title: A model to simulate pumping tests in wells with high loss and backflow.
abstract: Traditional methods of analyzing pumping tests in single wells fail when the well loss is very high due to a low transmissivity skin. Because of the restricted rate at which water can enter a high loss well from the aquifer, well casing storage becomes a significant factor. Additionally, if a slug of water enters the well from the pump column immediately after the pump is switched off, it has a long-lasting significant effect on the recovering water level in the well because it cannot be absorbed rapidly by the aquifer. A theoretical model is derived here that simulates the water level in a well in these circumstances. In the model, the continuously changing rate of water inflow from the aquifer to the well is approximated by a step function with a finite difference time step. It is demonstrated by a real example that the model can be applied easily to analyze pumping tests, including tests with a varying pumping rate. The analysis confirms suspected high well loss, calculates the unknown rate of backflow, and determines the aquifer's transmissivity.
authors.affiliation: Groundwater Division, Saudi Aramco, Dhahran 31311, Saudi Arabia. kaweckmw@aramco.com
authors.forename: M Wojciech
authors.initials: MW
authors.lastname: Kawecki
mesh_terms: D003198:Computer Simulation; D005618:Fresh Water; D008962:Models, Theoretical; D014881:Water Supply