| Abstract |
Tianjin is one of the few city in China carrying out the geothermal reinjection, the flowrate of geothermal reinjection is 1128x104m3/a by the end of 2012. With the development strengthening of geothermal resources, geothermal reinjection as an effective way to maintain resource sustainable development is increasing at different layers of geothermal reservoir. The Geochemical reaction is very complicated between different geothermal fluid, it is hard to understand and forecast the influence of geothermal exploitation and reinjection at different layers on fluid quality without the simulation of geochemical reaction. The research results show that the dynamic changes of hydrochemical field, temperature field and hydrodynamic field are correlative in the geothermal reservoirs. The temperature of reinjection fluids is lower than that of reservoir in the course of geothermal fluids reinjection, and the concentration of hydrochemical composition is probably different with that of fluid in geothermal reservoir, which not only affect hydrodynamic field and temperature field, but also may change the hydrochemical field of geothermal fluids, especially for the exploitation and reinjection happened at different layers. Although it is very difficult to use laboratory method to forecast the geochemical reaction of different chemical composition, however, geochemical simulating can effectively solve this problem. A doublet geothermal wells( JN-05 and JN-05B) at different geothermal layers were studied in this paper. . Simulation of different mixing ratio of geothermal fluid was conducted base on PHREEQC and water quality was compared with historical data. The results indicate that the mixed ratio of exploitation and reinjection fluids presents obvious positive correlation from 2003 to 2006, and being maintaine at 0.6:1-0.7:1 with the time passed. Moreover, the ion compositions of reinjection fluid is stable during 2003-2010, which means the geothermal reinjection has little influence on Wimishan reservoir. The research results is helpful to forecast the geochemical reaction in geothermal reinjection and could provide theoretical basis for the development and protection of geothermal resources. |