Unproved reserves

Unproved reserves are based on geological and/or engineering data similar to that used in estimates of proved reserves, but technical, contractual, or regulatory uncertainties preclude such reserves being classified as proved. [11] Unproved reserves may be used internally by oil companies and government agencies for future planning purposes, but are not routinely compiled. They are sub classified as probable and possible [11]
Probable reserves are are attributed to known accumulations, and claim a 50% confidence level of recovery. Industry specialists refer to this as P50 (i.e. having a 50% certainty of being produced). Referred to in the industry as 2P (proved plus probable).[8]
Possible reserves are attributed to known accumulations which have a less likely chance of being recovered than probable reserves. This term is often used for reserves which are claimed to have at least a 10% certainty of being produced (P10). Reasons for classifying reserves as possible include varying interpretations of geology, reserves not producible at commercial rates, uncertainty due to reserve infill (seepage from adjacent areas), projected reserves based on future recovery methods. Referred to in the industry as 3P (proved plus probable plus possible).