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The potential for locating hydrocarbon traps in the Rotliegend formation, based on the results of experimental seismic surveys

Maćkowski T., Kwolek K., Górecki W.

Geology, Geophysics and Environment

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2017

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Vol. 43, no. 3

191--199

EN

Within the framework of the Operational Programme Innovative Economy 2007-2013, studies were carried out for improving the effectiveness of using seismic surveys in the prospecting and exploration of gas fields in the Rotliegend formation. The completed experimental seismic surveys provided new, very interesting data on the geological structure of the deeper part of the Rotliegend basin (>4000 m), which is practically very important for prospecting for new gas fields. The interesting results were obtained along virtually the entire cross-section, particularly in two segments: the southern segment – in front of and within the Człopa-Szamotuły tectonic zone (the Szczecin-Gorzów segment) and the northern segment – in the area of the Zabartowo-1 and Zabartowo-2 wells (the Pomeranian segment). In the northern segment, for the first time in the history of studies of the Lower Permian Basin, it was possible to record reflections from the horizon of the aeolian sandstones occurring within the playa silty-clayey deposits (543 m below the top of the Rotliegend formation), which represents a significant achievement from the point of view of prospecting for hydrocarbon resources. This horizon, characterized by favourable reservoir properties, pinches out northward. It is a very important piece of information because systems oflithologic traps may be related to such pinchouts. In the central part of the Obrzycko-Zabartowo profile, in the Chodzież area, a vast structural elevation occurs, approximately 10–12 km wide and with the amplitude of 250–300 m, which may be a potential large structural or structural and lithologic trap. These newly discovered zones of occurrence of gas traps in the seismic profiles made by the AGH University of Science and Technology within the framework of the research project, will be implemented in a detailed seismic exploration during the exploratory work of Polish Oil and Gas Company (PGNiG SA).

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X-ray micro computed tomography characterization of porosity in Rotliegend sandstones on the northern slope of the Wolsztyn Ridge, western Poland

Poszytek A., Mikołajewski Z., Dohnalik M.

Geological Quarterly

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2016

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Vol. 60, No. 4

801-810

EN

Natural gas in the Polish Rotliegend Basin occurs in porous and permeable aeolian sandstones, and traps are mostly structural. Lithological traps are rare and occur on the northern slope of the Wolsztyn Ridge where fluvial and aeolian sandstones overlap with alluvial facies. Both fluvial and aeolian sandstones are reservoir rocks in this area. The X-ray micro computed tomography (MCT) results and microscopic observations indicate that the sandstones in lithologic traps on the northern slope of the Wolsztyn Ridge form highly compartmentalized vertical reservoir rocks composed of four types of sandstones. The profiles are dominated by very low-porosity fluvial sandstones (F2), and low-porosity aeolian and fluvial sandstones (A2, F1). The A1 type of sandstones with high porosity (10%) occurs only in some sections of the profiles. The most important diagenetic processes that reduced porosity were compaction and cementation by carbonate cements. All studied sandstones were subjected to the same diagenetic processes. However, each of the processes ran with varying intensity in different types of sandstones. Detailed analyses of pore distribution by MCT methods with respect to primary depositional or lithofacies effects, and secondary diagenetic effects, help to understand the 3D geometry of pores and pore shape-size distributions. The results can be used in the studies of other sandstones with a different origin and age.

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Poszukiwanie pułapek litologicznych w utworach czerwonego spągowca na NE skłonie wału wolsztyńskiego

Kwolek K., Solarski T., Buniak A.

Prace Instytutu Nafty i Gazu

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2004

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nr 130

75

PL

Zdecydowana większość złóż gazu ziemnego w piaskowcach czerwonego spągowca odkrytych na obszarze monokliny przedsudeckiej uformowała się w typowych pułapkach strukturalnych. Do nielicznych wyjątków należą złoża strukturalno-litologiczne Paproć i Ujazd. Ich pułapki sąkombinacją linii zasięgu piaskowców górnego czerwonego spągowca w strefie marginalnej (na północnym skłonie wału wolsztyńskiego), granicy sejsmicznej Z1' związanej ze spągiem cechsztynu oraz powierzchni kontaktu gaz — woda. Kartowanie granicy Z1' na ogół nie stwarza dzisiaj problemów, ale precyzyjne określanie linii zasięgu ww. piaskowców, oparte niemal wyłącznie na interpolacj i międzyotworowej, wciąż napotyka na bardzo duże trudności. Poster przedstawia stosunkowo prosty sposób metodycznego podejścia do przedstawionego wyżej problemu. Według przeprowadzonych analiz sejsmicznych i geologicznych wydaje się, że najlepszym sposobem detekcji zmian facjalnych i związanych z nimi stref zaniku właściwości zbiornikowych, a tym samym — zasięgu porowatych piaskowców górnego czerwonego spągowca, jest analiza zmian amplitudy granicy sejsmicznej Z1' połączona z korelacją pojawiającego się bezpośrednio poniżej refleksu dodatniego, powstającego na kontakcie piaskowców eolicznych z pierwszym od góry profilu poziomem zlepieńców.

EN

Several gas fields in Rotliegendes sandstones have been discovered within the area of Fore-Sudetic Monocline. Most of the fields were formed in typical structural traps, where reservoir rocks belong to aeolian sandstones composing the uppermost part of Rotliegendes deposits. The few exceptions are structural-lithologic traps of Paproć and Ujazd gas ńelds in the western part of the Poznań Trough. These traps are determined by a combination of the extent line of porous, permeable Rotliegendes sandstones and the geometry of the Z1' seismic horizon (related to the base of Zechstein) in the peripheral zone on the northern slope of the Wolsztyn High. Mapping of Z1' horizon, in general, does not cause any difficulties, at present however, precise determination of the extent line of reservoir rocks still encounters serious problems. In accordance with performed geological and geophysicał analyses it seems that the best available tool of detecting zones of porous sandstones within the uppermost part of upper Rotliegendes deposits is detailed analysis of Z1' reflection amplitude correlated with the appearance of positive reflection directly below.