HR: 0800h
AN: NS31A-08    [Abstracts]
TI: Dielectric and GPR Characterization of Shallow Carbonate Reservoir Analogs in Central Texas
AU: * Banerjee, D
EM: dmukherjee2@uh.edu
AF: University of Houston, Department of Geosciences, 312 Science & Research Building -1, Houston, TX 77204-5007, United States
AU: Heggy, E
EM: heggy@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058-1113, United States
AU: Khan, S D
EM: sdkhan@uh.edu
AF: University of Houston, Department of Geosciences, 312 Science & Research Building -1, Houston, TX 77204-5007, United States
AU: Sullivan, C E
EM: charlotte.sullivan@pnl.gov
AF: Pacific Northwest National Laboratories, 902 Battelle Boulevard, Richland, WA 99352-999, United States
AB: Albian rudist communities of the Edwards Formation, Fredericksburg Group, occur widely in Central and South- Central Texas. Capped by younger dolostones of the same group, they form important analogs for highly productive hydrated and hydrocarbon-rich reservoirs in arid environments. This study is a part of a larger project covering exposures of Albian rudists and associated depositional facies around Georgetown (Williamson County) in Central Texas. Dielectric measurements of field-collected rock samples of varying clay content were carried out initially under vacuum dried conditions and then under controlled amounts of moisture contents from 1 to 100% of the rock porosity (assuming even and complete saturation of porosity). Plots of the real parts of dielectric constants indicate that the more clay-rich samples exhibit a much greater variation with changing moisture content. Plots of the imaginary parts of the dielectric constants of the samples show a similar trend with a more significant dependency at low moisture content (< 20%), i.e., changes in dielectric losses are more conspicuous with an increase in clay content. These plots indicate that different carbonate units can be differentiated in the field by a Ground Penetrating Radar (GPR) as a result of their different dielectric contrasts arising from a variation of moisture and clay contents. The penetration depths are also calculated for each sample at varying antenna frequencies assuming GPR signal penetration in a homogeneous layer. As expected, this reveals an inverse relation between the clay content and the depth of penetration. Our analyses involve the use of a 400 MHz antenna with the Subsurface Interface Radar (SIR-3000) System by GSSI and GPS data to obtain better knowledge of the architecture and spatial distribution of the rudist mounds in the subsurface. This effort will eventually provide a 3D characterization of the shallow reservoir geometry and its dielectric heterogeneity, useful not only in hydrocarbon exploration but also in hydrological applications in carbonate terrains. Acknowledgement: This research was supported by a GCAGS Student Research Grant to D. Banerjee.
DE: 0619 Electromagnetic theory
DE: 0694 Instruments and techniques
DE: 1835 Hydrogeophysics
DE: 5109 Magnetic and electrical properties (0925)
DE: 5144 Wave attenuation
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly