Salinity-Independent Multiphase Fraction Metering for the Oil and Gas Industry using Microwave Sensors

Microwave sensing based on variation in dielectric properties is a well-known method for the multiphase fraction metering of oil, water, and gas mixtures. However, this method is severely affected by variation in the salinity levels of the mixture, a problem that is complicated by the fact that salinity varies with temperature. As a result, frequent calibration of the sensor is required to correct for changes in the salinity of a multiphase flow. In this paper, a dual-frequency orthogonal resonator (DFOR) microwave sensor is proposed for accurate multiphase fraction metering without the need for frequent sampling or calibration. This is achieved by utilizing the dispersion characteristics of brine, which generates an independent data set that allows the salinity of the mixture to be determined. The preliminary results obtained from the testing of a DFOR prototype in an industrial flow loop (SwRI, Norway) with two salinity settings support the proposed concept.