Effect of Silica Nanoparticles Adsorption on the Wettability Index of Berea Sandstone

ABSTRACT Nanotechnology has already drawn attentions in the oil and gas industry for its many potential applications in exploration and production processes, especially in the enhanced oil recovery (EOR) area. Nanoparticles, as a part of nanotechnology have been suggested as a promising EOR method in the future. Some EOR mechanisms for nanoparticle have already been proposed, such as disjoining pressure gradient, interfacial tension reduction, wettability alteration and plugging of big pore channels. Hence, the study objective of this paper is to investigate the effect of silica nanoparticle adsorption on the wettability index for Berea sandstone. In this experimental study, both hydrophilic and hydrophobic silica nanoparticles with 7 nm average particle size were used. Water wet and neutral wet Berea sandstone cores with 250-450 mD permeability were selected as porous media. Three weight percent (3 wt. %) NaCl brine and ethanol were used as suspension fluids for hydrophilic and hydrophobic silica nanoparticles respectively, and the wettability index of Berea sandstone treated by nanoparticle was measured using Amott method. The results indicated that the hydrophilic nanoparticles can make neutral wet cores more water wet and increase the wettability index of water wet cores about 10%. The hydrophobic nanoparticles can delay the imbibition process for water wet cores but have no significant effect on wettability change. While for neutral wet cores the high concentration hydrophobic nanoparticles suspension can make it more oil wet. The adsorption and retention of nanoparticles in porous media can reduce its porosity and permeability.