With 345 million
barrels of oil produced during an operating life of 15 years, the Miller
platform acted as a key hub for BP’s North Sea operations.
Now, as the platform is readied for final removal, Decom News spoke to Win Thornton, BP Vice President Decommissioning, for an update on progress and to hear about the opportunities and challenges of a major decommissioning project.
Field life, CoP and late life management
The Miller field, located 270 kilometres north east of Aberdeen, was discovered by BP in 1983 in water depths of 100 metres. Production from the field started in June 1992 and plateaued from late 1992 to 1997 at around 150,000 barrels a day.
The platform comprises topside facilities (drilling, production, processing and accommodation modules) installed on a module support frame supported by an eight-legged steel jacket.
It reached the end of its economic oil and gas producing life in 2007 when Cessation of Production (CoP) approval was received from the UK Government.
Following CoP, Miller was maintained and crewed with a much smaller team as the base for the Jigsaw offshore search and rescue helicopter (SARH), until 2015 when an industry-wide SARH solution replaced the Jigsaw programme.
Between CoP and 2010, BP spent £170million preparing Miller for final removal. This involved plugging and abandonment of wells and cleaning of topsides.
During this stage, the UK supply chain played a vital role, with Scottish and UK companies securing around £140million worth of contracts.
In 2016, Petrofac was awarded a Duty Holder contract from BP to support the late life management of Miller. Based in Aberdeen, Petrofac hold Duty Holder responsibility for the platform, managing all aspects of on and offshore activities to enable the smooth transition to the second phase of the decommissioning programme.
Later in 2016, BP awarded the engineer, prepare, remove and dispose (EPRD) contract for Miller to London-based Saipem Ltd. Saipem will be responsible for removing and disposing of the 28,000-tonne topsides and 18,000-tonne jacket.
Saipem is carrying out project management, engineering and associated required documentation work from its headquarters in Kingston-upon-Thames.
The methodology Saipem has chosen – reverse installation using the Saipem 7000 (S7000) heavy lift vessel – is the most logical and cost-effective method for Miller’s design, minimising complexity and safety risk by removing the need for multiple barge transfers of the cut sections of the platform and allowing the sections of the platform to be transported direct to quayside for disposal. A key efficiency of the removal process is that all the modules will either be transported on the deck of the S7000, or transported to shore slung from the large cranes in what’s call the ‘lift and carry’ method.
This does require access to an ultra-deepwater quayside and port so that the S7000 can remain ballasted down at transit depth until off-load is complete. Given the current lack of such facilities in the UK, Saipem has opted to take the Miller sections to the Kværner Stord AS yard in Norway for final disposal and recycling.
Decommissioning preparatory work
Since the award of the EPRD contract, a programme of preparatory work has been taking place on Miller to ensure it is ready for the arrival of the S7000.
In November 2016, a drone survey of the platform collected detailed information about the platform, particularly in areas not easily accessible.
This included the flare tip, drilling derrick, exhaust stack and under deck, allowing the team to verify existing engineering drawings and documents and support the development of accurate job cards.
In January 2017, a team was mobilised offshore to begin the onsite preparatory work that will allow the module-by-module removal of the facilities.
This preparation work is now complete.
Win Thornton explained: “The key components of the preparatory phase of the project involved ensuring adequate and safe access to the lifting points of each module and carrying out examinations to verify that the lifting points are in good shape and suitable for the job in hand.
“Largely, we have found that most of the original lifting points are sound and our inspections have revealed no defects. This makes our job a whole lot easier.”
Win added: “Miller comprises about 12 large modules and with the original lifting points being in place and intact essentially allows us to take the platform apart the way it was put in.
“It was an efficient design at the time, maybe with decommissioning in mind, maybe not. But it’s going to make our decommissioning job a bit easier.
By way of contrast, Win pointed to the last major BP North Sea decommissioning project – removal of the 20,000-tonne North West Hutton in 2008.
He added: “If you look at North West Hutton, it took 22 heavy lifts and 90 days to remove the topsides. We can do Miller in 12 lifts and about 30 days.”
Another component of the preparation work that has been taking place on Miller is the separation of modules. Each module has been separated from the module sitting above.
Heavy duty bolts connecting the drilling derrick to the drilling substructure and the substructure to the drilling and well bay module below will be removed to ensure easy removal just prior to lift off.
Elsewhere, the cellar deck module will be disconnected from the jacket structure when the risers, caissons and the jacket legs are severed a few meters below deck elevation.
Other sections of the platform which have been separated to allow removal of the Miller include walkways, stairs, pipes, cables and cable trays.
Given that Miller is still operating with a minimal crew, many of the pipes and cables are associated with services essential for maintaining ongoing operations and safety systems.
These elements of the platform will be separated when the S7000 is on location and Miller personnel have been transferred from the platform and the platform has been completely prepared for removal.
On arrival outside the Miller 500 metre zone and after successfully completing pre-lift trials and surveys, the S7000 gangway will be landed.
This will signal the start of the final shutdown of the Miller facilities. Shutdown activities are expected to last around three days, after which any final activities which could not be completed while the platform was still operating will be completed. In all, five offshore heavy lift vessel campaigns are scheduled with removal expected to be complete in 2018.
Strength of UK supply chain
Collaboration has been vital to the success of the Miller decommissioning project to date and Win was keen to highlight the important role played by the local supply chain.
The debate around the UK’s decommissioning capabilities and competitiveness is something BP has been keeping a close eye on going to great lengths to help shape the conversation.Throughout the Miller project, the UK supply chain has made a major contribution, turning skills and expertise traditionally used in exploration and production activity to decommissioning.
Win said: “BP has been very proactive in this space, speaking to ports and yards and both the UK and Scottish Governments to help them understand where the UK can be competitive.
“What we always try to stress, however, is that the UK supply chain already competes. If you look at Miller, we estimate that around £140m of the £170m we spent on plugging and abandonment of wells and cleaning the topsides was with UK suppliers. That’s a lot of jobs.
“Most the engineer, prepare, remove (EPR) work - approximately 70% of the contract value – will be carried out by the UK supply chain and project managed in the UK through Saipem’s teams in London and Aberdeen. In fact, we estimate that once the Miller decommissioning programme is closed out following final removal and disposal, around 80% of the total project spend will have been with our local supply chain colleagues.
“That tells a great story about the strength of the supply chain here in the UK.”