MEOR represents a truly eco-friendly petroleum recovery
process employing biotechnological resources and techniques
that can be used to replace and augment the traditional EOR
processes and flooding chemicals. Many countries have envisaged
that one-third of their oil recovery programs will utilize MEOR
techniques by the year 2010. Though it has been repeatedly
encountered that the benefits of MEOR projects applied to one
well have positively affected the recovery performance of
neighboring wells, thus improving the process efficiency; better
understanding of the reservoir characteristics, biochemical and
physiological characteristics of microbial consortia, controlling
mechanisms and process economics are essential before MEOR
becomes a viable process for general field applications. Most of
the MEOR work leading to field trials has been completed in the
last two decades and now the technology has advanced from a
laboratory-based evaluation of microbial processes, to field
applications internationally. Though research initiatives and
endeavors in MEOR have progressed rapidly, still some questions
remain unanswered. In spite of microbial processes holding great
promise and prospect for EOR, the reasons that retard the
implementation of MEOR include inconsistency in in situ
performance, low ultimate oil recovery factor, uncertainty about
meeting the engineering design criteria by microbial processes
and a general apprehension about processes involving live
bacteria. It is now known that manipulation of microbial consortia
activity is a potentially powerful process that can profoundly and
beneficially affect the microenvironment of a reservoir to mobilize
more oil, increase production rates and technical efficacy of the
recovery systems. In situ application of a judicious consortium of
aerobic and anaerobic bacteria, acclimatized in simulated oil
reservoir conditions, coupled with the bioaugmentation and
stimulation of indigenous microflora have been successful in
enhancing both the oil productivity and ultimate oil recovery
factor. However, a better understanding of the MEOR processes
and mechanisms from an engineering standpoint based on
economics, applicability and performance is the key to further
improve the process efficiency for writing more success stories.
Advanced MEOR technologies based on the use of genetically
engineered organisms and some specific enzymes may prove to be
very effective and successful in the future. Nevertheless, an urge
and urgency in developing novel MEOR technologies in the wake
of an impending energy crisis seem to be imminent, mainly on account of their perceived potential to offer a cost-effective
solution to the conventional EOR strategies