Research on Oil Recovery Technology of Graded Pressure Subsurface Pump

CO₂ flooding in low-permeability reservoirs can significantly increase oil recovery. However, owing to the injection of CO₂, the gas content in the production medium is increased, resulting in a decrease in the pump efficiency. To address the problem, a graded pressure subsurface pump is developed. Through the analysis of the structure and working principle of the graded pressure pump, the numerical simulation method is used to simulate the operation of the graded pressure pump in the gas-liquid two-phase medium. The distribution of pressure and gas-liquid two-phase medium and the variation with time in the pump cylinder during the operation of the graded pressure pump is attained. The simulation results indicate that the graded pressure pump can reduce the opening pressure of the travelling valve and lower the stroke loss of the pump. The pressure difference between the travelling valve and the fixed valve can be reduced, and the CO₂ dissolved and precipitated on the upper and lower strokes could be decreased. The up stroke loss is reduced, and the pump efficiency is improved. The graded pressure pump can also avoid the air lock. Compared with the traditional pump, the efficiency of the graded pressure pump can be improved by about 20%, presenting a significant production increase performance.