Reserves and Recovery Factor
In place volume is geology, reserves are engineering and economics: the recovery factor connects them and carries most of the argument.
The equation
Reserves = STOIIP × RF
- RF is the fraction of in place oil that will actually be produced
- Typical waterflood recovery sits between 0.25 and 0.45
- Gas fields commonly recover 0.6 to 0.85
Worked example
A 50 million barrel STOIIP developed with water injection at a recovery factor of 0.35 yields 17.5 million barrels of reserves. Improving RF by five points adds 2.5 million barrels without drilling a single exploration well.
When to use it
Recovery factor moves with drive mechanism, well count, and oil viscosity. Analogue fields anchor the estimate early, simulation refines it later, and small RF changes swing project economics more than most people expect.
Related Calculators and Reference
- Mud Weight and Pressure Gradient Calculator: convert between ppg, SG, and psi per foot.
- Probabilistic STOIIP Calculator: volumes with uncertainty ranges.
- PetroWiki by SPE: the industry reference for petroleum engineering.