A Study On Dynamic Characteristics Simulation And Control Of Bias Mechanism Of Point-the-Bit Rotary Steering System

As the world’s most advanced directional drilling tool,rotary-guided drilling tools generally control the borehole trajectory and can significantly improve drilling efficiency during directional drilling.Foreign countries have long had a series of commercial rotary guide drilling tools,but the domestic research started late,in order to break the foreign technology monopoly,urgent need for in-depth research and design of rotary guided drilling tools.This paper selects the point-the-bit rotary steering system for research.The specific research work is as follows.(1)Mechanical analysis of the mandrel was carried out,and the formula for the relationship between the force and the bending deflection is derived.And through the combination vector of the offset vector of the inner and outer eccentric ring of the deviation of the mechanism,the central component expression of the mandrel and the motion trajectory formula of the center of the mandrel at the eccentric ring are obtained.(2)The simplified geometric model of the point-the-bit rotary steering system is imported into ADAMS virtual prototype software,and finite element dynamic simulation model is established,the simulation and external eccentric ring trajectory and the relationship between triangle function,and use the mandrel central component expression calculated the theoretical offset component under different conditions,compare the theoretical value and the ADAMS software simulation obtained numerical solution,the relative error of 80.56% data is less than7%,which verifies the feasibility of deriving trajectory formula in engineering application.(3)This paper obtains the formula for the motion trajectory of the inner and outer eccentric ring after determining the bit deflection angle and the tool surface angle.And program the solution and optimization of the motion trajectory of the internal and external eccentric ring,to quickly reach the target tool surface,shorten the adjustment time of the internal and external eccentric ring,and improve the working efficiency of the system.Then the simulation of the simulation result is less than 2%,it proves the feasibility of both the simulation and the design of the motion loop.(4)The formula of the relationship between the bias force of the mandrel,the lateral force of the bit and the bending deflection of the mandrel is derived,so as to realize the solution of the lateral force of the bit.ADAMS software was used to simulate the virtual prototype of the directional guidance tool,and it was found that the relative error between the calculated and simulated results of the bearing support reaction force was less than 8%,and the average error between the theoretical and simulated values of the bending deflection of the mandrel was only7.68%(without considering the deformation of the mandrel at the two end bearings).This demonstrates the feasibility of using the mandrel deflection equation in practice.The above conclusions provide theoretical support for the precision guide drill bit drilling along the predetermined trajectory and the subsequent design and development of the point-thebit rotary steering system,which has significant practical applications.