Land Seismic Exploration Technique
"The Reflection Seismic Method"
The “Reflection Seismic Method” is a geophysical technique used to map in 2D or 3D, an image of the earth’s subsurface. Reflection Seismic is used by Oil & Gas, Coal Seam Gas, Minerals and Coal Exploration and Production companies to develop a clear understanding of subsurface rock structure and other geologic properties.
“Seismic Vibrators” are used in onshore Oil Exploration to generate a compressional wave travelling downward through the subsurface and being partially reflected at each rock interface. The reflected energy is recorded at the surface by the Seismic Recording System via a 2 to 10 km long Seismic Cable to which ground motion sensors called Geophones are attached.
The Geophones are moved by the upward travelling compressional wave, generating a small electrical current within the geophone. The small electrical signals are added to improve Signal to Noise Ratio and are digitized to 24 bit accuracy with the digital signal then being transmitted to the Recording Truck connected to the Seismic Cable.
“Seismic Sweep” - The Servo-Hydraulic Seismic Vibrator uses a hydraulic pump and servo valve operating at 3000 psi to accelerate a 4000 kg Steel Mass (attached to the baseplate) through a pre-programmed range of frequencies between 4 and 200 Hz.
The “Sweep” can be generated with variable force, phase rotation and timing. To increase the Energy output (amount of Force) being transmitted into the earth, several Vibrators may be used in series and several sweeps with the same or variable frequency ranges may be added together.
Terrex Seismic operates four (4) Seismic Vibrators on each of its four (4) Seismic Crews acquiring 2D and 3D seismic surveys using a the Sercel 428XL Seismic Recording System with Sensor SM24 10Hz Geophones.