Page 24 - Primer on Enhanced Oil Recovery

Hydrocarbon and oil reserves classification 15

Reservoir any natural volume of accumulated oil and/or gas in a trap. Gas,
oil and water in the deposits are separated to the great extend under the influence of
gravitational forces. Usually gas and oil occupy the upper part of the trap, and water
fills the rest of the reservoir. In general, the conditions of the occurrence of oil and
gas in the deposits are determined by the hypersometric position of the oil-water
(OVC), gas-water (GVK) and gas-oil (GNK) contacts.
Any open or potential reservoir of oil or gas can be the subject of several sepa-
rate and independent projects at different stages of exploration and/or development.
Thus, the same reservoir may have recoverable quantities of hydrocarbons belong-
ing simultaneously to several classes of reserves or resources development projects.
The type and quantities of initial geological reserves and hydrocarbon resources are
determined from a database based on geological, geophysical and field information.
For example, the database will contain: reservoir height, oil, gas, water-oil, gas-oil
and gas-bearing zones location, oil-and-gas-saturated thickness and residual oil and
gas; reservoir rocks properties and their variations (both laterally and vertically);
the initial formation pressure and temperature. Also, the influence of all above con-
stituencies on the final oil and gas yield.
Project a link between the oil or gas deposit and the decision-making process
regarding its development. The implementation of a specific reservoir development
project is characterized by a unique hydrocarbon production profile. The profile is
unique for only this project and takes into account the time of development and finance
dynamics. The project is the main element of this classification, and the net recoverable
reserves and resources are additional quantities of hydrocarbons produced during the
implementation of each project. Profiles of hydrocarbon production are calculated
before the technical, economic or contractual development period. Production profiles
define the value of the countable recoverable reserves and resources, and the money
flows related to the project. The ratio of NCDs (initial recoverable reserves) to Total
initial geological reserves and resources determines the amount of final oil and gas out-
put for a single development project. The implementation of one project may involve
the development of several deposits or several projects. All of which can be implemen-
ted on one deposit. Not all technically feasible development projects will be industrial.
The industrial profitability of a development project depends on the set of conditions
forecasted for the project implementation period. These conditions are determined by
technological, economic, legal, environmental, social and political factors. Although
economic factors can be condensed to projected costs and prices for the outputs, they
are also, in the best, influenced by the market conditions, the development of transport
and processing infrastructure, taxation conditions and taxes themselves.
Property legal ownership. Each item, including fields, deposits and infra-
structure items, can have a distinctive legal status, which is set by incorporated
rights and obligations, including tax conditions. Specific contractual rights and obli-
gations, including financial conditions, allow to define the share of each project par-
ticipant in the total production (substantiation of ownership), as well as the share of
investments, costs and revenues for each development project and deposits. A sin-
gle property may include several deposits/it is also possible that one deposit may be
divided into several properties. The property can be both open and unopened.