Mar-06

Oct-06

Apr-07

Nov-07

Jun-0

8

Dec-08

Jul-0

9

Jan-10

Aug-10

Feb-11

Sep-11

Apr-12

Oct-12

A Simulation Study of Simultaneous Acid Gas EOR and CO2 Storage at Apache’s Zama F Pool EERC

Energy & Environmental Research Center®Dayanand Saini, Damion J. Knudsen, James A. Sorensen, Charles D. Gorecki, Edward N. Steadman, and John A. Harju, Energy & Environmental Research Center, Grand Forks, North Dakota Putting Research into Practice

Abstract Petrophysics Predictive Simulation Results (continued)

The Plains CO2 Reduction (PCOR) Partnership, led by the Energy & Low-Permeability Rock Type Facies Zama Site Input Output Low-Permeability Rocks (oil/water rel. perm.) Low-Permeability Rocks (gas/oil rel. perm.)Environmental Research Center, is working with Apache Canada Ltd. 1 1 1 1

0.9 0.9 0.9 0.9to validate the stored volumes of CO2 in the F pool of the Zama oil field Krg (initial)

GR

NPH

I

PHO

B

PEF

DT

RT RXO

Faci

es

PHE

Kh Kv

Perf

s

Swn

Son

Sw So

Kro

w

Kro

w

Krow (initial)0.8 0.8 0.8 0.8Krog (initial)0.7 Krw (initial) 0.7 0.7 History Prediction0.7Krg (history matched)in northwestern Alberta, Canada. Since December 2006, acid gas (70%

carbon dioxide [CO2] + 30% hydrogen sulfide [H2S]), captured at a nearby

Krow (history matched)0.6 0.6 0.6 0.6Krog (history matched) 0.5 0.5

Kro

g

Kro

g

Krw

KrgKrw (history matched)0.5 0.5

0.4 0.4 0.4 0.4 0.3 0.3 0.3 0.3

0.2 0.2 0.2gas-processing plant, has been injected for simultaneous enhanced oil 0.2 0.1 0.1 0.1 0 0

0.1 0

0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1recovery (EOR) and CO2 storage purposes. 0

Sl, fractionSw, fraction  To aid in the monitoring, verification, and accounting program, a detailed High-Permeability Rock Type Facies static geologic model of this heterogeneous pinnacle reef carbonate High-Permeability Rocks (oil/water rel. perm.) High-Permeability Rocks (gas/oil rel. perm.)

1 1 1 1 0.9 0.9 0.9 Krg (initial)reservoir was constructed. A combination of object modeling and 0.8

0.9 PredictedOilRecovery,FieldOil,andWaterRates(existingEORconfiguration) AmountsandRatesofInjectedandProducedCO2(existingEORconfiguration)Krow (initial) 0.8 0.8 0.8Krog (initial) 0.7multiple-point statistics (MPS) workflow was used for spatial distribution of different properties extracted from 0.7 Krw (initial) 0.7 0.7 Krg (history matched)

0.6 0.6Krow (history matched) 0.6 0.6Krog (history matched)

Krw

Krg 0.50.50.5 Krw (historty matched) 0.5available borehole image logs and other well log data. Additional CO2 Storage Capacity Gain Through Water Extraction0.4 0.4 0.4 0.4

0.3 0.3 0.3 0.3

  0.2 0.2 0.2 0.2 OnewaterextractionwellcompletedinbottomwaterzonewithexistingEORconfiguration(onegasinjectionandtwooil0.1 0.1 0.1 0 0 0 0One of the equiprobable static realizations was chosen for performing history matching for model validation.

0.1

0 0.2 0.4 0.6 0.8 1

The history-matching results were then used for further conditioning of a static geologic model that includes better representation of underlying aquifer and internal reservoir microfacies. The history-matching results indicate a residual oil saturation ranging from 40% to 60% in regions with good permeability. These areas will be targeted while evaluating the future incremental oil recovery potential for this reservoir. The reef structure below the oil–water contact (OWC) was also modeled to explore the possibility of additional storage capacity gain in the underlying aquifer. With over 700 pinnacle reef structures in the Zama subbasin, a careful selection of pinnacle structures similar to the F Pool may provide significant storage capacity gain

productionwells).0 0.2 0.4 0.6 0.8 1 Sw, fraction Sl, fraction

History Matching • HistorymatchingwasperformedwithP10OOIP(originaloilinplace)(4.3MMstb)staticmodelrealization.

