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Injection of a working fluid into the reservoir not only
intensifies production and ensures the maximum oil recovery
factor but also increases reservoir pressure and the bottom-hole
pressure in the producing wells, prolonging thus the following life
of the reservoir.
The oil recovery factor depends on shape and size of the
reservoir, and also on a number of other factors. Other things being
equal, the output of a reservoir depends on the length of the rows
of producing wells, i.e., on the length of the oil drainage boundary,
and the productive life depends on the reserves, which are
approximately proportional to the area and thickness of the
deposit. Thus, oil recovery factor is determined on a considerable
extent of length of drainage boundary to area of deposit. This ratio
may be such that the productive life of the reservoir is unduly
prolonged in view of the conversation of the central part of the
reservoir. The productive life can be shortened by more intensive
exploitation and to achieve this, edge flooding can be
supplemented by pattern flooding. The reservoir is divided up into
a number of separate fields with using of rows of injection wells,
thereby considerably lengthening the drainage boundary and,
therefore, also the outer rows of producing wells. Rows of
producing wells must be provided on either side of the row of
injection wells used in pattern flooding. The recommended
procedure is to have not more than 5-7 producing rows between
the rows of injection wells. In this way the entire reservoir can be
brought into production, the current rate of oil production
increases and productive life becomes shorter.
Conditions that favour for the application of pattern
flooding present of water underlying the lowermost sections of the
formation and continuity of the formation which helps to
accelerate effect of injection wells.
The productive life of steep formations can be reduced by
injecting gas (or air) near crest of reservoir to create an artificial

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