Abstract The Laggan–Tormore development was sanctioned in 2010: the two fields are produced by subsea systems, tied back to the Shetland Islands where the hydrocarbons are processed in the Shetland Gas Plant. A key aspect of the Laggan–Tormore development was the inclusion of in-line tees in the flowlines to allow future tie-ins. This paper highlights the opportunities now available for further gas developments West of Shetland and describes the efforts performed by Total and its co-venturers during the period 2010–15 in order to take advantage of the new gas infrastructure. Three exploration wells were drilled by Total and its co-venturers around the facilities during this period. The Tomintoul well turned out to be dry despite a positive amplitude v. offset (AVO) anomaly. Edradour, whilst a gas discovery, was not big enough to make an economical tie-back to the Laggan–Tormore facilities. The third exploration well Spinnaker was disappointing. All undeveloped gas resources around the facilities were evaluated and Glenlivet was clearly the most attractive. Studies demonstrated that a joint Edradour–Glenlivet development would be economical; the Field Development Plan was approved in March 2015 and the Glenlivet development drilling campaign took place during the summer of 2015. Total continues an intensive exploration programme West of Shetland on its wide acreage, hoping to bring additional projects in the future.

Abstract Spectral decomposition analyses seismic reflectivity data in the frequency domain, providing images of the subsurface that complement conventional seismic interpretation. It is a highly visual tool that allows additional value to be extracted from seismic data, to aid in the identification of geological information and to be used in conjunction with more traditional methods such as amplitude extraction and attribute analysis. The methods of spectral decomposition chosen utilized a top reservoir seismic reflection surface, with the selected dominant frequency volumes coloured and recombined in a spatial context to produce various red–green–blue (RGB) blends. Application of spectral decomposition to the Laggan and Tormore fields revealed the varied distribution of turbiditic sands, as well as extensive east–west faults that have previously been inferred from seismic reflection data. These enhanced images of the reservoir provide a more detailed interpretation of the field architecture and have been captured in DONG E&P UK Ltd's own fault and reservoir models, leading to a greater understanding of potential field development outcomes and future well placement decisions. Attempts to distinguish hydrocarbon effects using spectral decomposition proved difficult, although interesting frequency variations around a known gas–oil contact (GOC) were noted.

Abstract Seismic imaging beneath shallow (<5 km) Palaeogene basaltic volcanic successions on the Faroe–Shetland Margin is very challenging with conventional seismic methods. Consequently, the interpretational uncertainty that surrounds the sub-basalt structure of the region is a major source of exploration risk. This study uses gravity and magnetic data in conjunction with seismic data to map the sub-basalt structure of the Faroe–Shetland Basin and model the crustal architecture of this part of the Atlantic margin. Four crustal types are recognized using gravity data: oceanic, intruded transitional, stretched continental and normal continental crust. Map-based interpretation of the gravity and magnetic data helps redefine the basins, highs and faults in the region. The structural interpretation suggests that the boundary between normal and stretched continental crust is coincident with the long-lived left-lateral ‘West Shetland Shear Zone’, which partitioned strain during rifting of the margin. 2D/2.5D gravity and magnetic models are shown for two seismic profiles from the PGS FSB MegaSurveyPlus. The models suggest highly thinned crust, which was intruded by mafic magma beneath the Flett sub-basin, and an asymmetry to the rifting, which is consistent with a process of Wernicke simple shear.