Hydraulic Fracture Orientation Using Passive Borehole Seismics

Passive borehole seismometry enables mapping the orientation of induced hydraulic fracture planes by using a triaxial seismometer clamped in the treatment well to map acoustic emissions from the fracture. Presently, the method utilizes only those seismic events attributable to shear failure along the fracture plane which exhibit both compressional and shear wave phases. The fracture azimuth is seen to parallel the polarization of the compressional wave phase. Whereas other geophysical techniques used to determine fracture orientation are principally surface-deployed measurements and, therefore, lose their effectiveness as the fracture depth exceeds 1500-2000 meters, the borehole seismic has worked effectively at 3300 meters in past applications. The method, principally, gives only fracture azimuth as is demonstrated by two examples of field test data.