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Wide beam design combines riser-based intervention with well construction capability

Wed 06 Sep 2017

Wide beam design combines riser-based intervention with well construction capability
Siem Helix 1 started work offshore Brazil earlier this year; sister vessel Siem Helix 2 will now start work early in 2018

The first quarter of 2017 saw Helix Energy Solutions Group’s Siem Helix 1 light well intervention vessel finally start operations offshore Brazil on contract to Petrobras

 

Contract commencement followed the completion of contract negotiations with Petrobras, Brazil’s state oil company, to amend terms for contracts for Siem Helix 1 and sister vessel Siem Helix 2, both of which were contracted and ordered before the downturn in the offshore oil and gas industry following the steep fall in the oil price.

When Siem Offshore’s well intervention vessels were ordered, the oil price was still above US$100/barrel. All that changed after July 2014, when the price began its steep fall, leading Petrobras, which is using the vessels on long-term deals, to renegotiate the agreement for the ships with Helix Energy Solutions, which is chartering them from the Norwegian owner.

The contract for Siem Helix 1, originally scheduled to begin no later than 22 July 2016, was amended to commence between 22 July 2016 and 21 October 2016, and the day rate under the contract was reduced to a level acceptable to both parties. The contract for Siem Helix 2, originally scheduled to begin no later than 21 January 2017, was amended to commence between 1 October 2017 and 31 December 2017, and the day rate for this contract was not changed. As it eventually turned out, Siem Helix 1 actually started work for Petrobras somewhat later even than the amended contract negotiations suggested. Siem Helix 2 is now expected to commence operations in Brazil in Q1 2018.

Siem Helix 1 and Siem Helix 2 were ordered by Siem Offshore from Flensburger shipyard in Germany on the back of a deal that would see the Siem Offshore-owned ships chartered by Helix for an initial period of seven years, with options that can extend the charter periods up to 22 years.

Under the terms of that deal, Siem Offshore was also to provide marine management, including crewing, for the two vessels, which are based on the Salt 307 WIV design from Salt Ship Design. Helix was to provide the topsides and manage the integration of the well intervention equipment onto the vessels, having entered into agreements with Petrobras to provide well intervention services offshore Brazil for an initial period of four years with options to extend.

The Salt Ship Design vessels have an overall length of 158 m and were built in compliance with the requirements of classification as mobile offshore drilling units (MODUs). Purpose-designed as well intervention vessels, they are capable of all aspects of riser-based, through-tubing well intervention operations as well as emergency response and well construction.

Siem Helix 1 and Siem Helix 2 are stable, wide beam vessels (31 m) combining exceptional operational capabilities with enhanced stationkeeping. Both vessels have an intervention tension frame (ITF), offline maintenance tower and deck skidding system, which optimise well operations whilst reducing the need for lifts across the deck and eliminating man-riding from well-centre activity.

They are classed as Well Intervention Unit 2 vessels and can operate in water depths up to 3,000 m. They have a transit speed of in excess of 12 knots and are thus capable of providing service quickly and efficiently where needed. They have a deck loading capacity of 6,000 tonnes, a main offshore crane with active heave compensation of 250 tonnes at 14 m (supplied by NOV) and an auxiliary crane with a capacity of 60 tonnes at 18 m. The vessels also have a hangar for ROVs and two launch and recovery systems. Siem Helix 1 and Siem Helix 2 also have an 8.0 m x 8.1 m moonpool and accommodation that meets ILO MLC 2006/MODU/SPS 2008 standards for a total of 150 people. Given the energy-intensive nature of the work they carry out offshore, electrical power is important to the design. The main generators provide 25,360 kW in total.

Among the equipment suppliers for the vessels are Kongsberg, which was contracted to supply a wide range of equipment including all of the key navigation, positioning and automation technology, and Osbit Ltd in the UK, which was responsible for the blowout preventer maintenance and storage tower, ITF and movable deck equipment. 

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