A numerical study of the relationship between NMR relaxation and permeability in sands and gravels

Dlubac, Katherine; Knight, Rosemary; Keating, Kristina

doi:10.3997/1873-0604.2013042

Cited by 13 publications

(14 citation statements)

References 24 publications

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“…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

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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.

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Section: Nmr Relaxation Times Theorymentioning

confidence: 99%

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

et al. 2015

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“…In Table , we compare reported b values for the lithologic constant when m = 1, found to be the optimal result in this study, and for m = 4, the standard value for petroleum applications. The table includes the standard b values and reported range of values for consolidated sandstones for petroleum applications (Kenyon ; Straley et al ); the values reported for the High Plains aquifer (Dlubac ; Dlubac et al ); and the values found in this study. We observe that as the material type becomes more consolidated (from bottom to top of the table), b decreases by about an order of magnitude in going from unconsolidated to un/semi‐consolidated material and then another order of magnitude in going to consolidated material.…”

Section: Resultsmentioning

confidence: 92%

NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers

Knight¹,

Walsh

Grunewald

et al. 2015

Groundwater

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Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger-Doll Research (SDR) equation, which is based on the Kozeny-Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. The SDR equation includes empirically determined constants. Decades of research for petroleum applications have resulted in standard values for these constants that can provide accurate estimates of permeability in consolidated formations. The question we asked: Can standard values for the constants be defined for hydrogeologic applications that would yield accurate estimates of K in unconsolidated aquifers? Working at 10 locations at three field sites in Kansas and Washington, USA, we acquired NMR and K data using direct-push methods over a 10- to 20-m depth interval in the shallow subsurface. Analysis of pairs of NMR and K data revealed that we could dramatically improve K estimates by replacing the standard petroleum constants with new constants, optimal for estimating K in the unconsolidated materials at the field sites. Most significant was the finding that there was little change in the SDR constants between sites. This suggests that we can define a new set of constants that can be used to obtain high resolution, cost-effective estimates of K from NMR logging in unconsolidated aquifers. This significant result has the potential to change dramatically the approach to determining K for hydrogeologic applications.

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Section: Introductionmentioning

confidence: 99%

“…The relaxation time constant of the NMR signal, that is, the time it takes for the nuclear spins to reequilibrate to their initial state after being perturbed by an energizing pulse, contains information about the pore size distribution (Bird et al, 2005;Brownstein & Tarr, 1979;Hinedi et al, 1997;Müller-Petke et al, 2015). Taken together, the NMR parameters have been linked to hydraulic conductivity (K) through the use of various empirical relationships (Daigle & Dugan, 2009;Daigle et al, 2014;Dlubac et al, 2014Dlubac et al, , 2013Dlugosch et al, 2013;Knight et al, 2016;Legchenko et al, 2004;Vilhelmsen et al, 2014). NMR logging has been used for decades in the petroleum industry to estimate the hydraulic properties of reservoirs (Coates et al, 1999;Daigle & Dugan, 2009, 2011Dunn et al, 2002;Kleinberg & Jackson, 2001).…”

Section: Introductionmentioning

confidence: 99%

Successful Sampling Strategy Advances Laboratory Studies of NMR Logging in Unconsolidated Aquifers

Behroozmand

Knight

Müller‐Petke

et al. 2017

Geophysical Research Letters

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The nuclear magnetic resonance (NMR) technique has become popular in groundwater studies because it responds directly to the presence and mobility of water in a porous medium. There is a need to conduct laboratory experiments to aid in the development of NMR hydraulic conductivity models, as is typically done in the petroleum industry. However, the challenge has been obtaining high-quality laboratory samples from unconsolidated aquifers. At a study site in Denmark, we employed sonic drilling, which minimizes the disturbance of the surrounding material, and extracted twelve 7.6 cm diameter samples for laboratory measurements. We present a detailed comparison of the acquired laboratory and logging NMR data. The agreement observed between the laboratory and logging data suggests that the methodologies proposed in this study provide good conditions for studying NMR measurements of unconsolidated near-surface aquifers. Finally, we show how laboratory sample size and condition impact the NMR measurements.

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A numerical study of the relationship between NMR relaxation and permeability in sands and gravels

Cited by 13 publications

References 24 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

NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers

Successful Sampling Strategy Advances Laboratory Studies of NMR Logging in Unconsolidated Aquifers

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