A Novel Approach to Shale Stability Enhancement in Drilling Fluid Using Nano-Crystalline Hydroxyapatite Treated with Anionic Sodium Dodecyl Sulphate

Abstract Unstable wellbore often occurs in water-sensitive shale formations during drilling, leading to longer drilling times and higher costs. This problem has been addressed by using various shale stabilizers for water-based muds (WBMs) such as polymers, salts like potassium chloride (KCl), and nanoparticles (NPs) in practical applications. The strong clay attraction to water, inhibitor hydrophilicity, reservoir heterogeneity, and shale's unique pore size collectively hinder the complete stabilization of shale inhibitors. This work discusses the effects of WBM with sodium dodecyl sulphate-treated nanocrystalline hydroxyapatite (nHAp/SDS) on shale stabilization through various tests, including a linear swelling test, a hot-rolling dispersion test, and a capillary suction time (CST) test. The rheology and filtration properties of nHAp/SDS treatment fluids that had 0.5, 1.0, 1.5, and 2.0 wt.% were also examined. All the nHAp/SDS findings were compared with those of nanosilica and KCl-WBM. The plastic viscosity of the KCl-WBM was enhanced by 20–90% with increasing concentrations of nHAp/SDS and by 10–70% with nanosilica compared with the KCl-WBM at 10 cP. When compared with nanosilica, nHAp/SDS demonstrated a greater enhancement in the fluid loss control efficiency of KCl-WBM. The fluid loss was reduced to 6.4–3.1 mL from 7.9 mL, with nanosilica decreasing it to 7.3–4.6 mL. The rates of shale plug height swelling decreased in this order: 10.1% for KCl-WBM, 8.4-6.1% for nanosilica, and 7.5–4.1% for nHAp/SDS. This suggests that nHAp/SDS is a better inhibitor. The results from the CST test show that nanosilica and KCl absorbed more water and had higher CST values than nHAp/SDS. In addition, the hot-rolling test indicates that nHAp/SDS creates rough layers on the shale surface and reduces the shale-water interaction. nHAp/SDS had a higher recovery rate of 89.8% when it was used at 120 °C compared to nanosilica and KCl-WBM, which had recovery rates of 76.6% and 52.1%, respectively. nHAp/SDS consistently outperformed KCl-WBM and nanosilica in all test conditions. The research indicates that nHAp/SDS shows promise in drilling shale-rich wells and improving wellbore stability.