Mechanistic insights into Janus silica nanoparticles as shale inhibitors in water-based drilling fluids

Shale hydration expansion is a serious challenge in drilling fluid technology as it undermines oil and gas extraction efficiency. Swelling clay particles compromise wellbore stability and increase drilling costs. Therefore, the development of highly effective drilling-fluid shale inhibitors is urgently required. This study investigates the potential of Janus silica nanoparticles (JNPs) as novel shale inhibitors. JNPs with both hydrophilic and hydrophobic characteristics were synthesized using the Pickering emulsion method. Their inhibitory properties were evaluated and compared with those of traditional inhibitors, namely potassium chloride (KCl), polyether amine (PA), and silicon dioxide (SiO 2 ), using rheological and filtration performance, bentonite inhibition, linear swelling, and shale cutting hot-rolling recovery tests. JNPs had no significant impact on the rheological properties of the drilling fluid and notably reduced filtration loss while demonstrating superior performance at a low concentration of 0.5 wt%. This concentration reduced the linear swelling rate of bentonite from 103.1 % to 40.2 % and enhanced shale cutting recovery to 60.7 % at 160 ℃. Based on contact angle measurements, scanning electron microscopy observations, molecular dynamics simulation, ζ-potential measurements, X-ray diffraction analysis, and liquid level and capillary pressure measurements, it was proposed that the superior inhibitive performance of JNP arose from its ability to compress the electrical layer, block nanopores, and alter wettability. The novel JNPs exhibited considerable potential as an effective inhibitor of water-based drilling fluids for shale oil and gas drilling.