Relationship between glacial erosion and fluid flow inferred from 3D seismic data : SW Barents Sea

Abstract

This Master thesis investigates the relationship between glacial erosion, glaciotectonically displaced sediment blocks and indications of fluid flow and shallow gas accumulations in buried glacial sediments of the south-western Barents Sea margin. The thesis is based on two three-dimensional (3D) seismic datasets, NH98003 and EL0001, the two-dimensional (2D) seismic survey NH9702 and exploration well 7216/11-1. 3D seismic techniques have allowed mapping and visualizing of buried geomorphological features in great details within the study area. Large semi-circular depressions and fluid migration pathways are imaged, as well as glacigenic sediment blocks and rafts. A glacigenic origin is inferred for the megablocks and rafts indicating high glaciotectonic activity of the former ice streams. Six large-scale depressions are inferred to be sources for the removal of sediment mega-blocks and rafts at one particular stratigraphic level of the Plio-Pleistocene succession. Mapped fluid migration pathways and shallow gas accumulations show evidence of an active fluid migration system, and its spatial relationship with the erosional depressions is documented. Modeling of the gas hydrate stability zone has been performed for glacial and interglacial conditions and its effect on the sediment properties is discussed. A conceptual model is proposed for the formation of the depressions, where brittle glaciotectonic deformation along a weak layer at the base of gas-hydrate cementing sediments is inferred. Subsequent expulsion of gas-rich fluids is assumed to have followed deglaciation which might further have reworked the depressions.