7- Microbial EOR (MEOR)

MICROBIAL EOR (MEOR)MICROBIAL EOR (MEOR)

Dr. Ir. Dr. Ir. DedyDedy KristantoKristanto, , M.ScM.Sc

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What is MEOR ?What is MEOR ?

yy Microbial Enhanced Oil Recovery (MEOR) is the use Microbial Enhanced Oil Recovery (MEOR) is the use of microorganisms to retrieve additional oil from of microorganisms to retrieve additional oil from existing wells, thereby enhancing the petroleum existing wells, thereby enhancing the petroleum production of an oil reservoir. production of an oil reservoir. yy In this technique, selected natural microorganisms In this technique, selected natural microorganisms

are introduced into oil wells to produce harmless byare introduced into oil wells to produce harmless by--products, such as slippery natural substances or products, such as slippery natural substances or gases, all of which help propel oil out of the well.gases, all of which help propel oil out of the well.yy Because these processes help to mobilize the oil Because these processes help to mobilize the oil

and facilitate oil flow, they allow a greater amount to and facilitate oil flow, they allow a greater amount to be recovered from the well.be recovered from the well.

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The Science of MEORThe Science of MEOR

yy The microorganisms used in MEOR can be applied to The microorganisms used in MEOR can be applied to a single oil well or to an entire oil reservoir. a single oil well or to an entire oil reservoir.

yy They need certain conditions to survive, so nutrients They need certain conditions to survive, so nutrients and oxygen are often introduced into the well at the and oxygen are often introduced into the well at the same time. same time.

yy MEOR also requires that water be present. MEOR also requires that water be present.

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Microorganisms grow between the oil and the well's Microorganisms grow between the oil and the well's rock surface to enhance oil recovery by the following rock surface to enhance oil recovery by the following methods: methods:

yy Reduction of oil viscosityReduction of oil viscosity Oil is a thick fluid that is Oil is a thick fluid that is quite viscous, meaning that it does not flow easily. quite viscous, meaning that it does not flow easily. Microorganisms help break down the molecular Microorganisms help break down the molecular structure of crude oil, making it more fluid and easier structure of crude oil, making it more fluid and easier to recover from the well.to recover from the well.

yy Production of carbon dioxide gasProduction of carbon dioxide gas As a byAs a by--product product of metabolism, microorganisms produce carbon of metabolism, microorganisms produce carbon dioxide gas. Over time, this gas accumulates and dioxide gas. Over time, this gas accumulates and displaces the oil in the well, driving it up and out of displaces the oil in the well, driving it up and out of the reservoir. the reservoir.

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yy Production of biomassProduction of biomass When microorganisms When microorganisms metabolize the nutrients they need for survival, they metabolize the nutrients they need for survival, they produce organic biomass as a byproduce organic biomass as a by--product. This product. This biomass accumulates between the oil and the rock biomass accumulates between the oil and the rock surface of the well, physically displacing the oil and surface of the well, physically displacing the oil and making it easier to recover from the well.making it easier to recover from the well.yy Selective pluggingSelective plugging Some microorganisms secrete Some microorganisms secrete

slimy substances called slimy substances called exopolysaccharidesexopolysaccharides to to protect themselves from drying out or falling prey to protect themselves from drying out or falling prey to other organisms. This substance helps bacteria plug other organisms. This substance helps bacteria plug the pores found in the rocks of the well so that oil the pores found in the rocks of the well so that oil may move past rock surfaces more easily. Blocking may move past rock surfaces more easily. Blocking rock pores to facilitate the movement of oil is known rock pores to facilitate the movement of oil is known as selective plugging.as selective plugging.

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yy Production of Production of biosurfactantsbiosurfactants Microorganisms Microorganisms produce slippery substances called surfactants as produce slippery substances called surfactants as they breakdown oil. Because they are naturally they breakdown oil. Because they are naturally produced by biological microorganisms, they are produced by biological microorganisms, they are referred to as referred to as biosurfactantsbiosurfactants. . BiosurfactantsBiosurfactants act like act like slippery detergents, helping the oil move more freely slippery detergents, helping the oil move more freely away from rocks and crevices so that it may travel away from rocks and crevices so that it may travel more easily out of the well.more easily out of the well.

