Paleogeomorphology restoration of Wufeng Formation-Lower Member of Longmaxi Formation in Zigong area of Sichuan Province and its oil and gas significance

The Weiyuan-Zigong area is a main shale gas production area in the Sichuan Basin. The distribution of the Upper Ordovician Guanyinqiao Member provides significant guidance for shale gas exploration. Tectonic-sedimentary background analysis combined with core, thin section, paleontology, logging, deposition rate and carbon-oxygen isotope data were used to interpret the micro-paleogeomorphology of the Zigong area in the Hirnantian-Rhuddanian period. The Guanyinqiao Member comprises shell limestone deposited under the background of regression in the tectonic stabilization period. The Guanyinqiao Member was missing and the Wufeng Formation was thin in wells A205 and A1. The NE-SW-directed Zigong low uplift identified in wells A1 and A205. A sedimentary evolution model of the Zigong area during the Hirnantian-Rhuddanian period was established, and its influence on black shale thickness was clarified. The Wufeng Formation and the high gamma ray value section of Longmaxi Formation thickened around wells A1 and A205. Both sides of the Zigong low uplift are favorable for exploration.