Analysis and Countermeasures on the Efficiency of the Pumping Wells System in the Old Oil-field

Abstract In China, some old oil fields into the late stage of development, the wellbore fluid become complexity, and the production and the pump efficiency gradually decline, which lead to an increase in production costs. According to the statistics, the efficiency of 36.7% of the total wells are lower than 30%, By analyzing the main reason for the low efficiency of the pump and combined the status of oil well production, statistical analysis on the impact of system efficiency under different working conditions and establish a corresponding model. The model mainly analyses the impact of stroke number, the stroke, the pump diameter, the submergence depth and gas content on pump efficiency. According to the well structural characteristics, a geometric model of the downhole rod system is established and the finite element model is generated by unit discrete. Considering the boundary conditions of the contact boundary of the sucker rod and tubing, the frictional resistance between the sucker rod and well fluid, the frictional resistance between the plunger and the pump barrel and the process of loading and unloading of the oil column, the numerical solution technology is adopted, which can reproduce the state of deformation of the rod string in a stroke, and gain the indicator diagram of the down hole pump and the efficiency of the system the down hole rod. Selecting the test wells of the oil production plant in Daqing Oilfield to check the model, the results show the error of pump displacement is 0.7% and the error of rod efficiency is 7.8%. On the basis of this analysis, the different stroke, pump speed, dynamic liquid level and pump diameter impact on the rod efficiency is analyzed. The calculation results show: the rod efficiency decreases with the increase of stroke and pump speed, the rod efficiency increases with the increase of fluid level and pump diameter and when the product of the stroke and stroke number is a fixed value, high speed and low stroke is beneficial to improve the efficiency of rod.