Definition - What does Oil-Emulsion Mud mean?
Oil Emulsion Mud, also known as oil-water emulsion mud or oil in water emulsion mud is a type of emulsified mud used in the drilling operations which is formed when water is in a continuous phase and oil is in a dispersed phase. It is different from oil base mud in the fact that it has oil in the continuous phase and water in the dispersed phase.
Petropedia explains Oil-Emulsion Mud
An emulsion is the mixture of two or more substances which are normally not mixable with each other. In normal scenario when oil and water are brought in contact, oil being less denser than water floats on top of water, but when shaken vigorously, it forms an emulsion which can be used as a drilling fluid during oil well drilling operations. Emulsions consist of a continuous phase and a dispersed phase and the boundary between both these phases is known as the interface. Emulsions have cloudy appearance and are unstable and thus do not form spontaneously.
Oil-Water emulsion is a water base drilling fluid in which water is kept in large quantities and oil (maybe crude oil, diesel or synthetic liquids) are kept in very low quantities, just 2% to 5%. This is the reason for saying that water is present as a continuous phase (or in large amount) in such type of emulsion mud and oil is present in the dispersed phase.The benefit of using such drilling fluid or drilling mud is that because of low quantity of toxic synthetic base oil present in it, this type of drilling fluid is considered safe for the environment and passes the EPA static sheen test and mysid shrimp toxicity tests.