Herkunft, Auftreten und Visualisierung von Permeabilitätsbarrieren in einer Gaslagerstätte in Sandsteinen des Rotliegenden (Südliches Permbecken, Deutschland): Bedeutung für Diagenese, Fluidfluß und Produktion

Continental clastic sediments were deposited during the late Permian (Upper Rotliegend) in the Southern Permian Basin and represent the economically most important gas reservoir in Germany, the Netherlands and the southern North Sea. The deposits consist of aeolian dune sediments, intercalated fluvial, alluvial and wadi deposits. They exhibit a high degree of heterogeneity with respect to porosity, permeability and sediment composition. The aeolian dune and Interdune sandstones, locally interbedded with wadi and sabkha sediments are the prominent reservoir facies. Due to the heterogenic nature of the sediments and extensive diagenetic overprint during burial of up to 5000 m, these sandstones represent a tight gas reservoir characterized by permeabilities of less than 0.1 mD. This thesis focuses on sediments of the Dethlingen Formation, presenting a new characterization of permeability barriers and interbedded highly permeable zones. In order to observe the heterogeneity over a range of lenthscales, permeability barriers have been defined in core and correlated to log data on a large scale. Petrographic thin section analysis, Digital Image Analysis and high-resolution X-ray Microtomography were integrated to identify the barriers down to sub-millimetre scale. As the conventional interpretation of a well includes different types of data, e.g. geophysical logs, sedimentological core data, petrophysical data and results of thin section analysis, interpretation is mostly done using different software packages. In order to achieve a more integrated analysis of this data, relevant information has been collected and compiled so that different types of data can be examined, communicated and understood in an easier way. The dependence of petrophysical properties on rock fabric and pore parameters has been revealed using analysis of petrographic thin sections and Digital Image Analysis. Synsedimentary and early diagenetic processes influence the later diagenetic evolution during burial and exhumation. The distribution of clay minerals in the sediment has been recognized as the most significant process influencing quartz dissolution and quartz cementation therefore diagenetically altering the pre-existing aeolian pin-stripe lamination and determining fluid flow through the sediment.