Fugro Models Complex Sea Currents

press release January 31, 2012

Managing vessel heading and cable pay-out from stinger in strong currents for accurate touchdown in trench.

3D sea current modelling is an important step forward in extending the boundaries of safety and efficiency in subsea operations.

Fugro Subsea Services Limited is a manufacturer and operator of ROVs and provider of subsea engineering, construction support and inspection, maintenance and repair services. Its Robotic Technologies business line has announced the introduction of three-dimensional sea current profiles to its DeepWorks family of subsea simulators. Users can now model currents as they vary with depth and location, enabling more realistic representations of current flows across large sea areas, in shallow waters and around targets. Complex current profiles can be quickly configured to better understand the physical effects on objects like the ROV tether as it moves through different current fields.

A simple user-interface allows the operator to define the strength, heading and elevation of currents, at different geographic coordinates and depths as a series of current profiles in a simulation. Once setup, the user can readily modify values as required over the duration of the mission being simulated.

Each current is defined as a 3D vector and a set of these vectors defines a complex current profile from the sea surface to the seabed. Full horizontal and vertical interpolation is supported, which allows the current’s strength and true direction to be calculated and monitored at any point in the current field.

This allows the operator to predict the effects of currents during a cable-lay operation, for example, to determine how far the vessel heading must be offset from the trench to compensate for the effects of the current. In deeper water fields, complex current profiles make it difficult, unaided, to predict cable touch down accurately. DeepWorks now enables different current settings to be tried in various scenarios, to determine the safe operating envelope and helps to validate procedures for optimal payout speed and vessel navigation.

“The ability to model complex currents adds an extra dimension to simulation. This is very useful when running engineering simulations in the office, but is especially valuable when running live offshore operations,” said Dr Jason Tisdall, Robotic Technologies Business Line Manager. “The ability to predict where subsea risers and umbilicals are in real-time based on the currents flowing is a powerful safety and cost reduction feature.”

Modelled currents give more realistic environmental conditions for training ROV pilots in station-keeping, navigation and performing intervention operations involving moveable bodies, or working in close proximity to targets for detailed inspections. Accurate knowledge of current behaviour also provides dive teams with a better understanding of the safety constraints for payout and management of the diver’s umbilical cable to avoid hazards.

3D sea current modelling is an important step forward in extending the boundaries of safety and efficiency in subsea operations. 3D sea current profiles is available now with new orders for DeepWorks and as an upgrade to existing installations.