Evolutions in the Elastic Constants of Ca-Montmorillonites with H2O/CO2 Mixture under Supercritical Carbon Dioxide Conditions

Clay mineral plays a crucial role in determining permeability and affecting mechanical properties of caprock formations in geologic carbon sequestration (GCS) and enhanced oil recovery (EOR) engineering. In the corresponding environment, CO2-H2O intercalation not only causes swelling or shrinkage of clay mineral but also results in affecting mechanical properties of mineral. However, influence of quantitative CO2/H2O adsorption on mechanical properties of clay still remains unknown. This work investigated evolutions of elastic properties of Ca-MMT with variable CO2-H2O component using molecular dynamic method. Elastic coefficients C-ij, bulk modulus K, shear modulus G, Young's modulus E-ii, and Poisson's ratio E-ij were correlated to qualified adsorption of CO2-H2O mixture. We obtained the following conclusions: (1) in-plane elastic constants, bulk modulus, shear modulus, and Young's modulus E-33 had distinct correlation with the profile of d(001) spacing as a function of H2O content at fixed CO2 content; (2) no distinct evolution profile was found in Poisson's ratio as a function of CO, or H2O content; (3) we revealed that the mixture of CO2/H2O caused decrease in strength of clay mineral; and (4) varying ranges of all elastic constant were summarized for day-CO2-H2O considered in this work.