Numerical Analysis of Electromagnetic Multiphase Fraction Sensor

Oil-gas-water multiphase flows are often encountered in the oil and gas industry. The accurate measurement of the different phase fractions inside a production pipeline over different flow regimes is a challenge for the industry. This paper illustrates the use of a microwave transmission sensor that measures the amplitude attenuation and phase shift of oil-water-gas mixtures of varying water/liquid ratio (WLR) and gas fraction. The research prototype consists of several microwave antennas placed around the cross section of a pipe, with different positions of the receivers relative to the transmitter. Numerical analysis of the measurements is made for inhomogeneous flow distribution with a central gas “core” in the liquid. For a homogeneous two-phase oil-water flow, knowledge of amplitude attenuation, phase shift, and distance between antennas can be used to determine the dielectric permittivity and conductivity of the fluid inside the pipe. By using an appropriate dielectric mixing model, the WLR of the liquid inside the pipe can be obtained using the values determined for dielectric permittivity and conductivity. For three-phase flow, determination of WLR is more difficult because of the presence of gas. To investigate the effect of gas fraction variation, sensitivity maps for different transmitter-receiver pairs can be obtained by numerical analysis performed using three-dimensional (3D) electromagnetic (EM) modelling. By analysing the responses of amplitude attenuation and phase shift of the different receivers, the apparent permittivity and conductivity of the gas core in a liquid distribution can be obtained.