An empirical model to predict the distribution of iron micro-particles around an injection well in a sandy aquifer

The distribution of micro Fe particles injected into a porous medium via a well highly depends on flow velocity and slurry properties. Column experiments were conducted to predict the filtration behavior and, hence, the micro-iron distribution around a well. Packed-bed column experiments were conducted in different experimental conditions: seepage velocity, volume of injected suspension, iron particle and guar gum concentration (viscosity) were varied. Results are used to calculate a parameter "space removal efficiency" (η(space)). Space removal efficiency is defined as the fraction of particle concentration lost by the slurry (and retained by the porous medium) while it crosses a unit length of the porous medium. η(space) was found to be inversely proportional to seepage velocity and viscosity, while it is independent of the volume of injected slurry (or injection time) and particle concentration. The obtained relationships for η(space) are used in an empirical numerical model to predict the distribution of iron particles around an injection well at a realistic field injection. To this purpose, the flow domain is discretized in shells, each characterized by a value of seepage velocity and by a distinct volume of slurry that flows through a unit of its surface. The resulting model, which is based on a large number of experimental observations (about 50 packed-bed column tests), overcomes the limit of current approaches for predicting iron particle transport, as they consider mono-dimensional flow conditions, while during injection the flow field is radial. The proposed approach ought to help bridging the gap between laboratory scale research and the field scale application of micro-iron particle technology.