Lopez-Comino, Jose Angel and Cesca, Simone and Heimann, Sebastian and Grigoli, Francesco and Milkereit, Claus and Dahm, Torsten and Zang, Arno (2017) Characterization of Hydraulic Fractures Growth During the Äspö Hard Rock Laboratory Experiment (Sweden). Rock Mechanics and Rock Engineering, 50 (11). pp. 2985-3001. DOI: https://doi.org/10.1007/s00603-017-1285-0
Full text not available from this repository.Abstract
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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | Hydraulic fracturing Äspo Hard Rock Laboratory Induced seismicity Detection and location algorithms |
| Subjects: | Methodology > Method and procesing > Technology-seismicity interaction Inducing technology > Geothermal energy production Methodology > Method and procesing |
| Project: | SHEER project |