Tiny and invisible, bacteria are often maligned as ‘bugs’ that
cause diseases in humans and animals. Little do we know of how wonderfully they
help sustain life on earth. As the base of the food chain in many environments,
they do the most inane and tedious of jobs—from breaking down dead, organic
matter and recycling natural resources to putting that tang in yoghurt, and
that sour taste in dough bread. And now, scientists at TERI have developed ways
of utilizing these bacteria to extract oil from ‘sick’ or less productive
oil wells and putting them back in business.
A technological breakthrough
Microbial biotechnology came to the rescue when researchers at TERI cultured
a set of microbes that could survive temperatures as high as 90°C, air
pressure up to 140 kilograms per square centimetre, and strong salinity with
concentration levels ranging from 4% to 8%. Techniques used earlier for oil
recovery employed microbes that could bear temperatures only up to 65 °C.
TERI cultured these stronger bacteria in simulated conditions of oil wells complete
with high temperature, high pressure, and heavy salt concentration. The product
was successfully tested in oil wells in Gujarat and the rest, as they say, is
history.
Tackling critical needs
Ageing of wells is a perpetual and crucial concern that the global oil industry
faces. Thousands of oil wells lie abandoned—they are either unproductive
or yield oil in insignificant quantities. An oil well becomes sick when approximately
30% of oil in place has been recovered. The reason: natural gas in the reservoir
(responsible for pushing oil up to the mouth of the well) diminishes in quantity
and loses pressure because of deep extraction. As a result, the oil flow decreases
and eventually stops. These so-called dead or sick wells still have a substantial
quantity of oil left in them. Conventional methods of recovery are extremely
expensive and costs can vary from 140 000 to 200 000 dollars per well.
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| Preparing nutrients for injection into the oil well |
However, as oil reserves dry up globally, the depth of wells increases, and
temperatures inside the reservoirs also increase (it varies between 80 °C
and 120 °C), these methods prove ineffective and the task becomes more challenging.
From ‘unwell’ to ‘oil well’
The MEOR (microbial enhanced oil recovery) mechanism of extracting oil from
less productive wells has solved an age-old problem that perplexed the oil industry
the world over. Also called the huff-puff method of oil recovery (it involves
injecting microbes and then sucking up oil), it extracts over three times the
oil than any other conventional process.
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| Mixing nutrients with microbes |
After these microbes are injected into an oil well, they take close to a fortnight
to do their job. What happens in the oil reservoir during the incubation time
makes for interesting study. To understand it better, one needs to visualize
rocks with pores, much like a honeycomb. Oil, being viscous, is trapped in these
pores.
These microbes produce carbon dioxide and methane, gases that enter the pores
and squeeze out every ounce of oil. They also produce bio-surfactants (detergent-like
compounds) that reduce the tension between oil and the rock surface and help
release the oil. The reaction of these microbes in oil also releases alcohol
and volatile fatty acids. The alcohol reduces the viscosity of oil, making it
light enough to flow out. The fatty acids solubilize the rock surface and thus
push oil off them. The MEOR process of oil recovery actually offers more than
the advantages of conventional methods of oil recovery plus the added strengths
of the microbes.
Beneficiaries
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| Injecting selected microbes into the oil well |
Wells of the ONGC (Oil and Natural Gas Corporation) in Gujarat have been revived,
thanks to this technology, and are functioning again. The MEOR technology, when
applied in 25 oil wells of ONGC, extracted 4500 cubic metres of oil from one
of the sick wells, translating into revenues of more than 675 000 dollars. The
Company plans to use the technology for other sick oil wells in Gujarat and
Assam. Its benefits such as cost-effective use and environment-friendly nature
have generated interest among oil firms in the Middle East and other oil-producing
countries.
Funded partly by the Department of Biotechnology, Government
of India, the project received financial assistance of 10 million rupees from
ONGC, and technical and infrastructural support from the IRS (Institute of Reservoir
Studies), a research wing of ONGC. T E R I and ONGC have already jointly applied
for a patent for this technology.
Applications/benefits
Oil recovered through T E R I’s microbial technology has helped bring
down the cost of oil substantially. Depending upon the nature of recovery, the
price of each barrel of oil can decrease by as much as 35%–40%. Moreover,
the environment-friendly nature of this form of oil recovery gives it an edge
over other conventional methods. The possibilities that these invisible, living
organisms offer us are immense and still not fully tapped.
