Simple Aquifer-free Models for Underdamped Slug Tests in High Permeability Aquifers

Abstract:

Slug tests are a rapid and cost effective aquifer testing method that provide insight into aquifer characteristics such as hydraulic conductivity. Accurate hydraulic conductivity values are essential for understanding the flow of water, and are a key component in understanding and modeling the effects of sea level rise on salt water intrusion in coastal aquifers. Large discrepancies exist among reported values of hydraulic conductivity based on different test methods for the Biscayne Aquifer, and attest to a need for reevaluation of test methods when applied to highly permeable systems. To determine the validity of slug tests that display underdamped oscillations in highly permeable aquifers, development of two models for cases with oscillating responses are considered and applied to actual well tests, and to an end-member (aquifer-free) laboratory case. Preliminary results of the models show that the proposed Poiseuille-equation-based models agree well with data from one real slug test and from an end-member laboratory test. However the Darcy-Weisbach-based model does not agree as well in both the well tests and end-member case, necessitating further examination of the parameters, the force balance equations that define the models, and the experimental design. The resulting models should demonstrate if the behavior of some slug tests in highly permeable material can be predicted by a damped spring mass model, and thus help to determine when the estimation of true hydraulic conductivity values in highly permeable aquifers is possible with slug tests.