Research On Dynamics And Drilling Control Of The Slide Drilling System

Slide drilling system is widely used in directional drilling engineering because of its mature technology and low cost.However,the high slenderness ratio of the drill string and the complex bottom hole environment make it difficult to predict the drilling trajec-tory accurately.And the operation during the process of drilling mainly relies on the artificial experience of directional engineers and drillers resently,which leads to a long time consuming.The problem of low drilling efficiency needs to be solved urgently.In this paper,a segmentation modeling method is proposed to evaluate the bottom hole as-sembly(BHA)steerability efficiently and accurately by using the multi-body dynamics method and considering the complex bottomhole environment.A feedforward control system based on the dynamic model was proposed to control the BHA drilling according to the planed well trajectory,which is applied to automating the work of directional engi-neers and drillers,and achieving the aim of efficient slide drilling.The research work of this paper is as follows:1.Established a “whole drill string” multi-body dynamic model of the slide drilling system based on an Arbitrary Lagrangian–Eulerian(ALE)formulation.The governing dynamic equations of the whole slide drilling system,combined with the system con-straint equations,contact equations,wellbore update equations,is used to model and sim-ulate the directional process.This model provides a straightforward assessment of the dynamic characteristics accurately.The computational efficiency is higher than that of the traditional “whole drill string” model based on Lagrangian formulation.2.Proposed a multi-body dynamic segmentation model of slide drilling system based on the “whole drill string” model.The degree of freedom(DOF)of drilling system is greatly reduced by decoupling the BHA drilling process from the drill string balance pro-cess.Segmentation model provides a new approach to improve the efficiency of the slide drilling simulation under constant control condition while ensuring the accuracy.This model also can be used to evaluate the BHA steering ability in different control and for-mation conditions efficiently and accurately,which has a high application value in drilling engineering.In addition,the proposed method can be extended to conventional rotary BHA and rotary steerable system,whose steering drilling process can be simulated effi-ciently.3.Proposed a feedforward control system based on the segmentation model of slide drilling system,combined with shooting method and quasi-Newton method,which can calculate the rig control variable that controls the BHA drilling according to the target trajectory.The feedforward control system provides a new way to automate the work of directional engineer and driller,enabling accurate and efficient automatic slide drilling with known drilling system model parameters.The performance of the presented feed-forward control system were varified to satisfy the requirements of field operation by four numerical examples and three simulation tests,based on the in-field experimental data.