Research On The Prediction Method Of Eccentic Wear Life Between Rod And Tube For Flooding Pumping Well

In recent years, with the constant improvement of the three oil production technology in China, the number of polymer-flooding well is increasing. The Polymer solution is power-law fluid, eccentric wear between sucker rod and tubing intensified with normal force caused by the produced liquid, the break off of the sucker rod and the accident of the oil pipe damage increase sharply compared with the water flooding well. Due to the inability to predict the maintenance period of the pumping unit, oil field mostly used the method of pump-testing afterwards, the economic benefit of oil field has been seriously affected. According to the actual situation of oil field, the statistical equation of the pump cycle is obtained by using the statistical method of multiple regression, then the actual stress situation of polymer flooding well is analyzed, the prediction of polymer flooding pump detection period of pumping wells by using the method of theoretical analysis, it is of great significance to the actual production of oil field. This paper mainly studies the following contents:According to the actual production data of oilfield, based on multiple element nonlinear theory, pump checking period regression model is established by use of the MATLAB software, it realized the prediction of single well pump cycle. Significance test for the regression equation and regression parameters respectively, using of Weibull distribution of three-parameter, the prediction equation of pump cycle are optimized.Considering the axial friction between the rod and tube, based on the static equilibrium method, the helical buckling configuration of the rod string is established and the contact pressure of the rod is calculated. For polymer flooding wells, the influence factors on normal force are analyzed. The calculation model of the contact pressure between the rod and the tube is considered when the axial force and normal force are considered together. Analysis of the different combination of rod and tube case, change of maximum contact stress equivalent.Based on the wear energy theory, considering the wear depth change, establish calculation model of wear of rod tube. Based on the static strength theory, the life prediction model of the rod string is established. Based on the ANSYS finite element software, analysis of the change of stress with the maximum wear depth maximum equivalent damage of rod string, then solve the rod pipe damaged parts of the stress concentration coefficient and the relation between the maximum wear depth. Based on fatigue damage theory, the fatigue life prediction model of rod string is established.The corresponding software for polymer-flooding well life prediction and simulation of worn rod and tube is programmed applying Visual Basic 6.0. Using the software, we can analysis the effects of various parameters on the production cycle of pump inspection, and we can realize the simulation of polymer flooding well rod helical buckling state and rod contact pressure calculation.The software 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 theoretical foundation for reasonable planned pump inspection.