After identifying sedimentary basins thought to contain hydrocarbons, an oil company acquires the mineral rights from the individual or government holding them. The oil company will then contract with a seismic acquisition company, such as Western GECO to map the area's underground rock formations through seismic surveying.
Seismic surveys use low frequency acoustical energy generated by explosives or mechanical means.
These waves travel downward, and as they cross the boundaries between rock layers, energy is reflected back to the surface and detected by sensors called geophones. The resulting data, combined with assumptions about the velocity of the waves through the rocks and the density of the rocks, are interpreted to generate maps of the formations. Seismic surveys are usually performed using multiple geophones set at known distances from the energy source. Early seismic surveys used mechanical plotters to record the received signals, and were restricted to a few geophones. These surveys placed the source and geophones in a straight line, with the interpretation of the resulting data producing a 2-D cross section of the formation under that line.