Investigating the impact of the Hornsund High on Triassic sedimentation in the western Barents Shelf

The Triassic on the southwest Barents Shelf important for hydrocarbon exploration as several hydrocarbon source and reservoir rocks occur within this interval. Despite favourable conditions for hydrocarbon accumulation, the architecture of the depositional systems and varied provenance has caused difficulty predicting reservoir distribution and their properties.

Irregular palaeotopography is thought to have affected sedimentation. Late Palaeozoic rifting resulted in the uplift of prominent structural highs. In the exploration areas, the subsurface Loppa and Stappen highs acted both as sediment sources and barriers to sediment dispersal. The Hornsund-Sørkapp High is an analogous high that is well exposed in southern Svalbard, whose influence on sediment dispersal may be evaluated more cost effectively.

The results reveal Triassic shales rest on Permian carbonates in areas east of the high and the main potential for reservoir development lies in immature deltaic sediments sourced from the east. However, significant differences in sediment thickness, facies, and apparent provenance are seen across the high. Notably, on the top of the high, thin Early Triassic conglomerates rest unconformably on foliated Palaeozoic units belonging to the high. In addition, west of the high, the immature deltaic sediments sourced from the east are largely absent. Instead, mature Middle Triassic sandstones which were sourced from the west are developed.

The results imply the Hornsund High had a notable impact of sedimentation. The high was exposed in the Early Triassic resulting in the deposition of local conglomerate units. Following transgression, the influence of the high persisted into the Late Triassic, possibly creating a barrier to immature deltaic sediment sourced from the east.

The Loppa and Stappen highs, located in the exploration areas to the south of Hornsund, may have similarly affected sediment dispersal. If so, then the results could suggest poor reservoir development in the Late Triassic in areas west of the highs. However, they highlight the possibility of locally sourced Early Triassic, and westerly sourced Middle Triassic siliciclastic reservoirs, generally absent in areas to the east.