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Fluid saturation-dependent nuclear magnetic resonance spin-lattice relaxation in porous media and pore structure analysis (1993)

Chen, Songhua ; Liaw, Hsie-Keng ; Watson, A. Ted

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 74 (1993), S. 1473-1479

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Nuclear-magnetic-resonance spin-lattice relaxation measurements were conducted in a Bentheimer sandstone sample for drainage experiments involving gas-liquid fluid phases with ten different saturation levels ranging from complete water saturation (Sw=1) down to Sw=0.14. A monotonic decrease in relaxation times was observed as the water saturation was lowered over this broad saturation range. This phenomenon is explained by considering that for a drainage process the liquid (wetting) phase was drained from different-sized pores at different saturations with larger pores being drained first. The relaxation decay curves corresponding to each saturation state were analyzed using both stretched exponential and discrete multiexponential functions. In particular, the effect due to bulk fluid relaxation was eliminated so that a more appropriate relationship between pore size distribution and the relaxation rate is obtained. From these analyses, the relative variation of pore size distributions corresponding to different saturation levels was obtained. A power-law dependence of saturation with relaxation times is observed which indicates that the relaxation analysis can be used to characterize fluid saturations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.354845

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Characterization of fluid distributions in porous media by NMR techniques (1996)

Liaw, Hsie-Keng ; Kulkarni, Raghavendra ; Chen, Songhua ; [et al.]

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 42 (1996), S. 538-546

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Nuclear magnetic resonance (NMR) spin-lattice relaxation measurements are used to investigate pore structures and fluid phase distributions in porous media. A new method for estimating relaxation time distribution functions from measured relaxation data is presented using a B-spline basis to represent the distribution function and Tikhonov regularization to stabilize the estimation problem. Surface relaxivity, which is required to convert relaxation time distributions to pore-size distributions of fluid phase distributions at partial saturations, is determined using pore volume-to-surface-area ratios estimated by NMR diffusion measurements. This approach was validated by analyzing certain model porous media with known pore volume-to-surface-area ratios. The method is demonstrated by determining pore-size and fluid phase distributions of sandstone and carbonate samples, as well as by comparing the pore-size distributions of chalk samples obtained by this methodology with those estimated by mercury porosimetry.

Additional Material: 10 Ill.