Article
The influence of the thrust over the evolution of the thermal regime of the Vrancea Nappe source rocks (Eastern Carpathians). A 1D simulation of the Șipoteni oil structure (Romania)
Ciprian Chelariu - “Al. I. Cuza” University of Iaşi, Faculty of Geography and Geology, Department of Geology, 20A Carol I Blv., 700505 Iaşi, Romania, Department of Geology Cristina Negru - “Al. I. Cuza” University of Iaşi, Faculty of Geography and Geology, Department of Geology, 20A Carol I Blv., 700505 Iaşi, Romania, Department of Geology
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Abstract:
The aim of the present paper is to highlight the variations in thermal regime caused by the thrusting of
the Tarcău Nappe over the Vrancea Nappe during the New Styrian tectono-genesis. The onedimensional
analysis was carried out for the sedimentary column opened by the S300 well within the
Șipoteni oil structure (Comănești Basin area). This involved the overlapping of the temperature
isolines over the burial curves of the source rock-bearing formations. The computation of
temperatures for the time period after the thrust was performed using the equation for heat transfer in
an unsteady regime (Angevine and Turcotte, 1983), which requires knowing certain local physical
and thermal parameters. Regarding the thermal parameters, given the lack of laboratory or in situ
measurements, thermal diffusivity was indirectly estimated, through mathematical simulation, while
the thermal gradient of the structure was established using temperature measurements carried out at
various depths during the well-digging process. As far as the other parameters (regarding thickness
and other aspects of the nappes) are concerned, they were determined based on the back-stripping
analysis and the history of sediment burial, being closely related to the local conditions of the nappes.
The results obtained have shown that, for the oil structure studied, the influence of the thrust over the
thermal regime was not great enough to be considered a major factor in the generation of hydrocarbons
from the source rocks. It was most likely the thickness of the thrust nappe which had an essential role.
In other areas, where it was considerably larger, the former may have even played a decisive part.
Keywords:
thrust, back-stripping, hydrocarbon source rocks, Șipoteni, thermal regime
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