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Direct and Microseismic Observations of Hydraulic Fracturing in Barre Granite and Opalinus Clayshale

Li, Bing Q. and Einstein, Herbert H. (2019) Direct and Microseismic Observations of Hydraulic Fracturing in Barre Granite and Opalinus Clayshale. Journal of Geophysical Research. Solid Earth, 124 (11). pp. 11900-11916. ISSN 2169-9313.

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While hydraulic fracturing is a well‐established and widely implemented process, there are still some aspects that can be better understood. Specifically, researchers do not fully understand the relation between the hydraulic fracture network and the microseismic events induced during hydraulic stimulation. In this laboratory study, we address this knowledge gap by conducting hydraulic fracturing experiments where we directly observe microstructural changes using a high‐speed camera attached to a 5X magnification lens and analyze the images using a digital image correlation code. These data are compared to simultaneously acquired acoustic emissions, from which we infer the location and focal mechanisms of induced microseismic events. Experiments were conducted on Opalinus clayshale and Barre granite, at injection rates of 0.019 and 0.39 ml/s for each rock. The simultaneous recording of microseismic and visual observations is unique and provides significant insight into the details of hydraulic fracturing. Our results show several interesting differences between granite and shale, and between injection rates. For example, we find that while the creation of hydraulic fractures is generally considered as tensile at the field scale, evidence of shearing can be observed to varying degrees at the microstructural scale. Specifically, we see that microstructural shearing is more evident in granite in the form of distinct en echelon microcracks. On the effect of the injection rate, we find that a reduced injection rate tends to create a more complex network of microcracks, along with a lower proportion of double‐couple (shear) focal mechanisms in the microseismic data.

Item Type:Article
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URLURL TypeDescription set
Li, Bing Q.0000-0002-4158-4941
Einstein, Herbert H.0000-0003-4074-4736
Additional Information:© 2019 American Geophysical Union. Received 15 JUL 2019; Accepted 10 SEP 2019; Accepted article online 12 SEP 2019; Published online 30 NOV 2019. The authors would like to thank Total SA and the Abu Dhabi National Oil Company for funding this research. We would also like to thank the Mont Terri rock laboratory for their generous donation of Opalinus clayshale. Additionally, many thanks to two anonymous reviewers and editor Doug Schmitt for excellent suggestions on the manuscript. Finally, we would like to thank Wei Li and Omar Aldajani for their assistance with experiments, and John Germaine, Brian Evans, and German Prieto for invaluable advice. The data set can be found online (
Funding AgencyGrant Number
Abu Dhabi National Oil CompanyUNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20191216-140015379
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Official Citation:Li, B. Q., & Einstein, H. H. (2019). Direct and microseismic observations of hydraulic fracturing in Barre granite and Opalinus clayshale. Journal of Geophysical Research: Solid Earth, 124, 11900–11916.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100306
Deposited By: Tony Diaz
Deposited On:16 Dec 2019 22:09
Last Modified:04 May 2020 17:40

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