A reservoir-scale structural reappraisal of onshore Devonian analogues of the Clair Group in the Fair Isle-Shetland region
The Clair Field, situated to the west of Shetland, represents the largest hydrocarbon resource in the UKCS and is comprised of fractured Devonian-Carboniferous sandstones that overlie an up-faulted ridge of fractured Precambrian metamorphic basement. The onshore, broadly extensional Orcadian Basin has long been used as an analogue for the Clair Field but it is possible that it formed in a rather different tectonic setting, as it lies in a separate basin to the west with some significant differences. In particular, some of the known complexity in the sub-surface structures, and basement-cover relationships may suggest that strike-slip tectonics played a role in the evolution of the Clair Basin during the Devonian-Carboniferous period.
The project will reappraise the stratigraphy, structure and tectonic evolution of an alternative onshore analogue to Clair, using the Devonian basins/sub-basins of Fair Isle-Shetland-Foula region as an analogue for the Palaeozoic tectonics during basin development and later Mesozoic reactivation. This will be achieved through detailed studies of exposed basement-cover contacts and the structure of the overlying sandstone-dominated sequences exposed in large coastal sections.
Fieldwork data will be presented, focusing on the geology and structures of Foula, the Walls Peninsula, Lerwick and Sumburgh with detailed mapping of key localities in the Devonian sequences and associated basement.
Fieldwork will be supplemented by the use of photogrammetry and terrestrial LiDAR to capture the geology of key localities and allow for analysis of structures in difficult to access areas. 3D models of the stratigraphy and structure will be created for use in numerical simulations of fluid flow, modelling of fracture networks, up-scaling and reservoir quality studies. Sampling for heavy mineral analysis will also be carried out in order to determine the provenance and age of the Devonian sequences of Foula and Shetland. All these findings will be compared to previous analogue studies and applied to the current information and models which concern the stratigraphic and structural architecture of the Clair field and its regional tectonic setting.