Optimizing drilling fluid rheology with hybrid nanoparticles boron nitride and graphene nanosheets: an experimental study

The rheological performance of oil-based drilling fluids was enhanced using graphene nanosheets and graphene-boron nitride hybrid nanoparticles. Optimized rheology is critical for efficient cuttings transport, wellbore stability, and cost-effective drilling. Graphene nanosheets (100-1500 mg/L) increased apparent viscosity (AV) by up to 90% and plastic viscosity (PV) by up to 106% compared to the base mud across 140-240 °F, with negligible density change. The graphene-boron nitride hybrid system exhibited concentration-dependent nonlinear behavior: viscosities decreased at low concentrations (100-500 mg/L) but rose markedly at higher concentrations (1000-1500 mg/L), achieving up to 164% increase in AV and 71% in PV at 1500 mg/L and 240 °F relative to the base fluid. This synergistic effect arises from graphene's lubricating properties combined with boron nitride's structural reinforcement, enabling formation of a robust nanoparticle network that resists thermal thinning. These findings demonstrate that hybrid nanoparticles offer a tunable, effective strategy to customize drilling fluid rheology, improve hydraulic efficiency, reduce torque and drag, and lower operational costs in high-temperature environments.