Research On Chemical Blocking Mechanism Of Recharge Of Geothermal Tailwater In Sandstone Reservoir

Geothermal resources as a new type of green environmental protection resources that can be developed and utilized by people and have great development prospects are one of the important contents of China's energy development strategies and policies.The recharge of geothermal resources is the key to the sustainable utilization of this green energy.However,during the recharge process,some geothermal recharge wells are blocked,the ground pressure of the recharge increases,and the rate of recharge decreases,which affects the geothermal energy.The ultimate goal of sustainable development and utilization research has also become an urgent problem to be overcome in the current worldwide sandstone reservoir.It is necessary to find out the mechanism of geothermal recharge blockage and formulate corresponding anti-blocking measures in order to achieve stable recharge mining and continuous recycling of geothermal resources.The thesis selected the Lubei thermal storage area in Shandong Province as the research object.Based on the on-site investigation and sampling,it carried out indoor experimental research and hydrogeochemical simulation.The PHREEQC software was used to simulate the law of dissolution and precipitation of minerals.The chemical affinity between the heat source water and the tail water reveals the influence of the thermal storage medium on the chemical blockage by the one-dimensional sand column test.The two-dimensional sand tank test is used to understand the temporal and spatial development of the chemical blockage.The mechanism has certain guiding significance for promoting the sustainable development of geothermal resources.The results show that the minerals that may be related to chemical clogging in Lubei area are quartz and chalcedony,carbonate minerals are calcite,dolomite,and aragonite,and sulfate minerals are gypsum.Carbonate minerals will increase the probability of clogging with increasing temperature and increasing pH;increasing temperature will reduce the clogging probability of silicate minerals,and the dissolution tendency of sulfate minerals will be reduced,and pH changes will have little effect on the two.;The oxidation-reduction potential has little effect on the dissolution and precipitation tendency of the studied minerals.The compatibility of geothermal source water and tail water in Lubei area is good.The local heat recharge tail water meets the geothermal source water in the reservoir.The larger amount of tail water mixes with the source water.The chemical precipitation amount generated at the moment of mixing is largest,The precipitate is calcite.Increased temperature is more conducive to the formation of calcium carbonate precipitation,that is,the tendency of calcite precipitation to increase.The heat storage medium will have a certain impact on the water quality of the recharge tailwater in the early stage of recharge,but the impact of the heat storage medium on the water quality of the recharge water gradually decreases with the recharge,until it is negligible.In the process of geothermal tailwater recharge,the relative permeability coefficient gradually decreases,and the decrease decreases with time.The closer to the water inlet,the faster the blockage,the more obvious the phenomenon,and the more serious the blockage.