Abstract
Summary The association of large-scale, visible (macro) seeps with oil and gas fields has been well known for many years. It is evident from the recent literature that developments in electronics and analytical techniques have been permitting more and more comprehensive geochemical analyses with a greater reliability and sensitivity. Low level, non-visible micro-seeps are now reliably detected and can be used to evaluate the hydrocarbon potential of a basin, to establish the association of hydrocarbons with individual structures, and to determine whether the reserves at depth are likely to be gas or oil prone. Weisman at Gulf Oil Company describes a system which measures C 1 –C 4 hydrocarbons with a sensitivity of 5 × 10 −11 1 propane at STP 1 −1 seawater. The newest generation of ‘Sniffer’ systems manufactured and operated by Interocean Systems Inc. measures C 1 –C 8 hydrocarbons with resolution of the saturated and unsaturated isomers as well as resolutions of the straight chain, branch chain and cyclic isomers with a sensitivity of 5 × 10 −13 1 −1 octane at STP 1 −1 seawater. These advances in hardware in hardware coupled with new data processing techniques have permitted the establishment of a significant body of field data and experience over the years. It is evident from the data presented that these newer geochemical techniques and experience from field data have created the ability not only to detect the very low concentration micro-seeps, but also to interpret the data in a useful way. This is resulting in geochemistry playing a more significant role in exploration than ever before.
Published Version
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