Abstract:In order to determine the seismic facies and sedimentary characteristics of the Changxing Formation in the Yilong-Pingchang area of Sichuan Basin, this work employed comprehensive analytical techniques involving seismic lithology and seismic geomorphology, and integrated well data, seismic data, and three-dimensional identification of reef bodies to determine the distribution patterns of reef beach reservoirs within the Changxing Formation. The results indicate that the Changxing Formation in the Yilong-Pingchang area develops four sedimentary zones. Among them, the open platform facies corresponds to parallel-subparallel sheeted moderately weak and intermittent seismic facies. The platform marginal facies corresponds to parallel-subparallel mound or lens-shaped moderate-weak seismic facies. The platform foreslope facies corresponds to sheeted foreset weak seismic facies. The marine basin facies corresponds to parallel-subparallel sheeted medium-strong seismic facies, which can be subdivided into subfacies of platform margin reef, intra-platform reef and intra-platform shoal. The 30 Hz amplitude tuning body slice reveals that the shoreline of the basin is distributed in a northwest direction, while the 25 Hz amplitude tuning body slice has a clear response to the reef bodies in the platform margin, intra-platform reef, and intra-platform shoal subfacies in the west side of the basin. The planar distribution and development scale of biological reefs and shoals were controlled by the ancient geomorphic morphology of high in the southwest and low in the northeast during the sedimentary period of the Changxing Formation. The favorable areas for the growth and development of platform margin reefs are two rows of northwest-trending belts in the platform facies.
