An Integrated Approach for the Thermal Maturity Modeling Re-Assessment of an Exploration Well in the Hellenides Fold and Thrust Belt

Abstract

Utilizing geological and geochemical data, we re-assessed the thermal maturity of the Lower Cretaceous Vigla shales of the AY-3 well, located in the Internal Ionian geotectonic zone of Greece, using 1D thermal maturity modeling. Vigla shales primarily containing kerogen type I to II, incorporated within alternations of carbonates, cherts, and marly limestones, were selected as the main source rock intervals. Biomarkers and Rock-Eval data were used on top of vitrinite reflectance data for the calibration of the 1D model. Hopane and sterane isomerization ratios for the Vigla shales appear to hold values of 58–64% and 44–49%, respectively, while vitrinite reflectance ranges from 0.61% to 0.71% and Tmax between 431 and 451 °C. One-dimensional thermal maturity modeling suggests that lower Cretaceous Vigla shales entered the oil window in early Miocene times and reached the expulsion onset during the middle Miocene. Additionally, thermal modeling estimates the overburden eroded thickness to range between 2.1 and 2.6 km. This unravels the pre-eroded shape of this part of the belt of Miocene times alongside the burial history of the area and its evident relation to the hydrocarbon potential. This assessment comprises a step towards the understanding of the belt and the different timings of hydrocarbon generation in the External Hellenides.