Gas seepage from a carbonate-cemented sandstone reef on the Kattegat coast of Denmark

• Published in: Marine and petroleum geology 1994-04, Vol.11 (2), p.182-189
• Main Authors: Dando, Paul R., O'Hara, Sean C.M., Schuster, Ute, Taylor, Lesley J., Clayton, Chris J., Baylis, Sarah, Laier, Troels
• Format: Article
• Language: English
• Subjects: carbon isotopes; Earth sciences; Earth, ocean, space; Exact sciences and technology; gas seepage rates; Hydrocarbons; Marine; methane; Sedimentary rocks
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/0264-8172(94)90094-9

Gas seepage rates were measured over a two year period at an intertidal/shallow subtidal methane-derived carbonate-cemented sandstone reef off north-east Denmark. The positions of some of the gas outlets at the intertidal site changed with time but the overall gas flux of the reef area remained approximately constant, with a mean flow-rate of 59.4 ml h −1 m −2 or over 100 l h −1 for the seepage area. In the shallows the flow-rates of seeps varied with the depth of the overlying water. The methane from the seeps had a radiocarbon age of > 39 000 years bp and was depleted in heavy isotopes, δ 13C CH 4 varied from −68.6 to −75.3‰ and δD from −240 to −249‰, suggesting a bacterial origin. The most 13C-depleted methane came from the most active of the seeps tested.