Hydraulics of horizontal wells in fractured shallow aquifer systems Eungyu Park a, * , Hongbin Zhan b a Department of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5028, Delft 2600GA, The Netherlands b Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, USA Accepted 1 May 2003 Abstract An analysis of groundwater hydraulic head in the vicinity of a horizontal well in fractured or porous aquifers considering confined, leaky confined, and water-table aquifer boundary conditions is presented. Solutions for hydraulic heads in both leaky confined and water table aquifers are provided. The fracture model used in this study is the standard double-porosity model. The aquitard storage is included in the formula. Solutions for the confined and unconfined conditions, fractured and porous conditions, wellbore storage, and skin effect are compared. Several findings of this study are, (1) the influence of wellbore storage and skin upon the drawdown for a fractured confined aquifer is similar to that for a porous confined aquifer, (2) aquitard storage affects the intermediate time the most by delaying the drawdown, and (3) there is a significant difference between the type curves of fractured and porous confined aquifers in most aquifer boundary conditions because of the contribution of matrix storage, and such a difference disappears at the later time. q 2003 Elsevier B.V. All rights reserved. Keywords: Horizontal well; Wellbore storage; Skin effect; Water table; Leaky confined aquifer; Fractured aquifer 1. Introduction Horizontal well applications are one of the promising techniques in environmental remediation, water management, oil recovery, etc. In most of these applications, keeping the wellbore in contact with the targeting subsurface zone is essential. Horizontal wells offer many advantages over vertical wells because of their larger contact with the targeting aquifers. There have been several studies about the hydraulics of horizontal wells in shallow ground water aquifers (Hantush and Papadopulos, 1962; Cleveland, 1994; Sawyer and Lieuallen-Dulam, 1998; Zhan et al., 2001) and in unsaturated zones (Falta, 1995; Zhan and Park, 2002). In most of these studies, the horizontal well is treated as a line sink/source and the wellbore storage and skin effects are not included. Zhan and Zlotnik (2002) derived solutions for drawdowns in water table aquifers due to pumping from horizontal and inclined wells. Their solutions may be inaccurate at early time and near the well because they neglect wellbore storage and skin effects. Recently, Park and Zhan (2002) derived a solution for hydraulic head in the vicinity of horizontal wells in confined and leaky confined 0022-1694/03/$ - see front matter q 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0022-1694(03)00206-3 Journal of Hydrology 281 (2003) 147–158 www.elsevier.com/locate/jhydrol * Corresponding author. Present address: Environmental Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. E-mail addresses: parke@ornl.gov (E. Park), zhan@hydrog. tamu.edu (H. Zhan).