COMPARISON OF EARLY AND LATE TRAVEL TIMES OF PRESSURE PULSES INDUCED BY MULTILEVEL SLUG TESTS
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abstract
2019, Taylor and Francis Ltd. All rights reserved. During a slug test, injection or withdrawal of a small volume of water through an open borehole in an aquifer induces a pressure pulse propagation process in the aquifer. Hydraulic data sets that are collected during this procedure can be manipulated by mathematical inversion to estimate the hydraulic properties near the borehole. In this paper, we report our finite element forward modeling of slug tests in an aquifer with stratigraphical heterogeneities. Our numerical studies, which resulted in contour plots of head perturbation and travel time, show that the early hydraulic travel time contour associated with partially penetrating slug tests in a heterogeneous aquifer could display a spatial distribution that is quite different from the late travel time contour. While the late travel time contour primarily reflects the integrated effect of widely propagated pressure distribution, the early travel times reflect the preferential flow and therefore can be exploited for hydrostratigraphical imaging of the aquifer. We argue that the early portion of hydraulic signals contains information that is complementary to the conventional peak travel time inversion and plays an indispensable role in gaining enhanced characterization of a geological units hydraulic properties. Furthermore, our modeling results demonstrate that early hydraulic travel times are not always associated with the shortest flow path.
