Abstract
Smeaheia, a prominent fault block located on the Horda Platform, northern North Sea is identified as a potential subsurface CO2 storage site. We utilise the GN1101 3D seismic survey to generate a high-resolution subsurface geomodel to inform the structural style and evolution of the fault block, to investigate geological controls on proposed CO2 storage and provide a geometric framework as a basis for future analyses. Two basement-involved (first-order) north-south trending fault systems, the Vette Fault Zone (VFZ) and the Øygarden Fault Complex (ØFC), bound the 15 km-wide fault block. The VFZ bifurcates down-section where it is hard-linked with two separate basement structures, a phenomenon we term as “dual rooted”. Apart from activity during the Permo-Triassic (Rift Phase 1) and the Late Jurassic–Early Cretaceous (Rift Phase 2), we present evidence that rifting in this part of the North Sea continued into the Late Cretaceous with minor reactivation in the Palaeocene–Eocene. Two segments of the VFZ interacted and linked at a relay ramp during Rift Phase 2. Second-order (thin-skinned) faults show basement affinity and developed during Rift Phase 2 in two distinct pulses. A population of polygonal faults intersects the overburden and developed during the Eocene to middle Miocene. We have revised the areal extent of two structural closures that define the Smeaheia fault block, Alpha (VFZ footwall) and Beta (ØFC hanging wall) which consist of Upper Jurassic Viking Group target formations. Simplified cross-fault juxtaposition analysis of the VFZ and second-order intra-block faults are presented and inform pressure communication pathways between the Smeaheia and Tusse fault block, as well as reservoir integrity and compartmentalisation. The geomodel further identifies important geological controls on CO2 storage in the fault block including a thinning caprock above the Alpha structure, and identification of hard-linkage between deep tectonic faults and shallow polygonal faults.
Highlights
In an effort to combat climate change (Intergovernmental Panel on Climate Change Special Report, 2005; 2007, 2014), the European Commission has outlined an ambitious target to reduce anthropogenic emission of greenhouse gasses by 80–95% by 2050 with respect to 1990 levels (E.U. Commission, 2018)
The GN1101 seismic survey provides high resolution imagery of the Smeaheia fault block which is one of several rotated fault blocks that comprise the northern Horda Platform, and more regionally, the eastern margin of the North Sea rift system. This localised study provides insight for the timing of rifting on the Horda Platform, especially during Rift Phase 2 (JurassicCretaceous rifting) which previous workers have described as dia chronous with strain localisation in the Viking Graben area, but east wards migration of activity over a 30 My period (e.g., Bell et al, 2014). As such this section starts with a detailed discussion on the timing of first- and second-order fault activity in the Smeaheia fault block which contributes to regional understanding of how and when the Horda Platform developed
Creation and analysis of a geomodel derived from the GN1101 3D seismic survey and a regional 2D grid has informed the structural style and evolution of the Smeaheia fault block in the Horda Platform
Summary
In an effort to combat climate change (Intergovernmental Panel on Climate Change Special Report, 2005; 2007, 2014), the European Commission has outlined an ambitious target to reduce anthropogenic emission of greenhouse gasses by 80–95% by 2050 (including 500 Gt of CO2) with respect to 1990 levels (E.U. Commission, 2018). In CCS, CO2 is captured at point sources e.g., CO2-emitting industrial plants, transported to suitable in jection sites by pipelines or ships and sequestered within subsurface storage formations, e.g., saline aquifers and depleted hydrocarbon fields (Intergovernmental Panel on Climate Change Special Report, 2005; Bachu, 2008; Benson and Cole, 2008; Gibbins and Chalmers, 2008). Current EU-wide facilities, will fall short of the estimated 12 Gt of CO2 storage required to meet the 2050 targets (International Energy Agency, 2013). As such additional sequestration projects are necessary
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