1. n. [Drilling Fluids]

A mud additive used to lower interfacial tension so that trapped gas will readily escape from mud. Mechanical degassing equipment is commonly used along with defoamer. Octyl alcohol, aluminum stearate, various glycols, silicones and sulfonated hydrocarbons are used as defoamers.

Antonyms: foaming agent

Alternate Form: antifoam,  antifoam agent,  defoamer

See: aluminum stearate,  chemical barrel,  degasser,  fatty-acid soap,  gas-cut mud,  glycol,  interfacial tension,  octanol,  surfactant

2. n. [Well Workover and Intervention]

A chemical additive used to prevent the formation of foam during the preparation of a treatment fluid or slurries at surface. Excess foam created during the mixing process may cause handling and pumping difficulties and may interfere with the performance or quality control of the mixed fluid. Antifoam agents may also be used to break foams returned from the wellbore, following a treatment, in preparation for disposal of the fluids.

Antonyms: foaming agent

Alternate Form: antifoam,  antifoam agent,  defoamer

See: aluminum stearate,  chemical barrel,  degasser,  fatty-acid soap,  gas-cut mud,  glycol,  interfacial tension,  octanol,  surfactant