Tilt-over Incident Investigation: Liftboat Robert’s Seabed Challenge

NTSB Concludes Probe into Louisiana-based Liftboat, Unveiling Factors Behind 2022 Tilt-over

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The National Transportation Safety Board (NTSB) has recently concluded its comprehensive investigation into a tilt-over incident involving the Louisiana-based liftboat Robert in 2022. The incident occurred during a plug-and-abandonment campaign on several wells connected to an Apache Corp.-owned oil production platform, situated approximately 80 miles southeast of Lake Charles, Louisiana.

On September 23, 2022, the Robert, while supporting the aforementioned campaign, experienced adverse conditions as high waves reached the bottom of its hull while elevated, causing one of its legs to nudge into an adjacent low spot in the seabed. The vessel’s crew had meticulously chosen a location on the east side of the platform after a thorough examination of a third-party survey map by the captain, the company’s VP of operations, and an operations manager.

Following the selection of the site, the crew lowered the legs and elevated the Robert just clear of the waves. As an additional precaution, extra ballast was taken on board as a preload for 36 hours. Despite maintaining a safe distance from a can hole, foul weather prompted the crew to jack down and relocate 18 hours away to the northwest due to an approaching hurricane.

Upon their return on October 3, the Robert chose a new site, jacked up its legs, and raised the vessel approximately 48 feet above the water. The liftboat remained operational for several weeks until November 15 when the captain, anticipating adverse weather conditions, decided to evacuate the vessel. The crew left the Robert at 25 feet above the water, and, as precautionary measures, one generator was left running while the crew boarded a helicopter to shore.

By November 19-20, weather stations recorded storm force winds and significant wave heights that exceeded the liftboat’s operational limits. Subsequently, on the morning of the 20th, the Robert began tipping to port. A subsequent inspection on November 23 revealed substantial damage, including structural stress fractures, equipment displacement, and bent legs within the leg towers.

Over a two-week period, a response team successfully righted the vessel, jacked up its legs, and towed it back to the port of Amelia, Louisiana, arriving safely in early December. The estimated cost of repairs amounted to approximately $7 million, reflecting the extent of the damage incurred during the incident.

The NTSB’s assessment attributes the vessel’s tilt-over to the transfer of wind and wave-induced stress down the legs to the seabed, where the liftboat’s pads were embedded. The force likely caused the seabed under the port side pad to crumble and shift into a nearby can hole, leading to the leg’s displacement, as determined by the NTSB’s investigation.

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