Development of a laboratory-scale numerical model to simulate the mechanical behaviour of deep saline reservoir rocks under varying salinity conditions in uniaxial and triaxial test environments

The proposed numerical model based on the stiffness degradation mechanism of reservoir rock can accurately simulate salinity-dependent stress-strain behaviour under any stress environment (uniaxial/triaxial). According to the model, both pore fluid salinity and confining stress add additional strength to the reservoir rock mass due to NaCl crystallization and pore shrinkage. Importantly, the model clearly shows a reduction of the effect of pore fluid salinity on reservoir rock strength characteristics with increasing reservoir depth or confinement, mostly due to the more significant effective stress at such extreme depths. This provides an important finding on CO2 sequestration in saline aquifers: salinity-dependent strength alteration is not very important for extremely deep aquifers compared to shallow aquifers. Although this model has the capability to simulate the failure of reservoir rock under extreme pressure conditions, the simulation results show a small fluctuation near the post-peak stage due to the complexity of the damage mechanism caused by strain localization.