Helical Buckling and Lock-Up Conditions for Coiled Tubing in Curved Wells

Abstract

Abstract An improved formula for critical buckling loads has been derived. This formula, which takes the well curvature into account, has been verified in small scale laboratory tests. The theory has been applied to survey data from a real horizontal well and it predicts that the well curvature substantially affects the critical force for helical buckling, and thereby also the maximum run-in length of coiled tubing. Criteria for operational limits, such as lock-up and tubing failure, are also discussed in the paper.