Page 305 - Fundamentals of Enhanced Oil and Gas Recovery

Microbial Enhanced Oil Recovery: Microbiology and Fundamentals 293

Figure 10.1 The incremental oil costs for different EOR methods [26].

other tertiary methods used petroleum-based chemicals [6,15]. In MEOR, several
mechanisms works at the same time and this highly improves the effectiveness of this
method [30]. This method is relatively environmental friendly [30]. The biochemicals
generated by the microbes are largely biodegradable and nontoxic [24,31].
However, there are some challenges regarding employing MEOR.
Unfortunately, considering the other tertiary techniques, MEOR is confined to lab-
oratory investigations and the field trials are scattered and also small-scale [32].
Although there are many successful reported field trials in literature, in some cases
there is still a place of skepticism about the validity of the results [32].Moreover,the
major uncertainty is about the process reliability and reproducibility [32].Amongst
the several reported successful MEOR field applications, still there are some cases
reporting MEOR to be ineffective. Extreme caution should be considered in chang-
ing the microenvironment of the reservoir by introducing new compounds [31].
Accidental or uncontrolled development of some bacteria populations such as
sulfate-reducing bacteria (SRB) can induce extra costs, damage the facilities, and
bringsome safetyhazardous [15,16,33 36]. The injected oxygen for aerobic
MEOR trials is a corrosive agent and can damage the facilities and downhole pip-
ing. Anaerobic MEOR needs a relatively huge amount of sugar as the nutrient,
which makes the application of MEOR limited in offshore platforms due to logisti-
cal issues [24]. For cases dealing with cultivation of bacteria and producing the bio-
chemicals on surface, the high costs of laboratory equipment, maintenance of the