The CO2CRC Otway International Test Centre in Victoria serves as a globally recognised research facility for advancing monitoring technologies that ensure safe and effective geological carbon storage (GCS). Stage 4 Otway Project is designed to test continuous and time-lapse seismic monitoring during controlled CO₂ injection into a heterogeneous saline aquifer at ~1.5 km depth. Between November 2024 and January 2025, 10 kt of CO₂-rich gas were injected. Monitoring utilised distributed acoustic sensing (DAS) across multiple wells, permanent surface orbital vibrators (SOVs), and time-lapse vertical seismic profiling (VSP) surveys to provide both active and passive seismic datasets.

For Stage 4, the final monitor dataset from the Stage 3 campaign in 2021 was adopted as the baseline. The first dedicated Stage 4 monitor (M9) survey was acquired in February 2025. A dedicated 4D processing workflow produced coherent and repeatable results across vintages, enabling robust time-lapse comparison. The 4D analysis successfully imaged the full 10 kt CO₂-rich gas plume, with anomalies clearly observed near the CRC-4 and CRC-5 wells, consistent with the injection interval and the known heterogeneity of the aquifer. These observations confirm the ability of DAS-enabled VSP to resolve plume migration and geometry at the reservoir scale.

A further 10 kt injection is scheduled for January–March 2026. Two additional monitor surveys are planned for December 2025 and March–April 2026, which will extend the dataset and further validate permanent, fibre-optic based seismic monitoring as a cost-effective and scalable solution for long-term CO₂ storage conformance and assurance.