This article deals with the geological evolution of the Munsterland Basin, western Germany with special emphasis on the Carboniferous petroleum systems including their unconventional shale gas resources. The Carboniferous contains several black shales and many bituminous coal seams which are targets for shale gas and CBM (coalbed methane) exploration. A large set of maturity and calibration data was used to create the first 3D petroleum system model for this area providing depth-, temperature-, and maturity maps for different stratigraphic units and for different time steps. Based on maturity information and data on adsorption characteristics of one of the prominent gas shales, the Mississippian Upper Alum Shale ("Hangender Alaunschiefer"), we also calculated quantities of generated, expelled and adsorbed and free gas in a fully integrated numerical petroleum systems model.In part I of this article [1] we discussed the general model input, the calibration and the temperature and maturation history of the Westphalian succession.

This article deals with the geological evolution of the Munsterland Basin, western Germany with special emphasis on the Carboniferous, which reaches a thickness of more than 5 km in this area. Various data sets revealed the present-day geometry and were evaluated, corrected and compiled in order to construct a 3D model (PetroMod (R) suite software) for this region, extending about 152 km in east-west and 109 km in north-south direction. A large set of calibration data (mainly vitrinite reflectance, but also fission track data) was available as well but not homogeneously distributed, leading to varying degrees of uncertainty with respect to maturity of the Carboniferous. This study provides for the first time 3D modeling results such as paleo-temperature, and maturity maps for the Westphalian succession for different time steps. In Part II of this article we will discuss gas generation, sorption, and accumulation within one of the most important gas shales in northwest Europe, the Namurian Upper Alum Shale.

Different black shale sequences occurring in the Devonian and Mississippian at the northern margin of the Rhenish Massif and the Ardennes have not been considered economically interesting targets so far. Due to their high thermal maturity, all oil potential has been exhausted. Nevertheless, some of these shales are still within the gas window. Therefore, these sequences may well act as economically feasible gas shales in the future. To evaluate the shale gas potential, extensive measurements on these black shales have been performed, including mineralogical investigations, analysis of organic and inorganic geochemical composition, as well as vitrinite reflectance measurements. Next to gathering information on Devonian and early Mississippian black shale sequences, this study mainly focused on the marine, organic-rich “Hangende Alaunschiefer” (Upper Alum Shale) in Germany and the Belgian “Chokier Formation” of late Mississippian age. Results of these extensive measurements revealed that especially the properties of the Upper Alum Shale and the Chokier Formation are similar to producing gas shale formations in the USA. Therefore, these sequences may become an important target for future shale gas exploration in Europe.

