Development of online separation and surfactant quantification in effluents from an enhanced oil recovery (EOR) experiment

Abstract Surfactant flooding is one of the Chemical Enhanced Oil Recovery (cEOR) methods used to meet the growing demand for oil. It consists in injecting an aqueous formulation containing surfactants, whose performance, both in terms of incremental oil production and surfactant adsorption, is assessed in the laboratory with coreflood tests. Currently, coreflood effluents are collected in tubes throughout the experiment and the analyses are performed offline. Surfactants are measured in the aqueous phase by Hyamine assay or by liquid chromatography. It is noteworthy that these analyses may be difficult to carry out since the effluents may contain stable emulsions. Moreover, it is unclear whether all surfactants are in the aqueous phase, or whether they are partly trapped in the oil phase. To overcome these difficulties and quantify surfactants reliably in coreflood effluents, we have developed an online experimental setup that includes: a dilution “millifluidic” chip to transfer the surfactants in the aqueous phase, a “microfluidic” membrane-based separation device to separate oil from the aqueous phase, and an online UV–visible spectrometer to measure the surfactant concentration. This setup was successfully validated with model fluid mixtures and was evaluated on real systems. Finally, it was tested under representative conditions of coreflood experiments. The obtained results proved the efficiency of the setup to facilitate the quantification of the surfactants in the effluents which clearly improves the accuracy of the measurements.