Rheological Evaluation of Mucuna sloanei (Ukpo) as a Sustainable Bio-Polymer Viscosifier for Water-Based Drilling Fluids in Nigeria

Abstract

The stability of drilling fluid rheology under varying operational conditions is critical for efficient petroleum drilling. Conventional water-based drilling fluids (WBDFs) often suffer instability under high-temperature and saline environments, necessitating sustainable alternatives. This study investigates Mucuna sloanei (Ukpo), an indigenous Nigerian bio-polymer, as a viscosifier for WBDFs, with Gum Arabic (GA) serving as the control. Laboratory experiments were conducted using API rotary viscometer protocols to evaluate viscosity and gel strength of bentonite-based muds modified with incremental concentrations (1–7 g/L) of Mucuna sloanei and GA. Tests were performed under ambient conditions, elevated temperatures (35–120°C), and saline environments (NaCl contamination). Comparative analyses were carried out to assess rheological performance and operational suitability. At ambient conditions, Mucuna sloanei significantly enhanced viscosity (24 cp to 49 cp at 600 rpm) and gel strength (9 lb/100 ft² to 31 lb/100 ft² at 10 sec), outperforming GA in thickening capacity. However, MS exhibited sharp declines in viscosity and gel strength at elevated temperatures, while GA demonstrated superior thermal stability (23 cp to 20 cp at 600 rpm across 35–120°C). Under saline conditions, MS showed strong viscosity retention (20 cp to 44 cp at 600 rpm) but with instability at higher dosages, whereas GA maintained controlled rheological behavior (23 cp to 35 cp at 600 rpm) with steady gel strength increases.This is the first comparative study of Mucuna sloanei and Gum Arabic under combined concentration, temperature, and salinity stress conditions. Findings reveal that Mucuna sloanei is a potent viscosifier suitable for low-to-moderate temperature drilling environments requiring high gel strength, while GA offers greater resilience in high-temperature and saline operations. The study underscores the potential of indigenous bio-polymers as eco-friendly alternatives to synthetic additives, supporting sustainable drilling fluid development in Nigeria and advancing green petroleum engineering practices.