Research On Dynamic Modeling Of Sucker-rod Pumping Process And Optimization For Frequency Of Stroke

Sucker-rod pumping system is the most widely used in domestic and foreign oil wells, and it is also overwhelmingly dominant in the ways of mechanical oil artificial lift methods. Because the rod pump beam pumping unit has these advantages including the simple structure, the reliable operation, the easy maintenance, and long-term continuous operation in serious conditions, etc. It is widely used in oil exploration process. Sucker-rod pumping system includes three components:a pumping unit, sucker rod and pump. In China existing holdings of various types of pumping is more than two hundred thousand. Rod pump beam pumping unit is the most widely used oil pumping equipment on the ground.Firstly, the theory of existing beam pumping unit’s work is introduced. The conventional beam pumping unit kinematics and kinetic parameters of rod load is detailedly analysed. The inflow performance relationship is analysed. The process of pump working is analysed, and the calculation methods of fluid flow and related pressures are given.Secondly, simulation program with the above model by Matlab is compiled. Hanging beam pumping unit displacement, velocity and acceleration are simulated; the inflow performance relationship of oil well is simulated; liquid inflowing into and discharge of the pump chamber in a cycle are simulated; then the dynamic fluid variation of surface in longer dimension is simulated. Through these simulations, the process of liquid from the reservoir flowing into the well, and then discharged to the outside through the well pump is completely given.Finally, the liquid level changing model is aimed to support the optimization for the frequency of stroke of the pump, and the mathematical model of the optimization for frequency of stroke is developed. According to different optimization objectives, it is needed to construct the function of maximal oil production target and the function of optimal economic target, respectively. Constraint conditions of the optimization for the frequency of stroke have been studied, including the constraint of forecasting of the fluid level and the error rate of the pump when motor running under a large load for a long time range. The examples of oil production and economic before and after optimization calculation are compared, and it proves the optimization method is playing a very significant role in improving production efficiency.