Experimental and numerical modeling of CO2leakage in the vadose zone

Abstract

This study presents the experimental and modeling results of CO 2 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 CO 2 were injected through 16 micro-injectors in a 35 m 3 experimental unit fi lled with sandy material. Monitoring and mapping of surface CO 2 fl ux were performed periodically to assess the evolution of CO 2 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 (H 2 O, CO 2 , 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 CO 2 behavior in the vadose zone. This combined experimental and modeling approach shows that CO 2 leakage in the vadose zone quickly comes out through preferential migration pathways and spots with the ranges of fl uxes 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 signifi cant implications for designadapted detection and monitoring strategies of early leakage in commercial CO 2 storage.