Uncertainty in the long-term fate of CO₂ injected for geologic carbon sequestration (GCS) is a significant barrier to the adoption of GCS as a greenhouse-gas emission-mitigation for industry and regulatory agencies alike. We present a modeling study that demonstrates that the uncertainty in forecasts of GCS site performance decreases over time as monitoring data are used to update operational models. We consider a case study of GCS in a depleted natural gas reservoir, with CO₂ injection occurring over 20 years, with a 50-year post-injection site care period. We constructed a detailed model to generate the actual model output, which is considered synthetic observation data. A series of simpler operational models based on limited data and assumptions about how an operator would model such a site are then run and compared against actual model output at specific monitoring points after one year, two years, etc. The operational model is updated and improved using the synthetic observation data from the actual model at the same time intervals. Model parameter values and model features needed to be updated over time to improve matches to the actual model. These kinds of model adjustments would be a normal part of reservoir engineering and site management at GCS sites. Uncertainty in two key measures related to site performance decreases with time: extent of the CO₂ plume up-dip migration, and radial extent of the pressure pulse. This conclusion should help allay the concerns of industry and regulators about uncertainty in long-term fate of CO₂ at GCS sites.

地质碳封存（GCS）注入的CO ₂的长期命运的不确定性是将GCS用作工业和监管机构的温室气体减排的重要障碍。我们提供了一项模型研究，该研究表明，随着监测数据用于更新运营模型，GCS站点性能预测的不确定性会随着时间的推移而降低。我们考虑了一个天然气枯竭储层中GCS的案例研究，CO ₂注入发生了20年，注入后现场护理期为50年。我们构建了一个详细的模型以生成实际的模型输出，该输出被视为综合观测数据。一系列更简单的操作然后运行基于有限数据的模型以及关于运营商将如何对此类站点进行建模的假设，并在一年，两年等之后将其与特定监视点的实际模型输出进行比较。使用综合观察数据来更新和改进运营模型从相同时间间隔的实际模型中获得。模型参数值和模型特征需要随时间更新，以改善与实际模型的匹配。这些类型的模型调整将是GCS站点水库工程和站点管理的常规部分。与现场性能相关的两个关键指标的不确定性随着时间的推移而降低：CO _2的程度羽状流的上倾迁移和压力脉冲的径向范围。该结论应有助于缓解行业和监管机构对GCS站点CO ₂长期命运不确定性的担忧。