Abstract:

Geochemical analysis of different degrees of biodegradated crude oils show that a slight biodegration affects little to the pyrrolic nitrogen compounds in the oils. The concentrations of cathazole, methylcarbazole and C₂-carbazole decrease with the increasing of the biodegradation for mid-degree biodegraded oils, the concentrations of pyrrolic nitrogen compounds sharply decrease in the heavily biodegraded oils. The relative concentrations of carbazole, methylcarbazole and C₂ carbazole do not show any apparent changes in the non-heavly biodegraded oils; in the heavilybiedegraded oils, the concentrations of carbazole and methylcarbazole decrease, but that of the C₂-carbazole increases.As the C₂-carbazole isomers, the relative Percentage contents of the pyrolic N-H shielded, the prplic N-H semishielded and the pyrolic N-H-exposed carbazoles do not display any obvious variation in the non-heavily biodegraded crude oils, but that of the pyrrolic N-H-exposed carbazoles increase and that of the pyrrolic N-H semi-shielded carbazoles decrease in the heavily biodgraded oils.

Key words: crude oil, biogradation, carbazole, benzene-carbazole, Liaohe Basin