caa a22 4500 606149147 CHVBK 20210128100532.0 cr unu---uuuuu 210128e20150901xx s 000 0 eng 10.1007/s00531-014-1081-y doi (NATIONALLICENCE)springer-10.1007/s00531-014-1081-y Predicted bulk composition of petroleum generated by Lower Cretaceous Wealden black shales, Lower Saxony Basin, Germany [Elektronische Daten] [Volker Ziegs, Nicolaj Mahlstedt, Benjamin Bruns, Brian Horsfield] The Berriasian Wealden Shale provides the favourable situation of possessing immature to overmature source rock intervals due to differential subsidence within the Lower Saxony Basin. Hydrocarbon generation kinetics and petroleum physical properties have been investigated on four immature Wealden Shale samples situated in different depth intervals and following the PhaseKinetics approach of di Primio and Horsfield (AAPG Bull 90(7):1031-1058, 2006). Kinetic parameters and phase prediction were applied to a thermally calibrated 1D model of the geodynamic evolution at the location of an overmature well. The immature source rocks of all depth intervals comprise kerogen type I being derived from the lacustrine algae Botryococcus braunii. Bulk kinetics of the lower three depth intervals (sample 2-4) can be described by one single activation energyE a, typical for homogeneous, lacustrine organic matter (OM), whereas sample 1 from the uppermost interval shows a slightly broader E a distribution which hints to a more heterogeneous, less stable OM, but still of lacustrine origin. Predicted physical properties of the generated petroleum fluids are characteristic of variably waxy, black oil possessing GOR's below 100Sm3/Sm3 and saturations pressures below 150bar. Petroleum fluids from the more heterogeneous OM-containing sample 1 can always be described by slightly higher values. Based on the occurrence of paraffinic, free hydrocarbons in the uppermost horizon of the overmature well and gas/condensate in the lower 3 depth intervals, two scenarios have been discussed. From the first and least realistic scenario assuming no expulsion from the source rock, it can be deduced that phase separation in the course of uplift can only have occurred in the uppermost interval containing the slightly less stable OM but not in the lower intervals being composed of a more stable OM. Therefore and taking secondary cracking into account, all depth intervals should contain gas/condensate. The free hydrocarbons in the upper horizon are interpreted as impregnation from migrated hydrocarbons. The second scenario assumes nearly complete expulsion due to fracturing by the so-called generation overpressure (Mann et al. in Petroleum and basin evolution. Springer, Berlin, 1997). The expelled petroleum might migrate into lower pressurised source rock horizons and reach bubble-point pressures leading to the exsolution of gas and "precipitation” of very high molecular weight bitumen unable to migrate. Subsequent burial of the latter in the course of the basin evolution would lead to secondary cracking and remaining pyrobitumen explaining the high amounts of pyrobitumen in the overmature well Ex-B and relatively enhanced TOC contents at such high maturity levels. The Author(s), 2014 Bulk kinetics nationallicence PhaseKinetics nationallicence Phase behaviour nationallicence Type I kerogen nationallicence Waxy oil nationallicence Lacustrine depositional environment nationallicence Unconventionals nationallicence Ziegs Volker Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut Mahlstedt Nicolaj Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut Bruns Benjamin Energy and Mineral Resources Group (EMR), Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstr. 4-20, 52056, Aachen, Germany aut Horsfield Brian Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut International Journal of Earth Sciences Springer Berlin Heidelberg 104/6(2015-09-01), 1605-1621 1437-3254 104:6<1605 2015 104 531 https://doi.org/10.1007/s00531-014-1081-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00531-014-1081-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ziegs Volker Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut NATIONALLICENCE 700 1- Mahlstedt Nicolaj Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut NATIONALLICENCE 700 1- Bruns Benjamin Energy and Mineral Resources Group (EMR), Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstr. 4-20, 52056, Aachen, Germany aut NATIONALLICENCE 700 1- Horsfield Brian Section4.3: Organic Geochemistry, Helmholtz Centre, GFZ German Centre for Geosciences Potsdam, 14473, Telegrafenberg, Potsdam, Germany aut NATIONALLICENCE 773 0- International Journal of Earth Sciences Springer Berlin Heidelberg 104/6(2015-09-01), 1605-1621 1437-3254 104:6<1605 2015 104 531