Simulation and experimental measurements of internal magnetic field gradients and NMR transverse relaxation times (T2) in sandstone rocks

Connolly, Paul R. J.; Yan, Wei; Zhang, Dongke; Mahmoud, Mohamed; Verrall, Michael; Lebedev, Maxim; Iglauer, Stefan; Metaxas, Peter J.; May, Eric F.; Johns, Michael L.

doi:10.1016/j.petrol.2019.01.036

Cited by 54 publications

(35 citation statements)

References 38 publications

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“…In regard to quantitative analysis of pore size, a DDIF tool utilizing higher eigenmodes is developed by the signal difference from reference signal R and test signal E (Song 2003;Cho and Song 2008). Tests combining DDIF with other pulse sequences like CPMG are also used in studies of pore structure characterization and non-uniform field distribution (Zhang et al 2018;Connolly et al 2019). For qualitative analysis, a more direct away is combining processes Yan et al (2013) Image-based methods Reservation of mineral compositions makes it possible to capture short relaxation signal of different solid components Ogren (2013), Tiwari et al (2013) Geometric algorithms A kind of simplified method for study NMR response difference between pores and fissures with regular or simplified shape and structure Jia et al (2007) Statistics algorithms Simplified version of process-based methods with significant difference in geometrical characteristics among simulation results Sheidaei et al (2013) NMR response simulation…”

Section: Experimental Methodologiesmentioning

confidence: 99%

Advances in low-field nuclear magnetic resonance (NMR) technologies applied for characterization of pore space inside rocks: a critical review

et al. 2020

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NMR serves as an important technique for probing rock pore space, such as pore structure characterization, fluid identification, and petrophysical property testing, due to the reusability of cores, convenience in sample processing, and time efficiency in laboratory tests. In practice, NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation. The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations. This article first gives a brief description of the development history of relaxation theories and models for porous media. Then, the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented. Meanwhile, limitations and deficiencies of them are summarized. Finally, future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.

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Section: Experimental Methodologiesmentioning

confidence: 99%

Advances in low-field nuclear magnetic resonance (NMR) technologies applied for characterization of pore space inside rocks: a critical review

et al. 2020

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“…In aqueous solution, the bulk relaxation time usually ranges from 2,000 to 3,000 ms. Its contribution to the harmonic average, therefore, becomes negligible in comparison. Diffusion relaxation, caused by the Brownian movement of the proton spins in an inhomogeneous magnetic field, can be neglected in the presence of small gradients and short echo spacing during measurements 17,20,21 . Therefore, the dominant relaxation within the pore space is surface relaxation, which is a function of the surface‐to‐volume ratio ( S / V ) and surface relaxivity ( ρ 2 ).…”

Section: Methodsmentioning

confidence: 99%

Analysis of ZTE MRI application to sandstone and carbonate

et al. 2020

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Microtomography (μCT) and nuclear magnetic resonance (NMR) have been used to characterize porous media for decades. Magnetic resonance imaging (MRI) enables direct visualization of pore architecture and many pulse sequences exist. In this work, we tested the MRI pulse sequence Zero Echo Time (ZTE) to study sandstone and carbonate for its ability to address short relaxation times. We aimed at resolving two fluid conduit scales, that is, pores and fractures. In this research, we study tighter porous systems than those previously reported using ZTE. Additionally, pore cluster analysis (PCA), combined with ZTE, can be used to analyze pore‐fracture connectivity of relatively large core plugs. We show that ZTE can resolve two‐scale pore systems simultaneously, that is, fractures and pores. By combining time‐domain NMR pore‐size analysis and PCA, we show that careful selection of resolution is necessary to understand transport in porous media.

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“…A series of 180° RF pulses refocusses dephasing arising from inhomogeneity of the static magnetic field, generating a train of spin echoes which decay according to 2 . In this work we employed = 500 echoes separated by an echo time of = 100 µs; this short echo time, together with the low static magnetic field strength employed in this study, aimed to limit the influence of undesired transverse relaxation phenomena due to magnetic susceptibility contrast effects at the solid-liquid interface (Connolly et al, 2019;Mitchell et al, 2010). The resulting relaxation data are again described by a Fredholm integral equation of the first kind (Wilson, 1992),…”

Section: Nuclear Magnetic Resonance Relaxation Measurementsmentioning

confidence: 99%

“…As such, it offers opportunities for the development of robust approaches for monitoring CPB samples under early hydration conditions without the requirements for sample modifications, such as solvent exchange or oven drying, which may damage the material microstructure (Makar and Sato, 2013;Zhang and Scherer, 2011). Indeed, as the longitudinal and transverse NMR relaxation times T1 and T2 are both inherently sensitive to molecular dynamics (Kowalewski and Mäler, 2017), the relaxation characteristics of fluids confined to porous structures can provide unique insight into material structural properties, including pore size distributions and pore network connectivity (Connolly et al, 2019;Davies and Packer, 1990;Fridjonsson et al, 2013;Gallegos et al, 1987;Kleinberg et al, 1994;Kleinberg and Horsfield, 1990;McDonald et al, 2005;Monteilhet et al, 2006;Yao and Liu, 2012).…”

Section: Introductionmentioning

confidence: 99%

Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

Nasharuddin¹,

Luo²,

Robinson³

et al. 2021

Preprint

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Cemented paste backfill (CPB) comprising mineral tailings, binders and mixing waters is an important potential support material in the mining industry. As the mechanical properties of CPB are significantly influenced by its microstructural characteristics the development of measurement tools to better understand its pore structure evolution is important for its increased utilisation. This study reports the application of low-field nuclear magnetic resonance (NMR) relaxation time measurements to characterise the microstructural evolution of CPB materials over 56 days of hydration, contrasting common tap water and hypersaline water (~22 wt% salt) as mixing waters. Distinct NMR relaxation time populations were evidenced within each CBP sample, revealing the presence of both capillary (T1,2 ≈ 10 ms) and gel pore water (T1,2 ≈ 300 – 500 µs), with time-dependent relaxation measurements facilitating characterisation of capillary pore structure evolution over the hydration period assessed. Hypersaline samples demonstrated a time-lag in this measured capillary pore evolution, relative to those hydrated with tap water, while hydration rates were observed to increase with increased CPB binder content. Further, both T1 and T2 NMR relaxation times were found to correlate with the uniaxial compressive strength of the CPB materials investigated, facilitating the formulation of a predictive correlation function between NMR relaxation characteristics and mechanical properties.

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Simulation and experimental measurements of internal magnetic field gradients and NMR transverse relaxation times (T2) in sandstone rocks

Cited by 54 publications

References 38 publications

Advances in low-field nuclear magnetic resonance (NMR) technologies applied for characterization of pore space inside rocks: a critical review

Advances in low-field nuclear magnetic resonance (NMR) technologies applied for characterization of pore space inside rocks: a critical review

Analysis of ZTE MRI application to sandstone and carbonate

Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

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