Experimental and numerical modeling of CO2 leakage in the vadose zone.

This study presents the experimental and modeling results of CO₂ injection and transport in the vadose zone performed in PISCO2 facilities at the ES.CO2 center in Ponferrada (North Spain). During 46 days of experiments, 62.10 kg of CO₂ were injected through 16 micro-injectors in a 35 m³ experimental unit filled with sandy material. Monitoring and mapping of surface CO₂ flux were performed periodically to assess the evolution of CO₂ migration through the soil and to the atmosphere. Numerical simulations were run using TOUGH2 code with EOS7CA research module considering two phases (gas and liquid) and three components (H₂O, CO₂, air). Two layers (sand, gravel) and atmosphere boundary were implemented taking into account heterogeneous soils, homogeneous soil, rainfall, temperature, and liquid saturation to allow a better understanding of CO₂ behavior in the vadose zone. This combined experimental and modeling approach shows that CO₂ leakage in the vadose zone quickly comes out through preferential migration pathways and spots with the ranges of fluxes in the ground/surface interface from 2.5 to 600 g·m⁻²·day⁻¹. This gas channeling is mainly related to soil compaction and climatic perturbation. This has significant implications for design-adapted detection and monitoring strategies of early leakage in commercial CO₂ storage. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]