Implication of cenozoic tectono-sedimentary evolution for the geoenergy potential in the NW Transcarpathian Basin

Abstract

The extensive Pannonian Basin System comprises several hydrocarbon-bearing sub-basins, including the moderately explored Transcarpathian Basin located in its NW part. Tectono-sedimentary and volcanic events have influenced the sub-basin's infill and geoenergy potential. Through a comprehensive analysis of petrophysical, organic geochemical, sedimentological, and biostratigraphic data, we aim to uncover the characteristics of petroleum and geothermal plays in the challenging-to-sample Prešov depocenter (NW corner of the Transcarpathian Basin) and its surrounding areas. The results highlight two significant tectono-sedimentary events: first, the opening and subsequent disintegration of the compressional foreland Central Carpathian Paleogene Basin, and its Lower Miocene continuation, which facilitated the deposition of source rocks. Second, the initial phase of rifting in the transtensional Prešov sub-basin, part of a broader back-arc system, created accommodation space for Karpatian to Badenian (Burdigalian to Serravallian) facies. This process led to the formation of fault system that deformed whole sedimentary infill, including the preCenozoic basement carbonates, which resulted in the creation of structural traps and pathways for horizontal and vertical migration. This research reaffirms the geoenergy potential of Paleogene sedimentary records in Central Europe as viable source rocks for hydrocarbons. Contrary to established knowledge, organic lean kerogen type III appears to not only produce methane gas but also wet gas. A promising hydrocarbon trap has been identified in the Triassic to basal Paleogene carbonate breccia reservoirs, though it includes a risk of CO2 and N2 contamination. Notably, this risk diminishes in the uppermost sections of the carbonate traps, where the highest concentrations of methane and wet gas are found, likely due to the gravitational separation of gases by molecular weight. Additionally, these carbonate breccias show moderate geothermal potential.