Groundwater flow near vertical recirculatory wells: effect of skin on flowgeometry and travel times with implications for aquifer remediation

Abstract

Flow structure around a recirculation well in a uniform anisotropic aquifer is investigated using potential theory and Stokes’ stream function techniques. A vertical recirculation well consists of two screened sections (chambers) separated by an impermeable casing: one section extracts water from the aquifer and the other section injects the water back into the aquifer. Analytical formulae are derived for the drawdown and the stream function for a model in which the extraction and injection chambers of the well are modeled as uniformly distributed cylindrical sinks and sources, respectively. Travel times are analyzed for water particles traveling from the injection chamber to the extraction chamber along streamlines containing various percentages of the flow. We consider a disturbed zone (skin) having properties which are different from those in the uniform anisotropic aquifer owing to disturbance of the area near the well during installation. The effects of this skin on the streamlines and travel times are analyzed for various lengths separating the chambers and for various skin conductivities. The method completely eliminates the use of numerical finite-difference or finite-element methods and can be used for optimization of technological parameters in a remediation system.