The Dunlin Alpha platform was installed in 1977, comprising a concrete gravity base structure (CGBS), supporting a steel topsides deck and production facilities.The infrastructure included Dunlin, Dunlin South West, Osprey and Merlin fields. The Dunlin Alpha platform was constructed on the seabed above the Dunlin field and has served as a production facility for the associated fields. Oil production was exported from Dunlin Alpha via pipeline to the Cormorant A platform, and from there by pipeline to the Sullom Voe oil terminal in the Shetland Islands.
The main Dunlin hydrocarbon reservoir and the Dunlin South West hydrocarbon accumulations were reached from wells located on the Dunlin Alpha platform. As separate reservoirs, the Merlin and Osprey fields were accessed by subsea wells located on the seabed. These fields were ‘tied back’ to the Dunlin A platform by a set of two 8 inch diameter subsea pipelines and control lines. Dunlin Alpha also acted as a pumping station for crude oil imports from the Thistle field, exported via the Dunlin/Cormorant pipeline.
Production from the Dunlin A platform started in 1978, and from Osprey and Merlin in 1991 and 1997 respectively. The Osprey field facilities comprised two subsea drilling templates and a subsea manifold located some 7km north of Dunlin A in water depths ranging from 155m to 165m. The Merlin field facilities comprised three subsea production wells and a water injection well, located 7km west of Dunlin A in water depths ranging from 155m to 165m. A 23km long, 119mm diameter electric power cable ran in a seabed trench from the nearby Shell-operated Brent Charlie platform to Dunlin Alpha, through which available electrical power, generated on Brent Charlie could be supplied to Dunlin Alpha. A 10.2km long, 100mm diameter gas pipeline was installed during 2012 to import fuel gas to Dunlin A from Thistle. The pipeline was trenched and backfilled along its entire length.