Mechanical Analysis of Drill Strings in Horizontal Directional Drilling

摘要

A large number of failure cases on horizontal directional drilling arise from complex forces, difficult mechanical analysis and lack of theoretical basis of construction parameters. So it's of great engineering value to make mechanical properties of horizontal directional drilling clear.The mechanical analysis models of directional drilling and completed-pipeline in three working conditions of drilling guide hole, expanding hole and pulling back completed-pipeline are established in this paper with the synthetical consideration of well structure, BHA, service environment, mechanic and process parameters. The spatial deformation curve of tubular string is fitted by spline function, and the deformation curves of tubular string in suspending and horizontal section are acquired by weighted residual method and elastic foundation beam method separately. In addition, with the consideration of support and subsidence, the tangent points of tubular string in suspending section and shaft lining are analyzed. Position of weakest point, failure reason of drill string in horizontal section and choice rules of roller centralizer and connector are determined based on above research. Also, the security of drill string in horizontal section is validated by two-criterion approach. The conclusions drawn from the paper have great guidance effect on engineering application.