Whereas gas production from unconventional reserves has greatly increased over the past decades, there is still a largely unexplored potential in the Paleozoic of Central Europe. For this area, the paper summarizes some important aspects of the geology of tight sandstone gas reservoirs, gas shales and coalbed methane. Tight sandstones with low permeabilities are especially present in the Permian (Rotliegend Formation) of The Netherlands and northern Germany, but also in the underlying Carboniferous. There is already active production from some of these reservoirs. Further development greatly depends on understanding of gas charge as well as the regional distribution of porosity and permeability which in turn depend on facies and diagenesis. In contrast exploration for gas shales is just at the very beginning. Whereas Mesozoic shales in the southern Lower Saxony Basin have to be regarded as prime targets due to thickness, maturity and organic matter content, there are additional targets in the Mississippian, but also in older rocks. Currently an international gas shale research programme (Gas shales in Europe, GASH) gathers relevant data for these units. Coalbed methane exploration started already about 20 years ago in the Ruhr Basin, but was not successful at that time due to small flow rates. On the other hand, production from abandoned coal mines provided substantial amounts of gas. Due to the abundance of coal seams and the suitable maturity conditions and gas contents, there is a high potential for future substantial coalbed methane in the area. Alors que l’extraction du gaz naturel des gisements non conventionnels a fortement augmenté ces dernières dizaines d’années, un large potentiel de ressources reste inexploré dans les couches paléozoïques de l’Europe Centrale. Cet article présente, pour cette région, quelques aspects importants de la géologie des grès de faible perméabilité (tight gas sands), des gaz de schiste (gas shales) et du gaz de houille (coalbed methane, CBM). Les grès de faible perméabilité se trouvent surtout parmi les couches permiennes (Rotliegend) aux Pays-Bas et dans le nord de l’Allemagne, mais aussi dans les couches du Carbonifère supérieur. La production est déjà active dans quelques-uns de ces réservoirs. Pour l’avenir, le développement dépendra principalement de l’amélioration de la compréhension du gaz en place et de la distribution régionale de la porosité et la perméabilité qui, d’ailleurs, dépendent du faciès lithologique et la diagénèse. La recherche de gaz dans les roches argileuses, par contre, vient juste de commencer. Les roches argileuses mésozoïques dans le sud du bassin de Basse-Saxe (Lower Saxony Basin) sont des objets d’exploration prioritaire à cause de leur épaisseur, de leur maturité et de leur teneur en matière organique. Mais il existe d’autres séries intéressantes dans le carbonifère inférieur et des couches plus anciennes. Actuellement, un projet de recherche international vise à acquérir des données géologiques sur ces systèmes. La recherche du gaz de houille (CBM) a commencé dans la bassin de la Ruhr il y a une vingtaine d’années, mais avec un succès très limité à cause de faibles débits de gaz. En revanche, le captage de grisou des mines de charbon abandonnées a fourni de considérables quantités de gaz. De par la multitude des filons houillers et des conditions de maturité et de teneurs en gaz favorables, il existe dans cette région un potentiel considérable de gaz de houille.

The evolution of the North German Basin is of particular interest due to the fact that it is an important hydrocarbon province with considerable reserves of natural gas. There have been several previous studies on the stratigraphy, structural evolution, and geochemical characterization of the basin, but no large-scale petroleum systems model has previously been published. We have developed a fully integrated numerical petroleum systems model, with emphasis on Palaeozoic pretroleum systems, taking into account the thermal subsidence history to calculate maturity levels, temperatures, and other related parameters. As one result of the study, we have produced maps of temperature and maturity for different time steps. We have also calculated the dynamics of gas generation and accumulation for different parts of the basin. This large-scale petroleum system model for the North German Basin can be applied in future exploration because it gives important clues concerning migration, accumulation, and escape of gas in the course of basin evolution.

Unconventional Gas Resources in the Paleozoic of Central Europe - Whereas gas production from unconventional reserves has greatly increased over the past decades, there is still a largely unexplored potential in the Paleozoic of Central Europe. For this area, the paper summarizes some important aspects of the geology of tight sandstone gas reservoirs, gas shales and coalbed methane. Tight sandstones with low permeabilities are especially present in the Permian (Rotliegend Formation) of The Netherlands and northern Germany, but also in the underlying Carboniferous. There is already active production from some of these reservoirs. Further development greatly depends on understanding of gas charge as well as the regional distribution of porosity and permeability which in turn depend on facies and diagenesis. In contrast exploration for gas shales is just at the very beginning. Whereas Mesozoic shales in the southern Lower Saxony Basin have to be regarded as prime targets due to thickness, maturity and organic matter content, there are additional targets in the Mississippian, but also in older rocks. Currently an international gas shale research programme (Gas shales in Europe. GASH) gathers relevant data for these units. Coalbed methane exploration started already about 20 years ago in the Ruhr Basin, but was not successful at that time due to small flow rates. On the other hand, production from abandoned coal mines provided substantial amounts of gas. Due to the abundance of coal seams and the suitable maturity conditions and gas contents, there is a high potential for future substantial coalbed methane in the area.

The presentation will deal with the evolution of the Central European Basin System (CEBS) with special emphasis to the Palaeozoic petroleum system. A large-scale dynamic 3D model (PetroMod® suite software)was built extending from Denmark to the midlands of Germany and from Netherlands to Poland. The presentation gives an overview on subsidence and sedimentation, uplift and erosion, temperature and maturity evolution in the CEBS.