Hydrodynamic activity and tilted oil-water contacts in the North Sea

The position of the oil-water contact (OWC) in a prospect or field is one of the most important factors in determining reserves. In the central North Sea, OWCs in the Cretaceous Chalk Group and in Paleocene sandstones can be naturally tilted by bed-parallel hydrodynamic activity as the Central Graben dewaters. Examples of fields with interpreted tilted OWCs are described, and set within their regional hydrodynamic context. In addition, laboratory experiments and computer simulations are used to examine the response of fluid contacts to aquifer heterogeneity in a hydrodynamic environment. These models can be used predictively, improving the understanding of tilted OWCs in fields, helping to explain dry wells and to improve planning and risk analysis for both exploration and development drilling.

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