Research On The Working Mechanism And Stick-slip Control Method Of A New Type Of Torsional Vibration Tool

With the continuous development of the world economy and the continuous improvement of people's living standards,the demand for energy was also increasing.The current development of conventional oil and gas fields has been unable to meet people's demand for energy.The global oil and gas exploitation was developing rapidly from shallow to deep and land to ocean.However,with the increasing of oil and gas mining depth,strata structure will become complicated,such as the geological environment of formation pressure,the rock drillability and uncertainty,which caused the drill string system to produce vibration in the form of circumferential,transverse and longitudinal.The harms of the stick-slip vibration were most serious.It greatly accelerated the failure of drill string and drill bit,caused the failure of ground equipment,resulted in downhole accident,which seriously affected the bit drilling speed and increased drilling cost.In order to effectively solve the stick-slip vibration,firstly,a new torsional vibration tool was proposed and its structure was designed in this paper.Secondly,the kinematics of the tool was studied.Thirdly,a nonlinear dynamic model of drill string system based on this tool was established,and the effect of viscosity reduction of the tool was further studied combined with the kinematics research results of the tool.Finally,the influence of the viscosity reduction of the stick-slip control method on the new torsional vibration tool was studied.Sliding mode control,PID control and coupling sliding mode PID control were designed respectively,and the control performance and robustness of each controller were compared.The main research content was as follows.1)Combined with the current research status of hydraulic shock apparatus at home and abroad,a new type of torsional vibration tool was designed,and the working principle of the tool was introduced.Compared with the existing tools,the tool could use the energy of the drilling fluid to drive the turbine axis to rotate,and then drive the disk valve structure to run.According to the characteristics of the disc valve structure and the cover plate,part of the drilling fluid will enter the internal sector cavity of the impact chamber periodically from the two areas,which will drive the impact hammer to impact the impact seat.It will form a periodic impact torque to change the rock breaking torque of the bit,thus restraining the stick-slip vibration of the bit to a certain extent and improving the drilling efficiency.2)The kinematics of a new torsional vibration tool will be studied.According to the location relationship among the disc valve structure fan hole,cover plate fan,the impact hammer and the impact seat of the new torsional vibration tool,the kinematics equation of the overcurrent area and the impact hammer was established.The variation of the overflow area,the angular velocity and the angular displacement of the impact hammer were obtained.Meanwhile,based on the collision relationship between impact hammer and impact seat,the variation of impact torque with time under different inlet flow was obtained,and the collision frequency was analyzed based on this.3)A drill string dynamic model with or without a new torsional vibration tool was established.The theoretical derivation of the dynamic equation of the drill string was carried out with or without a tool.Then the angular velocity and angular displacement of each component of the drill string system with or without tools were compared and analyzed at the given speed of the top drive.At last,the angular velocity of drill bit with or without tools was studied under different drive speed,different viscous damping and different drilling pressure.The research showed that increasing the turntable speed,properly increasing viscous damping and properly reducing drilling pressure could restrain the stick-slip vibration of drill string to a certain extent,and the new torsional vibration tool has an obvious viscosity reduction effect compared with no tools under the same conditions.4)On the basis of the drill string system model with a new torsional vibration tool,the effect of viscosity reduction of the stick-slip control method was studied.When drilling parameters were disturbed,drill string system may exhibit vulnerability,resulting in stick-slip vibration.Based on this,two sliding mode control methods and two PID control modes were designed respectively.Combining the control equations and given parameters,the viscosity reduction effect and the stability of the four control modes were analyzed.The results showed that the four control methods could effectively control the stick-slip vibration phenomenon of drill string system.Then,the control performance and robustness of each controller were compared,and the simulation analysis was carried out from the interference of different tracking speed and turntable respectively.The results showed that the overall performance of the sliding mode control equation U2 and the PID control equation U4 were better than the U1 and U3 control equations.But by comparing the sliding mode control equation U2 and the PID control equation U4,it was known that the robustness of U2 was stronger and the response ability of U4 was faster.Finally,combined with the advantages and disadvantages of the two types of control mode,the coupling sliding mode PID control mode was designed,and the simulation analysis was carried out.The analysis showed that the robust and response ability of the coupled sliding mode PID control method was better than the separate sliding mode and PID control mode.In summary,based on the basic structure and principle of the new torsional vibration tool,the working mechanism of the tool was studied by establishing the kinematics and dynamics model of the tool.The influence of the new torsional vibration tool on the stick-slip vibration was analyzed and compared,and the stick-slip control method was studied based on the drill string model with tools.The research results provided a theoretical basis for the later indoor and downhole experiments of the new torsional vibration tool,and provided a reference for restraining the stick-slip vibration of the drill bit.