1. . 
A person responsible for testing the mud at a rig and for prescribing mud treatments to maintain mud weight, properties and chemistry within recommended limits. The mud engineer works closely with the rig supervisor to disseminate information about mud properties and expected treatments and any changes that might be needed. The mud engineer also works closely with the rig's derrickman, who is charged with making scheduled additions to the mud during his work period.
Synonyms: drilling-fluid engineer