Engineered Well Injection and Extraction to Enhance Mixing in Aquifers

Remediation of contaminated groundwater may involve the injection of one or more reactants into the aquifer to stimulate degradation of contaminants, coupled with removal of water from an extraction well to increase circulation. Ideally, the reactants should be mixed throughout the contaminated area to optimize the reaction rate. However, due to the laminar flows characteristic in porous media, mixing in groundwater is an inherently slow process, governed by molecular diffusion. In particular, laminar groundwater flow is an example of potential flow, which implies that it is irrotational. In contrast, mixing occurs more readily in rotational flows, such as turbulent flow in streams. In these fields, a material line will be stretched and folded within the domain due to transient vortices. We investigate the possibility of applying this paradigm in aquifers. Specifically, we explore how well injection and extraction schemes can be engineered to create transient flows that lead to stretching and folding, and therefore mixing, within an aquifer.