Many shoreface sandstone reservoirs host significant hydrocarbon volumes within distal intervals of interbedded sandstones and mudstones. Hydrocarbon production from these reservoir intervals depends on the abundance and proportion of sandstone beds that are connected by erosional scours, and on the lateral extent and continuity of interbedded mudstones. Cliff-face exposures of the Campanian 'G2' parasequence, Grassy Member, Blackhawk Formation in the Book Cliffs of east-central Utah, USA, allow detailed characterization of 128 erosional scours within such interbedded sandstones and mudstones in a volume of 148 m length, 94 m width and 15 m height. The erosional scours have depths of up to 1Á1 m, apparent widths of up to 15Á1 m and steep sides (up to 35°) that strike approximately perpendicular (N099 AE 36°) to the local north-south palaeoshoreline trend. The scours have limited lateral continuity along strike and down dip, and a relatively narrow range of apparent aspect ratio (apparent width/depth), implying that their three-dimensional geometry is similar to non-channelized pot casts. There is no systematic variation in scour dimensions, but 'scour density' is greater in amalgamated (conjoined) sandstone beds over 0Á5 m thick, and increases upward within vertical successions of upward-thickening conjoined sandstone beds. There is no apparent organization of the overall lateral distribution of scours, although localized clustering implies that some scours were re-occupied during multiple erosional events. Scour occurrence is also associated with locally increased amplitude and laminaset thickness of hummocky cross-stratification in sandstone beds. The geometry, distribution and infill character of the scours imply that they were formed by stormgenerated currents coincident with riverine sediment influx ('storm floods'). The erosional scours increase the vertical and lateral connectivity of conjoined sandstone beds in the upper part of upward-thickening sandstone bed successions, resulting in increased effective vertical and horizontal permeability of such intervals.

Distal intervals of interbedded sandstones and mudstones in shallow-marine, wave-dominated shoreface and deltaic reservoirs may contain significant hydrocarbon resources, but their reservoir properties are difficult to predict. Relatively small-scale (200 m x 100 m x 20 m), three-dimensional object-based reservoir models conditioned to outcrop analogue data have been used to investigate the controls on the proportion of sandstone, the proportion of sandstone beds that are connected by sandstone-filled erosional scours, and the effective vertical-to-horizontal permeability ratio (kv/kh) of such intervals. The proportion of sandstone is controlled by sandstone-bed and mudstone-interbed thickness, and by parameters that describe the geometry, dimensions and lateral-stacking density of sandstone-filled scours. Sandstone-bed connectivity is controlled by the interplay between the thickness of mudstone interbeds and sandstone-filled erosional scours. Effective kv/kh is controlled by the proportion of sandstone, which represents the effects of variable distributions and dimensions of mudstones produced by scour erosion, provided that scour thickness is greater than mudstoneinterbed thickness. These modelling results provide a means to estimate effective kv/kh at the scale of typical reservoir-model grid cells using values of mudstone-interbed thickness and proportion of sandstone that can potentially be provided by core data.

The reservoir properties of distal lower shoreface and distal wave-dominated delta-front deposits, which consist of sandstone beds with locally scoured bases and mudstone interbeds, are poorly understood. The lower Rannoch Formation (Middle Jurassic Brent Group) forms an interval of such heterolithic sandstones in many North Sea reservoirs, and is used to illustrate a workflow for rapid estimation of reservoir properties and their sensitivity to key parameters. Mudstone-interbed thickness distributions in cored reservoir successions are compared to the thickness distribution of sandstone scour-fills in an outcrop analogue(s) in order to identify mudstones with the potential to form laterally extensive barriers to vertical flow. Effective kv/kh at the scale of several typical reservoirmodel grid cells (200 x 100 x 20 m) is estimated in intervals bounded by these mudstone barriers via a simple analytical technique that is calibrated to previously documented reservoir-modelling experiments, using values of sandstone proportion measured in cored reservoir successions. Using data from the G2 parasequence (Grassy Member, Blackhawk Formation, east-central Utah, USA) outcrop analogue, mudstones bounding 3-8 m thick, upward-coarsening successions in the lower Rannoch Formation may define separate stratigraphic compartments in which grid-cell-scale effective kv/kh is estimated to be 0.0001-0.001 using a streamline-based analytical method.

The timing of hydrocarbon maturation has an important implication for deeper hydrocarbon prospecting. Results from a series of basin models for the North Celtic Sea Basin display the implications of structural evolution on the timing of hydrocarbon maturation, charge history and trap formation, sealing potential, remigration, and phase change. This study adds to previously published works, which were based on 1D modeling, by generating 2D models using PetroMod TM software. Seismic data have been used to reconstruct the regional structural framework, while the integrated wireline logs and geochemical data provided lithological, porosity, and palaeothermal information. The palaeothermal values and available vitrinite re lectance data have been used to calibrate the models to present day heat low of 52mW/m 2 . Results from this study show that hydrocarbon maturation, generation, and migration were affected by the Triassic and Late Jurassic rifting activities, resulting in a complex charge history and trap modi ication through time. The Late Jurassic source rocks (PurbecK) attained peak maturation for oil in late Cretaceous while the Early Jurassic Source rocks (Liassic and Toarcian) entered the gas window in Early Cretaceous. Analysis of the petroleum systems for deeper hydrocarbon prospecting suggests that two expulsion phases of hydrocarbons occurred in the Late Jurassic and Early Cretaceous respectively. This result suggests that there is potential for charge of suitable reservoir facies at depth if the reservoir quality can be preserved. Hydrocarbon preservation risk is low in anticlinal structures but there is a high risk of hydrocarbon remigration along modiied fault planes in fault-dependent structures. The study demonstrates how basin geometry has changed through time, due to multiple tectonic events, leading to modi ication of older traps.