Estimating short-term capacities of geothermal wells

Abstract

In this report a geothermal system with full reinjection is analyzed. The focus is on extreme output situations, where wells are utilized at their maximum mechanical output. Such situations should not be maintained for long periods, a few days or months at the most, since the annual recommended average flow rate for long-term use is usuallybelow these levels. It is assumed that the geothermal reservoir together with production and reinjection wells can be modelled as a series of tanks. Due to a large demand difference between seasons the first degree term of the conventional flow-pressure relationship for geothermal reservoirs is omitted during high demand seasons, leaving only the turbulent term for consideration. Changes in water elevation in production and reinjection wells can be estimated with the full reinjection constraint for differentscenarios. Using this constraint, various combinations of production and reinjection wells may be analysed and provide answers to questions like: ?-What is the optimal combination of production and reinjection wells? At what depth shall the production pumps be placed? When is it economical to add a new reinjection well or a production well? Could we possibly increase the pump pressure instead??… Finally an optimizationprocedure regarding system setup for a closed geothermal system, is briefly introduced.