Nuclear magnetic resonance measurement of hydrodynamic dispersion in porous media: preasymptotic dynamics, structure and nonequilibrium statistical mechanics

Abstract

Measurement of displacement time and length scale dependent dynamics by pulsed gradient spin echo nuclear magnetic resonance in porous media directly provides the preasymptotic hydrodynamic dispersion coefficient. This allows for comparison with nonequilibrium statistical mechanics models of hydrodynamics dispersion in porous media. Preasymptotic dispersion data and models provide characterization of porous media structure length scales relevant to transport and are related to the permeability and sample heterogeneity.

Permeability of a growing biofilm in a porous media fluid flow analyzed by magnetic resonance displacement‐relaxation correlations

“…The absolute value of the data is analyzed so all phase information is lost and instead of a phase shift corresponding to the velocity induced displacement, only hydrodynamic dispersion information is retained (Seymour and Callaghan, 1997). Before the bacteria were inoculated into the system, the results for the three displacement observation times Δ show the well‐known increase in preasymptotic hydrodynamic dispersion D (Δ; Codd and Seymour, 2012) and the same T 2 of 700 ms. As the biofilm grew, the Δ = 50 ms data continue to show about the same amount of hydrodynamic dispersion at T 2 ∼ 700 ms, while the 250 and 500 ms data show larger amplitude hydrodynamic dispersion more broadly distributed in amplitude as the biofilm grew. The decrease in signal intensity of the shorter T 2 peak in the 50 and 250 ms data is evident between the second and third columns, again demonstrating that a sloughing event occurred at about 30 h of biofilm growth.…”

Application of PFG–NMR to Study the Impact of Colloidal Deposition on Hydrodynamic Dispersion in a Porous Medium

“…6, alternatively low-q data can be directly measured to obtain D * (Seymour and Callaghan 1997). The preasymptotic longitudinal dispersion is observed to increase with time (Codd and Seymour 2012;Scheven et al 2007) for the clean and colloid impacted systems. There is an increase in dispersion from the CBP to the bead packs after infusion of colloidal particulates (CS1 and CS2) representative of the holdup and long tails of the displacements.…”

“…The dispersion of a fluid in a porous media indicates the degree of interconnectivity of the pore space and provides insight into the morphological characteristics of the porous medium (Codd and Seymour 2012). A useful dimensionless number to characterize dispersion in porous media is the Péclet number (Pe) which is the ratio of convective to diffusive force and can be written (Seymour and Callaghan 1997):…”

“…enough molecules must experience the same displacement behaviour over a certain displacement time. The displacement length and time scale that correspond to diffraction characterize the structure of the sample through molecular diffusion (Callaghan et al 1991;Latour et al 1993;Sen et al 1994;Callaghan et al 1999) or flow and hydrodynamic dispersion (Seymour and Callaghan 1996;Codd and Seymour 2012). In the current work a distinct NMR diffraction pattern is detected which corresponds to the displacement necessary for molecules to sample the rigid boundaries of the spherical packing medium by flow and dispersion.…”

“…The study of flow through porous media is a rich field encompassing many phenomena of interest in natural and technological settings (Sahimi 1993;Johnson et al 1996;Berkowitz and Ewing 1998;Prat 2002). Nuclear magnetic resonance (NMR) is a powerful non-invasive tool for the investigation of fluid transport in porous media (Seymour and Callaghan 1997), and has been used extensively to study structural and flow properties inside porous media (Song et al 2008;Gladden and Mitchell 2011;Codd and Seymour 2012). In this study, NMR is used to investigate the effect that colloidal particle deposition has on the flow properties inside a porous medium.…”