Petroleum Basins of Western China

Gregory Ulmishek

Eleven productive or potentially productive basins are recognized in western China. Despite their differences in size and geologic framework, these basins have important common features: (1) their Mesozoic-Cenozoic sequences are composed of essentially continental rocks, and (2) they experienced predominantly compressional stress during the late stages of their geologic history. Four of the basins have established commercial production; oil and/or gas shows are present in most other basins. The most probable amounts of undiscovered resources in all basins are estimated at 19.5 billion bbl of oil and 78 tcf of gas, about 90% of these resources are in the Tarim, Zhungaer, and Chaidamu basins.

The Tarim basin is situated on the Precambrian median massif (plate). Both carbonate Paleozoic and clastic Mesozoic-Cenozoic rocks are productive. Proved source rocks are lacustrine and swamp facies of Late Triassic-Middle Jurassic age; marine source rocks in the Carboniferous section may also be present. Promising exploration plays are located in the Southwest and East Tarim depressions and on the North Tarim uplift.

The Zhungaer basin also occupies the median massif. Oil source rocks are Upper Permian lacustrine black shales, Carboniferous marine shales, and Jurassic coal measures. Major reserves are concentrated in the Karamay overthrust belt. This area and the Sangequan uplift are most valuable for exploration.

The Chaidamu basin apparently consists of three graben rifts of Mesozoic, Tertiary, and Quaternary age. Source rocks are abundant, but reservoirs are of poor quality. Sixteen oil and gas fields are found in anticlinal structures. Analogous traps in the Mangya depression constitute the major exploration play.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.