Abstract
The extraction of hydrocarbons from unconventional oil and gas reservoirs relies on a detailed understanding of the cracking processes in shale. Also, underground structures designed for nuclear waste repositories are often preferred to be in shale due to its characteristic low permeability. Specifically, how cracks initiate, propagate and coalesce in shale is of interest in these contexts. A series of unconfined compression tests were conducted on Opalinus shale extracted from the Mont Terri underground rock laboratory in Switzerland. These tests were performed on prismatic Opalinus shale specimens with one vertical flaw. High resolution imagery was used to capture crack initiation, -propagation and -coalescence. Digital Image Correlation (DIC) methods were used to determine deformation and crack initiation. By using static loading and unloading cycles, localized strains associated with cracking events were observed. The DIC analysis showed much more cracking than visual inspection with the naked eye. Additionally, a significant influence of bedding planes on the cracking patterns was observed.
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Acknowledgements
The research presented in this paper was supported by TOTAL SA. Their support and advice is gratefully acknowledged. We would also like to thank Swisstopo and the Mt. Terri Laboratory (Dr. Ch. Nussbaum) for making the Opalinus shale cores available to us.
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Morgan, S.P. (2017). Using Digital Image Correlation to Detect Cracking in Opalinus Shale. In: Zehnder, A., et al. Fracture, Fatigue, Failure and Damage Evolution, Volume 8. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-42195-7_18
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DOI: https://doi.org/10.1007/978-3-319-42195-7_18
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