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Origin and migration of oil from the Ukrainian Outer Carpathians to their Mesozoic basement: a case of Lopushna traps

Radkovets N. Y., Kotarba M., Koltun Y., Kowalski A., Kosakowski P., Więclaw D.

Geological Quarterly

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2016

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Vol. 60, No. 1

133--148

EN

Lopushna oil field has been discovered in Mesozoic-Paleogene strata of the platform basement under the Ukrainian Outer (Flysch) Carpathians. Oils from two main accumulations, occurring in the Upper Cretaceous sandstone and Upper Jurassic limestone reservoirs, have been analysed in order to identify their origin and relation to the known petroleum systems in the region of the Outer Carpathians and the basement of the Carpathian Foredeep. Results of geochemical investigations of oils, including biomarker and isotopic data, show a good correlation with oils, accumulated in the Carpathian flysch strata. Oils are low-sulphur and did not undergo significant degradation. They were generated from Type II or II/III kerogen, deposited in anoxic environments in clastic sediments. Generation occurred at the peak of “oil window”, probably in the temperature range of 122 to 126oC. The presence of oleanane indicates the Cretaceous or younger source rocks. Good correlation on biomarker and isotopic data with the organic matter dispersed in Oligocene Menilite Beds, occurring at the top of the Carpathian flysch succession, allowed authors to identify them as source rocks for oils of the Lopushna field, which thus can be regarded as an oil family of the Outer Carpathians. The migration distance for both Lopushna oils and oils accumulated in the Carpathian flysch strata was similar. A number of sub-vertical dislocations, on which the subsided flysch strata occur at the same depth level with the Jurassic and Cretaceous rocks of the platform, can be assumed as possible migration pathways from the mature source rocks of the Oligocene Menilite Beds of Boryslav-Pokuttya, Skyba or Krosno units to the Lopushna type traps, which suggests the possibility of existence of other hydrocarbon accumulations of this type. The Lopushna field so far is unique containing this type of oil found in the basement of the Ukrainian Carpathian Foredeep.

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Origin of liquid hydrocarbons accumulated in the Miocene strata of the Polish Carpathian Foredeep and its Palaeozoic–Mesozoic basement

Więcław D.

Annales Societatis Geologorum Poloniae

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2011

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Vol. 81, No 3

443-458

EN

Petroleum geochemical data of 34 oils and condensates accumulated in the Carpathian Foredeep and its Mesozoic and Palaeozoic basement were used to assess their origin and genetic type. The analysed liquid hydrocarbons are characterized by variable densities and sulphur contents. No relationship between these parameters and the reservoir rock age has been found. Secondary processes of evaporative fractionation and biodegradation are evidenced for some oils. These processes proceeded most intensively on the oil from Góra Ropczycka-1K well. The oils from Opaka-1, Lubaczów-157 and Góra Ropczycka-1K wells were generated from organic matter deposited in the Upper Jurassic carbonates. The oil from the inflow in Załazie-2 well originated from the Cambrian strata, but also contains biomarkers characteristic of Miocene strata. The next family, genetically connected with the Silurian and Ordovician source rocks, consists of oils accumulated in the Lower Carboniferous carbonates in Nosówka deposit and in the Upper Jurassic in the inflow into Łękawica-1 well. The condensates collected from the Miocene (Łękawica-1, Pilzno-37, Tarnów-39 and -45 wells) and Upper Jurassic strata (Łąkta-27 and Tarnów-5 wells) were generated by organic matter dispersed in the Middle Jurassic or Lower Carboniferous clastic facies. The remaining oils, from Grobla-Pławowice, Wierzchosławice, Jastrząbka Stara, Partynia-Podborze, Dąbrowa Tarnowska, Brzezówka and Zagorzyce deposits, and the inflows into Tarnów-47 and Pilzno-12 wells were generated from kerogen enriched in organic sulphur usually dispersed in carbonate rocks. Such a type of sediments occurs in the Devonian and Lower Carboniferous strata. Also, these strata as well as the underlying Silurian rocks have sufficient maturity for generation of the discussed oils. The oleanane in the discussed oils most probably originates from kerogen of the Upper Cretaceous or Miocene strata, through which these oils migrated and eluted this biomarker.

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Origin of oils accumulated in the Middle Cambrian reservoirs of the Polish part of the Baltic region

Kowalski A., Więcław D., Kotarba M. J.

Geological Quarterly

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2010

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Vol. 54, No 2

205-216

EN

We have examined 21 samples of crude oils accumulated in the Middle Cambrian sandstone reservoirs from the Polish part of the Baltic region. All the crude oils have similar parameters and indices, which suggests generation from the same source rock. Evaporative fractionation and biodegradation processes were detected in oil collected from the B4-N1/01 borehole. All crude oils have high gravities and low-sulphur contents, less than 0.3 wt.%, which suggests that their source rock contained low-sulphur kerogen deposited in a clastic environment. A low asphaltenes content (below 0.3 wt.%) and high saturate/aromatic hydrocarbon ratios indicate long migration distances or high thermal maturities. The longest migration distance was probably attained by oils from the arnowiec and B16 deposits. The biomarker data indicate an algal origin for the source organic matter deposited under conditions of clastic sedimentation. The stable carbon isotope data support this observation. The maturity of the oils analysed varies from ca. 0.75 to ca. 1.05% on the vitrinite reflectance scale. Unlike the B6, B16, Dbki and arnowiec accumulations, oils from the B3 and B4 accumulations reveal the lowest maturity.

