1. Logging in general

1.1 Definition

Logging is a geophysical technique used inside a borehole. The radius of the investigation volume is not much larger than that of the borehole.

They are used to measure in situ a physical parameter characteristic of the terrain, with the best possible vertical resolution. They do not (unlike geophysical drilling techniques) increase the radius of investigation of the borehole, nor do they allow us to judge the representativeness of the information obtained from the borehole.

They are complementary to surface geophysical techniques, which provide information representative of large volumes of terrain, but with less fine resolution (we know the terrain "roughly", but can't see the details).

The result...