Variations in the P-wave velocity with different porosities under different pressure and saturation conditions. The x-axis is the porosity, and the y-axis is the P-wave velocity. The triangle symbols represent a pore pressure of 8 MPa, and the star symbols represent a pore pressure of 15 MPa. The black, green, blue, and red colours represent the P-wave velocities associated with CO₂ saturations of 5%, 10%, 15%, and 20%, respectively.