Abstract
In this study, a difference between mechanical properties of water saturated and CO2 injected mudstone were investigated. Triaxial experiments, which simulated pressure and temperature at 1000 m deep underground, were conducted under drained and undrained conditions. Specimen were taken from Otadai mudstone Formation which is thought to be suitable for a caprock of carbon dioxide capture and storage reservoir. Experimental results were analyzed using poroelastic theory. Results are summarized as follows. (1) Under the both drained and undrained condition, Young's modulus and Poisson ratio of CO2-injected specimens were smaller than that of water saturated specimens. Triaxial strength of CO2-injected specimens were slightly higher than that of water saturated specimen. (2) Mineral particles do not seem to be dissolved since no significant differences in mechanical properties were observed between CO2-injected and N2-injected specimens. (3) Peak stress of water saturated specimens became larger by higher pore pressure than that of CO2-injected specimens.
