Enhanced oil recovery techniques - petrofed.winwinho...

Enhanced oil recovery techniquesDinesh C TewariInstitute of Reservoir StudiesOil and Natural Gas Corporation LimitedAhmedabad22 December 2009 Sivasagar

WHAT COMES TO MIND WHEN THEPRODUCTION OF YOUR WELLSSTART TO DECLINE?What is the purpose of EnhancedOil Recovery?• EOR is intended to improve –– displacement efficiency (at pore level)– sweep efficiency (vertical and areal)• Reduction of residual oil saturation isthe key to improving displacementefficiency, which is determined by theCapillary Number

Primary RecoverySecondary RecoveryTertiary RecoveryThermalGasChemical

PRIMARY AND SECONDARY RECOVERYAfter primary and secondary recovery (waterflood) oilremains in the reservoir as: uncontacted (unswept) oil (So = 1 - Swi) partially removed oil (1 - Swi < So > Soi) residual oil (So = Soi)Secondary and tertiary recovery are together referred toas enhanced oil recovery (EOR).

Incremental IOR/EOR OilIncremental IOR/EOR Oil by means of :IOR Improved Mobility ratioIOR Improved Areal SweepIOR Improved Vertical SweepEOR Lower Residual Oil Saturation

Thermal EOR MethodsTHERMALHot Water Steam In-Situ Elec. HeatCSSSteamFloodSAGDConductiveHeating Forward ReverseHi Press.Air Inj.FracNon-FracVAPEXVAPEX + SteamSAGPDryWetW / AdditivesTHAICAPRI

Thermal EOR ProcessThe principle of thermal EOR is that heat increases the mobility ofoil by reducing the viscosity.Oil mobility is increased relative to that of water and the mobilityratio is reduced allowing more favourable displacement.

Thermal EOR Process•Steam Flooding Process: In this process, steam iscontinuously introduced into an injection well. When steam isinjected into the reservoir, heat is transferred to the oilbearing formation, reservoir fluids and some of the adjacentcap and base rock. The heat reduces the oil viscosity. Thisincreases the mobility of oil.•As the steam loses heat energy it condenses to yield amixture of steam and hot water. Because of pressure gradienttowards producing well, an oil bank is formed ahead of steamzone. This enables the immobile oil to get produced from thereservoir. In general steam reduces the oil saturation in thesteam zone to very low value (about 10±%. Some oil is alsotransported by steam distillation.

Thermal (Steam flooding)

Thermal EOR ProcessTechnical Screening GuidelinesCrude OilGravity : 20cPComposition: Not critical but some light ends for steamdistillation will help.ReservoirType of formation : Sand or sand stone with highporosity and Permeability preferredNet Thickness : >15 feetAverage permeability : >10mDDepth : 300-5000 ftTemperature: Not Critical

Thermal EOR ProcessLimitations :•Oil saturation must be high, and the pay zone should bemore than 15ft thick to minimize the heat losses toadjacent formations.•Lighter, less viscous crude oils can be steam flooded, butnormally they are not if reservoir responds to an ordinarywater flood.•Steam flooding is primarily applicable to viscous oil inmassive, high permeability sandstones or unconsolidatedsands.

Thermal EOR ProcessLimitations :•Steam flooded reservoirs should be as shallow as possibleas long as pressure for sufficient injection rates can bemaintained. This is to avoid excessive heat losses in thewell bore.•Steam flooding is not normally used in carbonate reservoir.•Cost per incremental barrel of oil is high.•Low percentage of water-sensitive clays is desired forgood injectivity.•Adverse mobility ratio and channeling of steam may makethis process unattractive.

Steam Flooding (Huff and Puff)

Steam Assisted Gravity DrainageHorizontal wells drilled in stacked pairs form the basic unit of SAGDproject (top). Steam injected into the upper well melts surrounding oil(bottom). Gravity causes the mobilized oil to flow downward to thelower well for production.

Thermal EOR ProcessIn-situ Combustion ProcessThis process involves starting a fire in the reservoir and injectingair to sustain the burning of some of the crude oil, usually incombination with water. A combustion front is formed at whichthe injected air burns a small portion of the reservoir oil. Theprocess combustion can be achieved through low temperatureoxidation and high temperature oxidation. Low temperatureoxidation is suited for light oil. Hot flue gas and steam resultingfrom combustion and water vaporization displace the oil aheadof the combustion front. Vaporization of the light ends andthermal cracking also occur. Ahead of the combustion front, thevaporized light ends condense, providing some assistance todisplacement by solvent dilution of the virgin crude.

