Micro Bi Ally Enhanced Oil Recovery Final

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MICROBIALLY ENHANCED O IL RECOVERY

By- GuideNishant Ranjan Dr. M.N.Varma



NEED FOR MICROBIALLY ENHANCED RECOVERY

Nearly 370 billion barrels of conventional oil willremain in reservoirs worldwide after conventionalrecovery methods have been exhausted. Much ofthis oil would be recovered by Enhanced OilRecovery (EOR) methods



O IL EXTRACTION AND RECOVERY

It basically has 3 stages:Primary recoverySecondary Recovery

Tertiary recovery



P RIMARY RECOVERY During the primary recovery stage,reservoir drive comes from a numberof natural mechanisms. Theseinclude:natural water displacing oil downwardinto the wellexpansion of the natural gas at thetop of the reservoirexpansion of gas initially dissolved inthe crude oilgravity drainage resulting from themovement of oil within the reservoirfrom the upper to the lower partswhere the wells are located

Recovery factor during the primaryrecovery stage is typically 5-15%.



S ECONDARY RECOVERY

It relies on the supply of externalenergy into the reservoir in theform of injecting fluids to increasereservoir pressure, hence

replacing or increasing thenatural reservoir drive with anartificial driveOther secondary recoverytechniques increase thereservoir's pressure bywater injectionnatural gas reinjectiongas lift



TERTIARY RECOVERY Tertiary, or Enhanced Oil Recovery (EOR) methodsincrease the mobility of the oil in order to increaseextraction.Saturation is that fraction or percentage of the porevolume occupied by the fluid.For the oil phase to flow the saturation of oil mustexceed a certain value called critical oil saturation .During the displacing process of crude oil system fromthe porous media by water or gas injection there will besome oil remaining that is quantitatively characterizedby a saturation value larger than the critical oilsaturation. This is called Residual oil saturation.EOR employes a reduction in oil saturation below theresidual oil saturation (S or)



RECOVERY OF RESIDUAL OIL

Mobilization of residual oil is influenced by twomajor factors:Capillary Number (N c)

Mobility Ratio (M)



CAPILLARY NUMBER

Capillary Number is defined asNc = vμ/σ,

where v is the Darcy velocity (m/s), μ is the

displacing fluid viscosity (Pa.s ) and σ is theinterfacial tension (N/m).



MOBILITY RATIO (M)Mobility ratio is defined asM = λing / λed ,

where λing is the mobility of the displacing fluid (e.g. water), and λed isthe mobility of the displaced fluid (oil).(λ = k/μ, where k is theeffective permeability, (m 2) and μ is the viscosity ( Pa.s) of the fluidconcerned).



ENHANCED O IL RECOVERY METHODS

Thermal methods: it includes processes like CyclicSteam Stimulation (CSS), Steamflooding, SteamAssisted Gravity Drainage (SAGD) and In SituCombustionNon-thermal methods: It includes processes likemiscible flooding and chemical floodingOther methods: Some other methods areMicrobially enhanced oil recovery and foamflooding



MICROBIALLY ENHANCED O IL RECOVERY

MEOR is simply the process of utilizingmicroorganisms and their bio-products to enhancethe oil recovery.Bacteria are the only microorganisms used for

MEOR by researchers due to their small size(0.5-5.0 µm), their production of useful metaboliccompounds such as gases, acids, solvents,biosurfactants, biopolymers as well as theirbiomass.Also, their ability to tolerate harsh environmentssimilar to those in the subsurface reservoirs interms of pressure, temperature, pH and salinityincreased their attraction to be used for EORpurposes.



S ELECTION OF MICROBES Microbes can be classified in terms of their oxygen intake intothree main classificationsAerobesAnaerobesFacultative

Successful field experiments mostly used the anaerobic bacteriaas oil reservoirs have very low oxygenated environment

The main sources that are suitable for bacterial isolation are:Formation waters,sediments from formation water purification plants (gatheringstations),sludge from biogas operations and effluents from sugarrefineries.Oil contaminated soilIsolation from hot water streams



MECHANISMS

The mechanisms by which the bacteria can improvethe oil recovery are as follows:Biodegradation of Crude Oil

Gas ProductionProduction of ChemicalsSelective PluggingOther Techniques



BIODEGRADATION OF CRUDE O IL

A proposed mechanism of MEOR is utilization ofbacteria that can degrade crude oil and consume itsheavy fractions. As a result of this process, oilbecomes a lighter and more valuable product as a

result of a decrease in viscosity .Pseudomonas, Arthrobacter, and other aerobicbacteria are especially effective in the degradationof crude oilHowever, this degradation is confined to lighterportions of petroleum —especially paraffins —andbacterial treatment is beneficial for removal ofparaffins from the wellbore, which can restrict theflow seriously.



GAS P RODUCTION

The bacterially produced gases (such as CO2, N2,H2, and CH4) improve the oil recovery in 2 ways:It dissolves in the crude oil and thus reduces itsviscosityIncreases the pressure in the reservoir.The source of this produced gas is in-situfermentation of carbon sources such as glucose byusually anaerobic bacteria. The most importantgas-producing bacteria are Clostridium,Desulfovibrio, Pseudomonas, and certain methanogenes.



