Long-term preservation and enhancement of flow paths in deep geothermal reservoirs.

The preservation and enhancement of the transmissivity of water-conducting fractures in the area of the injection of thermal water is one of the main goals within the long-term operation of geothermal power plants. In the Bavarian Molasse basin thermal water is produced for heat and energy generation from the carbonaceous Malm aquifer with temperatures between 65 and 145°C with pumping rates up to 150 1/s. The thermal water, which is cooled down at the surface is pumped back to the carbonaceous reservoir. In spite of the higher carbonate solubility of cooled down water and the solution of carbonaceous host rocks in the close vicinity of the injection well, the transmissivities of waterconducting fractures and pores can be long-term decreased by precipitating e.g. silicate minerals. [ABSTRACT FROM AUTHOR]