Digitized platforms enable zero-defect construction of offshore facilities

Laser scanning technology increases accuracy

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John M. Rothermel, James McGill - Quantapoint

With oil prices at $60 per barrel or higher, many offshore platforms are being modified to keep production levels as high as possible. Unfortunately, many platforms have little or no as-built (or existing condition) documentation. Additionally, much of what does exist is out-of-date or of questionable integrity.

Bad or non-existent as-built documentation increases the risk for misalignment of piping and other equipment, obstructions in areas targeted for modification, and increased rework and hot work. This results in schedule, cost, production capacity, and safety.

Traditionally, companies have attempted to update as-built documentation using the following steps: (1) team members visited the site and gathered notes after making manual spot measurements with tape measures and plumb bobs; (2) once back at the office, the notes were converted into drawings; (3) which were then handed to the design engineers who created new facility structure around the existing structure; (4) fabricators built components from the design drawings; and finally, (5) an erector attempted to assemble the parts into the existing facility.

Digitizing a platform

Laser scanning is a relatively new technology that replaces manual surveying tools. It is the tool that can be used to digitize a platform - from the waterline to the helideck. The digitized platform includes dimensional and layout information and can be accessed on desktops anywhere in the world to support owners and operators, engineering consulting firms, or project management teams for revamps, asset management, maintenance, safety, training, or facilities and equipment upgrades.

What are the steps involved in digitizing an offshore platform? First, the goals and desired end results of the project are identified to ensure full understanding of requirements. Second, a two-person field crew uses laser scanning to capture overlapping 3D scans for individual areas of the platform, a process that can take from two to 10 days, depending on the size of the platform. Third, advanced algorithms integrate (or register) the laser scans into a network with a measurement uncertainty of no worse than 3 mm from any point to any other point. Fourth, photo-realistic 3D laser models are created that provide a cohesive, high fidelity 3D database for the platform. Finally, the dimensionally accurate and physically complete digitized platform - consisting of the registered laser scans and 3D laser models - is delivered to the client.

Once a platform has been digitized, there is little or no need to send personnel back to the platform. The digitized platform may be accessed directly and can be used to create 2D drawings (equipment layouts, sections, piping & instrumentation diagrams, piping isometrics), extract exact locations for tie points for piping or structural modifications, review proposed designs against actual existing conditions, and to perform constructability reviews such as construction sequencing.