Eficiência de recuperação de líquidos em tubos capilares por injeção de fluidos viscosos

Abstract

We analyze experimentally the displacement of immiscible liquids in capillary tubes. An important application is the oil recovery in porous media, in which use is made of injection fluid to increase the pressure in the reservoir and displace the oil that has not been produced with natural pressure. A capillary analysis is a simplified form and commonly used to approach the problem. Typically, due to the high viscosities of the fluids involved and the low travel speeds, these processes occur with negligible inertial effects, and thus, all tests are conducted at low values of Reynolds number. Scales involved in the process are very small which make the capillary forces extremely important. The capillary number is explored from very small values to its asymptotic limit. A very significant aspect of the problem is the effect of viscosity ratio on the mass fraction of oil not recovered during the injection of the removing liquid. Views of the interfaces of the bubbles formed between the removing liquid and shifted liquid are presented too, indicating a strong relationship of the instability with viscosity ratio. Given the same number of capillarity, the geometric fraction of residual mass mg increased with decreasing viscosity ratio, except for the lowest ratio of viscosities tested. Already the fraction of lost mass me calculated as the ratio between recovered and total mass or between the velocities decreased with decreasing viscosity ratio on the same capillary number. The existence of a nonuniform residual film over the bubble flow through the capillary tube can be associated with the non-concordance between the results.