Reserves refer to the estimated quantities of hydrocarbons (oil, natural gas, and natural gas liquids) that are expected to be commercially recoverable from a specific reservoir or group of reservoirs. Reserves are typically categorized according to their level of certainty, based on the available geological and engineering data and the level of risk associated with their recovery.
There are three main categories of reserves:
Proved reserves: Reserves that have a high degree of certainty of being recoverable, based on existing geological and engineering data. These reserves are typically the most valuable and represent the majority of the commercially viable hydrocarbons.
Probable reserves: Reserves that are less certain to be recoverable than proven reserves, but still have a reasonable expectation of commercial viability based on geological and engineering data.
Possible reserves: Reserves that are less certain to be recoverable than probable reserves, but still have some potential for commercial viability based on geological and engineering data. These reserves may require additional exploration or development work to confirm their recoverability.