The Mjølnir Impact Crater in the central Barents Sea - a potential hydrocarbon system?

Abstract

A meteor impact event on the Bjameland Platform in the Norwegian Barents Sea about 142 ± 2.6 million years ago formed the Mjølnir Impact Crater. The structure has diameter of 40 km impacting the Mesozoic stratigraphy, and has previously been investigated with emphasis on the dynamics of the impact, the structure formation, sedimentation and post-impact tectonics. Impact structures have proven to be petroliferous elsewhere in the world. By applying new seismic 2D- and P-cable data and integrating prior studies, this thesis focuses on how the structure of the Mjølnir Impact Crater might represent a petroleum system in the Barents Sea. The structural setting of the Mjølnir impact Crater shows several potential structural traps, including horst and graben structures within the crater, and listric rim faults at the periphery. A simplified 1D maturation model of potential source rocks in the area, indicate that the Hekkingen and Steinkobbe formations are sufficiently matured and have generated oil, while the Lower Triassic formations have generated gas. These source rocks may potentially charge the Mjølnir Impact Crater by petroleum migration vertically along deep-seated faults and laterally in the southward dipping stratigraphy, from the Nordkapp Basin area. The southern section of the Mjølnir Impact Crater is considered have the highest hydrocarbon potential, due to a thicker overburden and favorable migration pathways. Five seismic anomalies of high amplitude have been identified in the southern Mjølnir Impact Crater. These are interpreted to represent hydrocarbon accumulations, structurally trapped in horsts and by listric rim faults, and overlain by Upper Jurassic shales with sealing properties. Volumetric calculations for one of the amplitude anomalies suggest that 24,4 MMSm3 of oil may be accumulated at the southern boundary of the crater. In conclusion, presence of source rocks, migration pathways, reservoir and traps supported by observations of seismic amplitude anomalies suggests that the Mjølnir Impact Crater represents a potential hydrocarbon system.