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Microbial Product and Their Microbial Product and Their Application in EORApplication in EOR

Microbial Effect

Acids

Modification of reservoir rock Improvement of porosity and permeability Reaction with calcareous CO2 production

Biomass

Selective or nonselective plugging Emulsification through adherence to hydrocarbons Modification of solid surfaces, e.g., wetting Degradation and alteration of oil Reduction of oil viscosity and oil pour point Desulfurization of oil

Gases

(CO2, CH4. H2)

Reservoir repressurization Oil swelling Viscosity reduction Increase of permeability due to solubilization of carbonate rocks by CO2

Solvents Dissolving of oil Surface active agent Lowering of interfacial tension

Polymers Mobility control Selective or nonselective plugging

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Main Mechanisms of Microorganism in Main Mechanisms of Microorganism in Improve Oil RecoveryImprove Oil Recovery

yy InIn--situ generation of gases such as methane, situ generation of gases such as methane, carbon dioxide, hydrogen or nitrogen from the carbon dioxide, hydrogen or nitrogen from the metabolic processes.metabolic processes.

yy Break down of heavy hydrocarbon by the enzymes Break down of heavy hydrocarbon by the enzymes produced inproduced in--situ by some microorganisms (mostly situ by some microorganisms (mostly aerobic types).aerobic types).

yy InIn--situ generation of chemicals such as situ generation of chemicals such as biosurfactantsbiosurfactants, biopolymers, organic acids and , biopolymers, organic acids and alcohols. alcohols.

yy Reduction of residual oil saturation due to the inReduction of residual oil saturation due to the in--situ generation of gases and chemicals as well as situ generation of gases and chemicals as well as the upgrading of reservoir oil.the upgrading of reservoir oil.

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Main Mechanisms of Microorganism in Main Mechanisms of Microorganism in Improve Oil RecoveryImprove Oil Recovery

yy Plug off high permeability layers (thief zones) in Plug off high permeability layers (thief zones) in injection wells or to redirect the injection fluid into injection wells or to redirect the injection fluid into lower permeability regions by plugging off the lower permeability regions by plugging off the floodedflooded--out high permeability channels.out high permeability channels.

Note : This is accomplished by injecting an inactive Note : This is accomplished by injecting an inactive (spore form) slug of the microbial culture followed (spore form) slug of the microbial culture followed by enough nutrient to activate it inby enough nutrient to activate it in--situ and hence situ and hence increase its size and population. increase its size and population.

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Type of Microbial Processes for Type of Microbial Processes for Improve Oil RecoveryImprove Oil Recovery

Process Production Problem Types of Activity

or Product Needed

Well bore cleanup

(improve oil drainage into well bore)

Paraffin and scale deposits

Emulsifiers, biosurfactants, solvents, acids,

hydrocarbon degradation

Well stimulation

(stimulate release of

oil entrapped by capillaries and brine)

Formation damage, pore damage

High water production

Gas, acids, solvents, biosurfactants

Biomass and polymer production

Enhanced waterfloods

(reduce permeability variation and block

water channels)

Poor displacement efficiency

Poor sweep efficiency

Scouring

Biosurfactants, solvents, polymers

Biomass and polymer production

Nitrate reduction

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Field Applications of MEORField Applications of MEOR

Most field applications of MEOR are conducted on a Most field applications of MEOR are conducted on a cyclic basis.cyclic basis.

yy A slug of the microbial culture and its nutrient A slug of the microbial culture and its nutrient (such as molasses with some nitrates and (such as molasses with some nitrates and phosphates) are injected into a well.phosphates) are injected into a well.

yy The well is then shutThe well is then shut--in for 3in for 3--6 months (called 6 months (called incubation period) to allow for enough production incubation period) to allow for enough production of of bioproductsbioproducts prior to placing the well back on prior to placing the well back on production.production.

