Computational Fluid Dynamics (CFD) is used to investigate the hydraulic performance of a centrifugal pump within the electrical submersible pump (ESP) unit in single-phase flow. The geometry consists of a three-stage centrifugal pump with an impeller and a diffuser in each stage. The stage performance is influenced by the inlet and outlet conditions of the stage, and therefore, three stages were modeled. The simulations were run at 3,500 RPM for various flow rates within the operating range. The k-ε turbulence model and the shear stress transport (SST) turbulence model were used to compare the capabilities of the model on performance predictions. Simulations were run in steady and unsteady flow conditions with a single vane and a full pitch model. Hydraulic performance such as efficiency, pump head, and break horse power (BHP) obtained from numerical analysis were compared with the test results to validate the CFD model. The comparison results revealed that the CFD overpredicts the pump head and underpredicts the BHP by 5 to 10%. The discrepancy between measurements and predictions are reasonable because the hydraulic leakage and bearing power losses are not modeled in CFD. The overall predicted efficiency is higher than the measurements because of overpredicted head and underpredicted BHP. Comparing numerical simulations with different turbulent models showed no significant difference between the k-ε model and the SST model. The steady/ unsteady flow comparison also showed similarity in the hydraulic performance near the best efficiency point. For design purposes, steady flow simulation with a single vane and the k-ε model were used to cut computational time.

Extending system run life impacts well profitability by cutting artificial lift replacement costs and reducing production losses from downtime. The run life of Electrical submersible pumping (ESP) motor can be increased by reducing the operating temperature of the motor. On the other hand, cooler-running motors can be used for high-temperature wells, where downhole temperatures may be a limiting factor.Controlling motor temperature is important for increasing ESP run life as motor temperature plays a key role in motor failures. Power losses in ESP motors were analyzed for various operating conditions. Power losses are the source of heat generation and the resulting temperature rise in the ESP motor. The internal motor temperature depends upon heat generation in the motor, well parameters, operating conditions, as well as the design and materials used to manufacture the motor.To reduce internal operating temperature, the motor should efficiently transfer the heat generated within the motor to the well fluid. New techniques for efficient heat transfer were developed and ESP motors with an enhanced motor-cooling design were built. These modified motors were tested in wells under controlled conditions in Claremore, Oklahoma and in two field trials in conventional and SAGD wells. The results showed a significant decrease in the internal operating temperature. This paper will address various contributing factors affecting motor internal temperature, an enhanced cooling design, and field trial test results.

In oilfield applications, an electrical submersible pumping (ESP) system is placed inside the wellbore to provide the necessary energy to lift the fluids to the surface when the reservoir pressure is not sufficient. The ESP system consists of an electric motor, seal section, rotary gas separator (optional), multistage centrifugal pump, electric power cable, motor controller and transformers. The electric motor is placed on the bottom of the unit, and the production fluids are allowed to pass around the motor in order to cool it. The motor generates heat while operating. Study on the temperature rise inside the motor is important to prevent components from failing due to overheating. The temperature rise inside a motor has not been studied extensively. In this work, the temperature of components inside an electric motor was measured under different loading conditions, fluid viscosity and temperature. After testing, the computational fluid dynamic (CFD) was used to model the temperature heat rise in the same motor under the same conditions. The CFD models were validated by the test data within ± 5% error. Furthermore, the validated CFD model was used to calculate the heat rise for different insulation and bedding materials. These computational results from CFD are used to optimize the design of the electrical motor.

In oil field applications, the Electrical Submersible Pumping (ESP) unit (comprised of multistage pump, seal and motor) is placed inside a wellbore to provide necessary energy to lift reservoir fluids from the formation to the surface when the energy in the reservoir is not sufficient to lift the fluid to the surface. ESP motors produce heat while operating. The motors are cooled by the well fluid that passes the motor while being pumped. Many well fluids have very limited heat carrying capacity, resulting in higher operating temperature within the motor. Only a limited number of studies have been conducted that have analyzed the inside temperature rise in the motor. A parametric study has been conducted using the computational fluid dynamic software Ansys CFX to examine the profile of the temperature rise in the motor. The computational model is validated by experimental data which showed that the computational model predicts the temperature with 95% accuracy. Therefore, this computational model effectively represents the experimentally determined temperature distribution of the motor.