Seismic evidence for fluid migration and gas accumulation in sediment formation beneath the giant Storegga slide complex (Grip high 3D cube)

摘要

The study area covers the northern sidewall of the Storegga slide located at the southern limit of the Vøring Plateau. The water depth at mid-Norwegian margin varies approximately between 500 and 1500m. The mid-Norwegian margin area has been known to be prone for submarine sliding and is therefore a key location for studying morphological features to improve our understanding of slide mechanisms. The master thesis aims to investigate fluid migration into the Naust formation from deeper reservoirs and its potential role in slope failure. The 3-D seismic dataset GH01 allowed mapping and visualizing of three slides at the northern sidewall of the Storegga slide. Fluid migration from deeper sources through polygonal and extensional faults and acoustic pipes, gives rise to fluid accumulations under impermeable glacigenic debris flow deposits within Naust formations. The role of fluid flow for slope failures is difficult to decipher. Acoustic pipes north of northern sidewall of the Storegga slide indicate focused fluid flow and a possible active fluid migration system. The layer-bound polygonal faults within Brygge and Kai formations and their extension to the lower Naust formation may be caused by rapid loading adding to the fluid migration pathways to the Naust formation. Thus migrated fluids have been documented to accumulate within the slide prone Naust formations. The three slides identified at the northern flank of the Storegga slide have their basal surface on the marine clays indicating the slope failure on marine deposits. Fluid flow is not considered solely responsible for slope failures but the presence of faults down to the headwall of each slide does support an important buildup of zones of weakness for fluid migration contributing to slope failure.