MSV Seawell, the pioneering monohull light well intervention and dive support vessel, has returned to service in the North Sea after a $75 million investment by its owners, Aberdeen-based Helix Well Ops (U.K.) Ltd., a U.K. subsidiary of international offshore energy service company Helix Energy Solutions Group Inc.

The 30-year-old vessel’s upgrade was carried out over 8.5 months at the Damen yard in Vlissingen, The Netherlands, followed by extensive sea trials.

Among the upgrades:

  • 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, improving station keeping performance and the safety of wells being worked on, particularly in challenging weather;
  • All electrical systems and cabling have been replaced and upgraded;
  • Onboard accommodation has been improved, enhancing the work and living spaces for MSV Seawell’s 122 crew members;
  • The dive system and bells have been refurbished; and
  • Lifeboats have been upgraded to comply with new North Sea performance standards.

The modifications have changed the distinctive silhouette of the legendary vessel. A new 50-ton crane with active heave compensation and a multipurpose tower has replaced the former 65-ton cranes aft and separate derrick that provided its characteristic profile.

The new tower, designed by Royal IHC, allows the vessel to deploy Helix Well Ops’ 7⅜-in. subsea intervention lubricator (SIL) in addition to its 5⅛-in SIL. It also can stack the complete SIL and deploy it to the seabed in a single run. The ability to deploy the 7⅜-in SIL brings it into line with its sister vessels, Well Enhancer and Skandi Constructor.

MSV Seawell has provided an important and invaluable contribution to the North Sea oil and gas industry over the past three decades,” said Steve Nairn, Helix Well Ops (U.K.) vice president, in a statement. “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, MSV Seawell has demonstrated the cost-effectiveness of utilising a vessel to deliver light well intervention services compared to a rig.”

Launched 30 years ago at the Pallion yard in Sunderland by North East Shipbuilders, MSV Seawell was considered the world’s most sophisticated offshore support vessel when it entered service in 1987. The 114-m (374-ft) vessel was the first in a series to feature electrical propulsion and set a benchmark for multifunctional offshore support vessels, certified as a standby and rescue ship, and equipped as an anchor-handler.

MSV Seawell undertook its first light well intervention 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. In October 1998 the vessel claimed another historic first with completion of a wireline intervention on a horizontal subsea tree in the North Sea’s Arkwright Field.

Among its diverse range of projects are well maintenance, production enhancement, diving and abandonment work. MSV Seawell also recovered a ditched Harrier jet from the Bristol Channel. The vessel’s specification includes a 7 m by 5 m (23 ft by 16.4 ft) moonpool, a twin bell saturation diving system rated to 300 m (984 ft) with a capacity for up to an 18-man dive team and work and observation class ROVs.

MSV Seawell’s history of entering more than 650 wells and decommissioning more than 150 live and suspended wells, including 15 subsea fields, will continue with this refit. The company expects the vessel’s lifespan to extend at least 15 years.

“Refitting MSV 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,” Nairn said. “The investment ensures this iconic vessel will continue to pioneer a market it has helped shape.”

—Joseph Markman