Comparative Evaluations of Surfactant-Functionalized Eggshell Powder as a Bridging Agent in Water-Based Muds under High-Temperature Conditions

Abstract

Abstract The exploration of cost-effective and eco-friendly bridging materials in water-based muds (WBM) highlights the use of agricultural waste components, such as eggshell powder (ESP). Untreated ESP is unstable, poorly dispersed, and tends to aggregate, which reduces its effectiveness at elevated temperatures. In this study, Tween 80, cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) were utilized to modify ESP particles, enhancing their effectiveness as bridging agents. The characteristics of these modified ESP systems are evaluated at 2 and 4 wt.% concentrations, in comparison with both industrial calcium carbonate (CaCO3)-based muds and untreated ESP (96.7% CaCO3) at temperatures of 25 °C and 260 °C. The data indicate that surfactant-modified ESPs provide enhanced steric and electrostatic interactions, leading to improved colloidal stability. While industrial CaCO3 is effective in controlling fluid loss under low-pressure and low-temperature (LPLT) conditions, untreated ESP offers better performance in high-pressure and high-temperature (HPHT) scenarios due to its enhanced thermal resistance. Modified ESP muds demonstrated improved plugging efficiency, enhanced rheological stability, reduced filter cake thickness, and minimized fluid loss. CTAB and SDS-modified ESPs showed the lowest filtrate loss and highest rheological activity, with CTAB reaching optimal values at 25 °C and SDS at 260 °C. In the case of LPLT, 2 and 4 wt.% CTAB-based ESP reduced the filtrate loss of untreated ESP by 48% and 75.3%, respectively, while SDS resulted in reductions of 33% and 74%. Under HPHT, the filtrate loss for ESP modified by SDS decreased by about 70.3%, exceeding the 35.8% reduction achieved with CTAB. The relative particle plugging index (PPI) values confirmed improved plugging efficiency of CTAB (PPI = 48 – 75.3%) at LPLT and SDS (PPI = 33 – 70.3%) at HPHT. Tween 80 demonstrated only moderate advantages. Overall, SDS-modified ESP exhibited the most effective mud stability and plugging behavior across both temperature regimes, while CTAB is superior at LPLT. These results suggest that SDS- and CTAB-treated ESP serve as environmentally friendly alternatives to industrial CaCO3 bridging agents for drilling muds in challenging high-temperature conditions.