A subsurface perspective on ETAP – an integrated development of seven Central North Sea fields

In December 1995 the UK Government gave approval to develop the Eastern Trough Area Project (ETAP) – a major new project consisting of the integrated development of seven Central North Sea fields. During the development phase BP will operate four fields (Marnock, Machar, Mungo and Monan) and Shell will operate three fields (Heron, Egret and Skua). On commencement of production in 1998 BP will act as operator of the overall facilities on behalf of the seven co-venturers (BP, Shell, Esso, Agip, MOC Exploration, Murphy and Total). The reservoir architecture, conditions and fluids pose some unique challenges for the project which represents the single largest North Sea development for ten years. The challenges include: downhole sand control in high pressure/high temperature (HP/HT) horizontal wells; management of uncertainty in forecasting target depths in diapir wells; management of uncertainty in long term performance of fractured chalk under waterflood; downhole salt/scale management under HP/HT conditions; management of uncertainty in long term productivity from Skagerrak reservoirs; and well engineering in HP/HT conditions. This paper gives a brief overview of the challenges that ETAP is facing during development of these reservoirs and outlines how these will be addressed during the early field development stage.