Formation Of Geothermal Resources And Analyses Of Exploitation Regime Of Thermal Groundwater In The Urban Beijing Area

Geothermal resources are proved to be clean and cheap. The Beijing geothermal field is a famous geothermal field in China. It has abundant low-temperature geothermal resources and gains extensive applications. It is significant to research in storage capacity.The geothermal groundwater resources in Beijing which lies in the northern part of North China Plain are middle-low temperature and stored in sedimentary basin. The geothermal reservoirs are Proterozoic siliceous dolomite and the total thickness is above 5000 m. The heat insulation caprock is mainly composed of Mesozoic and Cenozoic, partly including shale of Meso-to-Neo Proterozoic. The deep circulation of the groundwater acquires heat from the earth's crust under normal geothermal gradient and the temperature of the water is between 20 and 89℃. In this paper we use the linear regression analyze, we found that the ratio of thermal heating is increased, so the dynamic water level has the disciplinarian, rise at the stop heating periods, but the collectivity current drop year after year.In this paper, we analyze the relationship of the structure character, geothermal reservoirs structure and geothermal storage capacity in urban area of Beijing. Make the quantificational analyze in geothermal storage capacity of urban geothermal field. Through those work we get the urban geothermal field average geo-temperature gradient is between 2-3℃. The transfer mode of bedrock geothermal reservoir layer is under the geological conditions control. In the front of the mountain area, circle alternate is intensive, the shallow geo-temperature gradient is on the low side. The geo-temperature gradient of the wells which are 3000m depth is 2.1-2.4℃/100m, we can conclude that the geo-temperature gradient of Beijing plain is low; it is under the global average. Now in the mine depth under the 4000m area, there is no geothermal water which temperature is 90℃higher, so it decide the Beijing plain is low temperature geothermal.Through the WATCH program, we use the different geothermometer to compare analyze. Use the geochemistry geochemistry, and the result of the different geothermometer calculate, alone with the data of mineral-liquor balance, prove the chalcedony geochemistry is more suitable to estimate the temperature of urban geothermal field. Calculations show that the 21 mine wells′s temperature based on chalcedony geochemistry is between 80.6℃-103.8℃, which is higher than any other wells in the field. We can conclude the highest temperature of urban geothermal area is in the middle of the depressed. There have the abundant geothermal develop potential in this area.