Imaging of the water velocity distribution in water continous multiphase flows using Inductive Flow Tomography (IFT)

In the oil-gas fields, slurry flows, gas-in-water two phase flows, and oil-gas-water three phase flows are frequently encountered. Generally, the measurement of volumetric flow rate for each phase is of most interest, especially in subsea oil-gas production applications, where it is essential to obtain oil, water and gas flow rates in inclined oil wells. The problem of how to accurately measure these flow parameters for such complicated flow phenomena, without using expensive and large test separators, is a major challenge for the industry. Most conventional multiphase flow meters have severe limitations regarding types of flow and their measurement reliability. Some useful techniques containing radioactive sources are available but they are expensive and potentially harmful to humans. Thus, many academic and industrial researchers are working to develop a multiphase flow meter based on tomographic techniques that does not contain a radioactive source. Such a device would normally involve at least two independent flow metering techniques. Tomographic techniques have been successfully used in multiphase flows to determine the local volume fraction distributions of the various phases; however, only a very small number of results can be found in the published literature concerning the equally significant problem of local velocity distribution. Therefore, the aim of this research is to develop a non-intrusive flow measurement technique, without the use of radioactive sources, for measuring the local axial velocity distribution of the electrically conducting continuous phase in multiphase flows. This thesis reports the development of a multi-electrode electromagnetic flow metering technique, the so-called Inductive Flow Tomography (IFT), for obtaining the local flow velocity distributions of the electrically conducting continuous phase in multiphase flows, with particular relevance to gas-in-water two phase and oil-gas-water three phase flows. Previous research has indicated that the electromagnetic flow meter (i.e. Electromagnetic Velocity Profiler) is a promising technique for measuring the local axial water velocity in single phase and solid-in-water two phase flow. However, that technique has several limitations, which means it is valid only for determining water velocity profiles in seven regimes of the pipe crosssection. A novel multi-electrodes electromagnetic IFT flow metering system has been developed in the research described in this thesis, which is capable of determining the local conducting continuous phase velocity at any position in the flow cross-section (in vertical and inclined pipes). The theoretical work carried out in developing the IFT system includes a completely novel flow velocity distribution “image reconstruction algorithm”, which is described in the thesis. This thesis also describes the design and subsequent implementation of the hardware and software for the IFT system. In the final sections of this thesis, a series of experiments, which include inclined gas-oil-water three phase flow and gas-in-water two phase flow, were performed to investigate the performance of the IFT system. The experimental results obtained show a good agreement between the reference measurements and velocity measurements obtained using the IFT system