NMR Multiphase Flow Measurement Using Pre-Polarization
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Solution Overview
Problem
Accurate measurement of flow rates and phases of multiphase fluid flows in pipes, particularly in the petroleum industry, is challenging due to the complexity of hydrocarbon transport.
Innovation Solution
A Nuclear Magnetic Resonance (NMR) spectrometer-based method and apparatus that estimates flow rates of selected phases in multiphase fluids by using pre-polarization and detection sections to align nuclear spins and apply RF pulses, allowing for the calculation of flow rates through signal analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NMR techniques are used to measure flow rates in multiphase fluids, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The NMR flow measurement system is divided into distinct functional sections: a pre-polarization section with its own magnet and a detection section with its own magnet and RF coils. This segmentation allows each section to be optimized independently and simplifies the overall system architecture by distributing functionality across separate modules rather than requiring a single complex integrated system.
Solution Approach 2:
The pre-polarization section acts as an intermediary that prepares the fluid by aligning nuclear spins before the fluid enters the detection section. This intermediary step enhances the NMR signal strength in the detection section, improving measurement precision without requiring the detection section itself to be overly complex.
2Measurement precision
If pre-polarization section is added to improve signal strength, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The pre-polarization section performs preliminary action by aligning the nuclear spins of fluid molecules before they reach the detection section. This preliminary polarization enhances the NMR signal strength during detection, improving measurement precision without requiring complex signal processing or detection hardware.
Solution Approach 2:
The system merges the pre-polarization function and detection function into a single integrated flow measurement device, with both functions operating on the same fluid stream in sequence. This merging approach allows the complex functionalities to be combined in a coordinated manner that simplifies overall system operation compared to separate independent systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise determination of flow rates and phase velocities in multiphase fluids, effectively addressing the measurement challenges by leveraging NMR techniques to differentiate between hydrocarbon and water phases.
Implementation Method 1
a pre-polarization section for polarizing nuclear spins of fluid along a selected direction
Implementation Method 2
a detection section for providing NMR excitation pulses to the fluid and obtaining NMR signals in response to the NMR excitation pulses from the fluid
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
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.