Transient Flow to a Horizontal Well under a Surface Water Body

A horizontal well is sometime installed in an aquifer beneath a surface water body to get better quality water because the lower permeable layer (aquitard) at the bottom of the water reservoir can act as a filter. The horizontal well can have great length of screens, thus can withdraw a significant amount of groundwater for water supply. In this study, we have investigated the transient flow to a horizontal well under a water reservoir. Previous studies in vertical wells related to this subject treated leakage from the surface water body as a volume source term in the governing equation, assuming the leakage distributed uniformly inside the aquifer. This is a necessary simplification to make the mathematical models solvable. In this study, flows in the aquitard and aquifer are treated as two systems which are linked through the continuity of flux and head at the aquitard-aquifer boundary. In particular, we treat leakage as a boundary at the aquitard-aquifer interface, not as a uniformly distributed volume source. The problem presented here concerns the induced three-dimensional interaction of stream and aquifer under a pumping horizontal well. The seepage rate induced by the pumping horizontal well and its dependence on the horizontal well length, well location, aquifer anisotropy, and hydraulic parameters of the aquitard at the bottom of the water reservoir is investigated. The results will be compared with those presented by Zhan and Park (2003). This paper will answer the questions such as under which circumstance the simplification of treating leakage as a volume source is valid. Keywords: transient flow, seepage rate, interaction, horizontal well Reference: Zhan, H. and Park, E., 2003. Horizontal well hydraulics in leaky aquifers. J. Hydrol. 281, 129-146