Viscosity measurements of high-pressure CO2 foam with sodium dodecyl polypropoxy sulfate surfactants for enhanced oil recovery application

Abstract

Rheological behaviors of high-pressure CO2 foam for enhanced oil recovery (EOR) were investigated based on the apparent viscosity measured in the range of shear rate from 102 to 105 inverse second. Surfactants used to generate the CO2 foam were sodium dodecyl polypropoxy sulfates with average propoxylation degrees of 4, 7.52, and 14.8. CO2 and water with a weight ratio of 50:50 were mixed with 1 wt % surfactant to generate the CO2 foam in a high-pressure recirculation apparatus under pressure where CO2 density becomes 0.7, 0.8, 0.9 g/mL at each temperature of 35, 45, and 55 °C. Experimental data was analyzed using power-law model to describe the behavior of CO2 foam, and Ellis model to estimate the zero-shear viscosity. The CO2 foam showed shear thinning behaviors with power-law indices ranging from 0.78 to 0.85. The viscosity of CO2 foam increased with increasing CO2 density under isothermal conditions, and decreased with an increase in temperature under isochoric conditions.