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Using Ground Penetrating Radar to Detect Oil in Ice and Snow

Using Ground Penetrating Radar to Detect Oil in Ice and Snow. E. Babcock 1 , J. Bradford 1 , H.P. Marshall 1 , C. Hall 2 , and D.F. Dickins 3 1 Department of Geosciences, Boise State University, Boise ID; 2 Alaska Clean Seas, Anchorage AK; 3 P.Eng., DF Dickins Associates Ltd., La Jolla CA.

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Using Ground Penetrating Radar to Detect Oil in Ice and Snow

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  1. Using Ground Penetrating Radar to Detect Oil in Ice and Snow E. Babcock1, J. Bradford1, H.P. Marshall1, C. Hall2, and D.F. Dickins3 1Department of Geosciences, Boise State University, Boise ID; 2Alaska Clean Seas, Anchorage AK; 3P.Eng., DF Dickins Associates Ltd., La Jolla CA

  2. Overview • Ground Penetrating Radar (GPR) theory • Considerations for detecting oil under ice and snow • Demonstrations in controlled environment spill response • Future work

  3. Brief History of GPR (Olhoeft, 2006) • 1926: Radar used to sound the depth of an alpine glacier in Austria (Stern, 1929) • 1958: USAF airplane crashed on Greenland ice sheet as radar energy passes through surface to layers below • 1960s: GPR used to sound moon during Apollo 17 • 1970s: Begin widespread use of GPR as a geotechnical tool • 1980s: GPR assessed as tool for oil detection under ice(Goodman et al., 1985 and 1987)

  4. Fundamentals of GPR • GPR uses electrical energy to interrogate the subsurface • Operates at radio frequencies • 10 MHz to 1 GHz • Transmit timed pulses of EM energy; measure reflected returns, process data, and display Annan, 2002.

  5. Material Electrical Properties in the Arctic Marine Environment

  6. INSERT PICS

  7. GPR for Oil Spill Response • Can we detect oil under ice and/or snow? • What processing do the data require? • What resolution can the system provide? • What limitations do we experience? • What benefits does this technology provide?

  8. System Considerations: Data Processing • Use standard basic processing steps • Time zero shift • Bandpass filter • Spherical spreading correction • Attribute analysis • Instantaneous phase and frequency • Reflection strength • Previous work with GPR noted potential using attribute analysis to detect oil that was not possible with conventional analysis

  9. System Considerations: Antenna Frequency • Frequency for radar survey is a trade-off • Depth of penetration • Quality of resolution • System portability • Field testing shows that GPR frequency of 500 MHz is optimal for penetration and resolution of oil under ice

  10. System Considerations: Resolution and Detection • Using 500 MHz antennas • Detect 1-2 cm oil layer in most scenarios • Resolve 4-5 cm oil layer • Thin bed analysis problem • Reflection analysis alone not enough to accurately locate oil • Previous work had indicated attribute analysis as possible solution (Goodman et al., 1985) • Consider attributes in conjunction with modeled response

  11. System Considerations: Non-Uniqueness From Bradford et al., 2008

  12. System Considerations:Anisotropy Data courtesy of Alaska Clean Seas

  13. Control Module (Digital Video Logger) - Sensors and Software PE Pro www.sensoft.ca

  14. Prudhoe Bay, April 2007 2008 Training on North Slope

  15. Pulse Ekko Pro GPR 500 and 1000 MHz antennas Multi-offset acquisition to determine effective permittivity of ice Pre- and post- oil emplacement 3D surveying over 20 x 20 m grid Large scale 2D profiling Norway, 2006

  16. GPR for Oil Spill Response: Svalbard From Bradford et al., 2008

  17. Controlled Spill, New Hampshire, 2004,2011-2013 • Cold Regions Research and Engineering Lab (CRREL), 2011 and 2012 • Indoor and outdoor testing • Known ice thickness • Known oil locations • 500 MHz PE Pro System

  18. GPR for Oil Spill Response: CRREL From Bradford et al., 2010 From Bradford et al., 2008

  19. GPR for Oil Spill Response: CRREL 2012

  20. GPR Limitations in the Arctic Environment • Variations in sea-ice conductivity and anisotropy • Snow may generate spurious amplitude anomalies due to water or ice in snowpack: solution is non-unique • We can ameliorate these concerns by frequent data truing and cautious interpretation

  21. Conclusions: What Can GPR Do For Us in Arctic Spill Response? …and future research

  22. Acknowledgements • My advisors John Bradford and HP Marshall • CRREL and all the hardworking staff there – thanks! • Alaska Clean Seas • DF Dickins Associates Ltd • Current funding provided by • Alaska Clean Seas • Conoco Phillips • ExxonMobil • Shell Oil • Statoil

  23. References Annan, A.P. 2005. Ground-Penetrating Radar. In Near Surface Geophysics, Investigations in Geophysics No. 13. Butler, D.K., Ed. Society of Exploration Geophysicists, Tulsa, OK. Annan, A.P. 2002. GPR – History, Trends, and Future Developments. Subsurface Sensing Technologies and Applications, 3(4): 253-271. Bradford, J.H. and J.C. Deeds. 2006. Ground penetrating radar theory and application of thin-bed offset- dependent reflectivity. Geophysics, 71(3): K47-K57. Bradford, J.H., D.F. Dickins, and P.J. Brandvik. 2010. Detection of snow covered oil spills on sea ice using ground-penetrating radar: Geophysics, 75, G1-G12, doi:10.1190/1.3312184. Bradford, J. H., D. F. Dickins, and L. Liberty. 2008. Locating oil spills under sea ice using ground-penetrating radar: The Leading Edge, 27,1424–1435. Martinez, A. and A.P. Byrnes. 2001. Modeling Dielectric-constant values of Geologic Materials: An Aid to Ground-Penetrating Radar Data Collection and Interpretation. Current Research in Earth Sciences, Bulletin 247. Online at http://www.kgs.ukans.edu/Current/2001/martinez/martinez1.hmtl Olhoeft, G.R. 2006. Applications and Frustrations in Using Ground Penetrating Radar. IEEE AESS Systems Magazine, 2: 12-20. Questions?

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