Synthesis of Novel Salt-Resistant and High-Temperature Hydroxyapatite Nanoparticle for Rheology, Lubricity, Surface Tension, and Filtration Property Modifications of Water-Based Drilling Mud

Abstract Optimal additives are often needed to improve the performance of water-based muds (WBMs) in tough drilling conditions like deep water reservoirs, salty formations, and high-temperature wells. The efficiency and contribution of nanoparticles (NPs) in enhancing the performance of WBMs in these tough drilling conditions have been continuously demonstrated in recent applications. Nevertheless, the use of NPs in drilling fluids is still very new, and their higher specific surface energy frequently compromises their stability within the fluid system. This has resulted in a decline in drilling performance and outputs, highlighting the importance of using well-dispersed and stabilized additives in drilling fluids. Hydroxyapatite nanoparticles (nanoHAp) were therefore designed in situ through the chemical precipitation technique with sodium dodecyl sulphate (SDS) to improve the lubricity, rheology, and filtration properties of WBM. It was also developed to reduce surface tension, resist calcium chloride (CaCl2) contamination, and improve the drilling of high-temperature wells. NanoHAp in various amounts (0.1, 0.2, 0.3, 0.4, and 0.5 wt.%) were added to conventional WBM, BN-WBM (bentonite-water solution), and BN/Ca (bentonite solution contaminated with CaCl2) at 25, 150, 180, and 210 °C. The results showed that nanoHAp exhibits excellent thermal stability. At 210 °C and 1021 s−1 shear rate, its concentrations of 0.1–0.5 wt.% increased the viscosity by 42.4–122% over the reference sample at 30 mPa-s. Under the same conditions, they decreased the fluid loss from 44.6 mL to 10.9–21.8 mL. They also served as friction and surface tension agents, improving the lubricity by 7.8–47.5% from 0.295 and reducing the surface tension by 5.1-29% from 59 dyne/cm3 at 25°C. In salt resistance tests, the BN/Ca solution had an excessive viscosity and fluid loss of 155.4 mPa-s and 192 mL, respectively, at 210 °C; however, nanoHAp reduced the viscosity to 50 mPa-s by 67.8% and the fluid loss by 59% to 79 mL. This study highlights the positive impact of nanoHAp on the fluid properties of drilling mud, particularly under CaCl2 contamination and high temperature conditions.