Coordinates: 57°24′54″N 2°15′22″E / 57.415°N 2.256°E The Eastern Trough Area Project, commonly known as ETAP, is a network of nine smaller oil and gas fields in the Central North Sea covering an area up to 35 km in diameter. There are a total of nine different fields, six operated by BP and another three operated by Shell, and together, they are a rich mix of geology, chemistry, technology and equity arrangements.
The ETAP complex was sanctioned for development in 1995 with first hydrocarbons produced in 1998. The original development included Marnock, Mungo, Monan and Machar from BP and Heron, Egret, Skua from Shell. In 2002, BP brought Mirren and Madoes on stream. With these nine fields, the total reserves of ETAP are approximately 490 million barrels (78,000,000 m3) of oil, 35 million barrels (5,600,000 m3) of natural gas condensate and 2 billion cubic feet (57,000,000 m3) of natural gas.
A single central processing facility (CPF) sits over the Marnock field and serves as a hub for all production and operations of the asset including all processing and export and a base for expedition to the Mungo NUI. The CPF consists of separate platforms for operations and accommodation linked by two 60 m bridges. The Processing, drilling and Riser platform (PdR), contains the process plant and the export lines, a riser area to receive production fluids from the other ETAP fields and the wellheads of Marnock. The Quarters and Utilities platform (QU) provides accommodation for up to 117 personnel operating this platform or travelling onwards to the Mungo NUI. This partitioning of accommodation and operations into two platforms, adds an extra element of safety, a particular concern for the designers coming only a few years after the Cullen report on the Piper Alpha disaster.