| Surfactant adsorption on reservoir rocks or sands is one of the major factors that may significantly reduce the effectiveness of alkaline/surfactant flooding for heavy oil recovery. It is difficult to determine the surfactant adsorption by measuring the difference in surfactant concentrations before and after adsorption when the water phase contains fine heavy oil drops that cannot be separated by using a centrifuge. In this study, sand-washing method was developed to quantitatively determine the surfactant adsorption on sand surface in oil/(alkaline/surfactant solution)/sand systems. By combining the sand-washing method and the conventional static adsorption test, this study successfully determined the distribution of surfactants between the oil-water interface and the sand surface in alkaline/surfactant flooding process for heavy oil recovery. The results showed that surfactant adsorption on sand would diminish over 40% due to the formation of emulsion with the presence of the heavy oil. With sand-washing method, equilibrium surfactant concentration in an aqueous phase could be determined from the surfactant adsorption isotherm. Using the mass balance method, surfactant partitioned to oil-water interface could be calculated. (Abstract shortened by UMI.)... |
