EFNMR Fluid Measurement System for Multiphase Flow Accuracy
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Solution Overview
Problem
Existing multiphase flow meters face challenges in accurately measuring oil and water flow rates in industrial pipelines due to the complexity of multiphase fluid streams and varying flow regimes, particularly with increased water content as reservoir lifetimes extend.
Innovation Solution
A fluid measurement system utilizing an Earth's field nuclear magnetic resonance (EFNMR) detection coil with dual polarization and Tikhonov inversion techniques to determine velocity and content of oil and water phases, enabling precise phase differentiation and volumetric flowrate measurement across various flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multiphase flow meters are used to measure oil and water flow rates, then basic flow measurement is possible, but measurement accuracy deteriorates due to complex multiphase fluid streams and varying flow regimes
Solution Approach 1:
The patent replaces conventional mechanical or electronic multiphase flow metering systems with an NMR-based measurement system. The NMR system uses magnetic field interactions with hydrogen nuclei in the fluid to measure phase velocities and flow rates, eliminating the need for mechanical moving parts or complex electronic sensors that struggle with multiphase flows. This substitution enables accurate measurement across different flow regimes (stratified, dispersed, emulsified) by relying on fundamental magnetic resonance properties rather than mechanical flow dynamics.
Solution Approach 2:
The patent utilizes changes in NMR signal parameters (relaxation times T1 and T2, signal amplitude) to differentiate between oil and water phases and to measure their respective flow rates. By analyzing how these parameters vary with flow regime, phase composition, and velocity, the system achieves accurate measurement despite the complexity of multiphase streams. The inversion algorithms process these parameter variations to extract quantitative flow information.
2Measurement precision
If NMR-based measurement is applied to achieve phase differentiation, then measurement accuracy improves, but device complexity increases due to pre-polarizing magnets and inversion algorithms
Solution Approach 1:
The patent employs a pre-polarizing magnet positioned upstream of the NMR detection coil to pre-align the magnetic moments of hydrogen nuclei in the fluid before they enter the detection zone. This preliminary polarization action enhances the NMR signal strength and improves phase differentiation capability. By performing this preparatory magnetic alignment before detection, the system achieves better measurement accuracy without requiring overly complex detection electronics or processing.
3Measurement precision
If inversion algorithms are used to determine phase velocities, then measurement accuracy improves, but computational complexity and processing time increase
Solution Approach 1:
The patent applies iterative inversion algorithms that progressively refine the velocity and flow rate estimates from NMR signal data. Rather than attempting to solve the complete inverse problem in a single step, the algorithm performs multiple iterations, each improving the accuracy of phase velocity determination. This partial action approach balances computational effort with measurement precision, achieving reliable results without requiring excessive processing time or computational resources.
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
The system provides unambiguous phase differentiation and improved measurement accuracy for both oil and water flow rates, especially in wet gas flow scenarios, by leveraging NMR signals and pseudo-1D inversion methods, enhancing robustness across a range of flow regimes.
Implementation Method 1
circulating the mixed-phase fluid through a pre-polarizing magnet to initially polarize the gas phase and the liquid phase
Implementation Method 2
measuring a plurality of free induction decay (FID) values of the polarized gas phase and a plurality of FID values of the polarized liquid phase with an Earth's field nuclear magnetic resonance (EFNMR) detector
Data Source
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AI summary
Techniques for measuring fluid properties include circulating a mixed-phase fluid flow through a fluid flow circuit; circulating the mixed-phase fluid flow through a pre-polarizing magnet; polarizing at least a gas phase of the mixed-phase fluid flow to an initial polarization; measuring fluid induction decay (FID) values of the polarized gas phase with the EFNMR detector; determining a velocity of the gas phase based on the FID values of the polarized gas phase; producing a pulsed magnetic field gradient to suppress one or more signals acquired by the EFNMR detector with a first electromagnet; measuring FID values of the liquid phase of the mixed-phase fluid with the EFNMR detector simultaneously with the production of the pulsed magnetic field gradient; producing a homogeneous polarizing field to polarize the liquid phase of the mixed-phase fluid with a second electromagnet; and determining a velocity and content of the liquid phase based on the FID values of the polarized liquid phase.