Restricted diffusion and exchange of water in porous media: Average structure determination and size distribution resolved from the effect of local field gradients on the proton NMR spectrum

Kuntz, Jean-François; Palmas, P.; Level, Vincent; Canet, Daniel

doi:10.1016/j.jmr.2007.12.020

Cited by 10 publications

(16 citation statements)

References 22 publications

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“…Note that each 2D spectrum has been normalised to constant total intensity so as to remove T 1 relaxation effects. We note that unlike [13], the 2D spectra obtained here are very symmetric. A clear growth of off diagonal intensity is observed as the mixing time is increased.…”

Section: Mhzmentioning

confidence: 60%

“…This can lead to some ambiguity when it comes to interpreting peak locations. Kuntz et al [13] have proposed a new 2D exchange experiment which involves only the Fourier transformation. This simple exchange method in principle allows one to investigate exchange between pores of imbibed fluid molecules, simply as a result of changes in local Larmor frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Observation of molecular migration in porous media using 2D exchange spectroscopy in the inhomogeneous magnetic field

Burcaw

Callaghan

2009

Journal of Magnetic Resonance

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Section: Mhzmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Observation of molecular migration in porous media using 2D exchange spectroscopy in the inhomogeneous magnetic field

Burcaw

Callaghan

2009

Journal of Magnetic Resonance

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“…• Fourier-Laplace NMR: By considering the merits of Fourier and Laplace NMR methods, these two techniques are easily married in the context of spectroscopy/imaging with relaxation/diffusion. For instance, Diffusion-Ordered SpectroscopY (DOSY) and Relaxation-Relaxation-Ordered SpectroscopY (RROSY) yield diffusion and relaxation correlation maps of molecular compositions within different chemical shift values [32,71,72]. Propagator-resolved relaxation and REXSY methods monitor the molecular translational displacements in certain size range in flow experiments and track how far fluid molecules move during the experimental mixing time to estimate critical pore morphologies [73][74][75].…”

Section: Multi-dimensional Nmr Techniquesmentioning

confidence: 99%

“…Induced magnetic field B in [58][59][60] RRCOSY [63,82,83] DRCOSY, RICOSY, DRICOSY [24,[84][85][86] Correlation DDCOSY [64] REXSY [32,69] Laplace-Laplace Exchange DEXSY [68,70] DOSY, RROSY [32,71,72] Spectroscopy-resolved Relaxation-MAS [87] Relaxation/Diffusion [76][77][78] Spatially-resolved DRCOSY [79,80] 1D relaxation or diffusion [73,74] Fourier-Laplace Propagator-resolved REXSY [75] the current strength in RF coil delivered by the RF power amplifier of the spectrometer 4 .…”

Section: Othersmentioning

confidence: 99%

Advanced NMR methodologies in rock core analysis

Liu¹

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<p>¹H NMR techniques have gained extensive acceptance in petrophysics for the evaluation of fluid-saturating reservoir rocks. This thesis presents the development of new NMR methods regarding the reserves (determination of pore length scales and surface relaxivities), productivity (estimates of permeability) and recovery of fluids (resolves of saturation evolution) in rocks. Traditionally, pore lengths are evaluated from the ground relaxation eigenmodes of spin-bearing molecules in pore space. This evaluation is not straightforward since it is affected by surface relaxivity. Here, we use an approach to determine pore length from detecting the high relaxation eigenmodes, in which way the eigenvalue spectrum directly scales to the pore size distribution. Based on this, we extend this approach for the use with low-field NMR spectrometers and 2D NMR eigenmode correlation methods. Surface relaxivity can be further extracted from these 2D correlation maps, which is in agreement with an independent NMR measurement. Permeability is generally estimated from surface relaxation via empirical pore-network models. However, for heterogeneous rocks a single (or averaged) permeability value may not be adequate. Therefore, we measure surface relaxation in conjunction with MRI techniques. Permeability profiles can then be obtained from spatially resolved relaxation maps yielding local connectedness between adjacent slices. The results are confirmed by the comparison of brine-permeability measurements. MRI experiments of fluids in rocks at reservoir-like conditions may yield optimized recovery strategies of reservoir fluids. In this context we combine MRI with diffusion-relaxation correlation measurements during flooding intervals. The results provide substantial information, such as flooding front and saturation profiles of immiscible fluids discriminated by fluid type.</p>

