Multi-phase metering device for oilfield applications
This application is related to a system and methods for sampling fluids and gases using nuclear magnetic resonance (NMR) technology. Specifically the system is related to an improved metallic pipe design for use at oil and gas well heads that includes integral coils for transmitting an NMR pulse sequence and detecting NMR signals and can be used as a component of an NMR instrument. The methods are related to obtaining and analyzing NMR spectra in stationary and flowing states.
1. A method of measuring the relative quantities of fast-relaxing and slow-relaxing components in a sample flow using nuclear magnetic resonance (NMR) relaxometry, comprising the steps of:
flowing a sample comprising at least two components through the pipe, the at least two components comprising a fast-relaxing component and a slow-relaxing component;
measuring a relaxation curve corresponding to at least one fast-relaxing component as the sample flows through the pipe, by applying an electromagnetic field to the sample and recording a signal response using an NMR coil;
calculating, using a processor, a proportion of fast-relaxing component in the flowing sample based on relaxation spectra obtained from the measured relaxation curve; and
calculating, using the processor, a proportion of a slow-relaxing component in the flowing sample based on the calculated proportion of fast-relaxing component; and
enabling presentation of the calculated proportion of fast-relaxing and slow-relaxing components on a user interface.
2. The method of claim 1 , wherein the at least one fast-relaxing component comprises oil.
3. The method of claim 1 , wherein the at least one slow-relaxing component comprises water.
4. The method of claim 1 , wherein the method comprises: calibrating the NMR pipe with a stationary sample comprising a known proportion of a fast-relaxing component.
5. The method of claim 1 , wherein the calibration step comprises calibrating the NMR pipe with a pure sample of the fast-relaxing component.
6. The method of claim 1 , wherein the fluid is flowing at a speed that allows collection of a fast-relaxing component relaxation signal without counting for a slow-relaxing component relaxation signal.
7. The method of claim 1 , wherein the method comprises repeating one or more of the calibration steps over a selected temperature range.
8. The method of claim 1 , wherein the proportion of the slow-relaxing component, S src , is calculated as: S src =1−S frc , where S frc is the proportion of fast-relaxing component.
9. The method of claim 1 , wherein the method comprises creating the relaxation spectra for the sample using a standard NNLS (non-negative least-squares) algorithm.
10. The method of claim 1 , wherein mixture consists of two components.
11. The method of claim 1 , wherein the method comprises:
measuring the sample flow rate; and
calculating a cut of a slow-relaxing component based on relaxation spectra obtained from the measured relaxation curves and on the measured flow rate.
12. The method of claim 1 , wherein the measurement period corresponds to a time greater than the relaxation time range of the fast-relaxing component and slower than the relaxation time range of the slow-relaxation component.
13. The method of claim 1 , wherein the method comprises:
measuring the temperature of the sample; and
setting a measurement period based on the measured temperature of the sample.
14. The method of claim 1 , wherein the method comprises:
measuring a relaxation curve corresponding to at least one fast-relaxing component during a measurement period; and
controlling the flow rate of the sample based on the measurement period duration.
15. An NMR apparatus for measuring the relative quantities of fast-relaxing and slow-relaxing components in a sample flow using nuclear magnetic resonance (NMR) relaxometry, the NMR apparatus comprising:
a pipe configured to receive a flowing sample comprising at least two components, the at least two components comprising a fast-relaxing component and a slow-relaxing component;
NMR components configured to measure a relaxation curve corresponding to at least one fast-relaxing component of the flowing sample; and
a processor configured to calculate a proportion of fast-relaxing component in the flowing sample based on relaxation spectra obtained from the measured relaxation curve; and to calculate a proportion of a slow-relaxing component in the flowing sample based on the calculated proportion of fast-relaxing component.
16. A method of measuring the relative quantities of components in a fluid using nuclear magnetic resonance (NMR) relaxometry in an NMR pressure tube or pipe, comprising the steps of:
calibrating the NMR pressure tube or pipe with a pure oil sample by putting a pure oil sample within the NMR pressure tube and applying an electromagnetic field to the sample and recording a signal response using the NMR coil thereby providing a pure-oil calibration curve;
introducing at least a two-component mixture into the NMR pressure tube or pipe, wherein the mixture comprises oil and water;
measuring relaxation curves of a hydrogen signal by applying an electromagnetic field to the mixture and recording a response using the NMR coil;
calculating water-cut using a processor based on relaxation spectra obtained from the measured relaxation curves; and
enabling presentation of the calculated water-cut on a user interface.
17. An NMR apparatus for measuring the relative quantities of components in a fluid, the NMR apparatus comprising a electronic circuit having a processor and a NMR pressure tube, the NMR apparatus being configured to:
calibrate the NMR pressure tube or pipe with a pure oil sample;
introduce at least a two-component mixture into the NMR pressure tube or pipe, wherein the mixture comprises oil and water;
measure relaxation curves of a hydrogen signal; and
calculate water-cut based on relaxation spectra obtained from the measured relaxation curves.