Optimization Design And Vibration Characteristics Of Shock Absorber For Cylinder Type LWD Tool

With the development of science and technology,LWD(Logging while drilling)plays an increasingly important role in oil drilling and production equipment.It can not only guide the drilling and production work by monitoring the real-time geological information in the well,but also improve the drilling and production efficiency and ensure the life safety of the staff in the face of drilling and production of relatively difficult deviated wells and horizontal wells.Logging while drilling tool is installed on the measurement short section near the bit.When drilling,it is not only affected by the external complex working environment,but also by the mechanical property of the drilling and production equipment itself.It can be seen that it is of great significance to reduce the vibration and improve the accuracy of measurement for effectively improving the drilling efficiency.At present,the vibration damper of LWD in China mainly adopts rubber ring structure,and its vibration damping performance and service life are limited.1.The structure of LWD tool is analyzed.The mechanical model is established,the various loads are analyzed,the optimal design scheme of the shock absorber is determined,and the basic design and analysis of the structural optimization are carried out through the calculation of the structural parameters of the shock absorber.2.Based on the Hertz contact theory,the contact model between the sphere at the top of the damping block and the cylinder of the outer shell is established to analyze the variation law of the contact area under the action of external loads.Referring to the working principle of the cylinder spring damping device,the contact variation law of the damping block is studied when the ball at the top of the damping block is in contact with local sliding,and the analytical method is used to analyze the contact variation law of the damping block when the axial force and tangential force change simultaneously.Based on the contact analysis of the damping block,the stability calculation method of thermo-mechanical instability in the sliding process is proposed.Referring to the Iwan parallel series model,the dry friction micro-slip of multiple spring dampers in the cylinder spring damping device is studied,the vibration equation of micro-slip is established,the dimensionless friction of the damping block is analyzed,and the sliding displacement value of each damping block is solved analytically at any moment.According to the theory of P and Q’s fixed point in thedesign principle of dynamic shock absorber,the optimal damping ratio of cylindrical spring damping devices studied.3.Based on the finite element method,ANSYS simulation software is used to conduct modal analysis,harmonic response analysis and random vibration analysis on the spring vibration damping device of the drilling-while-drilling tool,so as to obtain the basic dynamic characteristics of the vibration damping device and the frequency region of resonance response.4.Multibody system dynamics simulation with ADAMS software,combined with the influence factors of transverse vibration and torsional vibration,compare the three kinds of working conditions,the original structure of drilling tools and install the cylinder while drilling tool spring damping device of drilling tool vibration characteristics,to determine in this paper,the design of vibration reduction device damping effect is better,less affected by rotation speed.