The occurrence and characteristics of reservoir waters from the Silesian segment of the Rotliegend Basin (SW Poland)

Abstract

The paper considers the potential for new discoveries of gas accumulations in the Rotliegend Basin on the basis of the analysis of reservoir and hydrochemical tests and the results of reservoir simulations. Several reservoir simulations carried out in the study area (history of production and history matching) demonstrate the regional migration of reservoir waters. The integration of the simulations with mathematical calculations (in consistency with Hubbert’s theory) and with hydrochemical results permits recognition of the regional hydrodynamics and the potential localization of gas fields. In an analysis of the current hydrodynamic and hydrochemical conditions of reservoir waters in the Rotliegend (Lower Permian) strata, attention was focused on part of the sedimentary Rotliegend Basin, located south of the Wolsztyn-Pogorzela High, utilizing materials available from drilling and noting the differences between this area and the northern sub-basin. The current hydrogeological conditions and the dynamics of fluid transfer in the Rotliegend Basin are an effect of structural rearrangement during the Laramide orogeny. The basin hypsometry, resulting from the Laramide movements, became the decisive factor that controlled the filtration of groundwater. The recent hydrodynamic characteristics of migrating reservoir waters are reflected in the P-T (fluid pressure and temperature gradient) distribution pattern. Hence, the analysis of this distribution may reveal reactions that have taken place over time. It must be emphasized that clusters of gas fields are located in the zones occupied by stagnant groundwater (rNa/rCl<0.75) under hydrostatic (or slightly higher) pressure.