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Influence of basement involvement during Jurassic rifting in the North Sea. A 3D seismic investigation coupled with field analogues from western Norway

The Smeaheia CO2 storage prospect envisages safely injecting and storing up to 1.3Mt of CO2 within Jurassic siliciclastic reservoirs (Sognefjord and Fensfjord formations of the Viking Group) of the Horda Platform (Blocks 32/4 and 32/1 of the North Sea) over a 25-year period. The area which lies approx. 20km east of the Troll A platform is structurally complex owing to rift phases during the Permo-Triassic and Mid-Jurassic which have resulted in north-south trending basement-involved faults and a population of northwest to southeast striking subsidiary faults.

Two of these basement-involved faults, i.e., the Vette fault to the west, and the Øygarden fault to the east bound the Smeaheia prospect. Two main closures, Alpha and Beta (Figure 1), have been defined as trapping structures, which developed as fault-propagation features during accrual of displacement on the aforementioned faults. The overburden consists of the Draupne Formation, a mudstone-rich marine deposit, which forms the main top-seal and the overlying Cromer Knoll, and Shetland groups, which comprise carbonates and deep-water sediments. The overlying sequence comprises the mud-dominated Cenozoic succession. Structurally, the overburden is affected by tectonic and polygonal faulting, glacial scouring, and pockmarks, the inter-connectivity of which (if any) have to date not been adequately described.

Figure 1. Details of the structural architecture of the Alpha and Beta prospects

We seek a motivated MSc student to address knowledge gaps in the structural framework and evolution of the Smeaheia area that will help de-risk the proposed injection and storage of CO2 in the prospect. Students will primarily work with high quality 3D seismic workflows (e.g., Figure 2), which will be beneficial for future careers/research in CO2 storage or hydrocarbon exploration. Work on the projects will begin in spring 2018, with a completion date of 1st June 2019.

Figure 2. Workflow diagram illustrating seismic investigation and fault analyses methods being applied to the structural de-risking of the Smeaheia prospect

The propagation history of faults can often be determined in 3D seismic data by the recognition  syn-kinematic packages, anomalies in fault displacement profiles, and variations in the geometry of the fault plane, i.e., undulations or sudden changes in strike/dip. In map view the prospect-bounding Vette and Øygarden faults show locally variable strikes. Furthermore, preliminary investigations (Jonassen, 2015) showed displacement profiles on both faults show considerable contrast in styles. This contrast may reflect the relatively high position of the basement in the footwall of the Øygarden fault where the fault effectively juxtaposes basement rocks with the proposed Jurassic reservoir rock.

This project will consider:

  1. the influence of basement propagation in the evolution of Mesozoic faulting in the Smeaheia area,
  2. explore the effects of mechanical stratigraphy on fault propagation,
  3. consider the fault sealing implications of reservoir – basement rock juxtaposition.

Further, the project will include field analogues of basement rocks and faults from western Norway.

Seismic interpretation of 3D datasets, fault displacement and attribute analysis. Field mapping and collection of structural/sedimentological data.

Learning and skillsets:
Proficiency using Schumberger Petrel E&P Software Platform and Midland Valley Move and or Badley’s T7. Independent research, academic writing and presentation skills.

Tags: Structural geology, carbon capture and storage, seismic interpretation, fault analysis, back-stripping/restoration, North Sea geology
Published Nov. 12, 2018 11:21 AM - Last modified Nov. 12, 2018 11:21 AM

Scope (credits)