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Schematic of MEOR Processes Schematic of MEOR Processes

Bacteria

Nutrient

+ Regenerate

More Bacteria

MetaboliticReactions

and Interaction with fluids

Products useful for EOR

Crude Upgrading

Plugging of thief zones

Gases (CH4, N2, H2, CO2)

Chemicals (Surfactants, Polymers, Acids, Alcohols)

Appropriate Conditions

Temperature 30 - 40 0C

Pressure < 30000 kPa

Salinity < 4% by weight

1 psi = 6.9 kPa

1 atm = 101.3 kPa

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Typical of MEOR CycleTypical of MEOR Cycle

yy Injection into the well 0.05 Injection into the well 0.05 -- 0.1 m0.1 m33 of microbial of microbial culture (with a cell count 10culture (with a cell count 1066 -- 101088 cell/ml).cell/ml).

yy Injection into the well 50 Injection into the well 50 -- 100 m100 m33 of nutrient.of nutrient.yy Nutrient concentration of 2 Nutrient concentration of 2 -- 4 % and 0.03 4 % and 0.03 -- 0.1 % 0.1 %

(by weight) nitrate and phosphate additives.(by weight) nitrate and phosphate additives.

yy Incubation period (shutIncubation period (shut--in) for about 3 in) for about 3 -- 6 months.6 months.yy Production period.Production period.

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Microbial SolutionsMicrobial Solutions

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MEOR Injection Processes MEOR Injection Processes (Injection, Soaking and Shut(Injection, Soaking and Shut--in)in)

3 Drive WaterDrive Water1 Oil ZoneOil Zone

WaterInjection

Well

Separation andStorage Facilities

Production Well

2 MicrobeMicrobe

Microbe + Nutrient with oil & water

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Factor Affecting MEORFactor Affecting MEOR

yy How active and how long these microbes survive.How active and how long these microbes survive.yy The conditions which affect the microbes behavior The conditions which affect the microbes behavior

in the reservoir include temperature, pressure and in the reservoir include temperature, pressure and salinity.salinity.

Optimum reservoir conditions for MEOR are:Optimum reservoir conditions for MEOR are:

yy Temperature Temperature 30 30 -- 40 40 00CCyy PressurePressure less than 30000 less than 30000 kPakPayy SalinitySalinity less than 4 %less than 4 %

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Typical Stimulation of Oil ProductionTypical Stimulation of Oil Production

The stimulation of oil production by The stimulation of oil production by in situ in situ bacterial bacterial fermentation is thought to proceed by one or a fermentation is thought to proceed by one or a combination of the following mechanisms:combination of the following mechanisms:

yy Improvement of the relative mobility of oil to water Improvement of the relative mobility of oil to water by by biosurfactantsbiosurfactants and biopolymers;and biopolymers;

yy Partial Partial repressurizationrepressurization of the reservoir by methane of the reservoir by methane and COand CO22 gases;gases;

yy Reduction of oil viscosity through the dissolution of Reduction of oil viscosity through the dissolution of organic solvents in the oil phase;organic solvents in the oil phase;

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Typical Stimulation of Oil ProductionTypical Stimulation of Oil Production

yy Increase of reservoir permeability and widening of the Increase of reservoir permeability and widening of the fissures and channels through the etching of fissures and channels through the etching of carbonaceous rocks in limestone reservoirs by organic carbonaceous rocks in limestone reservoirs by organic acids produced by anaerobic bacteria;acids produced by anaerobic bacteria;

yy Cleaning of the Cleaning of the wellborewellbore region through the acids and gas region through the acids and gas from from in situ in situ fermentation. The gas serves to push oil from fermentation. The gas serves to push oil from dead space and dislodge debris that plugs the pores. The dead space and dislodge debris that plugs the pores. The average pore size is increased and, as a result, the average pore size is increased and, as a result, the capillary pressure near the capillary pressure near the wellborewellbore is made more is made more favorable for the flow of oil;favorable for the flow of oil;

yy Selective plugging of highly permeable zones by injecting Selective plugging of highly permeable zones by injecting slimeslime--forming bacteria followed by sucrose solution which forming bacteria followed by sucrose solution which "turns on" the production of extra cellular slimes. "turns on" the production of extra cellular slimes. ArealArealsweep efficiency is improved. sweep efficiency is improved.

