Effect of surfactants at ultra-low concentration in oil/brine diphasic displacement: The way to unlock EOR polymer field projects

Abstract

Capital and operating expenses of polymer injection projects are sometimes borderline to ensure profitability. Therefore, it is of interest to significantly improve the oil recovery potential with a low enough marginal cost. The addition of surfactant is very effective to enhance oil recovery, but, with traditional formulation guidelines, the high cost of chemicals and the difficulties in preparing the SP solution is major obstacles. The objective of this study is to try to adapt the concept of optimal surfactant formulation, without trying to achieve ultra-low interfacial tensions, to improve the overall efficiency of polymer injection.Phase behaviors of conventional surfactants/crude oil/water systems have been studied to find the optimal formulation conditions at high surfactants concentration. This ultra-low tension formulation was then diluted by more than one order of magnitude compared to “traditional” surfactant designs and was successfully tested in core floods at different injected volumes in order to optimize the design and minimize the cost.Contrary to expectations, it was found that the optimal formulation used at ultra-low concentrations can sufficiently modify the flow propagation to significantly improve polymer flood. The volume of surfactant injected was optimized to be “good enough” just to upgrade polymer flood without seeking complete desaturation. The low formulation concentration level makes it easy to handle and can considerably extend the application limits of polymer injection.