Mechanism of Hydrocarbon Migration Along Fault Strike Controlled by Structural Ridges: A Case Study of the Pinghu Slope Belt, Xihu Sag

Migration of hydrocarbons along fault strike remains poorly understood, and its underlying mechanisms have not been fully clarified. Taking the Pinghu slope belt in the Xihu Sag, East China Sea Basin, as a case study, this study investigates the migration process, efficiency, and controlling factors of natural gas migration along fault strike using three-dimensional physical sandbox simulation experiments. The results show that: (1) under strong fault sealing conditions, hydrocarbons rarely migrate vertically across fault planes and instead preferentially migrate laterally along structural ridges developed on the hanging wall, forming stable migration pathways; (2) structural ridges serve as dominant conduits for efficient hydrocarbon transport, guiding hydrocarbons toward structurally elevated positions where accumulation and enrichment occur; and (3) the simulated migration patterns are consistent with exploration discoveries in the study area, where hydrocarbon accumulations are concentrated in ridge-controlled favorable zones. These findings indicate that the coupling between structural ridge development and fault sealing capacity is the key factor controlling hydrocarbon migration, accumulation, and enrichment in the Pinghu slope belt, providing theoretical support for hydrocarbon exploration in fault-controlled basins.