Structural architecture and sedimentary facies models of the Dengying Formation platform margin belts along the flanks of the Deyang-Anyue rift trough, Sichuan Basin

The platform margin belts of the Dengying Formation flanking the Deyang-Anyue rift trough represent a critical frontier for natural gas exploration and development in the Sichuan Basin. While giant gas fields, such as Anyue and Penglai, have been discovered along the eastern margin, the sedimentary characteristics of the western margin and the architectural disparities between the two flanks remain poorly understood, thereby constraining further exploration efforts in the region. By integrating core descriptions, well logs, and 3D seismic data, we systematically characterize the development of the Dengying Formation platform margins on both sides of the trough. Lithofacies paleogeographic maps were reconstructed for key intervals, and refined sedimentary facies models were established for the dual-flank system. As indicated by the research results (1) During the Late Sinian deposition of the Dengying Formation, the platform margins on both flanks primarily consisted of microbial mound, shoal, and mound-shoal complex facies, along with inter-mound/shoal subfacies, whereas the trough interior was dominated by slope-to-basin facies. (2) Distinct heterogeneities exist in the development and evolution of the platform margins. The eastern margin, controlled by basement faults, exhibits a steeply dipping, vertically stacked architecture with minimal lateral migration. In contrast, the western margin is characterized by multi-stage, gently sloping geometries with significant lateral migration distances. (3) Lithofacies paleogeographic mapping reveals substantial spatial variations in platform margin distribution between the second (Deng 2) and fourth (Deng 4) members of the Dengying Formation. During the Deng-2 period, the platform margin followed a quasi-circular distribution along the Chengdu-Suining-Zizhong trend. During the Deng-4 period, the platform margins expanded significantly, with the western margin trending NS along the Hongya-Jingyan-Zigong area and the eastern margin extending NS along the YantingSuining-Moxi area. Overall, the Deyang-Anyue rift trough is characterized by a “steep-east vs. gentle-west” and “single-stage-east vs. multi-stage-west” sedimentary facies model.