Page 20 - Primer on Enhanced Oil Recovery

Hydrocarbon and oil reserves classification 11

In the following the main classes and categories of geological hydrocarbon
reserve volumes are listed.
The total initial geological resources and reserves are the initial volumes of
hydrocarbons found in natural deposits before the start of their development, as
well as the volumes of hydrocarbons in deposits that are expected to discovered
(forecasting) in the future, the equivalent of “total resources”.
Open initial geological resources and reserves are calculated hydrocarbon
volumes contained in the already known (explored) deposits prior to the beginning
of commercial exploration of hydrocarbons.
Production accumulated volumes of liquid, gaseous and solid hydrocarbons,
produced on a specific date, e.g. already extracted hydrocarbons.
Reserves are the amount of oil, combustible gases, natural condensate
and associated components contained in them, which is located in the depos-
its studied by drilling and which are supposed to be mined from a specified
date under existing economic conditions. All estimates of reserves take into
account a certain degree of risk or uncertainty, which depends on the number
of geological, geophysical and field data, technical and economic, available.
All factors should be accounted for at the time of calculating reserves. This
will include all necessary financial data: cost of area exploration, the cost of
drilling, transportation costs, set prices per barrel, taxes, and much more.
All this plays a role in determining the feasibility of a project to develop
reserves.
Conditional resources are volumes of potentially recoverable hydrocarbons,
calculated from the assessment (as of a specific date) of explored deposits, but with
delayed production. The delay is due to existing extraction constraints. Conditional
resources are classified according to the level of confidence determined during the
modeling. Modeling also takes into account the phases of the project and it eco-
nomic indicators. If restrictive conditions can change in the future and conditional
resources can be profitably developed, then these hydrocarbon volumes should be
transferred to the other appropriate categories.
For example, conditional resources may include projects for which, at present,
for examples: there are no profitable markets, hydrocarbon production depends on
the emergence of new technologies, or on which the calculation of reserves
(resources) of a deposit does not allow an unequivocal conclusion about the indus-
trial significance of a development project.
Undiscovered initial oil-in-place the amount of liquid, gaseous and solid
hydrocarbons contained in deposits that are not yet discovered (but forecasted as
possible) on the date of calculation.
Perspective resources are the volumes of potentially recoverable hydrocar-
bons which are calculated when assessing (on a specific date) exploration. These
are prospective structures, i.e. undiscovered deposits for the future implementation
of future development projects.
For example, prospective resources may be in the deep-lying horizons of the
developed fields but not discovered at the date of the estimate. Nevertheless, there
might be favorable geological conditions for the accumulation of hydrocarbons.