Enhanced stability of low oil-to-water ratio water-in-oil emulsions (oil-based drilling fluids): Synergistic effect of nano-SiO2 and emulsifiers

Nano-SiO2 has excellent potential to enhance the performance of low water-in-oil drilling fluids. The effect of hydrophilic nano-SiO2 synergistic emulsifier on the performance of water-in-oil drilling fluid was studied from the aspects of emulsion and drilling fluid system. Based on the perspective of emulsion droplets, the performance of emulsions was evaluated in terms of oil-water interface film strength, oil-water interface properties, the microstructure of emulsion droplets, droplet size distribution, dynamic stability of emulsions, and rheological properties of emulsions. The stability of the emulsion is the best when using 2 wt% nano-SiO2 and 2 wt% emulsifiers. Based on the emulsion, a water-in-oil drilling fluid system was established. By testing the rheological properties, electrical stability, and filtration performance of the drilling fluid, it was concluded that nano-SiO2 improved the performance of low-oil-water ratio water-in-oil drilling fluids. Nano-SiO2 can effectively improve the flow pattern of drilling fluid. Nano-SiO2 helps increase the demulsification voltage of the drilling fluid system after aging at 140 degrees C to 874 V, which enhances the filtration performance of the system, and the reduction rate of filtration loss is 81.8%.