Pore wetting is a principal control of the multiphase flows through porous media. However, the contact angle measurement on other than flat surfaces still remains a challenge. In order to indicate the wetting in a small pore, we developed a new pore contact angle measurement technique to directly measure the contact angles of fluids and gas/liquid/supercritical CO2 in micron-sized pores under ambient and reservoir conditions in this study, as well as the effect of chemical functional groups on pore contact angle.
The results indicate that the pore contact angle of a confined liquid in a glass capillary differs from the contact angle measured on a flat glass surface in an open space. Surface tension is not the only dominant factor on contact angle. The static contact angle in a glass pore also varies with glass pore size and liquid chemical structure. Viscosity and surface tension can significantly affect the dynamic pore contact angle. A new empirical correlation was developed based on our experimental data to describe the dynamic pore wetting.
The CO2 phase significantly affects the CO2-fluid contact angle in an oil-wet pore. Supercritical CO2-fluid contact angles are larger than gas CO2-fluid contact angles, but are smaller than liquid CO2-fluid contact angles. However, this significant CO2 phase effect cannot be observed in a water-wet pore.