Thermal EOR Process

Air injectionSCHEMATIC OF SPONTANEOUS IGNITIONSpontaneous IgnitionBridge Plug

TEB port for loading TEBGas InjectionSCHEMATIC OF ARTIFICIAL IGNITIONAir injectionGas BurnerBridge Plug

In-situ Combustion

Thermal EOR ProcessTechnical Screening GuidelinesCrude OilGravity: 15 feetAverage flow capacity : > 20 mD-ftDepth: > 500 ftTemperature: 150oF preferred

LimitationsThermal EOR ProcessThe process will not sustain if sufficient coke is not deposited.Excessive deposition of coke will lead to low advancement ofcombustion front and eventually killing of the process in the presenceof sufficient quantity of air.Oil saturation and porosity must be high to minimize heat loss to rock.Produced flue gases can pose environmental problem.Operation problems such as severe corrosion caused by low pH hotwater, increased sand production, pipe failures as a result of high htemperature and adverse mobility ratio makes this processcomplicated and difficult.Heterogeneous formation can result in poor sweep efficiency.

1008060W/c, %40200Nov-07Nov-06Nov-05ISC Pilot Project : BechrajiNo. of Flowing wells : 121Air Injectors on stream : 4Air Injection Rate, Nm3/d: 100000Cum. Air Injection, NMMm3 : 60Oil rate, tpd : 22Water Cut, % : 55Primary recovery : 10%Recovery with EOR : 45%1000800Inititiation of ISC600400Oil RateW/C2000Drive- Active Bottom WaterNov-04Nov-85Nov-86Nov-87Nov-88Nov-89Nov-90Nov-91Nov-92Nov-93Nov-94Nov-95Nov-96Nov-97Nov-98Nov-99Nov-00Nov-01Nov-02Nov-03RF - 10.2 %Viscocity - 300 cpOil rate, tpd

W/c, %Balol FieldBalol FieldIn-situ combustion pilot : March 1990Semi-commercial Phase : Jan. 1992Commercial Phase : Oct. 1997Primary Recovery : ~ 10 %Envisaged additional recovery : 36 % :~ 6.57 MMt1000100800Inititiation of ISC80600400W/COil Rate60402000Nov-85Nov-86Nov-87Nov-88Nov-89Nov-90Nov-91Nov-92Nov-93Nov-94Nov-95Nov-96Nov-97Nov-98Nov-99Nov-00Nov-01Nov-02Nov-03Nov-04Nov-05Nov-06Nov-07Oil rate, tpd200Drive- Active Edge WaterRF - 44.8 % ( PR-13%)Viscocity - 150 to 1000 cp

Jun-12Santhal FieldSanthal FieldCommercial Phase : Oct. 1997Primary Recovery : ~17 %Envisaged additional recovery: 30 % : 14.57MMtOIL GAIN BY EOR (IN-SITU COMBUSTION) IN SANTHAL FIELD2000Oil Gain by EOR = 1.122 MMt Till Aug '041500START OF ISC10005000EORACTUALENVISAGED PRIMARY RECOVERYJun-74Jun-76Jun-78Jun-80Jun-82Jun-84Jun-86Jun-88Jun-90Jun-92Jun-94Jun-96Jun-98Jun-00Jun-02Jun-04Jun-06Jun-08Jun-10TIME------>Drive- Active Edge WaterRF - 42.8 % ( PR-17%)Viscocity - 50 to 150 cpOIL T/day------->

Non-Thermal EOR MethodsNON-THERMALMiscibleChemicalImm. GasDrivesOtherSlug ProcessPolymerCO 2MEOREnrichedGas DriveSurfactantFlue GasFOAMVaporizingGas DriveAlkalineInert GasCO 2 MiscibleMicellarN2 MiscibleASPAlcoholEmulsion

180160140120100806040200173100Chemical EOR ProcessChemical EOR ProcessAssumed:Primary Rec. 33.3 %OOIPChem. Flood Rec. 33.3 %OIP84 7763 61514026 2412 10 10 9 7 6 4 4 3 3 0.90.6 0.3 0.2Billion BblsS. ArabiaUSAIranIraqKuwaitAbu DhabiVenezuelaRussiaLibyaNigeriaChinaQatarMexicoCanadaBrazilNorwayOmanIndiaUKDubaiDenmarkRomaniaGermanyFrance

