<P> The extraction of petroleum is the process by which usable petroleum is drawn out from beneath the earth's surface location </P> <P> Geologists and geophysicists use seismic surveys to search for geological structures that may form oil reservoirs . The "classic" method includes making an underground explosion nearby and observing the seismic response, which provides information about the geological structures underground . However, "passive" methods that extract information from naturally occurring seismic waves are also used . </P>

How to get crude oil from the ground