Print this pageContrasting 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.