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Complex Petroleum Systems of Sea of Azov - Southern Russia
Conference Paper · February 2012
DOI: 10.3997/2214-4609.20143892
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Geological Survey of Serbia
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Complex Petroleum Systems of Sea of Azov Southern Russia
E. Lavrenova (Soyuzmorgeo), D. Spahic* (Schlumberger) & A. Gorbunov
(Soyuzmorgeo)
SUMMARY
Nowadays majority of successful oil and gas discoveries are a result of the sophisticated studies combined
with the most recent exploration techniques applied on variety of depositional complexes. One of the
proven methods that largely decrease uncertainties in hydrocarbon exploration is numerical petroleum
system modeling.
By using different petroleum system modeling tools like 1D, 2D & 3D modeling here we investigate
complex petroleum system of the southern Russia (Sea of Azov). The subsequent numerical models
highlighted a new hydrocarbon system nested within the poorly explored transitional complex of the Sea
of Azov.
Petroleum Play Assessment Workshop
13-15 February 2012, Malaga, Spain
Introduction
Nowadays majority of successful oil and gas discoveries are a result of the sophisticated studies combined with
the most recent exploration techniques applied on variety of depositional complexes. Each new hydrocarbon
discovery is in most cases a consequence of complex exploration strategy that often results in a discovery of
new hydrocarbon objects. However, in addition to high exploration costs, sometimes traditional geological
exploration methods require undesired additional expenses that often affect overall economic success.
Commonly in last decades, in order to reduce risks and avoid any additional expenses, integration of geological
databases with subsequent risk assessment has been used by many exploration-production companies. One of
the proven methods that largely decrease uncertainties in hydrocarbon exploration is numerical petroleum
system modeling.
By using different petroleum system modeling tools like 1D, 2D & 3D modeling here we investigate complex
petroleum system of the southern Russia (Sea of Azov, Fig.1). The subsequent numerical models disclosed a
new hydrocarbon system nested within the poorly explored transitional complex (TC) of the Sea of Azov (Fig
2).
The transitional complex of Sea of Azov is a geological object that lies below the well-known Cenozoic
productive system (Fig 3). The system is represented by Late Paleozoic and Mesozoic carbonate-clastic system
that is crosscut by the extensional deformations. Unfortunately, by using traditional exploration tools, the TC
has been only partially explored: poor seismic visualization data, lack of deep exploration wells, scattered
geochemical data, etc. Nevertheless, by using petroleum system analysis and associated numerical calculations
in PetroMod software we integrated available datasets and subsequently we quantify the hydrocarbon potential
of the TC. Results have shown that the investigated Paleozoic-Mesozoic petroleum system has significant
hydrocarbon potential.
Hydrocarbon saturation of the sediment cover in the Sea of Azov is defined usually by deep exploration well
data. Several small gas fields are discovered within the Cenozoic system, for example Strelkovoye,
Beysugskoye, Vostochno-Kazantipskoye, etc., as well as the small oilfield - Novoe. Additionally, there are
several discoveries among older Eocene deposits: Maikopian play (Morskaya, Nebolshaya,
Electrorazvedochnaya, Strelkovaya, Severokazantipskaya fields) and Middle-Upper Miocene system
(Obruchevskaya, Oktiabrskaya, Severo-Kerchenskaya, Seismorazvedochnaya, Zapadnobeisugskaya, etc, Fig.4).
All identified reservoirs are productive mostly gas-saturated. Preliminary investigations indicated that these gas
occurrences are most likely associated to the underlying TC. In order to verify such hypothesis, we investigated
maturity and potential of the Tertiary petroleum system (1D basin model of the borehole Oktiabrskaya).
.
Figure 1 Geographical position of the Sea of Azov including vicinity of mountain Caucasus (modified after Stovba & Stephenson, 2003).
Petroleum Play Assessment Workshop
13-15 February 2012, Malaga, Spain
Figure 2 There are four main structural elements in the study area: the North Azov Depression, Azov Swell, South Azov Step, IndoloKuban Foredeep.
