The Lower Saxony Basin (LSB) in northwest Germany is one of the oldest oil-producing basins in the world, where the first production well was drilled in 1864. It has been intensively investigated with respect to its hydrocarbon potential and can be regarded as a well-studied example of a sedimentary basin that experienced strong inversion and uplift. Oil and gas source rocks of economic importance include Upper Carboniferous coals as well as Jurassic (Toarcian Posidonia Shale) and Cretaceous (Berriasian/Wealden) shales. We have developed a fully integrated 3D high-resolution numerical petroleum systems model incorporating the LSB, and parts of the Pompeckj Block in the north as well as the Münsterland Basin in the south. Aside from temperature and maturity modeling calibrated by a large amount of vitrinite reflectance and downhole temperature data, we also investigated petroleum generation and accumulation with special emphasis on the shale gas potential of the Jurassic Posidonia Shale.