Dynamic Deliverability Prediction for High-Temperature High-Pressure Gas Reservoirs Incorporating Time-Varying Fluid-Rock Parameters

Productivity prediction in high-temperature, high-pressure (HTHP) gas reservoirs is complicated by the strong coupling between stress-sensitive rock properties and pressure-dependent real-gas behavior during reservoir depletion. Conventional deliverability models that generally assume constant permeability and fluid properties are therefore inadequate for accurately characterizing such systems. In this study, a dynamic deliverability prediction method is developed by extending the classical Laminar-Inertial-Turbulent (LIT) inflow equation, with model coefficients continuously updated to reflect the coupled evolution of stress-sensitive permeability and real-gas pressure–volume–temperature properties. Core experiments conducted under reservoir-representative conditions (53 MPa and 138 °C) show that permeability degradation is better described by a power-law model ( R 2 = 0.928). High pressure–volume–temperature experiments and correlation evaluation indicate that the Shell and LGE models provide the most accurate predictions of gas deviation factor and viscosity ( R 2 > 0.98). The proposed model has been further validated against real-gas systems, and field application to six HTHP gas wells over a ten-year production period demonstrates that the proposed dynamic method accurately reproduces the observed decline in absolute open-flow potential, with an overall average absolute relative error of 8.07%. By retaining the analytical simplicity of the LIT equation while embedding stress-sensitive geomechanics and real-gas thermodynamics, the approach offers a practical tool for long-term productivity forecasting and development optimization in HTHP gas systems.