Multiphase Flow Measurement using Earth s Field Nuclear Magnetic Resonance
Multiphase flow metering has significant potential in a number of industries; particularly in the oil and gas industry with regards to assisting the development of marginal fields and monitoring subsea processing. We demonstrate the novel use of a nuclear magnetic resonance (NMR) multiphase flow meter consisting of a pre polarising permanent magnet upstream of an Earth's field NMR detection coil. The application of suitable signal analysis in interpreting the H NMR signal acquired from a flowing stream allows determination of the relevant velocity probability distribution. The accuracy of such velocity distributions is verified using superficial velocity measurements obtained from an in line rotameter as well as comparison to theoretical turbulent velocity distributions. The flow metering system has been successfully applied to two phase air/water flows in order to simultaneously track both liquid holdup and liquid velocity with time in both the stratified and slug flow regimes.