ABSTRACT
Carbon dioxide (CO2) is injected into the underground rock for a variety of purposes. It is often used for miscible flooding to enhance oil recovery in depleted petroleum reservoirs, and the use of CO2 as a fracturing fluid for well stimulation has been considered because it eliminates formation damage and residual fracturing fluid (Sinal & Lancaster 1987, Liao et al. 2009). Using CO2 as fracturing and circulating fluid has also been proposed in hot dry rock geothermal energy extraction, because it eliminates scaling in the surface piping due to the inability of CO2 to dissolve mineral species (Brown, 2000). Recently, since shale has a greater affinity for CO2 than methane (Nuttall et al. 2006), the CO2 injection to enhance shale gas recovery has been considered as well (Kalantari-Dahaghi 2010). For all of these purposes, it is necessary to understand the behavior of CO2 in rock. It is also important to know how injected CO2 infiltrate into the surrounding rock mass in CO2 capture and storage projects (Xue et al. 2006, Nooner et al. 2007).
