Two-phase relative permeability measurements in Berea sandstone at reservoir conditions
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The goal of this research was to explore the role of composition on relative permeability by performing two-phase steady-state relative permeability measurements. The effect of changing fluid composition was studied by using different fluid pairs: CO2/brine, N2/brine and n-decane/brine. In addition, the experiments were performed at two different pressures for the same fluid pair, CO2/brine, since pressure also changes fluid properties such as density that may have an effect on the relative permeability. A very important part of this study was the establishment of the experimental procedures needed to ensure accurate measurements of the relative permeability. These are difficult measurements subject to many experimental artifacts and complications. For example, a special effort was made to reduce capillary end effects in these experiments. Although many studies have reported relative permeability measurements for N2/brine, CO2/brine, or oil/brine, this is the first experimental study where the relative permeability for different fluids was measured using precisely the same methodology. The same core was used for all experiments allowing for a direct comparison between the different fluids. Furthermore, special care was taken in this study to eliminate experimental artifacts that affect relative permeability measurements. In particular, experiments were performed at a high Rapoport-Leas number to minimize capillary end effects. Fractional flow effects, e.g. not being able to flow enough pore volumes to reach residual saturation throughout the whole core, while not eliminated, were circumvented by measuring sectional pressure drops, as opposed to only the pressure drop over the whole core.