Ultra-Wideband Microwave Tomography: A Concept for Multiphase Flow Measurement

In the petroleum industry, precise information about the individual flow rates of oil-gas-water flows are needed for safe and economical production. The determination of the individual flow rates requires an accurate measurement of the individual volume fractions which is a complicated task because of varying properties of the media. The measurement uncertainty of common three-phase flowmeters is strongly dependent on the flow regime. In this contribution, we propose an ultra-wideband (UWB) tomography concept to determine the individual volume fractions of multiphase flows in metal measurement pipes accounting for different flow regimes. A microwave coupling structure has been developed, which consists of a dielectric window and a waveguide with an UWB coaxial-to-rectangular-waveguide transition. A 2-channel test system has been realized and the complex transmittances and reflectances have been measured in the frequency range from 1.1 GHz to 6.0 GHz for different homogeneous media (air, rapeseed oil, and water with different salinities). The measurement results confirm the assumption of the proposed concept that it is possible to distinguish between the oil, gas, and water because of their different complex permittivities. The impact of the waveguides on the measurement results can be compensated in the frequency range from 1.1 GHz to 3.0 GHz by means of a TRL-calibration. Above 3 GHz, the excitation of higher-order waveguide modes lead to narrowband resonances in the measured frequency responses.