Viscoelastic Oil Displacement System of Modified Silica Nanoparticles/Zwitterionic Surfactant for High Salinity Reservoir

Abstract

Polymer flooding and polymer/surfactant flooding have achieved good efficiency in the application of conventional reservoir, but the existed chemical flooding technology cannot cannot address the issues of the requirements of chemical flooding in high salinity reservoir. Under the condition of high salinity reservoir, due to the increase of calcium and magnesium ions, the increasing viscosity effect of oil displacement system is lost. In order to study the feasibility of applying nanomaterials in the field of enhanced oil recovery under the conditions of high salinity reservoir, develop a low-concentration and high-efficiency oil displacement system. EAPC solution has advantages in reducing interfacial tension, but its viscosity is not good. Therefore, hydrophobically modified silica nanoparticles (SiO2 NPs) were added to the carboxylic acid–type erucic acid amide propyl betaine (EAPC) solution. The interaction between EAPC and hydrophobic carbon chains led to the exposure of carboxyl groups, thus making the system more stable. The interfacial activity and zeta potential were studied, and the interaction mechanism between modified SiO2 NPs and EAPC was obtained. The results show that when the EAPC concentration is 0.3%, the apparent viscosity of the modified silica nanoparticles (SiO2 NPs) composite system can reach 40 mPa·s, and the oil-water interfacial tension can be reduced to 10-2 mN/m. The micro-visualization model and the simulated oil displacement experiment proved that the modified SiO2 NPs (0.3%)/EAPC (0.3%) composite system has a variety of oil displacement mechanisms. Under the simulated reservoir conditions (total salinity of 25000 mg/L, calcium and magnesium ion concentration of 500 mg/L, 70 °C), it is proved that the modified SiO2 NPs composite system had good viscoelasticity and improved oil washing efficiency. The oil displacement system has guiding significance for effectively enhancing the recovery of high salinity reservoir.