Surfactant screening for foam EOR: Correlation between bulk and core-flood experiments

• The small-scale core-flood set-up is shown to be a useful tool for rapid screening of surfactants.
• Bulk foam stability only correlates with foam apparent viscosity in the absence of oil.
• The bulk-foam stability increases with increasing interfacial tension between the oil and surfactant solution.
• The E, S and B coefficients are unable to predict foam behavior in the presence of oil.

Aqueous foams play an important role in many industrial processes, from ore separation by froth flotation to enhanced oil recovery (EOR). In the latter case, the foam is used as a means of increasing the sweep efficiency through the oil bearing rock – the complex, structure dependent, flow behavior of the foam means that it has improved penetration of lower permeability regions than would be obtained with a Newtonian fluid. An understanding of how foam behaves when flowing through a rock is therefore of great importance when selecting suitable surfactants for EOR processes. Previous tests have suggested that there is no reliable correlation between bulk foam behavior and foam behavior in a rock core, especially in the presence of oil. We present a comparative study of bulk stability tests and core floods with foam, both with and without oil. Core-flood tests were conducted in rock cores with a diameter of 1 cm, significantly smaller than typical cores. Apparent viscosity/injected gas fraction response curves were obtained, both with and without oil in the system.The current work finds that, in the absence of oil, there is a positive correlation between bulk foam stability and core-flood performance. Bulk foam experiments can therefore be a useful screening tool to give a good indication of the surfactant performance in the core flood. However, in the presence of oil, although there was a general trend of increasing maximum apparent viscosity with increasing bulk foam stability, no strong correlation was found between bulk foam stability and the performance in the core for the experiments performed.

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