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WellboreWellbore CleaningCleaning

1. Acids1. Acids

The acids react with various minerals, especially The acids react with various minerals, especially carbonates, and loosen clay particles and other inorganic carbonates, and loosen clay particles and other inorganic deposits.deposits.

2. Solvents2. Solvents

Solvents dissolve or swell the precipitated organic Solvents dissolve or swell the precipitated organic deposits, improving the mobility of the oil phase.deposits, improving the mobility of the oil phase.

3. Biogas3. Biogas

After a shutAfter a shut--in period of about 1 to 4 weeks for anaerobic in period of about 1 to 4 weeks for anaerobic growth, the pressure around the well bore was raised to growth, the pressure around the well bore was raised to 200200--300 300 psipsi. When the well was opened and allowed to . When the well was opened and allowed to blow out, a considerable amount of sludge and drilling blow out, a considerable amount of sludge and drilling mud were removed. The well was then placed back in mud were removed. The well was then placed back in production.production.

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Field Example Application of MEORField Example Application of MEOR

yy Field tests in US, Russia, Poland, Field tests in US, Russia, Poland, ChecoslovakiaChecoslovakia, Hungry, , Hungry, Rumania and Indonesia.Rumania and Indonesia.

yy Depth range 200 Depth range 200 -- 1500 m.1500 m.yy Temperature < 70 Temperature < 70 00C.C.yy Permeability 50 Permeability 50 -- 800 800 mDmD

Reported Response:Reported Response:yy All mechanisms confirmedAll mechanisms confirmedyy Results are encouraging but inconclusiveResults are encouraging but inconclusiveyy Oil production increase, but could be due to effects of well Oil production increase, but could be due to effects of well

shutshut--ininyy Need for additional research is evidentNeed for additional research is evident

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Example Application of MEORExample Application of MEOR

Effectiveness of various surfactant solutions in releasing lightEffectiveness of various surfactant solutions in releasing lightcrude oil from sand (Abucrude oil from sand (Abu--RuwaidaRuwaida et al., 1991; et al., 1991; BanatBanat et al., et al.,

1991;Banat, 1993)1991;Banat, 1993)

Surfactant ST (mN/m) RO (%) RRO (%)

0.1% SDS 27.1 35 0.0

1% Spolene 28.0 33 63.0

1% Petroleum sulfonate 27.5 33 58.0

ST-5 (from Abu-Ruwaida et al., 1991) 27.6 35 80.0

Pet 1006 (from Banat et al., 1991) 29.0 35 95.0

AB-2 (from Banat, 1993 ) 29.0 35 95.0

ST = surface tension; RO = residual oil; RRO = recovered residual oil.

What is MEOR ?The Science of MEORThe Science of MEORThe Science of MEORThe Science of MEORMicrobial Product and Their Application in EORMain Mechanisms of Microorganism in Improve Oil RecoveryMain Mechanisms of Microorganism in Improve Oil RecoveryType of Microbial Processes for Improve Oil RecoveryField Applications of MEORSchematic of MEOR ProcessesTypical of MEOR CycleMicrobial SolutionsMEOR Injection Processes (Injection, Soaking and Shut-in)Factor Affecting MEORTypical Stimulation of Oil ProductionTypical Stimulation of Oil ProductionWellbore CleaningField Example Application of MEORExample Application of MEOR

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7- Microbial EOR (MEOR)