Abstract The UK Rockall Basin is one of the most underexplored areas of the UK Continental Shelf (UKCS), with only 12 exploration wells drilled since 1980. With only one discovery made in 2000 (Benbecula (154/1-1) gas discovery), the general view of the basin from an exploration viewpoint is not positive. However, over the last 15 years, our knowledge of the petroleum systems of the Atlantic Margin has substantially increased. With the recent acquisition of new seismic data by the UK Government as part of the OGA's Frontiers Basin Research Programme, it is a pertinent time to re-examine the prospectivity of the UK Rockall Basin. This paper presents a history of exploration within the UK Rockall Basin, from the first well drilled in the basin in 1980, to the last well, drilled in 2006. We then present new insights into the lack of success during exploration within the basin, in particular by focusing on the extensive Early Cenozoic volcanic rocks within Rockall, to illustrate the wide range of potential interactions with the petroleum system. We also present evidence that points to the potential of a viable intra-basaltic (Rosebank) type play along the eastern flank of the Rockall Basin.

Abstract This study presents an integrated seismic, well and core-based analysis of the Maureen Formation in the Central Graben of the North Sea. Facies analysis reveals that it is possible to divide the Maureen sandstones into amalgamated, sand- and mud-prone divisions, but that the related chalk facies are complex and imply a range of depositional processes including pelagic fallout, debris flows and turbidity currents. These chalk deposits have an impact on the interpretation of amplitude-based seismic attribute volumes. Detailed petrophysical mapping, supported by seismic analysis, reveals that the Maureen sandstones were deposited in distinct western and eastern fairways controlled by the relict Mesozoic rift topography (although offset stacking is an important intragraben process). The spatial extent of the Maureen sandstones is similar to the overlying Sele and Lista formations and suggests that the broad controls on sediment routing were the same throughout the Lower Palaeogene. Other similarities between these systems include the role of sandstone texture in controlling reservoir quality (although the heterolithic nature of the Maureen sandstones means that porosities and permeabilities are lower). A pattern of intraformational progradation and late-stage backstepping of the sandstone units is likely related to sea-level variability.

Abstract The Tambores alluvial fan is located within the hyper-arid Atacama Desert of northern Chile. We examine evidence of the range of flow processes operative in this environment from a combination of Pleistocene–Holocene fan deposits and a recent (2001) flood event (16 m 3 s –1 ) in the fan feeder channel and upper alluvial-fan area. The field evidence suggests that peak flows recorded in the older deposits generated extensive sheetflood events dominated by antidune deposition in the upper fan area. These extreme, supercritical flows were generated by floods with sustained high sediment and water discharges and high stream power. Easily erodable alluvial source materials ensured high sediment discharge could be maintained within flood events. High stream power was ensured as a function of the tectonically exacerbated gradients within the source area. The 2001 event indicates the rapid rheological changes that can occur within an individual flood event, ranging from hyperconcentrated streamflow to mudflow. The flow deposits vary little in maximum clast size either between the varying flood events in the upper fan area, or down the fan gradient. This is due to a limited calibre of sediment being produced from the source area. The study highlights: (1) the range of flow rheologies that can be generated from a hyper-arid catchment both within and between flood events of varying magnitude and the associated difficulties in generating a reliable stratigraphy from the resultant deposits; (2) the high stream power and sediment discharge associated with major flood events and thus the nature of flood hazard in the catchment and on the fan; and (3) the limitations of sedimentological information such as maximum clast size as an indicator of peak flow characteristics in ancient deposits.