Static 3D model of the Rotliegend deposits - case study from natural gas field area, Fore-Sudetic Monocline, Western Poland

The "Z" natural gas field is located in the southern part of the Fore-Sudetic Monocline, in the western part of Poland. Rotliegend sandstones, characterized by good reservoir properties are located in the Polish part of the Southern Permian Basin (Gast et al. 2010). The "Z" gas deposit was discovered in 1978. Reservoir "Z" structure is a regular, oval brachyanticline. The culminations are separated by a shallow depression in which the top of Rotliegend complex is located at depth somewhat less than - 1275 m bsl. Massive type accumulation covers about 25 km and shows a height up to about 105 m (Karnkowski 1999). 3D static modelling was performed using Petrel software from Schlumberger. Typical workflows for modelling of oil and gas reservoirs were applied (e.g. Zakrevsky 2011). Structural model was created by 100 m x 100 m grid increment. Ten proportional layers of reservoir zone were set resulting in model composed of over 1,000,000 cells. The base case model assumed gas/water contact at 1345 m bsl. These models were result of geostatistical simulation based on Kriging technique. The quality and number of the input data used to develop parametric models play a major role. The most important parameters characterizing the reservoir rocks are: porosity, permeability and shale volume (vshale). Average petrophysical parameters based on base case model in the area are: 15% for porosity, 45 mD for permeability and 14% for vshale. Performed structural-parametric models of the Żuchlów gas field can be successfully used for dynamic simulation and reserves estimation.