Proved Reserves
Proved Reserves are those quantities of petroleum, which by analysis of geoscience and engineering data,
can be estimated with reasonable certainty to be commercially recoverable, from a given date forward, from
known reservoirs and under defined economic conditions, operating methods, and government regulations
.
If deterministic methods are used, the term reasonable certainty is intended to express a high degree of
confidence that the quantities will be recovered. If probabilistic methods are used, there should be at least a
90% probability that the quantities actually recovered will equal or exceed the estimate. The area of the
reservoir considered as Proved includes:
(1)
the area delineated by drilling and defined by fluid contacts, if any, and
(2)
adjacent undrilled portions of the reservoir that can reasonably be judged as continuous with it and
commercially productive on the basis of available geoscience and engineering data.
In the absence of data on fluid contacts, Proved quantities in a reservoir are limited by the lowest known
hydrocarbon (LKH) as seen in a well penetration unless otherwise indicated by definitive geoscience,
engineering, or performance data. Such definitive information may include pressure gradient analysis and
seismic indicators. Seismic data alone may not be sufficient to define fluid contacts for Proved reserves (see
“
2001 Supplemental Guidelines,
”
Chapter 8). Reserves in undeveloped locations may be classified as Proved
provided that the locations are in undrilled areas of the reservoir that can be judged with reasonable certainty
to be commercially productive. Interpretations of available geoscience and engineering data indicate with
reasonable certainty that the objective formation is laterally continuous with drilled Proved locations. For
Proved Reserves, the recovery efficiency applied to these reservoirs should be defined based on a range of
possibilities supported by analogs and sound engineering judgment considering the characteristics of the
Proved area and the applied development program.
Probable Reserves
Probable Reserves are those additional Reserves which analysis of geoscience and engineering data indicate
are less likely to be recovered than Proved Reserves but more certain to be recovered than Possible
Reserves.
It is equally likely that actual remaining quantities recovered will be greater than or less than the sum of the
estimated Proved plus Probable Reserves (2P). In this context, when probabilistic methods are used, there
should be at least a 50% probability that the actual quantities recovered will equal or exceed the 2P estimate.
Probable Reserves may be assigned to areas of a reservoir adjacent to Proved where data control or
interpretations of available data are less certain. The interpreted reservoir continuity may not meet the
reasonable certainty criteria. Probable estimates also include incremental recoveries associated with project
recovery efficiencies beyond that assumed for Proved.
Possible Reserves
Possible Reserves are those additional reserves which analysis of geoscience and engineering data indicate
are less likely to be recoverable than Probable Reserves
The total quantities ultimately recovered from the project have a low probability to exceed the sum of Proved
plus Probable plus Possible (3P), which is equivalent to the high estimate scenario. When probabilistic
methods are used, there should be at least a 10% probability that the actual quantities recovered will equal or
exceed the 3P estimate. Possible Reserves may be assigned to areas of a reservoir adjacent to Probable
where data control and interpretations of available data are progressively less certain
.
Frequently, this may be
in areas where geoscience and engineering data are unable to clearly define the area and vertical reservoir
limits of commercial production from the reservoir by a defined project. Possible estimates also include
incremental quantities associated with project recovery efficiencies beyond that assumed for Probable.
Probable and Possible Reserves
(See above for separate criteria for Probable Reserves and Possible Reserves.)
The 2P and 3P estimates may be based on reasonable alternative technical and commercial interpretations
within the reservoir and/or subject project that are clearly documented, including comparisons to results in
successful similar projects. In conventional accumulations, Probable and/or Possible Reserves may be
assigned where geoscience and engineering data identify directly adjacent portions of a reservoir within the
same accumulation that may be separated from Proved areas by minor faulting or other geological
discontinuities and have not been penetrated by a wellbore but are interpreted to be in communication with the
known (Proved) reservoir. Probable or Possible Reserves may be assigned to areas that are structurally
