3-D Seismic Facies Mapping and Well Data in 2-D Seismic Forward Modelling of Late Paleozoic Carbonate Deposits, Finnmark Platform, Southwestern Barents Sea

Bjarne Rafaelsen¹, Lars Stemmerik², Steen Agerlin Peteresen³, and Karin Andreassen^4
1Exploration Northern Areas, StatoilHydro ASA, Harstad, Norway.
²Section of Geography, University of Copenhagen, Copenhagen, Denmark.
³Research Centre, StatoilHydro ASA, Bergen, Norway.
⁴Department of Geology, University of Tromsø, Tromsø, Norway.

Upper Paleozoic carbonate buildups have been penetrated by well 7229/11-1 on the Finnmark Platform, southwestern Barents Sea. The well is situated close to the centre of a 3D seismic survey and therefore provides the opportunity to perform well-calibrated seismic facies mapping of the carbonate succession. Using this as a basis, 2D forward seismic modelling of carbonate buildups has been performed.

This study aimed to better understand the seismic response of the carbonate succession, the buildups and discontinuities observed in the 3D seismic data. Rock properties from well 7229/11-1 were supplemented by information from nearby wells to account for more basinal deposits. The use of seismic forward Compound Modelling software, developed by StatoilHydro Research Centre, Bergen, has helped to make more realistic models and thus to better realize the seismic response of the succession. The software takes the step from simple ray tracing to fast convolution based synthetic seismic and integrates subsurface petrophysical properties (velocity and density) with interpreted lithology distribution and architecture.

No faults or discontinuities were introduced to the model, just a detailed facies distribution. The modeling confirms results from the 3D seismic facies mapping and portrays the buildups in a similar manner as in the original seismic data. Interestingly, discontinuities occurring in the modelling results within and just below the carbonate build-ups are interpreted as artefacts due to velocity contrasts. Therefore, when interpreting the 3D seismic data set, only the discontinuities that show horizon offsets beyond the lateral dimensions of the overlying carbonate buildups / abrupt changes in the evaporite deposits can be regarded as real faults.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia