Abstract
Carbon capture and storage (CCS) is a key backstop technology for achieving carbon peaking and carbon neutrality, and a monitoring system that is safe, effective and cost-rational is a prerequisite for the approval, continued operation, and public acceptance of CO2 geological storage projects. This paper reviews the monitoring technology systems of ten typical international CCS projects—Sleipner, Northern Lights, Tomakomai, In Salah, Decatur/IBDP, Nagaoka, Weyburn–Midale, Cranfield, Otway, and Ketzin—and analyzes how four factors—storage type, geological conditions, regulatory context, and project stage—shape the technical route of monitoring. China’s first full-chain saline-aquifer storage demonstration, the Shenhua Ordos CCS project, is then compared with these projects along multiple dimensions. The results show that mature international projects generally adopt risk-driven, full-lifecycle, and hierarchically designed monitoring programs: offshore saline-aquifer projects rely on time-lapse (4D) seismic as the core method, supplemented by gravity, electromagnetic, and marine environmental monitoring, whereas onshore projects have developed site-specific combinations such as InSAR, permanent electrical resistivity, microseismic, and integrated VSP. For Shenhua CCS, three time-lapse VSP surveys formed the core of its geophysical program (the plume migration range within the injection interval extended from 350 m to 450 m, with no wave-field anomaly detected in the caprock at about 950 m depth), supplemented by self-developed downhole pressure/temperature gauges (drift error reduced from 2.17% to 0.26%) and multi-indicator near-surface monitoring; within an injected volume of 302,600 t, no leakage was detected in any monitored domain at the sensitivity of the deployed arrays, with a construction capital expenditure of about RMB 210 million (≈USD 31 million) and a full-chain cost of about RMB 280/t (≈USD 41/t). Compared with advanced international practice, gaps remain in the design paradigm (the transition from verification-oriented to risk-oriented design has not yet been completed), the large-scale application of high-resolution geophysics, institutionalized monitoring–modeling closure and data sharing, and technical standards and equipment localization. A pathway of risk-based hierarchical design, low-cost high-value technology portfolios, monitoring–modeling closure, standards first, and data sharing is therefore proposed for China’s megaton-scale storage projects.