Evaluation of Lubricant Performance in Under-Balanced Coiled Tubing Drilling: An Investigation of Chemical Composition and Operational Efficiency

Abstract This study investigates the impact of different lubricant types on Under-Balanced Coiled Tubing Drilling (UBCTD) performance. The scope includes laboratory testing of three commercially available lubricants: ester-based, extreme ester-based, and vegetable-oil-based lubricants. Key performance metrics such as compatibility with field water samples and various physical properties are assessed. Experimental setups simulate UBCTD conditions to evaluate lubricant performance and phenomena associated with drilling fluid degradation, namely "cheese" and "grease." Results indicate that the extreme ester-based environmentally friendly lubricant consistently outperforms the other lubricants, demonstrating superior compatibility with field conditions. Statistical analysis confirms significant differences, underscoring the reliability of the extreme ester-eased lubricant as a promising solution for enhancing drilling efficiency while minimizing environmental impacts.