P RODUCTION OF CHEMICALS

Chemicals that can be useful in the improvement ofoil recovery such as organic acids, alcohols,solvents, surfactants, and polymers are producedby a wide array of microorganisms.



S ELECTIVE P LUGGING

In this method, polymers or bacteria themselves areused to reduce the permeability of highly permeablezones or of water channels that form inheterogeneous reservoirs. Thus the unsweptformations are invaded by the water and sweepefficiency increasesBacillus, Xanthamonas, and Leuconostoc strainsare reported to be effective in such processes.



OTHER TECHNIQUES

Other uses of bacteria in the petroleum industryinclude the control of unwanted bacteria (such assulfate-reducing bacteria) in oil fields (Hitzman andSperl, 1994) and biodegradation of hazardouswastes caused by petroleum-related activities forthe controlling and removal of environmentalpollution.



MICROBIAL BIOPRODUCTS

BiomassBiosurfactantsBiopolymers

Bio-solventsBio-acidsBiogases



BIOMASS Bacteria are known to grow very fast assome are reported to multiply every 20minutes under aerobic conditions. Themechanism of the microbial biomass inMEOR involves selective plugging of high

permeability zones where the microbialcells will grow at the larger pore throatsrestricting the undesirable water flowthrough them. This will force the displacingwater to divert its path to the smaller poresand hence displacing the un-swept oil and

increasing the oil recovery.Some of the microorganisms used toproduce biomass are: Bacillus licheniformis,Leuconostoc esenteroides, Xanthomonas campestris

Bacillus licheniformis



BIOSURFACTANTS They are amphipatic molecules with bothhydrophilic and hydrophobic parts whichare produced by variety of microorganisms.They have the ability to reduce the surfaceand interfacial tension by accumulating at

the interface of immiscible fluids andincrease the solubility and mobility ofhydrophobic or insoluble organiccompounds.Surfactants are known to reduce theinterfacial forces between oil and water and

thus improve the mobilization of oilSome of the microorganisms used toproduce biosurfactants are: Acinetobacter calcoaceticus, Arthrobacter paraffineus,Bacillus sp., Clostridium sp., Pseudomonas sp.

Acinetobacter calcoaceticus



BIOPOLYMERS These are polysaccharides which aresecreted by many strains of bacteriamainly to protect them againsttemporary desiccation and predation aswell as to assist in adhesion to

surfaces. The proposed processes ofbiopolymers are mainly selectiveplugging of high-permeability zones andthus permeability modification of thereservoir to redirect the waterflood to oilrich channels.

Some of the microorganisms used toproduce biopolymers are: Bacillus polymyxa, Brevibacterium viscogenes,Leuconostoc mesenteroides,Xanthomonas campestris, Enterobacter sp.

Leuconostoc mesenteroides



BIO-SOLVENTS

Sometimes solvents can also beproduced as one of the metabolitesof the microbes. These includeethanol, acetone and butanol. They

may also help in reduction of oilviscosity and can also contribute asa co-surfactant in reducing theinterfacial tension between oil andwater

Some of the microorganisms usedto produce biopolymers are:Clostridium acetobutylicum,Clostridium pasteurianum,Zymomonas mobilis

Clostridium acetobutylicum



BIO-ACIDS

Some bacteria when given certainnutrients can produce acids such aslactic acid, acetic acid and butyricacid. These acids can be useful in

carbonate reservoirs or sandstoneformations cemented by carbonates,since it can cause dissolution of thecarbonate rock and hence improveits porosity and permeability

Some of the microorganisms used toproduce bio-acids are: Clostridium sp., Enterobacter aerogenes

Enterobacter aerogenes



BIOGASES Bacteria can fermentcarbohydrates to produce gasessuch as carbon dioxide, hydrogenand methane gas. These gasescan be used for enhancing oilrecovery by exploiting themechanisms of reservoir re-pressurization and heavy oilviscosity reduction. These gasescan contribute to the pressurebuildup in pressure depletedreservoirsSome of the microorganisms usedto produce biogases are:Clostridium sp., Enterobacter aerogenes, Methanobacterium sp.

Methanobacterium





PHYSICAL AND ENVIRONMENTALCONSTRAINTS

Pore SizeAcidityOxidation Potential

Water and ElectrolytesTemperaturePressure



P ORE S IZE Perhaps the most obvious constraint that applies todeep subsurface microbes is the size of the pores. Insome studies, the lower limit of mean pore sizes hasbeen shown to be smaller than the size of knownbacteria.For example, Frederickson et al. (1997) assessed shaleand sandstone cores from a site in northwestern NewMexico for microbial activity. They found no metabolicactivity was detected in core samples with pore throatsnarrower than 0.2μ m, although in some cases it wasafter extended incubation. The observation of muchhigher levels of metabolic activity in more permeablesamples led these authors to conclude that sustainedbacterial activity require interconnected pores ofdiameter at least 0.2μ m.



