Effect of Modified Hydroxyapatite Nanoparticles on Sodium and Calcium Cation-Contaminated Bentonite-Water Solutions at High Temperatures

Drilling in high-temperature wells may worsen the flocculation of water-based bentonite suspension (BN-WBM), particularly when common drilling fluid contaminants like calcium cation (Ca²⁺) and sodium cation (Na⁺) are present. High concentrations of these cations can adversely affect drilling fluid rheology, filtration, and density. This can result in poor well control, pipe entrapment, poor hole cleaning, and prolonged inactivity, making drilling unprofitable. Therefore, this study examined how well CaCl₂ and NaCl work with Nano-HAp to control the viscosity and filtration of BN-WBM at 25, 120, 150, 180, and 210 °C. The salt cation's (Ca²⁺/Na⁺) adverse effects on BN-WBMs and Nano-HAp's salt-tolerant activities were also shown. Adding 0.5 wt% Nano-HAp reduced the BN-salt-contaminated mud viscosity, shear stress, and fluid loss at all temperatures (25–210 °C). Salt screening demonstrated that Nano-HAp adsorbed onto the BN platelets' positive edge and negative face surfaces and protected the BN ion-sensitive regions. This prevented Ca²⁺ and Na⁺ from damaging the plate-like structure of the BN. When Nano-HAp is added to BN-CaCl₂-contaminated WBM at 210 °C, the amount of fluid lost drops by 59%, from 192 to 79 mL, and the viscosity drops from 26.23 to 10.67 mPa s. In BN-NaCl-contaminated WBM, Nano-HAp reduced the viscosity from 20.82 to 8.91 mPa s and fluid loss from 169 to 73 mL by 57%. This study demonstrated that the drilling fluids performed efficiently with 0.5 wt% Nano-HAp. This study also reveals that Nano-HAp increases BN-WBM's salt and temperature resistance and efficiency in high-salinity, high-temperature settings.