Oil/water stratified flow in a horizontal pipe: Simulated and experimental studies using EIT

Abstract

An experimental and a simulation study to describe oil/water stratified flow in a horizontal pipe was carried out. Oil/water mixtures are common in oil producing wells and stratified flow often occurs during pipeline transportation. Mixtures of paraffin oil in water with different concentrations of the oil phase were investigated. Regarding the experimental study three techniques were used to acquire information about the oil phase distribution in the pipe cross-section: Electrical Impedance Tomography (EIT), sample collection in different radial positions for oil quantification, and photographs of the flow. Concerning the EIT system an adjacent protocol was used in the acquisitions since it allows for a more precise reconstruction of the images in the case of stratified flows. The simulations were conducted mainly in 2D, using the level set model to describe the phenomenon in the oil/water interface in combination with the k-ε turbulence model. The COMSOL Multiphysics software was used for the simulations. 3D simulations were also conducted which did not prove more precise, in spite of the very high computational time required. The experimental tests were carried out in an existing pilot rig. In the course of this study superficial water inlet velocity ranged in the interval between 0.30 and 0.45 m s−1 and superficial oil inlet velocity between 0.17 and 1.27 m s−1. Pressure drop along the test section was the control variable, and a good fit was obtained between simulations in a 2D geometry and experiments, the maximum deviation between the experimental and simulated pressure drops being 9.7%.