Details
| Original language | English |
|---|---|
| Article number | ggaf154 |
| Number of pages | 15 |
| Journal | Geophysical journal international |
| Volume | 242 |
| Issue number | 1 |
| Early online date | 30 Apr 2025 |
| Publication status | Published - Jul 2025 |
Abstract
This study investigates the longitudinal (T1) to transverse (T2) relaxation time ratios in unconsolidated geological materials to determine how they vary across different geological units. Assessing the T1/T2 ratio can inform about the validity of the presumed relationship between T1 and T2 relaxation times in steady-state surface nuclear magnetic resonance (NMR) modelling (i.e.T1/T2 ratio is assumed to be constant and equal to one). The T1/T2 ratio investigation is conducted by 2-D T1–T2 correlation data using laboratory and borehole NMR measurements at a Larmor frequency of 2 MHz and 430 kHz, respectively. Laboratory NMR measurements were performed on 73 sediment samples from nine sites in Denmark and Germany, and borehole NMR measurements were conducted at 59 selected depth intervals in unconsolidated geological units across eight sites in the same countries. Volumetric magnetic susceptibility of the laboratory samples was measured to evaluate the effects of magnetic susceptibility on the T1/T2 ratio. Our results indicate that the T1/T2 ratios in mineral soils and sediments are pretty similar for borehole NMR and lab NMR data sets, regardless of the geological unit. In these geological materials, the mean value of the T1/T2 ratios is 1.64 in lab-NMR and 1.82 in borehole NMR data sets. In contrast, in our in-situ borehole NMR measurements in organic peat soils, the mean value of the T1/T2 ratios was higher (i.e. 2.77), exhibiting a broader distribution ranging from 1 to 4.8. Moreover, we observed that magnetic susceptibility did not have a significant effect on the T1/T2 ratio in the investigated samples. More importantly, the findings in this study can be adopted in the modelling of steady-state surface NMR modelling routines where a constant ratio of 1 for T1/T2 is assumed when solving the Bloch equations. It is expected that updating the T1/T2 ratio can improve the accuracy of water content and relaxation time estimations derived from steady-state surface NMR measurements.
Keywords
- Downhole methods, Hydrogeophysics, Magnetic properties, Statistical methods
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Geophysical journal international, Vol. 242, No. 1, ggaf154, 07.2025.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Longitudinal to transverse relaxation time ratio (T1/T2) in unconsolidated geological materials
T2 - a perspective from 2-D borehole and laboratory NMR measurements
AU - Mashhadi, Seyyed Reza
AU - Keating, Kristina
AU - Müller-Petke, Mike
AU - Hiller, Thomas
AU - Costabel, Stephan
AU - Parra, Andres Ospina
AU - Grombacher, Denys
N1 - Publisher Copyright: © The Author(s) 2025. Published by Oxford University Press on behalf of The Royal Astronomical Society.
PY - 2025/7
Y1 - 2025/7
N2 - This study investigates the longitudinal (T1) to transverse (T2) relaxation time ratios in unconsolidated geological materials to determine how they vary across different geological units. Assessing the T1/T2 ratio can inform about the validity of the presumed relationship between T1 and T2 relaxation times in steady-state surface nuclear magnetic resonance (NMR) modelling (i.e.T1/T2 ratio is assumed to be constant and equal to one). The T1/T2 ratio investigation is conducted by 2-D T1–T2 correlation data using laboratory and borehole NMR measurements at a Larmor frequency of 2 MHz and 430 kHz, respectively. Laboratory NMR measurements were performed on 73 sediment samples from nine sites in Denmark and Germany, and borehole NMR measurements were conducted at 59 selected depth intervals in unconsolidated geological units across eight sites in the same countries. Volumetric magnetic susceptibility of the laboratory samples was measured to evaluate the effects of magnetic susceptibility on the T1/T2 ratio. Our results indicate that the T1/T2 ratios in mineral soils and sediments are pretty similar for borehole NMR and lab NMR data sets, regardless of the geological unit. In these geological materials, the mean value of the T1/T2 ratios is 1.64 in lab-NMR and 1.82 in borehole NMR data sets. In contrast, in our in-situ borehole NMR measurements in organic peat soils, the mean value of the T1/T2 ratios was higher (i.e. 2.77), exhibiting a broader distribution ranging from 1 to 4.8. Moreover, we observed that magnetic susceptibility did not have a significant effect on the T1/T2 ratio in the investigated samples. More importantly, the findings in this study can be adopted in the modelling of steady-state surface NMR modelling routines where a constant ratio of 1 for T1/T2 is assumed when solving the Bloch equations. It is expected that updating the T1/T2 ratio can improve the accuracy of water content and relaxation time estimations derived from steady-state surface NMR measurements.
AB - This study investigates the longitudinal (T1) to transverse (T2) relaxation time ratios in unconsolidated geological materials to determine how they vary across different geological units. Assessing the T1/T2 ratio can inform about the validity of the presumed relationship between T1 and T2 relaxation times in steady-state surface nuclear magnetic resonance (NMR) modelling (i.e.T1/T2 ratio is assumed to be constant and equal to one). The T1/T2 ratio investigation is conducted by 2-D T1–T2 correlation data using laboratory and borehole NMR measurements at a Larmor frequency of 2 MHz and 430 kHz, respectively. Laboratory NMR measurements were performed on 73 sediment samples from nine sites in Denmark and Germany, and borehole NMR measurements were conducted at 59 selected depth intervals in unconsolidated geological units across eight sites in the same countries. Volumetric magnetic susceptibility of the laboratory samples was measured to evaluate the effects of magnetic susceptibility on the T1/T2 ratio. Our results indicate that the T1/T2 ratios in mineral soils and sediments are pretty similar for borehole NMR and lab NMR data sets, regardless of the geological unit. In these geological materials, the mean value of the T1/T2 ratios is 1.64 in lab-NMR and 1.82 in borehole NMR data sets. In contrast, in our in-situ borehole NMR measurements in organic peat soils, the mean value of the T1/T2 ratios was higher (i.e. 2.77), exhibiting a broader distribution ranging from 1 to 4.8. Moreover, we observed that magnetic susceptibility did not have a significant effect on the T1/T2 ratio in the investigated samples. More importantly, the findings in this study can be adopted in the modelling of steady-state surface NMR modelling routines where a constant ratio of 1 for T1/T2 is assumed when solving the Bloch equations. It is expected that updating the T1/T2 ratio can improve the accuracy of water content and relaxation time estimations derived from steady-state surface NMR measurements.
KW - Downhole methods
KW - Hydrogeophysics
KW - Magnetic properties
KW - Statistical methods
UR - http://www.scopus.com/inward/record.url?scp=105004883067&partnerID=8YFLogxK
U2 - 10.1093/gji/ggaf154
DO - 10.1093/gji/ggaf154
M3 - Article
AN - SCOPUS:105004883067
VL - 242
JO - Geophysical journal international
JF - Geophysical journal international
SN - 0956-540X
IS - 1
M1 - ggaf154
ER -