Oil drilling?

could anyone please explain what logging operations means when drilling for oil.thanksOil drilling?
Logging is the observing and recoding of characteristics of the rock chips that are forced up out of the hole as it is drilled. The rock type is identified, particulars of its characteristics are written down. When rock types change the contact is noted.


After the hole is drilled often special tools are lowered down the hole and some characteristics are recorded. Conductivity is a common and useful chararteristic to plot. Magnetism is often recorded, other traits can also be noted and graphed automatically. COmbined these records are useful for tlling the potential of oil production for that hole and usually even more useful for telling the likelyhood of prospects in the ';neighborhood.';