An Integrated Study of the Oligocene Sequence Stratigraphic Framework in the Egersund Basin, Norwegian North Sea
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The Oligocene interval of the Egersund basin in the Norwegian North Sea is under-studied stratigraphic successions due to its minor significance for the oil and gas industry. The purpose of this study was to improve the understanding of the sequence stratigraphic development in the area of the Egersund Basin. The Oligocene succession formed as a response to an interplay between different controlling factors, such as tectonics, eustasy, sediment supply and accommodation space. The uplift of the mainland Norway and the thermal subsidence of the North Sea affected the sediment supply of the Oligocene interval. The succession of Oligocene deposition varies considerably in thickness from the Stavanger Platform to the northeast and further basinwards to the southwest. Six key surfaces were mapped (Base Oligocene surface (MFS1), MFS2, SB1, MFS3, SB2 and Top Oligocene surface (MFS4)) within the post-rift Oligocene strata of the Egersund Basin and the nearby Åsta Graben in the Norwegian-Danish Basin. These key surfaces divide the Oligocene strata into seven seismic units (Units A-G), identified based on reflector terminations and internal reflector configuration. Two complete, third-order cycle sequences bounded by a maximum flooding surface were identified in the study area. These sequences comprise two highstand systems tracts (HST2 and HST3), two lowstand systems tracts (LST1 and LST2) and two transgressive systems tracts (TST1 and TST2).
Master's thesis in Petroleum geosciences engineering