BIOREMEDIATION AND

MICROBIAL ENHANCED OIL RECOVERY

SATYAJIT PRADHAN DARSHI PATNI NEHA OLI

WHAT IS BIOREMEDIATION? It is a process which uses naturally occurring microorganisms to enhance normal biological breakdown. How does it work? Microorganisms break down petroleum based compounds and convert them to carbon dioxide and water, eliminating the oil and grease in the cleaning solution and eliminating the need to transport hazardous materials.

Types of bioremediation In-situ: This involves treating the contaminated material at the site. Ex-situ: When bioremediation is carried out by displacement of the contaminated soil to another site for treatment.

Several factors influence the success of bioremediation: 1. The type of bacteria present at the site 2. The physical and chemical characteristics of the oil and the oil surface area. The three main approaches to oil-spill bioremediation are: 1. Bio augmentation: Oil-degrading bacteria are added to supplement the existing microbial population.

2. Bio enhancement: Nutrients or other growth limiting substances are added to stimulate the growth of indigenous oil degraders. 3. Bio stimulation:The use of indigenous microbes to promote the growth of native microbes, already present in the soil, so as to modify the site for bioremediation.

WHY BIOREMEDIATION?

Freezing of oil, deposition of semi-solid compounds and rusting of steel cause rupture of pipelines leading to oil spills. This becomes an important environmental concern. Of all the different processes available for clean-up of sites, bioremediation is the best and most cost effective method for remediation, with respect to environmental liability. Thus, it serves as a cheap, eco-friendly solution to clean the land and sea of oil spills.

OIL ZAPPER It is developed by TERI after seven years of research work and partly supported by the DBT (Department of Biotechnology), Ministry of Science and Technology, Government. The Oilzapper is neatly packed into sterile polythene bags and sealed aseptically for safe transport. The shelf life of the product is three months at ambient temperature.

What is Oil zapper? 1. It is a consortium of four bacterial strains. 2. Each bacteria feeds on different layers of crude oil i.e. a) waxy element/ saturated hydrocarbons b) aromatic component/ benzene compounds. c) NSO (compounds of nitrogen and sulphur) d) Asphaltene or tar It thus degrades the total petroleum hydrocarbon by its metabolic processes, converting hazardous substances into water, carbon dioxide and fatty acids.

1.A carrier material is used along with oil zapper. 2.It is an organic plant material(powdered corncob). 3.It helps in retaining moisture in contaminated soil and creates air pockets in soil, thus requiring less water. 4.This increases the rate of bioremediation. 5. The sludge eating bacteria can increase in number when an oily sludge is available. 6. When the contaminated is bio remediated, the microbial population naturally declines.

How does oil zapper act?

Crude oil contains hydrocarbon chains. Bacteria’s enzyme will catalyse the insertion of oxygen into the hydrocarbon,

so that the molecule can subsequently be consumed by cellular metabolism.

Carbon hydrogen bond is an excellent source of energy for the bacteria in oil zapper. So, it gets easier to degrade the

petroleum product.

The microbes used are either present in the environment, or they can be added by culture grown from other

contaminated areas or being genetically engineered.

METABOLIZING ACTION BY MICROBES

OIL- CONTAMINATED SOIL

MEOR—Microbial Enhanced Oil Recovery

The MEOR technology involves the use of specific microbes capable of producing useful metabolites (gases, solvents, surfactants, polymer, acids etc.) to recover additional oil from depleted petroleum reservoirs.

Why MEOR? 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. 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.

So the technique on MEOR is used, in which hyperthermophilic microbes are used to extract the remaining oil from the so-called dead or sick wells.

Outcomes of MEOR The outcomes of MEOR are explained based on two

predominant rationales: Increment in oil production- This is done by modifying

the interfacial properties of the system oil-water-minerals, with the aim of facilitating oil movement through porous media.

In such a system, microbial activity affects fluidity (viscosity reduction, miscible flooding); displacement efficiency (decrease of interfacial tension, increase of permeability); sweep efficiency (mobility control, selective plugging) and driving force (reservoir pressure).

Upgrading- In this case, microbial activity acts may promote the degradation of heavy oils into lighter ones. Alternatively, it can promote desulfurisation due to denitrification as well as the removal of heavy metals.

Advantages of MEOR Injected microbes and nutrients are cheap; easy

to handle in the field and independent of oil prices.

• Economically attractive for mature oil fields before abandonment.

• Increases oil production. • Existing facilities require slight modifications. • Easy application. • Less expensive set up.

Low energy input requirement for microbes to produce MEOR agents.

More efficient than other EOR methods when applied to carbonate oil reservoirs.

Microbial activity increases with microbial growth. This is opposite to the case of other EOR additives in time and distance.

Cellular products are biodegradable and therefore can be considered environmentally friendly.

Disadvantages of MEOR The oxygen deployed in aerobic MEOR can act as corrosive

agent on non-resistant topside equipment and down-hole piping

Anaerobic MEOR requires large amounts of sugar limiting its applicability in offshore platforms due to logistical problems

Exogenous microbes require facilities for their cultivation. Indigenous microbes need a standardized framework for

evaluating microbial activity, e.g. specialized coring and sampling techniques.

