Application of microwave spectroscopy for the detection of water fraction and water salinity in water/oil/gas pipe flow

Multiphase meters (MPMs) are used by the petroleum industry for measurement of individual flowrates of water, gas and oil flowing through a pipeline. Different meters are available on the market, most of them detect water by a measurement of the dielectric properties of the fluid mixture. To be able to deduce water content from a measurement of the mixture permittivity, the dielectric properties of each of the constituents must be known in advance. While the oil and gas permittivity is known from information about their respective density, water permittivity depends on the salt content. If water is the continuous phase in a multiphase flow, it is crucial to know the water salinity for a good performance of MPMs. A dedicated water salinity sensor has been developed, the purpose being to detect water conductivity and salinity in a water continuous water/oil/gas/ mixture. The sensor is based on microwave spectroscopy and measures differential attenuation and phase-shift of electromagnetic radiation propagating through the mixture. This paper presents the basic principles, physical models and main design of the salinity sensor as well as experimental results obtained from flow loop test.