1. n. [Drilling Fluids]
A test to determine the amount of clay-like materials in a water-base drilling fluid based on the amount of methylene blue dye absorbed by the sample. Results are reported as "MBT" and also as "lbm/bbl, bentonite equivalent" when performed to API specifications.
Synonyms: bentonite equivalent, MBT test
See: cation exchange capacity, endpoint, ion exchange, kaolinite, low-yield clay, titration, water-based mud