Quaternary and Neogene Reservoirs of the Norwegian Continental Shelf and the Faroe-Shetland Basin

Glaciogenic reservoirs host important hydrocarbon resources across the globe. Examples such as the Peon and Aviat discoveries in the North Sea show that Quaternary and Neogene reservoirs can be prospective in the region. In this study, we interpret 2D and 3D reflection seismic data combined with borehole information to document unconventional play models from the shallow subsurface of the Norwegian Continental Shelf and the Faroe-Shetland Basin. These plays include (i) glacial sands in ice-marginal outwash fans, sealed by stiff subglacial tills (the Peon discovery), (ii) meltwater turbidites, (iii) contouritic fine-grained glacimarine sands sealed by gas hydrates, (iv) remobilized oozes above large evacuation craters which are sealed by megaslides and glacial muds, and (v) Neogene sand injectites. The hydrocarbon reservoirs are characterized by negative-polarity reflections with anomalously high amplitudes in the reflection seismic data as well as density and velocity decreases in the borehole data. Extensive new 3D reflection seismic data are crucial to correctly interpret glacial processes and distinguish shallow reservoirs from shallow seals. These data document a variety of play models with the potential for gas in large quantities and enable the identification of optimal drilling targets at stratigraphic levels which have so far been overlooked

Quantification and restoration of the pre‐drift extension across the NE Atlantic conjugate margins during the mid‐Permian‐early Cenozoic multi‐rifting phases

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Characterizing ancient and modern hydrothermal venting systems

Highlights • Ancient and modern hydrothermal venting systems occur offshore mid-Norway and Java. • They can share morphologies, eruptive behavior and develop similarly. • Modern hydrothermal venting systems are relevant analogues for ancient systems. Abstract Ancient hydrothermal vent complexes have released large volumes of greenhouse gases in the past causing global warming, and similar modern vent structures are potential geohazards. In the NE Atlantic, thousands of hydrothermal vent complexes were formed during the Paleocene-Eocene Thermal Maximum. In Java, Indonesia, the erupting Lusi sediment-hosted geothermal system caused the displacement of 40,000 people. In order to determine how ancient and modern hydrothermal venting systems are related, we map a well-defined buried hydrothermal vent complex offshore mid-Norway using 3D seismic reflection data and then compare it to the active Lusi eruption (since 2006) and the neighboring inactive Porong Structure. These are characterized using 2D seismic reflection data, borehole data and field observations. The venting structures are subcircular in plan-view and a few kilometers in diameter. They are funnel-shaped in profiles, with inward-dipping beds surrounding the conduits. The hydrothermal vent complex offshore mid-Norway reveals five seismically-distinct vent fill facies units. Importantly, two of the facies units are separated by an angular unconformity, clearly indicating that the depositional events within the vent fill were distinct. Hydrothermal fluids are interpreted to have led to the fluidization of mud-rich sediments which were erupted and deposited in and around the vent complex. Interpretation of a seismically transparent body along the conduit of the Norwegian venting structure, and the abrupt widening of the conduit at the Porong Structure, are interpreted to be caused by changes in fluid-flow dynamics as the fluids rise and get released from the host-rock. The hydrothermal venting systems in Java and offshore mid-Norway are found to be morphologically similar and are interpreted to form as the result of the transport and eruption of fluidized sediments

Regional Structure and Basin Development of the mid-Norwegian Volcanic Passive Margin: Anatomy of a Polyphased Rifted System

The interior of the Norwegian Sea, or in the regional geological nomenclature “mid-Norwegian passive margin”, contains of about 20% of total oil and gas resources of the Norwegian Continental Shelf. However, the significant potential for additional resources remains hidden in the deep outer parts of the shelf. An extensive data acquisition campaign during last 15 years brings new knowledge regarding the entire mid-Norwegian margin and its outer part in particular. New 2D and 3D seismic surveys, potential field data, as well as new wells are now available for interpretation. This PhD study aimed to compile and jointly interpret this extensive and contemporary dataset to refine timing of tectonic events in the area, configuration and properties of the crust below sedimentary basins, as well as to perform detailed structural mapping along the margin. Another important task was to validate existing crustal models for the mid-Norwegian margin which were suggested before precise data was available and which were often based on “scientific guesses”. As a result of data analysis, several new structural elements were found and described in the outer and central parts of the mid-Norwegian margin. For example, a set of crustal marginal plateaus below the basins in the outer part was suggested as the most reasonable explanation for the observed structural geometries. This doctoral study shows that the basin provinces of the margin were subjected to discrete and localized Cretaceous-Paleocene rifting events that sequentially migrated westwards until the continental breakup and associated voluminous magmatism took place 56-55 million years ago. The formation and distribution of smaller sedimentary subbasins were controlled by pinch-and-swell deformation mode of deep crustal blocks. In summary, this work highlights the presence of the continental crust in the outer mid-Norwegian margin. That conclusion contrasts with previously published models inspired by the Iberian-type passive margins characterized by total elimination of the crust in the outer parts prior to breakup. A better understanding of the geological structure and evolution of the basin provinces of the mid-Norwegian margin could guide and facilitate future exploration activities there. That in turn may change considerably the current hydrocarbon resource estimates

