RESERVES

DEFINITIONS OF RESERVESby SPE and WPCReserves are those quantities of petroleum which are anticipated to be commercially recovered from known accumulations from a given date forwardReserve ClassificationsProvedProbablePossibleDevelopedUndevelopedUnproved

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.Proven 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.Unproved 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:Probable 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:Possible Reserves

Reserves estimation uncertaintyDeterministic a single best estimate of reserves is made based on known geological, engineering, and economic data.Probabilistic the known geological, engineering, and economic data are used to generate a range of estimates and their associated probabilities

Proven reserves 90% probabilityProbable reserves the difference between 50 and 90% probabilityPossible reserves the difference between 10 and 50% probabilityFrom distribution curves:Probabilistic Representation of Recoverable Reserves

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?

Reserves are those quantities of petroleum which are anticipated to be recovered from a petroleum accumulation. What wrong with this definition?

We have a structure in our licence area which we intend to explore. We anticipated it to contain a STOIPP of 2000 MMstb, and recovery factor of 65% using primary methods (30%), secondary (25%) and tertiary (10%) recovery methods. What are the reserves?

A reservoir has been discovered by drilling a successful exploration well, and drilling a number of producing wells. We have even produced some 200 MMstb of oil. STOIIP is 2000 MMstb and recovery factor is 35%. What are the reserves?Test yourself

Remaining hydrocarbon in place

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Remaining reserves!

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