An iceberg is towed by an offshore supply vessel (Image courtesy of PAL Aerospace)
Newfoundland and Labrador’s offshore operators develop ice management plans to outline how they will detect, monitor and manage icebergs before they pose a threat. The ice management plan is one element in an operator’s safety management system, which supports safe and environmentally responsible operations.
For detection, operators use: aircraft reconnaissance, detection equipment on support vessels and installations, trajectory modelling and satellite imagery. Using these techniques, operators can effectively track ice bergs and sea ice.
In order to deflect icebergs, the following techniques may be used:
- Floating Towropes are used to tow an iceberg a sufficient distance past a rig or production facility. For large icebergs, two vessels can be used instead of just one. Any time an iceberg is being towed, offshore operators alert the fishing industry and other mariners in the area.
- Water Cannons are used over shorter distances. If the iceberg is small (known as a “growler” or “bergy bit”), equipped vessels use water cannons mounted at the bow or the bridge to spray seawater at the base of the iceberg. This can break the iceberg or change its direction.
- Prop Wash refers to when a vessel repeatedly backs up close to an iceberg and the wash from the propellers creates a localized current, thrusting the berg along a different course. This technique is used for short durations to move bergy bits and growlers that are close to facilities.
- Ice Nets are used to tow icebergs in instances where floating towropes are not useful due to the iceberg rolling or the towline slipping.
Offshore operators design facilities with the harsh environment and seasonal presence of sea ice and icebergs in mind:
- Floating Production Storage and Offloading Vessels are strengthened to withstand sea ice coverage. In an emergency situation, these FPSOs have a quick-disconnect feature, allowing them to safely disconnect and leave the area in the event of unmanageable ice.
- Mobile Offshore Drilling Units like semi-submersibles and drillships can also disconnect from the sea floor and move, if required.
- Gravity Based Structures are sometimes built with ice walls made of concrete. These walls are designed to withstand the impact of a large iceberg.
Newfoundland and Labrador’s offshore operators have spent over $14 million to date on ice management and protection research and development projects.