Adsorption of a foam agent on porous sandstone and its effect on foam stability

This paper presents the adsorption kinetics and equilibrium of a CO2 foaming agent onto Berea sandstone and the adsorption effect on its foam stability. Results show that the adsorption of the foaming agent onto sandstone takes about 1 week to reach equilibrium and the adsorption process is well fit by a pseudo-second-order kinetic model. The adsorption kinetics coefficient decreases with the increase of initial concentration and their relationship is well fitted by two straight lines. The adsorption density increases with surfactant concentration and their relationship is well fitted by Freundlich isotherm model rather than Langmuir isotherm model. The foam stability of the effluent foam agent that flowed through sandstone is much weaker than that of the same concentration of fresh foaming agent that was not exposed to sandstone. It is suggested that the chromatographic adsorption should be considered when optimizing the compositions of a good foaming agent. In addition, the transport mechanisms of the foam agent through sandstone were elucidated by comparing the adsorption kinetics of the foam agent on five non-porous minerals common in sandstone with that on porous sandstone and through the sandstone pore microstructure analysis.