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1 Evaluation of Oil Reservoir Characteristics To Assess North Dakota Carbon Dioxide Miscible Flooding Potential Ralph Nelms Westport Oil and Gas Co. Randy.

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Presentation on theme: "1 Evaluation of Oil Reservoir Characteristics To Assess North Dakota Carbon Dioxide Miscible Flooding Potential Ralph Nelms Westport Oil and Gas Co. Randy."— Presentation transcript:

1 1 Evaluation of Oil Reservoir Characteristics To Assess North Dakota Carbon Dioxide Miscible Flooding Potential Ralph Nelms Westport Oil and Gas Co. Randy Burke North Dakota Geological Survey Westport Oil and Gas Co., L.P. North Dakota Geological Survey Geologic Investigations Number 21

2 2 North Dakota CO 2 Mini-Test Pilot 1981 Gulf Oil Company. Little Knife North Field. Five Acre 5 Spot. Mission Canyon Formation. Recovered 13% of OOIP. MMP 3,100 psi. Gulf Projected Recovery of 8% of OOIP on 160-acre Well Spacing.

3 3 Previous North Dakota CO 2 Studies 1988 and 1990 Basin Electric Cooperative. North Dakota and Montana 26 Fields. 4,467 MMbo In Place. 858 MMbo Produced as of ,038 MMbo Primary + Sec. EUR (~24% OOIP) 3,549 MMbo Remaining In Place 232 MMbo Potential CO 2 Flooding Recoverable. (5.2% of OOIP)

4 4 CANADA N.D.M.T. CO 2 PIPELINE Dakota Gasification Co. CO 2 Pipeline Location

5 5 CO 2 Screening Methodology Empirical reservoir characteristics. Analog dimensionless models (Shell Morgan Kinder). Preliminary reservoir simulation studies (IFLO). PVT tests, core analysis and core floods. Advanced reservoir simulation studies (ECLIPSE,GEM, VIP) Preliminary economic analysis. Field pilot. Large scale simulation and project economics. Full scale development.

6 6 Favorable Reservoir Characteristics for Empirical Screening Reservoirs with good waterflood response are best Candidate for CO 2. 20% OOIP< Recovery Factor <50% OOIP. Depth >2500 ft to reach MMP. Oil Gravity >27 Degrees API. Oil Viscosity <10 cp. Porosity >12%. Permeability >10 md.

7 7 Quick Rules of Thumb Recovery factor using miscible CO 2 is 8% -11% OOIP. Immiscible CO 2 50% of miscible. MMP equals initial bubble point pressure. CO 2 requirement is 7-8 Mcf/bo plus 3-5 Mcf/bo recycle. Water injection required to fill gas voidage and increase reservoir pressure to original BHP. WAG is alternative but 10 Mcf/bo still required. Top down CO 2 injection alternative is effective but requires more capital investment for higher CO 2 volume.

8 8 Unfavorable Reservoir Characteristics for Empirical Screening High concentrations of vertical fractures. Very high, or very low, permeability. (Vertical segregation or fracture channeling) Thick reservoirs with no layered horizontal permeability barriers. Reservoirs with poor connectivity. Well spacing >80 acres. Poor material balance during water flood. (High water loss out of zone, water influx or high water cut during primary production)

9 9 U.S. Active CO 2 Floods Texas 48 (26 Succ, 8 TETT, 13 Prom, 1 Fail) Wyoming 5 (5 Success) Oklahoma 4 (2 Success, 1 TETT, 1 Promising.) Utah 2 (1 Success, 1 Promising) Mississippi 2 (1 Success, 1 Promising) Michigan 2 (1 Success, 1 TETT) New Mexico 2 (1 Success, 1 Promising) Colorado 1 (1 Success)__________________ Total 66 (38 Success, 10 TETT, 17 Prom.) * First CO 2 Flood SACROC Jan 1972

10 10 Summary of US CO 2 Active Floods (CEED 2002) Total Active CO 2 Floods = 66 Total Successful = 38 Total Successful Carbonates = 29 Total Successful Sandstones = 9 Of 29 Successful Carbonate Units, 18 are in San Andres Dolomite.

11 11 Reservoir Characteristics of 29 Successful Carbonate CO 2 Floods 2002 US Average North Dakota Madison Porosity 11% (7%-13.5%) 10.9% Permeability 9 Md (1.5-62) 10.2 Md Depth 5,281 feet ( ) 7,500 feet API 33 degrees (28-41) 38.7 degrees BHT 108 degrees F (86-134) 201 degrees F Viscosity 1.52 cp (0.5 –2.6) 1.54 cp So at start of CO 2 flood = 55% (35%-89%)

12 12 Reservoir Parameters of Carbonate CO 2 Floods Well Spacing for 38 Successful CO 2 Floods: 1 Field at 130 acres 2 Fields at 75 acres 2 Fields at 50 acres 32 Fields < 40 acres 38 Well average was 27.6 acres

13 13

14 14 Favorable Reservoir Characteristics for North Dakota Carbonate Reservoirs MMP is Easily Achievable Depth, API Gravity and BHT all Favorable for CO 2 Flooding. Porosity, Permeability and So are all within Range of other Successful Carbonate Reservoirs. H 2 S in Sour Crude in not a constraint. Deeper Reservoirs offset Higher BHT for MMP

15 15 Unfavorable North Dakota Reservoir Characteristics Large Well Spacing averages 160 acres. Many Reservoirs are Vertically Fractured. Depth Increases Well Costs for Infill Drilling New Wells : $100/ft Sour Gas Recycling Costs. Heterogeneity limits sweep efficiency.

