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Reservoir Management Under Water Injection A Worldwide Perspective Dr. William M. Cobb Dallas, Texas 2 nd National Meeting on Secondary and Assisted Oil.

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Presentation on theme: "Reservoir Management Under Water Injection A Worldwide Perspective Dr. William M. Cobb Dallas, Texas 2 nd National Meeting on Secondary and Assisted Oil."— Presentation transcript:

1 Reservoir Management Under Water Injection A Worldwide Perspective Dr. William M. Cobb Dallas, Texas 2 nd 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 718 Brazil1538 Colombia 514 Ecuador 533 Mexico3252 Venezuela2640 Total9150

3 Argentina Monthly Oil Rate vs Time 1,000 BO

4 Argentina Year 2004 Production BOPD% of Total Primary Production 442, Secondary Production 257, Total699,

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

6 Argentina Percent Primary & Secondary Production Primary Secondary

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

8 Argentina Principle Production Areas Total BOPD % of Country Total Austral47, Cuyana41, Gulfo San Jorge284, Neuquina310, Noroeste17, ,

9 Argentina Year 2004 Production BOPDPrimary, %Secondary, % Austral47, Cuyana41, Gulfo San Jorge284, Neuquina310, Noroeste17, Total699,000

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 % of Total P/I Ratio Austral Cuyana Gulfo San Jorge11, , Neuquina4, , Noroeste Total17, ,

14 Daily NYMEX Oil Price Oil Price Gas Price

15 Common Denominators for Management of Waterfloods on a Worldwide Basis

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

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

18 What are the Key Factors that Drive the Outcome of a Water Injection Project? N p = Cumulative Waterflood Recovery, BBL. N = Oil in Place at Start of Injection, BBL. E A = Areal Sweep Efficiency, Fraction E V = Vertical Sweep Efficiency, Fraction E D = Displacement Efficiency, Fraction N p N*E A *E V *E D

19 Waterflood Recovery Factor E A = f (Mobility Ratio, Pattern, Directional Permeability, Pressure Distribution, Cumulative Injection & Operations) E V = f (Rock Property variation between different flow units) E VOL = Volumetric Sweep of the Reservoir by Injected Water E D = f (Primary Depletion, K rw & K ro, μ o & μ w )

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 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 (cont.) 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 Cumulative Oil Production = 40.0 MMSTB Remaining Oil Production = 5.0 MMSTB Estimated Ultimate Recovery = 45.0 MMSTB 26.0 MMSTB Volumetric Sweep Efficiency for Waterflood Project (Pore Volume Based on 6.0% Porosity Cutoff)

26 Cumulative Oil Production = 40.0 MMSTB Remaining Oil Production = 5.0 MMSTB Estimated Ultimate Recovery = 45.0 MMSTB 26.0 MMSTB 8.4 MMSTB 10% Porosity Cutoff 6% Porosity Cutoff Volumetric Sweep Efficiency for Waterflood Project (Pore Volume Based on 6.0% and 10.0% Porosity Cutoff)

27 Whats the Secret for Maximizing E A and E V (and E VOL )? ITS 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, VSg = 0% Sg = 10% SPE-48952

31 CHANGING HORSES

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

33 Fact: Conculsion: Oil and Water Production Rates are directly related to injection rates. Therefore, DCA of q o vs t or q o vs N p must be evaluated only after giving consideration to historical and projected water injection rates.

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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

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39 Keep Life Simple

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

41 North American Waterflood – Pattern 35-10

42 E-i W-i S-i N-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?? NO ! & 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

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


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