Tectonic features of Gaoshiti-Moxi paleo-uplift and its controls on the formation of a giant gas field, Sichuan Basin, SW China

Abstract

Based on the latest geological, seismic, drilling and outcrop data in the Sichuan Basin, the geological structure and evolution history of Gaoshiti-Moxi paleo-uplift was studied to find out controlling factors of the Sinian-Cambrian Anyue giant gas field. The Gaoshiti-Moxi paleo-uplift is an N-S trending syndepositional paleo-uplift related to the Tongwan movement. The top of Sinian Dengying Formation and adjacent strata in the central part of the paleo-uplift, namely the Gaoshiti-Moxi Area, has remained in the relatively high position since the Sinian, and a giant trap structure is developed independently in the area, which is different from Caledonian Leshan-Longnüsi paleo-uplift in development time, geological structure and evolution history. The Gaoshiti-Moxi paleo-uplift controls the development and distribution of the Sinian-Cambrian Anyue giant gas field, which is shown in the following aspects: (1) The western part of the paleo-uplift is adjacent to the source rock center of Cambrian Maidiping and Qiongzhusi Formations in Mianzhu-Changning intracratonic taphrogenic trough, and the source rocks of Sinian Dengying Formation and Cambrian Qiongzhusi Formation also occur in the Gaoshiti-Moxi paleo-uplift itself; (2) the paleo-uplift controls the formation and distribution of the high-quality reservoirs of the fourth and second members of Sinian Dengying Formation and Cambrian Longwangmiao Formation; and (3) there develop 3 sets of reservoir-seal assemblages which provide favorable conditions for the formation of the giant gas pool from in-situ cracking of paleo-oil reservoirs in the Sinian-Cambrian. Key words: Sichuan Basin, Gaoshiti-Moxi paleo-uplift, syndepositional paleo-uplift, tectonic feature, paleo-oil reservoir in-situ cracking