ACIDITY The acidity or (alkalinity) of the surrounding aqueous medium,measured by the pH, is significant in several respects:

o Surface Charge: On the cellular scale, pH controls the extentof ionization of the protein molecules that are embedded in thecell walls. As a result, cellular surfaces are generally chargedand surrounded by diffuse double layers, the thickness ofwhich is controlled by the overall electrolyte concentration.Interaction of these ionic space-charge regions with those thatalso surround small particles of mineral phases can stronglyaffect the motion of the cells through a natural porousmedium.

o Enzyme Function: Some of the embedded cell wall proteinsplay a crucial role in the uptake of nutrients, elimination ofwaste products, and maintenance of correct electrolyteconcentrations; on a molecular scale, their ability to performthese functions also depends on their extent of ionization. Therates of the enzymic processes that occur in respiration isstrongly dependent on the pH.



OXIDATION P OTENTIAL Cellular respiration consists of enzymically mediated electrontransfers from an electron donor (reducing agent, in chemicalparlance) to a terminal electron acceptor (oxidizing agent). Thiselectron transfer almost always involves a number ofintermediate electron transfer steps, which can be quite

numerous if the original electron sources are complex moleculessuch as sugars.Thus, for aerobic respiration, the terminal electron acceptor isoxygen, which is reduced to water according to the overallequation

A particularly important electron acceptor in hydrocarbonreservoirs that are not supplied by surface water is sulfate



WATER AND ELECTROLYTES

The concentrations of electrolytes and otherdissolved species required for proper cellularfunction is maintained by enzymically mediatedexchange of solutes or solvent with the surroundingmedium.



TEMPERATURE

The increase in random molecular motion resultingfrom an increase in temperature generally exertsnegative effects on enzyme function, since theactive-site configurations required for catalysis aredisrupted. At still higher temperatures, thehydrogen-bonded three-dimensional arrangementof the amino-acid chains also becomes disordered,resulting in irreversible denaturation.



P RESSURE

Indirect and direct effects of pressure on cellularfunction can be identified.Indirect effect - augmentation of gas solubility withincreasing pressure; this could affect the oxidationpotentials if the gases concerned are electrondonors or acceptors (such as hydrogen or oxygen,respectively).Direct effect - Growth rates of normal bacteriadecrease to zero as hydrostatic pressureapproaches about 40 Mpa.



MEOR P ROCESSES

Microbial floodingCyclic Microbial recovery







COMPARISION

AdvantagesLow operating costLow energy consumption

Does not depend on oil pricesDisadvantages

Reservoir’s environment may not be favorable for the pathogenic organisms to grow

Inconsistent technical performance and lack ofunderstanding of the mechanism of oil recoveryAbsence of standardized field results and post trialanalysis





MATHEMATICAL MODELLING

The constraints are expressed by the relation between theresidence time of the bacteria in a cylindrical reaction regionof radius r m and depth h and porosity υ , which is

where Q is the volumetric flow rate and S or is the residual oilsaturation, and the time τrxn required for the microbial reactionto produce a desired concentration c req of some metabolite Cfrom nutrient N

To estimate the reaction time, isothermal plug flow through thereactor is assumed, the consumption of N is first order andirreversible, and that it is injected at initial concentration n 0 .The rate equation is



where the stoichiometric coefficient νn defines theconversion efficiency of nutrient into product. Whenintegrated subject to the initial condition n (0) = n o ,

The kinetic equation for c is therefore

which, when integrated subject to the initial condition c (0)= 0 , gives

The limiting state implied by this equation is completeconsumption of the nutrient, and from this result thereaction time needed to establish the desiredconcentration c req is



CONCLUSIONS

In conclusion, MEOR is well-proven technology toenhance oil recovery from oil wells with high watercuts and also to improve it in mature oil wells, butstill in order for MEOR processes to be well

accepted and successful, extensive laboratory testsare required prior to field implementation to selectthe suitable microbes, to understand their growthrequirements and production conditions.



REFERENCES H. Al-Sulaimani S. Joshi, Y. Al-Wahaibi, S. Al-Bahry, A.Elshafie, A. Al- Bemani, Microbial biotechnology for enhancingoil recovery: Current developments and future prospects,Biotechnol Bioinf, 2011Fundamental Aspects of Microbial Enhanced Oil Recovery: ALiterature Survey Simon L. Marshall SIRO Land and WaterFloreat, Western Australia March, 2008Enhanced Oil Recovery – An Overview, S. Thomas, Oil & GasScience and Technology – Rev. IFP, Vol. 63 (2008), No. 1, pp.9-19Enhanced oil recovery using microorganisms, Hitzman, USpatent 1984Enhanced Oil Recovery, Ronald E. Terry, Encyclopedia ofphysical science and technology, 3 rd edition vol 18, pg 503-518Fundamental Aspects of Microbial Enhanced Oil Recovery: ALiterature Survey, Simon L. Marshall CSIRO Land and WaterFloreat, Western Australia March, 2008



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Micro Bi Ally Enhanced Oil Recovery Final