Influence of Mineralogy on Rock Mechanical Behaviour Considering Dynamic Alteration Damage Caused by SC-CO 2 : A Comparative Study on Different Rock Types

Currently, the inability to master the damage law of reservoir rock is one of the major obstacles to the efficient development of geological resources using supercritical carbon dioxide (SC-CO 2 ), and the key issue is the unknown influence mechanism of mineral dissolution on the altered reservoir strength. Therefore, the aim of this study was to reveal the influence mechanism of mineralogy on rock mechanical behaviour by conducting a SC-CO 2 dynamic alteration study. By analysing the correlation between mineral evolution and mechanical damage, the controlling effect of insoluble minerals on altered strength and the dominant effect of the highest reaction order minerals on damage rate were revealed. Under the dynamic alteration effect, the dissolution of soluble minerals is weakened and the spallation of insoluble minerals is promoted. An evaluation index, the ISR, was proposed to show significantly positive correlation with the altered strength, whose effect is similar to the content of insoluble minerals. A modification method for the alteration damage laws of different types of rocks was proposed, indicating that the mechanical damage should be considered more severe for sandstone and granite, and slighter for marble. On this basis, the mineral characteristics of the rocks, which can be severely damaged under SC-CO 2 alteration, are preliminarily proposed.