Transcript Reservoir Management Under Water Injection A Worldwide

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
Current Oil Production in
South America (1000 B/D)
•
•
•
•
•
•
•
Argentina
Brazil
Colombia
Ecuador
Mexico
Venezuela
Total
718
1538
514
533
3252
2640
9150
Argentina
Monthly Oil Rate vs Time
1,000
900
1,000 BO
800
700
600
500
400
300
200
100
20
06
20
05
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
19
96
19
95
0
Argentina
Year 2004 Production
BOPD
% of Total
Primary
Production
Secondary
Production
442,000
63.2
257,000
36.8
Total
699,000
100.0
Argentina
Monthly Oil Rate vs Time
900
1,000 BO
800
700
Secondary Production
600
500
400
300
Primary Production
200
100
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
19
96
19
95
0
Argentina
Percent Primary & Secondary Production
90
80
Primary
70
60
50
Secondary
40
30
20
10
0
1994
1996
1998
2000
2002
2004
2006
Argentina
Principle Productive Areas
Noroeste
Cuyana
.
Neuquina
Gulfo San Jorge
Austral
Argentina
Principle Production Areas
Austral
Cuyana
% of
Total BOPD Country Total
47,000
6.7
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
70.0%
60.0%
Nequina
50.0%
40.0%
30.0%
Gulfo San Jorge
20.0%
Cuyana
10.0%
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
Austral
19
96
19
95
0.0%
Argentina Oil and Injection Well
Count vs Time
25,000
20,000
15,000
Producing Wells
Injection Wells
Total Wells
10,000
5,000
0
2000
2001
2002
2003
2004
2005
2006
Argentina Injection Well Count and
Average Daily Injection per Well
Injection Wells
BWP Day/Well
20
00
20
00
20
01
20
01
20
02
20
02
20
03
20
03
20
04
20
04
20
05
20
05
20
06
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
Argentina
Well Distribution on 1/1/05
1.7
Injectors
40
938
5.5
11,005
Neuquina
Noroeste
Austral
Cuyana
Gulfo San Jorge
Total
Producing
289
% of
Total
% of
P/I
Total Ratio
0.8
7.2
246
4.8
3.8
64.2
2,740
53.6
4.0
4,852
28.3
2,086
40.8
2.3
57
0.3
0
0.0
-
17,141
100.0
5,112 100.0
3.4
1/
1/
19
93
1/
1/
19
94
1/
1/
19
95
1/
1/
19
96
1/
1/
19
97
1/
1/
19
98
1/
1/
19
99
1/
1/
20
00
1/
1/
20
01
1/
1/
20
02
1/
1/
20
03
1/
1/
20
04
1/
1/
20
05
1/
1/
20
06
Daily NYMEX Oil Price
80
30
10
20
70
60
15
50
40
10
Oil Price
20
5
Gas Price
0
0
Common Denominators for
Management of Waterfloods on
a 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
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
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
Waterflood Recovery Factor
Np
N
 RF
RF  E A * EV * ED



EVOL
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)
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:
V p So
, STBO
Oil in place at start of waterflood =
Bo
Produced oil since the start of injection =
N p ,STBO
Oil currently in reservoir = Oil in water bank + oil in oil bank
Oil in water bank =
Oil in oil bank =
V p Evw (1.0  Sw )
Bo
,STBO
V p (1.0  Evw )(1.0  S wc )
Bo
,STBO
Volumetric Sweep Based on Oil
Production Data
N p Bo
Evw 
SPE-38902
Vp
 1.0  So  S wc
S w  S wc
Example
Waterflood Statistics
Conditions at Start of Waterflood
Connate Water Saturation
Gas Saturation
Oil Saturation
Residual Oil Saturation
=
=
=
=
Oil Viscosity
= 0.3
centipoise
= 1.57
RB/STB
Oil Formation Volume Factor
22 percent
8 percent
70 percent
31 percent
Example (con’t.)
