Leakage Study And Structural Optimization Design Of The Layered Oil Production Pump

Layered oil recovery technology is a key technology to improve oil recovery and reduce production costs in the middle and later period of oilfield exploitation.Compared with conventional pumps,layered oil pumps contain more ball valve parts,which are complex in structure and usually used in oil wells with high water content and sand content.The working conditions are worse,and the leakage and erosion wear of layered oil pumps are more likely to occur.Based on the working condition of the layered oil pump(FCCYB38-28A),in view of the high leakage quantity of the layered oil pumps gap and the erosion wear of the standing valve,computational fluid dynamics theory is used to study the annular gap flow and the flow of standing valve of the layered oil pump,by the combination of theoretical method and the way of numerical calculation.Based on the numerical calculation model of gap leakage,the 50 mm length of the gap was numerically calculated in order to study the rule of gap leakage within a single stroke.The result shows that the direction of shearing leakage and differential pressure leakage are down along the wellbore,which belong to positive leakage,while there is only negative shearing leakage when it's going down.The annular gap leakage quantity between the plunger and pump barrel increases with the increase of the pressure difference,and linear relationship was presented.The leakage quantity increases with the increase of the gap width,and shows cubic function relationship.A gap leakage model with labyrinth seal grooves was established to study the applicability of the labyrinth seal groove under the three levels of pump gap.The effect of the flow resistance of the labyrinth seal groove under the three levels of pump gap was studied by changing the viscosity value of the liquid in the calculation domain,and the applicable principles for labyrinth seal grooves aiming to three levels of pump gap were got,which is the first level pump gap with labyrinth seal groove is suitable for oil wells with a liquid viscosity of less than 2mPa·s,while the second and third levels of pump gap with labyrinth seal groove are suitable for oil wells with a liquid viscosity of less than 2.5mPa·s and 6mPa·s,separately.In order to optimize the flow resistance of the labyrinth seal groove,the influence of the groove size on the flow resistance was studied by single factor method.The result shows that,to the first level of pump gap,the flow resistance increases firstly and then decreases as the groove size increases,to the second and third levels of pump gap,the resistance increases with the increase of the groove size,within the standard range,the groove width should be 1.5mm;Through comparison and verification,it was found that,for gaps of the same length,the increasing of the groove size is more conducive to reducing leakage than the increasing of the number of seal grooves,as groove spacing is the same.Aiming at the severe erosion and worn of the seat under the standing valve opening pressure difference,the relationship between the erosion characteristics and the degree of opening of the standing valve is studied.The result shows that,the erosion of the standing valve cone is the most serious,and the maximum erosion rate decreases rapidly as the degree of opening of the standing valve increases.The influence of the seat taper of the standing valve on the maximum erosion rate is studied.The result shows that the maximum erosion rate decreases as the taper increases,when the taper value is 37.5°,can achieve a small erosion rate.The improved standing valve structure can reduce the vortex of the fluid significantly in the valve cavity.Therefore,the problem that the valve ball is not tightly sealed due to the accumulation of sediment at the valve gap is reduced.