Stress-Dependent Permeability: Characterization and Modeling

Abstract

Summary During the production life cycle of a reservoir, absolute permeability can change in response to an increase in the net effective stress. This paper focuses on stress-dependent permeability in unconsolidated, high-porosity sand reservoirs (offshore turbidites) and moderate-to low-porosity consolidated reservoirs, including tight-gas sands. Specifically we address fundamental controls on stress-dependent permeability, rock-based log modeling of stressdependent permeability in cored and noncored wells, and, finally, implications for production rates and recovery volume based on data from reservoir simulation. Results demonstrate that the rate of reduction in permeability with an increase in stress is a function of the pore geometry in both consolidated and unconsolidated sand reservoirs. A practical, rapid, and cost-efficient methodology is presented to improve evaluation and enhance the productivity and management of stress-dependent reservoirs. Several cases are presented of a conceptual, single-well model of an overpressured, tight-gas sandstone reservoir that include stress-dependent permeability. Results of simulation analyses for varying conditions of reservoir stress demonstrate the importance of stress-dependent permeability in more accurate forecasting of reserves and predicting optimum wellbore-producing conditions.