Subsea inspection and repair technology keeps production at its peak

Paul Boughton

Companies specialising in subsea inspection, repair and maintenance are making major investments in new technology in order to maximise production from offshore assets. Sean Ottewell reports.

Subsea inspection, repair and maintenance and light construction specialist Harkand has extended its remotely operated vehicle (ROV) support vessel fleet operations in the North Sea by signing a charter agreement for the Surf Ranger.

The multi-purpose vessel, owned by Go Offshore, will be deployed immediately on a pipeline and structural inspection campaign for TAQA's UK business.

The project includes structural inspection at the Harding, Cormorant Alpha, North Cormorant, Tern and Eider (Fig. 1) assets, as well as the inspection of various pipelines, dredging works and mattress installation.

The 85.4m Surf Ranger is a DP2 multi-purpose ROV, survey and air diving vessel featuring a helideck, 60 tonne TTS Energy active heave compensated knuckle boom crane and can accommodate 69 personnel. It is permanently equipped with a Triton XLS work class ROV.

Meanwhile, Harkland continues to pursue its growth strategy with agreements to build up to two new DSVs for the North Sea.

The company has awarded a contract with global shipbuilders Vard Holdings for one DSV, with options for a second. Delivery of the first vessel is scheduled for the second quarter of 2016.

The deal, which marks an investment of US$200m (EUR148 million) per vessel including additional plant and equipment, is the latest in a series of announcements Harkand has made around the growth of its global vessel and ROV fleet, including the recent addition of the new-build Harkand Harmony to its Asia Pacific operations and the long-term charter of the Siem Spearfish for its US operations.

The contract brings Harkand's investment in its global operations since its formation in February 2013 to more than US$300 million (EUR222 million), boosting its vessel fleet to eight and its ROV fleet to 33.

Scheduled for delivery from Vard Soviknes in Norway, each 121m long vessel features a 250-ton offshore crane, an ROV hangar, a twin Bell 18 man saturation diving system, two launch and recovery systems, a deck decompression system for surface diving to 50m and accommodation for up to 120 personnel.

Diving daughter crafts

Unique Hydra has received its second order this year for diving daughter craft systems. The company's diving daughter craft systems are used as DSVs in diving operations where the conventional diving DSV is not able to position close enough to an FPSO or offshore platform.

The support vessel crafts are fitted with surface supplied diving systems capable of supporting Nitrox/air diving operations usually restricted to a maximum depth of 30-35m of sea water (MSW).

The diving daughter craft offshore workboat is usually assisted by an additional support craft that transfers personnel and supplies during the diving operation as well as transporting a casualty in the event of an injury or decompression incident. These are usually simple craft with personnel capacity to take all persons on the diving craft minus the crew.

The mother vessel barge or platform is outfitted with supporting equipment, including the decompression chamber, gas storage and compressors.

Unique Hydra points to a number of important advantages of using diving daughter craft systems. For example, there is a reduced safety risk to divers compared to diving from a dynamic positioning (DP) vessel, due to lack of vessel intake/thrusters hazards, long umbilical excursions and DP failure/drift off. There is also a reduced risk to the offshore asset as the DP vessel does not need to be in close proximity for diving operations.

A shallow keel means that the daughter craft is far more manoeuvrable and can access areas around platform/structure that are inaccessible to larger DP vessels due to risk of damage to risers, umbilicals or anchor chains.

At the same time, mooring to the platform/structure allows the craft to be positioned directly over the diver's worksite, allowing quicker access to the worksite and adding to on-the-job time.

Mobilisation times are also reduced as minimal equipment is required to be installed on the mother vessel, barge or platform beforehand.

Unique Hydra has developed two models of purpose designed diving daughter crafts, the HYDRACraft 1400 14m eight man, and the HYDRACraft 1500 15m 10 man. The company is able to supply turnkey diving daughter craft systems including decompression chamber facility and HP air and Nitrox generation equipment. Both of its new orders are for turnkey solutions.

The Eider Oilfield is situated 184km (114 mi) north-east of Lerwick, Shetland Islands, Scotland. Water depth is 157.5m (517ft).

Pigging solution for non-piggable pipelines

UAE-based global marine solutions provider Marsol International has teamed up with Aubin Group to provide what it describes as an industry first - a total pigging solution for non-piggable pipelines.

In field trials of the technology, they achieved successful displacement of pipeline preservation fluid in three, 48-inch oil pipelines.

The application is ideal for older fields that were not designed for pigging and/or have suffered damage. The solution is also well suited to pigging or cleaning pipe infrastructure that contains 90° bends and/or T-pieces that have varying internal diameters in the same configuration. It reduces the need to strip down, clean and reassemble components, and also reduces the potential for environmental damage.

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