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Cyclical alternations of sandstone and mudstone at a variety of length-scales cause significant permeability variations in tidal sandstone reservoirs, which makes them difficult to characterize and model. In this study, the geometry and distribution of small- and intermediate-scale tidal heterogeneities and their influence on fluid flow have been investigated using an outcrop analogue from the Eocene Dir Abu Lifa Member (Western Desert, Egypt). The key challenge in modelling such heterogeneities is to accurately reproduce their three-dimensional architecture. We use a novel, surface-based modeling approach, which honours the geometry of geological surfaces and therefore the contacts between laminae, beds and facies units. The technique used in this study directly reproduces three-dimensional surfaces using a purely geometrical approach. Statistical datasets of the distribution, length and continuity of mud drapes and associated geometrical parameters have been collated from high-resolution outcrop photomontages and associated measurements. The modelling algorithm, in conjunction with the quantitative outcrop data, has been used to generate generic three-dimensional models of heterolithic tidal sand bodies. The models are suitable for direct use in flow simulation studies and are currently being applied to characterize the effective reservoir properties and predict fluid flow behaviour in subsurface tidal sandstone reservoirs.

Numerous authors recognized the importance of variations in stretching rates for basin stratigraphy, and several subdivisions of the rift stage into phases were proposed, based on variations in the rate of extension (e.g. Prosser, 1993; Nottvedt et at., 1995; Ravnas and Bondevik, 1996).

A threefold subdivision of the syn-rift infill of extensional half-grabens, relating distinct lithologies and stratigraphic signatures to the temporal rift development was proposed by Prosser (1993). Subsequently Ravnas and co-workers (1994) have argued that a bipartite subdivision is developed more commonly in underfilled and sediment starved rift-basins. The Jack of late syn-rift sandstone cappings is attributed to low sediment supply despite low rates of tectonic subsidence and rotation. These two models can be seen as end-members in a series of syn-rift architectural patterns present in the middle Jurassic-lowermost Cretaceous of the northern North Sea.

The Mesozoic evolution of the northern North Sea has been subject to a lot of research already, and the general rift-basin development is fairly well known (e.g. Badley et.al., 1988; Gabrielsen et.al., 1990). Two periods of rifting are observed, the first one in the Late Permian and Early Triassic, the second one starting in the Early Bathonian (Late Jurassic). The aim of this study is to increase the understanding of the tectonic history of the Eastern part of the northern Viking Graben, i.e. the Oseberg and Brage area, during and after deposition of the Brent Group sediments. We used a numerical model, describing crustal deformation in a faulted region.