Source Rocks in the Junggar Basin, Northwestern China

Song Cao, Jie Tang

The Junggar Basin is the second largest sedimentary basin in northwestern China, covering an area of 130,000 sq. km. The sediments are dominated by non-marine Permian-Quaternary sequences with a maximum sediment thickness of about 12-15 km. Six sets of source rocks are developed in the basin: Carboniferous, Middle-Lower Permian, Upper Triassic, Middle-Lower Jurassic, Lower Cretaceous, and Lower Tertiary. The Carboniferous source rocks, characterized by deep water fine-grained sediments with high maturity and low TOC, are mainly distributed in the northwestern and northeastern margins. The permian source rocks are the main source rocks in the basin, consisting of lacustrine mudstone with a thickness ranging from 200 to 1500 m, covering anarea of about 56,000 sq. km. the Pe mian source rocks went into the "oil window" during the Jurassic time and enter the "gas window" during Cretaceous-Tertiary time. Most of the discovered oil and gas generated from the Permian source rocks. The Triassic source rocks are characterized by widely distributed lacustrine mudstone with a thickness ranging from 200 to 400 m, whose hydrocarbon generation areas are mainly located the southern and central parts of the basin. The Jurassic source rocks are dominated by widely distributed mudstone and coal with maturity varing in different parts of the basin. The Jurassic source rocks are the major source rocks for the gas resource in the basin. the Cretaceous source rocks are mainly developed in the southern mountain front. The Lower Tertiary source rocks are mainly developed in the southwest part of the basin.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995