A numerical study of field strength and clay morphology impact on NMR transverse relaxation in sandstones

Cui, Yingzhi; Shikhov, Igor; Li, Rupeng; Liu, Shitao; Arns, Christoph H.

doi:10.1016/j.petrol.2021.108521

Cited by 14 publications

(13 citation statements)

References 34 publications

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“…3a, b) in the micro-CT image due to resolution limitations. We employ a 3D reconstruction technique (Cui et al 2021) based on SEM images to overcome these limitations. Kaolinite booklets are distributed following a Boolean process with random unit rotation angles (Cui et al 2021).…”

Section: Kaolinite Modelmentioning

confidence: 99%

“…We employ a 3D reconstruction technique (Cui et al 2021) based on SEM images to overcome these limitations. Kaolinite booklets are distributed following a Boolean process with random unit rotation angles (Cui et al 2021). Individual kaolinite platelets as constituents of the booklets are approximated as hexagonal plates with thickness of about 60 nm and diameter of 2-3 μm.…”

Section: Kaolinite Modelmentioning

confidence: 99%

“…Calculating highresolution internal magnetic fields then must consider near-field effects at intermediate scales. We note that resolving the micro-structure of kaolinite requires resolution of the order of 20 nm (Cui et al 2021). A direct approach using, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…For such an approach, it would be desirable to replace effective clay parameters with clay structure and surface properties. A first step in this direction has been presented by Cui et al (2021), where a dual-scale model of Bentheimer sandstone described the heterogeneity of the rock including micro-porosity in clay regions. However, a multi-stage approach was used for the simulation of the NMR responses.…”

Section: Introductionmentioning

confidence: 99%

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NMR Relaxation Modelling in Porous Media with Dual-Scale-Resolved Internal Magnetic Fields

2022

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A pore-scale forward modelling approach for NMR relaxation responses of sandstones incorporating their dual-scale nature is presented. The approach utilises X-ray micro-CT images to capture inter-granular porosity and scanning electron microscopy images to reconstruct clay regions via a resolved clay micro-structure model. A key to calculating the NMR response with resolved clay micro-structure is the development of a dual-scale internal magnetic field calculation. This is achieved by a separation of near- and far-field effects in a dipole approximation of the internal field with periodic clay micro-structures, the latter of which take local clay pocket porosity into account. Tri-linear interpolation of the micro-CT image before calculation of the internal magnetic field further reduces errors in the transition regions between coarse- and fine-scale structure, with final discretisation level matching the fine-scale clay micro-structure model across the whole domain. The method is validated against direct calculations of model media at full resolution and applied to Bentheimer sandstone. Measured and simulated NMR $$T_2$$ T 2 relaxation responses, including relaxation time distribution shape, are in excellent agreement and distributions of internal magnetic field gradients at the highest spatial resolution as well as diffusion-averaged effective gradients are reported.

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Section: Kaolinite Modelmentioning

confidence: 99%

Section: Kaolinite Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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NMR Relaxation Modelling in Porous Media with Dual-Scale-Resolved Internal Magnetic Fields

2022

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“…This can be seen in some recent references. [1][2][3][4][5] Here, we focus on the network of a simple clay, namely, kaolinite, using a different NMR approach based on the nutation phenomenon. It was very early demonstrated by Torrey [6] that nutation experiments, through their dependence on relaxation parameters (R 1 , the longitudinal relaxation rate and R 2 , the transverse relaxation rate), could be able to discriminate between different species which may share identical (or almost identical) chemical shifts.…”

Section: Introductionmentioning

confidence: 99%

Longitudinal relaxation rate measurements for different signals unveiled by nutation spectroscopy: Application to the characterization of two arrangements experienced by water in a clay network

Ferrari

Moyne

Canet

2021

Magnetic Reson in Chemistry

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Nutation consists in monitoring the motion of nuclear magnetization under the application of a radiofrequency (rf) field. With an appropriate amplitude of the rf field, the nutation frequency depends on the NMR relaxation times. This property offers the possibility of differentiating species having the same Larmor frequency but differing by their relaxation times. This may occur for the composite proton NMR signal of water in complex systems. Separate nutation signals are thus observed with the possibility of measuring their longitudinal relaxation times by simply applying a saturation hard pulse, followed by an evolution interval, prior to the nutation sequence. This novel experiment has been used for studying the two sites existing for water in two kaolinite samples (one hydrated after stabilization of several months and the other nonhydrated). It turns out that water in these two sites differs essentially by its transverse relaxation time. Moreover, recovery is surprisingly biexponential for these two signals. A proper analysis of results obtained by this saturationrecovery nutation experiment provides not only the specific longitudinal relaxation rates of water in these two sites but also information about the averaging which occurs at long evolution times. This is discussed with regard of the structure and organization of the clay network. In particular, from relaxation rates at short evolution times, it is shown that this network is mainly constituted of ordered platelets, with a relatively weak proportion of randomly distributed platelets.

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NMR transverse relaxation of the clay-rich shale in inhomogeneous magnetic field: A numerical study

Zhang

Liu

et al. 2022

Computers & Geosciences

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A numerical study of field strength and clay morphology impact on NMR transverse relaxation in sandstones

Cited by 14 publications

References 34 publications

NMR Relaxation Modelling in Porous Media with Dual-Scale-Resolved Internal Magnetic Fields

NMR Relaxation Modelling in Porous Media with Dual-Scale-Resolved Internal Magnetic Fields

Longitudinal relaxation rate measurements for different signals unveiled by nutation spectroscopy: Application to the characterization of two arrangements experienced by water in a clay network

NMR transverse relaxation of the clay-rich shale in inhomogeneous magnetic field: A numerical study

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