Burial and Thermal History Modeling of the Paleozoic–Mesozoic Basement in the Northern Margin of the Western Outer Carpathians (Case Study from Pilzno-40 Well, Southern Poland)

Dariusz Botor

doi:10.3390/min11070733

Abstract

Hydrocarbon exploration under thrust belts is a challenging frontier globally. In this work, 1-D thermal maturity modeling of the Paleozoic–Mesozoic basement in the northern margin of the Western Outer Carpathians was carried out to better explain the thermal history of source rocks that influenced hydrocarbon generation. The combination of Variscan burial and post-Variscan heating due to elevated heat flow may have caused significant heating in the Paleozoic basement in the pre-Middle Jurassic period. However, the most likely combined effect of Permian-Triassic burial and Late Triassic–Early Jurassic increase of heat flow caused the reaching of maximum paleotemperature. The main phase of hydrocarbon generation in Paleozoic source rocks developed in pre-Middle Jurassic times. Therefore, generated hydrocarbons from Ordovician and Silurian source rocks were lost before reservoirs and traps were formed in the Late Mesozoic. The Miocene thermal overprint due to the Carpathian overthrust probably did not significantly change the thermal maturity of organic matter in the Paleozoic–Mesozoic strata. Thus, it can be concluded that petroleum accumulations in the Late Jurassic and Cenomanian reservoirs of the foreland were charged later, mainly by source rocks occurring within the thrustbelt, i.e., Oligocene Menilite Shales. Finally, this work shows that comprehensive mineralogical and geochemical studies are an indispensable prerequisite of any petroleum system modelling because their results could influence petroleum exploration of new oil and gas fields.

Highlights

Hydrocarbon exploration under thrust belts is a challenging frontier, both in the Carpathians and, in general, globally, e.g., [1,2]
If the pre-Triassic heating was responsible for the thermal maturity of the Paleozoic samples, it should be possible to observe a jump of vitrinite reflectance (VR) gradient between
In the frontal Carpathian orogenic wedge, the Paleozoic source rocks in the basements likely reached maximum heating in the Late Triassic to Early Jurassic period, which caused a major phase of hydrocarbon generation

Summary

Introduction

Hydrocarbon exploration under thrust belts is a challenging frontier, both in the Carpathians and, in general, globally, e.g., [1,2]. The most intriguing feature of the occurrence of oil and gas fields around the Carpathians and its foredeep is their existence within the orogen, and within a relatively short distance from the orogenic front [3]. This highlight can be noticed along the entire Carpathian arch from Czechia across Poland, and Ukraine to Romania. 13 natural gas fields and 10 oil fields have been discovered in the Mesozoic and Paleozoic of the Carpathian Foredeep and the sub-Carpathian basement These fields have combined reserves of 7.5 billion cubic meters of gas and 4.7 million tons of oil [4]

Methods

Results

Discussion

Conclusion