Exploring Limonite Pigment as a Sustainable Corrosion Inhibitor for Drill Pipe Protection in High-Pressure, High-Temperature Environments

ABSTRACT: Drill pipe corrosion poses significant operational challenges in the oil and gas industry, particularly in high-pressure, high-temperature (HPHT) drilling environments, where it can jeopardize worker safety and equipment integrity. While various corrosion inhibitors have been deployed, many exhibit effectiveness and economic feasibility limitations. This study investigates the potential of limonite, an ochre pigment known for its oxidation and absorption properties, as a corrosion inhibitor under HPHT conditions. Limonite pigment (LP) morphology and elemental composition were analyzed through scanning electron microscopic (SEM) and electron dispersive spectroscopy (EDS) respectively. An HPHT drilling environment was simulated in a reactor vessel with N80-grade steel coupons representing drill pipe material. The corrosion rates of water-based drilling mud (WBDM) augmented with various concentrations (0, 1, 2, 3, and 4 lb.) of limonite pigment were assessed under dynamic conditions at varying temperatures, pressures, and rotational speeds. The results of the temperature investigation show that the lowest and highest corrosion rates occurred at 60°C and 150°C respectively. Therefore, a more severe corrosion attack is expected at higher temperatures. An increase in pressure and rotation speed was discovered to cause an increase in corrosion rate. The effect of an increase in the temperature on corrosion rate is more severe than pressure and rotation speed. This study identifies limonite pigment as a promising, environmentally friendly alternative to conventional corrosion inhibitors. Additionally, it reveals that corrosion attack is more severe at elevated temperatures than at lower temperatures providing new insights for drilling fluid design in HPHT conditions.