Petroleum system evolution in the inverted Lower Saxony Basin, northwest Germany: a 3D basin modeling study

Abstract

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 M€ unsterland 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.

Predicted bulk composition of petroleum generated by Lower Cretaceous Wealden black shales, Lower Saxony Basin, Germany

“…The evolution of the LSB has been unravelled by Petmecky et al (1999), Bruns et al (2013b) and selected references therein. Of note to the current article was the rapid subsidence starting at Kimmeridgian (Upper Jurassic) times and reaching its maximum burial depth during Upper Cretaceous times (Petmecky et al 1999).…”

“…The following structural inversion of the basin in the Late Cretaceous was most intensive in the former basin centre and led to uplift and erosion of large amounts of Cretaceous and locally older strata of up to 6,700 m ( Fig. 1) (Bruns et al 2013b). The transition from Late Jurassic to Early Cretaceous times was dominated by a regression causing an isolation of sedimentary basins throughout northern Europe (Mutterlose and Bornemann 2000).…”

“…Rippen et al (2013) employed geochemical and petrographical methods to determine the maturity, organofacies and depositional environment of Wealden Shale samples stemming from these wells, and Bruns et al (2013b) included some of that geochemical data in a 3D basin model of the LSB reconstructing the geodynamic basin evolution. Here, we extend our understanding of the Wealden's source rock properties by predicting the bulk composition of the petroleum it generates as a function of thermal maturity level for each of the major organofacies it displays.…”

“…The PhaseKinetics approach (di Primio and Horsfield 2006) has been utilised to embed PVT predictive properties in a compositional kinetics matrix. To assist in our analysis, bulk kinetic parameters have been integrated into a 1D model for a mature well (Bruns et al 2013b and Fig. 1) and the derived phase states compared with the present-day composition of the free hydrocarbons (HC) in a thermally mature well in the LSB (Rippen et al 2013).…”

A new stylolite classification scheme to estimate compaction and local permeability variations

“…Assuming that 518 the other non--linearly growing stylolites show a similar dissolution, the 519 compaction estimates are 25.43 and 39.15% for the two cores (with an average 520 of 34.04% for both cores). If one compares the chemical compaction estimate at 521 stylolites with the initial porosity estimates of the Zechstein carbonates of up to 522 42% (Bruns et al, 2013), these values indicate that dissolution at stylolites is the 523 dominant compaction process in these rocks. In addition these values indicate 524 that material that dissolves at stylolites does not have to leave the system but 525 can fill pore space.…”