Integrated survey and positioning for FPU in the gulf of Mexico

PROJECT OVERVIEW

Subsea 7 required a strategic partner to support them with an FPU tow-out and in-field hook-up for their client over a three-month period.

The FPU needed to be dry towed from South Korea to the US Gulf, and the FPU final integration activities were to be completed alongside at Kiewit Offshore Services, Ingleside, Texas.

THE CHALLENGE

Subsea 7 required UTEC, a Geo-services brand in Acteon’s Data and Robotics division, to mobilise the FPU at Kiewit Offshore Services fabrication yard in Ingleside, Texas, where the FPU underwent final preparatory work and regulatory inspections before heading 380 miles offshore to its ultimate home, nearly 200 miles south of New Orleans.

Integration activities needed to be undertaken before the FPU could be towed to the final offshore site. This involved remote positioning of 8 x TUGs and Hook-up vessel, including the interfacing of sensors and dimensional control services, position monitoring of the FPU during connection to the towing fleet and during navigation of the inshore tow section, offshore tow section, and upon arrival at the field and mooring hook-up.

A bathymetric and hazard survey of the in-shore tow channel survey needed to be performed before the tow-out to verify the results of the existing survey and to ensure that no major changes had taken place during the intervening period between those surveys and the tow-out scope.

The survey would verify that the channel was free of any obstructions or debris that may adversely affect the tow-out operations along with seabed bathymetry/features and confirmation of the positions of any existing seabed structures.

CUSTOMER GOAL

Subsea 7 required position monitoring equipment consisting of GPS-based transmitters on all vessels involved in the tow, reporting to one master data processing unit and monitor located onboard the FPS with slave monitors on the tugs.

They required the following parameters to be displayed, in real-time:

• Position, orientation, bearing, and speed (overground) of the FPU and all vessels involved in the tow.
• Graphical presentation of the FPS, the tugs, and the lines connecting them.
• Bathymetry during the inshore tow.
• Horizontal clearance to seabed and channel boundaries.

OUR SOLUTION AND ITS COMMERCIAL BENEFITS

Market-leading services and integrated solutions

• The FPU, being such a giant structure, proved to push the limitations of being towed through the Quinta and Corpus Christi Ship Channel to Port Aransas before going out through the Aransas Pass to the Sea Buoy. We provided the end customer with reassurance on the channel limitations through a prep-tow-out 3D representation, giving us a competitive advantage as we were able to flag potential issues in the software, drawing on previous experience from similar projects to minimise risk.
• Environmental elements such as a water depth of 13.7m (45 ft) at the inshore section and wind impacted the tow route due to tidal streams that occurred particularly in the area just outside the Aransas Pass channel jetties. UTEC worked across the Geo-services segment, who have extensive experience working in this channel, to execute the pre-tow channel survey to ensure that no major changes had taken place during the intervening period between the two surveys and the tow out scope, and the route was free of obstructions.
• InterMoor, a Moorings and Anchors brand in Acteon’s Engineering, Moorings and Foundations division provided mooring engineering and offshore support, for Subsea 7.
• Subsea 7, with InterMoor’s support, first performed the mooring line pre-lay, installing over 8,220m of chain. The team then towed the FPU from Ingleside, Texas to its final offshore site in Green Canyon and hooked up the FPU to the pre-laid mooring lines using Island Offshore’s anchor handling vessel Island Victory. InterMoor’s work scope also included equipment marshalling and dock services from their shore base in Fourchon, Louisiana.

Operational bases across the world

• UTEC’s and Subsea 7’s Houston offices are within proximity of each other, which allowed for ease of equipment interfacing and testing of UTEC’s spread into Subsea 7’s container.
• Utilising our regional base allowed for in-person demonstrations of the software development which saved time and mobilisation costs.

Work at scale with a proven track record for delivery

• Subsea 7 required UTEC to manage and execute this complex scope of work, which was tied to the all-encompassing project on which Subsea 7 has been a prime contractor for several years.
• We provided a single point of contact for contracting and project management and were able to streamline processes based on previous contracts with this customer.

Optimise the project to increase commercial value

• UTEC used SIMOPS during the preparation for the mobilisation phase which included dimensional control and final interfacing of the provided equipment package for the entirety of the FPU preparation to meet the requirements of the project schedule.
• The Corpus Christi Ship Channel needed to be closed to other traffic for the duration of the inshore towing operations which avoided disruptions from vessel traffic from both commercial and pleasure craft during the inshore tow.

Combine digital technology and data to enhance our expertise

• UTEC collaborated with third-party software developer 4D Nav to develop a 3D model of the FPU with real-time graphical navigation of the tow out from the Kiewit yard through the ship channel to the sea buoy, followed by offshore tow to the field location. The 3D representation aided in navigation and incorporated alarms that mitigated impact with the channel sides or bottom.
• UTEC leveraged cross-segment knowledge by sub-contracting TerraSond, to perform a bathymetric and hazard survey along the La Quinta channel up to the Aransas pass before the FPU inshore tow to ensure safe and efficient operations during the tow out. The DTM (digital terrain model) generated from this channel survey was displayed in 2D and 3D in the navigation software during the tow out.
• UTEC were able to identify issues and anomalies before they happened using the pre-tow channel survey data provided through the Geo-services segment to fulfil customer requirements.

PRODUCTS USED

• Online survey and surface positioning systems
• Tug management system

“We are proud to have worked on this complex project with Subsea 7 where we were able to apply our experience and expertise in both onshore operations and development, as well the technical proficiency demonstrated by our field staff, to deliver highly accurate survey and positioning services using engineering intelligence and digital technology, resulting in successful project execution with no environmental adverse impacts being encountered. The client was satisfied, and we look forward to collaborating on future project scopes,”
said Brad Paul, UTEC Business Development Manager – Americas

“UTEC being part of the Acteon group provided an opportunity to combine the expertise of several companies to provide a complete solution to support the tow out of the FPU to Subsea 7. Throughout the planning and execution, the UTEC team worked closely with the Subsea 7 survey and engineering teams which resulted in the successful tow out and installation of the FPU,” said John Brader, Subsea 7 SURF Survey Operations Manager, North & Central America

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