The Faroe-Shetland Basin, NE Atlantic continental margin, hosts a number of important hydrocarbon fields, though deep water and narrow weather windows mean drilling costs are considerably higher than other parts of the UK Continental Shelf. Any additional drilling complications are therefore important to predict and negate as such issues can result in avoidable multi-million pound cost implications. This study focuses on the Corona Ridge, an intra-basinal high which contains the Rosebank Field, where a plethora of drilling issues, of enigmatic origin, are common within a key stratigraphic marker known as the Balder Formation. Drilling fluid loss, bit balling, wellbore breakouts, and wellbore “ballooning”, where lost drilling fluid returns to the wellbore, are all recognised within the Balder Formation along the Corona Ridge. We find that many of the drilling incidents can be traced back to both the lithological character of the Balder Formation, and the mid-Miocene tectonic inversion of the Corona Ridge. Moreover, we find that this geological explanation has wider implications for exploration in the region, including mitigation of drilling incidents in future wells through drill bit selection.
Bibliographical noteThis work forms part of the lead author’s PhD research, which is funded by a University of Aberdeen College of Physical Sciences Scholarship. This study originally formed part of a talk delivered to the 2017 Schlumberger SIS Forum. Well log and drilling data interpretation was performed using Schlumberger Techlog* wellbore software platform. We would like to thank numerous staff at Schlumberger SIS in Aberdeen for useful discussions. DW would also like to thank staff at Chevron’s Aberdeen office for important insights on the Rosebank Field, particularly the presence of image logs. Andrew Hurst is thanked for informative discussions regarding smectite clays and their origins. Finally, DW would like to thank members of the VMRC Consortium for helpful feedback on a presentation related to the study, particularly staff at Siccar Point Energy. Two anonymous reviewers are thanked for their detailed reviews which greatly improved the paper.
- HYDROCARBON EXPLORATION
- IGNEOUS PROVINCE