;Taking the extensively developed deep karst thermal reservoirs in Xiong'an New Area as the research object,this study uses PHREEQC to simulate the changes in hydrochemical components and the amounts of mineral dissolution and precipitation after injecting Baiyangdian surface water into the main exploited thermal reservoir—the Jixian Wumishan Formation karst thermal reservoir.According to the results,it can be seen that during the reinjection period,the chemical types of water from the reinjection well to the interior of the reservoir are sequentially HCO3·Cl-Na·Mg,HCO3·Cl-Na,C1·HCO3-Na and Cl-Na types,showing a transition from supply water to original reservoir water.This trend is mainly affected by advection and dispersion,but Mg2+,Ca2+,HCO3 are also controlled by factors such as water-rock reactions and pH,resulting in more complex trends.The dissolution and precipitation of minerals after reinjection mainly occur within a radius of 0.5m from the reinjection well,with the most obvious precipitation of calcite and dissolution of dolomite.These mineral reactions lead to a slight decrease in fracture porosity overall,but the change is limited and does not significantly affect rock permeability.Based on the types of changes in the geothermal reservoir caused by reinjection,four impact zones were delineated,namely the chemical impact zone,the seepage impact zone,the temperature impact zone,and the rock permeability impact zone,with the size of each impact zone decreasing in the order listed above.
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