IMPROVING THE CENTRIFUGAL PUMP DESIGN AND CHANGING THE STRENGTH OF OPERATION

Abstract

Background Currently, the share of electric centrifugal pump (EСP) units, which operate in a periodic mode, is growing in the production structure at a marginal fund. In this mode, the pump flow varies from the maximum value at the beginning to the minimum at the end of the pumping period. The trend towards such dynamics is explained by the fact that the fund of low-yield wells is growing in Western Siberia, where EСP is the main mechanized method of production. When oil is being produced in marginal wells, it is often necessary to encounter such a problem, when the dynamic level of the gas-liquid mixture can drop to a critical level. In this case, the pump flow is reduced, and the pressure developed by the pump is insufficient to overcome the hydrostatic pressure of the liquid column in the tubing. In this case, the pump stops pumping fluid and an inevitable failure of the pumping unit occurs due to a motor burnout. In addition, an increase in EСP operating in automatic periodic switching on mode leads to a significant reduction in well production. Aims and Objectives The aim of the work is to introduce a device for stabilizing the pressure at the inlet to the EСP station, which would discharge part of the oil product back to the pump through the annulus without stopping the equipment. In order to ensure reliable operation of this structure, the material was tested for strength and durability, taking into account the redistribution of stresses and changes in properties during operation. Results The tests of samples from pipe fragments of steel 40X with a service life of 57, 378, 1035 days showed a decrease in the tensile strength and yield strength by 20 % and 6 %, respectively. The distribution of hardness over the cross section of the wall of the tested pipe fragments showed that the core is harder than the edges of the wall, while as the operation progresses there is a slight hardening. Impact test results showed a significant reduction in toughness by 73 %. Fatigue tests carried out according to the circular curvature with rotation, revealed a decrease in fatigue life. The analysis of the device for stabilizing the pressure at the inlet to the ESP revealed that the most loaded unit is the overlap mechanism, which forms the hydraulic channel between the tubing cavity and the annular space. The calculation the action of the axial compressive load and the internal pressure of this node showed that the resulting loads in the stress concentration zones do not exceed the allowable values.