I am conducting a CO2-water coreflooding experiment. I found that when I inject CO2 as gas phase into sandstone core sample to displace water, the total volume of CO2 and water produced is always higher than the injected volume of CO2. However, when I inject CO2 in liquid phase, the injected and the produced volumes are the same. Please keep in mind that the system has some dead volume of water and there is a temperature difference between the sample and where we measure the volumes.

Thank you in advance for your help