In 1967 the Gulf Oil Company initiated a program for locating seeps in the marine environment. By 1974 a sophisticated system had been installed on Gulf's seismic vessel, the R/V Hollis Hedberg. This system, operated by Gulf from 1974 to 1983 was used to collect an extensive geochemical database in the Gulf of Mexico containing over 191, 000 dissolved gas analyses. An evaluation of this database, with respect to discoveries made after it was collected show the data is 88 % effective in finding new commercial production. This technology has the ability to predict whether a block has oil or gas potential.These active seepage anomalies define both the spatial extent and vertical variability of hydrocarbon plumes as they rise from the seafloor sediments. Spatial and temporal changes are quite distinctive when comparing natural versus anthropogenic seeps, which are almost exclusively related to leaking well casing and/or pipelines. This marine database illustrates the complexity of dissolved hydrocarbons associated with deep marine seepages from both natural and anthropogenic sources.This hydrocarbon seepage database provides the most extensive and complete coverage of the entire Gulf of Mexico shelf that has ever been collected. Dissolved gas measurements have been made at the surface (hull inlet) and at two depths (mid-tow, 450 feet) and (deep-tow, 600 feet), allowing both vertical and temporal measurements on regional and localized grids covering the Gulf of Mexico. Examples shown will demonstrate the spatial, vertical and temporal variability of natural and anthropogenic seepages. An understanding of this natural seepage complexity is essential when trying to compare and determine the potential source of new or continuing seepage which might be associated with an abandoned well, such as the Macondo well.

Spatial and temporal variability of hydrocarbon seepage, offshore Gulf of Mexico, regional and local variations as defined by natural seeps

245th National Meeting (2013)

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