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The present investigation is mainly concerned with the study of certain viscosity effects on the mechanism of liquid-liquid miscible displacement in consolidated porous media. In the past relatively little attention has been directed toward miscible displacement studies in which the viscosity ratio is kept constant but the viscosity levels of the liquids involved are varied. Similarly, little information is available on the effect of anomalous mixture viscosity behavior on miscible displacement (i.e., the shapes of the viscosity-concentration curves).
Apart from the above, a study was also conducted of the gravity effects and of the growth and behavior of instabilities formed under conditions of an adverse viscosity ratio. A relatively simple technique for obtaining the concentration profiles along the length of the core was developed for this purpose.
It was found that in miscible displacements conducted at a given favorable viscosity ratio the viscosity levels of the liquid pairs involved have a marked effect on the breakthrough efficiency and the transition zone length. The pairs of liquids for this study had similar viscosity-concentration curves. For the unfavorable case on the other hand, the effect was found to be relatively unimportant.
An analysis of the anomalous mixture viscosity behavior applied to the transition zone showed that such mixture behavior may be used to explain some of the results obtained for certain liquid pairs. For instance, the presence of a pronounced maximum or minimum in the viscosity-concentration curve affect the length of the transition zone. Similarly, the effect of reversing the order of displacement in cases of viscosity ratios near unity should be critically examined in the light of the viscosity-concentration curves.
Concentration profiles along the length of one of the cores were obtained at various times during displacement for both favorable and unfavorable viscosity ratios. In the case of favorable viscosity ratios, these results seem to support the view held by some investigators that small viscous fingers tend to stabilize with an increase in the distance traversed in a consolidated porous medium.