The entire quantity of reserves that a firm predicts having access to, computed as the sum of all proved and untested reserves, is known as 3P oil reserves. Proven, probable, and potential reserves are the three Ps.
The oil industry divides untested reserves into two categories: those that are likely to be exploited owing to financial or technical problems (probable) and those that are less likely to be extracted due to geological and engineering estimations from established sources (unproven) (possible). As a result, 3P stands for proven, probable, and potential reserves. This is in contrast to 2P oil, which only contains known and probable reserves.