Abstract
Ensuring wellbore stability and efficient drilling in high-pressure and high-temperature (HPHT) environments remains a persistent challenge in the oil and gas industry. This study evaluates the performance of Claytone-II, a novel organophilic phyllosilicate, as a rheological additive for oil-based drilling fluids (OBDFs) under HPHT conditions. Its intrinsic hydrophobicity, swelling capacity, and high surface area suggest potential for enhancing OBDF rheology and stability. Comparative characterization with a commercial organoclay (MC-TONE) was performed using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size distribution (PSD). Key fluid properties, including density, electrical stability, sag resistance, rheology, viscoelasticity, and filtration, were systematically evaluated. Claytone-II improved emulsion stability by 8%, reduced dynamic sag, and increased low-shear yield point (LSYP), enhancing suspension and hole cleaning. Rheological analysis showed higher shear stress and viscosity across all shear rates, with the Herschel-Bulkley model confirming stronger shear-thinning behavior and a higher consistency index. Filtration tests revealed an 8% reduction in fluid loss and 12.5% thinner filter cakes, indicating more effective fluid control. These reductions fall within operationally significant thresholds for HPHT drilling, contributing to enhanced wellbore stability and reduced risk of formation damage. Claytone-II demonstrated superior performance compared to MC-TONE across all major criteria, meeting or exceeding industry benchmarks. Its integration into OBDFs offers enhanced operational reliability and efficiency in HPHT drilling environments, with implications for reduced non-productive time (NPT) and improved economic outcomes.