Friction reduction measurement for a coiled tubing working in a marine riser

•Experimental and computational study on friction reduction between CT and riser.•CT with bigger diameter can help reduce friction.•Injecting velocity would not affect the friction.

Due to friction loss, the injection force applied on the Coiled Tubing (CT) would be unable to completely transfer onto its end. In that case, CT might be stuck in the riser which would finally make the operation failed. This paper proceeded experimental and computational study on ways to reduce friction between CT and riser to ensure the safety and reliability of the operation. Results show that inner pipe’s axial force transfer efficiency will decrease with the increasing of annular clearance, but injection velocity has almost no effect on inner pipe’s axial force transfer behavior. Thus in order to make the inner pipe transfer more axial force to its bottom end, CT with bigger diameter should be used during the operation. The research done above might provide important theoretical supports for the marine application of CT.