CO2泄漏停止后天然条件下浅层含水层的自我修复能力评价

摘要

Because of the unknown faults,fractures in the cap rock,the deep stored CO2 may move upward,the intrusion will impact shallow groundwater quality.After the leakage stopped,the affected aquifer may show self-repair capacity under the natural flow field.In this study,an injection test field was selected as example,and the reactive transport modeling software TOUGHREACT was used to simulate the self-repair capacity.The simulation results showed that,the intrusion of leaked CO2 would decrease the pH of target aquifer,and trigger the dissolution of carbonate minerals.After the leakage stopped,the pH would be increased under natural conditions,but the concentration of Ca would increased because of the dissolution of calcite along the flow path,which means the self-repair capacity of target aquifer is not good enough to scavenge the impacts of CO2 leakage.%由于盖层中可能存在未知断层和裂隙或被废弃井穿透，储存于深部地层的 CO2会发生向上运移泄漏影响浅层地下水水质，在天然流场的作用下，受影响含水层在泄漏停止后，可能表现出一定的自我修复能力。以美国某野外试验场地为例，以 TOUGHREACT 软件为平台，模拟分析当 CO2泄漏停止后含水层的自我修复能力。结果表明：CO2泄露进入含水层会降低地下水中的 pH 值，从而引起地下水中碳酸盐矿物（本次研究中为方解石矿物）的溶解发生；当泄漏停止后，在天然流场的作用下，地下水中 pH 值逐渐回升，说明天然条件下的含水层对 pH 值具有一定的自我修复能力，但在修复过程中，由于沿途方解石矿物的溶解，使得地下水中 Ca 的浓度值逐渐升高，研究区天然流场对地下水中的 Ca 修复效果不佳。