Proved Reserves (1P and 2P)

The oil and gas a producer can recover with reasonable certainty at current prices and costs (1P), split into proved developed reserves, recoverable from wells already drilled, and proved undeveloped reserves, which need wells still to be paid for. Adding probable reserves, more likely than not to be recovered, gives 2P. Reserves fall with production and are replaced by drilling, extensions, discoveries and revisions, so the roll-forward from one year to the next shows whether a producer is growing or depleting.