One major drawback in the implementation of CO2/surfactant enhanced oil recovery is the high cost of the surfactant volume needed and the extrapolated amount of surfactant required for use in the field. Therefore, there exists a need for a methodology to evaluate the most economic surfactant volume that will lead to optimum oil production.
This paper presents the results of laboratory experiments that were designed to study the performance of foam injection and to obtain information on the parameters that will be utilized in a future modeling study to determine the minimum but most effective volume of surfactant needed for optimum foam generation and hence oil recovery in a porous medium. The effect of reservoir pressure and surfactant concentration is studied.
Carbon dioxide and surfactant solution were co-injected into Berea sandstone core that was saturated with brine and oil after a waterflood process. Some of the values of parameters utilized in the experiments include surfactant concentrations of 0.1 wt % and 0.5 wt %, average back pressure of 2350 psi and total flowrate of 0.4 cm3/min, with CO2 injected at 0.3 cm3/min and surfactant concentration at 0.1 cm3/min, which results in a volumetric flow ratio of 3:1 and foam quality of 75%.
Results show that at a higher surfactant concentration, more oil was recovered, and a steady increase in pressure difference was observed. This indicates that foam was formed, which was also seen at the production end of the system. The foam created during the experiments with the 0.1 wt % surfactant concentration, on visual inspection, appeared to be weaker than that formed in the case of the 0.5 wt % concentration.