• AcombinationofobjectmodelingandMPSworkflowwasusedforspatialdistributionofreefandnonreeffaciesinthestaticmodel.

• Theadjustedparametersincludeverticalpermeability,wellproductivityindices,andvolumemodifierforreefstructurebelowtheOilSaturationandTotalGasperUnitArea(2012-06-01),EORwithBottom OilSaturationandTotalGasperUnitArea(2032-06-01),EORwithBottomOWC,alongwithanumericalaquifieratthebottomofthestructure.through water extraction. WaterExtraction WaterExtraction

Predictive Simualtion Results (20 Years of EOR Operations)

Variable Existing EOR Configuration Existing EOR Configuration with Water Extraction FromSimultaneous CO2 EOR and Storage Water Zone Below OWC)

Minimum BHP Minimum BHP Minimum BHP Constraints History Prediction Constraint = Constraint = of 300 psi and 2100 psi at   300 psi at Production 2100 psi at Production Production Wells and Water

Wells Wells Extaction Well, RespectivelyCumulative Oil and Injected CO2 Zama F Pool Incremental Oil Recovery (%) 16.2 12.6 22.1

Cumulative Oil Injection/Production 20 20 2080,000 160,000 Duration, YearsProduction (stb)

70,000 Cumulative Acid Gas Injection (tons)

140,000 Cumulative CO2 Injeted,

Cum

ulat

ive

CO2 I

njec

tion,

tons 16.07 10.09 12.70Million Tons

Cumulative CO2 Produced, Million TonsCumulative CO260,000 120,000

Injection (tons) 50,000 100,000

15.84 9.79 11.35

Cum

ulat

ive

Oil,

stb

Net CO2 Stored, Million Tons 0.24 0.30 1.35TheSequentialGaussiansimulationalgorithmwasusetopopulatereservoirpropertiesinthemodel.

Oil Produced, MMstb 0.70 0.55 0.9540,000 80,000 PredictedOilRecovery,FieldOil,andRate(existingEOR AmountsandRatesofInjectedandProducedCO2(existingNet configurationwithwaterextraction) EORconfigurationwithwaterextraction)CO2

30,000 Stored 60,000

20,000 40,000

10,000 20,000

Water Produced, MMstb 3.07 1.17 7.86

Summary0 0

A detailed static geologic model was constructed using MPS algorithm and object-modeling workflow for performingDate

compositional simulations (history matching and prediction) of simultaneous acid gas EOR and CO2 storage in this complex oil­(Burke, 2009)

PVT (pressure, volume, and temperature) Modeling • An11-componentPeng–Robinsonequationofstate(EOS)PVTmodelwasdevelopedtouseincompositionalsimulation.

• Simulatedminimummiscibilitypressures(MMPs)were4.1%higherand5.5%lowerthanthemeasuredvaluesforpureCO2andacidgas(80%CO2+20%H2S)mixture,respectively.

Dif. Lib. Calc. Regression Summary Dif. Lib. Calc. Regression Summary 350 1.25 5.00

300 4.50

1.20

HistoryMatchResultsforCumulativeOil, ActualandSimulatedWellBottomHole HistoryMatchResultsforCumulativeWater,andGasVolumes Pressures(8HPs) VolumesofInjectedAcidGasandWater

Predictive Simulation Results Existing EOR Configuration (one gas injection and two production wells) TwoscenarioswithminimumwellBHP(bottomholepressure)constraintof300and2100psiatproductionwells.

producing carbonate pinnacle reef structure.

Good agreement between historical data ( cumulative production and gas injection volumes and pressure) and simulated results was obtained by reconditioning of both the static and dynamic models.

Predictive simulation results suggest that under the current EOR configuration, an ultimate recovery of 44% (16% incremental recovery) can be achieved in the next 20 years while storing 0.25 million tons of CO2 in the reservoir.