Total Unit
Pore Volume
Cumulative Oil Production Since Start of
Injection
Current Volumetric Sweep Efficiency
= 350,000
MB
= 40,000
MSTB
= 0.552
Remaining Oil Production under Current
Operations
Estimated Waterflood Ultimate Recovery
= 5,000 MB
Ultimate Volumetric Sweep Efficiency
under Current Operations
= 0.600
= 45,000
MSTB
Volumetric Sweep Efficiency for Waterflood Project
(Pore Volume Based on 6.0% Porosity Cutoff)
1
26.0 MMSTB
Evw  0.85
0.8
0.6
Evw
0.4
Cumulative Oil Production
= 40.0 MMSTB
Remaining Oil Production
= 5.0 MMSTB
Estimated Ultimate Recovery = 45.0 MMSTB
0.2
0
10
20
30
40
50
60
70
80
Production Since Start of Waterflood, Np, MMSTB
Volumetric Sweep Efficiency for Waterflood Project
(Pore Volume Based on 6.0% and 10.0% Porosity Cutoff)
1
26.0 MMSTB
8.4
MMSTB
Evw  0.85
0.8
0.6
10% Porosity Cutoff
Evw
6% Porosity Cutoff
0.4
Cumulative Oil Production
= 40.0 MMSTB
Remaining Oil Production
= 5.0 MMSTB
Estimated Ultimate Recovery = 45.0 MMSTB
0.2
0
10
20
30
40
50
60
70
80
Production Since Start of Waterflood, Np, MMST B
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!
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
k50  20md
Dykstra-Parsons, V
SPE-48952
Sg = 0%
Sg = 10%
0.6
0.24
1.10
0.7
0.71
3.30
0.8
1.20
5.60
CHANGING
HORSES
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)
Decline Curve Analysis
Fact:
qo 
iw * Einj * f o
qw 
iw * Einj * f w
Bo

iw * Einj * (1  f w )
Bo
Bw
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
4,000
3,500
3,000
BOPD
2,500
2,000
BOPD
1,500
1,000
500
0
10,000
12,000
14,000
16,000
18,000
20,000
Cum. Oil - MBO
22,000
24,000
26,000
28,000
30,000
Latin American Waterflood
4,000
20
3,000
15
BOPD
2,500
2,000
10
1,500
1,000
5
500
0
10,000
0
12,000
14,000
16,000
18,000
20,000
22,000
Cum. Oil - MBO
24,000
26,000
28,000
30,000
Water Injection - MBWPD
3,500
BOPD
MBWiPD
Latin American Waterflood
4,000
20
3,000
15
BOPD
2,500
2,000
10
1,500
1,000
5
500
0
10,000
0
12,000
14,000
16,000
18,000
20,000
22,000
Cum. Oil - MBO
24,000
26,000
28,000
30,000
Water Injection - MBWPD
3,500
BOPD
MBWiPD
WOR is Independent of Injection Rate
qw
WOR 
q0
WOR 
iw * Einj * f w
iw * Einj * (1  f w )
fw
WOR 
(1  f w )
(WOR ) STD .COND .
fw
Bo

*
(1  f w ) Bw
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
Latin American Waterflood
Producing WOR
100
10
WOR
1
0
5,000
10,000
15,000
20,000
Cum. Oil - MBO
25,000
30,000
35,000
40,000
Keep Life Simple
Production Centered 5-Spot Pattern
N-Well
80 Acres
W-Well
E-Well
C-Well
S-Well
MONUMENT BUTTE UNIT-MB FED 10-35 - Production
North
American Waterflood – Pattern 35-10
8.0
28000
6.0
24000
5.0
20000
4.0
16000
3.0
12000
2.0
8000
1.0
4000
0.0
1982
0
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
GOR, SCF/BO
MBBL/MONTH
7.0
32000
Oil
Wtr
Wtr Inj
GOR
MONUMENT BUTTE UNIT-MB FED 10-35 - Oil Rate vs. Cumulative Oil
North American Waterflood – Pattern 35-10
7.0
6.0
Oil Rate, MBO/Month
5.0
4.0
3.0
2.0
S-i
E-i
1.0
N-i
W-i
0.0
0.0
50.0
100.0
150.0
200.0
250.0
300.0
Cumulative Oil, MBO
350.0
400.0
450.0
500.0
MONUMENT
BUTTE
UNIT-MB
FED 10-35
- WOR 35-10
vs Cumulative Oil
North
American
Waterflood
– Pattern
WOR
10.0
1.0
0.1
0.0
50.0
100.0
150.0
200.0
250.0
300.0
Cumulative Oil, MBO
350.0
400.0
450.0
500.0
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 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
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
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!)
