Formation conditions and exploration prospects of Sinian large gas fields, Sichuan Basin

Exploration potential of natural gas in the Sinian, Sichuan Basin, is evaluated based on research on the evolution of the Leshan-Longnusi palaeouplift and reservoir forming conditions such as sedimentary facies, source rocks, reservoirs and caprocks. The Sinian has a potential to form large gas fields in the Sichuan Basin: (1) Large-scale inherited palaeo-uplift provided conditions for oil/gas formation and accumulation. (2) A stable sedimentary environment guaranteed the extensive development of source rocks and reservoirs. (3) Deng-2, Deng-3 and Deng-4 members overlap each other and are widely developed. (4) Multiple source rocks overlay each other vertically and are distributed widely, superimposed between reservoirs like "sandwiches". (5) The Sinian has good preservation conditions, regional mudstone cap rocks are thick and faults are not developed. Considering these favorable reservoir forming conditions, four favorable prospective areas were selected: Leshan-Longnusi Palaeouplift, Southeast Sichuan, East Sichuan, and Northwest Sichuan. Of them, the Leshan-Longnusi palaeo-uplift is the most favorable prospect, where the litho-stratigraphic gas reservoirs in the slope deserve further exploration.