It would be extremely limited to none, in terms of environmental impact.
There are programs called aeromagnetics that look at fluctuations in the magnetic field. People who specialize in that area can interpret distortions of a magnetic field as an indicator of oil and gas reserves. An aeromagnetic program is run by flying. You fly with the receivers, the equipment for detecting that shift in magnetic field, in an airplane.
If you look at geochemical-type studies, they're typically right at the surface, and they're looking for anomalies. In some areas of the world, you actually have natural seeps where oil and gas actually seep to the surface. You can dig a little hole and look at the sand and you can tell if there's any naturally occurring hydrocarbons, which would give you an indication of something underground.
We're not talking real industrial activities with those types of programs.