Figure 3 There are two opposite opinion about geological structure of the transitional complex and about its prospects: transitional complex
consist of dislocated over matured rocks. Presence of petroleum system is impossible. Transitional complex consist of normal sedimentary
rocks, presence of petroleum system is possible (modified after Lavrenova & Kruglyakova, 2010).
Petroleum Play Assessment Workshop
13-15 February 2012, Malaga, Spain
1- oil
2- gas
3 - age of reservoir
4 - well 's name
Figure 4 Hydrocarbon discoveries across Sea of Azov.
Results of the1D model indicated that source rocks in the Cenozoic sediments on the Azov Swell cannot exist
(insufficient thermal maturity). In fact, Cenozoic gas shows on the Azov Swell are epigenetic to the investigated
sediments. Nevertheless, the investigation confirmed that in addition to a well-known Cenozoic petroleum
system in the South-East part of the Sea of Azov, a pod of active source rock (lower Maikopian clay) is located
within the Indolo-Kuban foredeep. Oil and gas accumulations that are genetically associated to Kuban foredeep
can be expected exclusively in the upper Cenozoic sediments of Indolo-Kuban Fore-deep and South-Azov Step.
After extensional tectonic event resulting in accommodation of normal faults, a vertical migration of
hydrocarbons was enabled. It seems that hydrocarbons produced within the TC have migrated vertically and
subsequently penetrated into the Tertiary sediments deposited along the Azov Swell. The direct TC gas shows
that have been detected boreholes Oktiabrskaya and Zapadno-Beysugskaya fields indicated that the only
possible explanation of deeper gas accumulations is that they originate from the underlying TC. Furthermore, by
using 2D regional model we investigate lateral migration potentials whereby the results clearly showed that
there is not enough migration time for hydrocarbons to migrate towards the distant accumulations of the Azov
Swell (Fig 5). Finally using the 3D petroleum system modeling we quantified general hydrocarbon potential of
the TC.
Figure 5 Complex 2D basin modeling used to check later migration possibilities from Idolo-Kuban foredeep to Azov swell. Results are
showing that migration could not reach the top of Azovian sweal due to insufficient timing and migration losses (modified after Lavrenova
et al., 2011).
Petroleum Play Assessment Workshop
13-15 February 2012, Malaga, Spain
Conclusions
Origin of the gas shows in Cainozoic sediments of the Sea of Azov has been discussed. Using numerical
petroleum system modelling is proved that there no source rocks in the sediment cover genetically associated to
the gas shows. Therefore it is to conclude that the investigated hydrocarbon system belongs to the hypothetical
petroleum system of the Transitional complex. Thus the transition complex can be considered as a promising
object for hydrocarbons prospecting. Nevertheless, in order to test hypothetical petroleum system additional
investigations are required. Further investigations could decrease the main risks associated to the investigated
petroleum system - presence of quality hydrocarbon reservoirs.
References
Lavrenova E., Kruglyakova M. (2010): Specific features of temporal and spatial distributions of light
hydrocarbons in the Sea of Azov. Geo-Marine Letters.V 30(3), p. 249-260 (DOI 10,1007/S00367-009-0175-1).
Lavrenova, E., Kruglyakova, M., Gorbunov, A., Spahic D., Sokolov, K. (2011): Oil and gas potentials of Azov
Sea bar deposits as indicator of active transitional system of hydrocarbon generation and accumulation in
eastern part of Sea of Azov (according to results of numerical basin model). 13 EAGE conference. Gelendzik.
Russia (in Russian)
Stovba S.R., Stephenson S.A. (2003): Style and timing of salt tectonics in the Dniepr-Donets Basin (Ukraine):
implications for triggering and driving mechanisms of salt movement in sedimentary basins. Marine and
Petroleum Geology 19. p 1169–1189
Petroleum Play Assessment Workshop
13-15 February 2012, Malaga, Spain
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