Definition:
Methylene Blue Dye test (see comment)
Subject Area 1:
Mud engineering
Remarks:
The methylene blue dye test, MBT, is used to determine the cation exchange capacity of the solids present in a drilling mud. Only the reactive portions of the clays present are involved in the test and materials such as barite, carbonates and evaporites do not affect the results of the test since these
materials do not adsorb methylene blue. The cation exchange capacities of some typical clay are:
Clay CEC (meq/100g)
Wyoming Bentonite 75
Soft Shale 45
Kaolinite 10
Drilled Cuttings 8 – 12
For bentonite based mud systems the MBT provides an indication of the amount of reactive clays which are present in the drilling mud solids and for bentonite free, water based mud systems the MBT reflects the reactivity of the drilled solids. The test cannot distinguish between the type of
clays but, if a reactivity for the drilled solids is known or assumed it can be used to determine the amount of bentonite present in bentonite based systems.