Laboratory Measurements of CO2-Foam Mobility

Abstract

Summary Mobility control of high-pressure CO2 floods by use of foam is a promising oil recovery technique. Critical information for the use of CO2 foam as a thickened displacement fluid is the ratio of the combined CO2/surfactant-solution flow rate to the pressure drop in the swept region. This foam mobility can be measured in laboratory experiments. In this work, a high-pressure apparatus was designed and carefully calibrated to measure foam mobilities at various flow rates. These measurements were made during simultaneous flow of the dense CO2 and surfactant solutions through core samples. Dependence of CO2-foam mobility on several variables was observed. The effect of aqueous surfactant concentration on CO2-foam mobility was explored thoroughly. The dependence in this case was such that foam mobility decreased steadily as surfactant concentration increased until a minimum mobility was attained at some particular concentration well above the conventional critical micelle concentration (CMC). The effect of foam volume fraction showed that mobility decreases with increasing fraction of surfactant solution. Also, it was found that the relative mobility (mobility divided by rock permeability) of CO2 foam was higher in Rock Creek sandstone than in Berea sandstone. Shear-thinning behavior was observed under some conditions in our experimental range of total flow rate.