Research and application of reaming subsidence control in horizontal directional drilling

In the reaming operation of horizontal directional drilling, a centralizer is often attached to a reaming-bottomhole assembly (R-BHA) to change the reamer side force. This can address the problem of large-diameter reamer subsidence. However, there is no scientific basis for how to attach the centralizer in the R-BHA. In this paper, an equation for the reamer side force in a two-centralizer R-BHA is derived, based on three moment equations. Then, using the Drucker-Prager criterion as a rock constitutive relation and the shear criterion for predicting damage initiation, a nonlinear dynamic finite element model is established using the finite element method (FEM). In addition, the trajectory of the reamer and the failure of the drilling tools are analyzed. The study results show that the combination of the analytical and finite element methods can effectively improve the installation accuracy of the centralizer. The attachment range of the centralizer can be quickly determined by a simple calculation of the analytical method, and the FEM (with high computational precision) can be used to analyze the subsidence control capacity of the R-BHA in detail. Application to a field case demonstrates the feasibility of the method, and the study conclusions provide a scientific basis for the centralizer attached to the R-BHA, which is important for controlling reaming subsidence.