Modeling of sorption-induced strain and stress in anisotropic permeability models

Abstract

This study investigates the dynamic coupling of sorption-induced strain and stress in anisotropic permeability models for deformable dual-porosity porous media, focusing on the impact of gas injection and production dynamics. The analysis is conducted at two monitoring wells: well I (injection) and well II (production), with CO2/N2 as the injection gas mixture. Quantitative results show that in well I, permeability decreases significantly, with a 14% reduction in the z-direction at low elastic modulus reduction coefficient values (Rmz = 0.0). In contrast, well II exhibits a permeability increase in up to 8% in the z-direction under similar conditions. The elastic modulus coefficient plays a critical role, as higher values reduce permeability loss in well I and limit the increase in permeability in well II. Internal swelling coefficients also demonstrate a strong impact, with variations leading to notable changes in permeability evolution across all three axes (x, y, and z). Stress-induced strain is identified as the dominant factor in porosity changes, accounting for 45% of the total variation in well I and 25% in well II. CO2 adsorption is the next most influential factor, contributing 30% in well I and 20% in well II, while N2 adsorption has a relatively smaller effect. Methane desorption significantly impacts well II, contributing 30% to porosity reduction. These findings emphasize the critical role of stress–strain interactions and sorption effects in controlling permeability evolution, offering valuable insights for optimizing gas injection strategies in enhanced coalbed methane recovery.