Abstract During Late Paleocene–Early Eocene times, the modern Rosebank structure was located at the juxtaposition of the easterly advancing Flett volcanic system and the northerly prograding Flett delta. As a result, the Rosebank reservoir sandstones are interstratified with volcanic and volcaniclastic rocks, offering challenges for reservoir imaging, depth prediction and reservoir characterization. These challenges have driven the application of Ocean Bottom Node (OBN) seismic technology. OBN data have yielded improved velocity models for depth conversion, better reservoir definition and key insights to aid the modelling of sand distribution from seismic attributes. Spectral decomposition of the OBN seismic data has facilitated the extraction of distinct volcanic subunits, whilst spectral enhancement has enabled visualization of complex stacking patterns within individual igneous layers. To complement the seismic analysis, detailed geological analogue studies have been undertaken in volcanic provinces such as the Palaeogene volcanic district of SE Greenland and the Columbia River Flood Basalt Province, USA. No single outcrop provides a definitive analogy to Rosebank, but each offers insights that provide an important link to understanding and managing the main subsurface uncertainties associated with field development. Integration of these multiple workflows have improved the reservoir characterization and provided the foundation for the optimization of the field development plan.

Abstract To date, fractured crystalline basement reservoirs (basement) on the UK Continental Shelf (UKCS) have largely been underexplored, despite the fact that numerous indications of hydrocarbons have been reported from basement in wells dating back to the 1970s. As production from the UKCS continues to decline, and with the exploration potential of more traditional plays becoming increasingly mature, the potential of the overlooked and underrated basement play warrants further exploration. Over the last 10 years, Hurricane Energy (Hurricane) have deliberately set out to explore the potential of this untapped resource, focusing on the Rona Ridge trend, West of Shetland. The Lancaster Field has been penetrated by four wells and benefits from a full 3D seismic survey, and, as such, represents Hurricane's most de-risked basement asset. The level of understanding of the Lancaster reservoir is such that Hurricane is now working towards a phased field development. This paper provides a summary of the geology and reservoir characteristics of the Lancaster Discovery, and a description of the technical progress achieved, to date, in de-risking the Lancaster Field.

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 Tsunami catalogues provide important datasets in assessing the risk from infrequent but potentially high-impact events. Although the UK is located away from subduction zones (the most common origin of tsunamis), tsunamis have struck its shores, most notably those triggered by the prehistoric Storegga submarine landslide and the 1755 Lisbon earthquake. Since the major events of 2004 (Indian Ocean) and 2011 (Japan) tsunamis are in the public psyche, even if the risks to UK coasts are not. Due to this heightened awareness, many reported events are claimed to be tsunamis and the potential for tsunamis is increasingly included in risk planning; understanding the true frequency of tsunamis is therefore important. Within the UK, the evidence for tsunamis includes tide gauge readings, reported visual observations and interpretation of sedimentological features. Catalogues need to consider whether the event is a true tsunami in order to avoid a plethora of claims that confound risk assessments; for example, recent well-documented events generated by weather systems (meteotsunamis) provide a possible explanation for some historical events. A detailed examination of the impact of tsunamis upon the UK coast is provided, including examples of events triggered by the three primary causes of tsunamis: seismicity, submarine landslides and coastal landslides.