Enhancing residual trapping of supercritical CO2 via cyclic injections

• Published in: Geophysical research letters Vol. 43; no. 18; pp. 9677 - 9685
• Main Authors: Herring, Anna L., Andersson, Linnéa, Wildenschild, Dorthe
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.09.2016
• Subjects: Brines; Capillary pressure; capillary trapping; Carbon dioxide; CO2 sequestration; Cores; Cycles; cyclic injections; Drainage; Drainage systems; Hysteresis; Imaging; Imaging techniques; Imbibition; Multiphase flow; Pressure; Pressure measurement; residual trapping; Saline water; Sandstone; Saturation; Sedimentary rocks; Trapping; X-rays; X‐ray microtomography
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL070304

We utilize synchrotron X‐ray tomographic imaging to investigate the pore‐scale characteristics and residual trapping of supercritical CO2 (scCO2) 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) scCO2 trapping. For the first D‐I cycle, residual scCO2 trapping is suppressed due to high imbibition capillary number (Ca ≈ 10−6); however, residual scCO2 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 scCO2 trapping increase is hysteretic and depends on the relative extent of the sequential drainage processes. The hysteretic pore‐scale behavior of the scCO2‐brine‐sandstone system observed in this study suggests that cyclic multiphase flow could potentially be used to increase scCO2 trapping for sequestration applications. Key Points We observe cyclic pore‐scale behavior of supercritical CO2 (scCO2) via synchrotron X‐ray microtomography Residual scCO2 saturation increases over multiple drainage‐imbibition (D‐I) cycles reaching a value of 50% after three cycles The ultimate driver for this behavior may be a combination of cycling and associated surface chemistry reactions