The adhesion of the oil to the rock surface is a phenomenon of practical importance in oil recovery operations. The forces responsible for the adhesion between oil and the rock surface will have to be overcome before the oil can be mobility to flow with the injected fluid_ If these forces are not overcome, only a fraction of the oil would be mobility and the rest would remain adhered to the rock surface. In other words, the recovery efficiency would be low within the zone swept by the injected fluid, be it water in a secondary waterflood or solvent in a miscible gas process.
Are the effects of oil-rock adhesion included in our current definition of reservoir wettability and its measurement techniques? Does the water-shielding phenomenon alone explain the effects of wettability on miscible flood performance? Is there experimental evidence for solvent retention due to the adhesion phenomenon? The present paper is directed to address these concerns and to seek a better understanding of the effect of this less well-known interfacial phenomenon on reservoirs mechanics. This paper aims to bring together pertinent literature from various fields of surface science such a.s contact angles, spreading, interfacial adhesion and reservoir wettability. Fundamental concepts, equilibrium relationships, laboratory techniques and their applicability are examined in the light of the recent experimental evidence.
Adhesion is such a commonly occurring natural phenomenon that we almost always take it for granted. We are all quite familiar with the experience of building sandcastles with moist sand, and not with totally dry or completely wet sand! Adhesion is natures's way of joining solid surfaces without any nails, screws or rivets. Adhesion is a fundamental force and it keeps nature together, neither too firmly nor too weakly. Adhesion manifests itself in many ways; for example, it keeps together the fibres in flowers, the cells in the animal body and the particles in minerals (Remberg, 1965). Other common examples of adhesion are the ice cubes sticking to the trays, ice sticking to the aeroplane wings, and the asphalt sticking to the paved roads. Thus adhesion progresses from being a minor inconvenience in the first case, to a major menace in the second, and to a necessity in the third
In spite of its wide occurrence and practical importance, the solid-liquid interface and the adhesion phenomenon still remain to be well understood. Granick (1991) notes that one reason for slow progress is simply that liquids in the bulk were traditionally studied by chemical physicists, while liquids at surfaces were studied by engineers. There was little interaction between these communities and their common problems tended to be neglected. Another reason is the paucity of experimental methods with which to probe this solid liquid interface that is buried between two condensed phases. This is starting to change and the field is developing rapidly both theoretically and experimentally through spectroscopic and diffraction investigations.
