Distribution pattern and main controlling factors of Paleozoic giant- and medium-sized gas fields of the Sichuan super gas basin in Southwest China

Sichuan Basin is the super gas basin with the most abundant natural gas resources in China, but the exploration degree of natural gas is relatively low. For providing theoretical support of the next exploration, combined with the exploration history of typical gas fields in the Sichuan Basin, and the analysis of oil-gas systems and multi-stage structural evolution, we analyze the enrichment and distribution and main control factors of large sized gas fields in the Paleozoic in the Sichuan Basin, which reveals the huge exploration potential of natural gas resources in the Sichuan Basin. Results show that the Sichuan Basin contains three super petroleum systems: the Lower Cambrian Qiongzhusi Formation, the Wufeng Formation-Longmaxi Formation, and the Upper Permian Longtan Formation/ Wujiaping Formation, and their demonstrated reserves account for 17.55%, 41.30% and 12.53% of the total demonstrated reserves in the Sichuan Basin respectively. 20 giant-sized gas fields (The proven in-place gas reserves of natural gas exceed 1 000×108 m3), 14 large-sized gas fields (The proven in-place gas reserves of natural gas range from 300×108 m3-1 000×108 m3) and 20 medium-sized gas fields (The proven in-place gas reserves of natural gas range from 100×108 m3-300×108 m3) have been discovered in the basin. The demonstrated reserves of natural gas in the giant-sized gas fields account for 85.5% of the total proven in-place gas reserves. The tectonic and sedimentary differentiation of the Paleozoic large-scale uplift-depression pattern controls the sedimentary characteristics of three sets of high-quality source rocks in the Sichuan Basin (Qiongzhusi Formation、Wufeng-Longmaxi Formation and Longtan/ Wujiaping Formation). The conclusion is that the evolution of continental basins since the Late Triassic, the Middle-Late Triassic to the Early-Middle Jurassic is the key reservoir forming period for the three major super petroleum systems. The Sinian to Lower Paleozoic around the Mianyang-Changning intracratonic sags, the Permian-Triassic around the Kaijiang-Liangping trough and Pengxi-Wusheng trough, and the shale gas of Wufeng Formation-Longmaxi Formation in Southeast Sichuan have become exploration areas of the three trillion gas field. © 2024 Natural Gas Industry Journal Agency. All rights reserved.