Monitoring long-term storage of CO2 in a gas and condensate field in the North Sea off the coast of Norway using seismic methods

Abstract

The rising concentration of CO<inf>2</inf> in the atmosphere drives climate change, prompting the development of various mitigation strategies. One approach involves injecting CO<inf>2</inf> into hydrocarbon reservoirs for long-term storage. For long-term storage, one needs to monitor the injected CO<inf>2</inf> to see the CO<inf>2</inf> storage location and detect any leakage. This study focuses on the monitoring of injected CO<inf>2</inf> in the Utsira Formation from a gas and condensate field in the Sleipner Field off the coast of Norway. The monitoring of injected CO<inf>2</inf> is carried out using seismic inversion techniques of time-lapse data acquired over the injected zone at different time intervals. Seismic inversion techniques transform seismic reflection data into quantitative acoustic impedance models of the subsurface. The objective of the present study is to compare model-based inversion, band-limited inversion (BLI), maximum likelihood inversion, linear programming inversion (LPI) and sparse layer reflectivity inversion (SLRI) approaches to monitor CO<inf>2</inf>. All inversion techniques show consistent results, with low impedance values ranging from 2115 to 5275 m/s*g/cm3 in the Utsira Formation. Among these techniques, SLRI and LPI outperform traditional methods by offering high-resolution imaging of CO<inf>2</inf> migration pathways, making them particularly effective for early leak detection and reducing uncertainties in reservoir modeling. By enhancing storage security and predictive modeling, these methodologies significantly contribute to the scalability and reliability of carbon capture and storage as a critical tool in combating climate change. This research not only strengthens the scientific foundation of seismic monitoring techniques but also provides practical recommendations for optimizing subsurface CO<inf>2</inf> storage assessment methods. © 2025 Society of Exploration Geophysicists. All rights reserved.