A key risk associated with the Goodwyn A (GWA) facility has been removed with the deconstruction of the drill derrick.
Some 120 tonnes of steel were removed over 20,000 hours worked offshore – beginning onshore at the end of last year and ending in May this year. That means, of course, that the bulk of the deconstruction took place during the cyclone season, and Woodside and its contractors had to contend with six tropical low events.
“Because of bad weather we actually had to build back parts of the derrick we’d deconstructed to make sure that we left the derrick safe in its partially deconstructed state,” explains Eric Kumar, principal project engineer. And that makes the outcome of zero accident reports and no unplanned events even more impressive.
The 55,000 tonne GWA platform is connected to the Goodwyn gas field located 23km south-west of the North Rankin A (NRA) platform and is about 135km north west of Karratha. Standing 290m tall, in water of 131m, it was commissioned in 1995. The drill derrick was part of the original construction and drilled GWA’s original 30-plus wells.
But it has not been required for many years, and as it got older it posed more hazards, including the potential to collapse in the event of a cyclone above Category 4. To ensure safety, the platform had to be evacuated whenever such a severe weather event was forecast. So the decision was taken to deconstruct it.
Offshore installation manager (OIM) Gary Sargeson says it was one of several big brownfields jobs completed at GWA in recent times, including the “grouting” of the flare tower legs to improve stability. But despite the labour-intensive work, the safety record has been exemplary. In fact, GWA ran from 12 July 2016 to 12 July 2017 with zero injuries – a first for the North West Shelf (NWS) Project.
“It’s the first time we’ve gone 12 months operationally without anyone being hurt and to successfully complete big work scopes like we did during that period is a big achievement on its own,” Gary says. Eric points to planning and collaboration as being key in the safe and successful removal of the drill derrick. “There was early identification of construction methods to reduce the risk of different types of removal, plus continuous engagement with Operations and Maintenance right the way through the deconstruction,” says Eric.
A collaborative and integrated approach via integrated activity planning also was critical. Mid-way through the deconstruction of the highest module (Module 3), Woodside changed to a single engineering, procurement and construction management (EPCM) contactor executing offshore brownfields works.
Wood Group, under the leadership of the Wood Group project manager Gary Quinn, managed the remainder of the deconstruction process. Alex Herbison, superintendent of Wood Group, says it was very rewarding for his team to be involved. “A full derrick condition survey was performed to review the condition of connections and verification of lengths and heights of structural members,” he notes.
“The success of the project was a direct result of the collaborative vision and constant pursuit of excellence,” Alex says. “It demonstrates the high level of professionalism and dedication while the level of communication between our projects teams has set the benchmark for future activities - the drill derrick deconstruction will enable the GWA asset to continue production in a safer environment.”
Alex attributes the safe removal of the derrick to innovative thinking and workforce engagement in practising and refining execution strategies. He says a strong team ethos was encouraged by early, regular and continual engagement during both planning and execution periods. In total, 78 critical lifts were required and a number of smaller sundry lifts.
Eric says meticulous attention to detail before deconstruction started was of vital importance. “This, together with other office-and site-based reviews, enabled a full awareness of all the risks presented by working at height, lifting operations and dropped object protection.” He adds that all lifts were identified in a very detailed lift plan.
The last of those lifts took the heaviest load – a steel section weighing 8.3 tonnes. This gave the team a safe boundary within which to work, he says, as well as the necessary information to enable site-based decisions on how best to proceed with lifts in various weather conditions. Indeed, health and safety was paramount.
Prior to the mobilisation, the entire project team attended a health and safety session which reinforced the importance of ensuring that everybody fully appreciated the scope and methodology of the project and its risks, mitigations and their roles and responsibilities. Gary says: “As the OIM, the big thing for me is that the deconstruction of the drill derrick removes a vulnerability. “It’s a huge step for health and safety because it removes things like the dropped object potential and saves us needing to do dropped object surveys every six months.”
The derrick has been sold for scrap metal.
Trunkline Q3 2017