Structural evolution, temperature and maturity of sedimentary rocks in the Netherlands : results of combined structural and thermal 2D modeling

Sedimentary basins in the Netherlands contain significant amounts of hydrocarbon resources, which developed in response to temperature and pressure history during Mesozoic and Cenozoic times. Quantification and modeling of burial, maturity and temperature histories creates a better understanding of the general geological evolution as well as petroleum generation. Structural modeling combined with basin modeling was used to demonstrate the influence of the structural history on petroleum plays and systems. For this purpose, a tectonic setting in the Netherlands was selected that shows large-scale tectonic inversion, associated erosion, and later subsidence. In this setting 31 deep wells along a 300 km long 2D section, that crosses the main tectonic features, were selected for a 1D and 2D basin modeling study. New vitrinite reflectance values were obtained and existing data re-evaluated to gain a good data base. On the basis of the 2D section, a structural model consisting of 21 paleo sections was created, covering a time span from the Late Carboniferous to present-day. All major basins in The Netherlands encountered at least one time of uplift or inversion and thus moderate to high amounts of erosion. The Permo-Triassic subsidence phase can be recognized in all basins, but with varying intensity. In the Jurassic, the basins experienced different relative movements that culminated in the Cretaceous when the influence of the inversion caused erosion of partially all of the Mesozoic succession. In order to determine the amount of inversion the basins have experienced, a 1D study was performed on the wells along the section. The burial histories are presented here to demonstrate the differences in basin evolution that led to their present shape and petroleum potential. The structural model was used to quantify the amount of erosion in between the wells or where the data from the wells was not informative (e.g., deepest burial at present-day). The results generated by the structural model agree with the 1D models in that the Late Cretaceous inversion affected the basins the most. Furthermore, according to the model the erosion in the Jurassic had the strongest influence on the structural highs. Using the structural model as input for the 2D basin model allowed the temperature and maturity of the sediments to be calculated. A temperature profile at 2000 m depth along the section shows that the present-day temperature distribution is also strongly influenced by the inversion. In the inverted basins, highly conductive layers such as overcompacted sediments or salt are closer to the surface, which results in temperatures above these layers being higher than in the non-inverted areas at similar depths. Eventually, the timing of hydrocarbon generation was found to be related to the structural history of the source rock within the basin. In strongly inverted parts of the basin, present-day burial is not sufficient to restart hydrocarbon generation, but in less inverted parts, hydrocarbon generation resumed during Tertiary times