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

Nederlandse Aardolie Maatschappij BV 2Month 2010Restricted

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

Nederlandse Aardolie Maatschappij BV 3Month 2010Restricted

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

3

Significant changes (down

sizing) required in well design, rig

selection, well functionality and

surface lay-out in order to meet

challenge

Nederlandse Aardolie Maatschappij BV 4Month 2010Restricted

Well concept evolution – 1st step

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 ?

4

Old design current design

Nederlandse Aardolie Maatschappij BV 5Month 2010Restricted

Well concept evolution – the next step ?

5

FALLBACK

Ο

Current base case

Ο Ο

3 ½” tbg, cemented in 6” – or 4 7/8” OH

2” guns

Proposed “slim” case, low permeability

Proposed “slim” case, high permeability

2 7/8” tbg,

cemented in

4 7/8”- or 3

15/16” OH

small guns:

1 9/16” or

1 11/16”

3 ½” * 2 7/8”

tbg,

cemented in

4 7/8”- or 3

15/16” OH

small guns:

1 9/16” or

1 11/16”

Driven by swell data assumptio

ns

Nederlandse Aardolie Maatschappij BV 6Month 2010Restricted

Slim well concept – impact gun size (base modelling)

6

0

20

40

60

80

100

120

140

160

180

200

0 200 400 600 800 1000 1200

FBHP (bara)

Gas rate (Km3/d)

0

100

200

300

400

500

600

Mar-09

Jun-09

Sep-09

Dec-09

Mar-10

Jun-10

Sep-10

Dec-10

Mar-11

Jun-11

Sep-11

Dec-11

Mar-12

Jun-12

Sep-12

Dec-12

Mar-13

Jun-13

Sep-13

Dec-13

Gas rate

Km3/d

DATE

Prod profile

0

20

40

60

80

100

120

140

160

180

200

Mar-09

Jun-09

Sep-09

Dec-09

Mar-10

Jun-10

Sep-10

Dec-10

Mar-11

Jun-11

Sep-11

Dec-11

Mar-12

Jun-12

Sep-12

Dec-12

Mar-13

Jun-13

Sep-13

Dec-13

Gas rate

Km3/d

DATE

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 !!

Nederlandse Aardolie Maatschappij BV 7Month 2010Restricted

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 stress

�Section 2 only, no flow conditions

�Various combinations OH size / tbg – and charge size

�Varying cement thickness

Nederlandse Aardolie Maatschappij BV 8Month 2010Restricted

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

modelling

0

2

4

6

8

10

12

14

0 10 20 30

Do

P,

pe

ne

tra

tio

n,

inc

hDoP 2" charge

DoP, 2" charge, 6"OH

DoP, 2" charge, 47/8" OH

0.14

0.16

0.18

0.2

0.22

0.24

0.26

0 10 20 30

EHD inch

EH, 2"charge, 6" OH

EH, 2"charge, 4 7/8"OH

Sample no �Sample no �

Nederlandse Aardolie Maatschappij BV 9Month 2010Restricted

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

modelling

0

1

2

3

4

5

6

7

0 5 10 15 20

TC

P p

en

etr

ati

on

, in

ch

TCP, small charge,4 7/8" OH

TCP, small charge,3 15/16"OH

0.1

0.12

0.14

0.16

0.18

0.2

0.22

0 10 20

EH, 4 7/8"OH

EH, 3 15/16"OH

Sample no �

Sample no �

DoP,

inch

EHD,

inch

Nederlandse Aardolie Maatschappij BV 10Month 2010Restricted

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

2

4

6

8

10

12

14

0 5 10 15 20 25 30

Do

P,

inc

h

DoP impact cement thickness

2" DoP, 4 7/8" OH

2" DoP, 6" OH

"small" DoP, 3 15/16"OH

"small" DoP, 4 7/8" OH

Sample no �

Nederlandse Aardolie Maatschappij BV 11Month 2010Restricted

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

vertical deviated Used for original modeling

6” OH 9” 7.7”7”

4 7/8” OH

11” 9.6”

EH 0.19” 0.17” 0.22”

Eff, % 50 50 80

Small charge

vertical deviated Used for original modeling

4 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

Nederlandse Aardolie Maatschappij BV 12Month 2010Restricted

Impact charge testing on well concept selection

0

20

40

60

80

100

120

140

160

180

200

0 200 400 600 800 1000

FBHP(bara)

Gas rate 1000m3/d

Inflow Performance Relationship

2" charge, base model

small charge, base model

2" charge, 6" OH, test results

2" charge, 4 7/8" OH, test results

small charge, 4 7/8" OH, test results

small charge, 3 15/16" OH, testresults

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.

Nederlandse Aardolie Maatschappij BV 13Month 2010Restricted

“Economics” : Impact charge testing on well concept selection

243

234

239241

216

227

200

205

210

215

220

225

230

235

240

245

250

Mm3 Cumulative Gas Production

BAS

EBAS

E

2” charge Minor Impact

Small charge

Major Impact

Nederlandse Aardolie Maatschappij BV 14Month 2010Restricted

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 under-

estimated

�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

�Carry out gun survival tests for 2” guns inside 2 7/8” tubing � if

Nederlandse Aardolie Maatschappij BV 15Month 2010Restricted