| Based on the outcrop and drilling data, we reconstructed the Ordovician lithofacies paleogeography map in Sichuan Basin with a method of single-factor analysis and multi-factor comprehensive mapping. There developed coastal facies, alluvial tidal flat facies, limited platform facies, open platform facies and slope-basin facies from west to east. According to the hydrocarbon source conditions, Late Ordovician Wufeng Formation developed in limited sea is high-quality source rocks, in addition, when connected by faults, the overlying Silurian Longmaxi Formation and the underlying Lower Cambrian Qiongzhusi Formation are effective source rocks. According to the reservoir conditions, dolomitization, supergene dissolution, and fracture development are the key factors for the formation of Ordovician carbonate reservoirs. Correspondingly, three types of reservoirs developed including particle-gravel dolomite reservoir, karst reservoir in Tongzi Formation and Honghuayuan Formation, and crack reservoir in Baota Formation. The Ordovician developed two sets of reservoir assemblages, i.e., the lower part and the upper part, which have good exploration potential. |
