The Triassic Skaggerak Formation is one of the main reservoirs in the high pressure–high temperature province of the North Sea. Production to date has come from fields located on the intra-basinal highs within the Central Graben, between 10 000 and 15 000 ft TVDss. Undrilled prospectivity has been recognized in structural traps in the deeper parts of the Central Graben up to 20 000 ft TVDss, yet reservoir effectiveness remains a key risk. Therefore, in order to optimize future exploration, appraisal and development programmes, it is necessary to consider the likely reservoir performance and production behaviour of these deeper Skaggerak prospects. The Skagerrak Formation comprises two main reservoir sandstones, the Judy Member and the overlying Joanne Member, separated by a thick shale interval, the Julius Member mudstone (Goldsmith et al. 2003). The two reservoirs show markedly different production behaviour despite their apparently similar character on wireline logs. Integration of the production behaviour from the Jade and Judy fields with the sedimentology has enabled the causes of this different production behaviour to be better understood, allowing the controls on reservoir flow to be modelled in both a static and dynamic environment. The understanding of the reservoir behaviour in the currently producing fields has been carried through to a predictive phase of simulation and modelling to determine the range of production behaviours expected for a deeper exploration portfolio. A clear porosity–depth trend exists within the Skagerrak Formation and this has been used to translate the robust history-matched reservoir models from the producing fields to the depth of the prospects. Sensitivity to fluid, porosity–depth trend and permeability of the deep reservoirs have been tested, and a range of likely production rates and behaviours established.