Green additives effectiveness in water-based drilling mud performance: A study of pistachio shell powder, magnesium oxide, and carbon black particles.

Drilling fluid performance is critical for wellbore stability, cuttings transport, and minimizing formation damage, but conventional additives often raise environmental concerns. This study evaluates the effectiveness of three additives, pistachio shell powder (PSP), magnesium oxide (MgO) nanoparticles, and carbon black (CB), in enhancing the rheological and filtration properties of water‑based drilling muds (WBMs). Ten mud formulations with varying additive concentrations (1-5 g) were prepared, and key parameters including density, pH, plastic viscosity, yield point, gel strength, API fluid loss, and shear‑dependent viscosity were systematically characterized. Results show that PSP significantly improved rheological performance, increasing yield point to 0.771 kg/m² and gel strength to 19.6 lb/100 ft², while maintaining stable density (9.82-9.88 ppg) and pH (8.0-8.2). In filtration tests, PSP achieved an API filtrate volume of 22 mL, superior to CB (26-27 mL) and comparable to MgO, owing to the formation of a thin, low‑permeability filter cake. All muds exhibited non‑Newtonian shear‑thinning behaviour, with PSP offering an optimal balance between viscosity for cuttings suspension and flowability during circulation. As an agricultural waste‑derived additive, PSP demonstrates technical performance on par with MgO nanoparticles while being cost‑effective and environmentally suitable. The main goal of this research is to comparatively study the effects of pistachio shell powder (PSP), magnesium oxide (MgO) nanoparticles, and carbon black (CB) on the rheological and filtration characteristics of water-based drilling muds under similar experimental conditions, and to identify a sustainable and economical drilling fluid additive.