A Dual Frequency Inductive Flow Tomography System for Fast Imaging of Water Velocity Profiles in Water Continuous Multiphase Flows

Measurement of the velocity profile of water continuous multiphase flows is important because it can enable production optimisation and avoidance of unwanted flow assurance issues in both mining and oil and gas industries. However, accurate measurement of the velocity profile of the continuous phase in multiphase flows when they are time dependent or transient is still a challenge in such industries. Many available commercial multiphase flow meters, which are not able to directly measure the velocity profile of the continuous phase, use radioactive measurement techniques. Radioactive measurement techniques have many safety issues involving exposure to radiation, which is very harmful and is a known cause of cancer in humans.

This thesis describes the development of a non-radioactive based flow meter, which relies on the measurement principle of a multi-electrode electromagnetic flow meter. This flow meter is capable of measuring the velocity profile of the conducting continuous phase in both single and multiphase flows tens (or potentially even hundreds) of times every second. The images of velocity profile of the conducting continuous phase in both single and multiphase flows were reconstructed using inductive flow tomography technique (IFT) from flow induced potential difference measurements obtained from a flush mounted array of electrodes on the wall of the flow meter. The designed and developed IFT system presented in this thesis consists of (i) a flow meter body, which has coils for generating magnetic fields and an array of 16-electrodes to enable sensing of flow induced potential differences; (ii) analogue electronic circuits for coil excitation and for signal conditioning of flow induced potential difference measurements and (iii) a computer unit for controlling system hardware and data acquisition and processing (which includes the mathematical algorithm for reconstructing the velocity profile of the continuous phase).

Performance of the IFT system was tested in vertical single-phase ‘water only’ flows and in both vertical and inclined two-phase air-in-water and solids-in-water flows. The velocity profile measurements from the IFT system were in good agreement with reference measurements and were consistent with previous work cited in the literature. In addition, the IFT system was tested in both single-phase ‘water only’ and air-in-water transient vertical flows, for which the velocity profiles were measured with improved accuracy and temporal resolution.