中文摘要：

在增强型地热系统（EGS）中，采用CO2替代水作为工质能够在利用低渗透性岩层中的地热能的同时埋存温室气体。本文使用TOUGHREACT软件建立二维EGS模型，对CO2工质在干热岩中的流动换热和固化进行了数值模拟。模型考虑了岩层中实际存在的孔隙水以及CO2-水-岩石三相间的化学反应，模拟时间为40年，得到了CO2质量流率、取热量随时间的变化，以及固化的CO2的空间分布随时间的变化。结果表明：与水相比，CO2能够从干热岩中获取更多的热量，并且拥有埋存温室气体的巨大潜力；CO2工质EGS系统更适合在渗透率高、温度高而孔隙率小、压力小的岩层应用，可获得更好的换热和固化效果。

英文摘要：

Using CO2 instead of water as working fluid in enhanced geothermal systems （EGS） could achieve COs sequestration as well as extract geothermal energy from low permeability geothermal resources （hot-dry-rock, HDR）. A 2-dimension model was developed to simulate an EGS using CO2 as working fluid. The fluid flow, heat transfer and COs sequestration were studied by numerical simulation. The original crevice water in the terrane and the chemical interactions of COs-water-rock were considered. The simulation time is 40 years. The changes of COs mass flow rate and heat extraction over time, as well as the space distribution of CO2 sequestration in the operation of COs-based EGS were obtained by the simulation. The results showed that C02 could extract more geothermal heat than water. For better performance, the COs-based EGS should be installed in the terrane with high permeability, high temperature, low porosity and low pressure.