The sequence of events began on the evening of 18 April 2026. The Deepsea Atlantic was running a blowout preventer and riser into the sea when, at around 20:59, one motor on Main Drawworks A tripped. The other three motors tripped in quick succession, causing a loss of control of the drive and main braking system with 646 tonnes hanging on the hook. The BOP and around 400 metres of drilling riser fell to the seabed.

No personnel were injured. The rig was confirmed secure and operations were immediately suspended pending BOP recovery and investigation. Odfjell Drilling subsequently shifted the Deepsea Atlantic from the UK back to Norway, where it underwent repairs at the CCB yard near Bergen.

The UK Health and Safety Executive served Odfjell Drilling with an improvement notice, stating that the Aberdeen-based contractor had failed to ensure the rig’s active heave drilling dual drawworks did not contain single point failures in the braking system. The regulator described the incident as having led to a significant risk of harm to persons from falling debris. Odfjell Drilling had until 15 June to demonstrate compliance with the improvement notice.

In response, Odfjell Drilling said it recognised the notice served by the HSE and was actively engaging with the findings from its regulators. According to Odfjell Drilling’s first quarter 2026 report, the company estimated three to four months before the rig would be ready to return to operations.

The Deepsea Atlantic is a 2009-built sixth-generation deepwater and harsh-environment semi-submersible of enhanced GVA 7500 design. It is a dual-derrick, dynamically positioned unit capable of operating in water depths up to 3,000 metres and drilling to 10,670 metres. The rig is under contract to Equinor until the end of the second quarter of 2027; the contract was originally signed in 2023 and extended in January 2025.

Rosebank lies approximately 130 kilometres northwest of the Shetland Islands in the Faroe-Shetland Channel at water depths of around 1,100 metres. The development plan covers four production wells, three water-injection wells and two plug-and-abandonment wells in the first phase, with produced hydrocarbons to be transported through new subsea flowlines to the refurbished Petrojarl Knarr FPSO for processing and export. Equinor operates the project on behalf of licence partners Equinor UK and Ithaca SP E&P, with the field expected to remain in production for approximately 25 years once drilling operations resume.

The incident and the subsequent repair timeline are understood to mean that some well completions will run significantly behind schedule, with first oil now expected in late 2026 at the earliest and more likely into early 2027.