Chemical Floods Current Status WorldwideFranceIn d iaIndonesiaVenezuelaUSAChinaTotal Number of Projects: 27

Chemical EOR ProcessOBJECTIVES OF CHEMICAL FLOODING• Increase the Capillary Number Nc to mobilize residual oil• Decrease the Mobility Ratio M for better sweep• Emulsification of oil to facilitate productionThe process also called as micellar or micro emulsion flooding,consists of injecting a slug that contains surfactant, co-surfactants, oil, water and other chemicals. The function of thesurfactant is to reduce oil/water interfacial tension, but it mayalso cause inter phase mass transfer of reservoir oil and water.Both the inter phase mass transfer and reduction of IFT increaserecovery of oil. Surfactant slug is often followed by polymerthickened water to improve sweep efficiency.

Chemical EOR Process

WATER FLOODInjectorProducer

WATER FLOODInjectorProducer

WATER FLOODInjectorProducer

WATER FLOODInjectorProducer

WATER FLOODInjectorProducer

SURFACTANT FLOODSurfactant follows the waterchannels through the formation

SURFACTANT FLOODInjectorProducer

SURFACTANT FLOODInjectorProducer

SURFACTANT FLOODInjectorProducer

SURFACTANT FLOODInjectorProducer

SURFACTANT FLOODInjectorProducer

SMART SURFACTANT FLOODSmart Surfactant seeks out oilbearingchannels, blocks waterchannels

SMART SURFACTANTInjectorProducer

SMART SURFACTANTInjectorProducer

SMART SURFACTANTInjectorProducer

SMART SURFACTANTInjectorProducer

SMART SURFACTANTInjectorProducer

SMART SURFACTANTInjectorProducer

Chemical EOR Process

Chemical EOR ProcessTechnical Screening GuidelinesCrude OilGravity: > 20o APIViscosity : < 100 cPComposition: Light intermediates are desirableReservoirType of formation : Sand stone preferredNet Thickness : > 10ftAverage permeability : > 10mDDepth: 950 to 9000 ft( temperature!)Temperature:

LimitationsChemical EOR Process•Adsorption of chemicals can be detrimental to the process.High temperature leads to degradation of chemicals.•Best results are obtained when alkaline material reacts with crude oil.The oil should have acid number more than 0.2 mg KOH/g of oil.•High amounts of anhydrite, gypsum or clays are undesirable.•Formation water chloride of < 20,000 ppm and divalent ions (Ca++and Mg++)

Chemical EOR ProcessPolymer ProcessThe objective of polymer flooding is to provide betterdisplacement and volumetric sweep efficiencies during awater flood. They do not lower the residual oil saturation.They improve recovery by increasing the viscosity ofwater, decreasing the mobility of water, contacting a largevolume of the reservoir and reducing the injected fluidmobility to improve aerial and vertical sweep efficiencies.Because, polymer flooding inhibits fingering, the oildisplacement is more efficient in the early stages ascompared to a conventional water-flood

Chemical EOR Process

Chemical EOR Process

Chemical EOR Process

Chemical EOR Process

Chemical EOR ProcessTechnical Screening GuidelinesCrude OilGravity: > 15o APIViscosity : 10ftAverage permeability : > 10mDDepth: < 9000 ft( temperature!)Temperature: < 229o

Chemical EOR ProcessLimitations and Facts•There are two types polymer synthetically produced polymers(Acrylamidetype) and bio-polymers (Xanthum(gum).•Factors which degrade polymers are salinity, temperature, time,shear rate and presence of divalent ions.•Bio-polymers suffer from bacterial degradation and cause well boreplugging.•Polymers may be ineffective in a mature water flood because of low lmobile oil saturation.•High adsorption on reservoir rock may kill the process.•Optimum temperature is a key selection criterion for polymers. Clay Cincrease polymer adsorption.•If oil viscosities are high, a higher polymer concentration is needed nto achieve the desired mobility control.•Some heterogeneity is acceptable but for conventional polymerflooding, reservoirs with extensive fractures should be avoided.