Pretty Please with Sugar!
Keep Life Simple
BOPD
BWPD
MCFPD
WCUT
GOR
1/
1/
04
1/
1/
05
1/
1/
02
1/
1/
03
1/
1/
00
1/
1/
01
1/
1/
98
1/
1/
99
1/
1/
96
1/
1/
97
1/
1/
94
1/
1/
95
1/
1/
92
1/
1/
93
1/
1/
90
1/
1/
91
1/
1/
88
1/
1/
89
1/
1/
86
1/
1/
87
1/
1/
84
1/
1/
85
1/
1/
82
1/
1/
83
1/
1/
80
1/
1/
81
Oil (BOPD); Water (BWPD); Gas (MCFPD); WC%
70
GOR
One Well Field - Latin America
Field
Analysis – Latin America
140
1.4
130
120
1.2
110
100
1
90
80
0.8
60
0.6
50
40
0.4
30
20
0.2
10
0
0
BOPD
04
1/
1/
02
1/
1/
00
1/
1/
98
1/
1/
96
1/
1/
94
1/
1/
92
1/
1/
90
1/
1/
88
1/
1/
86
1/
1/
84
1/
1/
82
1/
1/
80
1/
1/
Oil Production, BOPD
One Well Field - Latin America
Field Analysis – Latin America
100
90
80
70
60
50
40
30
20
10
0
BWPD
04
1/
1/
02
1/
1/
00
1/
1/
98
1/
1/
96
1/
1/
94
1/
1/
92
1/
1/
90
1/
1/
88
1/
1/
86
1/
1/
84
1/
1/
82
1/
1/
80
1/
1/
Water Production, BPD
One
Well
Field - –Latin
America
Field
Analysis
Latin
America
100
90
80
70
60
50
40
30
20
10
0
BOPD
BWPD
BWPD
04
1/
1/
02
1/
1/
00
1/
1/
98
1/
1/
96
1/
1/
94
1/
1/
92
1/
1/
90
1/
1/
88
1/
1/
86
1/
1/
84
1/
1/
82
1/
1/
80
1/
1/
Water Production, BPD
One
Well
Field - –Latin
America
Field
Analysis
Latin
America
100
90
80
70
60
50
40
30
20
10
0
GOR
04
1/
1/
02
1/
1/
00
1/
1/
98
1/
1/
96
1/
1/
94
1/
1/
92
1/
1/
90
1/
1/
88
1/
1/
86
1/
1/
84
1/
1/
82
1/
1/
80
1/
1/
GOR, MSCF/BO
One
Field -–Latin
FieldWell
Analysis
LatinAmerica
America
2
1.5
1
0.5
0
BOPD
GOR
04
1/
1/
02
1/
1/
00
1/
1/
98
1/
1/
96
1/
1/
94
1/
1/
92
1/
1/
90
1/
1/
88
1/
1/
86
1/
1/
84
1/
1/
82
1/
1/
80
1/
1/
Oil Production, BOPD
100
90
1.8
80
1.6
70
1.4
60
1.2
50
1
40
0.8
30
0.6
20
0.4
10
0.2
0
0
GOR, MSCF/BO
One
Well
Field - –Latin
America
Field
Analysis
Latin
America
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
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 Production, BOPD
One
Well
Field - –Latin
America
Field
Analysis
Latin
America
100
10
1
BOPD
One
Well
Field - –Latin
America
Field
Analysis
Latin
America
100
80
70
60
50
EUR @ 10 BOPD = 625MBO
40
30
20
10
Cum Oil - MBO
80
0
70
0
60
0
50
0
40
0
30
0
20
0
10
0
0
0
Oil Production, BOPD
90
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