OIL-RECOVERY BY IMBIBITION IN LOW-PERMEABILITY CHALK

This paper describes experimental studies of spontaneous imbibition of oil by water in a low-permeability outcrop chalk. At constant and hig h interfacial tension (IFT), the importance of capillary forces and th e existence of a predominantly countercurrent mechanism were establish ed. Additional experiments were performed to investigate the influence of length and of various boundary conditions. In another investigatio n, we modified the IFT at the sample boundary by using pairs of conjug ate phases of the n-hexane/ethanol/brine ternary system. Final recover y increased when IFT was lowered. We give a numerical interpretation f or this last result.