Effect of Anisotropic Rock Compaction on Unconventional Well Performance

Unconventional hydrocarbon reservoirs, particularly shale, exhibit stress-dependent flow properties like permeability and porosity, which are traditionally measured by applying confining stresses on core plugs. This study aims to investigate the impact of anisotropic stress conditions on the flow properties (permeability and porosity) of unconventional reservoirs, specifically shale, and their subsequent effect on well performance and recovery estimation. An advanced laboratory procedure was employed, applying tri-axial anisotropic stresses to shale samples to measure stress-dependent permeability and porosity. Dynamic simulations, based on these lab measurements, were used to assess the effect of varying stress conditions on well performance. The simulations focused on rock composition, particularly organic matter content, and its influence on permeability decline and rock compressibility. The workflow aimed to predict well performance under varying stress regimes including vertical and horizontal anisotropic stresses. The laboratory results confirmed significant stress dependence in shale permeability and porosity, with pore size reduction observed under high net stress. Numerical simulations, incorporating these stress-dependent properties, indicated a substantial impact on reservoir performance. Variations in flow properties, driven by stress anisotropy, led to considerable differences in well performance predictions. Simulation results highlighted that ignoring the stress sensitivity of shale's flow properties could lead to inaccurate performance forecasts. By integrating lab data with numerical models, the study showed that incorporating anisotropic stress conditions improves the accuracy of production forecasting, offering more reliable insights into well recovery and performance. This study introduces a comprehensive integration of advanced lab measurements with numerical simulations to model the impact of anisotropic stress-dependent permeability and porosity on unconventional reservoir performance, providing new insights into more accurate well performance and recovery predictions.