Page 478 - Fundamentals of Enhanced Oil and Gas Recovery

466 Afshin Tatar

O Breaking of the O O
ester bond
R 1 C R 1 C R 1 C
–
O O OH
R 2
Glass
Possible enzyme effect

Water

Oil More electrostatic repulsion due to
breaking of ester bonds

Shift to water-wet
behavior

Figure 10.9 Breaking down of ester bonds by enzymes and altering the wetting behavior of the
solid [60].

or as binding elements within high-molecular compounds [959]. Several authors have
reported application of enzymes in removing formation damages resulted from drilling
operations [960 964]. Nasiri [60] specified that effect of enzymes on the oil water
properties is trivial compared to the effect on the oil water solid properties.
The enzyme functionality is limited by temperature [24]. Water salinity and pH
are the other parameters that influence the enzymatic activity and change the mem-
brane thickness as well as cellular thickness [833]. However, some types of enzymes
can resist the extreme condition of pH, salinity, and pressure [965].

10.15 GENETICALLY-ENGINEERED MICROBIAL ENHANCED OIL
RECOVERY

The conventional MEOR methods incorporate the available native microorgan-
isms with a limited number of applicable trait combinations. Each bacteria type owns
their particular traits, which are associated with certain limitations [4]. As an example,
a certain bacteria type, which adequately generates the desired bioacids, may not sur-
vive in the reservoir harsh pH condition. These limitations and constraints encouraged
a new biotechnology in petroleum industry referred to as Genetically-Engineered