Back-calculated petroleum generation potential of Jurassic marine shales through time and space in the Danish North Sea

Oil and gas geochemistry shows that the primary source rock in the Danish Central Graben (DCG), North Sea, is the U. Kimmeridgian–Ryazynian marine shales of the Farsund Fm. Potential additional marine source rocks are the shales of the Oxfordian–L. Kimmeridgian Lola Fm and the relatively poorly known L. Jurassic Fjerritslev Fm. The shales of the Farsund Fm show significant lateral and stratigraphic variations in source rock quality (Petersen et al., 2010, 2013; Ponsaing et al., 2018). These organofacies variations are recorded in the oil geochemistry. To obtain higher granularity and capturing these variations the U. Jurassic shales were subdivided into seismic units (Lola Fm: pre-FSU1; Farsund Fm: FSU1 to FSU6) delineated by regional mappable seismic markers (FSM). The uppermost FSU6 contains the Bo Member (‘Hot Unit') that has normally been considered the most oil-prone section characterized by elevated TOC contents and HI values. The depositional area of the units varied through Late Kimmeridgian to Volgian times.