Effect of jet ejector geometry on the supply of a pumping unit preventing wax-deposit

Abstract

Relevance. Today oil production by installations of electric centrifugal pumps is one of the leading methods of mechanized oil production. The mechanized operation of hard-to-recover oil objects is complicated by the high viscosity of reservoir oil, the formation of wax-deposits in the wellbore. This leads to an increase in hydraulic resistances due to a decrease in the flow section of pipes and other pumping equipment components, a decrease in the productivity of wells and the efficiency of pumping production. In this regard, an urgent task is to develop and improve methods and devices for preventing deposits of wax-deposits in wells. Object. Downhole pumping unit for dosing reagent (inhibitor of wax-deposits) into the well, which is a combination of two technical devices – a pump dosing the reagent and a jet pump. Aim. To analyze the influence of the design parameters of the dosing unit on the efficiency of its operation (reagent consumption, liquid cavitation coefficient in the jet pump). Methods. Mathematical modeling of the operation of a downhole dosing unit for the supply of reagent, based on the application of the laws of conservation of mass and quantity of motion, as well as Bernoulli's law for a moving flow in a jet pump. Results. Based on the simulation results, the nature of the influence of the design parameters of the developed installation on the reagent consumption is established. It is established that the maximum flow rate of the reagent is achieved with a mixing chamber diameter of about 22 mm; an increase in diameter relative to the specified value leads to a decrease in the degree of local pressure reduction, a decrease in the diameter of the mixing chamber – a drop in flow due to an increase in the flow rate in the chamber and an increase in hydraulic resistance. It was found that an increase in the supply of electric centrifugal pumps in the considered range of 100–200 m3 per day has practically no effect on the reagent consumption when the mixing chamber diameter is more than 30 mm. It was found that at confuser length values exceeding 210 mm, the cavitation coefficient, regardless of the mixing chamber diameter, exceeds one, which indicates a smooth and uniform pressure reduction in the device body. In general, it is shown that by regulating the design parameters of a downhole metering unit, it is possible to ensure the required reagent consumption at a known electric centrifugal pump supply (well flow rate).