1. n. [Formation Evaluation]

A core that has been preserved in the same state as when it was brought to the surface. The term implies that the core has been stored for a period before analysis. If this has not been the case, it is known as fresh core. The goal of preservation is to maintain the original fluid content, fluid distribution, rock wettability and mechanical integrity. Preserved cores are typically sealed and protected from mechanical damage. Depending on the core and the objective, they may also be frozen or placed in humidity ovens. Preservation may be wet, in which the core is submerged in a suitably prepared brine, or dry, without any fluid.

See: native-state core,  restored state core,  routine core analysis