The aim of this study is to compare the performance of the multi-layer and the single-layer CO
2 injection methods used in offshore carbon capture and storage (CCS) through TOUGH-FLAC numerical simulations. Four key indicators, namely CO
2 saturation, pore pressure, vertical displacement,
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The aim of this study is to compare the performance of the multi-layer and the single-layer CO
2 injection methods used in offshore carbon capture and storage (CCS) through TOUGH-FLAC numerical simulations. Four key indicators, namely CO
2 saturation, pore pressure, vertical displacement, and Coulomb Failure Stress (
CFS), are employed as indices to assess the storage capacity of reservoirs and the mechanical stability of caprocks. Numerical simulation results show that the multi-layer injection method increases the CO
2 migration distance and reduces
CFS values compared with the single-layer injection method. After 1 year of injection, the combined CO
2 migration distance across two aquifers in Case 3 is 610 m, which is greater than that obtained using single-layer injection in Cases 1 and 2 (350 m and 380 m, respectively). Additionally, deep saline aquifers demonstrate superior CO
2 storage capacity due to higher overburden pressure, which also reduces the risk of caprock failures. After 30 years of injection, in Cases 1 and 2, the maximum
CFS values are 0.591 and 0.567, respectively, and the CO
2 migration distances are 2400 m and 2650 m, respectively. Overall, the findings of this study indicate that the multi-layer injection method, particularly in deep saline aquifers, provides a safer and more efficient CO
2 injection approach for offshore CCS projects.
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