1. Reservoir Management Under Water Injection A Worldwide Perspective
Dr. William M. Cobb
Dallas, Texas
2nd National Meeting on Secondary and Assisted Oil Recovery
September 8–9, 2005
Malargue, Argentina

2. Current Oil Production in South America (1000 B/D)
Argentina
Brazil
Colombia
Ecuador
Mexico
Venezuela 2640
Total

3. Argentina Monthly Oil Rate vs Time
1,000 BO

4. Argentina Year 2004 Production
BOPD
% of Total
Primary Production
442,000
63.2
Secondary Production
257,000
36.8
Total
699,000
100.0

5. Argentina Monthly Oil Rate vs Time
1,000 BO
Secondary Production
Primary Production

6. Argentina Percent Primary & Secondary Production

7. Argentina Principle Productive Areas.
Noroeste
Cuyana
Neuquina
Gulfo San Jorge
Austral

8. Argentina Principle Production Areas
Total BOPD
% of
Country Total
Austral
47,000
6.7
Cuyana
41,000
5.9
Gulfo San Jorge
284,000
40.6
Neuquina
310,000
44.4
Noroeste
17,000
2.4
699,000
100.0

9. Argentina Year 2004 Production
BOPD
Primary, %
Secondary, %
Austral
47,000
86.6
13.4
Cuyana
41,000
61.7
38.3
Gulfo San Jorge
284,000
60.6
39.4
Neuquina
310,000
60.5
39.5
Noroeste
17,000
100.0
0.0
Total
699,000

10. Argentina % of Total Secondary
Nequina
Gulfo San Jorge
Cuyana
Austral

11. Argentina Oil and Injection Well Count vs Time

12. Argentina Injection Well Count and Average Daily Injection per Well

13. Argentina Well Distribution on 1/1/05
Producing
% of Total
Injectors
P/I Ratio
Austral
289
1.7 40
0.8
7.2
Cuyana
938
5.5
246
4.8
3.8
Gulfo San Jorge
11,005
64.2
2,740
53.6
4.0
Neuquina
4,852
28.3
2,086
40.8
2.3
Noroeste 57
0.3
0.0 -
Total
17,141
100.0
5,112
3.4

14. Daily NYMEX Oil Price
Oil Price
Gas Price

15. Common Denominators for Management of Waterfloods on a Worldwide Basis

16. Why Inject Water? Maintain Reservoir Pressure – Pressure Maintenance
Increase Reservoir Pressure – Waterflooding
Supplement Natural Water Influx
But . . .
A, B & C are Displacement Processes and the Goal is to Displace Oil to a Production Well

17. Worldwide Reminders When Managing Waterflood Activities
Pressure Depletion Stops
Volumetric Sweep
Net Pay Cutoffs
Decline Curve Analysis
WOR Analysis
Waterflood Quarterback
Keep the Ax Sharp

18. Np = Cumulative Waterflood Recovery, BBL.
What are the Key Factors that Drive the Outcome of a Water Injection Project?
Np ≈ N*EA*EV*ED
Np = Cumulative Waterflood Recovery, BBL.
N = Oil in Place at Start of Injection, BBL.
EA = Areal Sweep Efficiency, Fraction
EV = Vertical Sweep Efficiency, Fraction
ED = Displacement Efficiency, Fraction

19. Waterflood Recovery Factor
EA = f (Mobility Ratio, Pattern, Directional
Permeability, Pressure Distribution,
Cumulative Injection & Operations)
EV = f (Rock Property variation between different flow units)
EVOL = Volumetric Sweep of the Reservoir by Injected Water
ED = f (Primary Depletion, Krw & Kro, μo & μw)

20. Traditional Waterflood Volumetric Sweep Efficiency Calculation
Uses Net Cumulative Water Injected (Wi-Wp)
Does not Account for Injection losses out of zone
Does not Account for Natural Water Influx

21. Compute Volumetric Sweep Based on Oil Production Data
Oil in place at start of waterflooding = Produced oil since the start of injection
+ Oil currently in reservoir
Where:
Oil in place at start of waterflood =
Produced oil since the start of injection =
Oil currently in reservoir = Oil in water bank + oil in oil bank
Oil in water bank =
Oil in oil bank =

22. Volumetric Sweep Based on Oil Production Data
SPE-38902

23. Waterflood Statistics
Example
Waterflood Statistics
Conditions at Start of Waterflood
Connate Water Saturation =
22 percent
Gas Saturation
8 percent
Oil Saturation
70 percent
Residual Oil Saturation
31 percent
Oil Viscosity
0.3 centipoise
Oil Formation Volume Factor
1.57 RB/STB

24. Example (con’t.) Total Unit Pore Volume = 350,000 MB
Cumulative Oil Production Since Start of Injection
40,000 MSTB
Current Volumetric Sweep Efficiency
0.552
Remaining Oil Production under Current Operations
5,000 MB
Estimated Waterflood Ultimate Recovery
45,000 MSTB
Ultimate Volumetric Sweep Efficiency under Current Operations
0.600

