contains at least 20% bacterial degrated methane.