Summary

Natural attenuation of the crude oil released during a catastrophic blowout of a production well has been monitored over the course of 22 months. Changes in the oil signature and PAH concentration and distribution have been determined for over 350 soils from 46 sample stations at different locations surrounding the well. Quantitative determinations of the reduction in the concentration of PAH compounds was monitored through relative comparison to an conservative internal marker, 17a(H),21b(H) hopane. Significant (80-90%) reductions in PAH content were observed only 10 months following the blowout at most locations other than those immediately proximal to the blowout well, where oil impact was greatest. Subsequent, monitoring revealed a return to background conditions at most locations within 18 months following the blowout. Under these conditions natural attenuation has resulted in removal of most hydrocarbons including the PAH.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah