1. n. [Formation Evaluation]

A core that is in the same state as when it was brought to the surface. A fresh core is sealed as soon as possible after retrieval from the well to minimize the loss of fluids and exposure to air. The term implies that the core is analyzed before being stored, after storage it is known as preserved core. Since the purpose is to minimize alteration, a fresh core has often been drilled with a bland mud, either water- or oil-base, but with a minimum of chemical additives and weighting material.

See: bland coring fluid,  native-state core,  oil-base mud,  preserved core,  restored state core,  routine core analysis,  water-based drilling fluid