Synthesis of superamphiphobic nanofluid as a multi-functional additive in oil-based drilling fluid, especially the stabilization performance on the water/oil interface

Abstract Nanofluids, as an effect additive in oilfield chemistry, has recently attracted significant attention. In this study, the superamphiphobic nanofluid (SAN) was synthesized to be a multi-functional additive in oil based drilling fluid (OBMs). Properties characterization of SAN and its influence on OBMs were investigated. The results showed SAN possessed a spherical shape with a diameter of about 100 nm which could construct a micro-nano structure. Due to the special structure and functional groups (perfluorooctyl) on the particle surface, SAN could alter the shale surface wettability to superamphiphobic, decrease the filtration volume of OBMs, reduce the spontaneous imbibition and maintain the compressive strength of shale core. Furthermore, SAN could exist stably at the interface due to the superamphiphobic characteristic, instead of dispersing in either water or oil phase. Therefore, it enhances the stability of water/oil emulsion. By observing and analyzing the role of SAN in OBMs, it was found SAN could effectively decrease the surface free energy of shale core from 71.47 + 0.52 to 0.09 + 0.02 mN/m and interfacial tension of water/oil system from 32.8 to 13.5 mN/m, reduce the capillary additional pressure by 1812 Pa and reverse the capillary force from attractive to repulsive. Accordingly, the OBMs with SAN was thought to be able to be used in the drilling of unconventional oil and gas reservoir well, for the considerable stability and that less liquid would penetrate into the shale pore. So the emulsion stability was enhanced and the wellbore stability was maintained. This study might provide an avenue to solve the issues owing to OBMs during the drilling process by adding additives with superamphiphobic wettability.