11
Hearing How An Operator
Monitored Individual
Producing Well Pump Intake
Pressures To Maximize The
Areal Sweet In A CO2
Flooding Operation In The
SACROC Unit, San Andres
Presented by: Kim Lomeli
8/26/2015
SACROC Unit
Discovered – 1948
Unitized for wtr flood 1952
First CO2 injection – 1973
(immiscible, little tertiary recovery)
K-M CO2 injection – 2000
(fully miscible, good tertiary recovery)
Patterns 10 Ac. to 90 Ac.
Average K – 30 mD
Most wells have ESP’s
Pressure & Rate Rebalancing
P Q
D’Arcy’s Law
w
e
wfe
rr
ppKhQ
ln
2
dr
dPKAQ
Radial FlowDifferential Form
Calculated Pressure Gradients, SWCL
Incremental Oil ResponseNeeds ESP UpsizeHigh GOR Well CTF/SI
Pressure & Rate Re-balancing
0
500
1000
1500
2000
2500
3000
3500
0 1000 2000 3000 4000 5000
Pu
mp
Inta
ke P
ress
ure
(P
SI)
Inflow Relationships
2
max
8.02.01
R
wf
R
wf
P
p
p
p
q
q
Productivity Index (PI)
0
500
1000
1500
2000
2500
3000
3500
0 2000 4000 6000 8000
q (bbls/day)
q (bbls/day)
Vogel’s IPR
wfR pp
qIP
..
Operating Point:
2000 bbls/day @ 2400 psi
An “Ideal” Pattern for CO2 Flooding
• Symmetrical Pattern
• Equal pressure gradients
• All layers take fluid
• Constant thickness
• Uniform permeability
• Laterally continuous
The Unfortunate Reality
• Asymmetrical Patterns
• Variable gradients
• Multiple layers
• Thickness varies
• Permeability varies
• Discontinuities
10
Step-Rate Testing
An initial SRT is run when the well is placed on initial water
injection to determine BHP, and the injectivity index.
Subsequent SRT’s are run annually, when on water during
WAG cycles
Key objectives:
• 48-hr shut-in prior to test gives a good estimate for reservoir pressure.
• Injectivity index is calculated from BHP vs. rate curve.
• Determination of the formation parting pressure (if observed).
• Pressure fall-off after last step gives an indication of perm and skin.
11
Step-Rate Testing
Skin
Note the near-wellbore skin effect
12
Rapid Pressure Drawdown (IWR < 1)
13
Rapid Pressure Drawdown (IWR < 1)
All ESP’s are equippedto record Pwf andmotor temp.
This data is availablein real-time and canalso be used to trackreservoir pressure
ESP Bottom-hole Gauge
14
Effect of Pressure Re-Balancing
Two Months on Injection/Production.
Boundary wells are drawing down reservoir pressure, flow
paths toward the interior
Nine Months on Injection/Production.
Reservoir pressure has decreased in boundary region, flow
paths realigned, improved sweep
Two months on injection.
No support to the western half of
pattern 261-2 (prior water curtain)
Nine months on injection.
Large ESP draw down pressure,
flowlines rearranged, support to west
15
Pattern 261-2 (showing delayed response)
16
Rate Re-balancing
Direct Channel
A direct channel from injector 212-2 to producer 271-3A
overwhelmed the support from adjacent patterns
17
Rate Re-balancing
With injector shut-in support from adjacent patterns
contributed to the response in producer 271-3A
18
Rate Re-balancing
212-2
Shut-in
Response
271-3A Response to shutting in 212-2
19
Pressure and Rate Re-balancing
Water Curtain
Overran 294-1
294-1 shows the effect of too much water curtain
20
Pressure and Rate Re-balancing
Water Curtain
shut-in
After water curtain shut-in well began receiving CO2 support
294-1 Production After Water Curtain Scaled Back
Decrease
in PIP
Increase in
Oil, GOR
Shut-in Water
Curtain
21
Response to Pressure & Rate Re-balancing
New Patterns Affect on “Nearby” Wells
“Nearby” Well Performance Data
Conclusions
• Successful optimization of a CO2 EOR project requires intensive
and continuous reservoir surveillance.
• Changing withdrawal in producing wells can have a significant
effect on the streamlines between the injector and producers within
a pattern.
• High GOR wells can be managed by downsizing the ESP or by
converting to flow.
• A relatively high processing rate is desirable so that the effects of
rebalancing can be observed in a reasonable time frame.
• High processing rates mean that individual patterns will have a
short producing life so adjustments need to be made as soon as
the opportunities are identified.
Questions