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Impact of the cracks lost in the imaging process on computing linear elastic properties from 3D microtomographic images of Berea Sandstone

Yang Zhang and M. Nafi Toksoz
Impact of the cracks lost in the imaging process on computing linear elastic properties from 3D microtomographic images of Berea Sandstone
Geophysics (April 2012) 77 (2): R95-R104

Abstract

With the current developments in imaging/computational techniques and resources, computational rock physics has been emerging as a new field of study. Properties of rocks are examined by carrying out extensive numerical simulations on rocks that have been digitized using high-resolution X-ray CT scans. The ultimate goal of computational rock physics is to supplement the traditional laboratory measurements, which are time consuming, with faster numerical simulations that allow the parameter space to be explored more thoroughly. We applied the finite-element method to compute the static effective elastic properties from 3D microtomographic images of Berea sandstone saturated with different fluids. From the computations, we found discrepancies between the numerical results and the laboratory measurements. The reason for such a problem is the loss of small features, such as fine cracks and micropores, in the digitized matrix during the imaging and aggregation process. We used a hybrid approach, combining the numerical computation and the effective media theories--the differential effective medium model and the Kuster-Toksoz model--to deduce the lost cracks by a very fast simulated annealing method. We analyzed the sensitivity of the inverted results--the distributions of crack aspect ratios and concentrations--to the clay content. We found that the inverted crack distribution is not so sensitive to clay content. Compared with the effect of cracks on the computed effective elastic properties, clay has only a secondary effect. Our approach can recover the lost cracks and is capable of predicting the effective elastic properties of the rocks from the microtomographic images for different fluid saturations. Compared with the traditional inversion schemes, based only on the effective media theories, this hybrid scheme has the advantage of utilizing the complex microstructures that are resolved in the imaging process, and it helps define the inversion space for crack distribution.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 77
Serial Issue: 2
Title: Impact of the cracks lost in the imaging process on computing linear elastic properties from 3D microtomographic images of Berea Sandstone
Affiliation: Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States
Pages: R95-R104
Published: 201204
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 31
Accession Number: 2012-059465
Categories: Applied geophysicsEngineering geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N38°25'00" - N42°00'00", W84°49'60" - W80°31'60"
N39°43'00" - N42°17'60", W80°31'60" - W74°40'00"
N37°15'00" - N40°40'00", W82°30'00" - W77°45'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201231
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