ANALYTICAL SOLUTION OF CAPTURE ZONE OF A HORIZONTAL WELL IN A CONFINED AQUIFER

Horizontal wells are regarded as effective means of removing contaminated groundwater from aquifers. However, delineation of capture zone of a horizontal well has not been carefully studied in a systematic way. In this paper, we have presented analytical solutions for the capture zones of horizontal wells in a homogeneous, confined aquifer with uniform flow, considering three possible well locations at the middle, the boundary, and an arbitrary position. We find that the capture width enlarges and the bisector line of the capture zone moves toward the centerline of the aquifer when moving away from the well in the upstream direction for an arbitrary well location. The capture width and bisector line approach their ultimate width and position, respectively after an ultimate distance of about 1.5 times of the aquifer thickness. The ultimate capture width depends on the well discharge but not on the well location. We have provided type curves of the ultimate bisector line position versus discharge for different well locations. Compared to the vertical well capture zone, the ultimate capture width of a horizontal well is smaller than that of a vertical well given the same discharge rate per unit length because of the constraining effect of the upper and lower aquifer boundaries. Furthermore, the relationship between the ultimate capture width and the well discharge rate is nonlinear due to the influence from the aquifer boundaries, in contrast to the linear behavior often observed in the vertical well capture zone.