Microbial growth is favoured when: layer permeability is greater than 50 md; reservoir temperature is inferior to 80 0C, salinity is below 150 g/L and reservoir depth is less than 2400m.

Classification of MEOR MEOR is classified as :-

Surface MEOR and underground MEOR based on the place where microorganisms work.

Surface MEOR, bio-surfactant , biopolymer (xanthan gum), and enzyme are produced in the surface facilities. These biological products are injected into the target place in the reservoirs as chemical EOR methods.

Underground MEOR, microorganisms, nutrients and/or other addictives are injected into the reservoir and let them sustain, grow, metabolize, and ferment underground.

Two microbial consortia used in MEOR are:-

Used in pipe - IRSM-1 –Clostridium, Bacillus

Thermophilic 45-65º C, Halophilic, Anaerobic Or

PDS10- Geobacillus kaustophillus Thermophilic – upto 90⁰C but optimum activity at 55⁰C, Anaerobic

Used in reservoir-

S-2 -Three Hyperthermophilic

Hyperthermophilic to 90º C, Halophilic, Barophilic, Anaerobic

Properties of microbes used in MEOR

General properties of microbes:- • Small Size

• Resistant to High Temperatures

• Resistant against High Pressure

• Capability of Withstand Brine and Seawater

• Anaerobic Using of Nutrients

• Unfastidious Nutritional requirements

• Appropriate Biochemical Construction for Production Suitable Amounts of MEOR Chemicals

• Lack of any Undesirable Characteristics

MICROBES IN THE PIPE:- • The microbes are :-

Thermophilic consortium (90⁰C,optically active at

55⁰C)

Micro aerophilic consortium

• Non pathogenic

• Gram negative

• Carbon source:- glucose and wax

• pH – 6 to 8

• Incubation period – 7 days

MICROBES IN THE RESERVOIR:- •The microbes are HYPERTHERMOPHILIC –

•Obligate anaerobes(-300 to -400 redox) •Thermophilic (90º C, attempt to 110º C) •Halophilic (7-4% salinity) •Barophilic (4500 psi) •Acidogenic (~pH 4.0)

•Gram negative •Non pathogenic. •Carbon source :- Sugar cane

•Nitrogen source:- Urea, Ammonium sulfate

Effects: • Gases, increase reservoir P, push oil out with gas drive • Gases, solvents and weak acids reduce viscosity: oil gets thinner and flows more freely • Surfactants (e.g. glycolipids, lipopeptides) emulsify oil- water, reduce surface tension and interfacial tension • Acids, dissolve carbonates, increase perm • Biopolymers, plug thief zones, access of secondary pathways • Bio films, influence on flow properties

How it works? • A large volume (120 cubic meters) of

bacterial culture with nutrient in aqueous media is pumped into well (wells must have significant water cut in order to facilitate bacterial growth).

• Well is kept shut-in for a significant period (almost for about 21 days) to allow bacterial growth.

• In nutrient broth bacteria rapidly multiply. • CO2, volatile fatty acids and bio-surfactants

are released as the bacteria consume nutrient feed.

•Generated acids dissolve rock, clean the pores and improve absolute permeability. •Produced gases re-pressurize the pores and push oil out of pore spaces & reduce oil viscosity. •Produced bio-surfactants reduce interfacial tension between oil and water and facilitate mobilization of trapped oil.

•Production of biopolymers increase water viscosity and improve mobility ratio.

•Bio-film developed on solid surface physically displace oil.

Paraffin Deposition Bacteria and

Wax Deposition Prevention

Method:-

When the oil is completely removed or taken out from the reservoir to column pipe , its temperature decreases from about 90⁰C to 50 -60⁰C.

As the temperature decreases the wax and paraffin present in the crude oil start solidifying and narrowing the column.

A microbe PDS10 (Paraffin Degrading Strain) is used to remove those solidified wax and paraffin. (Growth time is 5 days, add 30-40cubic meters of growth culture in the pipe)

The microbe metabolizes wax and paraffin into CO2 H2O and simpler products.

Biofilm is formed by bacteria which does not let oil or wax to adhere on the surface of the pipe.

When the wax starts depositing inside the pipes present on the surface of the earth (due to very low temp i.e., 37⁰C), WDP (Wax deposition Preventive strains) is added. (growth time 5 days and 30cubic meters of growth culture is added in the pipe)

The same process is activated. Wax is metabolized by the bacteria present in the growth culture and biofilm is formed.

Due to this, oil doesn’t stick at the surface of the pipes and we get a good production in an oil reservoir.

Oil and Natural Gas Corporation MEOR Projects, India 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.

Summary and Conclusions Up to 3 fold increase in oil production Significant reduction in water cut Longevity of 8-12 months Indigenous formation-organisms were most successful Incremental pay back of 2 to 3 months » formation characteristics » source of microbes. Cost/bbl and payback: » Thermophilic consortium $3/bbl in 2 months (IRSM-1 culture) » Hyperthermophilic consortium $6/bbl in 3 months (S-2 culture)