Evaluate Hydraulic Fracturing Effectiveness by Combining Water Hammer Analysis and Unified Transient Analysis: A Case Study of Gulong Shale Oil

Summary Accurate evaluation of hydraulic-fracturing (HF) effectiveness in shale oil reservoirs remains challenging because of complex induced fracture networks and limited access to low-cost, high-resolution diagnostics. In this study, we present an integrated, data-driven workflow that combines water hammer analysis (WHA) and unified transient analysis (UTA) to quantify both stimulated fracture geometry and the production-contributing fracture surface area from routinely available shut-in pressure and production records. WHA interprets early-time shut-in pressure oscillations to infer fracture complexity and characteristic dimensions, while UTA uses superposition principle and slope analysis to estimate the effective fracture surface area during production. Field case study indicates that the fracture surface area estimated by WHA is less than half of that estimated by UTA*, indicating that a large fraction of the stimulated volume may not contribute to sustained flow. Correlating WHA and UTA results with logging data and operational parameters helps identify key drivers of fracture usage and provides actionable guidance to refine stimulation designs in data-limited shale plays. *Corrigendum uploaded 17 November 2025; see Supplementary Data section for details.