WHELAN, JEAN K.¹, NATHAN MAH¹, GREG EISCHEID¹, HARRY ROBERTS², PAUL AHARON², ROBERT CHEN³, AND XUCHEN WANG^3
1Department of Geochemistry, Woods Hole Oceanographic Institution, Woods Hole MA 02543
²Center for Coastal Studies & Department of Geology & Geophysics, Louisiana State University, Baton Rouge, LA 70803
³Department of Environmental Sciences, University of Massachusetts, Boston, MA 02125

Abstract: Gas and Oil Seepage and Hydrothermal Venting in the Ocean Bottom -Detection by Fluorescence

An abundance of evidence suggests continuous or episodic upward movement of fluids from deeper sediments into surface sediments and ocean bottom waters. These seepages may have been volumetrically underestimated in the past, both in oil and gas productive areas and in tectonic regimes (e.g. hydrothermal vent areas) because they often occur through small seemingly unimportant localized cracks in the seafloor. However, even if these venting features are small, the volume of expelled fluid can be important: even a small fracture can deliver orders of magnitude more fluid than ordinary compaction and diffusion processes. Here we present initial results on successful deployment of a continuous bottom water fluorescence detector for detection of bottom venting fluids both in a known oil and gas seep area (Green Canyon in the offshore Louisiana Gulf of Mexico) and in a hydrothermal vent area (Guaymas Basin, Gulf of California). Our initial results confirm the very localized and possibly episodic nature of these venting features which would not have been detected without a continuous localized detection technique.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas