Effective Wettability Measurements of CO2-brine-Sandstone System at Different Reservoir Conditions

Abstract

Abstract The wetting properties of CO2-brine-rock systems will have a major impact on the management of CO 2 injection processes. The wettability of a system controls the flow and trapping efficiency during the storage of CO 2 in geological formations as well as the efficiency of enhanced oil recovery operations. While recent studies have shown CO 2 to generally act as a non-wetting phase in siliciclastic rocks, some observations report that the contact angle varies with pressure, temperature and water salinity. Additionally, there is a wide range of reported contact angles for this system, from strongly to weakly water-wet. In the case of some minerals, intermediate wet contact angles have been observed. Uncertainty with regard to the wetting properties of CO2-brine systems is currently one of the remaining major unresolved issues with regards to reservoir management of CO 2 storage. In this study, we make semi-dynamic capillary pressure measurements of supercritical CO 2 and brine at reservoir conditions to observe shifts in the wetting properties. We utilize core analysis techniques to evaluate core-scale effective wetting properties mainly by comparing the capillarity at different conditions on the same rock. We evaluate wettability variation within a single rock with temperature, pressure, and salinity across a range of conditions relevant to subsurface CO 2 storage. This paper will include the initial results of measurements in a Berea sandstone sample across a wide range of conditions representative of subsurface reservoirs suitable for CO 2 storage (5-20 MPa, 25-50 oC, 0-5 mol kg-1). The measurement uses X-ray CT imaging in a state of the art core flooding laboratory designed to operate at high temperature, pressure, and concentrated brines.