Deep-Water Reservoir Facies of the Jurassic Buzzard Field, North Sea, United Kingdom

Graham Dore and Chris Forster
Nexen Inc, Uxbridge, United Kingdom

The selection of core from the Buzzard Field includes samples of some of the depositional facies from over 1200 ft of core acquired in six exploration/appraisal wells across the field. The reservoir interval largely comprises Late Jurassic age, base of slope, gravity flow sandstones. The structureless sandstones and laminated sandstones (that can be observed in Well 20/6-3) are typical of the main reservoir ('Buzzard 4') interval and are commonly tens of metres thick comprising amalgamated, homogeneous sandstones. Within the structureless sandstones the primary structure may have been erased by dewatering. These are interpreted as stacked turbidites that have undergone rapid deposition from surge-like flows. The thick laminated sandstone intervals contain thin, dark bituminous bands that highlight subtle variations in grain size, grain packing density and grain orientation on a centimetre to millimetre scale. These are interpreted as sustained turbidites or hyperpycnites that are indicative of continual sedimentation in a near-slope depositional setting (possibly related to river flooding). Sandier facies are interbedded with structureless and laminated mudrocks, suggesting the accumulation of hemipelagic sediments and dilute mud-rich turbidity currents respectively. Several calcite cemented intervals are also seen in the core representing doggers with little lateral continuity. Core from Well 20/6-5 illustrates the Buzzard Field OWC. The field has an estimated hydrocarbon column of 1400 ft.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005