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  • Nature Research  (6)
  • American Association of Petroleum Geologists  (3)
  • 1
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    Importance of evolving fault seals on petroleum systems: Southern Halten Terrace, Norwegian Sea (2018)
    American Association of Petroleum Geologists
    In:  AAPG Bulletin, 102 (4). pp. 671-689.
    Details
    Publication Date: 2021-02-08
    Description: The role of faults in petroleum systems is important especially in cases where the hydrocarbon accumulation in the prospect or field is fault-dependent. Usually, the properties of faults in petroleum systems are considered as static through time. We present a case study from the southern Halten terrace in the Norwegian Sea which highlights not only the importance of faults but also that the evolution of fault properties is key in determining the correct charge in the fields in the region. The best-fit model shows that in order to match observations the petroleum system requires at least two stages of hydrocarbon migration during which fault properties change from partially to completely sealing with respect to hydrocarbon flow across them. The most likely process that results in fault sealing is cementation due to increasing temperatures caused by the rapid burial during the Quaternary glaciations. This results in the most accurate charge of accumulations in the region while also explaining other observations such as present-day pressure compartmentalization and biodegradation. The best-fit model also implements the source rock thermal evolution based on a 2D basin model that improves the match of fluid GOR in the accumulation to the measured values. This study highlights the importance of multi-scale, multi-physics and multi-stage models in order to obtain results consistent with present day observations.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1306/0208171616417017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Sea level fall during glaciation stabilized atmospheric CO2 by enhanced volcanic degassing (2017)
    Nature Research
    In:  Nature Communications, 8 (15867).
    Details
    Publication Date: 2020-06-18
    Description: Paleo-climate records and geodynamic modelling indicate the existence of complex interactions between glacial sea level changes, volcanic degassing and atmospheric CO2, which may have modulated the climate system's descent into the last ice age. Between ∼85 and 70 kyr ago, during an interval of decreasing axial tilt, the orbital component in global temperature records gradually declined, while atmospheric CO2, instead of continuing its long-term correlation with Antarctic temperature, remained relatively stable. Here, based on novel global geodynamic models and the joint interpretation of paleo-proxy data as well as biogeochemical simulations, we show that a sea level fall in this interval caused enhanced pressure-release melting in the uppermost mantle, which may have induced a surge in magma and CO2 fluxes from mid-ocean ridges and oceanic hotspot volcanoes. Our results reveal a hitherto unrecognized negative feedback between glaciation and atmospheric CO2 predominantly controlled by marine volcanism on multi-millennial timescales of ∼5,000-15,000 years.
    Type: Article , PeerReviewed
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    DOI: 10.1038/ncomms15867
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Glacigenic sedimentation pulses triggered post-glacial gas hydrate dissociation (2018)
    Nature Research
    In:  Nature Communications, 9 (Article number 635).
    Details
    Publication Date: 2021-02-08
    Description: Large amounts of methane are stored in continental margins as gas hydrates. They are stable under high pressure and low temperature, but react sensitively to environmental changes. Bottom water temperature and sea level changes were considered as main contributors to gas hydrate dynamics after the last glaciation. However, here we show with numerical simulations that pulses of increased sedimentation dominantly controlled hydrate stability during the end of the last glaciation offshore mid-Norway. Sedimentation pulses triggered widespread gas hydrate dissociation and explains the formation of ubiquitous blowout pipes in water depths of 600 to 800 m. Maximum gas hydrate dissociation correlates spatially and temporally with the formation or reactivation of pockmarks, which is constrained by radiocarbon dating of Isorropodon nyeggaensis bivalve shells. Our results highlight that rapid changes of sedimentation can have a strong impact on gas hydrate systems affecting fluid flow and gas seepage activity, slope stability and the carbon cycle.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1038/s41467-018-03043-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Submarine slope failures due to pipe structure formation (2018)
    Nature Research
    In:  Nature Communications, 9 (Art.No. 715).
