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Nederlandse Aardolie Maatschappij BV 1November 2012Restricted
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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content
Well concept evolutionCase for charge testingTest set-up / test conditionsCharge test resultsFindings charge testingImpact conceptsConclusions and way forward
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Well concept evolution
Netherlands / Southern UK sector scene settingMature 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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Well concept evolution – 1st stepTypical 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 sizessimple wellhead3½” cemented completion2” perf guns, static balanced / slight underbalance for trigger interval
Concept worked for no. of years BUT next step ?
Old design current design
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Well concept evolution – the next step ?
FALLBACK
Ο
Current base case
Ο Ο
3 ½” tbg, cemented in 6” – or 4 7/8” OH2” guns
Proposed “slim” case, low permeability
Proposed “slim” case, high permeability
2 7/8” tbg, cemented in 4 7/8”- or 3 15/16” OHsmall guns:1 9/16” or 1 11/16”
3 ½” * 2 7/8” tbg, cemented in 4 7/8”- or 3 15/16” OHsmall guns:1 9/16” or 1 11/16”
Driven by swell data
assumptions
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Slim well concept – impact gun size (base modelling)
0 200 400 600 800 1000 1200020406080
100120140160180200
Gas rate (Km3/d)
FBHP (bara)
Mar-09
May-09
Jul-0
9Sep-09
Nov
-09
Jan-10
Mar-10
May-10
Jul-1
0Sep-10
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-10
Jan-11
Mar-11
May-11
Jul-1
1Sep-11
Nov
-11
Jan-12
Mar-12
May-12
Jul-1
2Sep-12
Nov
-12
Jan-13
Mar-13
May-13
Jul-1
3Sep-13
Nov
-130
100
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400
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600
DATE
Gas rateKm3/d
Prod profile
Mar-09
May-09
Jul-0
9Sep-09
Nov
-09
Jan-10
Mar-10
May-10
Jul-1
0Sep-10
Nov
-10
Jan-11
Mar-11
May-11
Jul-1
1Sep-11
Nov
-11
Jan-12
Mar-12
May-12
Jul-1
2Sep-12
Nov
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Jan-13
Mar-13
May-13
Jul-1
3Sep-13
Nov
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DATE
Gas rateKm3/d
Cum prod
2” guns
Small guns
IPR
Case for charge testing:based on initial modeling, impact (Q / NPV) of changing to slim completion could be significant needs further clarification test DoP assumptions !!
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Charge testing conditions in lab
reservoirUCS = 1000 – 2000 psi (70 –
140 bar)
Res Pressure = 4350 – 5000 psi (180 - 350 bar)
Overburden = approx 9200 psi
(634 bar)
UCS of test sample
Internal Pressure
Field conditions
Confining stress on outside of the sample
Test set-up / test conditions
In order to mimic field conditions as good as possible selected the following parameters: Carbon Tan material (sandstone) internal / confining stressSection 2 only, no flow conditionsVarious combinations OH size / tbg – and charge size
Varying cement thickness
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Charge test results 2” charge
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)
Data used in original
modelling0 5 10 15 20 25 3002468
101214
DoP 2" charge
DoP, 2" charge, 6" OHDoP, 2" charge, 4 7/8" OH
DoP,
pen
etra
tion
, inc
h
0 5 10 15 20 25 300.14
0.16
0.18
0.2
0.22
0.24
0.26EHD inch
EH, 2" charge, 6" OHEH, 2" charge, 4 7/8" OH
Sample no Sample no
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Charge test results small charge
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
Data used in original
modelling0 2 4 6 8 10 12 14 16 18
0
1
2
3
4
5
6
7
TCP, small charge, 4 7/8" OHTCP, small charge, 3 15/16"OH
TCP
pene
trat
ion,
inch
0 2 4 6 8 10 12 14 16 180.1
0.12
0.14
0.16
0.18
0.2
0.22
EH, 4 7/8" OHEH, 3 15/16" OH
Sample no
Sample no
DoP, inch
EHD, inch
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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)
0 5 10 15 20 25 300
2
4
6
8
10
12
14
DoP impact cement thickness
2" DoP, 4 7/8" OH2" DoP, 6" OH"small" DoP, 3 15/16" OH"small" DoP, 4 7/8" OHDo
P, in
ch
Sample no
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Findings charge testing (2)Futher analysis of resultsCentralisation / stand-off impact: significant and hence to be
included, not directly included in original modelingOverall “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
vertical deviated
Used for original
modeling6” OH 9” 7.7”
7”4 7/8”
OH11” 9.6”
EH 0.19” 0.17” 0.22”
Eff, % 50 50 80
Small charge
vertical
deviated
Used for original
modeling4 7/8”
OH 2.9” 2.4”4”
3 15/16”
OH5.1” 4.3”
EH 0.17” 0.17” 0.17”
Eff, % 50 50 80
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Impact charge testing on well concept selection
0 100 200 300 400 500 600 700 800 900 10000
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200Inflow Performance Relationship
2" charge, base modelsmall charge, base model2" charge, 6" OH, test results2" charge, 4 7/8" OH, test resultssmall charge, 4 7/8" OH, test resultssmall charge, 3 15/16" OH, test results
Gas rate 1000m3/d
FBHP(bara) Impact 2” charge:
test results impact rel. minor
Higher DoP offset by lower assumed perforation eff.
Impact small charge: impact clear Lower DoP + lower
assumed perforation eff.
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“Economics” : Impact charge testing on well concept selection
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Cumulative Gas ProductionMm3
BASE BAS
E
2” charge Minor Impact
Small chargeMajor Impact
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ConclusionsCharge testing resultsReducing 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
under-estimatedpotential 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 forwardCarry out gun survival tests for 2” guns inside 2 7/8” tubing
if successful repeat charge testing pursue the tapered 2 7/8” * 3 ½” completion concept using 2” guns.
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