Running-in a new platform!When the real world does not obey your design basis

Martin Olldag BayLeif BlidegnDONG E&P

Geilo 28 March

Content

The Siri Complex

Design basis and expected challenges

CO2 Corrosion

Scaling Real-life and unexpected challenges

Deviations in flowrates and temperature Compressor performance

Wax precipitation Severe slugging

Conclusion

The Siri Complex

A

56095607 5608

B

5606

D

55095508

C

0002

5507

5605

5505 5506

B

0003

A

5604

5504

E

039

570957080009 00100008 5707

0004

0011

5610

5603

5510

5503

031

5706

5710

0005

0012

038

0001

030

F

0007

Projection: Mercator (world) [not to scale]

Operator

DONG Energy

Hess

Mærsk

Fields

Gas

Gas Condensate

Gas & Oil

Oil

Oil & Gas

4° 6°

56°

Nini ØstNini Vest Nini

SofieStine Segment-2

Stine Segment-1SiriSiri Nord

ConnieFrancisca

Cecilie

RauLulita

Harald

Amalie

Svane

Hejre

Svend

Q1Syd Arne

Bertel

Kim

Gert

RavnElly

ValdemarAdda

Roar

RolfDagmar

Gorm

HalfdanLola

TyraTyra Sydøst

Halfdan/NESkjold

Dan AlmaKraka

Regnar

4/956/95

16/9813/061/907/869/95

4/981/06

5/98

14/06 7/892/06

NorwegianShelf

DanishShelf

BritishShelf

DutchShelf

GermanShelf

3/07

8°

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Siri Wellhead and process platform First oil March 1999 Tank capacity 40.000 m3

Bed capacity 60 pers. Weight 11.000 Tonnes Reinjection > 95% Design capacity 50.000 barrels/day

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Stine Segment 1 Subsea template First oil May 2004

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Nini A Unmanned wellhead platform First oil August 2003 Monotower platform Weight 2900 Tonnes 6 Producers 4 Injectors

Cecilie Unmanned wellhead platform First oil August 2003 Monotower platform Weight 2900 Tonnes 3 Producers 1 Injector

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

The Siri Complex

Nini East Unmanned wellhead platform First oil February 2010 Monotower platform Weight 2900 Tonnes 2 Producers 1 Injector Drilling ongoing

Design Basis

Expected Challenges CO2 Corrosion

Scaling

CO2 Corrosion

High CO2 content in Nini East reservoir – 0.76 mol%

Will spread to all producing platforms via liftgas

Existing platforms designed for low CO2 content

A new corrosion strategy was needed

CO2 Corrosion

Selection of an appropriate corrosion inhibitor was based on laboratory testing, which clarified:

Inhibitor performance - including persistency on pipe wall and pitting corrosion; Tendency to form precipitation of gunk or solid matter; Thermal aging and corrosion tendency of neat inhibitor; Compatibility with scale inhibitor under topside and down-hole conditions; Protection of welds with nickel content.

CO2 Corrosion

Followed up by offshore test on Stine

CO2 Corrosion

The corrosion monitoring program was expanded further to include: Online ER-probes (Electrical Resistance) on satellite platforms, logging actual corrosion

rate every 6th hour. The addition of an ECN-probe (Electrical Chemical Noise) is being considered;

In-line corrosion coupons with welds; Ultrasonic and radiographic WTM (Wall Thickness Measurements); Collecting pigging debris for analysis; CMU (Corrosion Monitoring Unit) coupled to side-streams, where coupons are evaluated. Analysis of water composition and residual corrosion inhibitor.

Design Basis

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

Material SelectionInhibitor Injection via Lift Gas

Pigging Debris Analysis

Design Basis

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

ER probes and coupons

Design Basis

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

Sidestream Corrosion Rigs

Design Basis

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

Routine sampling

Design Basis

Nini

Cecilie Siri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini East

NiniNini

CecilieCecilie SiriSiri

10" Water Injection

6/10" Water Injection

4" Gas lift

4" Gas lift12" Multiphase

8" Multiphase

Stine S1

Umbilical

Nini EastNini East

Risk Based Inspection

Scaling

The alternation in composition would result in scaling

0

2

4

6

8

10

0 50 100 150 200 250

Satu

ratio

n Ra

tio

Pressure (Bar)

Siri SCA 2

CaCO3

BaSO4

Reservoir

Bottom Hole

Wellhead

Separator

Degasser

Scaling

An injection system of scale inhibitor via lift gas has been installed, in order to mitigate scaling.

Selection of appropriate scale inhibitor included following tests: Tendency to precipitate or gunk; Scale inhibition efficiency; Compatibility with other chemicals.

Real-life

Real-life and unexpected challenges Deviations in flow rates and temperatures; Compressor performance; Wax precipitation; Severe slugging.

