Defining Hydrostratigraphic Units and Estimating Their Permeability Using Cross-hole Ground Penetrating Radar
J. M. Markle
University of Western Ontario, Dept. of Earth Sciences, London, ON, Canada
Environmental investigations and reservoir simulation require detailed knowledge of the subsurface migration pathways determined by the presence of permeable layers. Knowledge of the location and 3-dimensional geometry of preferential flow paths is necessary to model and predict flow and transport in the subsurface. While these properties may be measured in sufficient detail vertically at well sites, adequate characterization of their lateral distribution is costly and time-consuming. Recent research has indicated that ground penetrating radar (GPR) imaging may provide a means of extracting estimates of the permeability of the subsurface materials. The purpose of our research is to assess how data from cross-hole GPR surveys may be used to obtain estimates of permeability.
Our test site is located in a glacial-fluvial outwash sand and gravel deposit that is underlain by glacial till. Subsurface flow is predominantly in the sand and gravel aquifer.We have installed a network of wells to facilitate geophysical and hydrologic testing. We collected undisturbed core samples during drilling. From these samples, we will log the stratigraphic units, determine the permeability of the porous media from constant-head tests and grain-size analyses, and measure dielectric values for the aquifer materials in the laboratory. With this information we will explore relationships between the dielectric values measured in the lab and in the field, and the permeability measured on the core samples. The development of relationships between the dielectric values and the permeability would allow direct estimates of the permeability of the porous media from GPR data.
AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid