Fault gouge characterization in the Øygarden complex in SW Norway – relevance for offshore CO2 storage
The Øygarden complex in southwestern Norway consists of gneisses of the Baltic shield that were reworked during the Caledonian orogeny. Post-orogenic collapse and extension has led to faulting which dominates the areas stretching from the Viking graben in the North Sea to western Norway. Since the 1970’s, the petroleum industry has mapped and analyzed fault systems and potential reservoirs offshore, across the Norwegian continental shelf. Carbon capture and storage (CCS) has become increasingly relevant over the past 20 years, but more data are required to store larger quantities of CO2 safer, and more cost efficiently. The Horda platform offshore from the Øygarden Complex, is of high relevance for the Northern Lights project for large scale carbon capture and storage.
This project aims to investigate and quantify how fault gouging affects the mechanical and structural properties along the fault planes of the gneisses in the Øygarden complex. Fault gouging is a result of brittle deformation along the fault plane, where the rock has been crushed into smaller grain size material. During CO2 injection, the fluid pressure in the reservoirs increases, which alters the stress state or fluid pressure on nearby faults. To better understand how faults within the Øygarden fault complex might respond to CO2 injection, more information on fault gouge properties is needed.
The project will involve methods from structural geology to geomechanics:
- Field work in Øygarden
Structural field work and sampling in the Øygarden complex, SW Norway, of 4-8 of sites, depending on the quality of the outcrops. The selection of localities will be guided by previous work on fault gouges (Ksienzyk, et al., 2016) and late Caledonian extensional shear zones (Wiest et al., 2020) in the region. A sample from the Lærdal-Gjende Fault may be included.
- Microscopy at UiB
Sample characterization using optical microscopy and SEM-imaging to outline the composition and structures of fault gouges observed in the field area.
- Lab work at NGI
Depending on the quality of the fault gouge material and the sample sizes from the field work, 3-6 fault gouge samples will be used for lab experiments. If material from the field is not available or is of insufficient quality or size, synthetic samples made from grinding of the host rock will be used instead.
The lab work will include consolidation of the samples – and performance of direct shear tests at low stress. The data from these experiments will be used to interpret the strength properties of the fault material by using the Mohr – Coulomb failure criterion. These results will then be used for an overall evaluation of the faults.
STAT110 – Basic Course in Statistics (10)
GEOV251 – Advanced Structural Geology (10)
GEOV241 – Microscopy (10)
GEOV345 – Regional geologic excursion to Western Norway (5)
GEOV252 – Field course in geological mapping (10)
AG349 – Geological constrains on CO2 storage on Svalbard (5)
GEOV242 – Igneous and Metamorphic Petrology (10)
GEOV302 – Data analysis in earth science (10)