Page 171 - Drilling Technology in Nontechnical Language

162 Drilling Technology in Nontechnical Language Second Edition

droplets that are completely surrounded by the oil. The droplets of brine
are held in an invert emulsion in the oil phase because they are coated by

emulsifiers (fig. 7–4). Emulsifiers are surfactants that have an organophylic
end and a hydrophylic end to their molecule. Each end aligns itself to be

in either the oil phase or the water phase so that the emulsifier molecule
forms a link between the oil and water.

Fig. 7–4. Emulsi ers around a water droplet

While the terms oil mud and IOEM have specific definitions, terms

such as oil mud and oil-based mud, among others, are interchangeable and
really define fluids where the continuous phase is oil. If water is present, it

is as an invert emulsion (water emulsified in oil). The presence of a water

phase in an oil mud allows for versatility in control of parameters such
as rheology.
Many different oils have been used in the past, including crude oil,

diesel oil, oils extracted from fish or plants, and synthetic oils. Some of

these oils are toxic, carcinogenic, and flammable (crude and diesel oils),
which are undesirable for safety, environmental, and health reasons.

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