Pore-scale Simulations of Capillary Trapping of Supercritical CO2 after Multiple Drainage and Imbibition Cycles

Abstract:

Carbon capture and storage (CCS) of carbon dioxide emissions generated by production or combustion of fossil fuels is a technologically viable means to reduce the build-up of CO₂ in the atmosphere and oceans. On a fundamental level, capillary trapping of scCO₂ is a pore-scale process that shares mechanisms that are relevant, for example in oil recovery and remediation of NAPL-contaminated aquifers. Capillary trapping of scCO₂ differs rather significantly from trapping of oil recovery and NAPL remediation in that the goal is to maximize the amount of NWP storage, whereas the objective of the other applications is to minimize the amount of residual NWP. This difference makes research into capillary trapping of scCO₂ unique, but also complex because scCO₂ phase properties (e.g. viscosity, density, and interfacial tension) exhibit large shifts with pressure and temperature which can strongly alter the trapping potential and efficiency. In this presentation we compare direct pore-scale observations of the Brine-CO₂ drainage and imbibition process with lattice Boltzmann model simulations. The observations were conducted with the synchrotron-based x-ray microtomography facility at the Advanced Photon Source (APS) at Argonne National Laboratory using a novel x-ray compatible, high-pressure, elevated temperature setup. The “large” volumes (~1200 mm³; 6.3 mm diameter and 40 mm in length) were segmented into solid phase (Bentheimer Sandstone), Brine (KI, 1140 kg/m³) and scCO₂. We will present LB simulations of small (64^3 voxels) and large sections of the scanned cores with a simple Shan-Chen-type model and a more advanced Equation of State-type model and compare model results to pressure and CO₂ saturation levels that were observed for the CO₂ invasion and Brine re-imbibition process. We will present results for the smaller sections under multiple drainage and imbibition cycles to investigate whether this will lead to enhanced trapping of scCO₂ as found in earlier research.