core — Oil & Gas Glossary
A cylindrical sample of geologicformation, usually reservoirrock, taken during or after drilling a well. Cores can be full-diameter cores (that is, they are nearly as large in diameter as the drill bit) taken at the time of drilling the zone, or sidewall cores (generally less than 1 in. [2.5 cm] in diameter) taken after a hole has been drilled. Cores
Detailed Explanation
samples are used for many studies, some of which relate to drilling fluids and damage done by them.