Fairfield Energy has announced plans to shut its Dunlin Alpha platform in the North Sea due to low oil prices, as well as challenging operational conditions.
Set to cost about £400m, the decommissioning process requires regulatory approvals.
Located nearly 200km north-east of the Shetland Isles, the platform processes production from the main Dunlin field and the Osprey and Merlin subsea fields.
Fairfield Energy holds the majority 70% stake, with the remaining 30% owned by Mitsubishi.
Starting in June, the company will close production from all Dunlin cluster fields, which include the Dunlin A platform, Dunlin South-west, Merlin and Osprey fields.
"Taking into account the asset's lifecycle, the depressed oil price and challenging operational conditions in the North Sea, starting the decommissioning process is the most appropriate action."
Production commenced in August 1978, and the Dunlin field produced around 120,000 barrels per day in the year 1979.
Previously operated by Shell, the oilfield is situated 300 miles north-east of Aberdeen in the East Shetland basin.
In 2008, Fairfield acquired the Dunlin, Dunlin SW, Merlin and Osprey fields.
The company decided to decommission the platform as it has achieved maximum economic recovery.
Fairfield Energy chief executive David Peattie said: "Taking into account the asset's lifecycle, the depressed oil price and challenging operational conditions in the North Sea, starting the decommissioning process is the most appropriate action.
"Our investment programme has prolonged the life of Dunlin leading to a notable contribution to the British economy and the creation of jobs in North Sea oil and gas. "