Reserves: quantities of crude oil and gas (both discovered and undiscovered) anticipated to be economically recoverable from discovered / proved sources. Oil in the ground is not a reserve unless is it estimated to be economically recoverable. Simple formula: (Discovered oil) — (Produced oil). Discovered Reserves / Proved Reserves: reserves that can be estimated with a high degree of certainty to be recoverable using current technology at current prices. Reserves do not include oil that has been produced / extracted. Undiscovered Reserves / Yet-to-find Reserves: quantities of crude oil estimated on a given date to be potentially recoverable from discovered accumulations, but which are not currently economic to extract. Discovered & Undiscovered Unrecoverable Resources: unrecoverable resources, whether discovered or not, are neither technically possible nor economic to produce.
Prospective Resources: quantities of oil and gas estimated on a given date to be potentially recoverable from undiscovered accumulations.