Experiments and Simulations on Plume Spreading by Engineered Injection and Extraction in Refractive Index Matched Porous Media

Abstract

Reactive transport, the coupled set of processes that control the source, movement, reaction, and fate of solutes in porous media, is fundamental to a range of geophysical processes including soil weathering, element cycling, in-situ mining, and groundwater remediation. Because reactive transport depends on hydrological, microbiological, geochemical, and physical processes, it constitutes a major branch within the broad and interdisciplinary heading of hydrobiogeochemistry (Meile & Scheibe, 2019). Here we focus on physical processes, specifically fluid velocity, on the premise that biogeochemical processes depend on the delivery of reagents and the removal of wastes that are provided almost entirely by fluid advection (Kitanidis, 2012).A particular motivation for this work is groundwater remediation, the art and science of sequestering or destroying contaminants in aquifers, the geologic structures that store and transmit useful quantities of water for municipal, industrial, and environmental purposes. Groundwater remediation often calls for an amendment to be introduced into the aquifer. Successful in-situ remediation requires that the remediation amendment and contaminant occupy the same pore space, at which point molecular diffusion permits the desired reaction (Kitanidis, 1994). In other words, reaction requires mixing, the result of molecular diffusion, which increases the volume into which mass is dissolved and consequently provides dilution. In contrast, spreading is defined as solute redistribution by advection, on any scale, without dilution, depending entirely on the velocity field. Spreading enhances mixing by increasing the interfacial area between plumes of differing chemical composition, and by sharpening the concentration gradients at the plume interface, both of which serve to increase mass transport by molecular diffusion (Le Borgne et al., 2010;Villermaux, 2019; Section 2.2). An elegant example of improved remediation through improved spreading has recently been provided by Ye et al. (2021), who used multi-screen wells to inject multiple amendment plumes with correspondingly increased interfacial area. Moreover, spreading takes place at the plume scale, which is an important distinction, because numerical and theoretical studies have shown that different processes dominate at the pore scale versus the plume scale (Jose & Cirpka, 2004).

Enhancing Mixing During Groundwater Remediation via Engineered Injection‐Extraction: The Issue of Connectivity

“…EIE schemes increase the active spreading and the area occupied by the injected fluid in aquifers, favoring mixing and accelerating the natural attenuation and degradation of contaminants. The benefits of this strategy has been proven for many configurations of extraction/injection wells through numerical simulations (e.g., Di Dato et al., 2018; Neupauer et al., 2014; Piscopo et al., 2013; Speetjens et al., 2021), laboratory experiments (e.g., Sather et al., 2023; Zhang et al., 2009) and field applications (Cho et al., 2019). Most recently, EIE has also been demonstrated to enhance NAPL recovery in multiphase flow systems (Wang et al., 2022).…”

“…of extraction/injection wells through numerical simulations (e.g., Di Dato et al, 2018;Neupauer et al, 2014;Piscopo et al, 2013;Speetjens et al, 2021), laboratory experiments (e.g., Sather et al, 2023;Zhang et al, 2009) and field applications (Cho et al, 2019). Most recently, EIE has also been demonstrated to enhance NAPL recovery in multiphase flow systems (Wang et al, 2022).…”

A Low‐Cost Programmable Reversing Flow Column Apparatus for Investigating Mixing Zones

“…This lack of physical models may be owed to the lack of a cost‐effective and adaptable general‐purpose apparatus. Physical model applications that have been described in publications include devices that simulate push–pull tests and multiwell remediation (Sather et al 2023), apparatuses simulating oscillating water tables (Rezanezhad et al 2014; Xin et al 2018) and reversing flow 1D column experiments (Liu et al 2017; Li et al 2020).…”

Thermally Enhanced Spreading of Miscible Plumes in Porous Media

“…In this context, mass transport by transverse dispersion is known to be an important process [1]. By contrast, active spreading results from the deliberate manipulation of the velocity field through an approach called engineered injection and extraction, for example, through vertically separated segments of the well screen [2] through a manifold of wells [3,4] confirmed by laboratory testing [5,6], or through a rotated dipole mixer [7] confirmed by field testing [8]. The present study proposes a new approach to active plume spreading by heating the injected water.…”