The Wyoming Enhanced Oil Recovery Institute’s

2008 Wyoming EOR/IOR Conference

“CO2 EOR, Reservoir Sweep and CO2 Storage”

Steve Melzer

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CO2 EOR, Reservoir Sweep and CO2 Storage

• Background and Growth of CO2 EOR

• The Concept of and Experience with Reservoir Sweep

• Incidental Storage of CO2 in EOR

• The Converging Worlds of CO2 EOR and CO2 Storage

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GROWTH OF PERMIAN BASIN & WORLDWIDE CO2 PROJECTS

1984 - 2008

0

20

40

60

80

100

120

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

YEAR

NO. O

F PR

OJE

CTS

WW Projects PB Projects

Melzer Consulting - 5/08* Ref: O&GJ Biennial EOR Editions & UTPB

BACKGROUND (OF CO2 EOR PROJECT GROWTH*)

* Includes Only CO2 Miscible Floods

…..and Growth Even with Languishing Oil Pricing

GROWTH OF PERMIAN BASIN & WORLDWIDE CO2 PROJECTS1984 - 2004

0

20

40

60

80

1988

1990

1992

1994

1996

1998

2000

YEAR

NO

. OF

PRO

JEC

TS

WW Projects PB Projects

Melzer Consulting - 8/04

WTI Posted Oil Prices - 1988-2000

$0

$10

$20

$30

$40

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

YEAR

OIL

PR

ICES

IN $

/bbl Average

Price = $18.80 (U.S.)

Average Growth > 2 Projects/Yr

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BACKGROUND (OF CO2 EOR PRODUCTION GROWTH*)

WW & PERMIAN BASIN CO2 EOR PRODUCTION1986 - 2008

0

50

100

150

200

250

30019

86

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

YEAR

CO

2 EO

R P

RO

DU

CTI

ON

- kb

opd

Permian Basin Worldwide

* Ref: O&GJ Biennial EOR Editions & UTPBP t I d t Alli

Melzer Consulting - 5/08

* Includes both CO2 Miscible & Immiscible Floods

HOW BIG IS THE CO2 EOR BUSINESS?

NOV 2005

* Source: Oil & Gas Journal (Mar ’08) and CO2 Flooding Conference (2007)

Annual Production Rev Figures**

U.S. $8.0 billion*

PB $5.3 billion*

* @ $80/bbl

** Does not take into account the NGLs produced from the recycle volumes6

ENHANCED OIL RECOVERY AND CO2 EOR

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BEYOND PRIMARY (AND WATERFLOODS)

• IMPROVE SWEEP– INFILL DRILLING– PATTERN MODIFICATION– AUGMENTED WATERFLOODING (POLYMER, ETC)– LOW SALINITY WATERFLOODING

• REDUCE WATERFLOOD RESIDUAL– THERMAL (CYCLIC STEAM, STEAM DRIVE, SAGD, FIRE)– CHEMICAL (ALKALINE/POLYMER/SURFACTANT)– MISCIBLE GAS INJECTION

• HYDROCARBON MISCIBLE FLOODING (HCMF)• NITROGEN• CO2

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EOR METHODS

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TODAY’S VIEW THE PRODUCING LIFE OF A RESERVOIR

‘IN-FILL’ DRILLING

* Average for San Andres Dolomites (PB)

The Concept of and Experience with Reservoir Sweep

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WATERFLOODING & SWEEP EFFICIENCY

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SWEEP EFFICIENCY

WF Swept Area

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WATERFLOOD RECOVERY

R = Es * (SOi – SORwf ) / SOiSOi = 0.80SORwf = 0.35Es = 0.70

R = .70 * (.80 – .35) / 0.80 = 0.39ROIP (SWEPT REGION ) = 0.70 * (0.45) / 0.80 = 0.39ROIP (UNSWEPT REGION ) = 0.30 * (0.80) / 0.80 = 0.30ROIP (TOTAL) = 0.69

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SWEEP EFFICIENCY

CO2 Swept Area

WF Swept Area

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CO2 FLOOD RECOVERY CALCULATIONS MISCIBLE PROJECTS

R = Et * (SOS – SORM )where: R = Recovery FactorSOS = Oil Saturation at Flood StartSORM = Miscible Residual Oil Saturation

