Norway-based Swire Seabed reports it has completed a second offshore pipeline campaign for Equinor, Norway, in the North Sea.

The campaign, undertaken during the summer, is the first fully unmanned offshore pipeline inspection ‘over the horizon’ ever completed, surveying up to 100 kilometres from the shore, according to the firm.

The recent inspections by Swire Seabed were completed using a Kongsberg Maritime, Norway, HUGIN AUV with the SEA-KIT, UK, Maxlimer unmanned surface vessel acting as the host vessel for surface positioning and communications to shore.

The complete operation was controlled from an onshore control centre, including launch and recovery of the AUV, command and control of the USV/AUV and monitoring of the acquisition of pipeline inspection data.

The inspections were performed on four pipelines, a distance of 175 kilometres surveyed over two AUV dives.

The AUV, operated by Swire Seabed, acquired bathymetric, synthetic aperture sonar and HD image data in order to verify the continued integrity of the subsea pipelines. The acceptance criteria for data (quality, coverage and density) were identical to the criteria used for traditional tethered inspection methods, Swire Seabed said.

The entire dual USV/AUV operation was executed by a small team of personnel working in a control centre in Swire Seabed’s HQ in Bergen.

“The completion of this project demonstrates Swire Seabed’s ability to deliver ‘firsts’ for the industry. This application of technology represents a step-change in the levels of safety, sustainability and low cost that can be achieved in subsea pipeline inspection and seabed mapping. We look forward to further developing and expanding the service in the coming years,” said Swire Seabed’s chief technology officer, Arvid Pettersen.