Improving the Efficiency of Active and Passive DAS Seismic Monitoring in an Onshore CCUS Demonstration Field

Abstract Long-term monitoring of injected CO2 in Carbon Capture Utilization and Storage (CCUS) projects, particularly seismic monitoring, constitutes a substantial portion of operational costs, despite CCUS's critical role in achieving carbon neutrality. Distributed Acoustic Sensing (DAS) technology offers a solution to reduce the cost and workload associated with monitoring in CCUS projects. This study focuses on improving operational efficiency by reviewing techniques for active seismic acquisition and continuous passive seismic monitoring, as demonstrated by Nakayama et al. (2024a, 2024b, and 2024c) in an onshore CCUS field test at the Minami-Aga field, a depleted oilfield in Japan. For active seismic monitoring, a walk-away DAS vertical seismic profiling (DAS-VSP) survey using a simultaneous source acquisition method, known as the slip-sweep method, was conducted as a baseline seismic survey. The comparison between traditional and slip-sweep acquisition methods revealed no significant differences in data quality, with the slip-sweep method nearly doubling acquisition efficiency. To manage the vast amounts of data generated during continuous passive seismic monitoring, a DAS system and real time data handling framework were employed. Microseismic (MS) events during the CO2 injection test were detected and located using a real time data analysis approach, resulting in the identification of approximately 1,200 events with estimations of their locations and moment magnitudes. The DAS system demonstrated high sensitivity to small-magnitude events. These field trials underscore the importance of enhancing operational efficiency to fully realize the potential of DAS in both active and passive seismic monitoring within CCUS projects.