Es > Et

R = Et * (SORWF – SORM ) where: SORWF = Waterflood Residual Oil Saturation

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PRIMARY + WATERFLOOD AND CO2 SWEEP EFFICIENCY

• PRIMARY + WATERFLOOD RECOVERYR = E(p+s) * (SOi – SORwf )E(p+s) = R / (SOi – SORwf )

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CO2 MISCIBLE FLOODING

EXPECTED RECOVERY

R = ET * (SORwf - SORm ) / SOiSORwf = 0.38 SOi = 0.85SORm = 0.10 ET = 0.35

R = .35 * (.38 – .10) / 0.85 = 0.115

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PHASE I RESERVOIR SCREENING RULES OF THUMB: CO2 MISCIBLE INJECTION

• PERCENT OF OOIP8 TO 18 (12)

• RATIO – TERTIARY / (P + S)20 TO 35 (25)

• SWEEP EFFICIENCY25 TO 50 (35)

• RATIO – Et / E(P+S)50 TO 60 (50)

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RULE OF THUMB EXAMPLES (1) EUR FROM CO2 INJECTION

FIELD A FIELD BSWi (% PV) 15.0 23.7SOi (% PV) 85.0 76.3SORwf (% PV) 38.0 26.0(P+S) Target (% PV) 47.0 50.3(P+S) (% OOIP) 41.8 55.2 (P+S) (% PV) 35.5 42.1E(P+S), % 75.6 83.7

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RULE OF THUMB EXAMPLES (2) EUR FROM CO2 INJECTION

FIELD A FIELD BSOi (% PV) 85.0 76.3SORwf (% PV) 38.0 26.0SORm (% PV) 10.0 10.0Tertiary Target (% PV) 28.0 16.0Tertiary, % OOIP 14.6 10.0 Tertiary, (% PV) 12.4 7.6ET 44.3 47.7ET / E(P+S), % 58.6 57.0

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RULE OF THUMB EXAMPLE (3) EUR FROM CO2 INJECTION

TERTIARY SUMMARYFIELD A FIELD B

%OOIP (SORwf ) 38.0 26.0ET 44.3 47.7T / (P+S) 35.4 18.1ET / E(p+s), % 58.6 57.0Tertiary, % OOIP 14.6 10.0

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PRIMARY, WF AND TERTIARY RECOVERY FROM THE W. TX SAN ANDRES EXPERIENCE

BUT BEWARE OF AVERAGES!!

WITH A RANGE OF VALUES OF 8-18%

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CO2 FLOODING: MISCIBILITY

• FIRST CONTACT• DYNAMIC OR MULTIPLE CONTACT• RESIDUAL OIL FOR CO2 FLOODING• IMMISCIBLE CHARACTERISTICS OF CO2

• WHY CO2 ?• OIL RECOVERY FROM CO2 INJECTION

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DEFINITIONS OF MISCIBILITY

• Two fluids are "first-contact miscible" if they form only one phase when mixed in any proportions.

• A process that relies on "Developed" or "Multiple-Contact" miscibility is based on the transfer of components between phases to generate mixtures that avoid the two-phase region. Such processes really involve chromatographic separations of components as phases with different compositions flowing at different rates. Displacement processes may be described as:

– Vaporizing Gas Drives– Condensing Gas Drives– Condensing/Vaporizing Gas Drives

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MISCIBILITY CONCEPTS

CORRELATIONS FOR MINIMUM MISCIBILITY PRESSURE CO2 AND CRUDE OIL MIXTURES

(Selected References)

1. Holm, L.W. and Josendal, V.A. (1974), “Mechanisms of Oil Displacement by Carbon Dioxide,” JPT (Dec 74), pp. 1427-38

2. Holm, L.W. and Josendal, V.A. (1982), “Effect of Oil Composition on Miscible Oil Displacement by Carbon Dioxide,” SPEJ (Feb. 1982), pp. 87-89

3. Yellig, W.F. and Metcalf, R.S. (1980), “Determination and Prediction of CO2 Minimum Miscibility Pressures,” JPT (Jan 1980), pp. 160-168.

