Integrated Reservoir Connectivity Analysis, Zechstein Carbonate Reservoir, Northern German Basin

An integrated workflow is presented for evaluating static and dynamic connectivity of a complex Upper Permian Zechstein carbonate reservoir, mainly platform facies, in the Scholen Concession of the Northern German Gas Basin. Sour gas production in the concession involves drainage from multiple, tectonically emplaced and, in places, vertically stacked allochthonous Zechstein carbonate reservoir sections. These allochthons lie within the Permian Zechstein salt and overlie the in-place autochthonous Zechstein reservoir. The key issues in the Scholen Concession are the static connectivity and fill-and-spill scenarios among the multiple Zechstein sour gas accumulations and the dynamic connection between the autochthonous and allochthonous reservoir intervals. Understanding these issues is important in the evaluation of infill drilling opportunities and near-field appraisal wells, and whether or not these opportunities can be drilled safely and economically. The integrated reservoir connectivity analysis incorporating geoscience and reservoir engineering data revealed that the five main gas accumulations in the concession appear to be connected statically through a common aquifer and the in-place autochthon and most detached allochthons likely are connected dynamically with baffles. These learnings ultimately led to realistic and reliable evaluations of infill opportunities and near-field appraisals in the concession area, and changes to the drill-well inventory seriatim.