The Health and Safety Executive served an improvement notice on the energy giant last November after it failed to maintain emergency shutdown valves.
It said Shell had breached the Control of Major Accident Hazards Regulations (COMAH) and the Provision and Use of Work Equipment Regulations by failing to take "necessary measures to prevent major accidents and limit their consequences".
The notice states: "You have failed to put in place adequate arrangements to ensure that emergency shutdown and emergency depressurisation valve actuators on the establishments are maintained in efficient state and effective working order."
A spokesperson for Shell told IOSH Magazine: "Shell UK can confirm that we have been issued with an improvement notice on 23 November 2017 in relation to the maintenance of emergency shutdown valves at our St Fergus plant in North East Scotland. We are working to address the requirements of this notice."
Shell initially had until 21 December to comply with the notice but the deadline has been extended to 28 February.