Figure 3. Time-lapse shear-wave velocity anisotropy differences. Phase I) CO₂ injection occurred at the CVU-97 well with a prominent S-wave anisotropy anomaly detected to the south. Phase II) CO₂ injection occurred at the six offset injectors (indicated by triangles). In the case of the miscible CO₂-oil bank, the S₂ velocity increased and S₁ velocity decreased (purple), whereas, in the case of water injection, the change in effective stress causes the S₂ velocity to decrease and S₁ velocity to increase (blue).