NMR Spectral Deconvolution for Pore and Absorbed Gas Mass
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Solution Overview
Problem
Traditional laboratory methods for determining porosity in unconventional reservoirs, such as shale formations, are unable to accurately differentiate between pore gas and absorbed gas, leading to overestimation of porosity and inaccurate reservoir characterization.
Innovation Solution
A method using spectral deconvolution of calibrated NMR spectra to separate and determine the mass of absorbed gas and pore gas in rock core samples, allowing for a more reliable estimation of porosity and other reservoir characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional laboratory methods are used to determine porosity in unconventional reservoirs, then the measurement process is simple, but the ability to differentiate between pore gas and absorbed gas is poor, leading to overestimation of porosity
Solution Approach 1:
The patent segments the gas signal into two distinct components: pore gas signal and absorbed gas signal. By separating these signals through spectral deconvolution, the method can accurately differentiate between gas in pore spaces and gas absorbed on kerogen surfaces, eliminating the overestimation error that occurs when treating both as pore gas.
Solution Approach 2:
The patent introduces an intermediary approach using NMR spectroscopy with spectral deconvolution as a mediator between the raw NMR signal and the final porosity calculation. This intermediary process separates the overlapping signals from pore gas and absorbed gas, enabling precise porosity measurement without requiring complex physical separation methods.
2Measurement precision
If NMR spectroscopy with spectral deconvolution is used to separate absorbed gas and pore gas, then porosity determination accuracy is improved, but the measurement process becomes more complex
Solution Approach 1:
The patent replaces complex mechanical or physical separation methods with NMR spectroscopy and spectral deconvolution. Instead of physically separating pore gas from absorbed gas through complex apparatus, the method uses magnetic resonance principles and mathematical deconvolution to distinguish between the two gas types, simplifying the overall measurement system while improving accuracy.
3Reliability
If absorbed gas is not differentiated from pore gas, then the measurement process is simpler, but reservoir characterization becomes inaccurate
Solution Approach 1:
The patent utilizes parameter changes in the NMR spectrum, specifically differences in relaxation times (T2) between pore gas and absorbed gas. By analyzing changes in spectral parameters rather than physically separating the gases, the method achieves accurate reservoir characterization while maintaining measurement simplicity.
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 more accurate determination of porosity and other reservoir characteristics, enabling better reservoir modeling and simulation for hydrocarbon recovery scenarios, and guiding drilling operations.
Implementation Method 1
NMR spectroscopy, or NMR, measures the interaction of nuclear spins of atoms within the sample, when placed in a powerful magnetic field
Implementation Method 2
separating the differential NMR spectrum into an absorbed gas NMR spectrum to determine an absorbed gas NMR signal and a pore gas NMR spectrum to determine a pore gas NMR signal by performing a spectral deconvolution
Implementation Method 3
acquiring a normalization NMR spectrum of the pressure cell containing a gas to determine a gas calibration NMR signal
Data Source
AI summary
A method and system for determining a mass of an absorbed gas and a mass of a pore gas in a sample using NMR spectroscopy is provided. The method includes acquiring a baseline NMR spectrum of a pressure cell containing the sample, saturating the sample with a gas, acquiring a saturated NMR spectrum and determining a differential NMR spectrum of the sample by subtracting the baseline NMR spectrum from the saturated NMR spectrum. The method also includes separating the differential NMR spectrum into an absorbed gas NMR spectrum to determine an absorbed gas NMR signal and a pore gas NMR spectrum to determine a pore gas NMR signal by performing a spectral deconvolution. The method further includes acquiring a normalization NMR spectrum of the pressure cell containing a gas to determine a gas calibration NMR signal and determining the mass of the absorbed gas and pore gas.