To produce hydrocarbons the reservoir must be found and be capable of producing fluids. The interconnections of the porous spaces, the permeability, permits flow of the gases and liquids. Tightly connected porous spaces are difficult producers, but well connected spaces have good permeability and are productive. The oil exploration process finds possible drilling locations, and the actual drilling of a well is used to test the geological hypothesis of hydrocarbon existence.
We shall study the seismic method for determining the subsurface structure. The geophysical technique is to generate artificial seismic waves and record their reflections from impedance differences within the earth. Echoes come from the reflections created by relatively hard surfaces where the impedance changes.