DETAILED THREE-DIMENSIONAL MODELING OF THE BOTN HYDROTHERMAL SYSTEM IN N-ICELAND

A detailed three-dimensional numerical model has been developed for the low-temperature hydrothermal system at Botn in Central North Iceland. It is based on a conceptual reservoir model which has evolved during two decades of gkthermal research in the area and on the 10 year production history of the system. The model consists of (1) A powerful recharge system at depth, (2) a shallow production reservoir and (3) a cold ground-water system at the surface. About 10 million tons of hot water have been extracted from the production reservoir since late 1981. The presence of the powerful recharge system results in a very slow long-term pressure decline. Flow of water in the production reservoir appears to be controlled by a highly permeable, vertical fracture-zone confined by low-permeability rocks. Cold ground-water flows down into the fracture-zone during production causing some cooling of the extracted water