InterPore2025

Mechanisms of foam transport and the role of injection parameters: A path to efficient remediation

19 May 2025, 14:20

15m

Oral Presentation (MS18) Innovative Methods for Characterization, Monitoring, and Remediation of Contaminated Soils and Aquifers MS18

Speaker

Dr Adil Baigadilov (BRGM: French geological survey)

Description

Soil and aquifer contamination by pollutants, including non-aqueous phase liquids (NAPLs) and per- and polyfluoroalkyl substances (PFAS), poses a severe threat to the environment and water resources. Conventional remediation methods often achieve limited recovery efficiencies, underscoring the need for innovative and scalable technologies [1 - 2]. Aqueous foam, a fascinating two-phase fluid with a microstructure that profoundly influences flow behavior in porous media [3], offers a promising solution. However, maximizing remediation efficiency requires a deeper understanding of the complex dynamics of foam flow within subsurface environments, such as trapping and mobilization [4 - 6]. The main objective of this study is to provide new insights into the mechanisms governing foam flow in unconsolidated porous media as a precursor to the wider application of this technology.
The study introduces a novel experimental setup to investigate the flow of pre-generated foam composed of a Sodium Dodecyl Sulfate (SDS) and Cocamidopropyl Hydroxysultaine (CAHS) surfactant blend combined with nitrogen gas (N${}_2$). Two injection protocols—fixed liquid flow and fixed gas flow—were employed to perform comprehensive foam quality (i.e., gas fractional flow) scans, assessing the influence of injection parameters on foam dynamics. The setup featured a 1D sandpack holder equipped with localized pressure and permittivity sensors, which allowed for the acquisition of pressure and saturation profiles along the system. High-resolution imaging enabled in-situ visualization of foam texture at the mesoscale (from pore to Darcy scale).
The results highlight the significant influence of gas compressibility on foam quality, emphasizing the importance of local pressure measurements for accurate assessment. Entrance and end effects were observed, underscoring the need to focus on internal sections of the porous medium for reliable interpretation of foam flow behavior. Foam quality scans revealed distinct low- and high-quality regimes, separated by a transition zone. Foam apparent viscosity showed a complex dependence on foam quality ($f_g$) and capillary number ($N_{Ca}$). Flowing and trapped foam fractions derived from local saturation measurements revealed a weak dependence on $N_{Ca}$ at lower $f_g$ (<0.85) and stronger at higher values. In-situ foam texture visualization captured dynamic variations in bubble size, highlighting the critical roles of lamellae division and bubble fragmentation in controlling foam mobility and flow uniformity.
This research advances foam-based remediation technologies by deepening our understanding of the mechanisms governing foam flow within porous media. By bridging laboratory-scale observations with practical applications, this study supports the establishment of aqueous foams as a viable tool for environmental remediation. Future work will focus on scaling these findings to heterogeneous field-like conditions, optimizing injection strategies, and expanding applications to diverse contaminants such as NAPLs and PFAS.