4. Johnson, J.P. and Pollin, J.S. (1981), “Measurement and Correlation of CO2 Miscibility Pressures,” SPE paper 9790 presented at the SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, April 5-8, 1981.

5. Alston, R.B., Kokolis, G.P., and James, C.F. (1985), “CO2 Minimum Miscibility Pressure: A Correlation for Impure CO2 Streams and Live Oil Systems,” SPEJ (April 1985), pp. 268-74.

6. Sebastian, H.M., Wenger, R.S., and Renner, T.A.(1985), “Correlation of Minimum Miscibility Pressure for Impure CO2 Streams,” JPT (Nov. 1985). Pp. 2076-82.

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WHY CO2 ?

• MISCIBLE AT LOWER PRESSURES THAN NITROGEN OR METHANE

• CHEAPER AND MORE PLENTIFUL THAN LPG/ENRICHED HYDROCARBON GAS

• DENSITY (IN DENSE PHASE) CLOSER TO RESERVOIR FLUIDS – OIL/WATER

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KEY (MINIMUM) REQUIREMENTS FOR CO2 MISCIBLE PROJECTS

• RESERVOIR CHARACTERISTICS– CARBONATES / SANDSTONES– GRAVITY SEGREGATION– STRATIFICATION/FRACTURES– CONTINUITY – WELL SPACING– POROSITY / PERMEABILITY– RESERVOIR THROUGHPUT (INJECTIVITY)– WATERFLOOD PERFORMANCE

IDEALIZED FLOODING

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Fluid Mobility Issues Can Reduce Recoveries And Increase CO2 Recycling

High Mobility Ratio DisplacementAreal “Breakthrough”

• Initial Radial Flow at Injector, Mobile Oil Bank Develops

• Preferential Flow Paths Encountered, Recovery Diminished

OPTIONS:• WAG Injection Design• Thickening Agents• Selective Injection• Profile Modification

• Cement• Liners

Re: T. Bradley, EOR CM Workshop, Dec 2006

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HETEROGENEITY* IN A VERTICAL SENSE

* Re: T. Bradley, EOR CM Workshop, Dec 2006

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HETEROGENEITY IN A HORIZONTAL (AREAL) SENSE

34

35

Fractured Reservoir Model

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Naturally Fractured Reservoirs

• Can Prove Difficult for Flooding (i.e., “short-circuiting” injector-producer pairs)

• Can be Useful to establish line drive pattern flooding if unidirectional

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Naturally Fractured Reservoirs

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Increased Sweep Efficiency from Line Drive Patterns

5-SPOTS LINE DRIVE

Atypical CO2 Flooding

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IMMISCIBLE CO2 FLOODING

• CO2 Solubility and Oil Swelling– Oil Volume Increase (can be ~50%)– Oil From Dead End Pores– Incremental Oil Below MMP

• Viscosity Reduction (Over that of Water)– Better Injection Rates– Reduces Mobility Ratio– Improves Relative Permeability– Improves Sweep Efficiency

41

CO2 SECONDARY FLOODING

• Poor Waterflood Performance (e.g., Clay Swelling)

• Stratification / Continuity• Poor Water Injectivity• High Connate Water• Viscous Oil• Attic Drive

RULES OF THUMB NOT WELL ESTABLISHED

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Residual Oil Zones aka Transition Zones

Hess’ Seminole Field Gaines County, West Texas

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BALANCING THE PATTERNS

• With CO2 , substantial oil can be trapped because the producing well may become uneconomic before the oil bank from the other injectors arrives. Pattern balancing is difficult and conflicts with other stated goals such as maximizing injection.

• In a waterflood, we were able to live with more unbalanced patterns because of the favorable mobility ratio and the relatively low cost of the water.

• Of course, practical compromises must be made.

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BALANCED INJECTION THE INACHIEVABLE IDEAL (5-SPOT EXAMPLE)

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PATTERN BALANCING ’REAL’ EXAMPLE

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MAINTAINING A CONTINUOUS OPTIMIZATION PROGRAM

Regardless of the detail or the quality of the pre- deployment study and the thoroughness of the plan of operation, performance will indicate changes that will be needed. Opportunities may range from the small and simple to major breakthroughs as the result of new learnings and new technology.

