VESSEL REFIT | Obana – Combined jackup unit to perform platform decommissioning in UK North Sea
Netherlands-based offshore decommissioning specialist Petrodec recently welcomed a self-elevating, heavy-lift platform to its fleet.
Obana was designed jointly by Petrodec and Singapore-based Keppel Offshore and Marine via its Keppel Offshore Technology Development division. The non-self-propelled unit was designed for year-round operations in the North Sea in water depths of up to 65 metres (210 feet).
The jackup was designed for heavy lifting and skidding of offshore structures for both construction and decommissioning projects, including topside and jacket removal of up to 8,000 tonnes. It can also support well intervention or function as an accommodation platform.
Obana consists of Brage and Grabus, two identical jackup units that were originally completed in 1999. Each has three 171-metre (561-foot) truss legs.
Fulfiling a need for more complex decommissioning capability
The project to develop Obana started in 2021 when Petrodec decided on a solution for decommissioning complex offshore platforms in the UK North Sea. The company had considered various possibilities and eventually decided to merge two used jackup vessels into a single vessel.
The combined unit was originally intended to be used as a drilling rig before it was decided to convert it for construction and decommissioning support duties.
The jackups were transported to Rotterdam while a new midship section was constructed in Dubai. With the arrival of the midship section in November 2024, Obana’s 2,000-ton MTC main crane was moved from Rostock to Rotterdam for installation.
In addition to the welding together of the three major sections, four new passageways linking all three sections were created and reinforcement and foundations for the two 60-ton cranes and the boom rest for the main crane were installed. With the three sections finally combined, this resulted in the open deck having a total area of 6,100 square metres (66,000 square feet).
Four Seatrax pedestal-mounted electric cranes and a helicopter deck are also fitted.
New paint was applied to the hull exterior while the voids and areas were merged including the main deck parts.
The accommodation for 136 persons is located as far away as reasonably practicable from the potential location of hydrocarbons and flight path of crane loads. A maximum number of two persons is assigned to each cabin.
The jackup’s onboard systems draw power from eight 1,800kW generators. A 715kW generator supplied by Caterpillar is available for emergency use.
Significant use of recycled steel
The jackup’s emergency evacuation equipment consist of self-propelled lifeboats supplied by Survival Systems International and Palfinger Marine.
Obana has been classed and surveyed by the American Bureau of Shipping and registered under the flag of Saint Vincent and the Grenadines. It is also fully compliant with UK HSEx/OSD Safety Case regulations 2015.
Petrodec said that 85 per cent of the steel used in the jackup is recycled as a means of reducing the environmental footprint of its construction.
