The Middle Silurian Hanjiadian Formation is a promising exploration target for hydrocarbon resources in the Sichuan Basin. Historically, research on this formation remains limited, leading to a poor understanding of its sequence stratigraphic architecture and internal sedimentary evolution, which in turn constrains hydrocarbon exploration. Using integrated outcrop, drilling, logging and seismic data, this study establishes a high-resolution sequence stratigraphic framework and a sedimentary filling evolution model for the Hanjiadian Formation guided by sedimentological and sequence stratigraphic principles. Three sequence boundaries are identified within the Hanjiadian Formation, and used to divide the formation into two third-order sequences (SQ1 and SQ2), within which four distinct systems tracts are recognized. A delta-shelf depositional system predominated during the deposition of the Hanjiadian Formation. Controlled by erosional processes and sequence boundaries, three subfacies are recognized in the study area: delta front (inner and outer fronts), prodelta, and argillaceous shelf. Longitudinally, the regressive systems tract of SQ1 (RST1) features the shallowest water depth and the most extensive delta-front sandbodies, creating a favorable interval for reservoir development. Taking systems tracts as fundamental units, the study analyzes sedimentary environmental evolution and sea-level changes via sequence stratigraphic correlation, and compares these results with coeval global sea-level fluctuations. Relative sea level in the Sichuan Basin during the Hanjiadian period underwent four cycles: deepening, shallowing, re-deepening, and re-shallowing. Finally, a sedimentary evolution model of the Hanjiadian Formation is proposed. This study provides important insights for hydrocarbon exploration and reservoir prediction of the Hanjiadian Formation in the Sichuan Basin.
Chen et al. (Mon,) studied this question.