Quantitative hydrocarbon potential mapping and organofacies study in the Greater Balder Area, Norwegian North Sea

Abstract

Quantitative maps of the reconstructed oil and gas potential of the Draupne and Heather Formation in the South Viking Graben were produced in order to improve the understanding of lateral and vertical variations in the type of organic matter. For this purpose the Draupne Formation was subdivided into a lower synrift and an upper postrift part (Upper and Lower Draupne Formation, respectively). Both sections show large lateral variability in source rock quality and oil and gas potential. The total TOC distribution is strongly related to the depositional environment and also to the preservation of organic matter. The Upper Draupne Formation exhibits equally high amounts of oil- and gas-prone organic matter. The Lower Draupne Formation shows a considerably higher amount of land-derived Type III organic matter, which decreases upwards and towards the Utsira High. The marine Type II material in the synrift section is less abundant, because of dilution of the marine material by terrestrial material transported by mass flows from the surrounding highs. These findings are supported by environmental molecular data. The Heather Formation is a mixture of type-III and -II kerogen and shows moderate to good gas potential. The source rock sections were also correlated using the relative occurrence of bisnorhopane in the rock extracts.