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Major hydrocarbon accumulations are located in western Ukraine within the Mesozoic‐Cenozoic flysch sequence in the frontal parts of the External Carpathians, and in the adjacent autochthonous foreland. The accumulations occur in three different structural settings: in the Carpathian flysch belt; in the pre‐Neogene foreland autochthon; and in Miocene foredeep molasse. The petroleum potential of organic‐rich rocks belonging to a number of different sedimentary cycles and tectonic units was studied by Rock‐Eval pyrolysis. Two significant organic‐rich units, both with a basin‐scale distribution, occur within the External Carpathians: (i) a unit comprising the Lower Cretaceous Shypot and Spas Formations; and (ii) the Oligocene‐Lower Miocene Menilite Formation. The Menilite Formation includes the principal source rocks in this area, although Lower Cretaceous source rocks may also have generated hydrocarbons. Thermal maturation of the flysch and consequent petroleum generation resulted mainly from tectonic burial during Miocene overthrusting. In the external parts of the Carpathian Flysch Belt, oil generation in the Menilite Formation begins at a depth of around 4.2 km and ceases at around 6 km. In more internal tectonic units, a “frozen oil kitchen” occurs at shallower depths, indicating an increasing amount of tectonic uplift and erosion. The autochthonous foreland is part of the SW margin of the East European Platform, and is partially overthrust by the Carpathian orogen. Rocks belonging to several different sedimentary cycles are present here. Pre‐Mesozoic rocks in the foreland are overmature, at least within the central and SE parts of the study area. Petroleum accumulations are therefore most probably confined to the Mesozoic‐Cenozoic sedimentary cover, within which the Middle Jurassic Kokhanivka Formation has the highest generation potential.

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The Lower Palaeozoic succession in SE Poland and West Ukraine has source rock potential, particularly the Ordovician and Silurian which contain oil‐prone Type II kerogen. The thermal maturity of these units ranges from early to late‐phase oil window (locally up to gas window). Within the Mesozoic succession, source rock potential is highest in the Middle Jurassic which has TOC of up to 26 wt% and a genetic potential of up to 39 mg/g of rock, with organic matter dominated by gas‐prone Type III kerogen. In SE Poland, the organic matter in this unit is generally immature, whereas maturities in West Ukraine are sufficient for hydrocarbon generation to occur. Modelling of hydrocarbon generation suggested that petroleum in Lower Palaeozoic source rocks began to be generated in the Early Carboniferous. Peak generation took place from the late Visean to the early Namurian, and terminated either as a result of source rock depletion or Variscian inversion. Expelled hydrocarbons migrated during post‐Carboniferous and Mesozoic uplift. Middle Jurassic source rocks in SE Poland have only reached the early oil window. Higher thermal maturities in the Ukraine resulted in hydrocarbon generation and expulsion. This took place after Miocene burial and maturation. A number of small hydrocarbon accumulations occur in Mesozoic reservoirs in SE Poland / West Ukraine, and hydrocarbons have migrated from Cambrian and Ordovician source rocks. However, the prospectivity of the study area is reduced as a result of phases of uplift and intense erosion which allowed hydrocarbons to escape from structural traps.

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