Many companies feel “the plan” is fixed and never have learned this lesson

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MONITORING PROGRAM GOES HAND-IN-HAND WITH THE OPERATING PLAN

• Strong communication between field and office• Pattern injectors and producers in same pay – DA! But…..• Metering and documentation system for injected and produced fluids• Periodic pressure measurements (falloffs and buildups)• Initial and (possibly) followup step-rate tests• Fluid level program for pumping wells• Water quality monitoring• Periodic profile measurements• Pattern balancing program• Program to monitor and adjust WAG ratio and WAG cycles

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TOOLS (1)

• GRAPHICALe.g., DIMENSIONLESS PLOTS CAN ID PROBLEM PATTERNS

51

TOOLS (2)

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TOOLS (3)

• SIMULATORS– SOME COMMERCIAL– SOME PROPRIETARY IN-HOUSE

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CO2 FLOODING RECAP (1)

• PROVEN TO BE TECHNICALLY VIABLE IN MISCIBLE AND IMMISCIBLE RESERVOIR CONDITIONS

• MOST PROVEN OF THE PROCESSES FOR LIGHT OILS

• LOW RELATIVE COST OF CO2 (EXCLUDING TRANSPORTATION - MORE ON THIS LATER)

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CO2 FLOODING RECAP (2)

• REDUCES REMAINING OIL IN PLACE VERY EFFECTIVELY BUT SWEEPS SMALLER VOLUME DUE TO GAS-LIKE VISCOSITY

• A POOR WATERFLOOD (POOR SWEEP EFFICIENCY) WILL MAKE A POOR CO2 FLOOD

• IF PROLIFERATION OF CO2 SOURCES ARE COMING AND REMOVE (TO A DEGREE) THE OBSTACLES OF DEVELOPMENT OF A PIPELINE NETWORK, THIS WILL COMMERCIALIZE THE:– DEVELOPMENT OF LESS EFFICIENT FLOODS– IMPLEMENTATION OF SLOWER RESPONDING FLOODS

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KEY REFERENCES

The CO2 Conference

Week of Dec 8th 2008 with Houston and Midland Venues

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Key Reference Work (1) The Annual CO2 Flooding Conference

• Held Each December in Midland, Texas – Home to 53 Active CO2 Floods

• Concentrates on Actual Case Histories• Includes a CO2 Flood Field Visit• Includes a CO2 Shortcourse• Includes an EOR Carbon Management Workshop • Great Networking Opportunity

Visit: www.spe-pb.org or call 432-552-2430

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Key Reference Work (2)THE CO2 FLOODING CONFERENCE SHORTCOURSES

1. Making Money on CO2 Flooding...Some Innovative Development Concepts for Independents..., May 1995.

2. Is My Field a Candidate for CO2 Flooding?, September 19953. Equipping and Day-to-Day Operations of a CO2 Flood, December 19954. How CO2 Flood Surveillance Helps Assure a Successful EOR Program, May 19964a. CO2 Flood Surveillance and Monitoring, December 20045. How to Put Together a CO2 Flood, December 19966. CO2 Measurements and Metering, December 19977. CO2 Facilities and Plants, December 19988. CO2 Flooding: Sandstones vs. Carbonate Reservoirs, December 19999. Issues for Beginning CO2 Flooders, December 200010. Reservoir Modeling and Simulation for CO2 Flooding, December 200111. Wellbore Management in CO2 Floods, December 200212. Carbon Dioxide Health And Safety, December 200413. CO2 Sourcing for Enhanced Oil Recovery, Dec 2006

(http://www.utpb.edu/ceed/co2/shortcourses.html) or phone 432-552-2430

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Key Reference Work (3)

• Practical Aspects of CO2

Flooding, Society of Petroleum Engineers Monograph Volume 22, 2002

(https://www.spe.org/mbrservices/ShopperProductDetail.cfm?ProdCompanyPa ssed=SPE&ProdCdPassed=SPE%2DPROD%2DMONO022)

Thank you

Questions?