Plantain peel ash as a natural retarder for controlling thickening time in saline contaminated cement slurries

Abstract

The control of cement slurry thickening time is paramount for successful well cementing operations where saline contamination poses a significant challenge by accelerating cement hydration and potentially leading to operational failures such as premature setting. This study evaluates plantain peel ash (PPA) as a sustainable natural retarder for controlling thickening time (TT) in sodium chloride (NaCl) and magnesium chloride (MgCl₂) contaminated Class G cement slurries. PPA was incorporated at dosages of 1%, 3%, and 5% by weight of cement (BWOC), with saline concentrations of 1%, 3%, and 5%. Thickening time was quantified using a high-pressure, high-temperature (HPHT) consistometer at 150°C and 24-hour compressive strength. Results demonstrated that PPA extended TT in a dose-dependent manner, countering saline-induced acceleration. At 5% NaCl, TT increased from 65 minutes (baseline) to 150 minutes (5% PPA), indicating a 130% improvement. MgCl₂ often restored TT to uncontaminated control levels at 180 minutes. PPA also reduced plastic viscosity by up to 56.7% and yield point by 41.7% in saline slurries, enhancing pumpability, and recovered compressive strength from 1200 psi to 1740 psi at 3% NaCl with 1% PPA. The retardation mechanism was attributed to PPA's high potassium oxide content (40-50%), which adsorbs onto cement grains. Statistical analysis (ANOVA) confirmed significant effects of PPA dosage on TT (F = 47.2, p < 0.001). PPA shows a better substitute for synthetic retarders like lignosulfonates.