Abstract

Segmented graben systems develop stepovers that have important implications in the exploration of oil and gas in extensional tectonic basins. We have compared and modeled a representative stepover between grabens in Canyonlands, Utah, and the North Sea Viking Graben and, despite their different structural settings, found striking similarities that pertain to other graben systems. In both cases, the stepovers represent relatively high parts within the graben systems that are likely to be among the first to be filled with hydrocarbons generated in deeper parts of the grabens. Furthermore, the relay ramps and smaller fault offsets in stepovers ease hydrocarbon migration and allow stepovers to act as preferred migration routes from deep graben kitchens to structurally higher traps in the basin. Graben stepovers and their related structures should be paid special attention during exploration because they may represent hydrocarbon accumulations complementary to larger traps along the graben flanks. These observations explain the location of the Kvitebjørn, Valemon, and Huldra fields in a stepover structure of the Viking Graben and encourage increased focus on similar graben stepovers in the Viking Graben and other graben systems.

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