Causes and countermeasures of drill pipe spring-back during pipeline backtow

During pipeline backtow of HDD operations, the spring back distance of drill pipe may exceed the range of drilling rig tongs after drill pipe is unloaded. Under such circumstances, it is necessary to install the additional transition collar for secondary backtow operation. In addition to increasing operation risks, such operation may significantly reduce work efficiency. Through analyses, root causes for spring back of the drill pipe can be determined as follows: elastic deformation of the drill pipe under significant backtow stresses and the actual diameter of the borehole may be significantly larger than the theoretical diameter upon completion of multiple reaming operations. With consideration to tests and field practices, conventional methods and countermeasures to eliminate spring-back of the drill pipe have been proposed as follows: applying suitable basket heights, deploying proper counterweight, excavating transmission trench, enhancing lubrication performances of the drilling fluid, and promoting the quality of reaming operations. In addition, by using the pipe thruster, stresses on the drill pipe induced by the horizontal directional drilling rig can be reduced; deployment of designated stop devices for drill pipe spring back may avoid the secondary backtow to enhance work efficiency.