Polymer Flood: SanandInjectors :Polymer - 13, Chase Water - 7Injection Rate : 910m3/d (800ppm) , 490m3/d (Water)Envisaged addl. Recovery: ~ 14 %Drive- Active Edge WaterRF - 31.5 %Viscocity - 20 cp

140120100water cut (%)Polymer Flood: SanandPolymer Flood: Sanand806040500450400350300250200150100500200Oil rate (m 3 /d)5/1/19696/1/19707/1/19718/1/19729/1/197310/1/197411/1/197512/1/19761/1/19782/1/19793/1/19804/1/19815/1/19826/1/19837/1/19848/1/19859/1/198610/1/198711/1/198812/1/19891/1/19912/1/19923/1/19934/1/19945/1/19956/1/19967/1/19978/1/19989/1/199910/1/200011/1/200112/31/20021/31/20042/28/20053/31/2006

JhaloraDrive- Active Edge WaterRF - 36.6 %Viscocity - 5-35 cp

Gas Based EOR Process

Gas Based EOR ProcessGas Injection is the second largest enhanced oil recoveryprocess, next only to thermal processes used in heavy oilfields. The residual oil saturations in gas swept zones havebeen found to be quite low, however, the volumetric sweepof the flood has always been a cause of concern. Themobility ratio, which controls the volumetric sweep,between the injected gas and displaced oil bank in gasprocesses, is typically highly unfavorable due to therelatively low viscosity of the injected phase. This differencemakes mobility and consequently flood profile control thebiggest concerns for the successful application of thisprocess.

Gas Contribution to Green House Effect

Gas Based EOR ProcessMiscible & immiscible gas injection processIn miscible gas injection process mass transfer occur betweenoil & gas & forms a transition zone to displace the oil effectively.ely.Miscible gas injection gives better displacement efficiency.Immiscible gas injection improves recovery by swelling & oilviscosity reduction.Displacement efficiency of immiscible gas injection is less thenmiscible gas injection process.

Gas Based EOR ProcessHydrocarbon Miscible Flooding :Hydrocarbon miscible flooding consists of injecting lighthydrocarbons through the reservoir to form a miscible flood. Theprocess recovers crude oil by generating miscibility (in thecondensing and vaporizing gas drive), increasing oil volume byswelling and decreasing the viscosity of oil. Three different methodsof attaining miscibility are used. One method uses about 5% PV slug sof liquefied petroleum gas such as propane, followed by natural gasor gas and water. A second method called enriched (condensing)gas drive , consists of injecting 10 to 20% PV slug of natural gas gthat is enriched with ethane through hexane(C2 to C6) , followed bylean gas and possible water.

Gas Based EOR ProcessOverall displacement EfficiencyE = Es x Ei x EdWhere Es is areal sweep efficiencyEi is invasion efficiency or vertical sweep efficiencyEd is microscopic displacement efficiency which accounts for thetrapping of oil by capillary forces in the pores invaded bydisplacing fluid.

Miscible Gas Flooding(Hydrocarbon Injection)InjectionWellHC GasInjectionfrom Pipelineor RecycleWaterInjectionPumpSeparation andStorage FacilitiesProduction Well4 3 2 11 Oil Zone 2Oil Bank /Miscible Front3HC andWater Zone4 Drive Water

Gas Based EOR ProcessHydrocarbon Miscible Flooding :The enriching components are transferred from gas to the oil. Thethird method, called High pressure (Vaporizing) gas drive, consistsstsof injecting lean gas at high pressure to vaporize C2 to C6components from the crude oil being displaced. Different types of oHC gas displacement are depicted in the next page.LPG Injection

Gas Based EOR ProcessRich Gas InjectionLean Gas Injection

MISCIBLE GAS PROCESS

Miscible Gas Injection: Gandhar GS-12Waterflood Recovery : 36 %HC Miscible Gas Inj. Recovery: : 57 %Gas Injectors: 10 (4,80000 m3/d)Avg Res Pressure: 270kscOil rate / water cut : 777m3/d / 1%

Gas Based EOR ProcessTechnical Screening GuidelinesCrude OilGravity : > 20o APIViscosity : 10ftAverage permeability : > 5mDDepth: > 700 ft( depending upon miscibility pressure)Temperature: < Not critical

Gas Based EOR ProcessLimitations and Facts•The minimum depth is set by the pressure needed to maintainthe generated miscibility.•A A steeply dipping formation is very desirable to permit somegravity stabilization of the displacement.•Viscous fingering results in poor vertical and horizontal sweepefficiency.•Solvent may be trapped and not recovered.•Injected hydrocarbon gas should be available in sufficientquantity.•Recycling of produced gas may reduce the total gas requirement.

