1. n. [Drilling Fluids]
Also known as isomerized olefin or IO, a synthetic hydrocarbon liquid made by the polymerization of ethylene, H2C=CH2. IOs are one of several synthetic fluids that have recently been used as base for synthetic-base muds and in other applications where refined oils might otherwise be used except for HSE concerns. IOs are linear structures that have their olefin double bond in the center of the chain length. They are made by isomerization of linear alphaolefins (LAO), which have their double bond at the end of the chain. Because the olefin bond is in the central area of the chain, the physical properties of IOs are different (for example, they are generally lower viscosity) compared with the LAOs from which they are made.