PRODUCTION CAPACITY OF GEOTHERMAL SYSTEMS

摘要

Geothermal systems are classified on the basis of reservoir temperature, reservoir enthalpy, their physical state or their nature and geological setting. They are often classified as either hightemperature (reservoir temperature a 1 km depth above 200°C) or low-temperature (reservoir temperature a 1 km depth below 150°C). Geothermal systems are also classified as (a) volcanic systems with the heat sources being hot intrusions or magma, (b) convective systems with deep water circulation in tectonically active areas, (c) sedimentary systems with permeable layers at great depth, (d) geo-pressured systems, (e) hot dry rock or enhanced geothermal systems and (f) shallow resources utilized through ground-source heat pump application. Low-temperature resources are distributed throughout the world; they are not restricted to volcanic regions. They are suitable for various direct applications, in particular spaceheating. Even though geothermal resources are considered renewable their production capacity is not unlimited. It is predominantly controlled by the reservoir pressure decline caused by the hot water production. This is in turn determined by the size of a geothermal reservoir, its permeability, reservoir storage capacity, water recharge and geological structure. Geothermal systems can in most cases be classified as either closed, with limited or no recharge, or open, where recharge equilibrates with the mass extraction. Volumetric assessment and dynamic modelling are the main methods of estimating the production capacity of geothermal reservoirs. Simple analytical models, lumped parameter models and detailed numerical models are used to simulate the nature and production response of geothermal systems as well as to calculate future predictions.