A High-Performance Organoclay for Enhancing Rheology, Stability, and Filtration Control in HPHT Oil-Based Drilling Fluids

Oil-based drilling fluids (OBDFs) are widely used in high-pressure and high-temperature (HPHT) drilling operations; however, maintaining stable rheology, suspension capacity, emulsion integrity, and filtration control under extreme conditions remains challenging. Although several studies have investigated organoclays (OCs) for OBDF applications, most existing work focuses primarily on conventional rheological properties under ambient or moderately elevated temperatures, with limited integration of sag behavior, emulsion electrical stability, viscoelastic response, and HPHT filtration performance within field-representative formulations. In this study, Claytone-SF, an organophilic smectite clay, is comparatively evaluated against a commercially deployed OC (MC-TONE) used in regional OBDF formulations, using an identical, field-based OBDF formulation. A comprehensive experimental program was conducted, including density, electrical stability, static and dynamic sag tests, rheology, viscoelastic measurements, and HPHT filtration at 275 °F. Material characterization using XRD, XRF, SEM, and particle size analysis was performed to relate clay characteristics to fluid performance. Relative to the benchmark fluid, the Claytone-SF formulation exhibited a 3% increase in electrical stability, a 40% increase in yield point (YP), a 49% increase in gel strength, and a reduction in inclined sag factor from 0.531 to 0.507. In addition, HPHT filtration performance improved, with a 6% reduction in filtrate volume and a 12% decrease in filter cake thickness. These results indicate improved consistency in low-shear rheology and suspension stability under the tested HPHT conditions. The observed performance enhancements are consistent with the combined influence of Claytone-SF’s mineralogical composition, platelet morphology, and organophilic surface modification. The study is subject to limitations, including evaluation at a single OC dosage, use of one commercial benchmark, laboratory-scale testing, and a maximum testing temperature of 275 °F. Despite these constraints, the results provide a performance-based, comparative assessment of OC behavior in HPHT OBDFs and practical guidance for OC selection under realistic drilling conditions.