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Shallow Subsurface Detection of Buried, Weathered Hydrocarbons

Kirstie L. Haynie and Shuhab Khan
University of Houston, Department of Earth and Atmospheric Sciences

Weathered hydrocarbons, commonly emulsified or in the form of tar balls, wash ashore along beaches due to natural oil seepages or offshore oil spills. They remain buried in the sand until a hurricane or storm exposes them; therefore it is important to understand the progression and extent of these hydrocarbons. Elmer’s Island, Louisiana, a site known for having large amounts of oil washed ashore from the 2010 BP Deepwater Horizon oil spill, was selected for a geophysical survey to detect the presence of buried, weathered hydrocarbons. Ground penetrating radar surveys, using 200 MHz and 400 MHz antennae, were conducted at the site along several traverses. The 400 MHz data show two distinct anomalous zones with strong positive amplitudes. An electromagnetic profiler, operated along the same lines, displays rows of oval shaped anomalies in conductivity contour maps. The two anomalous zones observed in the ground penetrating radar data correspond with anomalies displayed on these maps. Field observations confirmed the existence of contaminated sand buried at the survey site in distinct layers. This contaminated sand enclosed small aggregates of weathered hydrocarbons, which may be associated to the oval shape of anomalies. To test whether these shallow subsurface features can be mapped by airborne remote sensing, NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar imagery will be processed to detect shallow subsurface features. These images and the data collected at the survey site will be correlated to map the extent of buried hydrocarbons along shorelines and to understand the movement of weathered hydrocarbons in these environments.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013