Application of high-resolution sequence stratigraphy to northwest Hutton Field, northern North Sea: implications for management of a mature Brent Group field

The Middle Jurassic Brent Group reservoirs in Northwest Hutton comprise shallow-marine, marginal-marine, and coastal-plain reservoir sandstones of both channelized and sheet geometries. The connectivity and production characteristics of these sandstones can be predicted through the application of high-resolution sequence stratigraphic correlation techniques. The Broom Formation overlies a basal Brent sequence boundary and is a lowstand to transgressive systems tract tidal-estuarine complex. The overlying Rannoch Formation comprises shoreface sands that represent a highstand systems tract. The overlying Etive Formation is a multilayer fluvial to estuarine channelized system of near fieldwide development interpreted as incised valley fills. The superjacent Ness Formation is genetically related to the Etive and is the main oil-bearing interval over much of the field. The Lower Ness comprises mouth-bar parasequences and is interpreted to be a transgressive systems tract to the Etive lowstand. The Upper Ness is a nonmarine delta plain succession, interpreted as a highstand systems tract. Upper Ness channel sands typically correlate between several wells and are oriented west-east. An interval of widespread, stacked channels indicates a change in drainage orientation and is related to a high-frequency relative sea level fall. The uppermost reservoir unit is the Tarbert Formation, related to a further major sequence boundary. Original repeat formation tester data support a stratigraphically well-connected reservoir model. Compartmentalization exists and is due to stratigraphic layering (laterally persistent mudstones creating low vertical permeability) and variable dimensions of channels and valley fills.