To safely operate CCS businesses, CO₂ must be stored in subsurface formations without leaking into the subsurface, near surface, or atmosphere. Thus, the surface and subsurface physical properties require regular or frequent monitoring using various geophysical and engineering technologies to detect the lateral and vertical distribution of the injected CO₂. According to a report published by IEA in 2020, more than 40 monitoring technologies have been evaluated and compared. We continue to progress in industry-leading research on monitoring technologies to develop cost-effective and eco-friendly methods for future CCS businesses.

The geological features of a storage site are crucial to ensure secure and efficient CO₂ storage, because the behavior of the injected CO₂ depends on the geological characteristics of the storage reservoir, caprock, and surrounding formation. A storage site is evaluated based on geological, petrophysical, and geophysical data such as core samples, wireline logs, and seismic data. Moreover, outcrop analogs can assist in site characterization. Combining these approaches, we conduct research projects to understand the geological characteristics of storage sites and the influence of these characteristics on CO₂ injection efficiency and storage security.

Engineering studies on the behavior of injected CO₂ within the formation for the injection period as well as long-term post-injection period is crucial for planning a CCS operation to evaluate if the planned volume of CO₂ can be safely stored in target formations for a long time. Generally, this evaluation is performed by analyzing the spatiotemporal distribution of each fluid phase (e.g., gas, liquid, or supercritical) of the injected CO₂. In particular, the CO₂ injected into the subsurface formations migrate, diffuse, and dissolve during injection and post-injection owing to the diference between the density, concentration, and thermodynamic nonequilibrium of the injected CO₂ and formation water. The dissolved CO₂ yields chemical reactions with rocks such as mineral dissolution and precipitation, thereby causing variations in the rock properties of the reservoirs and caprocks in addition to mineralizing the CO₂ injected in the porous media. In forecasting the long-term behavior of stored CO₂, numerical simulations are used to handle complicated behaviors and reactions, which may not be considered for the oil and natural gas development. Thus, we evaluate the approach to accurately predict these phenomena related to geological CO₂ storage using numerical simulations.