Environmental statement - Flyndre and Cawdor - Maersk Oil
Environmental statement - Flyndre and Cawdor - Maersk Oil
Environmental statement - Flyndre and Cawdor - Maersk Oil
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<strong>Flyndre</strong> <strong>and</strong> <strong>Cawdor</strong> <strong>Environmental</strong> Statement<br />
Section 2 Proposed Development<br />
Vessel type<br />
Duration<br />
(days)<br />
Working fuel<br />
consumption (Te/d) 1<br />
Total fuel<br />
use (Te)<br />
Survey 40 11 440<br />
Dynamically positioned reel‐lay vessel 25 23 575<br />
Trenching support 40 17 680<br />
Diving support vessel 75 18 1350<br />
Rock dumper 10 15 150<br />
Guard vessel 50 4 200<br />
Supply vessel 20 10 200<br />
Total 3595<br />
1 Source; The Institute of Petroleum 2000.<br />
Table 2‐10 Vessel type <strong>and</strong> fuel usage during installation of subsea infrastructure.<br />
2.6.9. FLOW ASSURANCE<br />
HYDRATES<br />
The initial flow assurance work suggests the <strong>Flyndre</strong> <strong>and</strong> <strong>Cawdor</strong> hydrocarbons will be susceptible to<br />
hydrate formation. The pipeline insulation design will ensure that the temperature profile during<br />
normal operation remains above the hydrate formation temperature.<br />
For extended shutdowns the hydrate mitigation philosophy is to blowdown the system at the host to<br />
a pressure below the hydrate formation envelope at ambient temperature.<br />
Hydrate prevention during start up will be by continuous methanol injection at the trees, upstream of<br />
the choke <strong>and</strong> may also be injected into the riser local to the platform.<br />
The Clyde platform will provide the necessary storage <strong>and</strong> injection equipment to enable methanol to<br />
be injected at the tree <strong>and</strong> upstream of wing <strong>and</strong> master valves.<br />
SCALING<br />
The need for scale inhibition at <strong>Cawdor</strong> is currently uncertain <strong>and</strong> will need to be assessed further<br />
once the first well is drilled. However, injection facilities will be provided in the subsea chemical<br />
delivery system to allow downhole scale injection should it be required. The <strong>Flyndre</strong> well is already<br />
completed with a downhole chemical injection service installed.<br />
SAND<br />
S<strong>and</strong> is not anticipated from the <strong>Cawdor</strong> reservoir <strong>and</strong> is considered unlikely from the <strong>Flyndre</strong><br />
reservoir.<br />
WAX<br />
The Wax Appearance Temperature (WAT) is currently estimated at 35 o C <strong>and</strong> 37 o C for <strong>Flyndre</strong> <strong>and</strong><br />
<strong>Cawdor</strong> respectively. In addition to a low thermal loss design for the pipeline, a wax inhibition<br />
delivery system will be provided. The pipeline insulation design will ensure that the temperature<br />
profile during normal operations remains above the WAT.<br />
D/4114/2011 2‐15
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