Model assisted design of scavenger well system

•We develop a computationally inexpensive model of the scavenging well system.•We invoke the model to optimize the screen locations.•Production well screen is optimally located just below the water table.•Scavenger well screen is optimally located at the interface.•These locations minimize the scavenging requirement.

SummaryA scavenger well system is designed to skim/pump fresh water from a fresh-saline aquifer. It consists of a production and a scavenging well in close vicinity tapping the shallow fresh water and the deeper saline water zones respectively. These wells pump fresh and saline waters from the same site simultaneously without mixing, through two separate discharge systems. The rise of interface (upconing) due to pumping of fresh water well is countered by the pumping of saline water well. This leads to a reduction in the upconing of the interface. A general numerical model has been developed for simulation of saltwater transport induced by pumpage from a scavenger well system. The model has been validated against an analytical solution and a set of published field data. The numerical model is invoked to develop two Artificial Neural Network (ANN) models of the relevant state variables viz. production well salinity and drawdown at well face. These ANN models are used for optimizing the scavenging discharge with respect to the position of the two screens and subject to the constraint on production well salinity and the drawdown to ensure functionality of the production well screen.