Delving deeper

Heavy lifting, drilling and pipelay solutions provider Huisman has designed and built rock dumping systems before, notably for Tideway's Rollingstone and Seahorse vessels. But its next system, to be delivered later this year for the Tideway newbuild Flintstone, will be in an altogether different league.

Fast and highly automated, the Huisman system is seen by Tideway as a key enabler as its specialist fallpipe vessels target accurate rock placement in hitherto unprecedented water depths around 2000m.

‘This is a completely new deepwater system, and only the excavators and belts are not ours,' explains Terence Vehmeijer, Huisman's sales manager pipelay. ‘It's very high-level technology, with a gimball in suspension ensuring significantly improved operability in bad weather conditions compared with earlier systems. The active heave compensation system is also new,' he adds. ‘Normally the energy is stored in hydraulic vessels, but here we are using capacitors. We are doing a lot of testing on the quayside to make sure this will work offshore.'

Weighing around 825t and designed in accordance with Lloyd's CLAME, the stone dumping system will consist of a 240t-capacity gimballing tower and hang-off module, designed to prevent buckling of the self-supporting pipe string as a result of vessel motions. The pipes, approximately 12m long and 1050mm diameter, will be transported from a pipe storage facility (with capacity for 175 pipe sections) by crane to a buffer position and subsequently inserted into the tower using an automated pipe loading system. In the tower, a headclamp and rollerboxes will provide smooth handling and quick coupling of the pipe sections, says Huisman.

As well as skiddable and heave compensated umbilical winches, the company is supplying the moonpool hatches, ROV cursor frames, hydraulic/ nitrogen systems and four control cabins for these systems.

Huisman is also building a more conventional rock dumping system for the new Boskalis vessel. An improved version of Boskalis' current rock dumping system, it is scheduled for delivery early next year.

Smart work
Also taking shape alongside the Huisman quay in Schiedam when OE visited was the second of the company's innovative drilling towers for the new Frontier Drilling/Shell joint venture Bully drillships. Huisman is also responsible for the integration of vessel and equipment. Some smart vessel integration work, bringing the drill floor down to deck level and enabling the tower to be employed on smaller vessels, is expected to bring cost and operational flexibility benefits in ultradeep and Arctic environments.

Huisman's distinctive box-type towers have been employed offshore before, notably on Helix's Q4000 multirole support vessel and more recently on Well Ops' Well Enhancer intervention vessel, but the Bully rigs represent their first application as a full-blown drilling system.

The drilling equipment set allows offline stand building. A total of 950t (more than 44,000ft) of drill pipe and casing is racked back in two carousel type setbacks. Drillpipe and casing are handled in 135ft lengths. The 2400kips drill tower is fitted with active heave compensated drawworks, mounted inside the tower. Another novel feature is remote changeable reeving of the drill line, allowing high block speeds at low fastline speed, says Huisman, adding: ‘Cutting and slipping of the drill line is eliminated altogether by the application of dual drawworks (no deadman anchor). The addition of passive drillstring compensation to the active heave compensated drawworks provides inherent safety and redundancy.'

Once lowered onto the Huisman Schiedam quay mid-August, the Bully 2 tower will be prepared for transportation to Singapore's Keppel Shipyard, where the Bully 1 drillship is currently being commissioned. OE

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