Source rocks of the German Central Graben

Müller, Simon; Arfai, Jashar; Jähne‐Klingberg, Fabian; Bense, Frithjof; Weniger, Philipp

doi:10.1016/j.marpetgeo.2019.104120

Cited by 8 publications

(9 citation statements)

References 33 publications

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“…The Figge Maar is located in the southeastern part of the North Sea and it is part of the Southern Permian Basin, which is a hydrocarbon province extending from the United Kingdom to the central Baltic Sea (e.g., Glennie and Provan, 1990;Ziegler, 1990;Breunese et al, 2010). Halokinesis of Upper Permian Zechstein evaporites was key for the creation of most hydrocarbon reservoirs by forming traps in post-Permian strata or directly sealing Lower Permian Rotliegend reservoirs (Glennie and Provan, 1990;Grassmann et al, 2005;Breunese et al, 2010;Harding and Huuse, 2015;Müller et al, 2020). In the study area, the transition from the Upper Permian Zechstein to the Lower Triassic Buntsandstein is associated with a marked change in sedimentary facies.…”

Section: Geological Backgroundmentioning

confidence: 88%

Formation of the Figge Maar Seafloor Crater During the 1964 B1 Blowout in the German North Sea

Karstens

Deimling²,

Berndt

et al. 2022

Earth Sci. Syst. Soc.

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In 1964, exploration drilling in the German Sector of the North Sea hit a gas pocket at ∼2900 m depth below the seafloor and triggered a blowout, which formed a 550 m-wide and up to 38 m deep seafloor crater now known as Figge Maar. Although seafloor craters formed by fluid flow are very common structures, little is known about their formation dynamics. Here, we present 2D reflection seismic, sediment echosounder, and multibeam echosounder data from three geoscientific surveys of the Figge Maar blowout crater, which are used to reconstruct its formation. Reflection seismic data support a scenario in which overpressured gas ascended first through the lower part of the borehole and then migrated along steeply inclined strata and faults towards the seafloor. The focused discharge of gas at the seafloor removed up to 4.8 Mt of sediments in the following weeks of vigorous venting. Eyewitness accounts document that the initial phase of crater formation was characterized by the eruptive expulsion of fluids and sediments cutting deep into the substrate. This was followed by a prolonged phase of sediment fluidization and redistribution widening the crater. After fluid discharge ceased, the Figge Maar acted as a sediment trap reducing the crater depth to ∼12 m relative to the surrounding seafloor in 2018, which corresponds to an average sedimentation rate of ∼22,000 m3/yr between 1995 and 2018. Hydroacoustic and geochemical data indicate that the Figge Maar nowadays emits primarily biogenic methane, predominantly during low tide. The formation of Figge Maar illustrates hazards related to the formation of secondary fluid pathways, which can bypass safety measures at the wellhead and are thus difficult to control.

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Section: Geological Backgroundmentioning

confidence: 88%

Formation of the Figge Maar Seafloor Crater During the 1964 B1 Blowout in the German North Sea

Karstens

Deimling²,

Berndt

et al. 2022

Earth Sci. Syst. Soc.

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“…Absence or thinning of the Altena Group is the result of later erosion due to the emergence of the Mid North Sea Dome, the rise of salt structures or Cretaceous structural inversion. Proven occurrences of the Posidonia Shale Formation are described from the northern Dutch Central Graben, whereas the presence of the Posidonia Shale Formation is assumed for the southern part of the German Central Graben (Müller et al, 2020). There are no obvious indications for the diapirism and the development of basins related to diapiric growth in the German part of the Central Graben before Mid-Jurassic.…”

Section: Seismic Interpretation and Griddingmentioning

confidence: 99%

“…It is assumed that some of the locally present hydrocarbons originate from secondary Jurassic source rocks, e.g. Lower Jurassic marine claystones from the Aalburg Formation and Middle Jurassic coals from the Central Graben Subgroup (De Jager & Geluk, 2007;Wong, 2007;Müller et al, 2020). Middle Jurassic sandstones of the Central Graben Subgroup also constitute reservoir rocks, e.g.…”

Section: Introductionmentioning

confidence: 99%

Jurassic to Lower Cretaceous tectonostratigraphy of the German Central Graben, southern North Sea

