Surfactant Effects of Wettability Alteration and Low IFT on Countercurrent Imbibition for Tight Oil Formation

Abstract

Both wettability alteration and low interfacial tension (IFT) are important mechanisms of surfactants for enhancing oil recovery. In the imbibition process, surfactant solution invades the matrix, lowering IFT and altering the contact angle; these factors change the distribution of oil as well as the magnitude and direction of capillary force. Although a lot of research has been done in modeling countercurrent imbibition, less attention has been paid to comparing which effect plays a more important role in the imbibition process. A mechanistic model was used to study the surfactant solution imbibition process in porous media with subnanometer and nanometer capillaries, and the approximated diffusion coefficient was used to simplify the calculation. The simulated calculation demonstrates that, in contrast to low IFT, the change in wettability is the major mechanism for improving tight rock imbibition recovery, and this confirms that the change in wettability contributes more than lower IFT to the ultimate imbibition recovery.