The prospective research of CO2 storage in northwestern Taiwan － Assessment and Simulation of CO2 Storage in Selected Coastal Regions

Carbon capture, storage, and utilization (CCSU) is regarded by scientists and industries as one of the most effective methods for large-scale reduction of atmospheric CO₂ levels and is an essential tool in achieving global net-zero targets. However, the feasibility of CO₂ storage in Taiwan's environment and its potential for effective storage capacity are contingent upon the region's geological characteristics. Several years ago, the Taiwanese government and state-owned enterprises conducted investigations to assess the possibility of implementing CO₂ storage domestically. Preliminary estimates suggested that the potential storage capacity could reach up to 40 billion tons, significantly reducing Taiwan's carbon footprint. However, the actual storage areas and methods are still under investigation and research.

Considering Taiwan's location in an active orogenic zone and its dense population, extensive surveys and evaluations have identified that the most suitable storage methods would involve injecting CO₂ into offshore regions or beneath the uncompressed layers of coastal plain areas along Taiwan's western shoreline.

This study employs the numerical multiphase reactive-transport simulator TOUGHREACT with the ECO2N module, incorporating data from selected areas along the northwestern coastal region of Taiwan. Stratigraphic layering is derived from processed subsurface data, while reservoir permeability is determined from 3D core scans, with limited experimental measurements conducted on a single core sample for validation. A geological model was constructed to evaluate potential storage formations, including the depth, thickness, permeability, and porosity of both reservoir and caprock layers.  CO₂ migration, pressure buildup, and various trapping mechanisms—structural, residual, and solubility trapping—are further investigate to assess the long-term feasibility of CO₂ storage. The storage capacity is quantified in terms of total storage volume and the percentage contribution of each mechanism, with a focus on identifying potential leakage risks based on a realistic geological framework.

Numerical simulations are conducted to analyze the influence of key parameters such as porosity, permeability, relative permeability curves, and capillary pressure curves on CO₂ plume migration and storage efficiency. The study also examines the impact of geological heterogeneities, including layered structures and fault systems, incorporating field survey data to evaluate their role in storage performance and leakage risks. 

The research focuses on two key objectives: 1) analyze the impact of rock permeability on storage performance, and 2) evaluating CO₂ physical storage performance and potential leakage risks in the selected area of the northwest coast of Taiwan. The findings highlight the critical role of geological heterogeneities in influencing storage capacity and leakage risks, providing valuable insights for optimizing CO₂ storage strategies in complex subsurface environments.