Contact metamorphism and thermogenic gas generation in the Voring and More basins, offshore Norway, during the Paleocene-Eocene thermal maximum

Voluminous volcanic intrusive activity took place in the Voring and More basins at the Paleocene-Eocene boundary at about 56 Ma. This event caused thermal maturation of Cretaceous sedimentary rocks in the basins. We have estimated the resulting thermogenic gas generation potential from contact metamorphism using numerical simulations calibrated using borehole data. The borehole 6607/5-2 from the Utgard sill complex in the Voring Basin contains two c. 100 m thick sills and is used as a case study. We present both new and compiled data showing that (1) the bulk organic content is reduced towards the sill intrusions, (2) a c. 1 km thick stratigraphic interval is thermally affected, based on vitrinite reflectance data, (3) relative emplacement timing can affect the gas yield by up to 25%, and (4) some of the thermogenic methane is still present in the aureoles. The numerical model is calibrated using data from 11 wells. We estimate that the total gas generation potential for the two Utgard sills equals that of the Troll field (c. 10 Gt CH4), the largest producing gas field offshore Norway. We show that in the Voring and More basins, the total gas generation potential is up to 1500 Gt CH4 (c. 1100 Gt C), even from the relatively organic-poor Cretaceous source rocks with c. 1 wt% organic carbon, with implications for the carbon cycle at the Paleocene-Eocene boundary.