Characterizing the Impact of Fractured Caprock Heterogeneity on Supercritical CO$$_2$$ Injection

Abstract

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 .

Exploring the Impacts of Source Condition Uncertainties on Far‐Field Brine Leakage Plume Predictions in Geologic Storage of CO2: Integrating Intermediate‐Scale Laboratory Testing With Numerical Modeling

“…Given the findings of Hyman et al. (2020), discussed in the introduction, it is recommended to further explore the impact of uncertainty in fracture network structure on brine migration using a larger scale problem domain.…”

Scale‐Bridging in Three‐Dimensional Fracture Networks: Characterizing the Effects of Variable Fracture Apertures on Network‐Scale Flow Channelization

“…Rather, these increases are the result of alterations in the network-scale flow field, as seen in changing FTG structures of Figure 3. Figure 4c reports the distribution of active surface area from the ensemble defined as the ratio of surface area where there is significant flow over total surface area (Hyman et al, 2020;Maillot et al, 2016). We generated an additional 90 networks with constant apertures so the number of samples in the two distributions (constant and variable) is the same.…”

Stress Effects on Flow and Transport in Three‐Dimensional Fracture Networks

“…Conceptually, the backbone of the fracture network, alternatively referred to as the primary subnetwork, is the set of fractures where the majority of flow and transport occurs. Backbone membership, however, is nonunique and depends dynamically on several factors including the direction of the driving force (Grindrod & Impey, 1993; Neuman, 2005) and multiphase fluid properties (Birkholzer & Tsang, 1997; Datta et al., 2013; de Gennes, 1983; Hyman et al., 2020; Jiménez‐Martínez et al., 2016, 2020). We do not consider these other factors and instead focus solely on how the background stress field influences backbone membership due to restructuring of the flow field within the fracture network.…”