2.5.3.1 Availability and Consumption

China's exploitable geothermal resources are unbalanced in distribution and vary in feasibility of development from place to place. Different areas have different demands for geothermal resources. Generally geothermal resources are mainly developed for heating and medical bathe in northern China and for medical treatment, tourism and aquiculture in southern areas. In sedimentary basins geothermal fields  are widely distributed and can be concentrately developed, but the heat reservoirs are deeply buried and large investment is needed for their development, so the development is limited to cities, towns and their adjacent areas, such as Beijing, Tianjin, Xi'an, Kunming, Zhengzhou and Kaifeng. In the tectonic uplift areas,where geothermal fields are generally small in size and dispersively distributed, the development is usually carried out around the outcrops of geothermal water. Since the buried heat reservoirs are shallow and exploitation is easy with small investment, much attention has been paid to their development in areas with convenient transportation and developed economy, such as Nantian of Sanya City, Guantang of Qionghai, Xinglong of Wanning and Lanyang of Danzhou.in Hainan Province.

China's development of geothermal resources is obviously restricted by two conditions. The first one is resources. Usually at the early stage the development speed of a geothermal field increases rapidly, but after a certain period the development slows down because of resources' restrictions. To prevent any possible excess pumping, the only way is to control the pumpage at a certain level. The development of the geothermal field in southeastern Beijing, for example, maintained a momentum of increase for only 15 years. The second one is development level of local economy. For the development of heat conduction type geothermal fields, the operation depth at present time is usually from 2,000 to 2,500 m and in some areas with good economic conditions the maximum can be over 3,500 m. However, only those units or departments with good economic conditions are able to develop the geothermal resources. As to the convection type geothermal fields, now the development is limited to the geothermal fields with geothermal manifestations. This shows that the development speed of geothermal resources in China generally coincides with the development speed of national economy. In a period to come, China's economy will continue to grow. Based on the present volume of exploitation, it is estimated that if the annual increase rate of national economy is 10 % , then 1.18301 million m3/d geothermal water with 2,638.40 MW heat energy should be exploited in the year 2000 and 2.33515 million m3/d geothermal water with 4,637.16 MW will be needed in the year 2010(Table 2.5.10).

Table 2.5.10 China's estimated demands for geothermal resources in 2000 and 2010

¢Ù Calculation at 5% annual increase rate, but at 10% for the other regions;¢Ú Based on available information only.

2.5.3.2 Trend

China is rich in geothermal resources but they are still at a low level of development. Up to now 761 geothermal fields have been explored or investigated(including 28 in Taiwan), and a reserve of 2.52377 million m3/d (or 921 million m3/a)of exploitable geothermal water with 4,333.89 MW heat energy, equal to the caloric value of 4.66901 million t/a of standard coal has been verified. Among the 761 geothermal fields, 434 have been developed at different levels, where 944,000 m3/d(or 345 million m3/a)geothermal water with 1,771.07 MW heat energy is pumped out and utilized, that is, the colaric value similar to 1.9057 tons of standard coal is consumed. However, up to now only 37.4% of explored geothermal water resources have been exploited, showing that there is still potential for further development. In most provinces(autonomous regions and municipalities)explored geothermal resources can meet the demands of economic development in the year 2000.

In the 761 geothermal fields, only 126 have undergone detailed investigation and exploration , making up 16.6% of the total; over 600 have undergone only reconnaissance survey and investigation, which means a large potential of exploitation and development is remained. Based on the present volume of exploitable geothermal water in the currently highly developed geothermal fields, that is, 10, 000 m3/d in large geothermal fields, 3,000~5,000 m3/d in medium?size ones and 1,000m3/d in small ones, it is estimated that a total of 3.3357 million m3/d of geothermal water or 6,855.48 MW heat energy may be obtained from the 761 geothermal fields when the exploration and development is upgraded. This volume can meet the demands for geothermal resources at China's economical growth rate of 10% in the year 2010(Table 2.5.11).

Table 2.5.11 Estimated value of perspective exploitable resources of existing geothermal fields in China

China is rich in geothermal resources of low?moderate temperature which have a great potential for development. However, owing to the restriction of technological and economical conditions at present, only a small part of geothermal resources has been exploited. Based on analysis of operational data arising from several basin?type geothermal fields, the exploitable amount of geothermal resources accounts only for 1%~2% of the stored quantity of heat(estimated by an operation life of 100 years). Increasing exploitation will speed up the lowering of the geothermal water level and reduce the operation life. Besides, development of geothermal resources requires a lot of capital investment. Now geothermal resources are developed by way of pumping geothermal water directly from wells and at present time some RMB 3 million yuan are needed for drilling a well of 2,000 m deep and purchasing the pumping equipment. If pumpage of geothermal water of 75¡æ is 1,500~2,000 m3/d , the total useable quantity of geothermal heat per year will be equal to that of 4,000~5,000t standard coal. This shows that to increase exploitation capacity of every 10,000t standard coal, an investment of RMB 6~7.5 million yuan is needed. Without sufficient capital investment, it is impossible to upgrade the development of geothermal resources.

China's economy is now in a period of rapid development. A new demand for geothermal resources has been brought about by the requirements of economic development and environment protection. The general tendency is: for geothermal fields which have been exploited for years, such as the geothermal fields in Beijing and Fuzhou, long?term development program of geothermal resources will be worked out while the operational management is strengthened to maintain a balanced exploitation. Efforts will be made to explore geothermal resources in the deep parts of geothermal fields and adjacent area, and to expand the exploitation of geothermal resources so as to meet the increasing demand of society. In the areas where economy develops rapidly, for instance, the coastal economic zones, areas along the railway line from Beijing to Kowloon, Hong Kong and the key economic development zones in western China, exploration and exploitation will be accelerated in geothermal fields with favorable conditions for development to promote the development of economy and tourism. Geothermal resources in some large sedimentary basins in northern and northeastern China will become the priority of exploration in the coming period. In many cities and towns in those basins, remarkable social and economic performances have already been achieved in recent years by using geothermal resources for heating, medical treatment, washing and bathe, aquaculture, greenhouse agriculture and tourism. In the future much attention will be paid continuously to the development of geothermal resources. Influenced by those examples, other cities and towns will follow suits to promote development of geothermal resources. In oilfield areas development of geothermal resources will also be emphasized. Occurring in large sedimentary basins, many oilfields are both oilfields and geothermal fields. Some oil exploration wells there can be utilized as geothermal wells by themselves. Some oilfields where oil and gas resources are almost running out can be further used as geothermal fields. At present, trial experiments to exploit geothermal resources have begun in some oilfields(wells), The shifting of a part of the numerous oil fields(wells)to geothermal fields for the development of geothermal resources  will surely quicken the pace of the overall geothermal resources development in China.

It can be envisaged that China will enter a period of rapid development of geothermal resources .