| With the decline of formation fluid supply capacity and the exploitation of unconventional oil and gas reservoirs with low permeability and ultra-low permeability,the number of low production wells in China is large and increasing year by year.However,the widespread used of API oil pump minimum diameter is 32 mm,pumping capacity is far greater than the low production wells' formation fluid supply capacity,resulting in oil well production imbalance with formation fluid supply capacity and high energy consumption problems,so that many oil wells which still have potential value were forced to shut down.A lot of oil field in order to achieve aims of the balance and reduce the installed power,starting to develop smaller diameter pump,but many of them limited application because of the space constraints lead to low structural strength and poor internal flow characteristics.Therefore,it is of great practical significance to develop small diameter oil pump with higher strength and better flow characteristics.This paper mainly includes the following aspects:First of all,according to the liquid supplying capacity of low production oil wells,a small diameter oil pump with diameter 25 mm is designed.This pump uses the solid plunger,higher structural strength can prevent the accident which caused by valve cover fracture.The liquid and gas exchange device is arranged in the pump barrel,it can reduce the gas-liquid ratio and improve pump efficiency,so as to make this pump more adapter to low production yield wells which have low submergence degree and poor fluid supply conditions.Secondly,studied the internal flow characteristics and structure strength with software CFD and FEM,the results show that no matter the eccentric or deviation of plunger pump's clearance leakage is greater than concentric gap,and with the same eccentricity rate,the leakage of deviation model is less than the eccentric one.The structure of the liquid and gas exchange device will weaken the gap sealing performance,and the sealing length at this time is the difference between the plunger and exchange cavity length.The greater degree of opening of the inlet valve,the more number and more smooth of the diversion hole,the smaller pressure drop of fluid flow,but with the degree greater,the decrease of pressure drop becomes smaller.The strength of the oil outlet valve cover of the solid plunger pump is much larger than that of the oil outlet valve on the standard pump.Finally,the optimization analysis program of the small diameter pump by using Matlab software is written to in-depth study of pumping performance,and realizes the optimization of pump efficiency prediction,structure optimization and swabbing parameters at various working parameters.Based on laboratory test,the pumping performance of the small diameter oil well pump is studied.It is proved that the accuracy of the pump efficiency predicted by the optimization program of the small diameter oil pump and the rationality of the structural design.Through the analysis of field test data show that before the relative the average pump efficiency after test increase at least7.3 percentage points.With reasonably adjust the pumping parameters,the pump efficiency will exceed 70%,confirmed the pump can meet the production requirements of low production yield wells,and provides a basis for the promotion of oil pumping technology of small diameter pump. |
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