TY - JOUR
T1 - Laboratory hydraulic fracturing of granite
T2 - Acoustic emission observations and interpretation
AU - Li, Bing Q.
AU - Gonçalves da Silva, Bruno
AU - Einstein, Herbert
N1 - Funding Information:
The research presented in this paper was supported by TOTAL S.A., France. The authors would like to express their sincere gratitude for this support. We would also like to thank Professors John Germaine and German Prieto for the insights and suggestions.
Publisher Copyright:
© 2019 Elsevier Ltd
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/3/15
Y1 - 2019/3/15
N2 - Hydraulic fracturing is routinely used, but the fracturing processes that occur when rocks are hydraulically-fractured are not entirely understood and require further investigation. This study presents the acquisition, analysis and interpretation of acoustic emissions data from a series of laboratory hydraulic fracturing experiments on granite. Specimens with different orientations of two pre-cut flaws were tested under both 0 MPa and 5 MPa of vertical uniaxial stress to understand the effect of the external stress conditions. Acoustic emissions data are related to corresponding visual observations made using high-resolution and high-speed imaging. We find that in general, (1) the AE begin to occur at approximately 80% of peak pressure, (2) the focal mechanisms suggest that 55–60% of the radiation pattern could be explained by a double couple mechanism and is well-explained by simulation results, (3) hypocenter locations tended to agree well with visually observed white patching (process zone) and crack patterns, (4) spatio-temporal analysis revealed points in time at which microcrack coalescence were detected by AE, (5) that the AE could be used to make a non-unique prediction of crack initiation, and lastly (6) that exponential AE energy accumulation in the last 5–10 s prior to crack initiation can be modelled by time-to-failure methods.
AB - Hydraulic fracturing is routinely used, but the fracturing processes that occur when rocks are hydraulically-fractured are not entirely understood and require further investigation. This study presents the acquisition, analysis and interpretation of acoustic emissions data from a series of laboratory hydraulic fracturing experiments on granite. Specimens with different orientations of two pre-cut flaws were tested under both 0 MPa and 5 MPa of vertical uniaxial stress to understand the effect of the external stress conditions. Acoustic emissions data are related to corresponding visual observations made using high-resolution and high-speed imaging. We find that in general, (1) the AE begin to occur at approximately 80% of peak pressure, (2) the focal mechanisms suggest that 55–60% of the radiation pattern could be explained by a double couple mechanism and is well-explained by simulation results, (3) hypocenter locations tended to agree well with visually observed white patching (process zone) and crack patterns, (4) spatio-temporal analysis revealed points in time at which microcrack coalescence were detected by AE, (5) that the AE could be used to make a non-unique prediction of crack initiation, and lastly (6) that exponential AE energy accumulation in the last 5–10 s prior to crack initiation can be modelled by time-to-failure methods.
UR - http://www.scopus.com/inward/record.url?scp=85060696880&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85060696880&partnerID=8YFLogxK
U2 - 10.1016/j.engfracmech.2019.01.034
DO - 10.1016/j.engfracmech.2019.01.034
M3 - Article
AN - SCOPUS:85060696880
SN - 0013-7944
VL - 209
SP - 200
EP - 220
JO - Engineering Fracture Mechanics
JF - Engineering Fracture Mechanics
ER -