Successful Delineation of a Deep Sour Gas Play in the NE Sichuan Basin: Puguang and More Recent Discoveries

Yongsheng Ma and Xunyu Cai
China Petrochemical Corporation, Exploration Company, Beijing, China

The recent discovery of the giant Puguang gasfield in northeastern Sichuan Basin, SW China resulted from the successful application of a new play concept and new technology in a mature basin. The field is a combination structural-stratigraphic trap closed by lateral depositional change and fault closure. The trap evolved from a paleo-oil reservoir originating in the Triassic-Jurassic. The entrapment of thermal gas, which was derived from Lower-middle Silurian and Permian source rocks, occurred during deep burial in the Jurassic-Cretaceous. Tertiary-Quaternary compression transformed the paleotrap into the present gas reservoir. Gas is contained in the Lower Triassic Feixianguan and the Upper Permian Changxing reservoirs, which consist predominantly of dolomitized oolites deposited in shelf and platform-margin shoal and backreef environments. Reservoir quality is characterized by porosity of 1-29% and permeability of 0.01-9664 md, with buried depth greater than 5000 m. The discovery has not only broadened the exploration scope in the Sichuan Basin, but also provided an excellent analog for exploration in other fold-thrust belts worldwide. This presentation will review the exploration history of the Sichuan Basin, discuss the key scientific and technological advances that have been achieved in the field discovery process, and provide an update on more recent exploration successes in this sour gas play following the initial discovery.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas