THE PH-44/52/70 PIEZOELECTRIC SOURCES FOR BOREHOLES

Case History

The SWEPT IMPACT SEISMIC TECHNIQUE (SIST) consists of producing seismic signals as a series of pulses according to a deterministic time coding scheme. SIST is significantly more time-efficient than on-line stacking. The low power of the individual pulses maintains a relatively high signal frequency content, even in soft materials.  


      (a)             (b)

The PH borehole piezoelectric sources are designed for investigation depths up to 1km. The seismic signals are produced by applying controlled sequences of high voltage pulses to a stack of piezoelectric crystals. The standard frequency band is 500-2500 Hz. Versions with a band of 1000-5000 Hz are also available.

The tools consist of three modules connected by steel-armored cable: the power supply&controller (out-of-the-hole), the high voltage generator (out-of-the-hole or down-hole) and the piezoelectric actuator (down-hole) equipped with an acoustic impedance converter (a) or a motor-driven sliding wedge clamping mechanism (b). The sources are designed for minimum borehole diameters of 46 mm (PH-44), 56 mm (PH-52) and 76 mm (PH-70).

Specifications
Frequency Range: 500-3000 Hz
Working Voltages: from surface: 220 V / 50 Hz to piezocrystals: up to 6 KV
Maximum Working Depth: 1000 m
Maximum Temperature: 75° C
Minimum Hole Diameter: 56 mm
Dimensions: piezoelectric converter length: 310 mm
signal generator module length: 2100 mm
diameter: 52 - 54 mm
Mass: 23 - 25 kg (without cable)