Displacement of oil by a solution of an active and a passive additive
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A study is made of the frontal displacement of oil from a homogeneous porous medium by a solution of an active additive in the presence in the flow a component (referred to as the passive additive) that does not directly influence the ratio of the mobilities of the water and the oil but does interact with the active additive, changing its adsorbability and (or) its distribution between the phases . Such a situation arises when oil is displaced by solutions of surface-active substances and other reactants, whose effectiveness in application is significantly reduced by their adsorption by the porous medium (if the adsorbed matter itself does not reduce the mobility of the water, as in the case of the polymer in ). Under these conditions, it may be worth adding to the solution of the surface-active substance some cheap ballast substance that does not change the ratio of the mobilities of the phases but is capable of “taking away” from the surface-active substance some of the adsorption centers on the surface of the porous skeleton. Another example of a passive additive is provided by salts dissolved in water that influence the distribution of the active impurity between the water and the oil; this occurs in the case of displacement by carbonated water due to the dependence of the solubility of carbon dioxide gas in water on the mineralization of the water . In the present paper, an investigation is made of the structure of the displacement front, and a technique is developed for constructing a self-similar solution in the case when the adsorbability of the passive additive and its distribution between the phases do not depend on the concentration of the active additive.
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