The Post-buckling Mechnical Analysis And Experimental Study Of Coiled Tubing In Sidetracked Wells

With the advantage of not shut-in operation, improving the degree of automation ofdrilling and achieving the closed-loop drilling, coiled tubing technology has become a hotspot in domestic and international drilling applications. Because of its low stiffness, coiledtubing prone to bending instability easily in the decentralized or drilling process, causingdrilling operations fail to function properly. Therefore carring out the post-buckling analysisand experimental study of coiled tubing in sidetrack has important engineering significance.According to the deformation and force characteristics of the slim column buckling inthe tube, the article selects the slender column and the tube for the study, takes the iterativecalculation method to describe the entire change process of the buckling and post-bucklingbehavior and establishes a numerical method of buckling of slender column in the tube.Considering the contact of the double pipes inside and outside, the indoor test bench of theslender column buckling in the vertical tube is established to study the critical load ofdifferent column diameters when sinusoidal buckling and helical buckling occurs, and obtainsthe axial displacement and friction of the column under different axial force. The axialdisplacement of the column increases with increasing axial load and the change issubstantially linear. The column friction increases with increasing axial load and the stage ofhelical buckling increases faster than sinusoidal buckling phase. A finite element model of theslender column buckling in the tube is built, the critical buckling load of column and therelationship between the axial displacement and axial force is obtained. The critical loadvalues obtained respectively by the theoretical formulas of literature、the tests and thenumerical simulation is compared and all the three agree with each other, test values betterverify the correctness of the theoretical formulas and numerical models. Application columnbuckling finite element method, to establish a post-buckling mechanical model of coiledtubing in directional sidetrack wells. To calculate it, the axial force、axial displacement andfriction resistance of the coiled tubing post-buckling in directional sidetrack wells is obtained,which can provide a theoretical basis and guidance for construction site of coiled tubing.