Page 451 - Fundamentals of Enhanced Oil and Gas Recovery

Microbial Enhanced Oil Recovery: Microbiology and Fundamentals 439

Table 10.6 Production Problems and Suitable MEOR Processes Modified After Bryant and Rhonda
[392] and Volk and Hendry [22]
Production Problems MEOR Process Helpful Microorganisms

Formation damage, low Well stimulation Generally surfactant, gas, acid, and alcohol
oil relative producers
permeability
Trapped oil due to Waterflooding Generally surfactant, gas, acid, and alcohol
capillary forces producers
Poor seep efficiency, Permeability Microorganisms that produce polymer and/or
channeling modification copious amounts of biomass
Paraffin problems, Wellbore cleanup Microorganisms that produce emulsifiers,
scaling surfactants, and acids. Microorganisms that
degrade hydrocarbons
Unfavorable mobility Polymer flooding Microorganisms that produce polymer
ratio low sweep
efficiency
Water or gas coning Mitigation of Microorganisms that produce polymer and/or
coning and/or copious amounts of biomass
copious

best MEOR solution. Table 10.6 shows the common production problems and their
probable solution using MEOR applications. After clear determination of the problem
constraining the oil production, the best MEOR practice can be formulated. For this,
Volk and Hendry proposed [22] it is necessary to quantify parameters including the
microbial growth rate, mass of the target product per unit mass substrate consumed
and added, and concentration and fate of the bioproducts.

10.12.2 Considering Microbiological Principles
The other important step to have a beneficial MEOR project is to gain a thorough
knowledge about the existing microbial biological community in the target reservoir.
It is essential to now about the diversity of the microbial life and biochemical cycles.
As it was mentioned before, it is unlikely that the pristine microbial diversity is pre-
served after production rate declines. Thus, understanding the status of microbial con-
sortia before commencement of MEOR treatment is much more important than the
status of the pristine microbial biology before the time production started [22].To
exploit the microbial activities for enhancing oil recovery, at least it should be clear
that which microorganisms are present in the reservoir and what are the parameters
affecting their growth and activity [17]. For employing in situ approaches, it is essen-
tial to ascertain that a diversity of microbial life capable for metabolisms even in
extremely hypersaline and thermophilic oil reservoirs exists [17,125,804,805].Itis
likely that the microorganisms already present in the reservoir take the desired actions.