Page 426 - Fundamentals of Enhanced Oil and Gas Recovery

414 Afshin Tatar

(Single 5-spot pattern shown)
Microorganisms
and nutrients
Injection Production well
pump
Produced oil
and products
Injection
well

Microbial
Driving Microor- products Oil and Preflush
fluid Nutrients ganisms for products to condition
(water) releasing reservoir
oil

Figure 10.4 Schematic representation of microbial flooding. Courtesy of the National Energy
Technology Laboratory and the U.S. Department of Energy.

10.8 MEOR APPLYING APPROACHES IN FIELD
10.8.1 Microbial Flooding

This method employs the effects of microbial metabolites for enhancing the oil recov-
ery. In this approach, by adding the nutrients to the water flood the indigenous
microorganisms are stimulated to produce desired bioproducts for mobilizing the
residual oil or modifying the flow paths of the waterflood (see Fig. 10.4). In cases in
which the target microorganisms are not present, they will be coinjected along with
the nutrients via the injection wells. The mobilized oil will be produced in the pro-
ducing wells. Several studies denotes the effectivity of this approach
[11,76,108,408 410] and being economically feasible [108,409].

10.8.2 Cyclic Microbial Recovery
For cyclic microbial recovery, the solution containing the nutrients such as
fermentable carbohydrates like molasses (and microorganisms in cases the indigenous
microorganisms are not present) is injected down a well, which is close to its eco-
nomic limit. Depending on the permeability and depth of the reservoir, injection
time is different. After that, the well will be shut in for days or weeks before fluid is
allowed to flow, which is referred to as the incubation period. Meanwhile, the micro-
organisms will produce the desired metabolites to facilitate the oil movement in the