The Sichuan basin, southwest China: a late proterozoic (Sinian) petroleum province

Abstract

Abstract The Sichuan Basin in southwest China is a large intracratonic sedimentary basin which first subsided in the Late Proterozoic (Sinian). The basin has had a long, complex subsidence history that has continued through to the present day. Tectonic subsidence curves indicate that, in its early history, the basin developed as a complicated extensional basin whose subsidence and tectonic history was polyphase. Much of the subsidence was driven by pulses of extension followed by thermal relaxation of the lithosphere. The Sichuan Basin is an important petroleum base for the People's Republic of China because of the discovery and development of over 60 gas fields and 10 oil fields. One of the fields is the large Weiyuan Gas Field which is considered to be both sourced and reservoired in Late Proterozoic sedimentary rocks. These rocks are the Late Sinian carbonates of the Dengying Formation which form part of a thick platform (Yangtze Platform) succession that was deposited from the Sinian to the Silurian. The Weiyuan Gas Field occurs in a large anticlinal structure 53 × 26 km (850 km2) of which 200 km2 is prospective for gas. Up until 1988, 91 wells had been drilled in the field and 40 were in production. Production is approximately 800,000 m3/day (28.3 million cubic feet/day), with total production to 1987 being 13.6 billion m3 (480 billion cubic feet). Total reserves in the Weiyuan Gas Field are estimated at 30–40 billon m3 (1060–1410 billion cubic feet). The Sinian and earliest Cambrian succession in the Sichuan Basin is highly prospective for the discovery of additional reserves of natural gas.