CIS used its remotely operated Subsea Piling System, which makes it possible to drive piles as large as 36-in. in diameter, in water depths to 300 m (984 ft).
In August, the piles were driven remotely to secure the subsea Boa Extension Manifold, which makes up an integral part of the Alvheim development, approximately 225 km (139 ft) west of Stavanger. The development, which transports oil to the UK Scottish Area Gas Evacuation System, is designed to increase oil recovery by enhancing current production rates via three new subsea well step-outs at East Kameleon, Kneler A and Boa.
Once testing of all equipment was completed, the CIS team mobilized with piling and pile-lifting equipment to the Alvheim field. Working from the Skandi Arctic dive support vessel in maximum water depths of 130 m (426 ft), CIS drove the four 30-in. manifold piles.
The Subsea Piling System performed well despite difficult conditions, CIS said. Each pile was successfully driven into the seabed to its respective target depth of 11.25 m (37 ft). The subsea operation was completed in seven hours, which the company said was half of the time originally planned. All four piles were driven with a 90kJ hydraulic hammer in just 160 minutes.
The subsea piling process is carried out by an experienced CIS engineer from a control unit and monitoring system located onboard a nearby vessel. A hydraulic hammer, connected via an electronic umbilical cable to the control system, is lowered into the water and placed directly over the subsea pile. Once it is accurately positioned, the pile will be driven into the seabed by the hammer until it reaches its target depth.
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