Application for Variation of a Pipeline Licence – Pipeline Licence WA-20-PL

Feature Name

Easting

(MGA Zone 50)

Northing

(MGA Zone 50)

Midline PTS

280780

7733279

Flange to Midline PTS

280773

7733271

PLET

280770

7733179

Wheatstone Trunkline Crossing

284734

7731353

KP 10

289852

7728996

Halyard Umbilical Crossing

292067

7727976

KP 20

298940

7724826

Jansz Umbilical Crossing

303933

7723394

KP 30

308449

7721774

KP 40

317698

7717970

KP 50

327020

7714358

East Spar Crossing

328256

7713913

Coastal Waters

329613

7713423

General Details

1.

Pipeline Name (meaningful to industry):

Gorgon Commonwealth Waters Pipeline

2.

Start Point Description:

Midline PTS

3.

‘Start’ Point of Pipeline Coordinates (GDA94):

a)      Northing:

b)     Easting:

a)       Northing: 7733279 mN

b)      Easting: 280780 mE

4.

End Point Description:

3 Nm seaward of MLWM

5.

‘End’ Point of Pipeline Coordinates (GDA94):

a)      Northing:

b)     Easting:

a)      Northing: 7713423 mN

b)      Easting: 329613 mE

6.

Substance to be Conveyed:

Wet Gas – Predominately Methane with approx 14% CO2

7.

Characteristics of Substance to be Conveyed:

a)      Gas Composition:

b)     Oil Viscosity (centistokes):

c)      Flashpoint of Oil:

d)     Operating Temperature Range °C

a)       Gas Composition

b)      N/A

c)       N/A

d)      7 to 28 °C

Design Details

8.

Pipe Dimensions

a)      Outside Diameter (mm):

b)     Length of Pipeline (km):

a)       876 mm

b)      52.87 km

9.

Nominal Wall Thickness

a)      Standard Wall (mm):

b)     Heavy Wall (mm):

a)       38.0 mm

b)      N/A

10.

Joint Type (Welded, Mechanical etc):

Butt welded

11.

Design (at standard conditions)

a)      Initial Design Capacity (MMscf/d):

b)     Maximum Design Capacity (MMscf/d):

c)      Design Life (Years):

d)     Erosional Velocity (m/s):

a)      1909 MMscf/d

b)      1909 MMscf/d

c)       50 years

d)      30.5 m/s

12.

Pipeline Corrosion Allowance

a)      Internal (mm):

b)     External (mm):

a)       Internal:

4.5mm (KP 0 to 30)

3.0mm (KP 30 to 52.87)

b)      External: 0.0 mm

13.

Pipe Free Span (m) at Location (KP):

Assessed using FEA on pipeline digital twin

14.

Pipe Steel Specification and Grade:

(a)   Pipeline:

(b)   Riser:

a)       Carbon steel suitable for sour service, DNVGL-ST-F101

DNV SAWL 450 SFDU

b)      N/A

15.

Minimum Yield Strength of Pipe Steel:

450 MPag

Temperature & Pressure Details

16.

Design Temperature:

a)      Pipeline °C:

b)     Facilities °C:

a)      0 to 50 °C (for Commonwealth)

b)      N/A

17.

Maximum Operating Temperature

a)      Pipeline °C:

b)     Facilities/Stations °C (Normal):

a)       28 °C

b)      N/A

18.

Minimum Operating Temperature

a)      Pipeline °C:

b)     Facilities/Stations °C (Normal):

a)       Pipeline 7 °C

b)      Facilities: N/A

19.

Design Pressure (MPag):

29.9 MPag @ 130 m WD

20.

Inlet Pressure Range (kPag):

8,000 to 14,600 kPag

21.

Outlet Pressure Range (kPag):

8,000 to 14,600 kPag

22.

Field Test Pressure

a)      Proposed Field Test Pressure:

b)     Minimum Field Test Pressure

[  ] x MAOP = [  ] MPag:

a)       36.5 MPag @ 130 m WD

b)      Leak tested to 369 barg – 24 hours @ 130 m WD

23.

Maximum Allowable Operating Pressure (MAOP)

a)      MPag at      °C for Pipeline:

b)     MPag at      °C for Facilities/Station:

a)      MAOP is 20 MPag at max operating temp @ 130 m WD

b)      N/A

Pipeline Coatings

24.

