Environmental statement - Flyndre and Cawdor - Maersk Oil

2.5.4. DRILL RIG SUPPORT ACTIVITY
Flyndre and Cawdor Environmental Statement
Section 2 Proposed Development
Various support vessels will be associated with the drilling of the Cawdor wells including three AHVs, a
supply vessel and a standby vessel. Table 2‐4 summarises the drilling rig and support vessel activity
and fuel usage during the drilling of the Phase I and II Cawdor wells.
Vessel type
Duration
(days)
Phase I Cawdor Well
Working fuel
consumption (Te/d) 1
Total fuel use
(Te)
3 x Anchor Handling Vessel (transit) 24 2 50 1200
3 x Anchor Handling vessel (working) 6 3 5 30
1 x Semi‐submersible drilling rig 74 10 740
1 x Supply vessel (transit) 88 4 10 880
1 x Supply vessel (working) 22 5 110
1 x Standby vessel (in transit) 4 0.8 3.2
1 x Standby vessel (on station) 74 0.7 51.8
Phase II Cawdor wells (2 wells)
3 x Anchor Handling Vessel (transit) 51 5 50 2550
3 x Anchor Handling vessel (working) 12 5 40
1 x Semi‐submersible drilling rig 148 10 1480
1 x Supply vessel (transit) 176 6 10 1760
1 x Supply vessel (working) 44 5 220
1 x Standby vessel (in transit) 4 0.8 3.2
1 x Standby vessel (on station) 148 0.7 103.6
Total 9172
1 Source; The Institute of Petroleum, 2000.
2 Estimate it takes 4 days to transport rig to and from well location, therefore 2 X 4 day trips per anchor vessel.
3 Assumes a days’ work per vessel on arrival at location and when removing the rig.
4 Assumes supply vessel makes two trips a week and takes 2 days to travel to and from well location (22 trips total).
5 Assumes 4 days to transport rig to first well location and returning 74 days later to transport to second well location & one
day to move between the two well locations.
6 Assumes supply vessel makes two trips a week and takes 2 days to travel to and from well locations (44 trips total).
Table 2‐4 Fuel consumption of vessels associated with drilling of the Cawdor wells.
2.5.5. BLOW OUT PREVENTER
The drilling rig used for the development will be fitted with a Blow Out Preventer (BOP) stack. The
NTvL is fitted with a 10,000 psi high pressure Cameron Iron Works well control system and a BOP
stack. The function of the BOP is to prevent uncontrolled flow from the well by positively closing the
well at the seabed, as and when required. The BOP is made up of a series of hydraulically operated
rams that can be closed in an emergency from the drill floor and also from a safe location elsewhere
on the rig.
2.5.6. WELL DESIGN
Initially one well will be drilled in the Cawdor field, with two further wells anticipated in Phase II.
Detailed well design and completion strategy has yet to be finalised however is expected to follow the
design outlined below for all three wells (Table 2‐5) but may be reverted to an open hole acid frac
system.
2‐ 6 D/4114/2011