Clogging Mechanism And Tracer Technique Research Of Deep-porous Type Geothermal Water Re-injection

To achieve the virtuous cycle of sustainable development and utilization of geothermalresources and reduce the environmental pollution caused by the direct disposal ofgeothermal water, artificial reinjection of geothermal water is the inevitable way. However,clogging restricts artificial reinjection of geothermal water, especially in the type ofdeep-porous geothermal reservoir, the influence factor of used water reinjection clogging iscomplex and changeable, sustainable and efficient reinjection of used geothermal water isstill the world’s problems. Geothermal reinjection tracer test is one of the most important andmost intuitive methods to evaluate the effect of used water reinjection, analyze the migrationdirection and rate of reinjection water, find out the change of pressure field, water chemistryfield and temperature field before and after the injection, and make sure the “hotbreakthrough” between exploitation well and reinjection well. However, there is nosuccessful precedent in the tracer test study of domestic deep-porous geothermal reinjection.Therefore, deepening and perfecting the clogging mechanism and prevention measures ofdeep-porous reservoir and conducting systematic research of geothermal reinjection tracertest have important theoretical and practical significance on the sustainable development andprotection of geothermal reservoir, extending the life of geothermal fields andenvironment-friendly society construction.Selecting Xianyang deep-porous geothermal water as the research object under theinfluence of geothermal geology, hydrogeology and geothermal restraining the run ofreinjection well and based on the site investigation sampling test analysis, we apply thecombining method of hydrogeochemical theoretical simulation-indoor simulation test-field reinfection experiments and carry out the study of clogging mechanism and tracer testof used water reinjection in deep-porous reservoir. The study result of clogging mechanismshows the dissolution and precipitation rule of different types of minerals, the contribution ofsuspended matter clogging, chemical precipitation, particle migration, gas clogging for thereinjection clogging of the super-deep geothermal water and provides the suggestions ofpreventing reinjection clogging according to each clogging factors. Selecting ammonium thiocyanate as a tracer in the tracer tests, we are fully preparedand operating specifications. During the experiment, the tracer has not been founded,indicating that the connectivity between exploitation wells and reinjection well is poor andreinjection will not cause "hot breakthrough" during a short period of time.Some conclusions and understanding achieved in this study provide technical supportfor the prevention of used water reinjection clogging in the deep-porous geothermalreservoir, accumulate valuable experience for the future reinjection well tracer test andprovide a scientific basis for the sustainable use of deep-porous geothermal resources.