INVESTIGATIONS INTO SURFACTANT FLOODING: WETTABILITIES AND CONTACT ANGLES.

The capillary and viscous forces hold back the residual oil in reservoirs. The capillary forces can be reduced by reducing the interfacial tension or altering the wettability. When the wettabilities in an irregular pore space for both phases of oil and water are equal, one has a contact angle of 90 deg and the capillary pressure of the oil/water interfaces is made. These contact angles (about 90 degree ) are observed for the surfactant systems in reservoir waters.