Reassessment of the Mid North Sea High – Updated Petroleum System Analysis Based on New Seismic Interpretation Results

The Mid North Sea High (MNSH) is one of the last remaining underexplored regions on the UK continental shelf. Exploration efforts have been restarted with a renewed focus on the Paleozoic basins benefitting from released 2015 government-funded seismic acquisition. The results allowed improved imaging of sub-Zechstein intervals, essential to delineate individual Paleozoic play and trap types. Key elements of the Paleozoic petroleum system are Dinantian/Namurian source rocks likely to have contributed to the recent charge of the Breagh gas discovery in the southern portion of the MNSH. We present petroleum system modelling results from four 2D composite sections across the MNSH extending into the UK Central Graben. Key aspect was the assessment of the interplay of multiple processes that control thermal maturity of the Paleozoic source rocks and the related timing (e.g., paleo-heat flow, amount of erosion, and impact of Caledonian plutonism). Although hydrocarbon losses are predicted for the southern part of the MNSH during Variscan orogeny, discoveries such as Breagh and Crosgan point to late hydrocarbon charge. Towards the central part of the MNSH, the models predict a late phase of hydrocarbon generation from Carboniferous source rocks, taking place after trap formation and with mudstones reaching enhanced sealing efficiencies.