One of the most distinctive vessels operating in the North Sea has undergone a multi-million pound refit and upgrade to ensure it remains at the forefront of the oil and gas industry for many years to come.
The light well intervention and dive support multi-service vessel Seawell has returned to service after a £60 million (US$75 million) investment by its owners, Aberdeen-based Helix Well Ops (UK) Limited, a UK subsidiary of international offshore energy service company Helix Energy Solutions Group, Inc. It marks the beginning of the next chapter in the history of the pioneering monohull vessel.
Launched 30 years ago at the Pallion yard in Sunderland by North East Shipbuilders, Seawell was described as the world’s most sophisticated offshore support vessel when it entered service in 1987. The 114m vessel was the first in a series of vessels to feature electrical propulsion and set a benchmark for multifunctional offshore support vessels, certified as a stand-by and rescue ship, and equipped as an anchor-handler.
Seawell has been at the forefront of the light well intervention market since it undertook its first such project in the Magnus field, northeast of Shetland, in July 1987. In November 1995, it carried out the first subsea tree replacement from a monohull vessel anywhere in the world. The North Sea’s Arkwright Field was the location of another historic first for the vessel in October 1998, when the world’s first wireline intervention on a horizontal subsea tree was completed.
The range of projects Seawell has undertaken has been diverse. Alongside intervention, well maintenance, production enhancement, diving and abandonment work, it has also recovered a ditched Harrier jet from the Bristol Channel. This diversity reflects the vessel’s specification which includes a 7m x 5m moonpool, a twin bell saturation diving system rated to 300m with capacity for up to an 18-man dive team and work and observation class remotely operated vehicles.
The vessel’s multi-million pound upgrade was carried out at the Damen yard in Vlissingen in the Netherlands, taking around eight and a half months, and was followed by extensive sea trials. Improving the efficiency and capability of Seawell were set as key outcomes of the project. Six new Rolls-Royce Bergen C25:33L8ACD generator sets have replaced obsolete Hedemora generators, which had powered the vessel since it was built. The dynamic positioning (DP) thrusters and azimuths have been upgraded to DP3 class. This improves the stationkeeping performance of the popular vessel and the safety of wells being worked on, particularly in challenging weather.
Electrically the vessel is completely new, as all electrical systems and cabling have been replaced and upgraded. Onboard accommodation has been improved, enhancing the work and living spaces for Seawell’s 122 crew members. The vessel’s dive system and bells have been refurbished, while its lifeboats have also been upgraded to comply with new North Sea performance standards.
The modifications have changed the distinctive silhouette of the vessel. A new 50-tonne crane with active heave compensation and a multi-purpose tower have replaced the existing twin 65 tonne cranes aft and separate derrick that provided its characteristic profile.
Designed by Royal IHC, the new tower allows the vessel to deploy Helix Well Ops’ 73/8in subsea intervention lubricator (SIL) in addition to its 51/8in SIL. It can also stack the complete SIL and deploy it to the seabed in a single run. The ability to deploy the 73/8in SIL brings it into line with its sister vessels, Well Enhancer and Skandi Constructor.
Helix Well Ops (UK) vice president Steve Nairn said: “Seawell has provided an important and invaluable contribution to the North Sea oil and gas industry over the past three decades. It was the first vessel of its kind and has delivered many firsts throughout its career. The light well intervention sector has evolved in line with this reliable and popular vessel. Its specification and capabilities have helped the vessel become respected in the North Sea, and more recently further afield. Time and again, Seawell has demonstrated the cost-effectiveness of using a vessel to deliver light well intervention services compared to a rig. Refitting Seawell has been a major undertaking and one that underlines Helix Well Ops’ commitment to the North Sea marketplace, and having a robust and capable fleet of vessels, which includes Well Enhancer and Skandi Constructor, to service it. The investment ensures this iconic vessel will continue to pioneer a market it has helped shape.”
Having already entered more than 650 wells, decommissioned over 150 live and suspended wells, including 15 subsea fields, this refit extends the lifespan of Seawell and ensures it remains at the forefront of the light well intervention market for a further 15 or more years.