Steam migration and temperature distribution in aquifers during remediation using steam injection

Steam injection technology is commonly used to rapidly remove volatile and semi-volatile organic pollutants in aquifers, and its remediation effect is highly related to steam migration and temperature distribution. However, systematic studies on steam migration and temperature distribution across different types of aquifers are lacking. In this study, the steam migration and temperature distribution in an aquifer were investigated through a series of two-dimensional sandbox experiments with different groundwater velocities, steam injection flow rates, and stratigraphic structures. The experimental results indicated that the temperature distribution in the aquifer was related to the formation permeability and steam injection flow rate. When the hydraulic conductivity of the aquifer was lower than 10^-3 cm·s^-1, the heating zone in the aquifer had an H-shaped distribution, and when it was higher than 10^-2 cm·s^-1, the heating zone had a V-shaped distribution for a high steam injection flow rate (1 kgh^-1), and an H-shaped distribution for a low injection flow rate (0.5 kgh^-1). Under the same injection steam flow rate, the total area of the heating zone in the aquifers with different media was in the following order of sand particle size: coarse sand > fine sand > medium sand. Owing to the heat pipe and heat dispersion effects, the heating zone area in the fine sand aquifer was larger than that of the medium sand aquifer. Groundwater velocity did not affect the area of the heating zone. With the increase in groundwater velocity, the heating zone expanded downstream. In layered heterogeneous aquifers, the upper fine and lower coarse structures formed a steam-blocking interface, resulting in steam accumulation and temperature increase in the lower layer. These findings are significant for improving our understanding of steam migration and temperature distribution in aquifers, leading to an improved design and prediction of the steam remediation required for mitigating aquifer pollution.