Wormholing in Anisotropic Media: Pore‐Scale Effect on Large‐Scale Patterns

Abstract

Focused reactive flow and dissolution in fractured or porous media leads to the emergence of highly conductive dissolution conduits, so-called "wormholes" (Daccord et al., 1993;Hoefner & Fogler, 1988). Dissolution conduits are prevalent in subsurface karst, and can form extended speleological systems (Dreybrodt et al., 2005;Palmer, 1991). Wormholes are also important in several other applications, including CO 2 geo-sequestration (Deng et al., 2016), risk assessment of groundwater contamination (Fryar & Schwartz, 1998) or stimulation of petroleum reservoirs (Panga et al., 2005).The underlying mechanism involves positive feedback between reaction and transport-the pathways that focus the reactive flow dissolve preferentially, increasing their conductivity, and in turn focusing more flow. Concurrently, shorter wormholes are progressively drained and screened off by the longer wormholes, and ultimately cease to grow, resulting eventually in the appearance of hierarchical, scale-invariant distribution of wormhole lengths (Szymczak & Ladd, 2006

Effects of Mixing at Pore Intersections on Large‐Scale Dissolution Patterns and Solute Transport

“…To investigate the coupling between the pore‐scale mixing processes and macroscopic dissolution patterns, we use the capillary pore network model of a dissolving porous medium. Network models introduce a simplified representation of a porous material, either as a network of interconnected capillaries (Budek & Szymczak, 2012; Hoefner & Fogler, 1988; Roded et al., 2020, 2021) or as spherical pore bodies connected by cylindrical throats (Blunt et al., 2013; De Boever et al., 2012; Nogues et al., 2013; Raoof et al., 2012; Tansey & Balhoff, 2016; Xiong et al., 2016), offering a compromise between the computational accuracy characterizing the pore‐scale models and the ability to tackle large‐scale problems, which are the advantages of Darcy‐scale methods. Pore‐network models allow for control of the pore architecture (diameters, lengths, connectivity), tuning it to represent different rocks.…”

“…In this study, we represent a porous rock as a network of cylindrical capillaries (of initially heterogeneous sizes) that are broadened by the dissolution (Budek & Szymczak, 2012; Hoefner & Fogler, 1988; Roded et al., 2021). The nodes of the network (pore junctions) are assumed to be volumeless such that all the reaction takes place in the capillaries (pores) only.…”

“…In dissolution problems, pore network models are able to correctly reproduce the competition between the individual pores for the reactant flux, which leads to a successful representation of the variety of spontaneously formed dissolution patterns such as wormholes (Ameri et al., 2017; Budek & Szymczak, 2012), including their structure and advancement rate, permeability evolution, and the non‐monotonic relationship between injection rate and fluid volume required for breakthrough (Budek & Szymczak, 2012; Fredd & Fogler, 1998; Hoefner & Fogler, 1988). They were also successfully used to analyze the link between pore‐scale features and large‐scale morphologies (Roded et al., 2020, 2021).…”

“…Understanding the effects of pore‐scale phenomena on larger‐scale processes has been of great interest for upscaling subsurface processes (Battiato & Tartakovsky, 2011; Hu et al., 2021; Kang et al., 2019). Recent studies indeed showed that macroscopic reactive transport can be governed by pore‐scale properties such as pore network structure and pore‐scale mineral distribution (Li et al., 2007; Roded et al., 2021). Also, pore‐scale transport processes such as mixing are shown to greatly affect effective surface reaction rates (Deng et al., 2018; W. Lee et al., 2023; Li et al., 2006; Liu et al., 2022).…”

Surface‐Volume Scaling Controlled by Dissolution Regimes in a Multiphase Flow Environment

“…When the reactive fluid is in contact with rock, chemical reactions at fluid‐rock interfaces will alter the pore structure and significantly impact the geochemical and geophysical properties (Hu et al., 2021, 2023; T. Wang et al., 2022). For example, the caprock security at a GCS site is primarily influenced by the dissolution of the formation, which is determined by rock mineralogy (Al‐Khulaifi et al., 2019), structure heterogeneity (Deng et al., 2018; Roded et al., 2021; Y. Zhang et al., 2022; Zhou et al., 2022), and length scale (L. Li et al., 2008).…”