Actual Flowrates

The actual flowrates was lower than expected

0

500

1000

1500

2000

2500

19.02 10.04 30.05 19.07 07.09 27.10

Oil

Sm^3

/day

Nini East Predicted Vs. Actual

Actual Oil Flowrate Predicted Oil Flowrate

0

200

400

600

800

1000

1200

1400

1600

19.02 10.04 30.05 19.07 07.09 27.10

Oil

Sm^3

/day

Nini A Predicted Vs. Actual

Actual Oil Flowrate Predicted Oil Flowrate

Snowball effectLower production More problems

Actual Flowrates

0

50

100

150

200

250

300

350

400

450

19.02 10.04 30.05 19.07 07.09 27.10

Gas k

Sm^3

/day

Nini East Predicted Vs. Actual

Actual Gas Flowrate Predicted Gas flowrate

0

50

100

150

200

19.02 10.04 30.05 19.07 07.09 27.10

Gas k

Sm^3

/day

Nini A Predicted Vs. Actual

Actual Gas Flowrate Predicted Gas Flowrate

Actual Flowrates

0

50

100

150

200

250

300

350

400

19.02 10.04 30.05 19.07 07.09 27.10

GOR

Sm^3

/Sm

^3

Nini East Predicted Vs. Actual

Actual GOR Predicted GOR

0

50

100

150

200

19.02 10.04 30.05 19.07 07.09 27.10

Gas k

Sm^3

/day

Nini A Predicted Vs. Actual

Actual Gas Flowrate Predicted Gas Flowrate

Actual Flowrates

0

20

40

60

80

100

19.02 10.04 30.05 19.07 07.09 27.10

Lift

Gas

kSm

^3/d

ay

Nini East Predicted Vs. Actual

Actual Lift Gas Flowrate Predicted Lift Gas flowrate

0

500

1000

1500

2000

2500

3000

3500

4000

19.02 10.04 30.05 19.07 07.09 27.10Prod

uced

Wat

er S

m^3

/day

Nini A Predicted Vs. Actual

Actual Water Flowrate Predicted Water Flowrate

Temperature

0

5

10

15

20

25

30

35

40

45

50

Tem

pera

ture

[C]

Temperature - Predicted Vs. measured

Expected Temperature [24-04-10] Measured Temperature [24-04-10]

Expected Temperature [29-11-10] Measured Temperature [29-11-10]

Nini East NiniArrival NiniDeparture Siri

Compressor performance

Compressor performance

Compressor capacity was lower than expected Moleweight was out of Spec.

Compressor performance

4 Months after Nini East production started, the compressor was revamped with similar internals

The replaced internals was covered in rust

Compressor performance

Compressor performance

Compressor performance

Compressor performance

~4 kg of deposits was found in the compressor 65% iron oxide 5% iron sulphide 30% organic matter No chlorides or carbonates (indicating no liquid carry from the separators).

Compressor performance

The new internals increased capacity, but it was dropping steadily

Compressor performance

Corrosion happened in wet gas system - downstream LP Acid cleaning was carried out during the investigations Iron-rich water and condensate from knock-out drum was routed back to LP inlet scrubber TEG carry over from Glycol contactor to inlet scrubber for HP-section Mixture of condensate, iron-rich water and TEG entering LP inlet scrubber, provokes foam

formation -> liquid carry-over to LP-compressor

Compressor performance

Cleaning and chemical injection gave good results

Compressor performance

In January the compressor was revamped with new internals, designed for the new mole weight.

Compressor train does now deliver as expected

Wax issue

During routine pigging in NiniA-Siri pipeline a 14m^3 wax plug was formed. It was 160 meters long.

Wax issue

Wax issue

Wax issue

Heavy wax deposits was caused by: Initial WAT ~30C Actual WAT ~34C Lower Nini East temperature Shut-in of high WC wells on Nini A

Wax issue

The main points in the new wax strategy are: Special bypass pigs purchased; High water cut wells at Nini A restarted prior to pigging; Tailor-made chemicals for wax inhibiting/dispersion/dissolving; Mechanical removal of wax in production wells; Downhole injection of chemicals through chemical injection line at Nini East.

A clean-up campaign was performed Semi-intelligent pigging 17 pigs were launched – Increasing effective diameter

Wax issue – Differential pressure

172 mm

172 mm

176 mm

Pipe ID -182 mm

Wax issue

New strategy is successful

No shutdowns

Example (7 Feb 2011) Pressure drop before pigging – 11.6 Bar Pressure drop after pigging – 6.7 Bar Pipeline capacity can be increased by ~ 30%

Slugging

Severe Slugging is a challenge at Siri

The introduction of Nini East resulted in increased flaring

Slugging

Slugging

Challenged by several slug types Terrain-induced slugging Riser-induced slugging Hydrodynamic slugging

AB

C

D

Slugging

Slugging solutions: Manual choking; Automatic choking; Slug catcher; Antifoam injection; Slug handling by slug control valve; Slug mitigation by slug control valve.

Riser induced slugging

ISC System (Cranfield)

Chemical Injection

Slug mitigation (ISC system)

Conclusion

Design basis is not the real world!

Operation procedures has to be reviewed and updated

Be ready for some urgent challenges

Tieback solutions needs the right people at the right time

In spite off challenges: Stable production Prolonged Siri lifetime A valuable asset to the Siri Complex

58

Thank you for your attention!