Claymore Field, North Sea: Integrated Seismic Stratigraphy, Depositional Models and Reservoir Mapping

Venkatarat Kolla, Andrew F. Gordon, and Robert Cooper

Delineation and mapping of reservoir compartments within Northern Area Claymore (NAC) has proved difficult to reconcile with reservoir engineering data. An integrated seismic stratigraphy study was undertaken to solve this problem. Four seismic units (I to IV) were identified and mapped from a 3-D seismic dataset over NAC within the Valhall Formation, between the Base Cretaceous Unconformity and the near top reservoir seismic event. Time-isopach maps, seismic fades, log and core data were integrated to infer sediment fairways and depositional models. The latter, plus time isopachs and well data, were then used to provide a framework to generate reservoir maps (gross, net:gross, porosity) for input into the NAC reservoir simulation model and ultimately for optimising futur infill well locations.

The successful application of a fully integrated sequence stratigraphy study has led to the following depositional models and produced results that are compatible with the production history of the field. The basal seismic unit (IV) forms a depositional/compactional mound, onto which succeeding seismic units onlap. Seismic fades of units III and II range from mainly mounded, discontinuous to strong, continuous reflections and reflect deposition by debris flows and sheet- gravity flows respectively. Seismic unit I corresponds to two reservoir units, the main producing unit over NAC, the F1 and the overlying F0. Seismic fades of unit I range from a weak, discontinuous, mounded peak within F0 sediment fairways to a strong, continuous, mounded peak within F1 depocentres. Multiple episodes of sheet, sediment-gravity flows of the F1 reservoir were followed by channelised sediment-gravity flows of the F0 unit.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California