The wettability of oil reservoirs is the most important factor controlling the rate of oil recovery, providing a profound effect on petroleum production. The petroleum industry has increased the research effort on wettability, but, so far, there has been limited coverage on the topic. Wettability reviews the major research and applications on wettability, capillary pressure and improved recovery. Critical topics including core preservation, the effect of wettability on relative permeability, surface forces such as van der Waals equation of state, petroleum traps and pore size effects are all included in this musthave handbook. Deciphering the techniques and examples will increase the efficiency and production of oil recovery, translating to stronger reservoir simulations and improved well production.