| Abstract |
For most geothermal fields, the sustainability is limited by lack of liquid recharge, rather than lack of heat content. The extraction of geothermal fluid often causes continuous lowering of the pressure of the production wells. It is necessary to keep good balance between the geothermal fluid production and recharge. This is often a very difficult task, because the changes, on the fluid pressure of the production wells and the surrounding area, caused by production of geothermal fluid is often difficult to foresee. On the other hand, the recharge of a geothermal system is also difficult to predict, and it may change along with the amount of geothermal fluid production and the distribution of the production. Technical measures are very important for keeping the balance between fluid production and the recharge of a geothermal field, including monitoring, reinjection and modelling. And administration measures are equally important, for limiting the amount of production and enhancing reinjection, especially for geothermal fields that have many users. Beijing has abundant low-temperature geothermal, and it has had a nearly 40 year history of scaled geothermal utilization, including space heating, bathing, swimming pools, health spas and recreation, greenhouses, fish farming etc. Owing to over extraction of geothermal water, the pressure of the geothermal wells has started to decline rather fast in the most important geothermal fields since the early 1980’s. To realize sustainable use of geothermal resources, a lot of measures, both administrational and technical, have been applied in Beijing. As a result, the water level decline of the most important geothermal fields, such as southeast Urban and Xiaotangshan areas, have been greatly reduced, even stopped recently in the later one. |