Study on secondary migration of hydrocarbons in Tazhong area of Tarim Basin in terms of carbazole compounds

Fractionated carbazoles have been detected for the first time in crude oils from the Tazhong area of the Tarim Basin, and these nitrogen compounds were successfully utilized in the study of petroleum migration. Alkylcarbazoles are quite abundant in all the samples analyzed; small amounts of benzocarbazoles were detected only in some of the sample, and dibenzocarbazoles were not found in the oils. Based on the distributions of G1, G2 and G3 types of C2-alkylcarbazoles, the ratio of C3-/C2-carbazoles and the relative concentrations of alkylcarbazole and alkylbenzocarbazole, oils in the Carboniferous CIII reservoir in the Tazhong uplift are thought to have laterally migrated to the high level of Tazhong structure No. 4 from both northwest and southeast. The study here also shows that oils in the area may have undergone long-distance migration.