The Life and Death of Hydrocarbon Traps in East Greenland: The Charge and Degradation Histories of Laplace Bjerg and the Mols Bjerge

Abstract

The exhumed hydrocarbon traps of East Greenland provide a superb opportunity to study the evolution of fluid flow in the petroleum systems of the North Atlantic. Following basin inversion during the Cenozoic these structures were exhumed and deeply incised which has allowed them to be observed and mapped in great detail. This study examines the diagenetic history of the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps, from the initial charge of Triassic and Jurassic reservoirs, to their eventual uplift and destruction. Detailed petrographic analysis was undertaken on 67 samples collected at representative intervals throughout the structures. Variations in the distribution of diagenetic phases and remnant porosity were investigated. Twenty three samples were also subjected to helium porosity measurement. Bitumen, up to 18%, was recognised in 34 samples, 6 of which were analysed for their form and reflectance. Fluid inclusion data, collected from the nearby Bjørnedal region, helps to constrain the thermal history of the region. Helium porosity and permeability measurements are low, largely below 10% and 2 mD respectively. However, the abundance of bitumen highlights the presence of significantly higher porosity and permeability during hydrocarbon charge. A synthesis of fluid inclusion data and bitumen reflectance, alongside a detailed examination of the paragenetic sequence, demonstrate that hydrocarbon charge occurred in the Eocene, during maximum burial, at which time only a minor reduction in original intergranular porosities had taken place. The destruction of the pore systems occurred due to the degradation of hydrocarbons to bitumen, resulting from heat flow during intrusive events, and subsequent carbonate and limonite cementation during uplift. The original source of the hydrocarbons is unclear. This work highlights that where unaffected by intrusives and uplift, the largely untested Triassic play may still contain viable reservoir intervals at depth on the Norwegian Continental Shelf.