Polish shale gas deposits in relation to selected shale gas prospective areas of Central and Eastern Europe

Przemysław Karcz, Marcin Janas, Ireneusz Dyrka

Abstract


A b s t r a c t. This paper describes a regional overview of selected Central and Eastern European sedimentary basins which hold the unconventional potential for shale gas and shale oil exploration that have attracted interest in the last few years. Organic-rich fine-grained rocks like black and dark-grey shales, mudstones and claystones with varying ages from Cambrian to Miocene are distributed very irregularly across Europe. A long-lasting, dynamic geological evolution and continuous reconstruction of the European continent resulted in the formation of many sedimentary basins. In some basins, biogeochemical conditions favoured preservation of accumulated organic-rich deposits and led to the generation of hydrocarbons
after burial and reaching appropriate maturity levels. Even though shale gas and shale oil exploration in Europe is still in its infancy, shale formations were analyzed before as the source rocks in conventional petroleum systems. Parameters that were used to describe source rocks e.g.: total organic carbon, maturity, thickness, depth of occurrence and areal extent, can indicate preliminary potential for shale gas exploration and allow estimating first resource values. Currently the most intense shale gas exploration takes place in Poland where over 42 wells have been drilled and over 100 concessions for unconventional hydrocarbon exploration have been granted. Upper Ordovician and lower Silurian shales at the East European Craton (Baltic, Lublin and Podlasie basins) are the major targets for unconventional exploration in Poland. In Central and Eastern Europe, evaluation of the unconventional potential of gas-bearing shale formations is carried out also in Ukraine, Lithuania, Austria, Czech Republic, Hungary, Romania, Bulgaria, Moldova and the European sector of Turkey. Despite the fact that each shale rock differs from another by geochemical, petrographical, petrophysical, mechanical and other parameters, some similarities can be seen such as marine type of depositional environment with the predominance of type II kerogen or specific organic matter content. Recoverable resources of shale gas throughout Europe are believed to be as large as 17.67 trillion m3 (624 Tcf) and Poland, Ukraine, France with United Kingdom are thought to have the greatest resources.

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