Protective External Coating Specification and Thickness (mm):

FBE 0.735 mm

25.

Weight Coating Design Specification and Thickness (mm):

AS 1397 65 to 90 mm

26.

Field Joint Coating:

FBE + PUF Infill

(PUF required where concrete coating applied)

27.

Pipe-to-Pipe Joint Coating:

FBE + PUF Infill

(PUF required where concrete coating applied)

Control Monitoring

28.

Pressure and Flow Controls Description:

Pipeline isolation shall be via the subsea isolation valves and the pipeline isolation valves located within the pig receiver station at the LNG plant. The design uses an Instrumented Over pressure Protection System (IOPPS), located at each subsea production centre, with a design pressure less than well-head shut-in pressure (WHSIP), from over-pressure events. This system complies with AS 2885.4.

29.

Safety and Emergency Shutdown Description:

If an emergency situation occurs that threatens a MODU working above producing subsea facilities (e.g. dropped object), activation of a hand switch or defined loss of communications from MODU will initiate a MODU ESD. This isolates the Gorgon or Jansz wells and production flowline at the manifold where the MODU is working (the MODU has control of the well it is working on), to minimise any potential consequences. The MODU ESD is transmitted to the Gorgon GTP, isolating all wells on the manifold where the MODU is located.

30.

Telemetry Control:

Fibre-optic cables provide primary communication. Electric power cables provide power to the subsea equipment, and serve as the communications path for the backup copper-based communications system.

31.

Pigging Facilities:

a)      General Facilities:

b)     Description of Pigging Facilities:

a)      Permanent pig receiver is located in the inlet area of the LNG plant. Design pressure is 36,000 kPa design temperature is 75 °C (max); -46 °C (min).  

b)     Permanent pig receiver will be sized to accommodate the latest generation intelligent pig and shall be capable of launching and receiving.

32.

Provisions for cathodic protection of the pipeline:

Offshore:

Sacrificial anodes

33.

Cathodic Potential Monitoring:

Yes

34.

Cathodic Protection Test Posts:

N/A

Valves & Inline Facilities

35.

Fittings, Valves and Flanges Specifications

a)      Fittings:

b)     Valves:

c)      Flanges:

In accordance with DNV-OS-F101

a)      Fittings: ASMEB16.9

b)     Valves: API 6D, NACE MR0175

c)      Flanges: N/A

36.

Mainline Valves –

a)      Number of:

b)     Type:

c)      Location (at KP):

d)     Details of Mainline Valves:

N/A

37.

Location of future Off-take Tees (at KP):

N/A

38.

Number of Pipeline Inlet Facilities:

1

39:

Pipeline Inlet Facilities Description:

Diverless PLET

40.

Number of Pipeline Outlet Facilities:

1

41.

Pipeline Outlet Facilities Description:

Butt Welded

42.

Compressor Stations (if applicable)

a)      Number of:

b)     Location (at KP):

N/A

43.

Other Inline Facilities:

Corrosion monitoring spool prior to inlet of flowline (on the tie-in spool)

Crossings & Pipeline Stabilisation

44.

Location of the crossing:

Pipeline crossing locations are documented on Gorgon Pipeline – Overview of Pipeline Route

45.

Pipeline Crossing Type:

Achieved using pipe supports (mattresses) to cross over Apache East Spar Pipeline. Rock dumped for stabilisation.

46.

Crossings Design Standard:

AS 2885.4

47.

Minimum Earth Cover or Other Means of Stabilisation:

Rock Dump

48.

Anchoring Details:

N/A

Pipeline Management

49.

Environmental Design Criteria Description:

Designed to withstand 100 year return period storm levels; Erosion mitigation measures based on hydrological surveys; Minimised flora disturbance based on vegetation surveys; ROW minimised to restrict land disturbance.

50.

Marine Growth Allowance (mm):

Less than 60 m WD = 30 mm

60 m to 130 m WD = 10 mm

51

Risk Management Description:

Gorgon Upstream has a Risk Management Policy aligned to the principles of AS/NZS4360: Risk Management.

Formal safety assessments and risk assessment will be in accordance with AS2885.1.

The Pipeline Risk Management is included in the Formal Safety Assessment; document number G1-NT-REP-J0005.