Research On The Steerable Control Method Of Controllable Drill Bit

Rotary steerable drilling tool is an advanced equipment used to control the well trajectory.It has become the most effective tool to exploit unconventional oil and gas resources,among which the push-driven steerable drilling tool that uses push-driven actuator to push against the wall is the most widely used.However,the lateral force of the bit controlled by this tool is not only related to the size of the push force,but also closely related to the position of the push force.Due to the large distance between the push actuator and the bit,the actual lateral force is less than the push force,which affects the control effect of the well trajectory.If the cutting structure and pushing actuator can be integrated,the position of pushing force can be moved forward to the bit face,and a kind of steering bit with controlled expansion of cutting blade can be developed,it will undoubtedly improve the ability of steering tool to control the well trajectory.Focusing on the development of the controllable bit,the main research contents and stage achievements of this thesis are as follows:(1)The interaction between PDC(Polycrystalline Diamond Compact)bit cutters and rock was analyzed,the "elliptic non-uniform pancake" model of controllable bit inclined drilling was constructed,and the mechanism model of controllable bit steered drilling was established.The calculation shows that the controllable bit can improve the building slope by about 26%compared with conventional push-back guided drilling tools when the push force is the same.(2)Referring to the working principle of expansion reaming bit,the mechanical structure scheme of controllable bit is proposed.According to the general requirements of drilling engineering,the hydraulic cylinder structure driving the controlled blade is designed,and the characteristic parameters of the controlled blade such as pushing force,extension/contraction movement distance and movement speed are calculated.A hydraulic distributor with four flow channels and a hanging disc valve are designed to control the pressure of the hydraulic cylinder and drive the extension/retract of the controlled blade which rotates rapidly with the drill string.(3)Adopting the angle-velocity double closed-loop control system structure,the Angle position control system of the stable platform is designed to drive the hanging disc valve fixed to the stable platform to stabilize at a specific Angle position.According to the nonlinear dynamics model of the controllable bit stabilization platform,a cascade PID control method for the stabilized platform was proposed.The simulation was carried out by Matlab/Simulink simulation tool.The simulation results show that the stability control of the platform can be realized by using PID control under the action of strong disturbance.Circuits such as signal processing,main control module and control driver module are designed,and corresponding functional programs such as signal acquisition,Angle calculation,control operation and control driver are written.Through the sensor calibration,system integration,function debugging and other design work,the development of the principle prototype of the measurement and control system is preliminarily completed.The functional test results of the prototype show that the design of the measurement and control system is reasonable.These studies are expected to improve the performance of guided drilling tools in steering accuracy and efficiency,borehole smoothness,and reservoir penetration.