Optimizing Surfactant Additives and Nanosheet to Increase Oil Recovery in High Temperature and High Salinity Reservoirs

Abstract

Abstract Amphiphilic molybdenum disulfide (AMD) nanosheet is a novel flake type nanomaterial with unique behaviors on oil/water interfaces compared with particulate nanomaterials for increasing oil production. Surfactant additives are the key enabler for the nanosheet injection to solve the compatibility problem in high temperature and high salinity reservoirs. This study optimized some surfactant additives for the nanosheet to demonstrate some synergism effects at target reservoir conditions. Nanosheet/surfactant candidates with similar interfacial tension (IFT) performance but different emulsification abilities were compared. Original AMD nanosheet solution was a concentrated black liquid with the flake size about 80*60*1.2 nanometer (nm). The performances in a high salinity water (HSW) and high temperature up to 95°C were characterized by compatibility test, IFT measurement, and emulsification evaluation. The dynamic adsorption and oil production potential in porous media were evaluated by coreflooding tests. Indiana limestones with similar permeability were used. Performances of the nanosheet with different surfactant additives were evaluated. The AMD nanosheet was not compatible with HSW at 95°C. Two surfactants, named as S1 and S2, out of 20 samples showed significant compatibility improvements to nanosheet solution at a very low dosage concentration. IFTs of two nanosheet/surfactant mixtures with a light oil were both at magnitude of 10-2 mN/m, which were much lower than the values of nanosheet alone and surfactant alone. However, the emulsification abilities of the two nanosheet/surfactant systems with crude oil were quite different. S1 surfactant improved the emulsification ability of nanosheet, while S2 surfactant weakened the emulsion stability compared with nanosheet alone case. Accordingly, nanosheet/surfactant S1 injection produced a long-lasted emulsified oil and nanosheet/surfactant S2 injection formed a large oil bank at early stage in the oil displacement tests. But the ultimate oil recoveries of the two systems were almost the same. This study provides some insights of interaction between AMD nanosheet and surfactants and its effect on oil production performance. Improved nanosheet systems were developed to increase oil production under harsh conditions.