An ultra-diffusive leakage experiment was performed on the pilot site of Saint-Emilion near Bordeaux in France. It consisted in the injection of 85% CO₂ and 5% of each He, Kr and CH₄ in a vertical well with a very low injection pressure. This study allowed the development of an automated tool that continuously monitored the gas phase within the vadose zone. Measurements showed that the gas plume had a heterogeneous spatial and temporal variation. Mathematical calculations performed on the time series of the gas species showed that diffusive transport mainly occurred in the porous media. However, every stage of the migration could not be driven by diffusive process as shown by the exponential regression. A non-identified transport mechanism may have occurred during the increase of concentration. He was proven to be a suitable temporal tracer for a CO₂ leakage as it was a good temporal precursor. Even if the process was weaker than in the former injection experiments, Kr could show help foreseeing the extent of the gas plume within the pilot site. CH₄ was also shown to be an excellent temporal precursor of CO₂ arrival. The amount of gas migrating through the preferential path identified in the previous experiment was weaker than in the previous study. Moreover, the monitoring showed that a significant amount of injected gas migrated deeper in the vadose zone. The ratios CO₂/Kr vs. CO₂/He and the evolution of CO₂/Kr, CO₂/He and CO₂/CH₄ put in evidence three groups of probes. The first consists in the subsurface probes and is characterized by a potential reactive transport of _CO2 through the vadose zone such as gas dissolution in the aqueous phase. The second group gathers the closest probes to the injection point and underlines a very slow return to baseline value through diffusion. The third group is characterized by a competition between the process occurring in the first and second group. Isotopic measurement of Kr could not bring relevant information about the CO₂ fates into the vadose zone. However, it shows the possible presence of mechanism transport such as vertical flux and gravitational settlings. Observations from both of all the leakage experiment and future laboratory experiment could improve our understandings of the buffering zone and help to foresee CO₂ leakage for future storage site.

在法国波尔多附近的圣埃美隆试验场上进行了超扩散泄漏试验。它包括注入85％的CO ₂和5％的He，Kr和CH ₄的注入注入压力非常低的垂直井中。这项研究允许开发一种自动工具，该工具可以连续监测渗流区内的气相。测量表明，气羽具有不均匀的时空变化。对气体种类的时间序列进行的数学计算表明，扩散传输主要发生在多孔介质中。但是，迁移的每个阶段都不能由扩散过程驱动，如指数回归所示。浓度增加期间可能发生了未知的转运机制。他被证明是适合CO _2的时间示踪剂泄漏，因为它是良好的暂时先兆。即使该过程比以前的注入实验要弱，Kr仍可帮助预见试验地点内气体羽流的范围。CH ₄也被证明是CO ₂到达的极好的时间先兆。通过先前实验中确定的优先路径迁移的气体量比先前研究中的弱。此外，监测表明大量的注入气体在渗流带中迁移得更深。CO ₂ / Kr与CO ₂ / He的比率以及CO ₂ / Kr，CO ₂ / He和CO ₂ / CH ₄的演变提供了三组探针作为证据。第一种是地下探针，其特征是_二氧化碳通过渗流带的潜在反应性传输，例如气体溶解在水相中。第二组收集最接近注入点的探针，并强调通过扩散非常缓慢地返回基线值。第三组的特征在于在第一组和第二组中发生的过程之间的竞争。同位素Kr测量无法带来有关CO _2的相关信息进入渗流区。但是，它表明可能存在机械传输，例如垂直通量和重力沉降。从所有泄漏实验和未来实验室实验中获得的观察结果可以增进我们对缓冲带的了解，并有助于预见未来存储地点的CO ₂泄漏。