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标题：Surface geochemical data evaluation and integration with geophysical observations for hydrocarbon prospecting, Tapti graben, Deccan Syneclise, India
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作者：T. Satish Kumar ; A.M. Dayal ; V. Sudarshan 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2014
卷号：5
期号：3
页码：419-428
DOI：10.1016/j.gsf.2013.08.003
语种：English
出版社：Elsevier
摘要：AbstractThe Deccan Syneclise is considered to have significant hydrocarbon potential. However, significant hydrocarbon discoveries, particularly for Mesozoic sequences, have not been established through conventional exploration due to the thick basalt cover over Mesozoic sedimentary rocks. In this study, near-surface geochemical data are used to understand the petroleum system and also investigate type of source for hydrocarbons generation of the study area. Soil samples were collected from favorable areas identified by integrated geophysical studies. The compositional and isotopic signatures of adsorbed gaseous hydrocarbons (methane through butane) were used as surface indicators of petroleum micro-seepages. An analysis of 75 near-surface soil-gas samples was carried out for light hydrocarbons (C1–C4) and their carbon isotopes from the western part of Tapti graben, Deccan Syneclise, India. The geochemical results reveal sites or clusters of sites containing anomalously high concentrations of light hydrocarbon gases. High concentrations of adsorbed thermogenic methane (C1 = 518 ppb) and ethane plus higher hydrocarbons (ΣC2+ = 977 ppb) were observed. Statistical analysis shows that samples from 13% of the samples contain anomalously high concentrations of light hydrocarbons in the soil-gas constituents. This seepage suggests largest magnitude of soil gas anomalies might be generated/source from Mesozoic sedimentary rocks, beneath Deccan Traps. The carbon isotopic composition of methane, ethane and propane ranges are from −22.5‰ to −30.2‰ PDB, −18.0‰ to 27.1‰ PDB and 16.9‰–32.1‰ PDB respectively, which are in thermogenic source. Surface soil sample represents the intersection of a migration conduit from the deep subsurface to the surface connected to sub-trappean Mesozoic sedimentary rocks. Prominent hydrocarbon concentrations were associated with dykes, lineaments and presented on thinner basaltic cover in the study area, which probably acts as channel for the micro-seepage of hydrocarbons.Graphical AbstractDisplay OmittedHighlights•The study reveals that, the Mesozoic sediments are source of hydrocarbons.•Gases are derived from oxidation of thermogenic gas of the gas reservoir.•Dykes and lineaments act as channels for micro-seepage from source to thinner basaltic cover.
关键词：KeywordsenAdsorbed gasMicroseepageLight hydrocarbonStable isotopeGeophysicalDeccan Syneclise