Laboratory study of the Non-Newtonian behavior of supercritical CO2 foam flow in a straight tube

Rheological properties of supercritical CO2 (ScCO2) foam fluids are essential to understand foam displacement mechanisms in the research & development of efficient CO2-EOR and CO2 geological storage technologies. In this paper, a systematic laboratory study concerning non-Newtonian ScCO2 foam flow characteristics in a straight tube was carried out under different gas-liquid ratios. Through modifying experimental pressure and temperature conditions, comparative studies on liquid phase CO2 and gaseous CO2 foam rheology were also carried out. The experimental results show obvious shear-thickening behavior for the scCO2 foam (45 °C and 8.0 MPa) with flow behavior index increasing from 1.03 to 1.76 with increasing foam quality. And the apparent viscosity of scCO2 foam could reach up to 140 times of the single-phase water. The liquid phase CO2 foam (25 °C and 8.0 MPa) also exhibits clearly the shear-thickening characteristics with flow behavior index ranging from 1.56 to 1.88. The gaseous CO2 foam, on the other hand, behaves in a shear-thinning or pseudo-plastic manner with flow behavior index of 0.70 < n < 0.76. Due to the decreased interfacial tension and less bubble coalescence rate, much finer foam textures are observed for ScCO2 and liquid CO2 bulk foam, which mainly contributes to the shear thickening behavior for ScCO2 and liquid CO2 foam fluid.