The present consumption of bentonite in the drilling operations in Nigeria alone is over 50 thousand tons per year and it is imported from abroad This trend is expected to continue as drilling activities keep increasing. The large consumption and the high importation cost of this material led to an attempt to find a local substitute. This work focuses on the possibility of utilization of local clay as a basic material for drilling fluids. This research evaluates, by means of simple but relevant laboratory tests, the properties of clay deposit from ishiagu-ivo local government area of Ebonyi state, southeastern Nigeria and compared with imported bentonite. The results were analyzed using statistical and graphical methods.Water-based mud was formulated from the local clay and the properties were determined and compared with those of imported bentonite. The results obtained showed that there were significant differences in the formulated drilling fluid’s rheological properties and the pH when compared with that of imported bentonite. When beneficiated with soda ash ( CO₃) and PacR at a concentration of 5.0g and 50g respectively to 350mL of the local mud, the mud pH increased from 5.65 to 10.60 while the apparent viscosity, yield point and plastic viscosity increased from 4.50, 4.00, 3.00 to 11.10, 10.00 and 7.00 respectively. With the addition of barite (BaS ) (10g) to 350mL of the formulated drilling fluid, the density increased from 8.80lb/gal to 9.15lb/gal. Therefore, at considerable concentration, the ishiagu-ivo clay exhibits good rheological properties that could compete favourably with that of imported bentonite when beneficiated with soda ash ( CO₃), potassium chloride and Pac R. This goes to show that a quality drilling fluid could be formulated from ishiagu-ivo clay that could meet the API specification.
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