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

Reservoir ManagementReservoir ManagementUnder Water InjectionUnder Water Injection

A Worldwide PerspectiveA Worldwide Perspective

Dr. William M. Cobb

Dallas, Texas

2nd National Meeting on Secondary and Assisted Oil Recovery

September 8–9, 2005

Malargue, Argentina

Current Oil Production in South America (1000 B/D)

• Argentina 718• Brazil 1538• Colombia 514• Ecuador 533• Mexico 3252• Venezuela 2640• Total 9150

ArgentinaMonthly Oil Rate vs Time

0

100

200

300

400

500

600

700

800

900

1,000

1,000 BO

ArgentinaYear 2004 Production

BOPD % of Total

Primary Production

442,000 63.2

Secondary Production

257,000 36.8

Total 699,000 100.0

ArgentinaMonthly Oil Rate vs Time

0

100

200

300

400

500

600

700

800

9001,000 BO

Primary Production

Secondary Production

ArgentinaPercent Primary & Secondary Production

0

10

20

30

40

50

60

70

80

90

1994 1996 1998 2000 2002 2004 2006

Primary

Secondary

.

ArgentinaPrinciple Productive Areas

Noroeste

Cuyana

Neuquina

Gulfo San Jorge

Austral

ArgentinaPrinciple 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

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

Argentina% of Total Secondary

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

Nequina

Gulfo San Jorge

Cuyana

Austral

Argentina Oil and Injection Well Count vs Time

0

5,000

10,000

15,000

20,000

25,000

2000 2001 2002 2003 2004 2005 2006

Producing Wells

Injection Wells

Total Wells

Argentina Injection Well Count and Average Daily Injection per Well

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

Injection Wells

BWP Day/Well

ArgentinaWell Distribution on 1/1/05

Producing

% of Total Injectors

% of Total

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 0.0 -

Total 17,141 100.0 5,112 100.0 3.4

Daily NYMEX Oil Price

0

10

20

30

40

50

60

70

80

0

5

10

15

20

Oil PriceOil Price

Gas PriceGas Price

Common Denominators for Common Denominators for Management of Waterfloods on Management of Waterfloods on

a Worldwide Basisa Worldwide Basis

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

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

What are the Key Factors that Drive the Outcome of a Water Injection Project?

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

Np ≈ N*EA*EV*ED

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)

RF N

Np DVA E

E

EE

VOL

**RF

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

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 =

, STBOp o

o

V S

B

,STBOpN

(1.0 ),STBOp vw w

o

V E S

B

(1.0 )(1.0 ),STBOp vw wc

o

V E S

B

1.0p oo wc

pvw

w wc

N BS S

VE

S S

Volumetric Sweep Based on Oil Production Data

SPE-38902

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

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

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70 80

Production Since Start of Waterflood, Np, MMSTB

Cumulative Oil Production = 40.0 MMSTBRemaining Oil Production = 5.0 MMSTBEstimated Ultimate Recovery = 45.0 MMSTB

26.0 MMSTB0.85vwE

Volumetric Sweep Efficiency for Waterflood Project(Pore Volume Based on 6.0% Porosity Cutoff)

vwE

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70 80

Production Since Start of Waterflood, Np, MMSTB

Cumulative Oil Production = 40.0 MMSTBRemaining Oil Production = 5.0 MMSTBEstimated Ultimate Recovery = 45.0 MMSTB

26.0 MMSTB

0.85vwE 8.4MMSTB

10% Porosity Cutoff

6% Porosity Cutoff

Volumetric Sweep Efficiency for Waterflood Project(Pore Volume Based on 6.0% and 10.0% Porosity Cutoff)

vwE

What’s the Secret forMaximizing 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!

SHIFTING GEARS

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

Permeability Cutoff Using the Watercut Method at a 95 Percent

Watercut Economic Limit

80 Acre Pattern

Dykstra-Parsons, V Sg = 0% Sg = 10%

0.6 0.24 1.10

0.7 0.71 3.30

0.8 1.20 5.60

50 20mdk

SPE-48952

CHANGINGHORSES

AssumeGas Fillup has been Achieved (Reservoir contains oil

and waterReservoir Pressure is Approximately Constant (Bo is

constant)Steady State Flow Prevails (Approximately)

ConclusionWater Injection = Liquid Production (at Reservoir

Conditions)



* * * * (1 )

* *

w inj o w inj wo

o o

w inj ww

w

i E f i E fq

B B

i E fq

B

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.

Latin American Waterflood

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

10,000 12,000 14,000 16,000 18,000 20,000 22,000 24,000 26,000 28,000 30,000

Cum. Oil - MBO

BO

PD

BOPD


0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

10,000 12,000 14,000 16,000 18,000 20,000 22,000 24,000 26,000 28,000 30,000

Cum. Oil - MBO

BO

PD

0

5

10

15

20

Wat

er In

ject

ion

- M

BW

PD

BOPD

MBWiPD


0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

10,000 12,000 14,000 16,000 18,000 20,000 22,000 24,000 26,000 28,000 30,000

Cum. Oil - MBO

BO

PD

0

5

10

15

20

Wat

er In

ject

ion

- M

BW

PD

BOPD

MBWiPD

WOR is Independent of Injection Rate

0

. .

