Origin of natural gases of the Polish carpathians: Isotopic and geological approach
- Univ. of Mining and Metallurgy, Cracow (Poland)
- Polish Oil and Gas Company, Warsaw (Poland)
The Carpathian petroleum province includes the two main structural units: the Carpathian Overthrust and the Carpathian Foredeep. The Carpathian Foredeep consists of two structural complexes: Paleozoic-Mesozoic basement and a late Alpine Miocene cover. Stable isotope ratios and C{sub 2+} wet gas index (C{sub 2+}=(C{sub 2}+C{sub 3}+C{sub 4}+C{sub 5})/(C{sub 1}+C{sub 2}+C{sub 3}+C{sub 4}+C{sub 5})100[%]) for gases from the Flysch Carpathian reservoirs vary in the following ranges: {delta}{sup 13}C (CH{sub 4}) from -65.8 to -34.2 %, {delta}D (CH{sub 4}) from -207 to -151%, {delta}{sup 13}C (C{sub 2}H{sub 6}) from -47.2 to -24.0%, {delta}{sup 13}C (C{sub 3}H{sub 8}) from -31.6 to -22.6% and C{sub 2+} from 0.72 to 33.9. Natural gases, both dissolved with the oils and free accumulated independently in the Carpathian Overrhrust flysch reservoirs, were generated mainly during the low-temperature thermogenic processes (within {open_quotes}oil window{close_quotes}) and high-temperature ones as well as sporadically during bacterial processes. Stable isotope ratios and the C, wet index for gases from Paleozoic-Mesozoic deposits vary in the following ranges: {delta}{sup 13}C (C{sub 3}H{sub 8}) from -57.0 to -31.7%, {delta}D (CH{sub 4}) from -182 to -134%, {delta}{sup 13}C (C{sub 2}H{sub 6}) from -34.1 to -22.5%, {delta}{sup 13}C (C{sub 3}H{sub 8}) from -33.9 to -23.2%, and C{sub 2+} from 2.2 to 13.4. Such extended ranges of values suggest complex origins of bacterial and thermogenic gases involving migration and mixing. The thermogenic generation of hydrocarbons was a multiphase process and traps in all deposits were supplied at various times during the successive hydrocarbon generation phases. Accumulation of bacterial gases within the Miocene strata was facilitated by high sedimentation rate, rhythmic and cyclic deposition of alternating clays and sands, and presence of methane hydrate formed in the thermodynamic regime of the Miocene basin.
- OSTI ID:
- 127621
- Report Number(s):
- CONF-950995-; ISSN 0149-1423; TRN: 95:005942-0175
- Journal Information:
- AAPG Bulletin, Vol. 79, Issue 8; Conference: International conference and exhibition of the American Association of Petroleum Geologists, Inc.: managing change at the turn of the century, Nice (France), 10-13 Sep 1995; Other Information: PBD: Aug 1995
- Country of Publication:
- United States
- Language:
- English
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