Fault sealing evolution in complex fault zones of the Houxia Basin, China

Fault sealing capacity is controlled by present-day geometry and clay content, with current research focusing on enhancing the accuracy of capacity estimates. The mechanisms for evaluating both present-day and paleo-sealing are consistent, where the current sealing capacity representing the final stage in the evolutionary process of fault sealing. To address the limitations of the conventional shale gouge ratio ( SGR ) in evaluating the dynamic nature of fault sealing, this study proposes a visual model for fault sealing evolution. Fault sealing evolution is jointly controlled by the burial history and clay smear history and exerts a critical influence on hydrocarbon migration and accumulation. Hydrocarbon exploration data confirm that fault sealing during and after hydrocarbon migration critically impacts reservoir preservation. If faults remain unsealed during hydrocarbon migration and accumulation, they serve solely as conduits, with their present-day sealing capacity having limited impact. Effective fault sealing thus depends on the alignment between the evolutionary sealing stages and hydrocarbon activity. Building on this framework, we propose a method to visually and quantitatively characterize the fault sealing evolution alongside hydrocarbon activity. A case study of the Xishanyao Formation in the Houxia Basin highlights that the F4 fault transitioned from being over-open to sealed at the onset of hydrocarbon migration, thereby preserving the trap, while the F8-2 fault underwent a complete sealed–reopen cycle, with the late-stage reopening leading to an absence of hydrocarbon accumulation. This temporal contrast forms the basis for a new time-sensitive methodology for assessing fault-seal integrity in complex structural settings. • The effect of fault sealing capacity on hydrocarbon accumulation is investigated. • A fault evaluation framework is established using a triple-history coupling model. • Hydrocarbon preservation in the J 2 x 2 layer of the Houxia Basin was analyzed. • Persistent fault sealing constitutes an optimal sealing system.