Newly Discovered Giant Oil Fields of North Sea - The Role of Fractured Basement Highs

The discovery of the Johan Sverdrup oil field, estimated to contain 1.2 billion (recoverable) barrels, in the Norwegian sector of the North Sea has challenged oil exploration with a new petroleum system for the region. They key issue with the Sverdrup field is that the Upper Jurassic source rock is not mature below or in the vicinity of the reservoir, so that the oil must have migrated around, or, through the fractured basement high. The discovery raises the question if there are other giant oilfields waiting to be discovered on the ‘wrong’ side of basement highs, and what the resevoir potential of the high itself is. Applying a Sverdrup-like petroleum model, we evaluate if the oil missing in the hydrocarbon budget of the Central Graben could have migrated eastwards into and across the Mandal High (southernmost Norwegian North Sea), filling both fractured reservoirs in the granitic basement, and classical sandstone reservoirs on the eastern side of the basement high. In this contribution we present our model of the local petroleum system, and demonstrate some of the methods we have applied working on the reservoir and migration potential of the fractured high.