Coupled thermo-hydro-mechanical modelling of carbon dioxide sequestration in saline aquifers considering phase change

摘要

Carbon dioxide (CO2) sequestration in saline aquifers is considered to be one of the most viable measures to control its emissions. During the process of CO2 injection, phase changes of gas, liquid and supercritical CO2 will lead to changes in the density, dynamic viscosity, specific heat capacity and CO2 heat conductivity and solubility in water, which will influence the injection pressure and spatial distribution of CO2. To study the characteristics of injection pressure and spatial distribution of CO2 in saline aquifers, equations of state such as Peng-Robinson equation were used to realize the continuous calculation of the physical property parameters of gas, liquid and supercritical CO2. Based on the continuous physical property parameters, a fully thermo-hydro-mechanical (THM) coupled model was developed and then solved and verified using COMSOL Multiphysics software. It has been shown in this study that: (i) the predicted CO2 injection pressure by the THM coupled model is higher than that obtained from the uncoupled model; (ii) at the top boundary of the reservoir, the spatial distribution of CO2 can be divided into a rapid increase region, a slow decrease region, a rapid decrease region and an initial saturation region along the direction of CO2 migration and (iii) larger the reservoir geothermal gradient, more obvious is the gravity override effect.