Method of interpreting NMR signals to give multiphase fluid flow measurements for a gas/liquid system

• Main Authors: Freeman, John Justin, Appel, Matthias
• Format: Patent
• Language: English
• Published: 02.03.2017
• Subjects: MEASURING; MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUIDLEVEL; METERING BY VOLUME; PHYSICS; TESTING

A method for assessing a gas phase in a flowing multi-phase fluid comprises flowing the fluid through magnetic resonance and pre-polarization modules and applying to the fluid a radio-frequency pulse sequence at least once with and at least once without a magnetic field gradient. The method further includes measuring an NMR signal. The method also includes using a calibration between the ratio of slope and intercept of the NMR signal and flow velocity for at least one non-gas phase with the gradient applied to determine that phase's velocity. A calibration between the signal intensity of the liquid phases as function of flow velocity is used, with and without gradient, to correct the gradient-induced attenuation of the liquid signals and to calculate a gradient-corrected signal intensity of the liquid phases without a magnetic field gradient. Additionally, the method includes subtracting the gradient-corrected signal intensity from the NMR signal to calculate the volumetric fraction of the liquid phase.