A significant increase in the ultimate CO2 storage capacity (from 0.25 million tons to 1.35 million tons, i.e., an increase of 540%) can be achieved in the next 20 years if a water extraction well away from existing oil producers and gas injection wells is used to extract water from the bottom aquifer. In controlled water extraction (minimum BHP constraints of 2100 psi at water injector and 300 psi at oil producers), incremental oil recovery of 21% was observed, which is 5% more compared to the case with no water extraction. These gains in oil recovery and CO2 storage capacity may be attributed to attainment of better sweep by allowing

Rela

tive

Oil

Volu

me,

rb/s

tb 4.00 injection gas movement to contact residual oil remaining in unswept regions of the reservoir. Oil/Water

3.50 Contact

Gas

-Oil

Rati

o, s

cf/s

tb 250

200 1.15

150 1.10 O

il V

isco

sity

, cp)

(OWC) With over 700 pinnacle reef structures in the Zama subbasin, similar studies will be conducted for several other oil-producing3.00

pinnacle reefs to evaluate their EOR and CO2 storage capacity potential. 2.50

Final Oil Visc. Init. Oil Visc. Exp. Oil Visc.

2.00 Final GOR Init. GOR Exp. GOR 1.05

InitialOilSaturation InitialGasSaturation TotalGasperUnitArea(ft)attheStartof50 1.50Final ROV Init. ROV Exp. ROV GasInjection(Dec-2006)

1.00 References1.00 0 1000 2000 3000 4000 5000 60000 1000 2000 3000 4000 5000 6000

Pressure, psia Pressure, psia 1. Asghari, K., 2005, Zama Keg River F pool field-scale CO2 ­flood simulation study: Report prepared for Apache Canada Ltd., March.

2. Buchkuehle, M., Haug, K., Michael, K., and Berhane, M., 2007, Alberta Energy and Utilities Board, Alberta Geological Survey, regional-scale geology and hydrogeology ofStatic Modeling Workflow acid-gas enhanced oil recovery in the Zama oil field in Northwestern Alberta, Canada, June.

3. Burke, L., 2009, PCOR Project Apache Zama F pool acid gas EOR & CO2 storage: Report prepared by RPS Energy Canada for the Energy & Environmental Research Center, September.Step 1. Micro-CT scan Step 2. QEMSCAN

(nm-to-µm scale) (nm-to-mm scale) Dolomite

Porosity Matrix Background Calcite Others Quartz HiBSE

4. Knudsen, D.J., Saini, D., Gorecki, C.D., Peck, W.D., Sorensen,GasSaturationattheEndofHistoryMatch

Per

mea

ble

Per

mea

ble

Tig

ht

Faci

esFa

cies

Fa

cies

OilSaturationattheEndofHistoryMatchPeriod(2012-06-01) TotalGasPerUnitArea(ft)attheEndof J.A., Steadman, E.N., and Harju, J.A., 2012, Using multiple­Period(2012-06-01) HistoryMatchPeriod(2012-06-01) point statistics for conditioning a Zama pinnacle reef facies

model to production history: Poster presented at American

Association of Petroleum Geologists Annual Conference and Halite Exhibition, Long Beach, California, April. Pore

Acknowlegments The Authors thank the U.S. Department of Energy (DOE) for providing financial support for this study. Special thanks to Apache Canada Ltd. for providing the necessary data for

Anhydrite Wackestone/Packstone Grainstone/Floatstone/Rudstone

geologic and reservoir modeling. Many thanks to Megan Step 3. Formation Microimaging Step 4. Form Reservoir Model Grove and the EERC’s Graphics and Editing staff for their help Log Processing and Petrophyscics (10s of m-to-km scale) with poster preparation.

(cm-to-m scale) OilSaturation(2032-06-01)1 GasSaturation(2032-06-01)1 TotalGasperUnitArea(ft)1

1After20yearsofEORoperations,MinimumBHPconstraintof300psiatproductionwell.

© 2012 University of North Dakota Energy & Environmental Research CenterDOE NETL Carbon Storage R&D Project Review Meeting – August 2012

0

100