Well‐Seismic Diagnosis of Pore Pressure Variations in Near‐Normal Pressure Shale Gas Reservoirs

ABSTRACT Improving the understanding of shale gas reservoirs under near‐normal pressure conditions remains challenging because subtle pore pressure variations are difficult to detect yet can exert a first‐order influence on reservoir behavior. This study develops an integrated well‐seismic workflow to diagnose pore pressure variations and examine their relationship with shale gas performance in tight, heterogeneous reservoirs. Three pore pressure prediction approaches, including the equivalent depth, Eaton, and bulk modulus methods, were systematically evaluated, indicating that the bulk modulus method exhibits the highest sensitivity to low‐gradient pressure changes. High‐resolution acoustic impedance volumes were obtained through post‐stack sparse spike inversion and subsequently transformed into a three‐dimensional pore pressure model. Although the pressure coefficient varies within a narrow range of 0.98–1.12, the results reveal pronounced internal heterogeneity associated with lithofacies variation, fracture development, and fluid communication. Relatively higher pressure zones are characterized by improved porosity and elevated methane content, whereas fracture‐dominated intervals commonly display localized pressure dissipation and modified gas transport pathways. The observed positive relationship between pore pressure and well productivity highlights pore pressure as a key diagnostic parameter for identifying favorable intervals in near‐normal pressure shale gas systems. The proposed well‐seismic workflow provides a practical framework for reservoir characterization and performance evaluation in unconventional shale gas reservoirs and offers transferable insights for the assessment of normal‐pressure unconventional resources.