Study On Key Manufacturing Technologies Of Coiled Tubing

With the increasing demand of the lateral drilling and slim hole drilling, the coiled tubing (CT) operating technique will play a great role in horizontal well drilling, well workover and completion. But our research on the manufacturing technologies of CT units is still blank in China, which results in the tubes used in China are dependent on foreign imports. Therefore, the researches of coiled tubing operating technique and product development have become a top priority to replace imported products and meet the oil development market.In this thesis, a new effective manufacture method of coiled tubing, integrating dozens of forming processes, is proposed and the key processes, Cold Roll-Forming (CRF) and Stretch-Reducing (SR) will be the main research direction.In the forming process from the bland steel to the tube, the forming parameters directly affect the quality of the finished tube. Then parameter setting is always arduous and empirical. Analysis of the deformation process, from which the stress and strain distribution can be obtained, has great theoretical and engineering significance for the parameter design.The roll pass design in CRF determines whether the band steel is bended homogeneously with no defect. For CRF mill, roll amount, roll pass and stand spacing are calculated according to the Dual-radius Bending Method. The initial condition, boundary condition and contact condition are given to establish the CRF finite element model. The numerical simulation result shows that the bland passes through all the rolls successfully without any defect. Then, the deforming rule of the band steel and the distribution of the stress and strain are obtained, which can provide a theory basis for designing the welded pipe forming process.The roll pass parameters and roll rotational speed of the SR machine directly decide the tube tension between rolls, and also influence the tube deforming process and its quality. For the SR machine, the oval groove and stand spacing are designed. Tension coefficient and roll rotational speed can be attained by giving the diameter reduction of each stand. After finite element analysis of the coupled thermo -mechanical models of tube tension reducing, the tube deforming rule, the temperature change and the distributions of stress and strain are gained. In the end, nine SR models with different initial tube thickness are established and simulated, to summarize the causes of the unevenness of the transverse wall thickness of stretch-reduced tube and the formation of bore polygon.