Sorption Behavior of CO₂ on Rocks and Minerals in CO₂ Rich Dense Phase

Abstract

Evaluation of CO₂ storage capacity in water saturated reservoir rocks is very complex because various trapping mechanisms that act at different rates are involved and, at times, all mechanisms may be operating simultaneously. Thus, in terms of the water saturated reservoir rocks, a reliable estimate of CO₂ storage capacity requires a thorough understanding of the mechanisms of CO₂ trapping in this system.
The objective of this study is to provide a fundamental knowledge about interactions among CO₂, water and rock, and contributes to development of standards for CO₂ storage capacity estimation in the water saturated reservoir rocks. In this experiment, CO₂ sorption was measured for rock samples (quartzose arenite, greywacke, shale, granite and serpentine) , and mineral samples (quartz and albite) in a CO₂ rich dense phase at 50ºC and 100ºC, and pressures up to 20MPa, the condition of which is expected to occur mostly during CO₂ injection into pores of the water saturated reservoir rocks. The result obtained from the experiment exhibited a significant sorption capacity of CO₂ on all of the samples. At 50ºC and 100ºC, quartzose arenite indicated largest sorption capacity among the other samples in higher pressures (>10 MPa) . Furthermore, comparison with model prediction based on the pore filling model, which assumed that pores of the rocks and minerals will be filled with CO₂, suggested the importance of the sorption mechanism in the CO₂ geological storage in addition to the pore-filling mechanism.
The present results indicate that the sorption process may have significant and meaningful effect on the assessment of CO₂ storage capacity in geological media.