The Ramakrishnan-Cappiello method is based on the injection of an incompressible nonwetting phase at successively higher pressures (or flow-rates), and measuring the velocity (or injection pressure), while eliminating end-effects. Many enhanced oil recovery processes involve injection of a compressible nonwetting phase for which the velocity through the medium increases by decompression. Here, exact and perturbation expressions for decompression corrections are given along with Pade approximants of density and viscosity for CO2. We compute an increase of 1, 4 and 11% for liquid, supercritical, and gaseous CO2 relative permeability for previously conducted experiments. (c) 2013 Elsevier Ltd. All rights reserved.