Nanotechnology has shown great promise in tackling various challenges in oil and gas drilling operations. The incorporation of nanoparticles in drilling fluids has been found to improve their rheological behavior and overcome common challenges associated with drilling operations by reducing fluid loss, minimizing formation damage, improving heat transfer properties, and decreasing friction between the drill pipe and surrounding formation. Most available literature, however, focuses on using inorganic and non-biodegradable nanomaterials that could be expensive to scale up and might pose some environmental issues. Cellulose-based nanomaterials are among the most produced naturally derived nanomaterials. Research on the application of these nanomaterials in drilling fluids has been limited to evaluating the rheological behaviour and filtration properties of bentonite-based drilling fluids, neglecting the effect of nano-cellulose on the lubricity of drilling fluid. Accordingly, this study aims to investigate the performance of bentonite and non-bentonite water-based drilling fluids in the presence of cellulose nanocrystals (CNCs) at varying content (0.5, 1.0, and 2.0 wt%). The performance of these drilling fluids was evaluated in terms of lubricity, filtration properties, and rheological behaviour before and after high temperature (76 oC) aging. The results show that the incorporation of CNCs into water-based drilling fluids enhanced their lubricity leading to significant torque reductions. This improvement in lubricity was more pronounced in bentonite polymer-free drilling fluids. Furthermore, lower filtrate volume and more uniform filter cake were observed for nano-modified drilling fluids compared to the reference fluids indicating decreased fluid loss. The presence of CNCs also led to higher yield point, viscosity, and gel strength than the reference fluids. This thesis holds valuable insights for the application of CNCs in oil and gas drilling operations, especially in sustainably reducing torque and drag, while maintaining excellent performance.