Ultrasonic Transmitter
While seismic receivers (geophones, accelerometers, AE sensors) are able to record passive seismic signals, they are also suitable to record active signals, i.e. man-made signals emitted in order to scan the rock volume.
In the BRP project, we aim at installing sources within the monitoring boreholes that are suitable for cementation and emit in the long term a repeatable signal. Because we are interested in the evolution of fracture geometries of centimeter to meter scale, the source should come with a considerable bandwidth. For this reason, we install ultrasonic transmitter manufactured by GMuG and retrofitted to withstand the pressures in BRP. GMuG is specialized on developing custom-made sensors in underground experiments. The transmitters are based on piezoelectric ceramics that emit after receiving a 1200 V delta impulse, a stress wave similar to seismic waves. Two transmitters are placed per borehole and distributed in such a way that the reservoir center is fully scanned from all directions.