Low Friction Drilling Fluid Additive Technology

The use of lubricants is commonplace when drilling with water-based drilling fluids. They are less frequently applied when drilling with non-aqueous fluids, as the oil-based drilling fluid is thought to impart a high lubricity. With increased reach of the wells, lubricants are also applied in non-aqueous fluids (NAF) to reduce torque and drag at high angle, for extended reach and horizontal wells to improve drilling efficiency. However, the performance of these lubricants in NAF at extended periods of elevated temperature at downhole conditions is often inconsistent, thought to be hampered by ineffective metal binding and hydrolytic instability of the lubricant molecule. This requires frequent re-dosing and therefore higher cost to maintain performance. In order to identify a better-performing lubricant, it was necessary to better understand the fundamentals of lubrication in a drilling fluid. For example, what portion of the well contributes most to torque and drag? What is the frictional regime that dominates the lubricity between a drill pipe and its contact points? Looking at theoretical analysis and modeling, it was found that the horizontal portion is dominated by the boundary and mixed layer friction regime, which is a combination of surface forces and fluid viscosity. Additionally, understanding of tribology from other industrial applications was employed to better design a molecule that can deliver optimum lubricity in a NAF. This new understanding led to identifying an optimized lubricant for NAF. A lubricant derived from a plant-based raw material was specifically designed to be chemically and thermally stable, binding strongly to metal surfaces, and providing a tenacious film that reduces metal-to-metal friction factors during drilling, casing run and other completion operations. The identified lubricant was tested for compatibility with NAF, including effects on rheology, elastomers, and formation damage potential. Coefficients of friction and fluid rheology comparisons and research-related field trials are presented. The results show significant (20%) reduction in the coefficient of friction after treatment, especially after hot-rolling, indicating thermal and oxidative stability of the product.