Charge testing for well concept selection

1. Charge testing for well concept selection

November 2012
Eelco Bakker, Al Zanimonsky,
NAM
Mark Brinsden, Shell
EWAPS 12 - 6
Presented at 1st European & W African Perforating Symposium, Amsterdam 7 – 9 November 2012
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2. content

Well concept evolution
Case for charge testing
Test set-up / test conditions
Charge test results
Findings charge testing
Impact concepts
Conclusions and way forward
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3. Well concept evolution

Netherlands / Southern UK sector scene setting
Mature area, remaining gas/oil accumulations small size (0.2 – 1
BCM)
Early 2000’s: “step change” in costs required
Significant changes (down
sizing) required in well design, rig
selection, well functionality and
surface lay-out in order to meet
challenge
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4. Well concept evolution – 1st step

Old design
current design
Typical well data
Reservoir depths: 2800- 4600 mAH
(1800 – 3500 m TVD)
Reservoir pressure 250 – 360 bar
(undepleted)
Reservoir temperature 100 - 125
deg C
permeability : <1 - 50 mD, porosity
8 - 20 %
typical features:
reduced csg sizes
simple wellhead
3½” cemented completion
2” perf guns, static balanced / slight
underbalance for trigger interval
Concept worked for no. of
years BUT next step ?
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5. Well concept evolution – the next step ?

Proposed “slim”
case, low
permeability
Current base
case
Proposed “slim”
case, high
permeability
FALLBACK
Ο
Ο
3 ½” tbg,
cemented
in 6” – or 4
7/8” OH
2” guns
Ο
2 7/8” tbg,
cemented in
4 7/8”- or 3
15/16” OH
small guns:
3 ½” * 2 7/8”
tbg,
cemented in
4 7/8”- or 3
15/16” OH
small guns:
1 9/16” or
1 9/16” or
1 11/16”
1 11/16”
Driven by
swell data
assumptio
ns
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6. Slim well concept – impact gun size (base modelling)

Gas rate
Km3/d
600
FBHP (bara)
IPR
180
500
2” guns
200
Prod
profile
400
160
300
140
200
Small
guns
40
20
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DATE
Sep-11
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Jun-10
Sep-10
60
Dec-09
0
Mar-10
80
Jun-09
100
Sep-09
100
Mar-09
120
Gas rate
Km3/d
200
0
0
200
400
600
800
1000
Gas rate (Km3/d)
1200
180
160
140
120
Cum
prod
100
60
40
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DATE
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0
Sep-09
20
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Aardolie
Maatschappij BV
test
DoP
assumptions
!!
80
Mar-09
based on initial modeling, impact (Q
/ NPV) of changing to slim
completion could be significant
needs further clarification
Dec-11
Case for charge testing:
6
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7. Test set-up / test conditions

Charge testing conditions in lab
Field conditions
Overburden =
approx 9200 psi
(634 bar)
reservoir
UCS = 1000 – 2000
psi (70 – 140 bar)
Res Pressure = 4350
– 5000 psi (180 - 350
bar)
In order to mimic field
conditions as good as
possible selected the
following parameters:
UCS of test
sample
Carbon Tan material
(sandstone)
Internal
Pressure
internal / confining
stress
Confining
stress on
outside of the
sample
Section 2 only, no
flow conditions
Various combinations
OH size / tbg – and
charge size
Varying cement
thickness
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8. Charge test results 2” charge

DoP 2" charge
EHD inch
DoP, penetration, inch
14
0,26
12
0,24
10
0,22
8
DoP, 2" charge, 6"
OH
6
DoP, 2" charge, 4
7/8" OH
4
0,2
EH, 2"
charge, 4 7/8"
OH
0,18
0,16
2
0
EH, 2"
charge, 6" OH
0
10
20
Sample no
30
Data used in
original
modelling
0,14
0
10
20
Sample no
30
Carried out some 33 tests (3 labs, test data randomly plotted !!)
Tests in 7” and 4” Carbon Tan cores, both centralised / excentralised.
In some tests free gun volume ( FGV) reduced to minimise effect DUB (dyn
underbalance)
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9. Charge test results small charge

DoP,
inch
TCP penetration, inch
7
EHD,
inch
0,22
6
0,2
5
0,18
4
3
TCP, small charge,
4 7/8" OH
0,16
TCP, small charge,
3 15/16"OH
0,14
2
0,12
1
0,1
EH, 4 7/8"
OH
EH, 3 15/16"
OH
0
0
0
5
10
15
Sample no
20
10
Sample no
20
Data used in
original
modelling
Carried out some 17 tests (3 labs, test data randomly plotted !!)
Tests in 7” and 4” Carbon Tan cores, both centralised / excentralised.
In some tests FGV reduced to minimise effect DUB
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10. Findings charge testing (1)

Futher analysis of results
Impact
cement thickness clearly seen in majority of tests (6”
vs 4 7/8” OH, 4 7/8” vs 3 15/16” OH)
DoP impact cement thickness
14
12
2" DoP, 4 7/8" OH
DoP, inch
10
8
2" DoP, 6" OH
6
"small" DoP, 3 15/16"
OH
"small" DoP, 4 7/8" OH
4
2
0
0
5
10
15
20
25
30
Sample no
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11. Findings charge testing (2)

Futher analysis of results
Centralisation
/ stand-off impact: significant and hence to be
included, not directly included in original modeling
Overall
“perforation efficiency” (OH tunnel length/TCP tunnel length)
from tests some 80%, hence efficiency for actual field conditions
lower (less optimal conditions for dyn UB) tentatively set @ 50%
DoP 2” charge
6” OH
vertical
deviated
9”
7.7”
Small charge
Used for original
modeling
4 7/8” OH
7”
4 7/8”
OH
11”
9.6”
EH
0.19”
0.17”
Eff, %
50
50
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vertical
deviated
2.9”
2.4”
Used for original
modeling
4”
3 15/16”
OH
5.1”
4.3”
0.22”
EH
0.17”
0.17”
0.17”
80
Eff, %
50
50
80
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12. Impact charge testing on well concept selection

FBHP
(bara)
200
Inflow Performance Relationship
Impact 2” charge:
2" charge, base model
small charge, base model
180
2" charge, 6" OH, test results
160
2" charge, 4 7/8" OH, test results
140
small charge, 4 7/8" OH, test results
120
small charge, 3 15/16" OH, test
results
test results impact rel.
minor
Higher DoP offset by
lower assumed
perforation eff.
100
Impact small charge:
80
impact clear
60
Lower DoP + lower
assumed perforation
eff.
40
20
0
0
200
400
600
3
Gas rate 1000m /d
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13. “Economics” : Impact charge testing on well concept selection

Mm3
250
245
Cumulative Gas Production Small charge
Major Impact
243
241
239
240
235
BAS
E
234
230
BAS
E
227
225
220
216
215
210
205
200
2” charge
Minor Impact
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14. Conclusions

Charge testing results
Reducing
tubing size to 2 7/8” and using smaller charges not
attractive given loss of inflow / recovery this concept no longer
pursued !!
Impact
perf tunnel efficiency significant
Impact
cement thickness for smaller charges potentially underestimated
potential
impact on selected drilling practices (OH drilling
diameter)
Perforation
tunnel efficiency possibly overestimated in original
modelling
“ideal”
lab tests gave results of approx 80%, field conditions (small
clearance, low static UB) far from ideal.
Way forward
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out gun survival tests for 2” guns inside 2 7/8” tubing if
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15.

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