Use of the hydrogen and carbon stable isotopes in the characterization of oils from the Potiguar Basin (onshore), Northeastern Brazil
- Indiana Univ., Bloomington, IN (United States)
- Petrobras Research and Development Center, Rio de Janeiro (Brazil)
Hydrogen and carbon isotopic compositions of marine-evaporitic, lacustrine, and mixed oils were measured in selected samples from the onshore Potiguar Basin, Brazil. The isotopic data, together with GC and GC/MS results and geological information, were used to investigate the relationship between [delta]D and [delta][sup 13]C in the assessment of source rock facies, thermal maturity, biodegradation, and distance of secondary migration. The marine-evaporitic oils are depleted in D (-l 17[per thousand] to -136[per thousand]), and enriched in [sup 13]C (-25.6[per thousand] to - 26.4[per thousand]), whereas the lacustrine oils are enriched in D (-88[per thousand] to -101[per thousand]) and depleted in [sup 13]C (-30.1[per thousand] to -33.6[per thousand]). Values of [delta]D for mixed oils are intermediate between those of marine- evaporitic and lacustrine oils. The results suggest that [delta]D is a reliable tool for identification of oils that differ genetically, and the hydrogen isotopic compositions of the oils can be related to the [delta]D of the water in the paleoenvironments where the organic matter was produced. Therefore, [delta]D can be a useful tool to estimate, at least roughly, the paleo-[delta]D of the waters of the depositional environments and indirectly may give clues about paleo-climatic conditions. There was no detectable influence ofthermal maturation, biodegradation, or distance of secondary migration on the 8D of the oils. Marine-evaporitic and lacustrine oils can easily be distinguished using [delta][sup 13]C, but resolution of marine-evaporitic and mixed oils is not always possible. This indicates that [delta][sup 13]C can be a good tool for geochemical correlation, but is not diagnostic per se regarding the origins of all different types of oils. However, coupling of [delta][sup 13]C and [delta]D provides more powerful results.
- OSTI ID:
- 6859073
- Report Number(s):
- CONF-960527-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin, Vol. 5; Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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