Unconventional oil and gas potential of the Toarcian Posidonia Shale Formation in the crossjunction of Lower Saxony Basin, Pompeckj Block and Gifhorn Trough, Northern Germany: Implications from Organic Petrography, Geochemistry and 3D Numerical Basin Modelling Von der Fakultät für Georessourcen und Materialtechnik der Rheinisch-Westfälischen Technischen Hochschule Aachen zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von M.Sc. Alexander Thomas Stock aus Köln Berichter: Univ.-Prof. Dr. rer. nat. Ralf Littke Prof. Dr. Brian Horsfield Tag der mündlichen Prüfung: 05.Oktober 2017 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar II Acknowledgements I would like to express my utmost gratitude to Prof. Dr. Ralf Littke for enabling me to pursue a PhD in the field of Petroleum Geoscience at the Institute of Geology and Geochemistry of Petroleum and Coal at RWTH Aachen University. His tutelage and knowledge, combined with his outstanding support during my studies enabled me to persecute this degree, for which I am very grateful. Furthermore, I would like to express my gratitude towards Prof. Dr. Brian Horsfield for his work as a reviewer of this thesis and for enabling my research stay at the GFZ Potsdam. I am additionally very grateful for the help and support of Dr. Benjamin Bruns and Dr. Victoria Sachse, Dr. Daniel Mohnhoff, Dr. Alexej Merkel, Dr. Reinhard Fink and Dr. Arne Grobe, who helped with problems and questions regarding the various analytical techniques conducted within the scope of the thesis and who were always there for further fruitful discussions. Further gratitude is due for Donka Macherey, Annette Schneiderwind and Yvonne Esser for all the technical support and for tirelessly answering questions regarding the analytical methods. I would sincerely thank all my friends, colleagues and fellows during my stay at the Institute of Geology and Geochemistry of Petroleum and Coal who provided a wonderful work environment and inspired some of the best and funniest lunch break discussions. My deepest regards go to my family, especially my father and grandmother who provided support and encouragement during the creation of this thesis. III Abstract Petroleum production in Germany has a longstanding history that already started in the late 18th century in NW-Germany. Although petroleum production in Germany has rapidly declined from the early 1960’s onwards, there is still ongoing production in Germany. The production itself however faces strong challenges, as low oil prices due to a wealth of unconventional gas production in the US strongly influence the expensive domestic oil production in Germany. While the demand for petroleum and petroleum products is still high, conventional oil production in Germany declines, as known reservoirs are nearing the end of their lifecycle and further exploration efforts have been on a low level. The success of the unconventional oil and gas production, especially in the US, could act as an example in how to increase domestic production and to reduce the dependence on oil and gas imports. Although hydraulic fracturing, often a prerequisite for unconventional hydrocarbon production, is currently prohibited, an assessment of the theoretical potential and the location of so called “sweet-spots” can help in determining the suitability of the here chosen study area for conventional and unconventional petroleum potential, should the need for increasing domestic production or for reduced dependence on exporting countries arise. The chosen study area, a triple-junction of geological basin, namely the Pompeckj Block, the Lower-Saxony Basin and the Gifhorn Trough, located in NW-Germany, has been the target in past exploration and production efforts and still presents a major target in petroleum exploration and assessments for the future. The presence of Cretaceous (Wealden) and Jurassic (Posidonia Shale) marlstones and shales, as well as Carboniferous black shales and coals, acting as source rocks present within the basin systems, marks this area as a prominent oil and gas province. Especially the unconventional petroleum potential within the basin presents an up to date untapped resource that could be utilized, similar to the US shale gas boom, to increase the domestic production here in Germany. Current and past research on especially the Posidonia Shale in Germany have verified its suitability as a potential source rock in unconventional petroleum production due to its inherent type II hydrogen-rich kerogen, high TOC values and good thickness. To correctly assess the petroleum potential of the Posidonia Shale within the study area, this thesis studied its source rock characteristics, the oil properties of oils sourced by the Posidonia Shale and used 3D numerical