No abstract

Abstract: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 of lithologic 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).

In the Zielin oilfield in the Polish part of the Southern Permian Basin, oil and gas are produced from an Upper Permian Main Dolomite (Ca2) isolated platform. The paleohigh developed on a volcanic cone formed in Early Rotliegend time. Based on microfacies analysis of Ca2 reservoir rocks from four wells (Zielin-1,-2,-3 and-3KBis), four microfacies types are distinguished: peloidal dolomitized wackestone, intraclastic dolomitized rudstone and floatstone, biogenic boundstone, and intraclastic-bioclastic dolomitized packstone. In view of the lack of source rocks on the Zielin paleohigh revealed by Rock-Eval analyses, this isolated carbonate platform is regarded as a reservoir for migrating hydrocarbons. Biomarker analyses of two crude oils and nine carbonate rocks from the Zielin isolated carbonate platform and five crude oils from surrounding wells of the nearest Gorzów, Cychry, and Namyślin platforms indicate an origin for the oils from oil-prone type II kerogen, sourced from organic matter deposited under anoxic/suboxic conditions in a carbonate environment. Compared to organic matter extracted from the rock samples, oils from the Zielin-2 and 3KBis wells are characterized by higher values of the pristane/ phytane (Pr/Ph) and dibenzothiophene/phenanthrene (DBT/P) ratios, lower relative concentrations of polyalkylaromatics, as well as a higher maturity evaluated from the methylphenanthrene (MPI-1) and methyldibenzothiophene (MDR) indices. The molecular composition of sesquiterpanes, n-alkylbenzenes, and polyalkylnaphthalenes revealed a diverse specificity within the oils analyzed and allowed their separation into two groups. Oils Różańsko-4, Zielin-2, Zielin-3KBis, and Namyślin-1 represent group I, whereas Barnówko-3, Mostno-2 and Cychry-2 group II. From the gradient direction in the n-decane/ naphthalene ratio and maturity for respective crude oils belonging to group I, it is concluded that the oils accumulated in the Zielin atoll migrated from NW to SE following subsidence and tilting of the platform in this part of the Main Dolomite basin.

No abstract

No abstract