25. Volumetric Sweep Efficiency for Waterflood Project
(Pore Volume Based on 6.0% Porosity Cutoff)
26.0 MMSTB
Cumulative Oil Production = MMSTB
Remaining Oil Production = MMSTB
Estimated Ultimate Recovery = MMSTB

26. Volumetric Sweep Efficiency for Waterflood Project
(Pore Volume Based on 6.0% and 10.0% Porosity Cutoff)
26.0 MMSTB
8.4
MMSTB
10% Porosity Cutoff
6% Porosity Cutoff
Cumulative Oil Production = MMSTB
Remaining Oil Production = MMSTB
Estimated Ultimate Recovery = MMSTB

27. What’s the Secret for Maximizing EA and EV (and EVOL)?
IT’S THE INJECTION WELL!
Properly Locate the Injection Well
Develop an Appropriate Pattern!
Inject Water where You Find the Oil!
Measure and Manage Injection Profiles
Keep Fluid Levels in a Pumped Off Condition
Balance Injection and Withdrawals
Remember the Quarterback!

28. SHIFTING GEARS

29. Net Pay Static OOIP Dynamic OOIP Drive Mechanism Controlled by Cutoffs
Permeability Distribution between Flow Units (Dykstra-Parson Coefficient)
Oil/Water Relative Permeability
Mobility Ratio (Oil and Water Viscosity)
Fluid Saturations at Start of Injection (So, Sg, Swc)
Water Cut Economic Limit

30. Permeability Cutoff Using the Watercut Method at a 95 Percent Watercut Economic Limit
80 Acre Pattern
Dykstra-Parsons, V Sg = 0% Sg = 10%
SPE-48952

31. CHANGING HORSES

32. Decline Curve Analysis
Assume
Gas Fillup has been Achieved (Reservoir contains oil and water
Reservoir Pressure is Approximately Constant (Bo is constant)
Steady State Flow Prevails (Approximately)
Conclusion
Water Injection = Liquid Production (at Reservoir Conditions)

33. Decline Curve Analysis
Fact:
Conculsion:
Oil and Water Production Rates are directly related to injection rates. Therefore, DCA of qo vs t or qo vs Np must be evaluated only after giving consideration to historical and projected water injection rates.

37. WOR is Independent of Injection Rate
Conclusion:
WOR is independent of injection rate
WOR should be applied to individual wells and not field
WOR should be applied using values greater than 2.0

39. Keep Life Simple

40. Production Centered 5-Spot Pattern
N-Well
80 Acres
W-Well
E-Well
C-Well
S-Well

41. North American Waterflood – Pattern 35-10

42. North American Waterflood – Pattern 35-10
S-i
E-i
N-i
W-i

43. North American Waterflood – Pattern 35-10

44. A Friendly Reminder Waterflood Operations
Cartesian Plots of Oil Rate versus Cumulative Oil Production Should Be Prepared on A Well Basis
Semi-log Plots of WOR versus Cumulative Oil Production Should Be Prepared on A Well basis
Preparation of the Above Two Plots For The Entire Field Gives an Average Result Which May be Optimistic or Pessimistic

45. Have there been Recent Developments in Waterflooding Technology??
& YES ! ? ? ? ?
BUT . . .
Improved application of old principles leads to better recovery

46. What Are the Key Elements of a Successful Waterflood?
High Moveable Oil Saturation
Moderate to Low Oil Viscosity
Favorable Relative Permeability
Low Permeability Variation
Symmetrical Patterns
Ability to Inject Large Volumes of Water
Ability to Lift Large Volumes of Produced Water
Pumped Off Producing Wells

47. What are the Pitfalls of Waterflooding Practices?
Failure to keep producing wells in pumped off condition
Failure to clearly distinguish between Static OOIP and Dynamic OOIP (Primary vs Secondary)
Failure to collect sufficient quantity and quality of reservoir data
Failure to timely convert oil wells to injection wells
Failure to monitor injection water quality
Failure to keep the Ax sharp

48. Summary of New Waterflood Paradigms
Remember the Quarterback
(The Injector)
Keep the End in Mind
(Maximize Volumetric Sweep)
Keep the Ax Sharp
(SPE meetings, SPE-TIGS, and SPE.org provide great opportunities to sharpen the mind!)

49. Pretty Please with Sugar! Keep Life Simple

50. Field Analysis – Latin America

51. Field Analysis – Latin America

52. Field Analysis – Latin America

53. Field Analysis – Latin America

54. Field Analysis – Latin America

55. Field Analysis – Latin America

56. Field Analysis – Latin America

57. Field Analysis – Latin America

58. Reservoir Management Under Water Injection A Worldwide Perspective
Dr. William M. Cobb
Dallas, Texas
2nd National Meeting on Secondary and Assisted Oil Recovery
September 8–9, 2005
Malargue, Argentina