The Rosebank Field is located in the Faroe-Shetland Basin and hosts hydrocarbons within siliciclastic sediments interlayered with volcanic packages of the Late Paleocene to Early Eocene aged Flett Formation. Within this study the volcanic sequences are investigated based on an integrated appraisal of available drill cuttings, sidewall cores, core and wireline logs including image log and geochemical logs from eight wells supported by 3D seismic data. The Rosebank lower (RLV), middle (RMV) and upper (RUV) volcanic sequences are inter-layered with Colsay Member (C1–C4) fluvial to shallow marine siliciclastic intervals. A comprehensive cross-field borehole based lithofacies interpretation is presented characterising simple, compound and ponded effusive lava flow facies along with pillow lavas, invasive lava flows, volcaniclastic sediments and complex lava–sediment interactions. Geochemical analyses of core, sidewall core, and hand-picked cuttings spanning the field reveal separate high-titanium (RHT) and relatively lower-titanium (RLT) basaltic magma suites. These compositions can be identified and correlated across much of the field utilising geochemical logging data which, in combination with the geochemical analyses, reveals a two-part stratigraphic sub-division of each of the RLV, RMV and RUV. Geochemical logging data is also used to define a volcanic proxy (Fe/10+Ti) which utilises the elevated iron (Fe) and titanium (Ti) within all effusive and volcaniclastic basaltic lithologies to differentiate siliciclastic from volcaniclastic sediments where other logging parameters overlap. By comparing the borehole analyses with seismic data, a localised eruptive vent is interpreted within the north of the field. Finally, a cross-field volcanic model is presented and compared with relevant global field analogues, providing a constrained spatial framework for sub-surface modelling of inter-volcanic sequences.
Bibliographical noteFunding Information:
The Rosebank Joint Venture Project (Equinor UK Limited, Suncor Energy UK and Siccar Point Energy Limited) is thanked for project funding and permission to publish this paper. Jana Ólavsdóttir, Alan Bischoff and Kirstie Wright are thanked for insightful reviews that substantially improved the paper, and Craig Magee is thanked for editorial handling. In addition, Louise Duncan, Tim Watton, Ian Sharp, Mark Wood and John Still are all thanked for insightful discussions and technical support at different stages of the project. Electron Microscopy was performed in the ACEMAC Facility at the University of Aberdeen. Cambridge Carbonates are thanked for access to microscopy facilities while Chemostrat and Integrated Petrographic Services are thanked for chemical analyses and thin section preparation respectively. DAJ and SP are partly funded by the Research Council of Norway Centre of Excellence funding scheme (project 223272).
Data Availability StatementData availability: Data that support the findings of this study are available in the online appendix.
Supporting information: Additional supporting information may be found online in the Supporting Information section.
- core analyses
- geochemical correlation
- Rosebank Field
- volcanic lithofacies
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John Still (Manager)Geology and Geophysics
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