--> ABSTRACT: Contrasting Styles of Facies Architecture in Mixed Eolian/Fluvial Deposits - Hoton and South Ravenspurn Fields, UK, Southern North Sea, by M. L. Sweet; #91021 (2010)

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Contrasting Styles of Facies Architecture in Mixed Eolian/Fluvial Deposits - Hoton and South Ravenspurn Fields, UK, Southern North Sea

SWEET, MICHAEL L.

The Permian Rotliegend Group, the primary gas reservoir in the UK Southern North Sea, records a variety of arid climate, nonmarine environments. Because the eolian facies are the main flow units and fluvial facies are, in general, of poor reservoir quality the distribution and continuity of aeolian and fluvial deposits is a key factor controlling well performance. Hoton and Ravenspurn Fields because of their different tectonic and sedimentologic settings illustrate the range of depositional styles in a mixed eolian/fluvial sequence.

Hoton Field lies just down dip of a major basin-bounding fault system. A relay zone in this fault system focused fluvial systems into the area around Hoton Field through a substantial portion of Rotliegend deposition. Compared to other nearby fields fluvial (wadi) facies are coarse grained. Correlation of closely spaced wells reveals a history of fluvial incision and deposition interspersed with periods of aeolian activity and reworking of finer grained fluvial deposits. In this setting tectonics and variation in fluvial discharge have create a complex mosaic of eolian and fluvial deposits that show rapid lateral and vertical facies changes.

In contrast, South Ravenspurn Field is located further down depositional dip. Fluvial deposits are characteristically finer grained and have a high abundance of terminal fan facies. While fluvial incision and wind erosion can be documented the balance between the rate of water table rise or fall and the sediment supply seems to exert a greater control on sand body geometry. The resulting fluvial and eolian deposits are more laterally extensive than those in Hoton.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.