* *

* * (1 )

(1 )

( ) *(1 )

w

w inj w

w inj w

w

w

w oSTD COND

w w

qWOR

q

i E fWOR

i E f

fWOR

f

f BWOR

f B

Conclusion:WOR is independent of injection rateWOR should be applied to individual wells and not

fieldWOR should be applied using values greater than 2.0


1

10

100

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000

Cum. Oil - MBO

Pro

du

cin

g W

OR

WOR

Keep Life SimpleKeep Life Simple

Production Centered 5-Spot PatternProduction Centered 5-Spot Pattern

N-Well

C-WellW-Well

S-Well

E-Well

80 Acres

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

MB

BL

/MO

NT

H

0

4000

8000

12000

16000

20000

24000

28000

32000

GO

R, S

CF

/BO

OilWtrWtr InjGOR

MONUMENT BUTTE UNIT-MB FED 10-35 - ProductionNorth American Waterflood – Pattern 35-10

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 400.0 450.0 500.0

Cumulative Oil, MBO

Oil

Rat

e, M

BO

/Mo

nth

MONUMENT BUTTE UNIT-MB FED 10-35 - Oil Rate vs. Cumulative OilNorth American Waterflood – Pattern 35-10

E-i

W-i

S-i

N-i

0.1

1.0

10.0

0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 400.0 450.0 500.0

Cumulative Oil, MBO

WO

R

MONUMENT BUTTE UNIT-MB FED 10-35 - WOR vs Cumulative Oil North American Waterflood – Pattern 35-10

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

Have there been Recent Developments in Waterflooding Technology??

•NO !

& YES ! ? ? ? ?

BUT . . .

• Improved application of old principles leads to better recovery

What Are the Key Elementsof 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

What are the Pitfalls ofWaterflooding 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

Summary ofNew 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!)

Pretty Please with Sugar!Pretty Please with Sugar!

Keep Life SimpleKeep Life Simple

One Well Field - Latin America

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

1/1/

80

1/1/

81

1/1/

82

1/1/

83

1/1/

84

1/1/

85

1/1/

86

1/1/

87

1/1/

88

1/1/

89

1/1/

90

1/1/

91

1/1/

92

1/1/

93

1/1/

94

1/1/

95

1/1/

96

1/1/

97

1/1/

98

1/1/

99

1/1/

00

1/1/

01

1/1/

02

1/1/

03

1/1/

04

1/1/

05

0

0.2

0.4

0.6

0.8

1

1.2

1.4

BOPD BWPD MCFPD WCUT GOR

Oil

(BO

PD

); W

ater

(B

WP

D);

Ga

s (M

CF

PD

); W

C%

GO

R

Field Analysis – Latin America


0

10

20

30

40

50

60

70

80

90

100

Oil

Pro

du

ctio

n, B

OP

D

BOPD



0

10

20

30

40

50

60

70

80

90

100

1/1/

80

1/1/

82

1/1/

84

1/1/

86

1/1/

88

1/1/

90

1/1/

92

1/1/

94

1/1/

96

1/1/

98

1/1/

00

1/1/

02

1/1/

04

Wat

er P

rod

uct

ion

, BP

D

BWPD



0

10

20

30

40

50

60

70

80

90

100

1/1/

80

1/1/

82

1/1/

84

1/1/

86

1/1/

88

1/1/

90

1/1/

92

1/1/

94

1/1/

96

1/1/

98

1/1/

00

1/1/

02

1/1/

04

Wat

er P

rod

uct

ion

, BP

D

BOPD BWPD BWPD



0

0.5

1

1.5

2

1/1/

80

1/1/

82

1/1/

84

1/1/

86

1/1/

88

1/1/

90

1/1/

92

1/1/

94

1/1/

96

1/1/

98

1/1/

00

1/1/

02

1/1/

04

GO

R, M

SC

F/B

O

GOR



0

10

20

30

40

50

60

70

80

90

100

1/1/

80

1/1/

82

1/1/

84

1/1/

86

1/1/

88

1/1/

90

1/1/

92

1/1/

94

1/1/

96

1/1/

98

1/1/

00

1/1/

02

1/1/

04

Oil

Pro

du

ctio

n, B

OP

D

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

GO

R, M

SC

F/B

O

BOPD GOR



1

10

100

1/1/

80

1/1/

82

1/1/

84

1/1/

86

1/1/

88

1/1/

90

1/1/

92

1/1/

94

1/1/

96

1/1/

98

1/1/

00

1/1/

02

1/1/

04

1/1/

06

1/1/

08

1/1/

10

1/1/

12

1/1/

14

1/1/

16

1/1/

18

1/1/

20

1/1/

22

1/1/

24

Oil

Pro

du

ctio

n, B

OP

D

BOPD



0

10

20

30

40

50

60

70

80

90

100

010

020

030

040

050

060

070

080

0

Cum Oil - MBO

Oil

Pro

du

ctio

n, B

OP

D

EUR @ 10 BOPD = 625MBO


Reservoir ManagementReservoir ManagementUnder Water InjectionUnder Water Injection

A Worldwide PerspectiveA Worldwide Perspective

Dr. William M. Cobb

Dallas, Texas

2nd National Meeting on Secondary and Assisted Oil Recovery

September 8–9, 2005

Malargue, Argentina

Documents

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