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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Sandstone surface relaxivity determined by NMR T-2 distribution and digital rock simulation for permeability evaluation

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Lucas-Oliveira, Everton [1] ; Araujo-Ferreira, Arthur G. [1] ; Trevizan, Willian A. [2] ; Coutinho dos Santos, Bernardo C. [2] ; Bonagamba, Tito J. [1]
Total Authors: 5
[1] Univ Sao Paulo, Sao Carlos Inst Phys, POB 369, BR-13560970 Sao Carlos, SP - Brazil
[2] CENPES PETROBRAS, BR-21941915 Rio De Janeiro, RJ - Brazil
Total Affiliations: 2
Document type: Journal article
Web of Science Citations: 7

Many of the world's oil reservoirs are sandstones and some equations have been widely explored to estimate their permeability from NMR measurements, especially those based on the Schlumberger Doll Research (SDR) and Timur-Coates models. In both cases, the permeability is assumed to be related to pore sizes. Brownstein and Tarr showed that, under fast diffusion regime, the NMR transverse relaxation time is proportional to the pore size and the proportionality constant is defined by the interaction fluid/surface and represented by the surface relaxivity rho. However, although there are several methods in the literature to estimate rho, no standard methods have been established so far, to our knowledge. In this work, we estimated surface relaxivity by combining experimental and simulated NMR data using a recently developed computational method to emulate the NMR signal of fluids within Digital Rocks. In addition, we analyzed the correlation between the pore radii and the experimentally measured gas permeability. Comparing Schlumberger and Timur-Coates models for permeability prediction, we propose that the macro and microporosity intensities identified in the T-2 distribution are correlated with characteristics of the sandstone surface. Thus, sandstone surface relaxivity can be estimated using the ratio of macro and microporosity intensities from NMR and, consequently, the pore size distribution can be obtained using only T-2 distribution data. (AU)

FAPESP's process: 12/00380-5 - Evaluation of resistance to cyclic fatigue of rotary and reciprocal systems
Grantee:Idomeo Bonetti Filho
Support type: Regular Research Grants
FAPESP's process: 12/02208-5 - Quantum information processing via nuclear magnetic resonance
Grantee:Tito José Bonagamba
Support type: Regular Research Grants