Sedimentation process and stratigraphic evolution of deep-water sediments in Sørvestsnaget Basin, Southwestern Barents Sea

Abstract

Deep-water clastic reservoirs are one of the most important hydrocarbon plays in the Atlantic region, especially on the Norwegian Continental Shelf. In the Sørvestsnaget Basin, the provenance and origin of Tertiary sediments are still poorly studied and understood as there is a general lack of good quality seismic data and well control to constrain the geology of the area. This work is aimed at identifying different sediment packages preserved in the Sørvestsnaget Basin during the Tertiary period and also define their geometry, distribution, depositional environment, and source area. High-quality 2D seismic reflection datasets and two exploration wells, 7316/5-1 and 7216/11-1 were used to characterize the sediment types, and to define their geometry and depositional architecture. Seismic attribute analysis includes the use of instantaneous phase to further elucidate seismic reflector patterns. Five main sedimentary packages were defined from the seismic data and were correlated to tertiary sediments in the boreholes. In terms of the internal geometry of reflectors, the five packages are characterized mainly by westerly dipping clinoforms except for SP3 which is in turn reflected as chaotic to transparent seismic facies. In addition, the basal package (SP1) is composed of Eocene sediments and both NE-SW and W-E oriented clinoforms suggestive of dual direction of sediment transport from the northeastern and western areas during Eocene times. The abundance of radiolaria and agglutinated foraminifera in the cutting samples coupled with the absence of calcareous fossil imply that the Eocene sediments in the study area were deposited below the Carbonate Compensation Depth (CCD). Similarly, clinoforms in package 2 are oriented in southwestern direction signifying sediment source area in the northeastern. V-shaped submarine canyons were interpreted in this interval, at their distal part they lack downslope apron and are abutted against the Senja ridge. The most important piece of information from this work is that tertiary sediments in the Sørvestsnaget Basin were sourced and transported from the northeast and western direction in areas correlated to Svalbard, Stappen High and perhaps the Eastern Greenland. Deposition in the basin was influenced by multiple cycles of erosion, uplift, progradation, retrogradation and slumping.