Cerium oxide and bismuth oxide nanocomposites as clay swelling inhibitors in water based drilling fluids

Wellbore instability driven by reactive clay swelling remains a critical and costly challenge in the application of water-based drilling fluids. The core objective of this study is to evaluate the fundamental clay hydration inhibition potential of CeO₂-Bi₂O₃ bimetallic nanocomposite to ensure robust operational stability. The nanomaterial was synthesized via co-precipitation, subjected to 1-hour ultrasonic homogenization and 1-week static aging, and subsequently evaluated using dynamic light scattering, zeta potential, static filtration (100 psi, 60 °C), and hot rolling tests (105 °C). Experimental results demonstrated that an optimal nanocomposite concentration of 500 ppm fundamentally arrests clay hydration via double-layer compression (- 38.7 mV) and pore plugging, yielding an exceptional dynamic shale cutting recovery of 93%, significantly outperforming the standard 3 wt% KCl benchmark (78%). System compatibility assessments proved the additive acts as a non-damaging agent, maintaining vital plastic viscosity and yield point parameters while improving API filtration control in polymeric (9.5 to 7.8 mL) and weighted mud systems. In conclusion, the CeO₂-Bi₂O₃ nanocomposite serves as a highly efficient chemical inhibitor that mechanically stabilizes wellbores and prevents fluid invasion, presenting a viable, non-damaging alternative for advanced drilling fluid formulations.