TR(BR)-139 : Flow towards a partially penetrating large diameter well

Abstract

Large diameter wells are economical and ideal for groundwater extraction in low transmissivity aquifers, such as fractured or fissured rocks. Storage within the well plays an important role when a large diameter well is pumped. A part of the pumped discharge is contributed by the well-storage which is substantial during initial phase of pumping. Well-storage contribution decreases with increase in time and after sufficiently long time, it becomes zero. Several studies pertaining to the analysis of flow towards a fully penetrating large diameter well, have been reported in the literature. A large diameter well may penetrate the aquifer partially because of construction and other constraints.

The present study deals with the analysis of flow to a partially penetrating large diameter well considering the flow through the bottom of the well. A simple methodology has been evolved for obtaining transient drawdown in the well as well as in the aquifer. The methodology enables the determination of aquifer contribution to the pumped discharge through the circumference as well as through the bottom of the well apart from the determination of well-storage contribution to the pumped discharge.