derrickman — Oil & Gas Glossary
The member of the drilling crew in charge of the mud-processing area during periods of circulation. The derrickman also measures mud density and conducts the Marsh funnel viscosity test on a regular basis when the mud is circulating in the hole. The derrickman reports to the toolpusher, but is instructed in detail by the mud engineer on what to add
Detailed Explanation
to the mud, how fast and how much. His other job is to handle pipe in the derrick while pulling out or running into the hole.