The experimental design applied used a Response Surface Design (RSM), which involved 24 (2-Level, 4-Factors) to generate statistical models, and analyze the dataset. 
RSM
The beneficiation of the clay using sodium carbonate and Kelzan® XCD polymer ensued in an improvement in the rheological properties of the formulated drilling mud. 
Kelzan
The rheological properties of interest, which forms the response variables, were selected based on the API specification 13-A for drilling grade bentonite.  These properties were comparable with the API specification 13-A for drilling fluid materials.
API