Abstract
Mechanical automatic vertical drilling tools (MAVDT) have gradually gained attention as a drilling tool that can achieve active correction in harsh working environments such as high temperature and high pressure. The gravity sensing mechanism can sense the deviation and convert the deviation signal into the control signal to drive the actuator to correct the deviation. It is the core component of the mechanical automatic vertical drilling tool. This paper analyzes the force on the gravity sensing mechanism based on the structural analysis of the mechanical automatic vertical drilling tool. Then, the general dynamic equation of the gravity sensing mechanism is established based on D’Alembert principle. The critical response position where the acceleration value is zero is used as the research object to complete the preliminary design and analysis of the sensing mechanism. Through analysis, it can be found that there is a conflict between the response accuracy and control stability of the gravity sensing mechanism. High response accuracy often means poor control stability. For the gravity sensing mechanism with definite structural parameters, there is a limit value of the allowable friction coefficient. When the friction coefficient of the thrust bearing exceeds the limit value, the gravity sensing mechanism cannot achieve the inclination response no matter how big the inclination angle and deflection angle are. The friction coefficient between the disc valves and the force between the disc valves of the gravity sensing mechanism have a linear effect on the performance of the mechanism, and the smaller the deviation angle, the greater the influence coefficient of the force or the friction coefficient between the disc valves on the length of the gravity sensing mechanism. During the process of dynamic swing, the dynamic stable position of the gravity sensing mechanism is related to the relative relationship between the restoring force of the mechanism and the friction damping. To be precise, it is related to the potential energy zero point and the speed zero point during the gravity sensing mechanism swing process before it reaches the dynamic stable position.
Highlights
As one kind of active hole straightening tool, automatic vertical drilling tool (AVDT) is thought of as an advanced vertical drill technology, which changes the traditional well trajectory control method. is new rotary steerable system for vertical drilling can prevent boreholes from deviating from vertical and correct inclined boreholes to verticality actively
E friction coefficient μP and the fluid normal force FP between the disc valves are two key factors that affect the performance of the gravity sensing mechanism by the disc valve control mechanism. rough the above analysis, it can be found that its influence on the length of the gravity block of the gravity sensing mechanism is linear, and the higher the response accuracy, the greater the impact
(2) e friction coefficient of the axial thrust bearing of the gravity sensing mechanism has an important influence on the performance of the gravity sensing mechanism. ere is a limit value of the allowable friction coefficient for the gravity sensing mechanism with certain structural parameters
Summary
As one kind of active hole straightening tool, automatic vertical drilling tool (AVDT) is thought of as an advanced vertical drill technology, which changes the traditional well trajectory control method. is new rotary steerable system for vertical drilling can prevent boreholes from deviating from vertical and correct inclined boreholes to verticality actively. Compared with the traditional electronically controlled AVDT, the mechanical automatic vertical drilling tool (MAVDT) can achieve continuous active correction under the action of gravity only through the pure mechanical structure. Since the high-precision and high-sensitivity electronic control system is abandoned, the deviation control only depends on the characteristic of the heavy block in the mechanical stabilized platform to maintain the low side of the well under the action of gravity, so the gravity sensing mechanism is a key component for sensing well deviation and controlling its actuator to achieve well deviation response. The working process of MAVDT is dynamic [14,15,16,17] It is generally installed near the drill bit and rotates with the bottom hole assembly during operation and will be affected by axial vibration, lateral vibration, torsional vibration, or other factors, which will affect the response accuracy and stability of the platform. Multibody dynamics is introduced and numerical analysis is used to analyze the motion characteristics of the gravity sensing mechanism under different initial conditions. rough the introduction of dynamics, the motion model of the gravity sensing mechanism is more reasonable, and the motion characteristics of the gravity sensing mechanism and the responding mechanism of well deviation can be further understood, and it is beneficial to optimize the structure of the gravity sensing mechanism and further improve the response accuracy and stability of the MAVDT
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