NanoSurfactant: A Novel Nanoparticle-Based EOR Approach

This paper describes a nanoparticle-based approach for stabilizing the low-cost petroleum sulfonate surfactants in high salinity and temperature water to enable their utility in EOR applications in typical carbonate reservoirs. The paper presents and discusses experimental results on the phase behavior of three of such NanoSurfactant formulations and their interfacial tensions (IFT) with crude oil, in order to evaluate their ability to mobilize oil during EOR operations. The three NanoSurfactant formulations were prepared through a one-step nano-emulsification process involving high salinity water, 5 wt% petroleum sulfonate solution and a low-dose of three different 4 wt% co-surfactant solutions. The resulting formulations had a 0.2 wt% of total active ingredients. One of the three formulations was persistently stable, colloidally and chemically, in high salinity water (~ 56,000 ppm) at high temperature (100 °C) for more than six months, while the other two showed signs of instability after about four months. Interfacial tensions between crude oil and NanoSurfactant solutions, measured using a spinning drop interfacial tensiometer at 90 °C, was in the 10−2 to 10−3 mN/m range and substantially lower than that with high salinity water alone or solutions of corresponding co-surfactants of similar concentrations. Phase behavior, investigated by monitoring the clarity and UV absorbance changes in a system of crude oil atop of the NanoSurfactant formulation at 100 °C without mechanical mixing, showed enhanced formation of homogeneous oil-in-water emulsions at 100 °C without the aid of any mixing. Our results demonstrate the ability of NanoSurfactants to mobilize oil under typical carbonate reservoir conditions. Their colloidal nature gives them advantages over conventional micellar surfactants by allowing them to migrate deeper in the reservoir due to size exclusion and chromatographic effects. The simple method utilized in making NanoSurfactants opens the door for better utilization of numerous low-cost, yet salinity- and temperature-intolerant chemicals in typical carbonate oil reservoir applications.