An investigation by the Health and Safety Executive found deficiencies in Shell’s safety management system, including the failure to remove or properly maintain the return oil line pipework inside concrete leg column four, which was installed for short-term use and should have been removed in 2010 but remained for seven years.

The same inquiry linked the release to these safety-management failures and the ongoing presence of temporary spools that were never removed as planned.

About 176 staff on the rig faced an explosion risk, though the probability of ignition was assessed at under 1%; no injuries occurred.

Prosecutors and the HSE emphasized industry-wide lessons on vigilant maintenance and robust safety controls for offshore operations.

Ventilation fans meant to mitigate hydrocarbon release were not properly maintained, increasing the danger and potential scale of the incident.

The inadequate maintenance of ventilation systems contributed to the scale of the release and the risk of a catastrophic explosion.

An inspector highlighted confined-space risks and the potential for asphyxiation in addition to fire and explosion hazards.

Shell UK admitted two charges under Offshore Installations Regulations, acknowledging preventive measures did not adequately address corrosion and maintenance history.

Production was halted and 31 non-essential personnel were evacuated as a precaution after the incident.

The May 2017 release involved 200 kilograms of gas and 1,550 kilograms of crude oil, the largest hydrocarbon release reported to HSE that year, risking explosion and asphyxiation to hundreds of workers.

Shell stated that emergency procedures were followed, no injuries occurred, and measures have since been implemented to prevent recurrence.

Shell was fined 560,000 pounds by Aberdeen Sheriff Court for seven years of neglected pipework maintenance on the Brent Charlie North Sea platform, tied to the major hydrocarbon release in 2017.