The Eastern Trough Area Project is an integrated development of nine different reservoirs with differing ownership and operatorship - six separate fields are operated by BP, and a further three fields are operated by Shell. ETAP ranks as one of the largest projects in the past fifteen years. 

The various fields are grouped into six areas called clusters. BP operates the Heron cluster facilities on a day-to-day basis, while Shell remains responsible for any drilling, reservoir intervention or non-routine maintenance.

The whole ETAP area is approximately 35 kilometres wide at its maximum diameter. 

First production from ETAP was in July 1998 with the satellites: Mirren and Madoes, coming on stream via a subsea tie-back and additional platform facilities in 2002.

The additional of the Mirren and Madoes fields means that the facility now handles up to 120 thousand barrels per day oil. In addition, gas produced from each field is exported at around 250 million standard cubic feet per day. Approximately 1100 tonnes/day of natural gas liquids products such as condensate are produced. 

Reservoirs and Facilities

BP's reserves in ETAP lie in its interests in: Marnock, Mungo, Machar, Monan, Mirren and Madoes. These six reservoirs are independent. ETAP is based on the development of a Central Processing Facility (CPF)-consisting of a Processing, drilling and Riser (PdR) platform bridge-linked to a Quarters and Utilities (QU) platform over Marnock and a normally unmanned installation on Mungo. The remaining fields, Machar, Monan, Mirren, Madoes and the Shell operated Heron, Skua and Egret fields all produce through subsea manifolds tied back to the CPF. 

The PdR and QU platforms of the CPF are sited approximately 60 metres apart and are linked by two bridges. This design separates the production risers and Marnock wellheads on the PdR platform from the people on the QU platform. The PdR design also separates the riser area and the Marnock wellheads from a jack-up drilling rig when this is present. 

Produced Water

In order to handle produced water disposal, there are two produced water re-injection wells with provision for a further two re-injectors if needed later. Export Oil is exported through a 76 km 24-inch carbon steel pipeline to Kinneil terminal at Grangemouth via the Forties Pipeline System, accessed at the BP Unity platform. Peak export capacity is approximately 250 thousand barrels per day. 

Gas export is via a 14km, 16-inch carbon steel spur line link to BP's 36-inch Central Area Transmission System (CATS) pipeline to Teesside. The capacity is around 440 million standard cubic feet per day. CATS undertake onshore gas processing, before the gas is sold for commercial use. 

Health and Safety Executive

Safety was at the forefront of designing all facilities for ETAP to the extent that the Health and Safety Executive (HSE) acknowledged the development as being best industry practice. 

BP, as the CPF Operator, operates the Heron Cluster on a day-to-day basis on the instructions of Shell. Under current legislation BP has responsibility as Installation Operator for Shell ' s Heron Cluster. 

Wherever practical, common equipment has been used throughout the ETAP facilities to minimize spares and increase technician familiarity. 

All process systems are operated from a single control room on the CPF. Utilities requiring frequent adjustments, particularly power generation are designed for start-up and operation from the control room. 

Facilities are designed for: ergonomic principles, ease of operation and maintenance, to promote safety and encourage high morale in the workforce. All oil and gas process equipment is capable of being started up, controlled and shutdown from the CPF control room. 

The maintenance strategy is aimed at minimising permanent offshore manning levels. All maintenance work is scheduled and monitored using a computerised maintenance management system.