Software Development Of Wear Life Prediction Model For Rod String And Tubing String In Straight Welland

As the core equipments of rod pumped well, rod string and tubing string sufferscomplicated and long-time alternating loads in use. Once rod string or tubing string is outof work, the well cannot work normally, and crude oil production will be affected,whichwill influence the oil field’s profits. At present, since the pump checking period cannot bepredicted, wokers can seldom carry out planned pump checking,hence they usually checkpumps after incidents. From the record of pump inspection, we know that the failure of therod string and tubing string is the main cause of the failure of the well. For straight well,the main cause leading to failure is eccentric wear of rod and pump. To counter theproblem of straight well’s failure, this paper mainly studies the following contents:Based on actual pump checking records, the paper counts and classifies the failuresof straight well sucker rod, tubing and pump system. Pump checking period regressionmodel and influential factor sensitivity model for straight well are established based onmultiple element nonlinear theory. Pump checking period prediction for single-well isachieved. Failure rate model of straight well is built and is used to perform failure riskevaluation, risk level evaluation and prediction of the number of failed wells.Mechanical models of rod string and tubing string are established by analysing axialforce of rod string and tubing string. Considering restraints of suspension center and pumpload, mathematical model and axial loading simulation model of rod string and tubingstring are built applying wave equation theory.Based on static force balance method, the spiral buckling configurations and thealgorithmic methods for the contact pressure between rod string and tubing string aregiven respectively. The paper analyses various factors’ influence on normal force forpolymer flooding well. Mechanical model and mathematical model of buckling rod arebuilt with normal force. And then algorithmic model of the contact pressure between rodstring and tubing string is given under normal force based on wear energy theory. Usingthe ANSYS finite element analysis(FEA) software, the paper analyses maximumequivalent stress of rod and tube worn. And then regression models between maximum wear depth and stress concentration factor are given. Based on fatigue damage theory, lifeprediction models of rod and tube are proposed.The corresponding software for straight well life prediction and simulation of wornrod and tube is programmed applying Visual Basic6.0. Using the software, the paperevaluates failure risk and forecasts the number of pump inspection. And then it analysesthe pump inspection regression model and influential factor sensitivity of pump inspection.At the same time, the paper simulates straight well spiral buckling configurations andcontact pressure between rod string and tubing string. Concerning normal force, thesoftware analyses its influential factors and its influence on rod string buckling. At last,the software does life prediction for rod string and tubing string, providing theoreticalfoundation for reasonable planned pump inspection.