Improved prediction of hydraulic conductivity for coarse-grained, unconsolidated material from nuclear magnetic resonance

Dlugosch, Raphael; Günther, Thomas; Müller‐Petke, Mike; Yaramanci, U.

doi:10.1190/geo2012-0187.1

Cited by 48 publications

(42 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular, this is the case for materials containing large pores (e.g., Dlugosch et al, 2013;Dlubac et al, 2014) that are of interest for this study. One major outcome of the work of Brownstein and Tarr (1979) is summarized in Figure 2.…”

Section: Nmr Relaxation Times Theorymentioning

confidence: 99%

Nuclear magnetic resonance average pore-size estimations outside the fast-diffusion regime

et al. 2015

Self Cite

View full text Add to dashboard Cite

The pore-size distribution (PSD) of geologic materials is an important rock parameter to understand the flow of water in the subsurface. PSDs can be obtained from sieving analyses, mercury porosimetry measurements, and imaging techniques, but none of these methods is available for in situ measurements. Nuclear magnetic resonance (NMR) measurements are controlled by rock parameters such as the surface-area to porevolume ratio. NMR is available for in situ measurements. State-of-the-art NMR relaxation time measurements need a calibration of the surface relaxivity ρ to extract pore-size information. State-of-the-art NMR diffusion measurements avoid the calibration of ρ but are limited to small pores. We developed an approach that estimates the average pore size without calibrating ρ by means of incorporating higher order modes into the signal interpretation of NMR relaxation times. We conducted forward-modeling studies using an analytic solution for cylindrical tubes, 2D finite-element simulations to incorporate fractal pore spaces, and laboratory experiments on synthetic and natural samples. Our experimental data indicated that relaxation can occur outside the fast-diffusion regime not only for coarse-grained materials, but also for fine-to medium-grained unconsolidated sandy materials due to high surface relaxivities. We found that the rock-fluid interface's roughness had a significant impact on the diffusion regime and led to an apparent increase in ρ, which may cause intermediate or slow diffusion. The methodology was limited to materials with a narrow PSD and uniform distribution of ρ because we assumed multiexponential decay due to diffusion in single isolated pores.

show abstract

Section: Nmr Relaxation Times Theorymentioning

confidence: 99%

Nuclear magnetic resonance average pore-size estimations outside the fast-diffusion regime

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…For example, η = 2 for cylindrical pores, η = 3 for spherical ones, or more general, η > 3 for pores with a more complex geometry. The peak value

T_{2, normalP}^{prefix- 1}

is used in Eqn instead of the mean relaxation time because faster eigenmodes may occur if the fast diffusion assumption is not valid . In that case, the peak relaxation times are a good representation of the slowest eigenmodes.…”

Section: Nmr Relaxation Measurements In Unconsolidated Sedimentsmentioning

confidence: 99%

Effect of magnetic pore surface coating on the NMR relaxation and diffusion signal in quartz sand

Duschl

Pohlmeier

Brox

et al. 2016

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

Magnetic impurities are ubiquitous in natural porous media such as sand and soil. They generate internal magnetic field gradients because of increased magnetic susceptibility differences between solid and liquid phase in the pore space and because of the presence of magnetic centers. These internal gradients accelerate NMR relaxation rates and thus might limit the possibility of pore space characterization using NMR. In this study, we investigate the effects of coating the surface of natural sands by the antiferromagnetic iron oxyhydroxide goethite on NMR relaxation and diffusion properties. We found a non-quadratic dependence of the relaxation time distributions on the echo time indicating that the relaxation experiments were not performed in the fast diffusion limit, while the weak dependence on the external magnetic field strength is explained by the preponderance of the surface relaxation over the effect of diffusion in internal gradients. The surface to volume ratio of the pore space, determined by NMR diffusimetry ((S/V) ) remains approximately constant, whereas the same quantity, determined from gas adsorption ((S/V) ) increases proportional to the coating density. This is because gas adsorption measures surface roughness on sub-nanometer scale, whereas NMR diffusimetry averages over structures smaller than few microns. This has consequences for the calculation of the surface relaxivities. The usage of the (S/V) leads to constant values, whereas the usage of (S/V) leads to apparently decreasing relaxivities with increasing coating, which is unrealistic. Copyright © 2016 John Wiley & Sons, Ltd.

show abstract

“…The tortuosity is set to 1.5 in this study, which is a reliable estimate for coarse sand and gravel (e.g. Pape et al, 2006;Dlugosch et al, 2013). …”

Section: Estimation Of Effective Pore Radius and Hydraulic Conductivimentioning

confidence: 99%

“…Prammer et al, 1996;Behroozmand et al, 2014), and to provide hydraulic and soil physical parameters 25 (e.g. Dlugosch et al, 2013;Yaramanci, 2011, 2013;Sucre et al, 2011;Knight et al, 2016). As non-invasive tool from the subsurface, it is used for investigating the subsurface distributions of water content/porosity and hydraulic conductivity and allows for the lithological categorisation of aquifer and aquitards (e.g.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic characterisation of iron oxide-coated sand and gravel based on nuclear magnetic resonance relaxation modes analyses

Costabel¹,

Weidner²,

Müller‐Petke³

et al. 2017

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. The capability of nuclear magnetic resonance (NMR) relaxometry to characterise hydraulic properties of iron oxide-10 coated sand and gravel was evaluated in a laboratory study. Past studies have shown that the presence of paramagnetic iron oxides and large pores as present in coarse sand and gravel disturbs the otherwise linear relationship between relaxation time and pore size. Consequently, the commonly applied empirical approaches fail when deriving hydraulic quantities from NMR parameters. Recent research demonstrates that higher relaxation modes must be taken into account to relate the size of a large pore to its NMR relaxation behaviour in the presence of significant paramagnetic impurities at its pore wall. We performed 15NMR relaxation experiments with water-saturated natural and reworked sands and gravels, coated with natural and synthetic ferric oxides (goethite, ferrihydrite) and show that the impact of the higher relaxation modes increases significantly with increasing iron content. Since the investigated materials exhibit narrow pore size distributions, and can thus be described by a virtual bundle of capillaries with identical apparent pore radius, recently presented inversion approaches allow for estimating a unique solution yielding the apparent capillary radius from the NMR data. We found the NMR-based apparent radii to 20 correspond well to the effective hydraulic radii estimated from the grain size distributions of the samples for the entire range of observed iron contents. Consequently, they can be used to estimate the hydraulic conductivity using the well-known KozenyCarman equation without any calibration that is otherwise necessary when predicting hydraulic conductivities from NMR data.Our future research will focus on the development of relaxation time models that allow for broader pore size distributions.Furthermore, we plan to establish a measurement system based on borehole NMR for localising iron clogging and controlling 25 its remediation in the gravel pack of groundwater wells.

show abstract

Improved prediction of hydraulic conductivity for coarse-grained, unconsolidated material from nuclear magnetic resonance

Cited by 48 publications

References 29 publications

Nuclear magnetic resonance average pore-size estimations outside the fast-diffusion regime

Nuclear magnetic resonance average pore-size estimations outside the fast-diffusion regime

Effect of magnetic pore surface coating on the NMR relaxation and diffusion signal in quartz sand

Hydraulic characterisation of iron oxide-coated sand and gravel based on nuclear magnetic resonance relaxation modes analyses

Contact Info

Product

Resources

About