We present a set of multiphase flow simulations where supercritical CO$$_2$$ (scCO$$_2$$) displaces water at hydrostatic conditions within three-dimensional discrete fracture networks that represent paths for potential leakage through caprock above CO$$_2$$ storage reservoirs. The simulations are performed to characterize and compare the relative impact of hydraulic and structural heterogeneity in fractured media on the initial movement of scCO$$_2$$ through these caprock formations. In one scenario, intrinsic fracture permeabilities are varied stochastically within a fixed network structure. In another scenario, we generate multiple independent, identically distributed network realizations with varying fracture network densities to explore a wide range of geometric and topological configurations. Analysis of the simulations indicates that network structure, specifically connectivity and the presence of hanging fractures, plays a larger role in controlling the displacement of water by scCO$$_2$$ than variations in local hydraulic properties. We identify active surface area of the network as a single-phase feature that could provide a lower bound on the percentage of the network surface area reached by scCO$$_2$$.

中文翻译：

---

表征破裂盖层非均质性对超临界 CO$$_2$$2 注入的影响

我们提出了一组多相流模拟，其中超临界 CO$$_2$$ (scCO$$_2$$) 在三维离散裂缝网络中的流体静力条件下置换水，代表通过 CO$$_2$ 以上盖层的潜在泄漏路径$储水库。进行模拟以表征和比较裂缝介质中的水力和结构非均质性对 scCO$_2$$ 通过这些盖层地层的初始运动的相对影响。在一种情况下，固有裂缝渗透率在固定网络结构内随机变化。在另一个场景中，我们生成多个独立的、同分布的网络实现，具有不同的裂缝网络密度，以探索广泛的几何和拓扑配置。模拟分析表明，网络结构，特别是连通性和悬垂裂缝的存在，在控制 scCO$$_2$$ 对水的置换方面比局部水力特性的变化起着更大的作用。我们将网络的活动表面积识别为单相特征，可以为 scCO$$_2$$ 所达到的网络表面积百分比提供下限。