Page 34 - Primer on Enhanced Oil Recovery

Hydrocarbon and oil reserves classification 25

Figure 2.8 Gas cap and solution gas drive scenarios.

The natural reservoir regime has one of the most important influences on the
choice of rational, most economical, reservoir development systems and the effi-
ciency of utilization of reservoir energy in order to achieve the maximum ratio of
oil (carbohydrate) recovery.
At present, the justification of RF is conducted, as a rule, on geological and
hydrodynamic models, taking into the account geological, technical, technological
and even economic risks. The geological part of the model includes a three-
dimensional geological representation of the deposit in the form of a digital model.
The hydrodynamic part includes complete information on the operation of produc-
tion and injection wells (perforation intervals, commissioning, work history in time,
etc.).
Reliability of geological and hydrodynamic modeling is also achieved by their
adaptation to the past actual period of development of the reservoir (History
match). By simulating filtration processes in the three-dimensional space of res-
ervoir rocks and displacing oil (working agent) to the bottom of production wells,
a special model of the development project is created using computer programs
to predict the change in the state of the reservoir behavior at any time. The result
is a calculation of the design indicators of the development, both by the years of
operation, and for individual periods (10, 20, 40 years) of time, or until the end
of development.
The value of the final oil recovery coefficient RF is determined for several var-
iants of the design of the development system, which represents the overall optimi-
zation task of choosing the best design variant that ensures the maximum oil
recovery ratio.
Two different approaches can be taken as the basis for optimization: the achieve-
ment of the technically possible maximum oil recovery coefficient, i.e. getting the
highest RF, or getting the most profit from the development project implementation
process. The priority of assessing the oil recovery ratio, taking into account the eco-
nomics of a development project, requires that the current oil market, tax legisla-
tion, etc. be taken into account in the calculations of the current market situation
and, ultimately, profit margin.