Structural mapping of large aquifer structures

In this presentation we show results from a large hydrogeophysical survey carried out in Vendsyssel in the northernmost part of Jutland, Denmark. In the search for groundwater resources the survey clearly demonstrates the effectiveness of using cost-efficient transient electromagnetic (TEM) methods in combination with geological evaluations of existing bore hole data and other geological information. The TEM data has been measured in several periods where the oldest measurements were performed with a ground-based system while the newest measurements were carried out using the newly developed air-borne Sky TEM system. The methodology used in the survey comprises different phases involving an evaluation of existing drill hole information, selection of areas of specific interest, mapping using ground-based or airborne TEM and evaluation of the geophysical models. This evaluation forms the basis for pointing out sites for supplementary investigation drilling. The described methodology is cost-efficient as the number of expensive drillings is cut down to a minimum. Also, the methodology is general in all aspects and directly applicable to sedimentary areas worldwide.