Unexpected knowledge of geothermal resources
(1)The distribution of geothermal resources is obviously controlled by China’s geological structure and its position in the global tectonics
China is situated in the eastern part of the Eurasian plate, and the main body of the China Continent sits among the Indian plate(including Burma plate), Pacific plate and Philippines plate. The mechanism of collision and subduction of those plates resulted in the uplift of the present Qinghai-Tibet Plateau, and the formation of some down-warped basins like Tarim and Junggar, and Cenozoic fault depressional and stretch structures with North China as the representative as well as many complicated but orderly intraplate fracture pattens. Such a tectonic framework has exerted an important influence on the formation and distribution of China’s geothermal resources, resulting in the formation of two geothermal and high heat flow value zones: one is in Tibet and Yunnan, the other is along the southeastern coast. The high heat flow value zone itself is an area where geothermal hot springs are concerntrately distributed(see Fig. 2.5.1).On such a geological background, geothermal resources occur in two forms: one is geothermal hot springs outcropping along the major fractures and controlled by the areas of tectonic upheaval; the other is geothermal water occurring in the Mesozoic and Cenozoic sedimentary basins. The former resources are exposed directly on the surface in the form of hot springs in zonal distribution, obviously controlled by fracture structures, with their usable geothermal resources mainly dispersed over fracture zones as well as the zones of their influence;and the latter are buried in the deep geothermal reservoirs with their geothermal heat provided by the conductive heat in the interior of the earth and the usable geothermal resources distributed over the central parts of large sedimentary basins and their buried upheaval zones.
(2)Geothermal resources are widely distributed
The exploration of geothermal fields shows that exploitable geothermal resources are scattered all over the whole country except Shanghai and Ningxia, which has provided a vast space for the development of geothermal resources.
(3)Geothermal resources of low-moderate temperature are predominant and are the key objectives for development and utilization in China
According to the statistical data of exploration in the existing 761 occurrences, there are only 2 high temperature geothermal fields(the Yangbajain and Yangyi geothermal fields in Tibet, and all the rest are lowmoderate temperature geothermal fields. Of them 26 are moderate temperature fields(90~150¡æ), accounting for 3.4%; and 733 are low temperature geothermal fields under 90¡æ, amounting to 96.3%. The average temperature of explored geothermal fields is 54.8 ¡æ for the whole country, with the highest average of 88.6¡æ in Tibet and the lowest average of 37.7¡æ in Hunan(Table 2.5.5).Henan Hongxing Mining Machinery Co., Ltd is the professional manufacturer of complete sets of mining machinery, for example,mobile crushing station,ball mills Welcome all of you to visit our official website.secondary cone crusher:http://www.hx-china.com/5.html
Table 2.5.5 Average temperature of geothermal fields in different areas of China
(4)Most of the geothermal fields are medium and small in size
In the 761 geothermal fields which have been explored, 55 are large and medium-sized ones, occupying 7.2%, but their usable heat energy is 3£¬288.10MW, making up 75.87% of the total usable heat energy; 706 are small-sized geothermal fields, 92.8% of the total , but the usable heat energy is only 1£¬045.79MW, 24.13% of the total, and averages only 1.48MW.
(5)The geothermal water has a low degree of mineralization in most cases and is suitable for a multiple of uses
Water analyses of 493 geothermal fields show that 327 geothermal fields have geothermal water with the content of dissolved solids less than 1.0g/L, occupying 66.3%, and 42 geothermal fields have water containing dissolved solids over 3.0g/L, 8.5% of the total(Table 2.5.6).
Table 2.5.6 Degree of mineralization of geothermal water in the explored geothermal fields in China
(6)Medium-and small-sized geothermal fields with surface thermal manifestations in the uplift area can be developed and utilized more economically
Those geothermal fields have shallow heat reservoirs, usually 300~500m deep and are easy for development. Geothermal water receives some recharge and is good in quality, so it can be used for various purposes. With some further exploration work, the distribution scope, quantity of resource and the conditions for development will be basically defined. Exploration indicates that the explored exploitable geothermal resources can be increased by several times its natural discharge, which shows that further exploration work would make geothermal resource effectively utilized.
(7)Geothermal fields in large sedimentary basins have great potential for development and utilization
Geothermal resources in those sedimentary basins, the North China Plain and the Song-Liao Basin in particular, have great potential for development. However their development is restricted by the buried depth of hot reservoirs, lithology and recharge conditions. For geothermal water over 40¡æ, exploitation depth generally should be no more than 1,000 m. Now in some areas, however, exploitation depth has already exceeded 3,500 m and the depth and scope of the development of geothermal water of 70~90¡æ are showing a tendency of daily increase.
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