Geothermal energy resources are considered to be one of the main contributors to clean, renewable and low-risk energy production. However geothermal power production may result in some greenhouse gas (GHG) emissions. Injection of GHGs into geothermal reservoirs can be used to reduce these emissions, providing reservoir pressure support and possibly improve reservoir permeability.

To understand the migration and behavior of injected gases in the reservoir and to forecast gas breakthrough, simulation studies are required. This work investigates the possible impacts of infield reinjection of CO₂ in two-phase liquid-dominated geothermal reservoirs using an earlier 3D numerical model of the Wairakei-Tauhara system as a representative case study. Wairakei-Tauhara is an interesting case study as it has been operated with no reinjection for most of its lifetime. The work investigated the impact of various scenarios of separated geothermal water and CO₂ reinjection on reservoir sustainability. The breakthrough of CO₂ was also monitored since it can result in higher gas production and lower power generation. The modelling results showed that the injection of CO₂-water mixture helps to maintain the reservoir’s pressure, but, at the same time, it may suppress natural recharge and boiling, which results in reduction of the enthalpy of the produced fluid.

地热能源被认为是清洁，可再生和低风险能源生产的主要贡献者之一。但是，地热发电可能会导致一些温室气体（GHG）排放。可将GHG注入地热储层中以减少这些排放，从而提供储层压力支持并可能改善储层渗透率。

为了了解储层中注入气体的运移和行为并预测气体突破，需要进行模拟研究。这项工作使用怀拉基-陶拉哈系统的早期3D数值模型作为代表性案例，研究了在两相液体为主的地热油藏中CO ₂的野外回注的可能影响。Wairakei-Tauhara是一个有趣的案例研究，因为它在整个生命周期中都无需重新注入即可进行操作。这项工作研究了分离的地热水和再注入CO ₂的各种方案对储层可持续性的影响。CO ₂的突破还对其进行了监控，因为它可能导致更高的天然气产量和更低的发电量。模拟结果表明，注入CO _2-水混合物有助于维持油藏压力，但同时也可能抑制自然补给和沸腾，从而降低了产出液的焓。