Gas Based EOR ProcessCO2 Flooding (Miscible & Immiscible)This process is carried out by injecting large quantities CO2 (15%or more of the hydrocarbon pore volume) into the reservoir.Miscible displacement by carbon dioxide is similar to vaporizinggas drive. The only difference is a wider range of components; C2 Cto C30 are extracted. As a result, CO2 flood process is applicableleto a wider range of reservoirs at lower miscibility pressure thanthose for the vaporizing gas drive. CO2 is generally soluble incrude oils at reservoir pressures and temperatures. It swells thenet volume of oil and reduces its viscosity even before miscibilityityis achieved by vaporizing gas drive mechanism. As miscibility isapproached as a result of multiple contacts both the oil phaseand the CO2 phase can flow together because of lower interfacialtension. CO2 can be recycled by extracting it from the crude atthe surface.

Gas Based EOR ProcessCO2 Flooding (Miscible & Immiscible)

Gas Based EOR ProcessAn oil of less than 25o API is usually considered unfavorable for fCO2injection.A minimum oil saturation of 25-30% is required for this process.A large gas cap is usually an unfavorable factor.If reservoir pressure is considerably below miscibility pressure, , largevolumes of CO2 will be needed to obtain the miscibility.A highly fractured reservoir is usually considered unfavorablebecause the fractures provide a conduit from injection to producingwell.An adequate and reliable source of CO2 at reasonable cost is aprimary requisite.The ratio of vertical to horizontal permeability is critical parameteras it controls the rate at which the CO2 can segregate.Relatively thin permeable zones in the reservoir are technicallyadvantageous because they diminish the tendency of gravityoverride, but the thicker zone have an oil volume advantage.

Gas Based EOR ProcessCO2 Flooding (Miscible & Immiscible)Technical Screening GuidelinesCrude OilGravity: > 20o APIViscosity : < 12 cPComposition: High percentages of intermediate hydrocarbons (C5-C20)C20)ReservoirType of formation: Sand stone or carbonate with minimum of fractures, highpermeability streaks preferredNet Thickness : > Relatively thin unless formation is steeply dipping.Average permeability : > 2mD (provided sufficient injection rate can bemaintained)Depth: > Deep enough to allow high enough pressure, pressure required ed forachieving miscibility.Temperature: < Not critical. However pressure requiredincreases with temperature.e.

9 8 1 6 5

Gas Based EOR ProcessCO2 Flooding (Miscible & Immiscible)Limitations•Source of CO2 can act as a Limitation for this process to beapplied.•Very low viscosity of CO2 results in poor mobility control.•Early breakthrough of CO2 causes several problems.•CO2 gets dissolved into formation water making it acidic. Thiscauses corrosion of the tubulars in the well bore.•Repress rising of CO2 for recycling.•A A high requirement of CO2 per incremental barrel of oil produced.Safety hazards.

Gas Based EOR ProcessNitrogen Gas Flooding (Miscible and Immiscible)Nitrogen gas flooding oil recovery method uses the inexpensivenon hydrocarbon gas nitrogen to displace oil in system whichmight be miscible or immiscible depending upon the pressureand oil composition. Because of their low cost, large volumes ofthese gases may be injected. The process recover oil byvaporizing the lighter component of the crude oil and generatingmiscibility if the pressure is high enough, providing a gas drivewhere a significant portion of the reservoir volume is filled withlow cost gases. Higher miscibility pressure required compared toall other gases.

Gas Based EOR ProcessNitrogen Gas Flooding (Miscible and Immiscible)Technical Screening GuidelinesCrude OilGravity: > 30o API (miscible), >15o API (Immiscible)Viscosity : < 3 cP (Miscible) , Relatively thin unless formation is steeply dipping.Average permeability : > 5mD (Miscible), >15mD (Immiscible)Depth: > Deep enough to allow high enough pressure, pressurerequired for achieving miscibility.Temperature: < Not critical. However pressure requiredincreases with temperature.e.

