NMR Fluid Content Determination Using Internal Standard Sample
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Solution Overview
Problem
Existing methods for measuring fluid content in subsurface formations using low field nuclear magnetic resonance (NMR) face inaccuracies due to discrepancies between calibration and measurement conditions, leading to unreliable porosity measurements.
Innovation Solution
A method and system that utilize a standard sample with known chemical composition and NMR attributes, disposed alongside the formation sample in an NMR coil, to acquire simultaneous NMR signals and calculate fluid content using the formula Vr = Vst * Mst / Mr, where Mst is the NMR signal of the standard sample and Mr is the formation sample, effectively mitigating instrument instability and ensuring accurate fluid content determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external standard calibration method is used, then measurement process is simple, but measurement precision deteriorates due to instrument instability between calibration and measurement
Solution Approach 1:
The patent introduces an internal standard sample as an intermediary reference that co-exists with the formation sample during NMR measurement. This internal standard serves as a mediator to account for instrument instability, allowing real-time correction of measurement signals without requiring separate calibration procedures, thus maintaining both operational simplicity and measurement precision
2Device complexity
If separate calibration and measurement procedures are used, then device complexity is low, but reliability deteriorates due to condition discrepancies
Solution Approach 1:
The patent merges the calibration reference and measurement sample into a single NMR measurement process by placing the internal standard sample together with the formation sample in the same measurement environment. This combination ensures both experience identical instrument conditions, eliminating reliability issues caused by condition discrepancies while maintaining procedural simplicity
3Measurement precision
If internal standard sample is used, then measurement precision improves, but device complexity increases due to additional sample preparation
Solution Approach 1:
The patent utilizes parameter changes in the internal standard sample's NMR signal characteristics (relaxation times, signal intensity) to encode reference information that can be extracted during measurement. By selecting standards with distinct but overlapping NMR parameters, the system achieves high measurement precision while keeping preparation simple, as the standard only requires known fluid content and characteristic NMR properties
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 significantly reduces measurement errors, achieving accurate and reliable fluid content determination with minimal variability, as demonstrated by a maximum error of 3% compared to the external standard method's 10% error, by using an internal standard sample to account for instrument stability and ensure clear signal separation.
Implementation Method 1
Nuclear magnetic resonance (NMR) has been employed for some time to study the fluids inside the pore space of porous media. The fluid supplies numerous atoms or molecules in the pore space, and these molecules or atoms, when the external electro-magnetic field is carefully applied to them, would generate electrical signals in a sensing probe.
Implementation Method 2
NMR spectroscopy may be used to measure the spin-lattice (longitudinal) relaxation time (T1) and/or the spin-spin (transverse) relaxation time (T2) of the fluid.
Implementation Method 3
NMR spectroscopy may be used to measure the spin-lattice (longitudinal) relaxation time (T1) and/or the spin-spin (transverse) relaxation time (T2) of the fluid.
Data Source
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AI summary
Methods and systems for determining fluid content in a formation sample are disclosed. The method includes disposing the formation sample with a standard sample of a known chemical composition and one or more nuclear magnetic resonance (NMR) attributes in a NMR coil or probe, and acquiring NMR signals for the formation sample and the standard sample simultaneously. The system includes a NMR probe or NMR coil, a formation sample, and a standard sample with known chemical composition and one or more nuclear magnetic resonance (NMR) attributes, wherein the formation sample and the standard sample are disposed in the NMR coil or probe, and wherein NMR signals are acquired for the formation sample and the standard sample simultaneously.