Environmental Statement - Maersk Oil

Balloch Field Development Environmental Statement
Section 2 Proposed Development
GPIII operations and production chemists will continually monitor this constraint and manage GPIII
base production. Should this constraint become unacceptable, as part of the ongoing GPIII
production management there are condensate handling mitigations that have been identified. De‐
bottlenecking options would be further pursued in the event they are required.
2.5.7. ISOLATIONS AND HOOK‐UP
Double block and bleed production isolations currently exist on the DC2 manifold. The Balloch wells
can be hooked‐up to the DC2 manifold without the need for production shutdown or extensive
flushing of production or lift gas flowlines. Flushing and isolation risk assessments will be prepared
and detailed methodologies completed prior to operations.
2.5.8. PIPELINE TESTING AND COMMISSIONING
After pipe lay, the pipelines will be hydro tested prior to production to ensure they maintain pressure
and do not leak. As part of this process, the pipelines will be flooded with potable water dosed with
biocide, oxygen scavenger, dye and corrosion inhibitor. Following the leak test, the pipeline systems
shall be de‐watered using dyed Monoethylene Glycol (MEG) and treated seawater.
The potable water, along with chemical additives, may be discharged to the sea surface or processed
through existing facilities and re‐injected with the produced water stream. The chemicals to be used
for pipeline testing have yet to be finalised; however, the dose and quantities will be in accordance
with the manufacturers’ specifications.
For the purposes of this ES, it is assumed that all displaced water will be discharged overboard.
Details of the disposal of pipeline testing chemicals will be provided in the subsequent PON15C.
2.5.9. SUBSEA INFRASTRUCTURE PROTECTION
Concrete mattresses and grout bags will be required to provide protection to the subsea
infrastructure associated with the proposed Balloch development. It is estimated that a maximum of
30 concrete mattresses and 15 grout bags will be required for the complete development, i.e.
assuming three production wells. The mattresses will measure 6 x 3 x 0.15 m (L x W x H) and have a
mass of 2.4 te each while the grout bags will measure 1 x 0.5 x 0.5 m (L x W x H) and have a mass of
1 te each.
2.5.10. SUBSEA INSTALLATION SUPPORT VESSELS
Vessel type, duration and fuel usage for the installation of the subsea infrastructure are given in Table
2‐13.
Table 2‐13 Vessel use and fuel demand associated with the installation of the subsea infrastructure.
Vessel type 1
Phase I; appraisal/production wells
Duration (days)
Working fuel
consumption (te/d) 1
Total fuel use (te/d)
Diving Support Vessel (transit) 8 22 176
Diving Support Vessel (working) 30 18 540
Phase II; second and third production wells
Diving Support Vessel (transit) 2 16 22 352
Diving Support Vessel (working) 60 18 1,080
1 Source: The Institute of Petroleum (2000)
2 It is assumed that the second and third wells will be drilled at different times, requiring the vessels to go offsite
between the drilling of each well. Similarly it is expected that the DSV will go offsite between the drilling
campaigns.
2‐19