Spatially resolved T1 relaxation measurements in reservoir cores

Diffusion in brine‐saturated reservoir cores studied by NMR imaging

“…In addition, the limestone core yields a symmetric distribution of pixel diffusion coefficients, but the sandstone core exhibits a distinctly asymmetric distribution. Similar effects have been observed for TI values (Attard et al, 1991b) and have been attributed to the presence of the shale band in the sandstone core. Values of the apparent diffusion coefficient in the shale-band region are approximately half of that in the rest of the core.…”

Inverting MRI measurements to heterogeneity spectra

“…Relaxation decay in individual voxels is typically multiexponential, as has been observed previously [33][34][35][36][37]. Several options are available for fitting and analyzing these decay curves.…”

“…For water-saturated rocks, CPMG measurements provide insight into the total porosity and distribution of pore sizes [17,20,[22][23][24][25][26][27][28][29][30][31]. The spatial resolution afforded by MRI can be used to extend these techniques from the bulk to permit measurement of the spatial variation of these petrophysically relevant quantities [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46].…”

Magnetic resonance in porous media: Recent progress

“…The T 2 from each voxel is combined to form a MRI-based T 2 distribution and compared to Laplace inversion of the CPMG signal from whole samples. It is important to note that functions such as a double exponential or stretched exponential 76,77,80,85,86 may not describe the full T 2 distribution, but they do represent some average properties of the T 2 distribution such as the mean T 2 and the width. 86 The analysis has shown that the MRI-based T 2 distribution agrees quite well with the Laplace inversion result 86 ͓Fig.…”

“…By measuring the variation of NMR parameters ͑porosity, relaxation, diffusion, etc.͒ over different physical locations within the sample, MRI can provide a description of spatial heterogeneity. [76][77][78][79][80][81][82][83][84][85][86] Additionally, the spatial correlation of these parameters may provide a new means of assessing structure and heterogeneity.…”