CFD Simulations of Oil Viscosity and Emulsion Effects on ESP Stage Performance

Abstract

Abstract Oil-water emulsion effects on a seven-stage electrical submersible pump (ESP) performance are studied experimentally and numerically with computational fluid dynamics (CFD) simulation. At different oil-water fractions, temperatures, and ESP rotational speeds, the performance of the third stage was measured. The intention of this work is to validate and compare experimental data with CFD simulation results. In addition, flow structures can be visualized through the CFD simulation for oil-water emulsion flows. Density and mass flow rate are measured using the mass flowmeter while the emulsion effective viscosity is derived from the pipe viscometer installed downstream of the ESP. CFD simulations are carried out with estimated droplet sizes of the dispersed phase for oil-water flows, and the results are compared with the experiments. For the wall roughness, a higher value is used due to the extended use of the ESP. The three-dimensional, steady-state Reynolds-Averaged Navier–Stokes (RANS) equations with standard shear stress transport (SST) turbulence model are solved in ANSYS CFX solver by employing the frozen-rotor technique. With high-quality structured hexahedral mesh grids, the simulated pressure increment is compared with corresponding experimental results. For single-phase cases, results show considerable differences compared to experiments, which may be partially due to neglecting leakage losses in CFD simulations. When the two-phase simulation is conducted, it is confirmed that the solver takes oil and water as dispersion instead of emulsion, for which rheological behavior is not reflected. This is because the solver is based on two sets of Navier-Stokes equations for each phase. Consequently, the better approach for simulating the emulsion flow in ESPs by CFD methodology is to assume a single-phase, pseudo-homogeneous fluid with the rheology depending on the oil and water fractions and properties.