Produced oilfield emulsions can be classified into three broad groups: The most common range of emulsified water in light crude oils (i.e., above 20☊PI) is from 5 to 20 vol%, and in crude oils that are heavier than 20☊PI is from 10 to 35 vol%. The amount of water that emulsifies with crude oil in most production systems can vary widely, ranging from 60 vol% (in rare cases). These droplets also will be widely dispersed, so that they have little chance to collide, coalesce into larger droplets, and settle.

The remaining water will be in minute droplets that have extremely low settling velocities. In an untreated emulsion, the density difference between the oil and the water will cause a certain amount of water to separate from the oil by natural coalescence and settling however, unless some form of treatment is used to accomplish complete separation, a small percentage of water probably will remain in the oil, even after extended settling. Others do not emulsify or form loose emulsions that separate quickly. Some form very stable emulsions that are difficult to separate. Ĭrude oils vary considerably in emulsifying tendency.

An encyclopedia of emulsion technology,.A comprehensive presentation and further basic information can be found in: There are several good general references available for more detailed and diversified discussions on crude oil emulsions. These emulsions must be treated to remove the dispersed water and associated inorganic salts to meet crude specifications for transportation, storage, and export and to reduce corrosion and catalyst poisoning in downstream processing facilities.Įmulsions occur in almost all phases of oil production and processing: inside reservoirs, wellbores, and wellheads at wet-crude handling facilities and gas/oil separation plants and during transportation through pipelines, crude storage, and petroleum processing. The problem is usually at its worst during the winter because of lower surface temperatures. Emulsions can create high-pressure drops in flow lines, lead to an increase in demulsifier use, and sometimes cause trips or upsets in wet-crude handling facilities. Emulsions can be difficult to treat and may cause several operational problems in wet-crude handling facilities and gas/oil separating plants. A regular oilfield emulsion is a dispersion of water droplets in oil. Produced water may be produced as 'free' water (i.e., water that will settle out fairly rapidly), and it may be produced in the form of an emulsion. Furthermore, crude oil must comply with certain product specifications for sale, including the amount of basic sediment and water (BS&W) and salt, which means that the produced water must be separated from the oil to meet crude specifications. The produced water must be:Īll these steps increase costs. The water creates several problems and usually increases the unit cost of oil production.

5.3 Droplet size and droplet-size distributionĬrude oil is seldom produced alone because it generally is commingled with water.

5 Characteristics and physical properties.

Oil in water emulsion examples