Lack of relevant screening methods of oil recovery techniques for water flood with added nanoparticles in a given reservoir are hindering its implementation for enhanced oil recovery (EOR) purposes. Moreover, the understanding of the underlying mechanisms of oil increased by nanoparticles must be improved.
In this work, we screened twenty-three different types of silica nanoparticles as additives to injection water for oil recovery applications. The nanoparticles were surface functionalised to remain stable in the injection water and be active at the surface. The hypothesis is that the particles will improve the microscopic oil recovery efficiency of water flood in an oil reservoir. The concentrated solution of nanoparticles were prepared to 0.1 wt % concentration in synthetic North Sea water. Crude oil was obtained from a field in the North Sea. The following investigations were carried out to quickly verify the performance of nanoparticle oil recovery: 1) secondary injection through a visual glass micromodel. 2) For the prominent silica nanoparticles, we evaluated oil recovery by conducting secondary core flooding experiments in water-wet Berea sandstone rocks; and 3) the displacement mechanisms of nanoparticles were investigated by interfacial tension measurements between nanofluids and crude oil; Amott-wettability test; and by analyzing differential pressure across the core.
Experimental results from secondary floods showed that modified silica nanoparticles can boost oil recovery. The core flood recoveries ranged from 45.7% to 54.5% of original oil in place (OOIP) compared to 39.7% of reference water flood. Displacement studies revealed that, oil recovery was obtained from a contribution of interfacial tension reduction, wettability alteration, and log jamming effect due to pore blockage. This work suggests a procedure for screening nanoparticles for EOR applications while providing insights into the role of the modified-silica nanoparticles for recovery of oil.