Research On Downhole Load Shedding Device Of Rod Pumping System

In recent years,in order to make pumping wells the pump setting depth can be deepened,reduce energy consumption,increase production,and reduce hourse head polished rod load,many oil fields in China have designed and applied pumping unit load shedding devices.However,there are great differences in the energy saving effect of the existing load shedding device.It makes use of the annular space pressure difference between the casing and the tubing to reduce the polished rod load of the pumping unit,but the load reducing device is limited by the pressure difference,so the energy saving effect of the load reducer is limited.In this paper,aiming at some shortages of the existing pumping unit load shedding device,a new kind of downhole load reducer scheme for the rod pumping system is proposed.According to the process requirements,the structural design of the downhole load shedding device for the rod pumping system is determined.The basic parameters of each component of downhole load-down device in sucker rod pumping system have been determined.And the statics analysis and dynamics analysis of downhole load reducing device have been carried out.The downhole load-down device has the advantages of energy saving,load shedding and deepening pump hanging.Moreover,the device has certain application value.This article mainly studies the downhole load reduction device of the pumping unit from the following aspects:(1)The scheme of downhole load reducing device for rod pumping system is established and its structure is designed.The key components are analyzed by finite element method.The downhole load reduction device is designed,and its working principle and function are introduced.The load shedding force and the static load at the suspended point are calculated theoretically to determine the installation position of the load reduction device in the downhole;the structural design of the downhole load reduction device is performed.Creo software is used to perform three-dimensional solid modeling of the components of the downhole load shedding device,and the role of each component is introduced.Finite element software ANSYS Workbench is used to analyze the static components and fatigue life of key components of the downhole load shedding device.(2)The dynamics of downhole load shedding device is studied.The whole downhole load reduction system and sucker rod string dynamics are studied respectively.The dynamic model of the downhole load shedding system is established and the differential equation of motion of the system is written.The wave equation is established to analyze the sucker rod string,and the wave equation of the sucker rod string is solved by the finite element difference method.(3)The system dynamic simulation model of downhole load reducer is established and analyzed.The wave equation is solved by using MATLAB,and the suspension point movement law,suspension point load and hanging point indicator diagram are simulated.Based on the dynamic software ADAMS,a three-dimensional model of downhole load reduction device is established,and the dynamics and Simulation of suspension point are carried out.The suspension point movement rule and suspension load are simulated.Finally,the simulation results of MATLAB and ADAMS are compared.The rigid-flexible coupling dynamic analysis of downhole load reducer are studied.