Nuclear magnetic resonance 1H and 13C multiphase flow measurements, estimating phase selected flow rates from velocity distributions, volume fractions, and mean velocity
A method and apparatus for estimating a flow rate of a phase of a multiphase fluid is disclosed. A first velocity distribution is obtained for a first set of nuclei in the fluid from a Nuclear Magnetic Resonance (NMR) signal received for the fluid in response to a first NMR excitation signal. A second velocity distribution is obtained for a second set of nuclei in the fluid from an NMR signal received for the fluid in response to a second NMR excitation signal. A velocity of the phase is estimated from the first velocity distribution and the second velocity distribution. The flow rate of the phase is estimated using the estimated velocity of the phase and an estimated volume fraction of the phase.
1. A method of estimating in the petroleum industry, a flow rate in a pipe, of a selected phase of a multiphase fluid, with an NMR spectrometer comprising:
obtaining a first velocity distribution of amplitudes from a first set of nuclei in the multiphase fluid from a Nuclear Magnetic Resonance (NMR) signal received from the multiphase fluid in response to a 1 H NMR excitation signal;
obtaining a second velocity distribution of amplitudes from a second set of nuclei in the multiphase fluid from an NMR signal received from the multiphase fluid in response to a 13 C NMR excitation signal;
estimating a velocity of the selected phase from the first velocity distribution and the second velocity distribution; and
in the NMR spectrometer processor:
determining a volume fraction and a mean velocity of a water phase and a hydrocarbon phase using said amplitudes obtained from the first velocity distribution;
determining a volume fraction and a mean velocity of the hydrocarbon phase using an amplitude obtained from the second velocity distribution;
estimating the flow rate of the selected phase, using the determined volume fractions and the estimated velocities, and
providing the estimated flow rate of the selected phase to an output storage device of the NMR spectrometer.
2. The method of claim 1 , wherein obtaining each velocity distribution further comprises performing inversion on the related NMR signal.
3. The method of claim 1 , wherein the multiphase fluid is obtained from an oil field production system.
4. The method of claim 1 , wherein estimating a volume fraction of the phase further comprises comparing an amplitude of the obtained NMR signal to a previously determined signal amplitude from a calibrated flow of a hydrocarbon phase in a pipe section having the same configuration.
5. The method of claim 2 , wherein further comprising:
aligning the first and second sets of nuclei along a selected direction in a first section of the pipe; and
obtaining the NMR signal in a second section of the pipe.
6. The method of claim 5 , further comprising reducing a flow velocity of the phase of the fluid in the first section of the pipe.
7. The method of claim 6 , wherein reducing a flow velocity further comprises increasing a radius of the first section of the pipe.
8. An NMR spectrometer apparatus configured for estimating, in the petroleum industry, a flow rate in a pipe, of a selected phase of a multi phase fluid, comprising:
a transmitter configured to provide Nuclear Magnetic Resonance (NMR) excitations to the multiphase fluid;
a receiver configured to receive signals from the multiphase fluid in response to the NMR excitations; and
a processor configured to:
obtain a first velocity distribution of amplitudes from a first set of nuclei in the multiphase fluid from a Nuclear Magnetic Resonance (NMR) signal received from the multiphase fluid in response to a 1 H NMR excitation signal;
obtain a second velocity distribution of amplitudes from a second set of nuclei in the multiphase fluid from an NMR signal received from the multiphase fluid in response to a 13 C NMR excitation signal;
estimate a velocity of the selected phase from the first velocity distribution and the second velocity distribution;
determine a volume fraction and a mean velocity of a water phase and a hydrocarbon phase using said amplitudes obtained from the first velocity distribution;
determine a volume fraction and a mean velocity of the hydrocarbon phase using an amplitude obtained from the second velocity distribution;
estimate the flow rate of the selected phase, using the determined volume fractions and the estimated velocities, and
provide the estimated flow rate of the selected phase to an output storage device of the NMR spectrometer.
9. The NMR spectrometer apparatus of claim 8 , wherein the processor is further configured in order to obtain each velocity distribution by performing an inversion of the correspondingly related response signal.
10. The NMR spectrometer apparatus of claim 8 , wherein the multiphase fluid is obtained from an oil field production system.
11. The NMR spectrometer apparatus of claim 8 , wherein the processor is further configured to estimate the volume fraction of the selected phase by comparing an amplitude of the received NMR signal to a previously determined signal amplitude from a calibrated flow of a hydrocarbon phase in a pipe section having the same configuration.
12. The NMR spectrometer apparatus of claim 9 , further comprising
a polarization magnet configured to align nuclei along a selected direction in a first section of the pipe, and
a coil configured to receive an NMR response sign in a second section of the pipe.
13. The NMR spectrometer apparatus of claim 12 , wherein the first section of pipe is configured to reduce a flow velocity of the fluid.
14. The NMR spectrometer apparatus of claim 13 , wherein the first section of the pipe has a greater radius than the second section of the pipe.