**Section 3** Technological Applications **111 Chapter 7 113** Application of Emulsions and Microemulsions in Enhanced Oil Recovery and Well Stimulation *by Mysara E. Mohyaldinn, Anas M. Hassan and Mohammed A. Ayoub* Microemulsions are self-assembled colloidal aggregates formed by a dispersed

phase and a continuous phase stabilized by a surfactant. These aggregates may or may not require the presence of a fourth component known as a cosurfactant.

Preface

**In Memoriam, Prof. Julio Casado**

These systems are of great interest from a chemical point of view because they facilitate the simultaneous presence of a hydrophobic environment and a hydrophilic environment, with which they have an important solubilizing capacity, distributing the solutes between the water, the organic phase, or in surfactant film depending on their physicochemical characteristics. For this reason, they have abundant and interesting applications in different fields such as solubilization or extraction. Likewise, depending on their biocompatibility, they can be used as vehicles for active principles and drugs, improving their adsorption and therefore

Therefore, and throughout this book, we will see important applications of microemulsions as chemical nanoreactors. In the first place, they can behave as microheterogeneous catalysts, where one can observe both an important catalysis, an effect of increasing the concentration of reagents in one of the domains of the system, and a perfect inhibition, due to the physical separation of the reactants when solubilized in different phases of the system. Thus, in the literature there are a large number of examples where microemulsions have been used as reaction media in chemical, photochemical, and enzymatic processes. Even microemulsions have been used as

In addition, the diameter of the microdroplets that form the dispersed phase can be modulated, so that the nanoreactor can be scalable. In this sense, microemulsions can be used to control the growth of nanocrystals or the diameter of

We must not forget the fact that they can be used to modulate mechanisms oriented

Last, but not least, it is necessary to underline a final characteristic: their ability to simulate complex biological structures. This makes microemulsions a valuable tool for biomimetic chemistry. Thus, microemulsions have been used as models of

Leaving aside the chemistry, at the same time that the adventure of editing this book began, on July 2, 2018, Professor Julio Casado died in Salamanca. For this reason, I want to use this prologue to pay tribute. Don Julio Casado-Linarejos was born in Palencia in 1939 and received his PhD in Chemistry from the University of Valladolid in 1965. After the defense of his doctoral thesis, he joined as a postdoctoral researcher with Professor Bak at the University of Copenhagen, establishing

biological membranes or as models of water trapped in restricted media.

on his return the first microwave laboratory in Spain.

their efficacy from a pharmacological point of view.

an alternative system to phase transfer catalysts.

nanoparticles.

to stereoselective synthesis.