Gas Based EOR ProcessNitrogen Gas Flooding (Miscible and Immiscible)Limitations•A good miscibility can be achieved with light oils at high pressureonly. Therefore deep reservoirs are needed.•A steeply dipping reservoir is desired to permit gravitystabilization of the displacement.•Viscous fingering may result in poor vertical and horizontal sweepefficiency.•The non-hydrocarbon gases must be separated from the saleableproduced gases.

Gas Based EOR ProcessWater And Gas injection (WAG):-•Combines improved displacement efficiency of gas flooding withimproved macroscopic sweep by water injection.•Recovery of oil by exploiting the segregation of gas to the top andaccumulation of water towards the bottom.

Gas Based EOR ProcessWater And Gas injection (WAG):-The WAG survey conducted by Hadlow reported an ultimate recovery ofabout 8–14% 8OOIP, based on simulation and pilot tests. However, the morerecent survey of 2001 by Christensen et al. shows that the averageincrease in oil recovery was only 5 – 10%. The survey encompassed 59projects. The popularity of the WAG process is evident from the increasingnumber of projects and many successful field wide applications

Gas Based EOR ProcessClassification of WAG Process:-Miscible WAG is same as that of miscible gas injection exceptthat it is altered with water to improve its displacement efficiency.ency.In Miscible gas injection process mass transfer occurs between oiland gas and forms a transition zone to displace the oil effectively.Immisible gas injection improves recovery by swelling and oilviscosity reduction. Here gas is immiscible with the oil.‘Hybrid-WAG’ process patented by UNOCAL, and the ‘DUWAG’process of Shell. These patented processes namely; Hybrid-WAGand DUWAG were developed to optimize recoveries from gasinjection processes wherein a large slug of CO2 is injected followedowedby 1:1 WAG.

Gas Based EOR ProcessTapering is the decrease in gas-toto-water ratio as the floodprogresses. This is generally done to control the gas mobility and achanneling as well as to prevent early breakthrough of the gas. Thisstep is important especially when the injected gas is expensiveand needs recycling. Tapering is generally done in most of the CO2 Cand hydrocarbon floods and prevailed even in the earliest WAGflood trials.

Gas Based EOR ProcessPerformance of different methods of oil recovery

Gas Based EOR ProcessPerformance of different methods of oil recovery

Gas Based EOR ProcessSimultaneous water and gas injection (SWAG):SWAG is similar to WAG except that water and gas injectiontakes place simultaneously. SWAG experiments are performedwith different SWAG (gas-water) ratios. The water and gas areobserved to flow simultaneously in the pores with watercreeping on the pore walls and gas moving in the porecenters. It is observed that residual oil ganglia are sandwichedbetween gas-oil and water-oil menisci from oppositedirections and the oil was squeezed out as a result of veryconductive oil layers. It is also noted that recovery due toSWAG was Independent of the SWAG ratio.

Gas Based EOR Process

Gas Based EOR ProcessDisplacement Efficiency by SWAG in KALOL- IX+XDisplacement Efficiency, %HCPV70.0060.0050.0040.0030.0020.0010.000.000.000 0.500 1.000 1.500 2.000PV Injected, ccDisplacement by Water Flood Displacement by SWAG

Gas Based EOR ProcessSaturation of Oil,Water & Gas During SWAG Injection and Displacement Efficiency%So,Sw,Sg & Displacement Efficiency7060504030201000 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2PV Injected, ccSoswSgDispl.Eff

INCORRECT APPLICATIONS:Miscible Flooding• Of more than 100 floods, only a dozen havebeen commercially successful; failuresbecause of lack of attention to gravitysegregation, and frontal stability• Incompatible oil and drive fluid compositionsin multi-contact miscibility• Wrong choice of the drive gas (nitrogen?inert gas?)• Optimistic simulations (poor control ofdiffusivity); unscaled experiments

Microbial EOR process is an in-situ process which is more advantageousthan injection approach. Product formed to aid in oil release arebiological organism, they will gone through biodegradationMicrobial EOR Processfulfilling the demand ofenergy it is necessary topetroleum energy sourcereservoir. For this we cando enhanced oil recoveryIn present energyscenario overall worldhave need of cheaperenergy source. Forutilize optimumpresent in subsurfaceusing microbes.

