Tracking Control Method Of Geological Directional Drilling Trajectory Based On Drilling Tool's Attitude Control

With the exploration and excavation of deep mineral resources and energy,in-depth geological exploration and development have become inevitable.However,the deep geological environment is complex,with high temperature,high pressure,high formation,and mining disturbances,making the drilling process more difficult.Meanwhile,there is a lack of drilling tools' motion model and drilling trajectory model that consider actual working conditions and the appropriate control strategies.The development of the drilling system automation is limited,and the drilling trajectory is difficult to achieve the desired control effect.Since the control of the drilling tools is the basis for forming the directional drilling trajectory,the article starts from the movement modeling and management of the drilling tools and analyzes the drilling tools' movement process.A control strategy is proposed for the attitude of directional drilling tools.Then,the evolution process and formation mechanism of the drilling trajectory is analyzed,and a drilling trajectory model is established,and the drilling trajectory is only tracked.Thus,the trajectory azimuth directly determines the borehole's quality,and single-loop trajectory azimuth control is discussed.Finally,the weight-on-bit uncertainty increases with the deep strata change,the robust control considering the weight-on-bit uncertainty is studied for the drilling trajectory.The main research results and innovations of this dissertation are as follows:(1)Attitude control of directional drilling tools using the PI compensator.Drilling tools are the carrier that formed by the drilling trajectory,so the directional drilling trajectory needs to be realized by the directional drilling tools.The movement process of the drilling tools is complex and non-linear,and it is difficult to effectively control the drilling tools' attitude.A control strategy with a PI compensator is proposed for the attitude of directional drilling tools.Firstly,the movement process of the drilling tools is analyzed,and the movement mechanism of the drilling tools is clarified.So,the drilling tools' movement model is established;Thus,Taylor expansion and bilinear approximation transformation are used to deal with the non-linear terms existing in the movement model of the drilling tools.It will simplify the motion model of drilling tools.The idea of industrial compensation control is introduced,and the compensator is combined with the PI controller to form a PI compensator.The PI compensator can achieve accurate control of the drilling tools' inclination and azimuth,respectively.The simulation experiments were carried out in two aspects: no compensator and based on compensation control.The results show that this strategy improves the accuracy of directional drilling tool control.The system structure design is simple,the system stability is strong,and the project is easy to operate and realize.Therefore,the control method has better practical value.(2)Observer-based trajectory control for the directional drilling process.Although the drilling tools' movement forms the drilling trajectory during the drilling process,the drilling trajectory is also affected by bottom hole assembly,bit/rock interaction,and borehole friction.The trajectory inclination angle with azimuth and bottom hole assembly(BHA)inclination with azimuth is not precisely equal in the actual engineering.Existing research results all default that the actual trajectory inclination and azimuth are the same as the BHA inclination and azimuth,but this will bring some errors to the trajectory control.It results in the inability to achieve accurate control of the drilling trajectory.An observer-based control strategy is proposed to induce control errors for directional drilling trajectory.First,the drilling trajectory's evolution process is analyzed,and the relationship between the trajectory inclination with azimuth and the BHA inclination with azimuth is clarified.So,the drilling trajectory model is established.Next,the variable transformation technology is used to transform,and it makes the above model into a model suitable for control.Then,a dual-loop closed-loop control system based on an observer with compensation control is designed to realize tracking control of the drilling trajectory.Thus,system stability is analyzed in detail,and the controller parameters and observer gains are obtained.Finally,a typical case illustrates the correctness and effectiveness of the control strategy.(3)Azimuth control of directional drilling trajectory with time delay and angle coupling.The drilling trajectory azimuth directly determines the deviation direction of the drilling trajectory and also determines the borehole quality.So,the trajectory azimuth control is essential.By analyzing the drilling trajectory model,there is a coupling between the trajectory azimuth and the trajectory inclination.Meanwhile,the change of the trajectory azimuth has hysteresis characteristics.A control strategy is proposed to solve the problem of the time-delay and angle coupling of directional drilling trajectory azimuth.According to the azimuth model of the drilling trajectory,the state-space model of the trajectory azimuth is established;the equivalent-input-disturbance-based structure of the trajectory azimuth control system is designed;the internal model of the control system is used to track the change of the trajectory azimuth;a state observer with a first-order lowpass filter is used to estimate the trajectory azimuth based on the measured BHA azimuth.Next,the conditions of system stability are obtained through the form of LMI,and the control parameters are obtained from the stability conditions.Finally,the effectiveness of the strategy is demonstrated through numerical simulation.(4)Robust control of directional drilling trajectory with weight-on-bit uncertainty.Weight-on-bit is a significant factor that affects the directional drilling trajectory,and its fluctuation directly affects the formation of the drilling trajectory.To effectively and accurately track and control the drilling trajectory,a robust control strategy is proposed for the directional drilling trajectory considering the weight-on-bit uncertainty.By analyzing the drilling trajectory evolution model,the variable transformation technology is used to simplify the model.A state-space model with weight-on-bit uncertainty is established for the drilling trajectory system.Based on the idea of equivalent-input-disturbance,two closed-loop control loops are designed to control the trajectory inclination and trajectory azimuth,respectively.There are some modules in the trajectory system,such as the internal models are used to track the trajectory inclination and trajectory azimuth,respectively,the estimator is used to describe the estimation error,and the observer is used to obtain the state quantity of the trajectory inclination and azimuth,respectively.A closed-loop control state equation with separated uncertain terms is formed.A suitable Lyapunov function is selected to analyze the system stability,and the system stability is explained in the form of LMI.The control parameters and observer gains are obtained based on the stability conditions.A typical example is used to discuss the disturbance suppression of the strategy in the build-up segment and horizontal segment of the planning trajectory.It shows the method's effectiveness and robustness.