Nanoparticle-stabilised invert emulsion drilling fluids for deep-hole drilling of oil and gas

Invert emulsions are used to drill for oil and gas when good wellbore stability and high temperature tolerance are required. These drilling fluids contain a solid phase and two immiscible liquid phases stabilised with a polymeric surfactant. In ultra deep drilling, due to high temperature, the surfactant degrades causing phase separation. However, fine particles can be used as stabilisers, and the result is a Pickering emulsion. Here, we demonstrate that the use of a combination of hydrophobic nanoparticles and organically modified nanoclay results in stable water-in-oil invert emulsions model drilling fluids. These gel-like model fluids have the desired plastic viscosity and yield stress suitable for drilling fluid applications that can be modified by adjusting the nanoparticle-content. Aging experiments at 225 ◦ C showed that they also have high-temperature stability for demanding drilling operations.