Gannet Cluster: Development After the 1986 Oil Price Collapse
Authors: Carter J.H.T. , Muster Albert , Skinner Bruce 
Published: October 2008

The original Gannet Project comprising five hydrocarbon accumulations in the Central area of the North Sea was under development at the time of the 1986 oil price collapse, at which point it was cancelled. Following redesign and stringent cost reduction, based on a simplified facilities concept, Kittiwake, the most productive and least complex of the five fields, was reinstated as a stand-alone development and is now operational. Adopting similar design strategies three of the remaining four original Gannet fields together with a further discovery made in 1987 are now being developed, central on Gannet A platform in a water depth of 95 metres with subsea satellites at Gannet B, Gannet C and Gannet D. The development of these four fields is for recoverable reserves of 170MM bbl of oil and condensate and substantial gas reserves of 704 BCF. First hydrocarbon deliveries are scheduled for October 1992.

In addition to the extensive use of subsea development, other strategies were adopted to minimise capital expenditure and operating costs. These included:-(available in full paper)

By end 1991 the Gannet A jacket and 330km ofsubsea pipelines were installed, and development drilling had commenced. Construction activities for the integrated deck are on schedule for installation in second quarter 1992. The cluster approach and stringent cost control has facilitated the economic development of the field under the UK tax regime at oil price scenarios at the lower end of expectations.

BACKGROUND

The original Gannet Project comprising five hydrocarbon accumulations in the Central Area of the North Sea (CNS) was under development at thetime of the 1986 oil price collapse, at which point the project was cancelled. A North Sea situation Map of the UK is provided in Fig. 1 and a more detailed Field Location Map of the CNS in Fig.2. At this time the Gannet development consisted of 5 fields -3 Gannet fields, Kittiwake and Guillemot. The plans were based on cluster development with standalone, modular installations provided with steel jackets and self-sufficient drilling modules, but including one subsea gas development with 4 wells.

After the 1986 oil price collapse the introduction of new concepts was critical for economic viability. Kittiwake, the most productive and least complex ofthe five fields and the furthest away from the other fields was developed separately as a stand alone project utilising the concepts of an integrated deck and single lift installations of the jacket and topsides. For the development of the remaining fields to be commercially viable it was essential to find more cost effective engineering solutions for the extraction, processing, and evacuation of the reserves. It was also necessary to avoid reservoirs with too diverse recovery mechanisms and to ensure that each reservoir was justified on an incremental basis. Extensive reviews led to the decision not to include accumulations at Guillemot, the only reservoir needing water-injection. This led to thepreparation of development plans for Gannet A, B, C and a new discovery made in 1987, Gannet D.