High‐resolution fracture aperture mapping using optical profilometry. Issue 10 (2nd October 2013)

• Record Type: Journal Article
• Authors: Ameli, Pasha; Elkhoury, Jean E.; Detwiler, Russell L.
• Is Part Of: Water resources research. Volume 49:Issue 10(2013:Oct.)
• Page Start: 7126
• Page End: 7132
• Publication Date: 2013-10-02
• Subjects: Hydrology -- Periodicals; 333.91
• DOI: 10.1002/wrcr.20501
• Languages: English
• ISSNs: 0043-1397

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>[1] Fractures play an important role in the Earth's crust, often controlling both mechanical and transport processes. Developing a mechanistic understanding of these processes requires quantifying the roughness of fracture surfaces and the contacts and void spaces between fracture surfaces at high spatial resolution (10s of microns) over a broad range of scales (centimeters to meters). Here we present a scalable method for measuring fracture surfaces and reconstructing fracture aperture fields using an optical profilometer. We evaluate the method by measuring two fractured limestone cores; one is a tensile fracture with strong cross correlation between the surfaces and the other is a saw‐cut, sand‐blasted fracture with negligible cross correlation between the surfaces. Results of repeated measurements of these two fractures suggest that well‐correlated surfaces, where the correlation between the surfaces can aid reconstruction, can be reproduced with local uncertainties with median standard deviation of <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t950m2v" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:00431397:media:wrcr20501:wrcr20501-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>8</mml:mn><mml:mo> </mml:mo><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi><mml:mo> </mml:mo></mml:mrow></mml:math></alternatives>. Poorly correlated surfaces, where reconstruction relies solely upon the precision of the placement of the halves of the core on the profilometer stage, can be reproduced with local uncertainties with median standard deviation of <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t950m0r" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:00431397:media:wrcr20501:wrcr20501-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>20</mml:mn><mml:mo> </mml:mo><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi><mml:mo> </mml:mo></mml:mrow></mml:math></alternatives>. Additionally, we quantified the accuracy of the technique by comparing calculated aperture profiles of a fractured concrete core to thin sections cut from the core after impregnating it with epoxy. The median deviation between the two measurements, which includes errors due to residual misalignment of the profiles, was <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t950m19" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:00431397:media:wrcr20501:wrcr20501-math-0003" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>29</mml:mn><mml:mo> </mml:mo><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi><mml:mo> </mml:mo></mml:mrow></mml:math></alternatives> supporting the accuracy of the method. Our results emphasize the potential for using noncontact surface measurement techniques to accurately and precisely reconstruct fracture apertures over a wide range of length scales.</p> </abstract>