1-D modelling of the hydrocarbon generation history of the Jurassic source rocks in the Tarnogród-Stryi area (SE Poland - western Ukraine)

Paweł Kosakowski, Magdalena Wróbel, Yuriy V. Koltun

Abstract


Reconstruction of burial and thermal history was modelled for the Mesozoic strata in the basement of the Polish and Ukrainian parts of the Carpathian Foredeep and in the marginal part of the Outer Carpathians. The 1-D modelling was carried out in profiles of the wells located in the area between Tarnogród and Stryi towns. In the Polish part, the modelling were performed in the profiles of the Księżpol 15, Lubliniec 9, Markowice 2 and Opaka 1 wells, and in the Ukrainian part in the profiles of the Chornokuntsi 1, Korolyn 6, Mosty 2, Podiltsi 1 and Voloshcha 1 wells. The geochemical characteristics of the Mesozoic stratigraphical horizons revealed that the best features of source rocks were present in the Middle Jurassic strata in the Polish part of the study area and in the Middle and Upper Jurassic strata in the Ukrainian part. Within these strata, the horizons of source rocks were distinguished and their quantitative evaluations were characterized. For these horizons, reconstruction of processes for hydrocarbon generation and expulsion were performed. The source rocks in the Polish part reached maturity only in the initial phase of “oil window”. However, the maturity achieved towards the end of the Upper Jurassic was insufficient to exceed the 10% threshold of the transformation degree for hydrocarbon generation. Therefore, the amount of generated hydrocarbons was minimal. Slightly higher maturity of organic matter in the Ukrainian part resulted in exceeding the thresholds of kerogen transformation and the initiation of hydrocarbon generation and expulsion processes. The process began after the deposition of thicker Miocene formations and developed even up to the main phase of the “oil window”. The amount of the generated hydrocarbons reached ca. 150 mg/g TOC with an insignificant volume of expulsion.

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