Rapid Determination of Supercritical CO2 and Brine Relative Permeability using an Unsteady-State Flow Method

Abstract Relative permeability of supercritical CO2 (scCO2) and brine was determined in reactive and non-reactive rock cores using a combination of unsteady-state methodology and computed tomography. Experiments were conducted using a medical grade CT scanner to determine saturation using a custom Python script. The saturation and differential pressure across the core were then used to derive four empirical constants to calculate relative permeability. This methodology increases temporal efficiency while reducing experimental complexity. Additionally, we show that the method can be used to determine scCO2 relative permeability in a wide range of lithologies and flow rates, and with the ability to account for matrix dissolution during scCO2 flooding. Plain Language Summary : The ability to capture and store carbon dioxide (CO2) is an important component of efforts to slow climate change. Long-term geologic storage of CO2 requires accurate descriptions of injected CO2 in subsurface rock formations to account for stored volumes and develop adequate risk monitoring. Effectively describing the migration of CO2 injected in underground reservoirs requires an accurate description of how CO2 moves and interacts with the rock. Relative permeability, or the description of how efficiently a fluid moves in a porous media while in the presence of other fluids, is the most utilized tool for describing the competitive flow of fluids. In this study, we detail a modified unsteady-state methodology using computed tomography that provides relative permeability quickly and can be used to analyze heterogenous media. The methodology can be used to describe the impacts of dissolution on CO2 transport through reactive cores, which to the authors knowledge, has not been described in the literature previously.