TY  - JOUR
ID  - epos2045
UR  - http://doi.org/10.1007/s00603-017-1285-0
IS  - 11
A1  - Lopez-Comino, Jose Angel
A1  - Cesca, Simone
A1  - Heimann, Sebastian
A1  - Grigoli, Francesco
A1  - Milkereit, Claus
A1  - Dahm, Torsten
A1  - Zang, Arno
N2  - A crucial issue to characterize hydraulic fractures is the robust, accurate and automated detection and location of acoustic emissions (AE) associated with the fracture nucleation and growth process. Waveform stacking and coherence analysis techniques are here adapted using massive datasets with very high sampling (1 MHz) from a hydraulic fracturing experiment that took place 410 m below surface in the Äspö Hard Rock Laboratory (Sweden). We present the results obtained during the conventional, continuous water injection experiment Hydraulic Fracture 2. The resulting catalogue is composed of more than 4000 AEs. Frequency?magnitude distribution from AE magnitudes (MAE) reveals a high b value of 2.4. The magnitude of completeness is also estimated approximately MAE 1.1, and we observe an interval range of MAE between 0.77 and 2.79. The hydraulic fractures growth is then characterized by mapping the spatiotemporal evolution of AE hypocentres. The AE activity is spatially clustered in a prolate ellipsoid, resembling the main activated fracture volume (~105 m3), where the lengths of the principal axes (a = 10 m; b = 5 m; c = 4 m) define its size and its orientation can be estimated for a rupture plane (strike ~123°, dip ~60°). An asymmetric rupture process regarding to the fracturing borehole is clearly exhibited. AE events migrate upwards covering the depth interval between 404 and 414 m. After completing each injection and reinjection phase, the AE activity decreases and appears located in the same area of the initial fracture phase, suggesting a crack-closing effect.
VL  - 50
TI  - Characterization of Hydraulic Fractures Growth During the Äspö Hard Rock Laboratory Experiment (Sweden)
AV  - none
EP  - 3001
Y1  - 2017///
PB  - Springer Verlag
JF  - Rock Mechanics and Rock Engineering
KW  - Hydraulic fracturing Äspo Hard Rock Laboratory Induced seismicity Detection and location algorithms
SN  - 0723-2632
SP  - 2985
ER  -