3D seismic surveys reveal far more information than the 2D technology, which was used in the pioneering days of Cooper Basin discovery. Comparing 3D to 2D seismic results is like comparing an ultrasound or MRI tomographic body scan with a single X-ray.
Seismic energy is generated by large hydraulically operated pads mounted beneath four-wheel-drive trucks. The computer controlled pads each provide approximately 60,000 pounds of peak force. The trucks move along a straight-line traverse and at each recording point (40 m intervals) the pads are lowered to the ground and vibrated through a range of frequencies from 5-90 Hz over a 3-4 second period. This is a very passive energy source which emulates the same signal type as the now largely obsolete dynamite energy source. This site’s Gallery contains photographs of the vibroseis trucks used in the Spinel 3D seismic survey.
The very small seismic or sound waves travel down through the rocks, with minute amounts of the energy being reflected back to the surface from each deeper geological layer. By using very sensitive listening devices, geophones, the reflected seismic energy can be recorded from depths of up to 3 or 4 km.
By repeating this process along traverses 320m apart, a very detailed sub-surface image can be constructed from the data that is collected. The amount of data enables geophysicists to create psuedo-3D images of the volumes of sub-surface rocks, rather than individual 2-dimensional cross sections that are the output of 2D surveys.
Approximately 12-15 personnel operate from a survey and line-clearing camp, which moves ahead of the main recording camp. The main recording camp of some 50 personnel provides logistical support for acquisition of the seismic data.