ABSTRACT: Evolution and Petroleum Potential of the Sichuan Basin, Southwest China

KORSCH, R. J., Bureau of Mineral Resources, Canberra, Australia, J. D. GORTER, Pty. Limited, Perth, Australia, MAI HUAZHAO and SUN ZHAOCAI, Central Laboratories of Petroleum Geology, Ministry of Geology and Mineral Resources, Wuxi, Jiangsu, China

The Sichuan basin, southwest China, is a large intracratonic basin that commenced subsiding in the Late Proterozoic (Sinian) and has had a long subsidence history continuing to the Cretaceous. The subsidence initially was driven by extension, with the formation of a widespread carbonate platform during the Sinian to Silurian. During the Devonian and Carboniferous sediments were only deposited around the rim of the present basin. From the Late Permian, a series of foreland-loading events drove the subsidence, and sedimentation was dominated initially by marine carbonates and from the Late Triassic by fluvial to lacustrine clastics. The present northwest margin of the basin is the Longmenshan, which is an active thrust front forming part of the Cenozoic Himalayan system. The basin is a ajor producer of gas. ks exploration history began as long ago as 221 BC when boreholes over 300 m deep were drilled into evaporites using bamboo rods hardened in saltwater, natural gas from the holes was used to extract salt from the brines. Modern exploration commenced only in 1949. There are now over 70 producing gas and oil fields and the basin is considered highly prospective, particularly for additional large reserves of natural gas. The main exploration plays are Sinian to Triassic marine carbonates with interbedded source rocks and reservoirs; fractured Sinian and Early Paleozoic carbonates, Carboniferous erosional carbonate reservoirs and Permian reefs form some of the most important oil and gas bearing horizons in the basin. Also, oil has been found in Jurassic non-marine sands ones in the central part, and gas Triassic sediments in most parts of the basin.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)