We take three flow simulators, all based on Darcy’s Law but with different numerical solver implementations, to assess some of the issues surrounding their use to model underground CO₂ storage. We focus on the Sleipner CO₂ injection project, which, with its seismic monitoring datasets, provides unique insights into CO₂ plume development during a large-scale injection operation. The case studies firstly compare simulator performance in terms of outputs and run-times on carefully matched model scenarios; then we compare numerical with analytical Darcy solutions to explore the potential for modelling simplification; finally we look at the effects of including conservation of energy in the simulations. The initial case-study used simplified axisymmetric model geometry to simulate the upward flux of CO₂ through a heterogeneous reservoir, incorporating multiphase flow with coupled CO₂ dissolution into formation brine. All three codes produced near-identical results with respect to CO₂ migration velocity and total upward CO₂ flux at the reservoir top. The second case-study involved 3D modelling of the growth of the topmost layer of CO₂ trapped and migrating beneath topseal topography. Again the three codes showed excellent agreement. In the third case-study the simulators were tested against a simplified analytical solution for gravity currents to model the spreading of a single CO₂ layer beneath a flat caprock. Neglecting capillary effects, the numerical models showed similar layer migration and geometry to the analytical model, but it was necessary to minimise the effects of numerical dispersion by adopting very fine cell thicknesses. The final case-study was designed to test the non-isothermal effects of injecting CO₂ into a reservoir at non-ambient temperature. Only two of the simulators solve for conservation of energy, but both showed a near identical thermal anomaly, dominated by Joule-Thomson effects. These can be significant, particularly where reservoir conditions are close to the critical point for CO₂ where property variations can significantly affect plume mobility and also seismic response. In conclusion, the three simulators show robust consistency, any differences far less than would result from geological parameter uncertainty and limitations of model resolution. In this respect the three implementations are significantly different in terms of computing resource requirement and it is clear that approaches with simplified physics will pay rich dividends in allowing more detailed reservoir heterogeneity to be included. Contrary to this, including conservation of energy is heavier on computing time but is likely to be required for storage scenarios where the injectant stream is significantly different in temperature to the reservoir and most critically for shallower storage reservoirs where CO₂ is close to its critical point.

我们采用了三个流量模拟器，它们都基于达西定律，但是具有不同的数值求解器实现方式，以评估围绕其用于模拟地下CO ₂储存的一些问题。我们专注于Sleipner CO ₂注入项目，该项目及其地震监测数据集提供了对CO _2的独特见解。大规模注入操作过程中产生羽状流。案例研究首先在精心匹配的模型方案上比较了模拟器在输出和运行时间方面的性能；然后，我们将数值和解析达西解决方案进行比较，以探索简化建模的潜力；最后，我们看一下在仿真中包含能量守恒的效果。最初的案例研究使用简化的轴对称模型几何形状来模拟通过非均质油藏的CO ₂的向上通量，将多相流与耦合的CO ₂溶解合并到地层盐水中。对于CO _2的迁移速度和总的向上CO _2，这三个代码都产生了几乎相同的结果。储层顶部的通量。第二个案例研究涉及3D建模，该3D建模是在顶部密封形貌下捕获和迁移的最顶层CO ₂的生长。再次，这三个代码显示出极好的一致性。在第三个案例研究中，针对简化的重力流分析解决方案对模拟器进行了测试，以模拟平坦盖层下单个CO ₂层的扩散。忽略毛细管效应，数值模型显示出与分析模型相似的层迁移和几何形状，但必须通过采用非常精细的像元厚度来最小化数值分散的影响。最后的案例研究旨在测试注入CO ₂的非等温效应在非环境温度下进入储层。只有两个仿真器解决了能量守恒问题，但都显示出几乎相同的热异常，主要受焦耳-汤姆森效应的影响。这些意义重大，尤其是在储层条件接近CO ₂临界点的情况下属性变化会显着影响羽流活动性以及地震响应。总之，这三个仿真器显示出鲁棒的一致性，任何差异远小于地质参数不确定性和模型分辨率的限制所导致的差异。在这方面，这三种实现方式在计算资源需求方面存在显着差异，而且很明显，具有简化物理学的方法将在允许包括更详细的油层非均质性方面付出可观的收益。与此相反，包括能源节省在计算时间上比较重，但是对于注入流与储层温度明显不同的存储场景，以及对于CO ₂较浅的储层而言最关键的存储场景，可能需要进行节能。 接近其临界点。