Abstract:

Triassic system is mainly distributed in Kuqa,Awat-Mangar depressions and locally in the north Tarim fault-block uplift.In the north part of Kuqa depression and the east part of Awat-Magar depression,Triassic sediments are found to be 2000m and 1250m thick respectively.Through a detailed investigation,the Triassic sediments revealed by wells of Yuecan-1,Shacan-1 and Acan-1 are termed the"Mangar Group"(Tmn).This group can be further divided into 3 formations and 7 sporo-pollen assemblages.Among them,dark rocks become thicker from west to east,accordingly their geochemical indices are more favourable for oil generation,and kerogen of which had reached low mature stage.Crude oil collected from well Shacan-2 contains Triassic sporopollon.Thus Triassic sediments in north Tarim are considerably important source rocks,and Mangar depression should be a favourable broad region for oil generation. The author suggests that north Tarim fault-block uplift located at the higher part between Kuqa and Awat-Mangar depressions,is favourable for oil accumulation and migration.Paleozoic anticlines existed in the fault-block uplift and in the northern margin of Awat-Mangar depression may be the hydrocarbon enrichment zones.