Exploring stratigraphic traps: an example from the Upper Jurassic in Block 33/9, the Norwegian North Sea

Abstract

Abstract Stratigraphic trapping potential is identified in Block 33/9 by the occurrence of a seismically well-defined Upper Jurassic anomaly interpreted to represent sands deposited in the hanging wall of a rotated fault block. This interpretation is supported by a fan-shaped morphology, very distinctive mounding and associated differential compaction observed on 3D seismic data. Similar oil-bearing sandstones have been penetrated in the Statfjord Nord Field, where the Upper Jurassic (Volgian) sandstones (informally designated “Munin”) consist of a shoaling-upward shallow marine sequence with excellent reservoir characteristics overlying a turbidite lithofacies with very good to excellent porosities and permeabilities. The Upper Jurassic Draupne and Heather shales envelop the “Munin” sandstones, thereby acting as a seal and in the case of Draupne Formation, an organic-rich source rock. High-quality 3D seismic data were used to map this play. A two-dimensional seismic modelling study was undertaken to constrain the geologic model of a distinct seismic anomaly. The modelled time response shows a remarkable likeness to the real seismic data. Because this is a stratigraphic play, trap and seal are interdependent, and constitute the main risks.