Influence of Quaternary glaciations on subsurface temperatures, pore pressures, rock properties and petroleum systems in the onshore northeastern Netherlands

Pleistocene ice ages had a profound influence on the subsurface, in parts, until the present day. Ice masses during glacial advances partly covered onshore Netherlands during two glacial periods, the Elsterian and Saalian stages. This study presents a 3D basin and petroleum systems model of the northeastern Netherlands with implemented glacial stages to address the influence of low surface temperatures and the mechanical loading of ice sheets on the subsurface. Two ice sheet thickness scenarios were used to constrain results based on published ice sheet thickness estimates.

Overall, Quaternary glacial stages substantially impact the temperature and pressure distribution in the subsurface. Subsurface temperatures are significantly reduced during glacial stages, leading to lowered present-day temperatures and a low geothermal gradient in the shallow subsurface. In deeply buried sedimentary formations, pressures build up with every glacial advance resulting in overpressures at the present day. Glacial stages do not directly influence the petroleum generation of petroleum source rocks in the area, but high pressures during loading might have impacted petroleum expulsion of the early mature Coevorden Formation. Hydrocarbon accumulations in the Lower Saxony Basin were simulated to investigate the possible effects of mechanical ice loading and unloading on hydrocarbon migration. A loss of Coevorden Formation-sourced hydrocarbons to the surface was calculated in the Lower Saxony Basin during the glacial stages, indicating an influence of glacial loading on the Mesozoic petroleum system.