Three-dimensional numerical modeling of steam override observed at a full-scale remediation of an unconfined aquifer

Steam injected below the water table tends to move upward because of buoyancy. This limits the horizontal steam zone development, which determines the optimal spacing between injection wells. In this study, observations indicating steam override at a full-scale remediation of an unconfined aquifer are analyzed by numerical modeling using the code T2VOC. A simplified three-dimensional (3D) numerical model is set up, which qualitatively shows the same mechanisms as observed at the site. By means of the model, it is found that it will be possible to achieve a larger horizontal extent of the steam zone in a layered geology compared to the homogeneous case. In the homogeneous case, the steam injection rate increases dramatically when the injection pressure is increased, which is necessary to achieve a larger horizontal development. The development of the steam zone under unconfined conditions is found to be a complex function of the geologic layering, the water table at steady-state extraction, and the injection/extraction system. Because of this complexity, it will be difficult to predict steam behavior without site-specific 3D numerical modeling.