basin modelling to illustrate its distribution and potential. Organic geochemical analysis and bulk geochemical analysis conducted on oil IV samples from locations within the eastern LSB, the Pompeckj Block and the Gifhorn Trough and on Posidonia Shale analogue samples certified the excellent quality of the oils, with API° values higher than 30° and confirmed that the oils present in the study area are mainly sourced from Posidonia Shale source rocks alone. There was no apparent contribution of the lacustrine Wealden Shales recognizable. In depth kerogen analysis, using a maturity series of kerogen concentrates from Posidonia Shale samples allowed for insights into the petroleum composition at different maturities along the natural maturation pathway, providing a better mode of prediction for cracking products at certain maturities. This, in combination with petroleum kinetics measurements, was used to calibrate and create a 3D numerical basin model of the area, utilizing a threefold division of the Posidonia Shale and predicting petroleum accumulations and volumes, within potential reservoirs and for the unconventional potential within the three lithologic source rock units. The results from the high resolution 3D numerical basin model indicate that different localities within the study area show different predispositions in their potential for oil and gas production. Based on their maturity assessment, gas potential is present in the Central LSB and parts of the Pompeckj Block, while higher oil potential can be found on the rims of the LSB, in the Gifhorn Trough and in larger parts of the Pompeckj Block. While large parts of the produced hydrocarbons have been expelled from the source rock lithology, especially large parts of gas can be still retained in the pore system as free gas and in an adsorbed phase. However, especially the free gas shows a strong dependence, similarly to oil, on the sealing capacity of the overlying strata. V Kurzfassung Die Erdölförderung in Deutschland hat eine weitreichende Geschichte, welche bereits im 18. Jahrhundert begonnen hat. Auch wenn die Erdölförderung in Deutschland seit den 1960ern rapide abnimmt, gibt es dennoch einen Anteil an heimischer Öl- und Gasförderung in Deutschland. Die deutsche Öl- und Gasförderung ist jedoch einigen Herausforderungen unterworfen, nicht zuletzt der hohe Preis einheimischer Förderung gepaart mit dem seit Ende 2015 geringen Ölpreis aufgrund von Überproduktion, nicht zuletzt wegen der unkonventionellen “Shale Gas” und „Shale Oil“ Förderung der USA. Zwar ist der Bedarf an Öl und Gas in Deutschland weiterhin hoch, die deutschen Produktionsmengen nehmen jedoch ab, auch auf Grund des Lebenszyklus von Erdöl- und Erdgas-Lagerstätten, von denen sich viele ältere Felder dem Ende der Produktion nähern. Witere Exploration in Deutschland trifft zum einen auf eine zunehmend kritische Wahrnehmung in der Öffentlichkeit, zum anderen sind die Produktionskosten relativ hoch. Der Erfolg der unkonventionellen Öl- und Gasproduktion in den USA kann hier als ein Beispiel dienen wie auch durch politischen Hilfe die einheimische Produktion wieder erhöht und gleichzeitig die Importabhängigkeit reduziert werden kann. Kritisch betrachtet wird vor allem die Technik des “Hydraulic Fracturing”, auch Fracking genannt, welche jedoch oft eine Voraussetzung für die unkonventionelle Förderung ist. Diese Studie soll dazu dienen, das theoretische Potential und die Lage von potentiellen Explorationszielen in NW-Deutschland zu erfassen, falls in näherer Zukunft ein erneutes Bestreben nach deutscher Erdöl- und Erdgas-Produktion besteht, auch um wirtschaftspolitisch unerwünschte Importabhängigkeiten zu reduzieren. Der ausgewählte Arbeitsbereich, welcher das Niedersächsische Becken, den Pompeckj Block und den Gifhorner Trog mit einschließt, ist bereits als eine der ertragreichsten Erdöl- und Erdgasprovinzen in Deutschland bekannt. Durch die Präsenz der Wealden-Shales (Kreide), des Posidonienschiefers (Jura) und von Karbonischen Schwarzschiefern und Kohlen, welche als Muttergesteine für Erdöl und Erdgas dienen können, ist diese Region eine der Kohlenwasserstoff-höffigsten in Deutschland. Da sich die Förderung in diesem Gebiet bisher primär auf konventionelles Erdöl- und Erdgas beschränkt hat, besteht hier auch ein riesiges Potential zur unkonventionellen Förderung. Besonders das Potential des Posidonienschiefers ist in rezenten Studien als exzellent ausgewiesen worden, vor allem da er ein VI wasserstoffreiches Typ-II Kerogen beinhaltet, bei hohen TOC-Werten und einer hohen Mächtigkeit. Um das Potential des Posidonienschiefers im Arbeitsbereich möglichst genau vorhersagen zu können, wurden im Verlauf dieser Arbeit dessen
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