The influence of structural inheritance and multiphase extension on rift development, the northern North Sea

The northern North Sea rift evolved through multiple rift phases within a highly heterogeneous crystalline basement. The geometry and evolution of syn‐rift depocentres during this multiphase evolution, and the mechanisms and extent to which they were influenced by pre‐existing structural heterogeneities remain elusive, particularly at the regional scale. Using an extensive database of borehole‐constrained 2D seismic reflection data, we examine how the physiography of the northern North Sea rift evolved throughout late Permian‐Early Triassic (RP1) and Late Jurassic‐Early Cretaceous (RP2) rift phases, and assess the influence of basement structures related to the Caledonian orogeny and subsequent Devonian extension. During RP1, the location of major depocentres, the Stord and East Shetland basins, was controlled by favorably oriented Devonian shear zones. RP2 shows a diminished influence from structural heterogeneities, activity localises along the Viking‐Sogn graben system and the East Shetland Basin, with negligible activity in the Stord Basin and Horda Platform. The Utsira High and the Devonian Lomre Shear Zone form the eastern barrier to rift activity during RP2. Towards the end of RP2, rift activity migrated northwards as extension related to opening of the proto‐North Atlantic becomes the dominant regional stress as rift activity in the northern North Sea decreases. Through documenting the evolving syn‐rift depocentres of the northern North Sea rift, we show how structural heterogeneities and prior rift phases influence regional rift physiography and kinematics, controlling the segmentation of depocentres, as well as the locations, styles and magnitude of fault activity and reactivation during subsequent events

Architecture of the evaporite accumulation and salt structures dynamics in Tiddlybanken Basin, southeastern Norwegian Barents Sea

An extensive, reprocessed two‐dimensional (2D) seismic data set was utilized together with available well data to study the Tiddlybanken Basin in the southeastern Norwegian Barents Sea, which is revealed to be an excellent example of base salt rift structures, evaporite accumulations and evolution of salt structures. Late Devonian–early Carboniferous NE‐SW regional extensional stress affected the study area and gave rise to three half‐grabens that are separated by a NW‐SE to NNW‐SSE trending horst and an affiliated interference transfer zone. The arcuate nature of the horst is believed to be the effect of pre‐existing Timanian basement grain, whereas the interference zone formed due to the combined effect of a Timanian (basement) lineament and the geometrical arrangement of the opposing master faults. The interference transfer zone acted as a physical barrier, controlling the facies distribution and sedimentary thickness of three‐layered evaporitic sequences (LES). During the late Triassic, the northwestern part of a salt wall was developed due to passive diapirism and its evolution was influenced by halite lithology between the three‐LES. The central and southeastern parts of the salt wall did not progress beyond the pedestal stage due to lack of halite in the deepest evaporitic sequence. During the Triassic–Jurassic transition, far‐field stresses from the Novaya Zemlya fold‐and‐thrust belt reactivated the pre‐salt Carboniferous rift structures. The reactivation led to the development of the Signalhorn Dome, rejuvenated the northwestern part of the salt wall and affected the sedimentation rates in the southeastern broad basin. The salt wall together with the Signalhorn Dome and the Carboniferous pre‐salt structures were again reactivated during post‐Early Cretaceous, in response to regional compressional stresses. During this main tectonic inversion phase, the northwestern and southeastern parts of the salt wall were rejuvenated; however, salt reactivation was minimized towards the interference transfer zone beneath the centre of the salt wall

Seismic stratigraphic subdivision of the Triassic succession in the Central North Sea; integrating seismic reflection and well data

<p>The Triassic sedimentary succession in the Central North Sea has been investigated to establish a broader understanding of the Triassic Period, from the combined interpretation of seismic reflection data and well data. The Triassic succession has been subdivided into four seismic units, where unit boundaries are characterized by regional seismic amplitude anomalies, reflecting changes in gross sedimentary facies or rock properties. A successful correlation between sedimentary facies, interpreted within the well sections and distinct seismic reflection patterns, allowed a thorough mapping of the gross palaeoenvironment throughout the Triassic. The method presented of subdividing a continental sedimentary succession into seismic units should be applicable elsewhere in other basins. The main source area during the Triassic was Scandinavia to the north, and sediment transportation was mainly along north–south- and NE–SW-trending lineaments, which are at present located onshore southern Norway, and in the Åsta Graben and the Varnes Graben offshore. An uplifted Skagerrak Graben area acted as source area in the Early and early Middle Triassic, with sediment dispersal to the south and SW. High relief existed for a longer period in western Scandinavia than in eastern Scandinavia, which supports an asymmetric shape of the Scandinavian mountains during the Triassic. Accommodation space in the Early Triassic was mainly controlled by the relief inherited from a Late Carboniferous–Permian rift phase. Although thermally induced regional subsidence continued in the Middle and Late Triassic, creation of local accommodation space was mainly limited to halokinesis, including redistribution and withdrawal of salt from the subsurface. The Upper Triassic succession is eroded across the western and central parts of the study area, although the Upper Triassic unit is preserved in synforms adjacent to salt structures. In the western part of the study area, dry, playa conditions prevailed during the Early Triassic, although fluvial systems supplied long-transported sandy detritus southeastwards in the late Early Triassic. More sandy detritus was transported into the sedimentary basin in the Middle and Late Triassic, concurrently with a gradually wetter climate. </p

CCS in the Skagerrak/Kattegat area

This paper presents an ongoing project with the aim to assess a CO 2 infrastructure in the Skagerrak/Kattegat region (the sea bordered by north of Denmark, south coast of Norway and the west coast of Sweden). The area comprises 10-12 CO2 emission sources of more than 0.5 Mt/year. The geological and geophysical assessment of CO2 storage potential in the described area as well as reservoir modelling and simulations are performed in work package (WP) 1. The results from WP1 are used in the other work packages. Candidate storage sites are matched with those point sources in the region that are technically and economically feasible for CO2 capture, together with an assessment of the connecting infrastructure needs. WP 2 focuses on identifying optimal technological CO2 infrastructure solutions. Sources-to-sink solutions are in the process of being developed based on input from WP1 and WP3. Assessment of the build-up of a complete CCS infrastructure from a system perspective is the overall focus of WP 3, covering economical, practical and judicial aspects. The project group explores the economic potential for capture at each individual site including looking at other CO2 mitigation options and propose relevant capture technology with cost estimations. Dissemination of project results is organized in a separate work package, WP4