Effects of supercritical CO2 injection on sandstone wettability and capillary trapping

Abstract The capture and storage of CO2 represent a technologically viable option to reduce greenhouse gas emissions from the use of fossil fuels. The petrophysical characteristics of the storage, the type of rock, the state of the gas and the conditions of the injection process affect the development of the residual trap mechanism. In the ATAP experimental facility, supercritical CO2 was injected following two methodologies, the steady and unsteady states into three sandstone samples with different porosities and permeabilities in a triaxial cell, which reproduces a rock-brine system. The results were obtained and interpreted based on numerical adjustment models, which were made with the Cydar ™ software in the first drainage process. The results indicate the alteration of the storage wettability, which suggests a greater affinity of the rock to SCCO2. The relative permeability curves obtained by history matching and successive iterations were analyzed with Craig’s rule and compared with the SCAL (Special Core Analysis) measurements. The SCCO2 injection increases the storage capacity because of its higher density, and the reservoir rock shows more affinity to CO2 in this phase. Nevertheless, during the imbibition process, the amount of CO2 retained by capillary trapping is lower than that in a more water-wet storage.