SVELVIK CO2 FIELD LAB (ECCSEL-NO-3.12)

Svelvik CO₂ Field Lab is a small-scale laboratory in an easily accessible geological environment, which fills the gap between bench laboratory experiments and pilots. Due to its size, the controlled environment, and the potential of repeatable experiments, the field laboratory provides excellent possibilities to perform rapid and cost-efficient development and testing of CO₂ monitoring methods and equipment.

The laboratory is established in the glaciofluvial-glaciomarine Holocene deposits of the Svelvik ridge and occupies a non-active part of a sand and gravel quarry in the outer part of Drammensfjorden, about 50 km south-west of Oslo in Norway. Down to approximately 30 m, the test site consists of unconsolidated to weakly consolidated sand. Below, rather heterogeneous, and interlayered sand, silt and clay layers in varying proportions exist, displaying a large span of porosity and permeability.

The field laboratory consists of an injection well and four monitoring wells. The injection well is designed for injecting water and/or CO₂ at 64-65 meters depth. Tracers may be added to the CO₂ stream. The four monitoring wells are 100 m deep and positioned at the corners of a rhombus with the injection well (#2) in the centre. The monitoring wells are located 9.9 m (M3 and M4) and 16.5 m (M1 and M2) from the injection well. 

Areas of research at Svelvik CO₂ Field Lab include different aspects related to CO₂ monitoring and leakage detection:

• Development and testing of seismic and non-seismic techniques
• Quantitative CO₂ monitoring including pressure and saturation determination
• Fibre optic-based monitoring including testing of new cables, interpretation of recorded signals, and comparison with conventional methods
• Surface detection methods for CO₂ leakage
• Testing tracers for CO₂ storage and leakage detection

Instrumentation of monitoring wells

The monitoring wells are completed with PVC casing and instrumented behind the casing with:

• Capillaries for pore pressure measurements at three different depths, including the injection depth
• Capillaries for water sampling at the depth of injection
• Sensors measuring pressure and temperature at the depth of injection
• Electrodes for electrical resistivity tomography (ERT)
• Commercial fibre optic cables from SOLIFOS: Straight DTS (Distributed Temperature Sensing), DSS (Distributed Strain Sensing) and DAS (Distributed Acoustic Sensing)
• Fibre optic cables provided by Lawrence Berkley National Laboratory (LBNL): Straight (DSS and DAS) and helical (DSS and DAS).

The interior of the wells is available for non-permanent monitoring equipment as the permanent instrumentation has been installed behind the casing. For instance, seismic P- and S-wave borehole sources may be used together with 3C borehole receivers or hydrophone chains, creating high resolution seismic cross-well data sets. The collocation of conventional seismic receivers and DAS cables will provide additional opportunities for the development and testing of fibre optic cables and processing techniques for this type of data. The inside of the wells will also be available for development and testing of future monitoring systems.

Fibre optic cable installation

The commercial fibre optic cables are thin and flexible and could therefore be installed in a continuous loop through all four wells without splicing. Terminated ends are located inside an instrument cabin. While the DTS cable consists of four multi-mode fibres; two 50 mm and two 62.5 mm fibres, the DSS and DAS cables are composed of one and four single-mode fibres, respectively.

The straight cable from Lawrence Berkeley National Laboratory is a standard tactical fibre cable, whereas the helical cable is constructed using optical fibres wound at a 30° angle on a low durometer central mandrel. Both cables are relatively thick and stiff and had therefore to be cut off at the well-ends. To facilitate looping comparable to the commercial cable installations, the fibres inside the cables were spliced at the well-ends, creating down- and upgoing branches, connected at the well bottom. The cables will be looped in a future project.

Svelvik CO₂ Field Lab enables cost-efficient studies of quantitative CO₂ monitoring methods and technology where high-quality data can be acquired under controlled conditions; where pressure and CO₂ saturation can be varied independently; where a cross-well setup yields clean data undisturbed by "outside" or surface effects; and where experiments are repeatable as CO₂ is not stored permanently in the subsurface. Svelvik CO₂ Field Lab is unique as no other test sites can offer this combination.

Skilled scientists and technicians are available to assist visiting researchers, both on-site and remotely. One experienced person from SINTEF will be on-site as the on-site HMS manager during the project execution. Only trained SINTEF personnel are allowed to operate the injection infrastructure.

SINTEF has implemented and maintains a quality management system that fulfils the requirements of the standard NS-EN ISO 9001:2008 within research and development in materials technology, advanced materials and nanotechnology, applied chemistry and biotechnology, oil and gas, and green energy and process industry.