Experimental study of temperature and pressure effects on rock damage caused by SC-CO2

Abstract

While high-efficiently developing hot dry rock (HDR), supercritical carbon dioxide (SC-CO2) can cause mechanical damage to reservoir rocks by chemical alteration reactions. Accurately mastering the rock damage phenomena under different temperature and pressure is critical to directionally develop HDR in different reservoir environments. The interaction test between SC-CO2 and rocks was performed under different temperature and pressure. By controlling the liquid environment to flow or not, the interaction test was divided into dynamic and static alteration tests to comparatively study the effect of flowing liquid on mechanical damage and chemical reactions. With pressure increasing, mechanical damage and chemical reactions both grow more severe. With temperature increasing, sandstone and granite are more severely damaged, while marble is insignificantly affected. Most reactions of rock forming minerals are catalyzed, while that of calcite is inhibited. Considering dynamic alteration effect, the damage to sandstone and marble is more severe, while that to marble is slighter. The reactions of insoluble minerals are enhanced, while those of soluble minerals are weakened. The basic reason for the differential performance of temperature effect is the activation energy Ea of different minerals. With temperature increasing, the reaction rate of minerals with low Ea significantly decreases, while that of minerals with high Ea increases. In addition, a damage variable Dξ was established based on chemical kinetics method, showing high applicability for the rocks with insoluble mineral skeletons.