Evaluation of Claytone-ER as a novel rheological additive for enhancing oil-based drilling fluid performance under high-pressure high-temperature conditions

Abstract Conventional oil drilling fluids often fail under extreme (high-pressure high-temperature, HPHT) conditions, leading to wellbore instability and formation damage, causing substantial economic losses in the drilling industry. The objective of this study was to evaluate the performance of Claytone-ER, a novel rheological additive for oil-based drilling fluids (OBDF), compared with a conventional organoclay (OC). Claytone-ER improved the drilling fluid performance significantly, including enhancement of the emulsion stability by 3% (863 V to 891 V), mitigation of sagging behavior, and substantial improvement in key rheological parameters such as plastic viscosity (PV) by 26.5%, yield point (YP) by 98%, and apparent viscosity (AV) by 36.5%. Additionally, Claytone-ER enhanced gel strength (GS) and improved filtration properties, reducing filtrate volume by 8% (5.0 cm 3 to 4.6 cm 3 ) and filter cake thickness by 6% (2.60 mm to 2.45 mm). These results demonstrated the potential of Claytone-ER to enhance the stability and performance of OBDFs under extreme HPHT conditions, leading to improved drilling efficiency, reduced non-productive time, and cost savings for drilling operations. Furthermore, the enhanced rheological properties, sag resistance, and filtration control contribute to better wellbore stability and minimize the risk of formation damage, ensuring long-term well productivity. This study represents a significant advancement in drilling fluid technology, paving the way for safer and more efficient drilling operations in challenging HPHT environments. Future research will focus on field trials to validate the efficacy of Claytone-ER in real-world HPHT drilling scenarios.