Fundamentals of Wettability
Originally Posted on Schlumberger Website
Understanding formation wettability is crucial for optimizing oil recovery. The oilversus-water wetting preference influences many aspects of reservoir performance, particularly in water flooding and enhanced oil recovery techniques. Making the assumption that a reservoir is water-wet, when it is not, can lead to irreversible reservoir damage.
Wetting forces are in play all around us. They have practical applications, such as making rain bead up on a freshly waxed car so it is protected from rust. And they provide whimsy: wetting forces bind sand grains to hold the shape of a child’s sand castle.
Forces of wetting influence hydrocarbon reservoir behavior in many ways, including satura – tion, multiphase flow and certain log interpre – tation parameters. However, before getting into these details, it is best to first establish what wettability is.
Wettability describes the preference of a solid to be in contact with one fluid rather than another. Although the term “preference” may seem odd when describing an inanimate object, it aptly describes the balance of surface and interfacial forces. A drop of a preferentially wetting fluid will displace another fluid; at the extreme it will spread over the entire surface. Conversely, if a nonwetting fluid is dropped onto a surface already covered by the wetting fluid, it will bead up, minimizing its contact with the solid.