Drill String Vibration Analysis And Monitoring Device Design

In drilling process,the longitudinal vibration,transverse vibration,torsional vibration and coupling vibration happen in drill strings,which often make the drill internal force and the WOB fluctuating in large ranges.This case not only slows the drilling speed,but also causes wear and fatigue failure of the drilling tool,even breakes the drill strings.The drill string vibration analysis and monitoring device design play significant roles in preventing and reducing the damagement of the drill string.Based on the typical mechanical model and the vibration equation of the longitudinal vibration,transverse vibration,torsional vibration of the drillstring,this article establishes the method of using the vertical vibration acceleration,transverse vibration acceleration and torsional vibration acceleration to describe the drill string vibration.Select the whole revolving drill string as the research object,and fully consider the effect of theWOB,torque and the contact between the drill strings and the wellface,then set up the drill string vibration dynamic model.Based on the model,do nonlinear transient dynamic analysis witn the finite elements,use gap elements to simulate the contact between the drill string and the wellface,and establish the nonlinear dynamic finite element method.Design the drill string vibration monitoring device.The device is divided into three units and has the functions of vibration testing,intelligent distinguishing and alarm controling.when the outside and inside diameter of the main valve are 30mm and 12mm,triggering device can produce 3.94MPa pressure which ensures the availability and effectiveness of the mud pressure signal.Deduce the mathematical relationship between the six accelerations and the three accelerations to determine the spatial location of the accelerometer.Analysing the dynamic model of solid and beam element not only verifies the correctness of the location of the accelerometer,but also gets the number of the accelerometer used in the monitoring device.In the conditions that there is only longitudinal vibration or only torsional vibration in the drill strings,one accelerometer is enough for testing.In transverse vibration,two accelerometers are needed.In coupling vibration,three accelerometers are enough.Based on the drill string vibration fatigue failure theory,point to the lower drill tool as the research object,to do fatigue failure analysis to the dynamic model.Through the analysis,get the placement of the drill string vibration monitoring device.When the WOB are 9t,12t,15t,18t,the device should be placed at 50m,23m,34m,50m away from the bottom which has a guiding significance for engineering application of the drill string vibration monitoring device.This paper researches play important roles in developing the drill string vibration failure prevention and the down hole monitoring equipment design.The drill string vibration monitoring device has a wide application prospect in real time monitoring the drill string vibration of the oil field.