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T.B. van Hoof, TNO-Geological Survey of the Netherlands (Netherlands)
O.A. Abbink, TNO-Geological Survey of the Netherlands (Netherlands)
J.H.A van Konijnenburg-van Cittert, Nationaal Natuurhistorisch Museum, Naturalis (Netherlands)
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Recently, renewed interest in the hydrocarbon reservoir potential of middle Silesian (Westphalian) strata of the North Sea basin led to an increasing demand for a high resolution and solid stratigraphical framework for the Westphalian. At the moment the main biostratigraphical tool to provide chronostratigraphical information for exploration wells in NW European Westphalian strata is classic palynostratigraphy based on first and last occurrences of sporomorph taxa. The application of this methodology is hampered by the observed spatial variation in distribution of sporomorph taxa and the often poor preservation of marker taxa.
A new approach in palynostratigraphy is based on the so-called sporomorph ecogroup model concept (SEG), which was developed for Jurasic deposits in the North Sea basin. With this methodology sporomorphs are linked to the parent-plant, which makes a detailed palaeo-ecological interpretation of the quantitative palynological signal possible. The by this way detected changes in environment and/or climate can be used to enhance the stratigraphical correlation of wells and provides detailed information about facies distribution patterns. In this study a SEG model is developed for the Westphalian and applied to the Dutch onshore well Kemperkoul-1 (Westphalian B/C) and several wells in the Dutch offshore (D-E blocks). A comparison between the detailed palaeoenvironmental and climate reconstructions based on the SEG model and the sedimentological and paleontological analysis in well Kemperkoul-1 is made to test the outcome of the SEG model results. Furthermore, the SEG model approach enabled the detection of regional changes in facies distribution in the offshore D-E area during the Westphalian. Based on this study it can be concluded that combined application of classical palynostratigraphy with a SEG model approach enhances the stratigraphical resolution and accuracy of Westphalian chronostratigraphical interpretations based on biostratigraphy. Furthermore, the detection of changes in the regional facies distribution by the SEG approach provides a new tool for reservoir characterization during the Westphalian.
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