Nanoparticle dispersion with surface-modified silica nanoparticles and its effect on the wettability alteration of carbonate rocks

The main challenge of nanotechnologies for enhanced oil recovery (EOR) in carbonate reservoirs is to maintain the colloidal stability of nanoparticle dispersion (nanofluid) under the reservoir conditions with high salinity and high temperature. This study presents a nanofluid as an injection fluid for EOR under the extreme condition. The nanofluid was composed of surface-modified silica nanoparticles by a silane coupling agent (GPTMS, (3-Glycidoxypropyl)trimethoxysilane). The particle size distribution and particle aggregation were measured and observed to evaluate colloidal stability of the nanofluid by the light scattering and electron microscopy methods. As a result, the colloidal stability of the nanofluid was achieved at the salinity up to 20 wt% of base fluid at 90 degrees C, when the amount of GPTMS was 1 mmol/g. The wettability alteration test of carbonate rocks was carried out to validate the applicability of the nanofluid in the reservoir conditions. The results showed that the rock wettability of dolomite and limestone was effectively altered to neutral-wet and water-wet from strongly oil-wet, respectively, by the nanofluid with a small portion of particle concentration. Therefore, it is believed that the nanofluid can be an effective EOR agent in carbonate reservoirs.