4D GPR Fluid Flow Visualization in Fractured Carbonates at the 1 to 10m Scale
Mark Grasmueck¹, Pierpaolo Marchesini¹, Gregor P. Eberli¹, Michael Zeller¹, and Remke L. Van Dam²
¹Center for Carbonate Research, University of Miami (FL) USA
²Dept of Geological Sciences, Michigan State University, East Lansing (MI) USA
Three thousand liters of water were infiltrated from a 4 m diameter pond to track flow and transport inside fractured carbonates with 20-40 % porosity. Sixteen time-lapse 3D Ground Penetrating Radar (GPR) surveys with repetition intervals between 2 hrs and 5 days monitored the spreading of the water bulb in the subsurface. Based on local travel time shifts between repeated GPR survey pairs, localized changes of volumetric water content can be related to the processes of wetting, saturation and drainage. Deformation bands consisting of thin subvertical sheets of crushed grains reduce the magnitude of water content changes but enhance flow in sheet parallel direction. This causes an earlier break through across a stratigraphic boundary compared to porous limestone without deformation bands. This experiment shows how 4D GPR can non-invasively track ongoing flow processes in rock-volumes of over 100 m³.
AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012