    Details
    Publication Date: 2021-03-19
    Description: There is a strong spatial correlation between submarine slope failures and the occurrence of gas hydrates. This has been attributed to the dynamic nature of gas hydrate systems and the potential reduction of slope stability due to bottom water warming or sea level drop. However, 30 years of research into this process found no solid supporting evidence. Here we present new reflection seismic data from the Arctic Ocean and numerical modelling results supporting a different link between hydrates and slope stability. Hydrates reduce sediment permeability and cause build-up of overpressure at the base of the gas hydrate stability zone. Resulting hydro-fracturing forms pipe structures as pathways for overpressured fluids to migrate upward. Where these pipe structures reach shallow permeable beds, this overpressure transfers laterally and destabilises the slope. This process reconciles the spatial correlation of submarine landslides and gas hydrate, and it is independent of environmental change and water depth.
    Type: Article , PeerReviewed
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    DOI: 10.1038/s41467-018-03176-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Melt-induced buoyancy may explain the elevated rift-rapid sag paradox during breakup of continental plates (2018)
    Nature Research
    In:  Scientific Reports, 8 . Art.Nr. 9985.
    Details
    Publication Date: 2021-03-19
    Description: The division of the earth’s surface into continents and oceans is a consequence of plate tectonics but a geological paradox exists at continent-ocean boundaries. Continental plate is thicker and lighter than oceanic plate, floating higher on the mantle asthenosphere, but it can rift apart by thinning and heating to form new oceans. In theory, continental plate subsides in proportion to the amount it is thinned and subsequently by the rate it cools down. However, seismic and borehole data from continental margins like the Atlantic show that the upper surface of many plates remains close to sea-level during rifting, inconsistent with its thickness, and subsides after breakup more rapidly than cooling predicts. Here we use numerical models to investigate the origin and nature of this puzzling behaviour with data from the Kwanza Basin, offshore Angola. We explore an idea where the continental plate is made increasingly buoyant during rifting by melt produced and trapped in the asthenosphere. Using finite element simulation, we demonstrate that partially molten asthenosphere combined with other mantle processes can counteract the subsidence effect of thinning plate, keeping it elevated by 2-3 km until breakup. Rapid subsidence occurs after breakup when melt is lost to the embryonic ocean ridge.
    Type: Article , PeerReviewed
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    DOI: 10.1038/s41598-018-27981-2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Automated thermotectonostratigraphic basin reconstruction: Viking Graben case study (2008)
    American Association of Petroleum Geologists
    In:  AAPG Bulletin, 92 (3). pp. 309-326.
    Details
    Publication Date: 2019-09-23
    Description: We present a generic algorithm for automating sedimentary basin reconstruction. Automation is achieved through the coupling of a two-dimensional thermotectonostratigraphic forward model to an inverse scheme that updates the model parameters until the input stratigraphy is fitted to a desired accuracy. The forward model solves for lithospheric thinning, flexural isostasy, sediment deposition, and transient heat flow. The inverse model updates the crustal- and mantle-thinning factors and paleowater depth. Both models combined allow for automated forward modeling of the structural and thermal evolution of extensional sedimentary basins. The potential and robustness of this method is demonstrated through a reconstruction case study of the northern Viking Graben in the North Sea. This reconstruction fits present stratigraphy, borehole temperatures, vitrinite reflectance data, and paleowater depth. The predictive power of the model is illustrated through the successful identification of possible targets along the transect, where the principal source rocks are in the oil and gas windows. These locations coincide well with known oil and gas occurrences. The key benefits of the presented algorithm are as follows: (1) only standard input data are required, (2) crustal- and mantle-thinning factors and paleowater depth are automatically computed, and (3) sedimentary basin reconstruction is greatly facilitated and can thus be more easily integrated into basin analysis and exploration risk assessment.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1306/11140707009
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Interrelation between surface and basement heat flow in sedimentary basins (2017)
    American Association of Petroleum Geologists
    In:  AAPG Bulletin, 101 (10). pp. 1697-1713.
