抄録
The genetic relationship between slope-break zones and gravity-sliding structures and their integrated control on hydrocarbon trap formation remains poorly constrained in foreland basin successions. Using the fourth and fifth members of the Upper Triassic Xujiahe Formation in the central–western Sichuan Basin as a case study, this study investigates the evolutionary mechanisms of slope-break zones and gravity-sliding structures and their coupling effects on sedimentation, reservoir architecture, and hydrocarbon accumulation. An integrated workflow combining seismic interpretation, drilling, core analyses, and granular-flow numerical simulations was employed to characterize structural evolution and trap development. The results demonstrate that fault-controlled slope-break zones promoted the development of gravity-sliding structural systems characterized by frontal compression and rear extension, which exerted first-order controls on stratigraphic thickness, sandbody architecture, reservoir quality, and trap configuration. Two distinct hydrocarbon trap types were identified. The first comprises synsedimentary anticlinal sandbodies developed in gentle-slope settings through extensional deformation, forming laterally sourced and laterally trapped reservoirs adjacent to organic-rich mudstones. The second consists of gravity-sliding-induced synsedimentary anticlines developed along steep slope-break zones, where lateral and vertical sealing by mudstones facilitated hydrocarbon migration and accumulation within source-bearing intervals. These findings demonstrate that the coupled evolution of slope-break zones and gravity-sliding structures constitutes a fundamental control on hydrocarbon trap development in the Xujiahe Formation. The proposed coupling framework and associated trap models provide a new genetic basis for predicting structural–stratigraphic traps in foreland basins and analogous sedimentary systems.
