NMR Pressure Cell Core Sample Uptake Measurement
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Solution Overview
Problem
Conventional methods for determining the uptake capacity of core samples are often inaccurate due to the need for rigorous testing and configuration of systems, which is not always properly maintained, and they typically use small, powdered core samples that can introduce errors from increased surface area and physical alteration.
Innovation Solution
The method involves using a nuclear magnetic resonance (NMR) pressure cell to measure the NMR spectrum signals of a test fluid within a core sample, deconvolving the signals to separate the fluid in the annulus and within the core, and calculating the mass of the fluid based on the NMR spin magnetizations and geometric parameters, allowing for direct measurement of fluid uptake without destroying the core sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional volumetric or gravimetric methods are used to measure fluid uptake in core samples, then the measurement process is simple to perform, but the accuracy is reduced due to sample alteration and physical changes
Solution Approach 1:
The patent replaces conventional mechanical volumetric or gravimetric measurement systems with a nuclear magnetic resonance (NMR) based measurement system. The NMR system uses magnetic fields and radiofrequency pulses to directly detect fluid uptake in the core sample, eliminating the need for mechanical volume displacement measurements or weight changes, thereby improving accuracy without excessive complexity
Solution Approach 2:
The patent changes the measurement parameter from indirect mechanical/volumetric/gravimetric parameters to direct NMR signal parameters. By measuring the NMR signal intensity and relaxation characteristics of the fluid in the core sample, the system directly quantifies fluid uptake capacity, avoiding errors from sample alteration that plague conventional methods
2Quantity of substance
If small powdered core samples are used in conventional methods, then the surface area is increased for better measurement, but errors are introduced from physical alteration and increased surface area effects
Solution Approach 1:
Instead of using small powdered samples to increase surface area for measurement, the patent inverts the approach by using larger intact core samples. The NMR measurement technique allows sufficient signal detection from larger samples without requiring powder form, thereby eliminating errors from physical alteration while maintaining adequate measurement sensitivity
Solution Approach 2:
The NMR measurement system replaces the need to physically alter samples into powder form. The magnetic resonance technique can detect fluid uptake in intact core samples, eliminating the requirement for mechanical size reduction and the associated surface area effects that cause measurement errors
3Ease of operation
If conventional measurement systems are used without rigorous testing, then the operation is easier and maintenance is simpler, but the reliability of measurements is reduced
Solution Approach 1:
The NMR measurement system is designed to be self-calibrating and self-validating through intrinsic NMR parameters. The system automatically determines fluid uptake capacity from the NMR signal characteristics without requiring extensive external calibration or validation procedures, maintaining ease of operation while ensuring measurement reliability
Solution Approach 2:
The system incorporates feedback through the NMR signal measurement process itself, where the detected signal intensity and relaxation times provide direct information about fluid uptake accuracy. This inherent feedback mechanism ensures reliable measurements without requiring complex external validation systems
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 accurate and non-destructive measurement of fluid uptake capacity in core samples, reducing errors associated with sample alteration and enabling repeated testing, while directly measuring gas and hydrocarbon storage capacity in reservoir rocks.
Implementation Method 1
measuring a nuclear magnetic resonance (NMR) spectrum signal of a test fluid at a particular pressure
Implementation Method 2
deconvolving the NMR spectrum signal into a first NMR spectrum signal portion that is associated with a first portion of the test fluid in the annulus and a second NMR spectrum signal portion that is associated with a second portion of the test fluid entrained in the core sample
Data Source
AI summary
Techniques for determining an uptake capacity of a core sample include measuring a nuclear magnetic resonance (NMR) spectrum signal of a test fluid at a particular pressure and entrained in a core sample enclosed in a test cylinder of an NMR pressure cell such that an annulus is defined between the core sample and the test cylinder; deconvolving the NMR spectrum signal into a first NMR spectrum signal portion that is associated with a first portion of the test fluid in the annulus and a second NMR spectrum signal portion that is associated with a second portion of the test fluid entrained in the core sample; and determining a mass of the second portion of the test fluid based at least in part on the first and second NMR spectrum signals.