Original paper

Electrical conductivity as an indication for potential geothermal target layers within the North German Basin with respect to local geological conditions

Schaumann, Gerlinde; Grinat, Michael

Abstract

The local geological conditions of the Parchim borehole site and its vicinity, in the centre of the eastern North German Basin, were exemplarily investigated to determine the influence of electrical conductivities of overlying sediments on the detection of an assumed geothermal target layer with magnetotellurics, at a depth of approximately 6000 m, in the Lower Permian Rotliegend sediments. Mesozoic layers within the North German Basin have high electrical conductivities due to saline fluid in the pore spaces. Low resistivities (the reciprocal of the electrical conductivity) and high thicknesses of overlying layers can prevent the deeper layers from being determined by electromagnetic methods. The superposed sediments influence the determination of the target layer, depending on their resistivity and thickness. In the case of smaller thicknesses and higher resistivities of the superposed sediments, it is possible to detect the target layer, if it is also characterised by low resistivity. Several scenarios with variations of thicknesses and resistivities of the overlying Mesozoic sediments and of the target layer were modelled for layered cases, with parameters typical for the North German Basin. The aim of this paper is to investigate how a geothermal target layer can be delineated by magnetotellurics, when favourable conditions locally occur.

Keywords

electrical conductivityexplorationmagnetotelluricsgeothermal energygeophysical deepparchimnorth german basin