Reserve
Reserve
Reserve
DEFINITIONS OF RESERVES
by SPE and WPC
Reserves are those quantities of petroleum which
are anticipated to be commercially recovered from
known accumulations from a given date forward
Reserve Classifications
Proved
Developed
Undeveloped
Unproved
Probable
Possible
Proven Reserves
Proven reserves are those of petroleum which, by
analysis of geological and engineering data, can be
estimated with reasonable certainty to be commercially
recoverable, from a given date forward, from known
reservoirs and under current economic conditions,
operation methods, and government regulations.
90% probability of the quantities actually recovered will
equal or exceed the estimate.
Developed or undeveloped proven reserves.
Unproved Reserves
Unproved reserves are based on geologic and/or
engineering data similar to that used in estimates of
proved reserves; but technical, contractual, economic, or
regulatory uncertainties prelude such reserves being
classified as proved.
Probable Reserves
Probable reserves are those unproved reserves which
analysis of geological and engineering data suggests
are more likely than no to be recoverable.
50% probability of recovered proved plus probable
reserves.
Probable reserves include:
Possible Reserves
Possible reserves are those unproved reserves which
analysis of geological and engineering data suggests
are less likely to be recoverable than probable
reserves.
10% probability of recovered proved plus probable
plus possible reserves.
Possible reserves include:
Probabilistic Representation of
Recoverable Reserves
Test yourself
There are 950 MMstb of oil initially in place in a reservoir. It is estimated that
500 MMstb can be produced. Already 100 MMstb have been produced. What
are the STOIIP and reserves?
Before starting production it was estimated that there was a 90% chance of
producing at least 100 MMstb, 50% chance of producing 500 MMstb and 10%
chance of producing 700 MMstb. What are the proved reserves, probable
reserved, and possible reserves?