Seismic is one of the most important tools a practicing petroleum geologist could ever use. This method determines depth, stratigraphy, and the structure of rock formations deep within the Earth.
The concept behind the 2D seismic survey is that subsurface structures are interpreted by the measurement of the transit time of sound waves that are produced by an explosion or a vibration.
Onshore Seismograph Field Operation
Seismic data is gathered by the creation of vibrations at the surface by either dynamite explosions or a vibrator truck (also known as a thumper truck). Sound waves are created by these disturbances and they travel deep into the subsurface. They are then reflected back by the different rock layers and recorded by a seismograph. Spread out over the area of interest are listening devices referred to as geophones. They are attached to recording instruments in a seismograph truck by electric cables. Charges are set off in shot holes when dynamite is used. The geophones capture the reflections from the sound waves. Then, the data is uploaded into computers for processing. Afterward, a seismic line is created for interpretation by a geophysicist.
This is the same process used for offshore exploration, the with exception that instead of using trucks, they use boats.
Offshore Seismograph Field Operation
A more sophisticated way of retrieving seismic data was introduced in the 1990s and it has become very popular. It is referred to as 3D Seismic. It collects data in a similar fashion as the 2D, but the shot points are much closer together and the shoot is laid out on a grid. A huge amount of data is recovered and is then processed by computers. The end result is a 3D data set that provides remarkable and accurate data maps.
3-D Amplitude Map
Even with technological advances in seismic within the past several years, the drill bit is the only reliable way to find oil and gas.