TRANSIENT FLOW TO A HORIZONTAL WELL UNDER A WATER RESERVOIR

New semianalytical solutions for evaluation of the transient flow to a horizontal well under a water reservoir with finite length screen are investigated in this study. The lower permeable layer on the bottom of water reservoir can act as a filter. The water will be much clean after the effect of filtering. Previous studies treated leakage from aquitard or stream as a source term in governing equation of main aquifer, assuming the leakage distributes evenly inside the aquifer. In this study, flow in aquitard and aquifer is treated as two flow systems, and related these two flow systems together by the idea of continuity of flux and head on the boundary of aquitard and aquifer, and the leakage only occurs on the boundary. The results will be compared with those presented by Zhan and Park (2003) at different aquitard hydraulic characteristics and different well configurations systematically. This paper will answer the question under which circumstance the approximation of previous leakage treatment is valid. On the other hand, the problem presented here is the three dimensional pumping induced interaction of stream and aquifer under a horizontal well. The seepage rate induced by pumping horizontal well is fully discussed. Its dependence on the horizontal well length, well location, aquifer anisotropy and hydraulic parameters of lower permeable layer at the bottom of water reservoir is tested.

Reference: Zhan, H. and Park, E., 2003. Horizontal well hydraulics in leaky aquifers. J. Hydrol. 281, 129-146