NMR Pulse Sequence Overlapping Diffusion Times
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Solution Overview
Problem
Existing NMR diffusion measurement techniques face challenges in differentiating between intrinsic bulk diffusivity and restricted diffusivity in porous media, especially when dealing with complex samples like tight oil and emulsions, due to limitations in distinguishing between pore size effects and fluid composition.
Innovation Solution
A method and system that apply an NMR pulse sequence with overlapping diffusion times, using a first set of pulses and a second set of pulses with specific area parameters to encode for both diffusion times, allowing for the measurement of diffusion coefficients and their correlation, thereby differentiating between bulk and restricted diffusivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NMR diffusion measurement techniques are used, then diffusion coefficients can be measured, but it is difficult to differentiate between intrinsic bulk diffusivity and restricted diffusivity caused by small pore sizes
Solution Approach 1:
The measurement process is segmented into multiple diffusion time points (e.g., short, intermediate, and long diffusion times). By measuring diffusion coefficients at different time scales, the method separates the contribution of bulk diffusivity (which remains constant across time) from restricted diffusivity (which varies with diffusion time), enabling clear differentiation between the two components.
Solution Approach 2:
The diffusion time parameter is systematically varied across multiple measurements. By changing this key parameter and observing how the diffusion coefficient changes (or remains constant), the method identifies whether the measurement reflects bulk properties (time-independent) or restricted diffusion (time-dependent), thereby resolving the ambiguity.
2Measurement precision
If multiple diffusion times are measured using separate experiments, then bulk and restricted diffusivity can be differentiated, but the measurement time and experimental complexity increase
Solution Approach 1:
Multiple diffusion time measurements are merged into a single NMR experiment by implementing a pulsed field gradient sequence that encodes multiple diffusion time points within one acquisition. This allows simultaneous collection of data for short, intermediate, and long diffusion times without requiring separate experiments, significantly reducing total measurement time while maintaining the ability to differentiate bulk and restricted diffusivity.
Solution Approach 2:
The NMR pulse sequence is designed to continuously acquire diffusion data across multiple time points within a single experimental run. The gradient pulses and echo times are configured to maintain continuous measurement of diffusion coefficients at varying time points, eliminating idle time between separate experiments and maximizing the efficiency of data collection.
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
This approach enables unambiguous differentiation between intrinsic bulk diffusivity and restricted diffusivity, providing accurate characterization of porous media and fluid properties by analyzing the correlation between diffusion coefficients at different times.
Implementation Method 1
A first set of pulses and a second set of pulses encode for a first diffusion time and a second diffusion time, respectively
Implementation Method 2
Nuclear magnetic resonance (NMR) can be used to determine properties of a substance. An NMR method includes applying a static magnetic field to the substance. The static magnetic field generates an initial magnetization of atomic nuclei within the substance.
Implementation Method 3
a measurement of diffusion. The relaxation measurement and diffusion measurement can be used to determine the pore size distribution of the porous medium and fluid type contained within the porous medium
Data Source
AI summary
A method and system for determining a property of a substance using nuclear magnetic resonance (NMR) is described herein. The method includes applying a NMR pulse sequence to the substance. The NMR pulse sequence includes a first set of pulses and a second set of pulses. The first set of pulses and the second set of pulses encode for overlapping diffusion times. By overlapping diffusion times, the NMR pulse sequence can be used to measure a diffusion coefficient for a first diffusion time, a diffusion coefficient for a second diffusion time, and a correlation between the two overlapping diffusion times. This information, in turn, can be used to differentiate between intrinsic bulk diffusivity of the substance and the reduced diffusivity of the substance caused by restricted diffusion.