This book contains a research work which adopted Factorial Design technique together with API Specification for testing and procedures so as to provide great flexibility for exploring or enhancing the treatment of local clay and formulation of water based mud drilling in diverse ways in oilfield services. Moreover, the models developed from this research devised means of evaluating each main effects and interactions effects on the treatment of local clay so as to determine the best required treatment for the local clay and thereby optimize the whole process in order to produce the best drilling fluid formulation. This models developed has also been confirmed to be a means of saving time, cost and rigorous procedures in the laboratory in the process of obtaining drilling mud flow properties.