Three-Dimensional Evaluation of Fault Sealing Capacity Based on Fault Attributes and Displacement Pressure Difference: Application to the K Area of the Pinghu Slope, Xihu Depression, East China Sea Shelf Basin

Faults may act either as preferential migration pathways or as effective sealing barriers during hydrocarbon accumulation. Therefore, robust evaluation of fault sealing capacity is critical for assessing trap integrity and reducing exploration risk in fault-controlled reservoirs. Conventional fault-sealing assessments are commonly restricted to two-dimensional cross-sections or single-point analyses, which are insufficient to represent the pronounced spatial heterogeneity and structural complexity of fault systems.To address these limitations, this study proposes a three-dimensional quantitative evaluation method for fault sealing capacity based on displacement pressure difference. Taking the K area gas field in the step-fault zone of the Pinghu Slope, Xihu Depression, as a case study, we integrate three-dimensional structural modeling with geological property modeling. Fault planes are discretized, and key controlling attributes—including in-situ stress, shale content, burial depth, and fault activity timing—are assigned to individual fault elements, allowing calculation of both fault rock displacement pressure and the displacement pressure of juxtaposed reservoirs in three-dimensional space. This framework enables simultaneous evaluation of vertical and lateral sealing capacities.The results indicate that faults within the P5 and P6 members of the Pinghu Formation exhibit relatively strong sealing capacity and constitute the principal sealing intervals in the study area, consistent with existing exploration outcomes. In addition, faults located adjacent to the depocenter generally display enhanced sealing capacity, highlighting favorable zones for future exploration. Compared with traditional fault-sealing evaluation methods, the proposed approach significantly improves spatial resolution and visualization of sealing capacity, enhances evaluation efficiency, and reduces the subjectivity inherent in point-based analyses. This method is therefore well suited for fine-scale characterization of fault-controlled hydrocarbon accumulation in structurally complex basins.

Keywords：Fault sealing capacity; Displacement pressure difference; Three-dimensional fault model; Xihu Depression