16 16 Weyburn CO 2 Project, Saskatchewan, Canada Started in $1.3 billion Encana project. $100 million DGC project. 25 year life. 1,300 MMbo in place. CO 2 recovery 130 MMbo. 10% OOIP from CO 2 flood. 723 wells, 179 horizontal, 221 injection. Injecting MMcfpd CO 2. 95% Quality CO 2 from Great Plains in Beulah. 198 mile pipeline 4,655’ deep. 10’-89’ thick. Sour API gravity. Vuggy Limestone: 15% porosity 30 md. Marly Dolomite: 26% porosity 10 md. SSWAG injection due to fractures.

17 17 CO 2 Reservoir Excel Database NDIC Derived Data Author’s Data Input Unit Name/ Pool/ OOIP CO2 Oil Recovery (8% OOIP) Peak Rates, CO2 Oil Reserve Category Primary EUR, RF Favorable/Unfavorable Secondary EUR, RF CO2 Flood Characteristics Unit size Porosity, Permeability, Boi Effective Date uo, uw, M, h, BHT, API, Rw WOR, Soi, Soirr Swirr, P*, Pbp, Non-Unitized Fields Distance to CO2 Pipeline, Fracture Description

18 18 North Dakota Highest Ranked Reservoirs for CO 2 Flooding Mississippian -Madison Group  Mission Canyon  Glenburn  Sherwood  Ratcliffe Devonian - Duperow Permian/Triassic -Spearfish Pennsylvanian -Tyler “Health”

19 19 North Dakota Lowest Ranked Reservoirs for CO 2 Flooding Silurian - Interlake Devonian - Winnipegosis Madison with Cross-seal Fractures Ordovician - Red River B with Cross- seal Fractures

20 20 CO 2 Potential Oil Reserve Classification Probable, Possible, Unfavorable Probable (>2MMbo and <2MMbo): Highest probability of success based upon empirical analysis and comparison to other successful projects. Possible (>2MMbo and <2MMbo): Feasible but have less favorable reservoir characteristics. May have lower oil recovery. Unfavorable: Significant reservoir problems. Projects with greater than 2 MMbo recoverable best candidates.

21 21 Probable Top Ten North Dakota Units for CO 2 Flooding Beaver Lodge - Madison 17.6 MMbo Tioga - Madison 17.2 MMbo Big Stick - Madison 13.3 MMbo Fryburg - Heath (Tyler) 12.4 MMbo Beaver Lodge - Devonian 11.1 MMbo Newberg - Spearfish & Charles 7.7 MMbo Wiley - Glenburn 7.6 MMbo Blue Buttes - Madison 7.4 MMbo North Tioga - Madison 7.2 MMbo Charleson North - Madison 6.4 MMbo

22 22 Possible Top Ten North Dakota Units for CO 2 Flooding Cedar Hills South - RRB28.8 MMbo Cedar Hills North - RRB22.2 MMbo Antelope - Madison 8.0 MMbo Cedar Creek - Ordovician 7.7 MMbo Medicine Pole Hills West - RRB 3.4 MMbo Medicine Pole Hills - RRB 3.2 MMbo Medicine Pole Hills South - RRB 3.1 MMbo Eland - Lodgepole 2.8 MMbo Lignite - Madison (PA) 2.6 MMbo Rough Rider East- Madison 2.3 MMbo

23 23 Unfavorable North Dakota Units for CO 2 Flooding Horse Creek Red River Red Wing Madison Fryburg Madison TR Madison (South)

24 24 Constraints to North Dakota CO 2 Development Most oil reservoirs are 7,500 feet and many have well spacing >80 acres requiring high cost infill drilling. Only Nesson Anticline fields are less than 10 miles to existing CO 2 pipeline. Fields not on the Nesson anticline will be burdened with large pipeline installation costs. Most existing waterflood units are in mature waterflood stages at high water cuts. Low permeability and highly heterogeneous. Many reservoirs have strong water influx from vertical fractures outside of pay zone boundaries.

25 25 Conclusions 55 fields in North Dakota have Probable CO 2 recoverable reserves of 171 MMbo. 26 fields in North Dakota have Possible CO 2 recoverable reserves of 106 MMbo. One successful CO 2 pilot has been conducted to date. Comparison of North Dakota reservoir characteristics to successful Texas and Canadian reservoirs utilizing CO 2 flooding is favorable. Future North Dakota CO 2 development constraints are principally economic and will require large capital investments over long time periods plus the ability to manage both oil price and CO 2 price risks. A long term economic perspective will be required since CO 2 projects require long payouts on investment.

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