An Early Cretaceous lithostratigraphic and biostratigraphic framework for the Britannia Field reservoir (Late Barremian–Late Aptian), UK North Sea

A Lower Barremian–Upper Aptian lithostratigraphic scheme applicable to the Britannia Field (Blocks 15/29, 15/30, 16/26 and 16/27) is presented. The Britannia Sandstone Formation reservoir is formally subdivided into three members (type well 15/30-9); the Lapworth (Late Barremian to Early Aptian), Kilda (Late Aptian) and Bosun (latest Aptian) members. The Lapworth Member is subdivided into three units, Lapworth ‘A’ (Late Barremian), the intra-Fischschiefer Lapworth ‘B’ (intra-Early Aptian) and Lapworth ‘C’ (Early Aptian).

The Early Barremian to Early Aptian upper Valhall Formation is subdivided into seven units: ‘V3A’ the Hauptblatterton, ‘V3B’, ‘V3C’, ‘V3D’, Fischschiefer Bed, and ‘V4’. The overlying Sola and Rodby Formations are subdivided into Units ‘S1’ and ‘S2’ of the ‘Lower’ Sola Formation (Late Aptian), plus Units ‘S3’ and ‘S4’ of the ‘Upper’ Sola Formation (Early Albian). The Rodby Formation (Middle? to Late Albian) is subdivided into three units: ‘R2’, ‘R3’ and ‘R4’.

A high resolution biostratigraphic zonal scheme is defined for the Early Barremian to earliest Albian interval, utilizing calcareous nannoplankton, micropalaeontology and palynology. Within this, 49 zones and 38 subzones (12 microfaunal zones and 4 subzones, 23 palynological zones and 19 subzones, and 14 nannoplankton zones and 15 subzones) are recognized. Of these, 5 micropalaeontological zones (and 4 subzones), 11 palynological zones (and 15 subzones) and 7 calcareous nannoplank-ton zones (and 10 subzones) are directly applicable to the Britannia reservoir section.