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Biological markers and stable carbon isotope studies of bitumen impregnating Quaternary sediments at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)

Kotarba M. J., Fabiańska M., Więcław D., Kowalski A., Zych H.

Annales Societatis Geologorum Poloniae

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2009

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Vol. 79, No 3

463-480

EN

Biological markers and stable carbon isotopic compositions of bitumen impregnating the Pleistocene and Holocene sediments around the Starunia palaeontological site (Carpathian region, Ukraine) near discovered remnants of a mammoth and three woolly rhinoceroses, and one almost completely preserved rhinoceros carcass found in 1907 and 1929, were investigated. The research was carried out to assess genetic connections between the bitumen and oils from the nearby deep accumulations of the Boryslav-Pokuttya and Skyba units of the Carpathians. Another aim of these geochemical studies was to reveal the secondary geochemical processes (oxidation and biodegradation) influencing the bitumen, and to determine which environments have been favourable or unfavourable for the preservation of large Pleistocene vertebrates. Bitumen included within the near-surface rocks are not genetically connected with residual organic matter present in Quaternary sediments. Geochemical features, such as distributions of pentacyclic triterpanes and steranes, biomarker parameters and isotope composition indicate that all bitumens originate from oil-prone, Type II kerogen with insignificant admixture of terrestrial Type III kerogen in the middle stage of catagenesis. The oils occurring in deep accumulations in the Starunia area were the sole source of bitumen found in the near-surface sediments. Input of immature organic matter to bitumen from Pleistocene and Holocene sediments has not been found. The main factors differentiating the bitumen were: biodegradation, water washing and/or weathering. Additional influence of transport of bitumen by brine was found. The most favourable conditions for preservation of large, extinct mammals within the Pleistocene muds exist in the vicinity of Nos 22 and 23 boreholes, where bitumen is best preserved. The worst conditions were found in the vicinity of Nos 1, 4, 4' and 15 boreholes. Intensification of biodegradation and weathering effects were followed by intensive, chaotic changes of the remnants of large Pleistocene mammals.

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Skład, geneza i środowisko generowania ropy naftowej w utworach dolomitu głównego zachodniej części obszaru przedsudeckiego

Kotarba M.J., Więcław D., Kowalski A.

Przegląd Geologiczny

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2000

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Vol. 48, nr 5

436-442

PL

Przedstawiono geochemiczną charakterystykę genetyczną 33 rop naftowych ze złóż i nieprzemysłowych przypływów znajdujących się w utworach dolomitu głównego zachodniej części obszaru przedsudeckiego. Wszystkie badane ropy naftowe dolomitu głównego zostały wytworzone z ropotwórczego kerogenu typu II, który znajduje się w środkowej lub końcowej fazie niskotemperaturowych procesów termogenicznych. Utwory dolomitu głównego spełniają więc rolę zarówno skaty macierzystej jak i zbiornikowej. W północnej części badanego obszaru stopień przeobrażenia rop rośnie z zachodu na wschód i jest bardzo zróżnicowany pomimo, że akumulacje występują na podobnej głębokości, co może świadczyć o wielofazowości procesów generowania lub/i migracji węglowodorów. Natomiast w strefie południowej stopień przeobrażenia rop jest zróżnicowany w zależności od głębokości akumulacji, co może świadczyć o rozrzuconej przestrzennie " kuchni generowania " w której z tej samej substancji organicznej wytwarzały się węglowodory w zależności od głębokości pogrążenia, a tym samym o bliskim położeniu skal macierzystych od miejsc akumulacji oraz o niewielkim zasięgu migracji.

EN

Geochemical characteristics of origin of 33 oils in carbonate reservoirs occurring in the Zechstein Main Dolomite strata of the western part of the Fore-Sudetic area have been presented in the paper. All the oils were generated from type II kerogen in the middle and final phase of low-temperature thermogenic processes ("oil window"). The Main Dolomite strata play the role of both a source rock and reservoir. In the northern part of the studied area maturity of oils increases from the west to the east. It strongly varies although the accumulations occur on at similar depth. This may be the evidence of a multiphase character of the processes of hydrocarbon generation and/or migration. The maturity, however, varies in the southern zone, depending on the depth of accumulation. This may evidence the existence of a spatially scattered generation centres where hydrocarbons were generated from the same organic matter, depending on the depth of deposition, and so the closeness of source rock to the place of accumulation and small range of migration.