An Advanced, Balanced, and High-Performance Displacement Spacer System for Deepwater Formations

Abstract

A successful wellbore displacement and clean-up is a critical step during well completion operations. A poor cleaning performance can lead to increased cost of completion operations, potential formation damage, and thus reduced oil and gas productions. Failure to achieve a balanced displacement system can lead to negative pressures on cement jobs and tie-backs, wellbore control issues, and wellbore instability. Deepwater wells require a crucial and complete evaluation of a displacement system which will provide a balanced, effective, and efficient cleaning spacer system. Traditional displacement spacer systems typically consist of a solvent spacer and a surfactant spacer. A solvent spacer consisting of d-limonene is effective for removing oil-based drilling fluids from the wellbore; however, this is incompatible in water-based spacer systems and results in an underbalanced displacement system. On the other hand, a surfactant spacer is ineffective in displacing ester/isomerized olefin (IO) based drilling fluids. As the chemistry of drilling fluid additives become more diversified to accommodate various base oils, such as the blend of ester/IO used here, so too must the chemistry of cleaner/displacement additives to ensure appropriate compatibility. On many occasions, barite residue from the weighted spacer was found to adhere strongly to pipe surfaces and be nearly impossible to remove chemically upon contact with the surfactant spacer. This issue can cause incomplete zonal isolation. A new, balanced, and high-performance displacement system (ADS-RD) was developed and optimized for its ability to effectively remove oil-based drilling fluids, barite residue, and water wet pipe surfaces. Lab test results showed that ADS-RD was fully compatible, consistently achieved an average of 98% cleaning efficiency, and yielded water wet pipe surfaces against the ester/IO based invert emulsion drilling fluids. ADS-RD also proved to be an effective and efficient solution to other oil-based invert emulsion drilling fluids. This paper presents the testing program and lab test results for ADS-RD against a traditional displacement system with various oil-based invert emulsion drilling fluid systems with densities up to 14.8 lb/gal. This paper will also include cost savings and recommendations for field applications.