Microsismic and Acoustic Activity Associated with Hydraulic Fracture Propagation
Sismic and acoustic sources activated by the development of hydraulic fractures are discussed. It is shown that acoustic activity associated with crack extension should be high frequency; its existence depends upon pressure distribution at crack tip. For permeable fractured material, the increment in pore pressure in the vicinity of the hydraulic fracture may lead to some local slips which, in turn, can generate signals.
The frequency spectrum of these signals depends on the amount of injected volume and injection duration. In situ experiments carried out to investigate the possibility of mapping this activity in order to determine orientation and extent of a hydraulic fracture are presented. By comparison with previously published results, it is concluded that hydrophones are not appropriate for monitoring this type of acoustic activity. Further no low frequency induced seismicity has been observed although up to 12 m3 meters have been injected.
KeywordsRock Mass Stress Intensity Factor Pore Pressure Hydraulic Fracture Major Principal Stress
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