    Details
    Publication Date: 2020-02-06
    Description: Petroleum system models (PSM) result critically depend on the computed evolution of the temperature field. As PSM typically only resolve the sedimentary basin and not the entire lithosphere, it is necessary to apply a basement heat flow boundary condition inferred from well data, surface heat flow measurements, and an assumed tectonic scenario. The purpose of this paper is to assess the use of surface heat flow measurements to calibrate basin models. We show that a simple relationship between surface and basement heat flow only exists in thermal steady-state and that transient processes such as rifting and sediment deposition will lead to a decoupling. We study this relationship in extensional sedimentary basins with a 1D lithosphere-scale finite element model. The numerical model was built to capture the large-scale dynamic evolution of the lithosphere and simultaneously solve for transient thermal processes in basin evolution, such as sedimentation, compaction-driven fluid flow, and seafloor temperature variations. Our analysis shows that several corrections need to be applied when using surface heat flow information for the calibration of basement heat flow in PSM. Not doing so can lead to significant errors of up to 30-50 °C at typical petroleum reservoir and source rock depths. We further show that resolving sediment blanketing effects in basin modeling is crucial, with the thermal impact of sediment deposition being at least as important as rifting-induced basement heat flow variations.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1306/12051615176
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Detachment-parallel recharge explains high discharge fluxes at the TAG hydrothermal field (2021)
    Nature Research
    In:  (Submitted) Research Square preprint deposition service .
    Details
    Publication Date: 2021-12-13
    Description: Submarine massive sulfide deposits on slow-spreading ridges are larger and longer-lived than deposits at fast-spreading ridges 1,2 , likely due to more pronounced tectonic faulting creating stable preferential fluid pathways 3,4 . The TAG hydrothermal mound at 26°N on the Mid-Atlantic Ridge (MAR) is a typical example located on the hanging wall of a detachment fault 5-7 . It has formed through distinct phases of high-temperature fluid discharge lasting 10s to 100s of years throughout at least the last 50,000 years 8 and is one of the largest sulfide accumulations on the MAR. Yet, the mechanisms that control the episodic behavior, keep the fluid pathways intact, and sustain the observed high heat fluxes of up to 1800 MW 9 remain poorly understood. Previous concepts involved long-distance channelized high-temperature fluid upflow along the detachment 5,10 but that circulation mode is thermodynamically unfavorable 11 and incompatible with TAG's high discharge fluxes. Here, based on the joint interpretation of hydrothermal flow observations and 3-D flow modeling, we show that the TAG system can be explained by episodic magmatic intrusions into the footwall of a highly permeable detachment surface. These intrusions drive episodes of hydrothermal activity with sub-vertical discharge and recharge along the detachment. This revised flow regime reconciles problematic aspects of previously inferred circulation patterns and can be used as guidance to one critical combination of parameters that can generate substantive mineral systems.
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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    DOI: 10.21203/rs.3.rs-1030743/v1
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    OceanRep: Article in a Scientific Journal - without review
  • 9
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    Extensional tectonics and two-stage crustal accretion at oceanic transform faults (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Oceanic transform faults are seismically and tectonically active plate boundaries1 that leave scars—known as fracture zones—on oceanic plates that can cross entire ocean basins2. Current descriptions of plate tectonics assume transform faults to be conservative two-dimensional strike–slip boundaries1,3, at which lithosphere is neither created nor destroyed and along which the lithosphere cools and deepens as a function of the age of the plate4. However, a recent compilation of high-resolution multibeam bathymetric data from 41 oceanic transform faults and their associated fracture zones that covers all possible spreading rates shows that this assumption is incorrect. Here we show that the seafloor along transform faults is systemically deeper (by up to 1.6 kilometres) than their associated fracture zones, in contrast to expectations based on plate-cooling arguments. Accretion at intersections between oceanic ridges and transform faults seems to be strongly asymmetric: the outside corners of the intersections show shallower relief and more extensive magmatism, whereas the inside corners have deep nodal basins and seem to be magmatically starved. Three-dimensional viscoplastic numerical models show that plastic-shear failure within the deformation zone around the transform fault results in the plate boundary experiencing increasingly oblique shear at increasing depths below the seafloor. This results in extension around the inside corner, which thins the crust and lithosphere at the transform fault and is linked to deepening of the seafloor along the transform fault. Bathymetric data suggest that the thinned transform-fault crust is augmented by a second stage of magmatism as the transform fault intersects the opposing ridge axis. This makes accretion at transform-fault systems a two-stage process, fundamentally different from accretion elsewhere along mid-ocean ridges.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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