Geothermal reservoir rocks in Denmark

An extended summary of a DGU/EEC research project is presented. The possibilities of low enthalphy energy sources in Denmark have been investigated . Particular emphasis has been placed on the reservoir characteristics with the intent, if possible, to produce synthetic reservoir assessments.

The investigations of the reservoirs have included the establishment of sedimentary environment, degree and type of diagenesis, temperature mapping, factors controlling formation brine salinity, the decrease of porosity with increased depth of burial, and the relationships between porosity and permeability.

Very simplified, the porosity of the reservoirs decrease from 30-40 % at 500 m depth to 5-15 % at about 3500 m d pth. The significant decrease in permeability with increased depth is noted. Temperatures increase from about 55- 75°C at 2000 m to 75-105°C at 3000 m depth. Temperatures of I 00-150°C are reached in the central part of the sedimentary basins.