Müller

Jähne‐Klingberg

Thöle

et al. 2023

Netherlands Journal of Geosciences

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The Central Graben is a Mesozoic sedimentary basin that is significantly influenced by rift and salt tectonics. Its southern part is located in the German and Dutch sectors of the North Sea. Even though studies exist on the tectonic and stratigraphic development of the Danish and Dutch Central Graben, the German Central Graben as an important link is less investigated. We aim to fill this gap and to investigate the sedimentary development from the Latest Triassic to the Early Cretaceous, the relative influence of salt and rift tectonics on subsidence and how our results fit into the existing studies of the Danish and Dutch Central Graben. Knowledge of the development of the graben and its sedimentation is critical for any possible economic use like hydrocarbon exploitation or carbon capture and storage. Therefore, we mapped nine laterally traceable horizons on 2D and 3D reflection seismic data from the Lower Jurassic to the Lower Cretaceous within the German Central Graben and adjacent Danish Salt Dome Province as well as the northern Dutch Central Graben. These horizons include the base horizons of four tectonostratigraphic mega-sequences of the southern Central Graben adopted from the current Dutch tectonostratigraphic concept. Based on the mapping results, we constructed subsidence, thickness and erosion maps of the tectonostratigraphic mega-sequences and their subdivisions. The tectonostratigraphic mega-sequences were then correlated with well logs to determine the lithology. The results show that the structural and stratigraphic architecture of the German Central Graben was consecutively dominated by either subsidence controlled by rifting, salt tectonics or by thermal uplift and subsidence. We suggest that the German Central Graben is divided by a large strike-slip fault zone, the Mid Central Graben Transverse Zone, into a northern part that geologically rather belongs to the Danish and a southern part that rather belongs to the Dutch Central Graben. We discuss how this division and the tectonics influenced the regional lithology.

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“…As pointed out, it is unlikely that the studied sediment column is currently charged with thermogenic gas even though it cannot be excluded from the geochemical data that part of the gas stems from an underlying oil-mature source rocks (e.g. the Kimmeridge clay; Müller et al, 2020). Another option would be that the gas was desorbed from charcoal, which is known to occur in basal peats at "Doggerland" (Krüger et al, 2017).…”

Section: Modern Biogeochemical Processes In Peat-rich Sediments In Th...mentioning

confidence: 99%

Biomarker insights into a methane-enriched Holocene peat-setting from “Doggerland” (central North Sea)

et al. 2022

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Peats formed widespread early after the Last Glacial Maximum around the coast of the Dogger Bank, the central high of the now flooded “Doggerland” (central North Sea). Here we present biomarker and gas geochemical insights into near-surface peat cored at 43 m water depth. Based on their probable age of ~10 ka before present (BP), the peats are likely part of the so-called basal Holocene peats. Pore waters in the samples document slight methane enrichments in peat layers (up to 250 nM methane vs 60 nM above the peat layer) and δ13C-values of methane ranging between ca. −46‰ and −60‰ PDB. Ethane, propane, and n-butane were also found and may either document upward migration of thermogenic hydrocarbons in the past or, more likely, peat-specific gases, which is indicated by accompanying abundant unsaturated analogs (i.e. ethene and propene). High concentrations of elemental sulfur (up to 19 wt.%) and sulfur-specific transformation products of plant triterpenoids (Des-A-triterpenoids) point to microbial generation during and/or slightly after peat-formation as hydrocarbon source. Biomarkers indicated that peats were formed in a variable environment with high contributions from higher plant wax material. However, a C20 highly branched isoprenoid (HBI) likely records abundant diatoms typical of an oligotrophic lake environment. In addition, all samples contained a suite of bacterial hopenes and fernenes (hop-17(21)-ene, diploptene, fern-7(8)-ene). A strongly fluctuating methane-flux and/or -turnover during peat formation is recorded in partially high 13C-depletions of <−60‰ PDB of these biomarkers. This underlines the importance of peat layers for methane generation and consumption on “Doggerland” during the Holocene.

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Source rocks of the German Central Graben

Cited by 8 publications

References 33 publications

Formation of the Figge Maar Seafloor Crater During the 1964 B1 Blowout in the German North Sea

Formation of the Figge Maar Seafloor Crater During the 1964 B1 Blowout in the German North Sea

Jurassic to Lower Cretaceous tectonostratigraphy of the German Central Graben, southern North Sea

Biomarker insights into a methane-enriched Holocene peat-setting from “Doggerland” (central North Sea)

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