Mechanism of NMR Relaxation of Fluids in Rock

Kleinberg, R. L., Kenyon, W. E., Mitra, P. P. (1994) Mechanism of NMR Relaxation of Fluids in Rock. Journal of Magnetic Resonance, Series A, 108 (2). pp. 206-214. ISSN 10641858 (ISSN)

DOI: 10.1006/jmra.1994.1112


A theory of the nuclear magnetic relaxation of fluids in the pore spaces of sedimentary rocks at low frequencies is presented. Because the materials studied are varied in their composition and cannot be thoroughly characterized, the theory cannot be considered as universally applicable; however, it is consistent with diverse experimental observations that are in the literature, many of which have not been heretofore explained. The multiexponential character of the NMR decays has earlier been found to be correlated with the heterogeneities in pore sizes which characterize most rocks. The heterogeneity length scale is larger than the diffusion length associated with NMR relaxation times. It is found that the most important relaxation mechanism arises from hyperfine interactions with paramagnetic ions such as Mn2+ and Fe3+ at the grain surfaces. Lack of a strong temperature dependence of the rates indicates that the diffusive motion of the fluid molecules or the on-off motion at a surface site do not enter into a determination of T1 and T2. The ratio T1-/T2 measured at low frequencies has been generally found to be significantly greater than 1. It is proposed that the explanation for this phenomenon lies in the fact that the scalar part of the hyperfine interaction is comparable to the dipolar part, because the latter is partially averaged due to the restricted rotational motion of the molecules at a surface site. © 1994 Academic Press. All rights reserved.

Item Type: Paper
Subjects: physics > fluid dynamics
Investigative techniques and equipment > magnetic resonance imaging
physics > biophysics > pore dynamics
CSHL Authors:
Communities: CSHL labs > Mitra lab
Depositing User: CSHL Librarian
Date: 1994
Date Deposited: 02 Apr 2012 21:10
Last Modified: 10 Feb 2017 20:34

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