NMR Spatial Permeability Profiling for Heterogeneous Rock Samples
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Solution Overview
Problem
Current probe permeameter techniques face limitations in measuring permeability of rock samples with rough surfaces, high pore connectivity, and heterogeneity, as they require a tight seal and are incapable of accurately measuring water permeability, especially in complex reservoir configurations.
Innovation Solution
The method employs nuclear magnetic resonance (NMR) to measure spatial water permeability by saturating and desaturating rock samples, performing T2 NMR measurements along multiple axes, and analyzing the data to derive spatial permeability profiles, which is non-destructive and not affected by the shape or composition of the rock sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If probe permeameter technique is used to measure permeability, then general heterogeneity of rock samples can be identified, but the technique fails to accurately measure water permeability in samples with rough surfaces, high pore connectivity, and heterogeneity
Solution Approach 1:
The patent replaces the mechanical probe sealing system with a non-contact NMR measurement system. Instead of using a physical probe that requires tight sealing against the rock surface, the invention uses nuclear magnetic resonance to detect hydrogen signal intensities, eliminating the need for mechanical contact and sealing. This substitution enables accurate measurement of water permeability in heterogeneous samples with rough surfaces that would be difficult to seal properly.
Solution Approach 2:
The patent changes the measurement parameter from direct pressure measurement (probe permeameter) to hydrogen signal intensity ratio (NMR). By measuring the ratio of hydrogen signal intensities in saturated and desaturated states, the system derives water permeability without requiring mechanical sealing. This parameter change allows the technique to work effectively on heterogeneous samples with varying pore structures and rough surfaces.
2Measurement precision
If probe permeameter technique is used, then gas permeability can be measured, but the technique is incapable of accurately measuring water permeability
Solution Approach 1:
The patent uses hydrogen nuclei (protons) in water molecules as an intermediary to measure water permeability. The NMR technique detects the hydrogen signal intensity, which is directly related to the amount of water in the rock pores. By measuring the change in hydrogen signal intensity between saturated and desaturated states, the system reliably quantifies water permeability without being affected by the limitations of gas-based measurement methods.
3Loss of information
If traditional permeability measurement techniques are used, then point measurements can be obtained, but continuous spatial permeability profile information cannot be derived
Solution Approach 1:
The patent transitions from point measurements to spatially distributed measurements by incorporating spatial encoding gradients in the NMR system. The measurement system acquires hydrogen signal intensities at multiple positions along the core sample axis, creating a continuous spatial profile of water permeability. This dimensional extension from single-point to multi-point measurement provides comprehensive spatial information without requiring complex arrays of physical probes.
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 provides a robust and accurate method for determining spatial permeability profiles, overcoming the limitations of traditional techniques by offering precise measurements of water permeability in heterogeneous rock samples without damaging the samples.
Implementation Method 1
performing T2 NMR (nuclear magnetic resonance) on the saturated rock sample to detect spatial NMR data along a core sample axis
Implementation Method 2
detecting, with the NMR system, spatial NMR data along a core sample axis of the rock sample
Data Source
AI summary
A method includes deriving spatial permeability along a core axis by saturating the rock with an aqueous solution, performing T2 NMR on the saturated rock to detect spatial NMR data along the core axis, desaturating the rock, performing T2 NMR on the desaturated rock to detect spatial NMR data along the core axis, determining the spatial cutoff data for the saturated and desaturated rock along the core axis, and analyzing the spatial NMR data. The method further includes deriving spatial permeability along a second core axis by additionally performing T2 NMR on the saturated rock to detect spatial NMR data along a second core axis, performing T2 NMR on the desaturated rock to detect spatial NMR data along a second core axis, and determining the spatial cutoff data for the saturated and desaturated rock along the second core axis.