ABSTRACT
The most promising method to know the extension and orientation of the fracture is fracture mapping based on the interpretation of acoustic activity observed during hydraulic fracturing. The principle is to locate the discrete acoustic events recorded during the fracturing phases i.e. creation, propagation and fracture closure. This acoustic activity can be recorded at the ground level, in neighbour wells or more often in the treated well. Acoustic activity is closely correlated to the fracturing phases. An interesting observation concerns the polarization of the accelerometer signals for each acoustic event. The accelerometers associated with their amplifiers indicate a negative pulse when they are submitted to a compression and a positive pulse for a dilatation. When a fracture is created or when it begins to propagate, the recorded acoustic polarities indicate a tensile mechanism. But at fracture closure, the events polarities are more complicated and imply compression as well as shear mechanisms.
