ENGINEERING, CONSTRUCTION, & INSTALLATION
S7000 removes first structures
from decommissioned Miller platform
This August, Saipem began removing the first topsides structures from BP’s Miller platform in the UK central North Sea. During its 15-year operating lifes- pan the facility, located 270 km (168 mi)
northeast of Aberdeen, was a key hub for BP,
producing 345 MMboe.
BP discovered the field in 1983 in water
depths of 100 m (328 ft). Production started
in June 1992 through the eight-legged, steel
jacket platform, with drilling, production, processing and accommodation modules installed
on a module support frame. In 2007, when
the field reached the end of its economic oil
and gas producing life, BP received cessation of production (CoP) approval from the
UK government. Thereafter, a much smaller
team maintained and crewed the platform
for its new role as the base for the industry
Jigsaw offshore search and rescue helicopter
(SARH). This arrangement remained in place
until 2015 when Jigsaw was replaced with a
new industry-wide SARH solution.
Between CoP and 2010, BP spent £170
million ($224 million) preparing Miller’s fa-
cilities for final removal with a campaign that
involved plugging and abandonment (P&A)
of wells and cleaning of the platform topsides.
In 2016, the company appointed Petrofac as
duty holder to support late life management
of Miller, with responsibility for the platform
and managing all aspects of the offshore and
onshore activities in the run-up to the second
phase of decommissioning. Later that year, BP
contracted Saipem UK to remove and dispose
of the 28,000-metric ton ( 30,865-ton) topsides
and the 18,000-metric ton ( 19,842-ton) jacket.
Saipem has been performing project
management, engineering, and associated
documentation work from its UK headquar-
ters in Kingston, near London. The chosen
methodology for the removal operation – reverse installation using the heavy-lift vessel
Saipem 7000 (S7000) – has been the most
logical and cost-effective for Miller’s design.
It minimizes operational complexity and safety
risks by removing the need for multiple barge
transfers of the cut sections of the platform,
allowing these to be transported directly to
the quayside for subsequent disposal.
A key feature of the process is that all the
modules will be transported either on the deck
of the S7000, or suspended in slings from the
vessel’s large cranes via the ‘lift and carry’
method. This approach requires access to an
ultra-deepwater quayside and port to allow
the S7000 to remain ballasted down at transit
depth until it has completed offloading opera-
tions. Due to the present lack of such facilities
in the UK, Saipem has opted to take the Miller
sections to the Kvaerner Stord yard in western
Norway for final disposal and recycling.
Following last year’s award of the engi-
neer, prepare, remove, and dispose contract
to Saipem, preparations started to ensure the
platform would be ready for the scheduled ar-
rival of the S7000. In November 2016, a drone
sur vey of the platform provided detailed infor-
mation of its various structures, particularly in
hard-to-access areas. These included the flare
tip, drilling derrick, exhaust stack and under
deck: the information facilitated verification of
existing engineering drawings and documents.
In Januar y 2017, a team mobilized offshore
to start onsite preparations for the module-by-
module removal campaign. The key compo-
nents of the preparator y phase were ensuring
adequate and safe access to the lifting points of
each module, and conducting examinations to
verify that the lifting points were in good shape
and suitable for the tasks ahead. Most of the
original lifting points proved to be sound, and
the team’s inspections revealed no defects.
Miller comprises 12 large modules, and
with the original lifting points still in place
and intact, it is essentially a case of taking the
platform apart the same way it was put in. The
platform’s design was considered efficient at
the time and may even have been devised with
ultimate decommissioning in mind.
By comparison, BP’s previous major UK
North Sea decommissioning project, the re-
moval of the 28,000-metric ton ( 30,864-ton)
older generation North West Hutton platform
in 2008, required 22 heavy lifts and 90 days
to remove the topsides. Miller’s topsides can
be removed with 12 lifts, over a period of
around 30 days.
Another important facet of the prepara-
tory work on Miller was the separation of the
modules: each had to be separated from the
adjacent modules. Heavy duty bolts connecting
the drilling derrick to the drilling substructure
and the substructure to the drilling and well
bay module were also taken off to ensure easy
removal by the S7000’s cranes prior to lift-off.
Elsewhere, the cellar deck module will be dis-
connected from the jacket structure when the
risers, caissons, and jacket legs are severed a
few meters below deck elevation. Other sec-
tions of the platform that have been separated
to simplify removal operations include walk-
ways, stairs, pipes, cables and cable trays.
In August, the S7000 arrived at the field lo-
cation. Then followed final shutdown activities
to power down and de-man the platform, and
the first of the heavy lifts, including removal of
the platform’s derrick top, crane booms, heli-
deck and accommodation module. The vessel
subsequently transported these sections to
Stord for offload, demolition, recycling, or re-
use. Around 97% of the materials from Miller
will likely be recycled. A total of five offshore
heavy-lift vessel campaign trips are scheduled
with removal due to be completed in 2018.
Collaboration has been vital to the suc-
cess of this project, with the local UK supply
chain making a major contribution, adapting
skills traditionally applied in exploration and
production activity to decommissioning. •
Win Thornton is Vice President Decommissioning BP.
This is an adapted version of an article published in
August 2017 in Decom News by the UK organization
Decom North Sea.
The S7000 removing the Miller platform’s
accommodation module this August. (Image