Modeling discontinuous gas flow for remediation in heterogeneous media

Paul R. Hegele, Kevin G. Mumford

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Geoenvironmental Engineering

ABSTRACT: During the remediation of contaminated soils and groundwater, gases can be trapped in the subsurface. When injected or produced at slow rates in coarse saturated media, discontinuous (bubbly) gas flow can occur, which is characterized by disconnected gas clusters which can fragment, mobilize and coalesce during buoyancy-driven migration. It is thought that discontinuous gas flow is advantageous during remediation because it has a higher gas-liquid interfacial area than continuous channels, thereby maximizing mass transfer in or out of the gas phase and increasing remediation efficiency. However, heterogeneities can cause pooling and lateral spreading of the gas, affecting its distribution and availability for mass transfer. In this study, a macroscopic invasion percolation model was used to simulate discontinuous gas flow in the presence of heterogeneities. It was found that heterogeneities can decrease relative mass transfer rates under conditions of slower flow, but can increase relative mass transfer rates under conditions of faster flow.

RÉSUMÉ: Pendant la produit, durant la réhabilitation -ol peut causer des accumulations ou un écoulement latéral du gaz affectant ainsi sa important flot, les hétérogénéités peuvent accroître le taux relatif du transfert de masse.

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