Absolute Measurement of Pore Size based on Nonground Eigenstates in Magnetic-Resonance Relaxation

Afrough, Armin; Vashaee, Sarah; Zerón, Laura Romero; Balcom, Bruce J.

doi:10.1103/physrevapplied.11.041002

Cited by 11 publications

(7 citation statements)

References 24 publications

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“…Nonground eigenvalues of relaxation, after detection, may be employed in predicting pore size and surface relaxivities in natural porous media. This paper expands our previous letter [30] with more detailed descriptions, more experiments, different samples, three static magnetic fields, and a T 1 − T 2 imaging method.…”

Section: Introductionmentioning

confidence: 70%

“…Independently, we recognized that nonground eigenvalues of the relaxation-diffusion equation in magnetic resonance relaxation of porous media might be experimentally observed in simple measurements that commenced with homogeneous magnetization [30]. Such measurements, including that of Carr-Purcell-Meiboom-Gill (CPMG), inversion recovery, and their variants, are extensively employed worldwide.…”

Section: Introductionmentioning

confidence: 99%

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Pore-Size Measurement from Eigenvalues of Magnetic Resonance Relaxation

et al. 2021

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Nonground eigenvalues are widely disregarded in magnetic resonance relaxation measurements of porous media due to difficulties involved in their measurement, detection, and the derivation of physically meaningful parameters from them. Such nonground eigenvalues may be experimentally observed in relaxation measurements, such as the relaxation correlation of T 1 − T 2 , and yield information on the pore size and surface relaxivity of porous media without calibration through other independent measurements. Nonground eigenvalue analysis of T 1 − T 2 measurements on Berea sandstone undertaken at three static magnetic fields produces pore sizes consistent with those obtained through x-ray microtomography and SEM measurements. Similar agreement is found for a Bentheimer sandstone with a more complex pore geometry. A phase-encoding imaging variant of this method measures the imbibition confinementsize profile in Berea sandstone. It is suggested that the existence of nonground eigenmodes may be much more prevalent in simple magnetic resonance relaxation measurements than previously considered. Therefore, it is possible to measure pore size by matching numerical Brownstein-Tarr solutions with those of experiments in a wide variety of samples and magnetic resonance methods.

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Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Pore-Size Measurement from Eigenvalues of Magnetic Resonance Relaxation

et al. 2021

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“…This work extends our quest to examine realistic porous media with simple magnetic resonance experiments [37] and has wide-reaching potential applications in laboratory petrophysical studies, monitoring aquifers by surface magnetic resonance, process and industrial control, and magnetic resonance imaging all of which routinely employ free induction decays. Among possible radiological applications, this study is especially prevalent to imaging methods that employ FIDs, such as the Ultrashort Echo Time (UTE) method [5], as the main means of signal formation.…”

Section: Discussionmentioning

confidence: 82%

“…1f. In complex porous materials that are dominated by two pore sizes, such as Indiana limestone [37], the simple FID model of this work is likely to fail, and a more complex equation with a summation of two terms in Eq. ( 5) representing two pore size populations may fit experimental data.…”

Section: Discussionmentioning

confidence: 99%

“…The liquid saturation method and solvent flushing followed Recommended Practices for Core Analysis by the American Petroleum Institute [35]. The pore-filling brine solution wets the surface of chalk and sandstone rocks used in this work as witnessed by previous transverse relaxation studies [36,37]. Further information on the Danian chalk composition and properties may be found in [36,38].…”

Section: Theorymentioning

confidence: 99%

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Magnetic resonance free induction decay in geological porous materials

Afrough

2021

Eur. Phys. J. E

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Magnetic resonance is an important noninvasive technology across life sciences and industry. Free induction decay is the simplest 1 H magnetic resonance measurement method and an important means of probing fast-decaying signals in porous materials such as rocks, lung, and bone. It is commonly assumed that the free induction decay in geological porous materials is single-exponential. We experimentally observed two regimes of free induction decay behavior in geological porous materials: single-exponential and non-exponential decay. Numerical simulations that match experimental data highlight the effect of mass diffusion, especially in the single-exponential behavior. These two regimes of free induction decay in porous materials are associated with a bifurcation point in the solutions of the Bloch-Torrey equation for diffusion of fluids in confined domains in the presence of internal magnetic field gradients. This finding facilitates the extraction of absolute internal magnetic field gradient intensities from simple free induction decay measurements in the laboratory and field. This work also warns against common single-exponential assumptions in surface magnetic resonance methods employed in surveying underground water aquifers.

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Simple MATLAB and Python scripts for multi‐exponential analysis

Afrough,

Mokhtari,

Feilberg

2024

Magnetic Reson in Chemistry

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Multi‐exponential decay is prevalent in magnetic resonance spectroscopy, relaxation, and imaging. This paper describes simple MATLAB and Python functions and scripts for regularized multi‐exponential analysis methods for 1D and 2D data and example test problems and experiments. Regularized least‐squares solutions provide production‐quality outputs with robust stopping rules in ~5 and ~20 lines of code for 1D and 2D inversions, respectively. The software provides an open‐architecture simple solution for transforming exponential decay data to the distribution of their decay lifetimes. Examples from magnetic resonance relaxation of a complex fluid, a Danish North Sea crude oil, and fluid mixtures in porous materials—brine/crude oil mixture in North Sea reservoir chalk—are presented. Developed codes may be incorporated in other software or directly used by other researchers, in magnetic resonance relaxation, diffusion, and imaging or other physical phenomena that require multi‐exponential analysis.

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Absolute Measurement of Pore Size based on Nonground Eigenstates in Magnetic-Resonance Relaxation

Cited by 11 publications

References 24 publications

Pore-Size Measurement from Eigenvalues of Magnetic Resonance Relaxation

Pore-Size Measurement from Eigenvalues of Magnetic Resonance Relaxation

Magnetic resonance free induction decay in geological porous materials

Simple MATLAB and Python scripts for multi‐exponential analysis

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