Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 2 Proposed Development
Structure Dimensions (m x m) Total footprint (m 2 )
Flyndre manifold 5.5 x 5.2 28.6
Cawdor manifold 12.4 x 10.8 133.92
SSIV 5 x 5 25
Table 2‐8 Subsea footprint of manifolds and SSIV associated with the development.
The manifolds will be piled to resist accidental loadings arising from interaction with fishing
equipment. Four piles will be used to hold each manifold in place, the piles have the following
dimensions and penetration depths:
penetration length = 15 m
outside diameter = 600 mm
The seabed conditions are expected to be similar to those found at the Affleck development. Maersk
Oil has collected information on the pile driving information required to install piles at the Affleck
development. In this case a submersible hammer (IHC Hydrohammer S‐90) and piles that had a
diameter of 610 mm were installed to a depth of 16.5 m, details of this are presented in Table 2‐9.
At the time of writing this ES it was expected that the drivability results presented here would
represent the most onerous driving scenario at the Flyndre and Cawdor fields as the scenario
presented is for a greater piling penetration length and a marginally wider outside pile diameter.
Hammer
Total Blows
IHC Hydrohammer S‐90
963
Driving Time (min) 32 24 19 16 13 12 10 9 8 8
Blow Rate (b/min) 30 40 50 60 70 80 90 100 110 120
Table 2‐9 Drivability results summary.
The SSIV will be a gravity based structure and will not require piling.
2.6.3. PIPELINE DESIGN
Hydrocarbons from the Flyndre and Cawdor fields will be tied back to the Clyde production facilities
via a common Subsea 8”/12” pipe‐in‐pipe export pipeline. The Flyndre to Cawdor line is 4.2 km while
the Cawdor to Clyde is 20.46 km.
A pipe in pipe system was selected for the project as it provides the most robust system with regard
to operability and integrity. The carrier pipe material will be carbon steel and a dry insulation will be
used within the annulus.
2.6.4. PIGGING REQUIREMENT
Routine operational pigging is not envisaged, however to address unforeseen events, the pipeline will
be designed to be pigged and the subsea facilities will be configured with a temporary pigging
connection at the Flyndre end of the pipeline. The Clyde platform will provide space to enable
temporary pig launching/receiving equipment to be installed.
2‐ 12 D/4114/2011