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“…Most recently, Kuntz et al [40] proposed a simple exchange experiment to study the frequency exchange in a water-filled glass bead sample and a polystyrene sample. For their experiments they used two glass bead packs with a mean diameter of 31 µm and standard deviations of 5.6 µm and 9.3 µm.…”

Section: Two-dimensional Exchange Experimentsmentioning

confidence: 99%

Multi-Dimensional Nuclear Magnetic Resonance Methods in the Inhomogeneous Magnetic Field

Burcaw¹

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<p>This thesis introduces new NMR techniques which use the inhomogeneous internal magnetic fields present in the pore space of a porous medium exposed to an external magnetic field to obtain information about the pore size and heterogeneities of the the sample. Typically internal field inhomogeneities are regarded as unwanted due to their effect on various material properties such as relaxation and diffusion. However, in the experiments presented here, we choose samples specifically for their inhomogeneous internal fields and use multi-dimensional NMR methods and simulations to obtain our pore space and heterogeneity information. We first describe software developed to specifically simulate the internal magnetic field and diffusion through the pore space of a simple sphere pack system. This software generates a sphere pack and calculates the internal magnetic field generated by z-aligned magnetic dipoles placed at the center of each sphere. The internal magnetic field gradient is also calculated in the pore space. From there, a random walk method is developed and a realistic reflection off a sphere is introduced. We work through the development of this software and the mathematics behind the algorithms used. This simulation is used in all subsequent experimental chapters. We then use a two-dimensional exchange experiment to separate the susceptibility induced line broadening with the broadening caused by diffusion through the inhomogeneous field. We observe off-diagonal line broadening as the mixing time increases. We attempt to quantify this off-diagonal growth by selecting points on either side of the off-diagonal maximum and plotting their average as a function of mixing time. A biexponential fit to the average intensities with respect to mixing time results in a characteristic time and from that a characteristic length as a fraction of bead diameter. This experiment is simulated and a biexponential growth is also observed in the simulated off-diagonal with characteristic lengths comparable to experiment. To obtain a correlation length directly from experiment and not deduce one from a characteristic time, we add a spatial dimension to our exchange experiment in the form of a propagator dimension. This dimension allows us to select 2D spectra based on their Z-displacement. We observe off-diagonal growth due to both an increase in Z-displacement and an increase in mixing time. We move away from the biexponential fit and move to a relationship based on mixing time, effective diffusion, and Z-displacement to directly calculate a characteristic length. We see these same traits in the simulated data which agrees well with experiment. Lastly, we move away from exchange experiments and move to correlating the transverse relaxation time with the internal field offset. We find that there is correlation at large magnetic field offsets and small T2 times which appear to be indicative of sample heterogeneities. To confirm this we use a highly heterogeneous rock core sample which increases the correlations seen at the previous offsets and times. This experiment is more qualitative than the previous two as we do not have a concrete value for the heterogeneity of our samples. The simulation used throughout the thesis, while showing a definite correlation between field offset and T2 relaxation, is unable to accurately simulate the experiment and requires more development.</p>

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Restricted diffusion and exchange of water in porous media: Average structure determination and size distribution resolved from the effect of local field gradients on the proton NMR spectrum

Cited by 10 publications

References 22 publications

Observation of molecular migration in porous media using 2D exchange spectroscopy in the inhomogeneous magnetic field

Observation of molecular migration in porous media using 2D exchange spectroscopy in the inhomogeneous magnetic field

Advanced NMR methodologies in rock core analysis

Multi-Dimensional Nuclear Magnetic Resonance Methods in the Inhomogeneous Magnetic Field

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