Automated NMR Relaxometer for Borehole Core Porosity
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Solution Overview
Problem
Existing low frequency NMR relaxation measurements for oil-bearing earth formations are inefficient for high-throughput, automated surface measurements, particularly due to the irregular shapes and varying lengths of sidewall core samples, which complicates calibration to porosity and affects the accuracy and speed of data collection.
Innovation Solution
A high-throughput automated low field NMR relaxometer system with a controllable static magnetic field gradient and reconfigurable NMR antenna allows for measurements on irregularly shaped samples by selecting a sensitivity volume within the sample using a switchable gradient, enabling calibration to porosity without independent volume measurement, and processing NMR signals from both the entire and a fraction of the sample to determine petrophysical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manual loading of core plugs in sample holder is used, then measurement accuracy can be maintained, but productivity is low and automation is difficult
Solution Approach 1:
The system segments the measurement process by using multiple sample holders that can be independently loaded and measured. Each sample holder contains multiple sample positions, allowing parallel processing of multiple samples. This segmentation enables automated high-throughput measurement without requiring complex automation for each individual sample handling.
Solution Approach 2:
The sample holders are designed with universal compatibility to accommodate different types of borehole materials including core plugs, sidewall cores, drill cuttings, and microcores. The same holder design and measurement protocol can be used across all sample types, enabling automated high-throughput processing without requiring sample-specific customization.
2Adaptability or versatility
If measurements are performed on irregularly shaped samples, then sample representivity is improved, but measurement precision deteriorates due to calibration difficulties
Solution Approach 1:
The system changes the measurement parameter from volume-dependent to volume-independent by using normalized NMR signals. Instead of requiring precise volume measurements for calibration, the method uses the ratio of NMR signals from different samples, eliminating the need for accurate volume determination and enabling precise porosity calibration for irregularly shaped samples.
Solution Approach 2:
The system creates a reference measurement by comparing NMR signals from unknown samples against known reference samples with established porosity values. This copying approach allows calibration without requiring precise volume measurements of irregular samples, as the calibration is performed through signal ratio comparison rather than absolute volume determination.
3Quantity of substance
If entire sample volume is measured, then measurement completeness is improved, but signal-to-noise ratio deteriorates for irregular samples
Solution Approach 1:
The system applies local quality by selecting and measuring only the most NMR-active portion of each sample rather than the entire volume. For irregularly shaped samples with varying fluid content and relaxation properties, the method identifies and measures the region with optimal signal characteristics, improving signal-to-noise ratio while still providing representative porosity information through normalized measurements.
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 efficient, high-throughput surface NMR measurements that are calibrated to porosity, improving the accuracy and speed of data collection while maintaining a high signal-to-noise ratio, and allows for comparison with downhole NMR measurements for comprehensive earth formation evaluation.
Implementation Method 1
The static magnetic field aligns nuclei in a sample with the direction of the static magnetic field
Implementation Method 2
The RF magnetic field is typically applied in a form of a sequence of RF pulses (e.g., a standard CPMG pulse sequence) to produce a sequence of spin echoes
Implementation Method 3
an NMR antenna generating a radio-frequency (RF) magnetic field
Data Source
AI summary
A method for NMR measurements on borehole materials, e.g., sidewall cores, is based on performing a standard measurement in substantially homogeneous magnetic fields with a sensitivity volume covering an entire sample and a measurement on a fragment of the sample (local measurement), the fragment having a predetermined volume independent of the irregularities of the sample shape (e.g., irregular shaped edges). The fragment of the sample is selected using a switchable static magnetic field gradient or a localized radio-frequency magnetic field. The homogeneous and the local measurement data are processed jointly to obtain volume normalized NMR relaxation data (in porosity units), the processing also using a calibration sample data. A measurement apparatus with an automated sample transfer can be used to implement the method in order to perform high-throughput NMR relaxation measurements that do not require independent measurement of the sample volume.