Eastern Trough Area Project
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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.
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[edit] Development
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.
Liquids are exported to Kinneil at Grangemouth through the Forties Pipeline System. Gas is exported by the Central Area Transmission System to Teeside.
Apart from Mungo, which has surface wellheads on a NUI, all other fields use subsea tie-backs.
A tenth field, Fidditch, is currently under development by BP.2007 has been put on hold.
[edit] ETAP fields
[edit] Marnock
Marnock is a high pressure, high temperature gas condensate field with initial reservoir pressure of 9000psi. Estimated recoverable reserves are 600 billion scf and 50 million barrels (7,900,000 m³) of condensate. Marnock produces directly to surface wellheads on the CPF. It is operated by BP in partnership with Shell, Esso and AGIP.
[edit] Mungo
Mungo is an oilfield with a natural gas cap. Water and gas injection are used to manage the reservoir, which necessitated a small normally unmanned installation be built to support these facilities. The NUI is tied back to the CPF. The field is operated by BP in partnership with Nippon Oil, Murphy Oil and Total S.A..
[edit] Monan
Monan is a small turbidite oil and gas field produced under natural depletion using subsea manifolds. Its production fluids are fed into the pipelines connecting Mungo to the CPF. The field is operated by BP in partnership with Nippon Oil, Murphy Oil and Total S.A..
[edit] Machar
Machar is an oil field in a chalk reservoir. Originally, the half dozen wells produced under natural depletion but modifications are being made to include the capacity for gas lift. The field is solely a BP possession.
[edit] Mirren and Madoes
These two were later additions to the ETAP complex. Mirren is an oil field with a gas cap in the Paleocene structure. Madoes is a light oil field located in the Eocene rock. Both are subsea tiebacks to the CPF, with the capacity for gas lift in the future to aid production. They are both operated by BP with Nippon Oil, Shell, Esso and AGIP.
[edit] Heron, Egret and Skua
These fields are high temperature, high pressure oil producing wells. They are subsea tiebacks to the CPF, but also include produced water reinjection wells for disposal of produced water from Machar and Heron. All three fields are operated by Shell in partnership with Esso.
