During the past 18 months, Seatronics, an Acteon company, along with Technip, Star Net Geomantics, and BlueView Technologies, have been developing the BlueView 3D system for underwater metrology. The system combines terrestrial laser and underwater, 3-D multibeam sonar-scanning technology to provide a unique and innovative solution to complex subsea metrology operations.
This work has included several onshore dry-dock trials in Peterhead and Fraserburgh, United Kingdom. Seatronics, along with Star Net, is now a recommended execution contractor for BlueView BV5000 multibeam surveys for inspection and metrology projects, as it understands the system’s capabilities and clients’ subsea measurement requirements.
Seatronics has recently supplied a complete BlueView BV5000-1350 system and personnel for subsea metrology on the UK-based Auk North project in the North Sea, an endeavor that is spearheaded by Talisman Energy Ltd. and the third successful use of this technology. Coupled with Star Net’s extensive experience in advanced data processing techniques, the technology provided very precise measurements between the subsea connection flanges on two manifolds in the Auk North field development.
A new manifold was to be integrated into a field with an existing manifold. The spool piece needed between the new and the existing manifold had to be accurate to 70 mm and have an alignment error of less than 1°. All the metrology aids had been removed from the existing structure, which caused design issues. However, Star Net had laser-surveyed the existing manifold before its deployment as part of a previous onshore dimensional control survey. This dataset became critical in the project execution, since the subcontractor was able to generate temporary metrology aids from the survey data. The location of the flanges within the structures caused additional issues in terms of access.
The BlueView BV5000-1350 system was successfully deployed by its offshore personnel to perform multiple scans around the subsea structures. Data quality control was overseen by Star Net operatives onboard the vessel. Traditional laser scan data augmented this survey data to position the flanges accurately relative to each other and provide precise measurement information to aid in fabricating the adjoining spool piece.
Following the metrology survey, the spool piece was designed and fabricated. As part of the project’s completion, Star Net surveyed the two-piece pipe section and brought the sections together to confirm the fabrication tolerances.