Scholarly record

HYDROCARBON POTENTIAL OF ORDOVICIAN AND SILURIAN SHALE COMPLEXES IN THE CENTRAL PART OF THE BALTIC BASIN, POLAND - CASE STUDY

Bartosz Papiernik, Bartlomiej Liana, Michal Michna, Gabriel Zabek, Justyna Zajac

Abstract

Shale gas potential assessments completed in 2010 for the Baltic Basin (BB) were very optimistic. They placed most of the central part of the BB in the gas window, indicating high prospectiveness of the most of Ordovician, Llandovery and Wenlock deposits. The paper presents results of multicomponent spatial geomodelling, which strongly modify this concept. The model covers area located in the central part of the BB, comprising Kartuzy Szemud and Stara Kiszewa concession blocks. Its area is about 300 km2 and it incorporates both dry and liquid gas zones. 3D grid horizontal resolution is approximately 200 x 200 m and vertical resolution depends on thickness and variability of investigated complexes, resulting in 27, 3 mln of grid cells. The model includes chrono- and litostratigraphical units of Wenlock, Llandovery (divided into Pas??k Formation and Jantar Member), and Ordovician (Prabuty Formation and Sasino Formation). The most prospective are the mudstones of Wenlock, Jantar Member and Sasino Formation. The structural and the parametrical models were constructed based on 2D and 3D seismic data and high quality geophysical logs in 8 wells. Parametric models of reflectivity, facies, total and effective porosity, clay, carbonate and quartz volume, TOC, adsorbed gas, dissolved gas, free (dry) gas and liquids volumes were completed. As a result it was established that the dry gas window covers only about 60 km2 in the south-western part of the research area. The most promising complex in this zone is Jantar Member, followed by Sasino Formation Wenlock deposits. The other complexes are in practice not prospective. Most of the area (~250 km2) belongs to the liquid window modelling results indicate that Sasino Formation is on average the most condensate-prone complex in this area. Wenlock deposits turn out to be not prospective. Results of modelling practically exclude prospectivity of Wenlock deposits in the area. They confirm moderate petroleum potential of Sasino Formation and Jantar Member. They also show that gas-prone shales in the BB are buried to depths close to 4000 m bsl, which dramatically increase risk and costs of unconventional prospection in this region.

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