The latest growth of North American unconventional shale plays is supported by the shift towards improved well designs: extended well laterals, high-intensity proppant loadings, and adoption of slick water fluids for fracturing. To optimize well productivity and economics, producers continue to push the well lateral boundaries from 10,000-ft to over 15,000-ft, creating super lateral wells, which pose significant challenges and pushed the boundaries of extended reach Coiled Tubing (CT) operations. This document outlines field operational details, string design and downhole tool considerations that had a major effect on the success of extended reach CT interventions in super laterals with 2.375-in CT diameters.
Currently, several U.S. operators have succeeded with 7,500-ft to 10,000-ft range laterals using CT in post-fracture plug mill-out and clean-out operations. These well designs and successive service operations require larger CT diameters and higher pumping pressures to effectively complete job objectives. Generally, 2.375-in CT diameters of over +23,000-ft in length, that feature a robust wall design and materials are being used to withstand the combined pressure loadings and access target depths, –while minimizing bend cycle fatigue accumulation and deformation during operations. Operational plans comparing CT forces, lock-up behavior and hydraulics analysis, along with friction matching of post-job data evaluations, were used to compare the CT performance in the newest well lateral records. Other operational factors, such as equipment availability, logistical issues, and field deployment, are also considered in the analysis of using CT in these complex wells.
Field results demonstrated that CT well interventions in over 14,500-ft laterals are feasible by using highly engineered 2.375-in CT, friction reduction tools accompanied by fluids chemical additives, and tailored operating techniques that improve efficiencies. The application of high strength quench and tempered material with specific wall configurations that feature the use of the thickest gauge used in a working CT string, and the newest taper technology that transitions through four nominal wall thicknesses within couple hundred feet, –have been found to maximize lateral reach capabilities and service life in extended reach operations. The inclusion of the latest technologies on extended reach tools and fluid additives is a must to maximize friction reduction and wellbore cleaning at rates of over 4 BPM and working pressures of over 7,000 psi.
These industry records demonstrate that the potential for longer laterals is far from being exhausted. Technological innovations on surface equipment, downhole tools, CT materials and highly engineered strings configurations, along with refined operational practices and logistics, are required to perform safe extended lateral completions on a larger scale.