Page 297 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

264 Reservoir Engineering

common: (1) peripheral or central flooding where the injectors are grouped
together, and (2) pattern flooding where certain patterns are repeated through-
out the field. The relative location of injectors and producers depends on the
geology and type of reservoir, the volume of reservoir swept, and the time
limitations that affect economics. When possible, the injection scheme should
take advantage of gravity, i.e., dipping or inclined reservoirs, gas caps, or
underlying aquifers.

Peripheral or Central Flooding
In peripheral flooding, the injectors are located around the periphery so that
the flood progresses toward the center as shown in Figure 5-149, When the first
row of producers flood out, they are converted to injection status. This type of
flood can result in maximum oil recovery with a minimum of produced injectant,
and less injectant is required for a given mount of production, but a peripheral
flood usually takes longer than a pattern flood. In general, adequate per-
meability is required to permit movement of fluids at an acceptable rate with
the available well spacing. Central flooding is the opposite case in which
injectors are located in the center of the field, and the flood progresses outward
(see Figure 5149).

Pw

pw central Flooding
t
IW n
I Oil I.w

Peripheral Flood

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Combination Central and Peripheral flood
Okoducinp Well AWObr Injection Well .Gas Injection Well
Flgure 5-149. Peripheral and central flooding.