In a large Saudi Arabian field, water/oil-emulsion problems increased dramatically during the 1990＇s. Water/oil-separation problems increased incidents of shorting in the separator, tripping of equipment, and increased demulsifier usage. In a comprehensive study, watercut, temperature, shear, asphaltene content, demulsifier dosage, and mixing of different crude oils were quantified with a new water-/oil-separation index developed to measure emulsion stability. The results showed a strong correlation of asphaltene content in the crude oil with the water-/oil-separation index, or emulsion tightness.