Enhancing residual trapping of supercritical CO2 via cyclic injections

We utilize synchrotron X-ray tomographic imaging to investigate the pore-scale characteristics and residual trapping of supercritical CO2 (scCO(2)) over the course of multiple drainage-imbibition (D-I) cycles in Bentheimer sandstone cores. Capillary pressure measurements are paired with X-ray image-derived saturation and connectivity metrics which describe the extent of drainage and subsequent residual (end of imbibition) scCO(2) trapping. For the first D-I cycle, residual scCO(2) trapping is suppressed due to high imbibition capillary number (Ca approximate to 10(-6)); however, residual scCO(2) trapping dramatically increases for subsequent D-I cycles carried out at the same Ca value. This behavior is not predicted by conventional multiphase trapping theory. The magnitude of scCO(2) trapping increase is hysteretic and depends on the relative extent of the sequential drainage processes. The hysteretic pore-scale behavior of the scCO(2)-brine-sandstone system observed in this study suggests that cyclic multiphase flow could potentially be used to increase scCO(2) trapping for sequestration applications.