An Experimental Study of CO2-Brine Relative Permeability in Sandstone

We present an experimental study on CO2-brine relative permeability in a Berea sandstone core at 1500 psi and 20 °C. Recently, there have been many experimental studies on CO2 relative permeability, but most of them determined the relative permeabilities only using the total pressure drop across a core sample; this pressure drop can be strongly affected by the capillary end effect, especially for a low viscosity fluid like CO2. In order to minimize the capillary end effect, we chose a long (61 cm) and low permeability (49 mD) core such that the capillary pressure in the core is negligible compared with the total pressure drop across the core. In addition, we used a core holder with four pressure taps that allow us to measure the pressure drops of the five continuous sections of the core. Capillary end effect was detected in our experimental results and was isolated to the most upstream and most downstream sections of the core. And the middle three sections are considered with minimized capillary end effect and the average of the relative permeabilities in middle three sections are taken as the best measurements. In summary, our experiments obtained a CO2 end point relative permeability of 0.4~0.8 and a brine end point relative permeability of 0.04~0.08, which are very similar to oil-brine end point relative permeabilities in water-wet sandstone.