Andrew Pulham1, T. Saunders2, S. George Pemberton2
(1) University of Colorado, Boulder, CO
(2) University of Alberta, Edmonton, AB
ABSTRACT: Anatomy of a Transgression in a Rift Embayment: Bruce Field, Middle Jurassic, Northern North Sea, UK
Producing sandstones in the Bruce Field include a thick section of Middle Jurassic, syn-rift, lower delta plain, nearshore and restricted marine environments that were deposited during a regional, north to south transgression of the Viking Graben. The nature of this transgression in the Bruce area has been described and interpreted through the use of quantitative biostratigraphy and ichnofacies analysis combined with sedimentological and petrographic studies and the use of dynamic data such as RFT pressures and PLT production logs. The architecture of the Bruce reservoirs can be linked directly to the nature of the regional transgression. Of particular importance are changes in sediment supply that occur through time and the interplay between contemporaneous faulting and the palaeogeography of the local rift basin. The most important stratigraphic event is a key marine flood that resulted in the deposition of a laterally extensive and high permeability sandstone across large parts of the field area. The second most important stratigraphic event is related to an interpreted period of tidal amplification in the rift basin that resulted in the incision of deep tidal channels containing high quality reservoir facies. Reservoir facies are dominated by clean, cross-bedded, medium grained to coarse grained sandstones. Physical sedimentology does not allow details of the depositional setting to be fully realised. Only integration with the biostratigraphic and ichnological observations allow a picture of the stratigraphic evolution of the syn-rift deposits to be constructed.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado