Experimental study on axial load transfer behavior of a coiled tubing stuck in a steel catenary riser: At the stage of the coiled tubing un-helical buckled

Abstract

Coiled tubing can be used for steel catenary riser pigging operations to remove wax and other debris attached on the interior of steel catenary riser to recover production and ensure safety. Due to its low rigidity, coiled tubing would deform which might finally damage coiled tubing and steel catenary riser. Thus, in order to ensure safety and reliability of the operation, this article proceeded experimental study on the axial load transfer behavior of a coiled tubing stuck in a steel catenary riser when the coiled tubing has not yet helical buckled. According to the experimental results, the inner pipe’s axial force transfer efficiency is always less than 1; the outer pipe of “unfixed steel catenary riser boundary” would elongate forced by the inner pipe within it, which makes the injected displacement of inner pipe within outer pipe of “unfixed steel catenary riser boundary” bigger than the injected displacement of inner pipe within outer pipe of “fixed steel catenary riser boundary” system at the same force-out; before the inner pipe helical buckles, inner pipe’s force transfer efficiency for unfixed and fixed system can be considered as the same. The research done above might provide important theoretical supports for the steel catenary riser pigging operation.