Methane release from carbonate rock formations in the Siberian permafrost area during and after the 2020 heat wave

Anthropogenic global warming may be accelerated by a positive feedback from the mobilization of methane from thawing Arctic permafrost. There are large uncertainties about the size of carbon stocks and the magnitude of possible methane emissions. Methane cannot only be produced from the microbial decay of organic matter within the thawing permafrost soils (microbial methane) but can also come from natural gas (thermogenic methane) trapped under or within the permafrost layer and released when it thaws. In the Taymyr Peninsula and surroundings in North Siberia, the area of the worldwide largest positive surface temperature anomaly for 2020, atmospheric methane concentrations have increased considerably during and after the 2020 heat wave. Two elongated areas of increased atmospheric methane concentration that appeared during summer coincide with two stripes of Paleozoic carbonates exposed at the southern and northern borders of the Yenisey-Khatanga Basin, a hydrocarbon-bearing sedimentary basin between the Siberian Craton to the south and the Taymyr Fold Belt to the north. Over the carbonates, soils are thin to nonexistent and wetlands are scarce. The maxima are thus unlikely to be caused by microbial methane from soils or wetlands. We suggest that gas hydrates in fractures and pockets of the carbonate rocks in the permafrost zone became unstable due to warming from the surface. This process may add unknown quantities of methane to the atmosphere in the near future

Basin modelling of a complex rift system: The Northern Vøring Volcanic Margin case example

Extensional processes can lead to complex crustal configuration depending on the mechanisms of lithospheric thinning and the impact of magmatic additions during rifting and breakup. In this context, we studied the Vøring volcanic passive margin offshore Norway. The evolution of the inner Vøring Margin is well explained by standard models of lithosphere extension. However, these models fail to reproduce key observations at the outer (volcanic) province such as regional uplift at the time of breakup and excess magmatism. Therefore, additional processes are required to explain these observations. Excess magmatism and uplift have been related to mantle processes such as the arrival of the hot Icelandic mantle ‘plume’ or small-scale convection processes. Melt retention in the asthenosphere has also been proposed to explain uplift. At last, mantle phase transitions during extension may contribute to uplift. We present tectonic and thermal models of basin evolution along a seismic profile crossing the Northern Vøring Margin. The thermal and isostatic history of basins is constrained through time-forward basin modelling based on an automated inverse basin reconstruction approach. Two scenarios are evaluated: The first one includes pronounced mantle stretching during the last late Cretaceous-Paleocene rifting event, and the second one includes late Paleocene-early Eocene mantle thinning, at the breakup time around 56–54 Ma. Models incorporating late Paleocene-early Eocene mantle thinning and taking into account magmatic processes (melt retention and magmatic underplate) and mantle phase transitions satisfactorily reproduce the specific observations of the outer (volcanic) margin. This result supports the contribution of the hot Iceland plume on the evolution of the Vøring Margin. Our results also indicate that thin-crust models can produce a partially serpentinized mantle beneath the highly extended parts of the Vøring Basin. However, this model fails to reproduce observations. This suggests that serpentinization can occur locally but could not explain the entire lower crustal body nature

The T-Reflection and the Deep Crustal Structure of the Vøring Margin, Offshore mid-Norway

Seismic reflection data along volcanic passive margins frequently provide imaging of strong and laterally continuous reflections in the middle and lower crust. We have completed a detailed 2‐D seismic interpretation of the deep crustal structure of the Vøring Margin, offshore mid‐Norway, where high‐quality seismic data allow the identification of high‐amplitude reflections, locally referred to as the T‐Reflection. Using a dense seismic grid, we have mapped the geometry of the T‐Reflection in order to compare it with filtered Bouguer gravity anomalies and seismic refraction data. The T‐Reflection is identified between 7 and 10 s. Sometimes it consists of one single smooth reflection. However, it is frequently associated with a set of rough multiple reflections displaying discontinuous segments with varying geometries, amplitudes, and contact relationships. The T‐Reflection seems to be connected to deep sill networks and is locally identified at the continuation of basement high structures or terminates over fractures and faults. The T‐Reflection presents a low magnetic signal. The spatial correlation between the filtered positive Bouguer gravity anomalies and the deep dome‐shaped reflections indicates that the latter represent a high‐impedance boundary contrast associated with a high‐density and high‐velocity body. In ~50% of the outer Vøring Margin, the depth of the mapped T‐Reflection is found to correspond to the depth of the top of the Lower Crustal Body (LCB), which is characterized by high P wave velocities (>7 km/s). We present a tectonic scenario, where a large part of the deep crustal structure is composed of preserved upper continental crustal blocks and middle to lower crustal lenses of inherited high‐grade metamorphic rocks. Deep intrusions into the faulted crustal blocks are responsible for the rough character of the T‐Reflection, whereas intrusions into the ductile lower crust and detachment faults are likely responsible for its smoother character. Deep magma intrusions can be responsible for regional metamorphic processes leading to an increasing velocity of the lower crust to more than 7 km/s. The result is a heterogeneous LCB that likely represents a complex mixture of pre‐ to syn‐breakup mafic and ultramafic rocks (cumulates and sills) and old metamorphic rocks such as granulites and eclogites. An increasing degree of melting toward the breakup axis is responsible for an increasing proportion of cumulates and sill intrusions in the lower crust. ©2017. American Geophysical Union. All Rights Reserved

