HU - Hydrogeology and Environment

Journal of the Dept. of Hydrogeology and Environment, University of Würzburg (ISSN 09309-3757)

Editorial office: BGI, Greisingstr. 8, 97074 Würzburg, GERMANY

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Vol. 11 (1996)



Abstract



Vol. 11: 

Porenraumuntersuchungen ausgewählter Rotliegend Sandsteinproben Norddeutschlands unter besonderer Berücksichtigung der Porengeometrie.

[The Pore Geometry of Rotliegend Sandstones from Northern Germany]

Claudia Bärle


Abstract:
The influence of facies and diagenesis on pore geometry was examined using Rotliegend sandstone samples. For a core sample from a Rotliegend gas reservoir and samples out of the Flechtinger Höhenzug complete data files were established, each describing different aspects of the pore space composition.
Individual pore data (diameter, perimeter, form factor etc.) were obtained from specially prepared thin section sequence with the aid of an image analysis system, using a computer program VIDS V. The image analysis is primarily statistical in nature, with a vast quantity of numerical pore space information to be processed.
The geometrical analysis of spatial pore configurations has shown definite characteristic maxima within the frequency distributions, although the complete range of pore geometries is present in both materials. These maxima do not concentrate one specific numerical value, instead they include a certain range of data, indicating that a dominant size and shape spectrum is present. The "average pore" of the reservoir rock has got an area of 0-200 µm², a diameter of 40-60 µm, a perimeter of 50-150 µm and a length of greatest extension of 10-70 µm. In the rock sample "Flechtingen" pore areas of 0-150 µm², diameters of 0-20 µm, perimeters of 50-125 µm and length of greatest extensions of 40-60 µm dominate. Since both samples have got numerically different maxima the data is lithologically specific. Even with a great variety of sizes, arrangements and connections within the pore spaces, the composition of the pore system obeys certain statistically descriptive laws.
Both samples had similar sedimentary and environmental origins, differences in the diagenesis however are responsible for the divergent pore systems. Diagenesis is therefore the dominant pore system forming element. Using a medical research method known from the analysis of organ structure through elaboration of Cad-Program enhanced sequential photographs, a three-dimensional pore network model was constructed in order to demonstrate the statistic information and to illustrate the differences in the pore system composition. The result is a model of a multi-layered and complex reservoir rock with layer-specific productivity in contrast to a sandstone with reduced, homogenous pore system predominantly used in construction.
Further information about microporosity, pore throat distribution and geophysical parameters was determined by use of SEM-analysis and Hg-penetration tests.

Paper language: german; german abstract





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