Definitions for "Probable Reserves"
Reserves with a higher degree of risk associated with its ultimate realization
Probable reserves are less certain than proved reserves and can be estimated with a degree of certainty sufficient to indicate they are more likely to be recovered than not. Note that probable reserves have not been risked.
Areas which are unproven but presumed capable of production because of geological inference, for instance, proximity to proven reserves in the same reservoir.
Keywords:  casing, production
Production casing