3D-seismic interpretation of fluid flow systems and faulting in the Sørvestsnaget Basin and the Veslemøy High, SW Barents Sea

Abstract

The southwestern Barents Sea encompasses a large part of the Norwegian Continental Shelf (NCS), expressing a complex geological history. The area is characterized by a series of rifting episodes from the Mesozoic and Paleozoic eras, along with more recent glacial impacts from the Late Cenozoic and the Quaternary period. The SW Barents Sea has experienced erosion and uplift, with large depocenters being created along the westernmost margin of the area. The complexity of the area has highly affected the fluid flow systems and is one of the major reasons that exploration activity in the SW Barents Sea has been limited until recently.

This study investigates the structural evolution and fluid flow characteristics in the Sørvestsnaget Basin and the Veslemøy High, where the basin development is closely linked to the opening of the Norwegian-Greenland Sea and reorganizing plate movement. These events caused extensive rifting, creating a large depocenter where deep-rooted and shallow faults were established. Through 3D seismic investigations, the study area exhibits a series of chimney structures, mud volcanoes, shallow gas anomalies, and faults related to fluid migration. Seismic interpretation reveals the presence of different fluid flow systems in the western and eastern parts of the study area, displaying different mechanisms controlling the fluid flow patterns. The western part of the study area seems to be controlled by the Plio-Pleistocene wedge in the Naust Fm., directing fluids towards the surface where they accumulate along the Near Base Naust surface below the Upper Regional Unconformity, and within the Quaternary sediments above. The presence of an apparent diagenetic transformation zone appears on the structural highs to the northwest in the Sørvestsnaget Basin and on the Veslemøy High in the east, where deep-rooted faults limit their extent into the Sørvestsnaget Basin. The fluid flow system in the eastern parts of the study area is suggested to be controlled by the diagenetic zone, guiding fluids towards the structural high.

The findings in this thesis imply complex settings where both lateral and vertical migration of fluids can be connected to different source rock intervals from both the Late Mesozoic and Cenozoic ages. The appearance of seafloor and paleo-depressions could strengthen the theory of severe fluid expulsion, and highlights the impact of glacial processes along the western margin of the SW Barents Sea.