Quantitative comparison of DAS and point seismic sensors at Svelvik CO2 Field Lab

Time-lapse monitoring is one of the main requirements for Carbon Capture and Storage sites. Seismic monitoring, the most used geophysical method for such purpose, is central to tracking subsurface changes during CO2 injection. However, as CCS deployment scales up, monitoring technologies must balance data quality, operational practicality, repeatability, and long-term cost-effectiveness. Distributed Acoustic Sensing (DAS) offers a viable alternative to conventional sensors for permanent installation and monitoring of large-scale CCS sites. However, as DAS is still considered an emergingtechnology, its performance must be evaluated against established instruments under controlled field conditions.  

DAS provides many advantages, including requirement for electrical power only at one fibre end, dense spatial sampling, and the ability to record many channels over large coverage from a single interrogator. At the same time, DAS measurements can be affected by higher noise levels, directional sensitivity, gauge-length and pulse-width effects, and variable coupling between the fiber and the surrounding medium. 

Here, we present a comparative study of surface and borehole fiber-optic seismic sensing during a CO₂ injection experiment at the Svelvik CO₂ Field Lab in May 2026. Injection was conducted in a central 65 m deep borehole, surrounded by four 100 m deep monitoring boreholes located 9–16 m from the injection well and instrumented with cemented fiber-optic cables. During the survey, a P-wave sparker source was deployed in the monitoring boreholes and on a surface in a prototype seismic source.  The DAS system included straight and helically wound borehole fibers cemented outside of the monitoring wells, together with a prototype fiber optic surface sensor coupled to the ground with adjustable fluid mass loading. The entire fiber layout was interrogated simultaneously with an ASN OptoDAS interrogator. The DAS data are compared with measurements from borehole hydrophone strings, surface geophones, standalone seismic nodes, and a prototype of a optical MEMS-based accelerometer, allowing direct comparison of multiple sensors under identical field conditions. 

We evaluate signal-to-noise ratio, repeatability metrics, stacking performance, quantitative signal attributes, and time-lapse response. The study provides a field-based assessment of how DAS-based seismic data can complement conventional and novel point seismic sensors for high-resolution monitoring of CO₂ injection and other shallow subsurface processes.