Gas density in EOS2 is unrealistic(5000kg/m3)

Hello all:

    I set up a model to simulate CO2 displace water in core by EOS2 module. The inlet is CO2 mass inlet boundary condition, and the outlet is constant pressure boundary condition(10MPa). but the result shows that the gas density is very big (5090kg/m3) in some elements when the T=25℃ and P=10MPa(in this condition, the CO2 density should be 817.6kg/m3). I don't know what happen, and I tied ECO2N module under the same conditions, the result is realistic(820kg/m3). So I want to know what is wrong when using the EOS2 module.

    Thank you !