Difference in pore contact angle and the contact angle measured on a flat surface and in an open space

Pore wetting is of importance to many industrial processes, such as microfluidics, petroleum engineering, CO2 storage and biophysical processes. Due to lack of measurement techniques, pore wetting has been estimated by using the contact angle measured on a flat surface. This may give misled the interpretation of multiphase flow behavior in porous media. In this study, the static contact angles of various liquids were investigated in single glass capillaries to indicate the difference between pore contact angle and the contact angle measured on flat surfaces. The liquids used are deionised water, 1-propanol, n-decane and crude oil. The glass capillaries used had a pore size range from 100 to 1000 mu m. The experiments were designed to consider the effects of glass pore size, surface tension and chemical structure of liquid on pore contact angle. The results indicate that the contact angle of liquids in a pore cannot be simply treated as 0 degrees which is commonly applied in literature. The static contact angle in glass pores varies with pore size and the applied liquids. When the pore size of glass capillary decreases from 1000 to 300 mu m, the pore contact angles of DI water, 1-propanol, n-decane and crude oil increase from 20 degrees to 30 degrees, 19 degrees to 39 degrees, 20 degrees to 26 degrees and 15 degrees to 20 degrees, respectively. The static pore contact angle of a liquid in a glass capillary is different from the contact angle on a flat glass surface. This indicates that the previous application of a contact angle on a flat surface to a pore medium case might be inappropriate for some cases. (C) 2014 Elsevier Ltd. All rights reseived.