Microbial EOR ProcessMicrobial Enhanced Oil Recovery (MEOR) relies on microbes to fermenthydrocarbons and produce a by–product that is useful in the recovery ofoil. MEOR functions by channeling oil through preferred pathways in thereservoir rock by closing/ plugging off small channels and forcing the oil tomigrate through the larger pore spaces. Nutrients such as sugars,phosphates, or nitrates frequently must be injected to stimulate thegrowth of the microbes and aid their performance. The microbes generatesurfactants and carbon dioxide that help to displace the oil.Microbial growth can be either within the oil reservoir (in situ) or on thesurface where the byproducts from microbes grown in vats are selectivelyremoved from the nutrient media and then injected into the reservoir. Forin situ MEOR processes, the microorganisms must not only survive in thereservoir environment, but must also produce the chemicals necessary foroil mobilization.

Microbial EOR ProcessMEOR has two distinct advantages:(1)Microbes do not consume large amountsof energy(2) The use of microbes is not dependenton the price of crude oil, as comparedto many of the other EOR processes.In some reservoirs, beneficial microbes are indigenous and only neednutrients to stimulate growth. Because microbial growth occurs atexponential rates, it should be possible to produce large amounts ofuseful products rapidly from inexpensive and/or renewable resources.Thus, MEOR has the potential to be more cost-effective than other EORprocesses. Studies have shown that several microbially-produced biosurfactantscompare very favorably with chemically synthesizedsurfactants. The ability to produce effective surfactants at a low pricemay make it possible to recover substantial amounts of residual oil.

THE TECHNIQUE INVOLVES:‣injection of TBHA microbialconsortium along with nutrients inthe reservoir‣incubation of the Consortium.growth and production of usefulmetabolites (acids, biosurfactants.‣Increase mobility of crude oiltowards wellbore.‣currently applied in huff and puffmode.‣target stripper well/low producer

Microbial EOR Process

MICROBIAL PRODUCTS AND THEIR ACTIONAcidsImproving• porosity• permeabilityGases(CO 2 , CH 4 )• Increase in pore pressure.• Oil swelling• Viscosity reductionSolvents• Dissolving of oilSurfactants• Lowering of interfacial tensionPolymers• Mobility control

IDENTIFIED MICROBES FOR MEORPROCESS• Two consortium IRSM-1/IRSM-2 active upto 65°C• S-2 consortium active upto 90°C

Micro Photo Graph of Consortium S-2

Well Selection Criteria forapplication of MEORPARAMETERType of formationDepthRECOMMENDED RANGESand stone (preferably)Less than 8000 ft. (2400 Mts.)Temperature < 90°CPressure, Kg/cm 2 < 300 Kg/cm 2Reservoir rock permeability>50 md°API gravity of crude oil > 20Viscosity of oil 25 %Salinity as NaCl

Other parameters which areconsidered• Asphaltene, Resins & Wax content of crude• CBL/VDL• Proximity of Fluid Content• GOR• Injectivity• Mode of Lift• Withdrawal rate of well• Rock Mineralogy

Treatment DesignConsists of three steps• Pre-flush• Main Biological solution• After flushInfrastructure facilities required• Four epoxy coated tanks• Blending unit• Pumping unit• Filtration unit

Schematic flow diagram of MEOR JobTANK-1 TANK-2 TANK-3 TANK-450 m 3 50 m 3 50 m 3 50 m 3 FILTERATIONUNITBLENDING UNITWSSPUMPING UNITWSS

100.090.080.070.060.050.040.030.020.010.00.0MEOR PERFORMANCE OF SOB #72 (SS-1B)10.09.08.07.06.05.04.03.02.01.00.0Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02Dec-02Jan-03Feb-03Mar-03Apr-03May-03Jun-03Jul-03Aug-03Sep-03Oct-03Nov-03Dec-03Jan-04Feb-04Mar-04PeriodWater cut % Liquid rate m3/d Oil rate m3/dWater Cut (%)MEOR JOB ON 01.07.02Average Qo & Ql (m3/d)

1009080706050403020100MEOR PERFORMANCE WELL No. SOB # 36 (SS-1B)3530252015105017.01.0419.01.0422.01.0419.06.0421.06.0424.06.0426.06.0428.06.0430.06.0402.07.0404.07.0406.07.0408.07.0410.07.0412.07.0414.07.0416.07.0418.07.07DateWater cut(%)MEOR JOB ON 22-01-04Liquid Rate/Oil Rate (m3/day)Water Cut Liquid Rate Oil RatePRE MEOR JOB

