FRANCIS D. UDOH AND ANIETIE N. OKON
Abstract
In a quest to provide a substitute for foreign bentonite as a drilling fluid in the oil and gas industry in Nigeria, local clay was obtained from Ewet-Offot, Akwa Ibom State, Nigeria. Water-based mud was formulated from the clay after its properties were determined and compared with those of bentonite, the clay of choice for drilling operations. The results obtained show that there was a significant difference in the formulated drilling fluids rheological properties and the pH values when compared to those of bentonite. This is as a result of low concentration of sodium cations (Na++) which hinders its swelling tendency as well as clay water attraction. When beneficiated with soda ash (Na2CO3) and sweet potato starch at a concentration of 5.0g and 50g respectively to 350mL of the local mud, the muds pH value increased by 70% from an initial value of 5.65 to 9.60 while the apparent viscosity, yield point and plastic viscosity increased by 229%, 200% and 250% respectively. With the addition of barite (BaSO4) content of 10g to 350mL of the formulated drilling fluid, the clay density improved by 7% from an initial value of 8.60lb/gal to 9.20lb/gal. Therefore, at considerable concentration, the Ewet-Offot clay exhibits good rheological properties that would compare favourably with those of bentonite when beneficiated with soda ash (Na2CO3) and sweet potato starch. Meaning, a possible drilling fluid could be formulated from Ewet-Offot clay.