**2. Study Area**

The modeled salt structures are situated on the Hidra High (Model 1), and Sørvestlandet High (Model 2) on the platform just East of Central Graben in the Southwestern part of the Norwegian North Sea shelf (Figure 2).

**Figure 2.** Overview map of the study area situated on the eastern flank of the Central Graben seen as the green basement trend between the blue platform areas. Maps are modified from Norwegian Petroleum Directorate (NPD) maps. The inset map shows the study area situated centrally in the North Sea between mainland UK and Norway. Model 1 is positioned close to Well 1/3-8 on the Hidra High. Model 2 is shown by the red line. Hydrocarbon discoveries are shown in pink and light green.

Several oil fields (Mime, Ula, Tambar and Gyda) on the Cod Terrace and Sørvestlandet High and other discoveries in the areas are situated over salt structures with reservoirs in Upper Jurassic Ula sandstone [15]. On the Hidra High, several hydrocarbon discoveries are made including gas and oil in Late Paleocene Forties Formation (Oselvar, Ipswich), gas in Late and Early Cretaceous (1/3-1) and oil and gas condensate in Jurassic reservoirs (King Lear, Romeo). The Sørvestlandet area is dominated by pod-interpod salt structures [16–19]. Pods are irregular rounded basin filled with Triassic sediments

and distributed in a matrix of Zechstein salt forming walls, diapirs, ridges, and highs in a polygonal hive-pattern between the pods (Figures 3 and 4). The pods are capped by Jurassic to Cretaceous sediments. A system of collapse grabens in the Cretaceous unit follows the salt ridges surrounding the pod basins as can be seen in Figures 5 and 6. Their positions indicate a development related to vertical movement of salt structures and coeval subsidence in the pod basins.

The hydrocarbon potential in this area is related to Upper Jurassic reservoir rocks above structures defined by salt tectonics. A thick, more or less uniform salt unit was deposited over the entire area in Permian time, and has gradually developed into the complex salt structures we see today. Their development is related to episodes of salt movement from Early Triassic to Neogene time (Figure 4). The Model 2 profile crosses the Oda structure (well 8/10-4S) where oil is discovered in the Ula sandstone above a large salt structure. Other structures in the area have proven to be dry, thus it is of grea<sup>t</sup> importance to increase the understanding of the evolution and stratigraphy of similar undrilled structures in this area.
