Sedimentary Filling Evolution Controlled by Basin-mountain Coupling: a Case Study of the Xujiahe Formation in the Upper Triassic, Northeast Sichuan Basin

It is of great significance to clarify the sedimentary filling evolution process of the Xujiahe Formation in the Northeast Sichuan Basin for natural gas exploration. Employing well logs, cores, outcrops, and geological data, the characteristics of sedimentary facies and lithofacies within the Xujiahe Formation of the Northeast Sichuan Basin were examined. For sedimentary analysis, cores and outcrop observation is the most direct and efficient method, and the response relationship between logging and lithology can facilitate prediction of sedimentary facies. Additionally, the introduction of outcrops increases the accuracy and continuity of the prediction. As such, a feasible method for sedimentary microfacies analysis via the combination of well logs and cores is provided in the Xujiahe Formation. Influenced by the varying intensity of activity in the Longmen–Micang–Daba orogenic belt, the provenance within the study area exhibits three distinct directions: originating from Longmen orogenic belt, Micang orogenic belt, and Daba orogenic belt. The analysis results establish the response characteristics of sedimentary facies and logging curves in the study area, revealing the sedimentary filling process under tectonic control across different sedimentary periods of the basin, creating a model for the development of the basin. The results also show that the sedimentary filling evolution is controlled by the coupling control of the tectonic evolution of the basin and the activities of the surrounding orogenic belt, and the interaction between the two forms the palaeogeomorphologic pattern.