Gannet Site and Piperoute Surveys — An Integrated Interpretation

Abstract

The Gannet Development in the Central North Sea, consists of a platform, seven subsea developments and associated infield and export pipelines.

This paper provides a case history of the site survey aspects of the field development. It describes the advantages of a carefully planned, comprehensive site survey programme and also the advantages of a detailed integration of all available data to provide a reliable interpretation of geophysical data. This is of particular importance in an area such as Gannet where there is shallow gas and highly variable shallow soils.

Several seabed surveys and site investigations have been undertaken in the Gannet area over the last ten years. These commenced with reconnaissance surveys in the early eighties. As the field development plans were finalised, a programme of detailed seabed surveys and site investigations was established, supplemented by a shallow gas pilot hole.

Interpretation of the seismic data required careful integration of all the data sets. The result of this interpretation was a good understanding of the shallow soils and shallow gas within the area.

Shallow gas prognoses were made for all the proposed locations and to date these have been confirmed by wells at five of the locations.

Piling and anchoring conditions have been confirmed at the platform and drilling centre locations and trenching conditions for the pipelines were as predicted.