Unconventional Gas Resources in the Paleozoic of Central Europe

Abstract

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.