CO₂ geological storage is a key technology for reducing greenhouse gas emissions. But merely injecting CO₂ into sedimentary strata has high costs and no direct economic benefit. A more cost-effective and environment-friendly way is storing and utilizing CO₂ in deep sedimentary reservoirs for heat extraction. However, the effects of ubiquitous impurities on the sequestration safety and heat extraction performance of CO₂ in high-temperature reservoirs, are unclear. In this study, we have performed numerical simulations of multiphase flow, solute transport, and heat conduction at reservoir temperature 50–250 °C, to reveal the effects of two common impurities (i.e., H₂S and N₂) on the migration, dissolution and thermal absorption of CO₂ in sedimentary geothermal reservoirs. It is found that, for higher reservoir temperature, the impurity N₂ leads to smaller promotion on the migration of gas phase, but retains the acceleration effect on the cooling in reservoir. Above 150 °C, the deviations on the gas phase migration velocity and the CO₂ dissolution efficiency caused by 10 mol% N₂ are less than 12%. Meanwhile, the 10 mol% N₂ can increase the total heat absorbed from reservoir by about 40% at least. It means that N₂ has the potential to benefit a CO₂ plume geothermal system significantly without distinct risks. Besides, it is also found that the CO₂ dissolution efficiency can be increased and decreased by H₂S and N₂ through partitioning phenomenon, respectively.

CO ₂地质封存是减少温室气体排放的关键技术。但仅仅将CO ₂注入沉积地层成本高，没有直接的经济效益。一种更具成本效益和环境友好性的方法是在深层沉积储层中储存和利用 CO ₂以提取热量。然而，普遍存在的杂质对高温储层中CO ₂的封存安全性和热提取性能的影响尚不清楚。在本研究中，我们对储层温度 50–250 °C 下的多相流、溶质输运和热传导进行了数值模拟，以揭示两种常见杂质（即 H ₂ S 和 N ₂) 对沉积地热储层中 CO ₂的迁移、溶解和吸热。研究发现，对于较高的储层温度，杂质N ₂对气相运移的促进作用较小，但保留了对储层冷却的加速作用。150°C以上，10 mol% N ₂引起的气相迁移速度和CO ₂溶解效率的偏差小于12%。同时，10 mol%的N ₂至少可使储层吸收的总热量增加约40%。这意味着 N ₂有可能使 CO ₂羽状地热系统显着，没有明显的风险。此外，还发现H ₂ S和N ₂通过分配现象分别可以增加和降低CO ₂溶解效率。