Advancing Undersea CO2 Storage Monitoring
Research from the Norwegian University of Science and Technology (NTNU) aims to improve the monitoring of CO2 stored in undersea geological reservoirs. This research seeks to determine the location of injected CO2 and detect potential leakage.
Sleipner Project and Full-Waveform Inversion
Norway's Sleipner gas field hosts the world's longest-running undersea CO2 storage project, where 20 million tons of CO2 have been injected into the Utsira Formation, a saline aquifer.
Researchers at NTNU's Centre for Geophysical Forecasting (CGF) have applied a data-analysis technique called full-waveform inversion to geophysical data from Sleipner, including seismic imaging. A recent publication by CGF PhD Ricardo Jose Martinez Guzman details the technique's effectiveness in verifying CO2 presence and injected volumes.
Current Monitoring Challenges
Current monitoring practices typically involve ships towing acoustic sensors in a grid pattern over undersea formations. While land-based CO2 storage can be monitored through wells, offshore sites rely on geophysical data due to depths of a thousand meters or more below the seabed.
Innovative Laboratory Testing
CGF has also developed a new laboratory featuring a 2-by-4 meter water tank. This tank contains a several-hundred-kilogram model of the Utsira Formation's cap rock, which is designed to prevent CO2 leakage. The lab serves as a test environment for different measurement methods, using air as a proxy for CO2. Researchers can use 30 years of data from the Sleipner site for comparisons and calibration.
Kasper Hunnestad, a CGF postdoc, operates the lab, using ultrasonic senders and receivers to scan the mock-up as air is injected. Multiple scans create a timeline of air distribution, simulating CO2 monitoring in the field. The lab's controlled environment allows researchers to test scenarios, such as the impact of reduced data on CO2 distribution monitoring, potentially leading to cost reductions and improved accuracy for storage site monitoring.
Future Outlook and Industry Interest
CGF's industrial partners are reportedly interested in the test laboratory's findings due to the competitive nature of geophysical monitoring services. Martin Landrø, CGF director, suggested that future monitoring solutions might involve deploying fibre optic cables on the seabed, noting their low material cost compared to conventional seismic cables.