Natural gas seepage on the South Texas shelf Conference Paper uri icon

abstract

  • Copyright 1979. Offshore Technology Conference. An area of extensive gas seepage has been found on the South Texas shelf. The seep area extends for a distance of approximately 25 miles on a transect out from the coast at latitude 26 10'N. Water depths range between 65 and 130 meters. During nine samplings over a three year period, elevated near-bottom concentrations of methane (up to 500 nl/L), ethane (0.6 nl/L), and propane (0.5 nl/L) compared to nearby surface and other near-bottom waters were observed. Anomalous gaseous hydrocarbon levels were also observed in the interstitial waters at three stations sampled in the region. Ethane and propane concentrations were typically one order of magnitude higher in these sediments compared to typical South Texas shelf sediments. The C 1 /(C 2 +C 3 ) ratios in the sediments were as low as 14 indicating that the seepage may be of a petrogenic origin and not from shallow biogenic (microbial) sources. Significantly higher percentages of hydrocarbonoclastic bacteria were observed in the seep area. These may be a direct result of hydrocarbon seepage. No anomalous interstitial gas concentrations were observed in the 'Serendipity Gas Seep Area' of South Texas.

published proceedings

  • Proceedings of the Annual Offshore Technology Conference

author list (cited authors)

  • Brooks, J. M., Bernard, B. B., Sackett, W. M., & Schwarz, J. R.

complete list of authors

  • Brooks, JM||Bernard, BB||Sackett, WM||Schwarz, JR

publication date

  • January 1979