Numerical modelling and field experimental validation of the axial load transfer on the drill-strings in deviated wells

This paper studies the axial load transfer along the drill-strings in deviated wells by developing a finite element model based on the Euler beam theory and the augmentation Lagrangian contact algorithms. The model can simulate the entire drill-strings showing nonlinear contact model between drill-strings and casing. Special attention is given to the axial load loss, the pipe-casing contact force distribution and the slender pipe deformation. The efficacy of the proposed model is validated experimentally using a packer releasing procedure. Various drill-string factors, such as deviation angle, dogleg severity, hook load magnitude and buckling configurations, are considered for evaluating the efficiency of axial load transfer. Our analysis shows that the dogleg severity has a significant influence on the transfer, and the helical buckling of the drill-strings due to excessive loading could make it worse. This study provides a theoretical understanding of the variation of the contact force and the axial load transfer for the drill-strings in deviated wells. It can be used to better understand the working condition of downhole and guide field drilling.