# Oil and Gas Reserves

**Source:** Buckhead Energy Oil & Gas Encyclopedia (https://www.buckheadenergy.com/learn) — canonical: https://www.buckheadenergy.com/oil-and-gas-reserves

Oil and gas reserves are the quantities of oil and gas that are expected to be economically recovered from known accumulations under current conditions, sorted by how certain that recovery is — proved (1P), proved-plus-probable (2P), and proved-plus-probable-plus-possible (3P) — with the certainty of the category driving how heavily the reserves count toward value.

## What "reserves" actually means
Reserves are not "all the oil in the ground." They are the portion expected to be economically recovered from known deposits under existing prices, technology, and regulation. Oil that is physically there but cannot be produced at a profit is not a reserve — which is why reserves rise and fall with prices and technology even when the rock never changes.
Because recovery is a forecast, reserves are always described with a level of certainty. That is the whole point of the reserve categories: they sort expected barrels by how sure we are of getting them.

## Proved, probable, possible (1P/2P/3P)
Proved (1P): reserves reasonably certain to be recovered — high confidence. This is the category that includes proved developed producing and other proved sub-categories.
Probable: reserves more likely than not to be recovered but less certain than proved. Proved + probable is called 2P.
Possible: reserves that might be recovered but are less likely than probable. Proved + probable + possible is 3P.
Certainty falls from proved to probable to possible, and value is weighted accordingly.

## How reserves are estimated
Engineers estimate reserves using decline curve analysis on producing wells, analogy to nearby wells, and reservoir modeling, then apply prices and costs to decide how much is economic. The result is periodically re-estimated as wells produce, prices move, and new wells are drilled — so reserves are a living estimate, not a fixed fact.
This is why a reserve figure always comes with an "as of" date and a set of price and cost assumptions. Change the assumptions and the reserves change.

## Why reserves matter to owners
For a mineral owner, reserves are the underlying quantity your future royalties are paid from. The value of an interest tracks the proved reserves most closely — especially proved developed producing — while probable and possible reserves add upside at a steeper risk discount. When a buyer values your minerals, it is essentially estimating your share of the recoverable reserves and discounting for time, price, and risk.
Understanding the categories helps you read an offer: certain (proved, producing) barrels are worth more per unit than speculative (possible, undrilled) ones. Buckhead Energy weights proved producing reserves as the reliable core of value. This page is educational information, not financial advice.

## Frequently asked questions

**What are oil and gas reserves?**
The quantities of oil and gas expected to be economically recovered from known accumulations under current prices, technology, and regulation. Oil that cannot be produced at a profit is not a reserve, which is why reserves change with prices and technology even when the rock does not.

**What is the difference between proved, probable, and possible reserves?**
Proved (1P) reserves are reasonably certain to be recovered; probable reserves are more likely than not (proved + probable = 2P); possible reserves might be recovered but are less likely (proved + probable + possible = 3P). Certainty and value fall from proved to probable to possible.

**What does 1P, 2P, and 3P mean?**
1P is proved reserves. 2P is proved plus probable. 3P is proved plus probable plus possible. The higher the number, the more speculative reserves are included, so 1P is the most certain figure and 3P the most optimistic.

**How are oil and gas reserves estimated?**
Using decline curve analysis on producing wells, analogy to nearby wells, and reservoir modeling, then applying prices and costs to determine how much is economic. Reserves are re-estimated over time as wells produce and prices move, so they come with an "as of" date and assumptions.

**How do reserves affect what my minerals are worth?**
Reserves are the quantity your future royalties are paid from. Value tracks proved reserves most closely — especially proved developed producing — while probable and possible reserves add upside at a steeper discount. A valuation is essentially your share of recoverable reserves, discounted for time, price, and risk.

## Related terms
- [Proved Developed Producing (PDP)](https://www.buckheadenergy.com/proved-developed-producing)
- [Decline Curve](https://www.buckheadenergy.com/decline-curve)
- [Oil and Gas Production](https://www.buckheadenergy.com/oil-and-gas-production)
- [How We Value Mineral Rights](https://www.buckheadenergy.com/how-we-value)
- [Oil & Gas Encyclopedia — all terms](https://www.buckheadenergy.com/learn)

_Educational information only, not legal or tax advice. Buckhead Energy is a direct buyer of oil & gas mineral and royalty interests._