--> Geological setting and reservoir heterogeneity of Lower Paleozoic shales in the Lublin Basin (Poland) and its impact on exploration

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Geological setting and reservoir heterogeneity of Lower Paleozoic shales in the Lublin Basin (Poland) and its impact on exploration


The Lower Paleozoic, Ordovician and Silurian shale succession represents key prospective horizons in the Lublin basin defined as unconventional resources. For almost the last three years E&P companies have conducted research to evaluate HC potential, estimate resources and confirm reserves. During this time, across an area of nearly 20,000 sq. km, which covers the Lublin basin and part of the Podlasie basin, 24 new boreholes have been drilled, 11 of which have been drilled by ORLEN Upstream (7 vertical and 4 horizontal wells). Almost 1,800 m of core samples were recovered from the wells when performing coring operations and raised to the surface for study and detailed analysis. In addition to the drilling operations, ORLEN Upstream has conducted about 1,250 km of new 2D seismic surveys, reprocessed and interpreted more than 5,000 km of 2D seismic profiles and also more than 150 sq. km of 3D seismic data. Our top priorities were: to understand the structural evolution of the Lower Paleozoic succession, and detailed definition of the main reservoir parameters of Ordovician and Silurian shales and their extension. The analysis of the parameters' variability was performed (heterogeneity rock analysis). It involved wellbore, interwell and fieldwide scale heterogeneities and used cores, logs, seismic, structural and facies analyses. The preliminary results from the ten wells drilled by Orlen Upstream in the Lublin Basin confirmed the general, known trends of shale succession and high tectonic complexity within the research area. However, a noticeable variation of the main reservoir and geochemical parameters and geomechanical properties of the rock occurred both along and across the Lublin basin. There is a notable correlation between the level of transformation of organic matter and the depth of the horizons; no evidence of reservoir overpressure and a relatively high level of anisotropy of the stress regime. The number of drilled wells and production tests is currently insufficient to determine the relationship between the results obtained during the analysis and for estimation of the productive potential of Lower Paleozoic shale succession.