Coaxial NMR Probe Oscillating Field Diffusion
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Solution Overview
Problem
Current NMR methods for analyzing formation fluids in the oil and gas industry assume a single diffusion constant, which is inadequate for crude oils with a distribution of diffusion coefficients, leading to incomplete characterization of fluid properties.
Innovation Solution
A coaxial NMR probe is designed with an elongated conductor generating an oscillating electromagnetic field within a fluid sample, allowing for the analysis of T1, T2, and diffusion coefficients without the need for separate pulsed field gradient coils, using the oscillating field as both a magnetic field and a pulsed gradient for spatial encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate pulsed field gradient coils are used for diffusion measurements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the functions of the oscillating field coil and pulsed field gradient coils into a single oscillating field coil. The oscillating field coil generates both the RF excitation field and the magnetic field gradients necessary for diffusion measurements, eliminating the need for separate gradient coils and simplifying the probe structure while maintaining measurement capability
Solution Approach 2:
The oscillating field coil is designed to perform multiple functions: it serves as both the RF excitation coil for generating NMR signals and the pulsed field gradient coil for spatial encoding and diffusion measurements. This multi-functional design reduces device complexity while preserving the precision needed for characterizing crude oil diffusion coefficients
2Device complexity
If static gradient methods are used for diffusion measurements, then device complexity is reduced, but measurement precision deteriorates due to assumption of single diffusion constant
Solution Approach 1:
The patent employs periodic oscillating field pulses from the oscillating field coil to create time-varying magnetic field gradients. These periodic gradients enable the measurement of diffusion coefficients without assuming a single diffusion constant, allowing accurate characterization of crude oils with distributed diffusion coefficients while maintaining simple probe structure
Solution Approach 2:
The oscillating field coil varies the magnetic field gradient parameters dynamically through its oscillating nature, enabling the system to probe different diffusion coefficients in the crude oil mixture. This parameter variation allows accurate fluid property characterization without the limitations of static gradient methods
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 accurate measurement of fluid properties like T1, T2, and diffusion coefficients in both laboratory and high-pressure, high-temperature environments, such as downhole, providing detailed characterization of complex fluid compositions.
Implementation Method 1
The elongated conductor generates an oscillating electromagnetic field within the interior volume of the housing. The oscillating electromagnetic field produces a NMR signal within the fluid sample.
Implementation Method 2
The oscillating pulse field gradient de-phases the spins and then is turned off for a period, during which the spins diffuse. Following the diffusion period, the oscillating pulse field gradient is turned on to re-phase the spins followed by a spin-echo.
Data Source
AI summary
A coaxial nuclear magnetic resonance (NMR) probe and related methods are described herein. The coaxial NMR probe includes a housing with a fluid inlet, a fluid outlet, a longitudinal axis, and an interior volume. The housing contains a fluid sample that is analyzed by the probe. The coaxial NMR probe also includes an elongated conductor disposed along the longitudinal axis of the housing. The elongated conductor generates an oscillating electromagnetic field within the interior volume of the housing. The oscillating electromagnetic field produces a NMR signal within the fluid sample. The elongated conductor may also be used to receive this NMR signal. The NMR signal is then analyzed to determine information about the fluid sample. Various NMR pulse sequences for use with this coaxial probe and other coaxial probes are also described herein.