25th International Meeting on Organic Geochemistry IMOG 2011

P-289
Correlation of crude oils reservoired in the Polish Carpathian
oilfields (the Silesian and Skole Units)
Irena Matyasik 1 , Wojciech Bielen 1 , Marek Janiga 1 , Leszek Jankowski 2
1 Oil and Gas Institute, Cracov, Poland, 2 Polish Geological Institute, Cracov, Poland (corresponding
author:matyasik@inig.pl)
This region is located in the eastern part of
the Polish Outer Carpathians; traditionally there are
distinguished three tectonic units: the Silesian Unit in
the south, the Weglowka Unit and the Skole Unit in
the north. Oil fields are stretched on both sides of the
Weglowka Unit zone or its prolongation (eastern
direction).
This oil fields are located within the tectonic
flower structure and the role of the master fault acts
the Weglowka ramp. Tectonically active zone of the
ramp is a place of hydrocarbons migration but also
may be an insulating zone.
Until now, there is no clear explanation of the
origin of crude oils accumulated in different tectonic
units of the Carpathian Flysch. [2] One of the source
rocks, which shows a positive correlation with the
most of crude oils in this region are Menilite Beds. As
part of the correlation works GC, GC/MS and
EA/IRMS analysis were performed. Studied crude oils
were collected from the eastern part of the Silesian
Unit (Grabownica Fold) and the folds of the Skole Unit
(Łodyna-Wańkowa Fold, Brzegi Dolne well).
The correlation was performed in order to
determine sedimentation environment, type of
sediment, thermal maturity and degree of degradation
of oils (by geochemical indicators). The results
indicated a distinction between crude oils of the
Silesian Unit and the Skole Unit. Parameters
differentiating those oils are: sulfur content, Pr/Ph
indicator, isotopic composition (δ 13 C) and the
presence of bisnorhopane and tricyclic terpanes.
Crude oils of Skole Unit have a low sulfur content
and crude oils of the Silesian Unit are classified as
unsulphur. Bisnorhopane is present only in crude oils
of the Skole Unit, however tricyclic terpanes were
present (in high concentrations) in crude oils of the
Silesian Unit. Bisnorhopane presence can be
explained in three ways: degradation of crude oil (not
always confirmed by other factors) or bacterial activity
in the destruction of organic matter during
sedimentation in a shallow reservoir or paleoleakage.
Crude oils of the Grabownica Fold have high Pr/Ph
indicator (>2). Geochemical indicators of crude oils of
the Skole Unit show various sedimentation conditions
(from unoxic through sub-oxic to oxic environment). In
addition, variation of the the Silesian Unit and the
Skole Unit crude oils was confirmed by carbon
isotopic composition.
All those parameters were correlated with
corresponding parameters obtained from the
analysis of outcrop samples representing Menilite
Beds. All outcrops samples of the Skole Unit showed
a low thermal maturity (proved by Tmax and
biomarkers distribution – steranes), which excludes
those Menilite Beds as a source rock of crude oils
accumulated in the Skole Unit folds. However genetic
signatures (for example presence of BNH, isotopic
composition) may suggest that deeper Menilite Beds
(in Brzegi Dolne or Paszowa wells) are source rocks.
[1] Crude oils of the Silesian Unit may have another
source rock.
References:
[1] Kuśmierek J., Subsurface structure and tectonic
style of the eastern Polish Carpathians on the basis of
integrated 2D interpretation of geological and
geophysical image.
[2] Więcław D., Kotarba M. J., Koltun Y., Identification
of kerogen type in the menilite shales of the Skole
and Silesian units of the Polish and Ukrainian
Carpathians.
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