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Random Walks for Magnetic Decay in Porous Media

Published online by Cambridge University Press:  10 February 2011

Weicheng Cai
Affiliation:
Exxon Research and Engineering Co., Annandale, NJ 08801
Thomas C. Halsey
Affiliation:
Exxon Research and Engineering Co., Annandale, NJ 08801
John H. Hardenbergs
Affiliation:
Exxon Research and Engineering Co., Annandale, NJ 08801
Michael Leibig
Affiliation:
Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106
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Abstract

We propose a Monte Carlo method to simulate the magnetization decay for NMR in porous media. In this method, the diffusive spins in the fluid phase are modeled by 3-d random walkers, whose absorption at the solid surface simulates surface-mediated decay. Our method is 20 times faster than direct relaxation of the diffusion equation when a variable-step size implementation is used. We demonstrate our method by computing the surface relaxivity ρ for a Fontainebleau sandstone, whose structure was determined by X-ray tomography.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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