3D seismic investigation of fluid migration and fluid accumulation related to natural seeps in the Sørvestsnaget Basin, SW Barents Sea

Abstract

This master thesis examines the intricacies of fluid migration, gas seep areas, and fault dynamics in the southwestern Barents Sea. Acoustic evidence, such as pockmarks and gas flares, indicates active fluid movement within the below seabed sedimentary structures, such as clinoforms and the Upper Regional Unconformity (URU). Challenging lowermost reaches of gas chimneys, obscured by acoustic masking, suggest fluid pathways shaped by tectonic forces and sediment composition. Seismic surveys revealed vertical and sub-vertical fault systems acting as migration conduits in high zones, contrasting with lateral movements through clinoform sequences in the basin's central area. Seismic anomalies and variances in reflectivity provided insights into gas accumulation and migration patterns, highlighting the importance of geological features in directing fluid flow. The thesis also sheds light on the reactivation of geological faults potentially due to isostatic stresses tied to glacial periods, affecting the hydrocarbon expulsion and migration over time. Insights into the glacial impact on sediment deposition, uplift, and erosion from the Paleocene to the Pleistocene point to a complex sedimentary environment influenced by isostatic adjustments. These geological processes have contributed to the formation of stratigraphic traps and the destabilization of pore fluids, underscoring the dynamic nature of the Barents Sea’s subsurface. This work uncovers the fluid expulsion and gas migration episodes induced by repeated glacial-interglacial cycles and presents a model for gas dispersion within the region. Future research could explore seismic imaging techniques, gas hydrate stability, and integrated fault reactivation studies to advance the current understanding of this geologically active region.