Diagnostic plot analysis of a porous fractured aquifer

Diagnostic plot method (derivative analysis) displays the logarithmic derivate of drawdown data against time for hydraulic tests and is considered a robust tool for evaluating aquifer properties and developing suitable conceptual hydrogeological models. At the test site Neutra (located near the Nord Campus of University Goettingen, Germany), series of multi-level cross-well pumping tests were conducted in five wells. Both pumping and observation wells were equipped with inflatable double packers to isolate specific well sections hydraulically. This design allowed the research work on spatial variation of hydraulic parameters in the subsurface. The diagnostic plot derived from these pumping tests were analyzed and utilized not only for the identification of flow regimes and boundary conditions, but also for conceptualization and optimization of numerical modelling of aquifer system. Additionally, a significant skin and wellbore storage effect was detected at early time of the plots. Based on obtained results, conceptual models were developed, and the same pumping tests in the field were simulated to evaluate the aquifer properties. The advantages and limitations of diagnostic plot analysis were discussed based on the comparison of results from in-situ tests and numerical modelling.