The development of volcanic sequences at rifted margins: New insights from the structure and morphology of the Voring Escarpment, mid-Norwegian Margin

On the Vøring Margin offshore mid-Norway, Paleogene continental breakup was characterized by the extrusion of large volumes of flood basalts erupted in different depositional environments. The transition from subaerial to submarine emplacement environment is marked by the formation of the Vøring Escarpment which records the early encroachment of flood basalt into the basin and the buildup of a lava delta system. The increased availability of new and reprocessed high-quality seismic data allows a more detailed characterization of the along-strike and across-strike continuity and variability of the different volcanic seismic facies units. Detailed seismic interpretation shows that the ~350 km long NE-SW trending Vøring Escarpment is a prominent feature along the Vøring Margin with a height ranging between 200 and 1600 m. Structurally, the Vøring Escarpment is segmented along strike into five segments (E1–E5) with different controlling factors leading to variation in accommodation space. Relative sea level change and magma supply are the major controlling factors for segments E2 and E4 which are characterized by a well-developed lava delta system and significant escarpment height. Tectonic movements along the Jan Mayen Fracture Zone resulted in second-order segmentation of the E1 segment into pseudoescarpments with a very thin lava delta system and limited escarpment height. Segments E3 and E5, situated along the flanks of Cretaceous/Paleocene highs, are controlled by the structural highs, which were possibly reactivated during breakup time. Our mapping results provide crucial information about the paleogeography and yield important information regarding the paleo–water depth and depocenter locations prior to and during the breakup of the Vøring Margin

The Proterozoic evolution of northern Siberian Craton margin: a comparison of U–Pb–Hf signatures from sedimentary units of the Taimyr orogenic belt and the Siberian platform

Identifying the cratonic affinity of Neoproterozoic crust that surrounds the northern margin of the Siberian Craton (SC) is critical for determining its tectonic evolution and placing the Craton in Neoproterozoic supercontinental reconstructions. Integration of new U–Pb–Hf detrital zircon data with regional geological constraints indicates that distinct Neoproterozoic arc-related magmatic belts can be identified within the Taimyr orogen. Sedimentary rocks derived from 970 to 800 Ma arc-related suites reveal abundant Archean and Paleoproterozoic detritus, characteristic of the SC. The 720–600 Ma arc-related zircon population from the younger Cambrian sedimentary rocks is also complemented by an exotic juvenile Mesoproterozoic zircon population and erosional products of older arc-related suites. Nonetheless, numerous evidences imply that both arcs broadly reworked Siberian basement components. We suggest that the early Neoproterozoic (ca. 970–800 Ma) arc system of the Taimyr orogen evolved on the active margin of the SC and probably extended along the periphery of Rodinia into Valhalla orogen of NE Laurentia. We also suggest the late Neoproterozoic (750–550 Ma) arc system could have been part of the Timanian orogen, which linked Siberia and Baltica at the Precambrian/Phanerozoic transition

Regional structure and polyphased Cretaceous-Paleocene rift and basin development of the mid-Norwegian volcanic passive margin

The Møre and Vøring basins of the mid-Norwegian volcanic passive margin are characterized by thick accumulations of Cretaceous to Paleocene sedimentary strata. They were formed during a series of Late Mesozoic-Early Cenozoic extensional events and represent vast underexplored areas with a limited number of wells. Recently, a new generation of long-offset 2D seismic reflection lines and 3D seismic data, together with new well data, has permitted a significant improvement in the regional understanding of the Møre and Vøring basins. This has enabled much better imaging of the deep Cretaceous subbasins and sub-basalt structures. In light of this significant data improvement, we performed a regional tectonostratigraphic synthesis of the pre-breakup development of the Møre and Vøring basins. We have interpreted eight regional Cretaceous and Paleocene horizons and constructed a series of structural and thickness maps. The new interpretations allow us to examine the sequential evolution of the Cretaceous to Paleocene sedimentary infill and to discuss its relationship to the deep crustal structures and regional tectonic events. We conclude that the long and polyphased development of the Møre and Vøring basins is partly controlled by deep-seated structural highs. We show that active deposition in the Early Cretaceous was mainly focused in the Møre Basin, while the main Cenomanian and subsequent Late Cretaceous-Paleocene depocentres developed principally in the Vøring Basin and migrated sequentially west towards the present continent-ocean boundary. We argue that the outer Møre and Vøring basins are likely underlain by a relatively thick continental crust compared to the inner part of the regional sag basin. In this setting our observations do not support evidence for a large zone of exhumed upper mantle, which has previously been proposed to have formed before magmatism and breakup