Microbial Enhanced Oil Recovery
Microbial Enhanced Oil Recovery1Introduction
US Energy Information Administration:
http://www.eia.gov/totalenergy/data/annual/perspectives.cfmFossil
Fuel still remains key energy sourceOil ProductionPrimary Oil
Recovery: 5-10% of total reserveUse of natural pressure drive of
reservoirSecondary Oil Recovery: 10-40%Injection of fluids into
wells (water-flooding)Fossil fuels are the major source of energy
today. And despite increasing investments in the renewable energy
sector it is slated to remain the dominating source of energy in
the foreseeable future. Of the total energy production sources, oil
and gas amounts to almost 60%. This oil and gas is found deep
inside earths surface in complex capillary network of oil
reservoirs. The oil present in these reservoirs is recovered mostly
by Primary and Secondary oil recovery techniques. Primary
techniques make use of the natural pressure drive of the reservoir
to siphon out the oil present. Secondary techniques usually deal
with injecting a secondary fluid into the reservoir to flush out
the oil from the capillaries. 2IntroductionResidual Oil: 67% of
total oil reservesEnhanced Oil RecoveryAims at recovery of the
residual oilChemically Enhanced Oil RecoveryInjection of polymers,
surfactants, etc.Thermally Enhanced Oil RecoveryInjection of steam,
in-situ combustion, etc.
However, even after primary and secondary production, almost
2/3rd of the total oil ever found is still present inside these oil
reservoirs. This is called the residual oil. It is often located in
regions of the reservoir that are difficult to access and is held
in the pores by strong capillary pressure. With increase in oil
prices (especially during the Arab Oil Embargo of 1970s), it became
more and more important to find techniques that target this
specific problem. This gave rise to the Enhanced Oil Recovery
Techniques. Chemically Enhanced Oil Recovery deals with injecting
chemicals like polymers, surfactants, acids into the reservoirs.
Polymers increase the viscosity of the oil thereby aiding the flow,
while surfactants reduce the surface tension leading to easy
release of oil from the pores. However, most of these chemicals are
petrochemicals. Thus, CEOR may be unattractive as it finished
products are utilized for recovery of raw materials.3Introduction:
Microbial Enhanced Oil Recovery
Array of techniques that utilize microorganisms and the
metabolic products to increase the recovery of oil from depleted
and marginal reservoirs, thereby extending the life of oil
wellsProposed in 1926 by Beckman, but results from ZoBell led to
interest
Exploit microorganism which produce chemicals like biopolymers,
biosurfactants, etc.R. Sen/ Progress in Energy and Combustion
Science 34 (2008) 714-724Thus, we move towards a cost-effective
alternative: MEOR. MEOR is the collection of techniques that
utilizes microorganisms and the metabolites it produces to increase
the oil recovery. Basically, we produce all the chemicals required
for CEOR with help of microorganisms. Some of the useful metabolic
products are mentioned in the table along with its application.
Beckman proposed that microbial processes can aid in oil recovery
in 1926 but it was only after the work of ZoBell that the process
was considered seriously.4MEOR: Application Strategies &
TechniquesTwo Broad Categories:Injection of microorganisms and
nutrients into the reservoirsStimulation of indigenous
microorganisms by injection of nutrients
TechniquesCyclic Microbial RecoveryMicrobial FloodingSelective
Plugging
MEOR application can be classified in two broad categories.
First involves injection of microorganisms an nutrients into the
reservoir. Second deals with just the injection of nutrients to
stimulate the growth of microorganisms which are already present in
the wells. There are many ways in which MEOR can be applied. In
cyclic MEOR , the microorganisms and nutrients are injected in the
wells. The wells are then shut for a period long enough to allow
metabolite production which then leads to the oil production phase.
In microbial flooding, microbial growth is stimulated by adding
water to injection water. If the required microbial activity is not
present then microorganisms can also be injected along with
nutrients.In selective plugging, we use microbial growth to divert
water into low permeability regions. Biomass and biopolymers form
inside the high permeability regions thereby increasing the
permeability.5
