The eastern Sichuan area is a high and steep tectonic zone, with the Sichuan Basin experiencing three extensional and convergent tectonic cycles of the Nanhua to Early Paleozoic, the Late Palaeozoic to Triassic, and the Jurassic to Quaternary. It has obvious characteristics of bedding slipping and vertical stratification. Three structural layers（lower structural layer, middle structural layer, and upper structural layer）are identified based on the three detachment layers（Lower Cambrian, Lower Silurian, and Lower Triassic gypsum mudstone）. Under each detachment layer, independent hydrocarbon systems are formed around the respective effective hydrocarbon source rocks. The high and steep structures in eastern Sichuan are mainly formed in Indosinian period, developed in Yanshan Period, and reformed in Himalaya Period. Tectonic deformations of the eastern Sichuan high and steep structures are mainly characterized by “fault bending, wedge back-thrusting, and duplex”. The lower structural layer includes imbricate structure, duplex structure, and wedge back-thrust structure along the Lower Cambrian detachment layer; the middle structural layer includes fault bend fold, ramp structure, and back-thrust structure along the Lower Silurian detachment layer; the upper structural layer includes fault propagation fold, ramp structure, and back-thrust structure along the Lower Triassic detachment layer. The eastern Sichuan Basin is rich in natural gas and mainly concentrated in the middle structural layer. The characteristics of hydrocarbon accumulation include the lower structural layer Cambrian to Sinian dolomite and reef shoal zone in the high structural position of the inheriting low uplift; the middle structural layer Carboniferous dolomite and Silurian sandbody development zone in anticlinal area along unconformity surface; the middle structural layer Permian and Lower Triassic reef beaches and dolomite developed areas in the latent structural anticline and syncline. These potential oil and gas accumulation areas correspond to their favorable exploration directions.
Wu Xiaozhi Zhou Gang He Dengfa Wang Xiaojuan Guo Qiulin Zheng Min. Formation mechanism and natural gas accumulation of the high and steep structure in the eastern Sichuan Basin[J]. Chinese Journal of Geology, 2019, 54(4): 1100-1113.