Structural evolution of minibasins on the Utsira High, northern North Sea; implications for Jurassic sediment dispersal and reservoir distribution

Abstract

ABSTRACT 3D seismic and well data are integrated to determine the tectono-stratigraphic evolution of the SW margin of the Utsira High, northern North Sea rift system. During the Triassic, a series of minibasins formed due to passive diapirism of the evaporite-bearing, Upper Permian, Zechstein Supergroup. Subsequently, during the Jurassic, a series of secondary minibasins developed as the underlying salt walls collapsed. These minibasins were a few hundred metres deep, bound by sub-circular to elongate salt-cored structural highs and caused the development of complex subaerial topography and submarine bathymetry on the SW margin of the Utsira High. Salt withdrawal may have been related to: (i) partial dissolution of salt; (ii) differential erosion of the salt walls and adjacent Triassic-filled minibasins; or (iii) salt remigration caused by sub- or supra-salt extension or sediment loading. This study provides insights into the tectono-stratigraphic evolution of the SW margin of the Utsira High and has implications for (i) facies distribution of the Zechstein Supergroup within the northern North Sea rift system; and (ii) depositional system development, and thus reservoir distribution, within the Jurassic sedimentary succession.