The Critical Role of Monitoring in Offshore Carbon Capture and Storage

Abstract Objective and Scope Offshore Carbon Capture and Storage (CCS) aims to mitigate greenhouse gas emissions by transporting CO2 from onshore sources to offshore geological formations such as depleted reservoirs and saline aquifers. This strategy leverages existing oil and gas infrastructure to facilitate CO2 injection into secure subsurface locations. A key objective is to ensure long-term containment of the injected CO2 to maintain public trust and prevent environmental damage, particularly to sensitive subsea ecosystems. Maintaining reservoir integrity is essential, as any leakage could compromise both environmental safety and project viability. Methods, Procedures, Process To safeguard offshore CCS sites, Measurement, Monitoring, and Verification (MMV) systems are deployed to detect potential leaks and assess site integrity. Sonardyne contributed to a three-year MMV research initiative that included offshore trials using autonomous underwater vehicles (AUVs) for localized and wide-area site assessments. Monitoring strategies focused on high-risk zones such as injection wellheads, geological fault lines, and manmade subsea infrastructure. The monitoring process is divided into two phases: Baseline Monitoring, conducted over 12 months prior to injection to establish environmental norms, and Injection Phase Monitoring, which involves continuous, high-frequency data collection during CO2 injection operations. Results, Observations, Conclusions The MMV system demonstrated effectiveness in confirming the secure containment of CO2 at offshore sites. Baseline monitoring provided a comprehensive understanding of natural environmental variations, while injection phase monitoring enabled timely detection of anomalies indicative of potential leaks. The integration of physical oceanography, marine chemistry, and biology proved vital in overcoming challenges such as rapid CO2 dissolution, water column mixing, and seasonal variability. These observations affirm the importance of robust monitoring protocols to ensure CCS site integrity. Novel/Additive Information This approach underscores the complexity of subsea CCS monitoring and the necessity of a multi-faceted approach. The use of AUVs and advanced sensing technologies within MMV frameworks marks a significant advancement in environmental monitoring capabilities. Establishing detailed baseline datasets and maintaining continuous surveillance are critical for distinguishing natural fluctuations from containment breaches. These innovations contribute to the broader goal of safe, reliable, and publicly accepted offshore carbon storage solutions.