Ein Beitrag zur petrophysikalischen Evaluierung des Potentials unkonventioneller Lagerstätten in permischen Tonsteinen des Norddeutschen Beckens
Research output: Thesis › Master's Thesis
As part of the evaluation of the economic potential of unconventional natural gas reservoirs in the North German Basin a 7 m cored section of Permian Shales in depths of over 4400 m has been studied with the focus on petrophysics and mineralogy. A combination of X-Ray diffractometry, microscopy of thin sections and TOC determination by gamma radiation and LECO was used to resolve the mineralogy. These methods are highly complementary and allow a precise determination of the different minerals. The main minerals of the Permian Shales are α-quartz, feldspar (mainly plagioclase), calcite, muscovite/illite, chlorite, hematite, and in some samples anhydrite. Magnetite, goethite, limonite and rutile are accessory minerals. Due to the observed alteration processes of some iron minerals the environment was very likely oxygen-rich and the organic material was probably rapidly degraded. The high quartz content with over 60% is primarily responsible for the elastic parameters and the high brittleness of the formation. Although the Poisson's ratio is close to the typical cut-off value, the high empirical “Brittleness indices” are an indication for excellent conditions in order to efficiently stimulate the reservoir. The magnetic survey could not only aid in determining the contents of magnetite but also verify the low anisotropy of 2 to 7.5% from the ultrasonic measurement. The water saturated samples show probably because of the reaction with clays reduced elastic properties and behave slightly more ductile than the dried samples. Considering the performed measurements in this study to evaluate the potential, the following statements can be made. The permeability of 0.05 mD which is independent of the measuring direction and the “Brittleness indices” are definitely above the economic limitations. However, the average porosity of 0.8% using Archimedes principle is significantly below the required 4%. As there are no precise values for the TOC, the maturity, the gas content and the thickness as well as the spatial extent of the formation available, a final evaluation is not possible.
|Translated title of the contribution||A contribution to the petrophysical evaluation of the unconventional potential of Permian Shales in the North German Basin|
|Award date||28 Jun 2013|
|Publication status||Published - 2013|