Interpretation of 3-dimensional seismic data from the Sørvestsnaget Basin in the southwest Barents Sea demonstrates that Middle Eocene deep-water depositional systems are highly deformed by post-depositional sand remobilization and injection.
Numerous high amplitude features observed in the oldest depositional system reveal bowl- and W-shaped geometries in vertical seismic sections.
Paulina Safronova will give a talk entitled “Sandstone injections in Middle Eocene deep-water depositional systems in the Sørvestsnaget Basin, SW Barents Sea” in the Hydrocarbon Habitats seminars February 16/17 in Oslo/Stavanger.
In 3D view, the bowl-or W-shaped features have the appearance of downward narrowing cones or truncated cones (see figure).
Timeslices and seismic amplitude maps reveal that the “cones” have irregularly circular or polygonal plan view geometries, and have a diameter of several kilometres at the shallower stratigraphic levels.
The bases of bowl- and W-shaped features are inferred to be in situ depositional sandstone bodies.
Discordant wing-like parts are inferred to be sandstone injections, sourced from the margins of the concordant sandstone bodies.
The deep-water depositional system’s tendency to undergo post-depositional sand remobilization and injection is mainly due to the presence of good sealing rocks (low permeable mudstones) and a volumetrically significant, well sorted, unconsolidated sand in which an excess-fluid pressure has developed.
In the Sørvestsnaget Basin, pore fluid overpressure in the buried Middle Eocene sand bodies is suggested to be the result from (1) rapid burial, (2) fluid migration into the sealed sand bodies from deeper sources via synsedimentary faults and (3) fluid drainage (de-watering) from the surrounding mud during early compaction.
Post-depositional sand remobilization and injections have important implication for hydrocarbon exploration as they affect a reservoir primary architecture, and if large enough, sandstone intrusions may themselves be standalone reservoirs.