| Title | GEOTHERMAL RESOURCES IN THE AREA OF BEIJING |
|---|---|
| Authors | BIN Dezhi, LIU Jiurong, WANG Xiaoling |
| Year | 2002 |
| Conference | Beijing International Geothermal Symposium |
| Keywords | Geothermal geology; Geothermal resources; Development proposal; Geological structure |
| Abstract | Initiated by Mr. Li Shiguang who was a world famous geologist, geothermal exploration was started in the Beijing Plain in late 1960's. A few geothermal wells of 650-1158m were firstly drilled in the southeastern part of the urban area of the city, and geothermal water of 39.2-52.4? was found out. in the past more than 30 years, a number of geothermal fields have been identified and developed, such as those in the urban area, Xiaotangshan and Liangxiang. The area with geothermal potential has been defined as 2372km2. There has been more than 200 geothermal wells in Beijing, in which the deepest one is more than 4000m. The production capacity of the geothermal wells is often more than 1000m3/d, and some of the well can produce more than 3000m3/d. The geothermal water is of low mineral content water (TDS=500-700mg/l). The geothermal water is used for space heating, domestic hot water, health spa, recreation, greenhouse and fish farming etc. There are a few large-scale faults that are parallel to each other and strike in NE direction. The whole Beijing Plain is divided into a few grabens and hosts by these faults. The geothermal in the area of Beijing is of low-temperature resources stored in sedimentary basin. The geothermal reservoirs are Proterozoic siliceous dolomite, as well as Ordovician and Cambrian limestone. And the caprock is composed of conglomerate, siltstone, shale, tuff, basalt, sandstone of different geological time, as well as Quaternary lose sediment. The rock type and thickness of the caprock is different in each area. The geothermal gradient is 1.6-5.0?/100m, and it is closely related to the thickness of the caprock in most cases: the thicker the caprock is, the lower the geothermal gradient is. The most exploited geothermal fields are the Urban Geothermal Field, The Xiaotangshan Geothermal Field, as well as Liangxiang geothermal Field. And geothermal potential assessments of these two geothermal fields have been done on the basis of long-term monitoring data. For the other areas, analogue method was used to estimate the geothermal resources according to the assessment results for the above two fields. It is calculated that the heat storage in the 2372km2 area is 3.22?1020J, corresponding to the heating value of 110?108t standard coal, and the geothermal water storage (porosity of the reservoir is taken as 0.5-0.6%) in the area is 181.19?108m3. The heat stored in the geothermal water is estimated as 3.17?1018J, corresponding to about 1% of the heat storage of the geothermal reservoirs. The amount of geothermal water could be produced from the geothermal reservoirs on a sustainable basis is estimated as 1.09?108m3, according to the experiences from the Urban Geothermal Field and Xiaotangshan Geothermal Field (with some discount on basis of the understanding to each geothermal field). To use the geothermal resources in the area of Beijing in a sustainable manor, it is suggested: (1) To make a master plan for the geothermal development and utilization; (2) To focus on the geothermal within 3000m deep so as to avoid the high risks in developing deeper geothermal; (3) To do careful geological exploration before the drilling of geothermal wells; (4) To promote scaled geothermal development; (5) To promote geothermal reinjection; (6) To encourage cascaded use of geothermal resources; (7) To put more attention on the monitoring on the geothermal systems; (8) To do more detailed geothermal assessment. |