403530Average Qo & Ql (m3/d)1009080706050403020100MEOR PERFORMANCE OF WELL SOB# 100 (SS-1B)25201-Oct-031-Jan-021-Feb-021-Mar-021-Apr-021-May-021-Jun-021-Jul-021-Aug-021-Sep-021-Oct-021-Nov-021-Dec-021-Jan-031-Feb-031-Mar-031-Apr-031-May-031-Jun-031-Jul-031-Sep-031-Aug-03MEOR JOBON 20.06.2002Period151050W/C % Ql (m3/d) Qo (m3/d)Water Cut (%)

1009080706050403020100MEOR PERFORMANCE OF WELL NK # 208 (KS- 1A)353025201510504-Oct-0211-Oct-0231-Oct-0211-Nov-0218-Nov-0225-Nov-022-Dec-029-Dec-0216-Dec-0223-Dec-0230-Dec-026-Jan-0313-Jan-0320-Jan-0327-Jan-034-Feb-0311-Feb-0318-Feb-0325-Feb-034-Mar-0311-Mar-0318-Mar-0325-Mar-0331-Mar-03PeriodW/C % QL (m3/d) qo(m3/d)Water Cut (%)MEOR JOB ON 11.10.2002INCUBATION PERIOD

MEOR JOB PERFORMANCE AT KALOL #104 (XII)201816141230-Apr-0431-Mar-0429-Feb-0431-Jan-0431-Dec-0330-Nov-0331-Oct-0330-Sep-0331-Aug-0331-Jul-0330-Jun-0331-May-0330-Apr-0331-Mar-0328-Feb-0331-Jan-0331-Dec-0230-Nov-0231-Oct-0230-Sep-0231-Aug-0231-Jul-0230-Jun-0231-May-0230-Apr-0231-Mar-0228-Feb-0231-Jan-0231-Dec-0130-Nov-0131-Oct-01100908070605040302010010Mode changed to SRP86420W/C % QL M3/day QO,m3/dDATEWater Cut %Liquid rate / Oil rate m3/d

403530Liquid rate / Oil rate m3/d1002590208015706050104030205100PERFORMANCE OF MEOR JOB IN WELL KALOL#72 (XII)05.06.0230.06.0217.08.0203.09.0218.10.0225.11.0209.02.0320.03.0314.04.0330.06.0331.10.0331.12.0331.01.0417.02.0410.03.0431.03.04PERIODW/C% Ql m3/day Qo0Water Cut %INCUBATION PERIODREPEAT MEOR JOB ON 11.12.2003POST MEOR PERFORMANCEPow er supplychanged toindusrtial feederon 17.02.04PRE MEOR STATUSINCUBATION PERIODMEOR JOB ON 10.06.2002

PERFORMANCE OF MEOR JOB IN KALOL # 56 (IV)20POST MEOR STATUS18Liquid rate, Oil rate m3/d161412MEOR JOBON 15.3.20021031.01.0431.10.0331.05.0309.04.0319.03.0316.02.0329.01.0326.11.0209.11.0211.10.0228.09.0212.09.0227.08.0212.08.0217.07.0218.06.0225.05.0220.04.0215.03.0205.03.021009080706050403020100MODE OF LIFT CHANGEDGL TO SRP ON 05.01.20038INCUBATION PERIOD6420PERIODW/C % Ql- m3/d QoWater Cut %

COST OF MEOR OILMEOR job cost with• Low temp. consortium :- US $ 3 per barrel(IRS M-1 & IRS M-2)• High temp. consortium :- US 3$ to 6$ per barrel(S-2 consortium)Pay out period for• Low temp. consortium :- 2 months• High temp. consortium :- 3 months

Conclusions‣Future oil increasingly dependant on IOR/EOR‣Strong cost pressures‣Applications of modern technology (multilaterals,smart wells)‣Efficient reservoir management required‣Look for innovative ways continuing(research)‣Fiscal incentives & environmental pressuresmay steer direction

Conclusions•The forces holding back the oil in the porous rock are theinterfacial tension between oil and water, and the viscosity ofthe crude oil.• EOR has been utilized to overcome or to minimize thephysical and geological effects to mobilize additional oil.• It’s usually applied after primary and secondary recovery.• There is no universal method to be applied in any reservoir•Certain reservoir and fluid parameters have to be consideredby selecting any EOR methods• Improvement of EOR can be achieved in conjunction withother advanced technologies, such as horizontal drilling etc…