Evaluation of the Rheological Properties of Ire-Ekiti Clay as an Alternative Viscosifier to Bentonite

Abstract Bentonite is an inevitable material in the formulation of drilling fluids. Sourcing for commercial bentonite in Nigeria is largely dependent on the cost of importation that is highly unstable. Consequently, there is the need for the Nigerian oil and gas industry to find a substitute for commercial bentonite as the base viscosifier of drilling fluid. This work has been carried out to evaluate the rheological properties of Ire-Ekiti clay as an alternative viscosifier to bentonite. An indigenous clay (kaolinite) sourced in Ire-Ekiti, Ekiti State, Nigeria was beneficiated and modified to attain API characteristic properties similar to the commercial bentonite in the formulation of water-based mud. The kaolinite water-based mud was formulated using clay particles of 63- and 150-microns sieve sizes. The mud was characterized at varied reservoir temperature ranging from 30 to 80 °C at an interval of 10 °C, and the physiochemical and rheological properties were determined and compared with commercial bentonite water-based mud. The findings of the kaolinite water-based mud showed pH of 11.02, density of 8.64 ppg, which compared very well with those of the commercial bentonite water-based mud. On rheology of the beneficiated kaolinite water-based mud, the sand content was found to be 1.0%, while the marsh funnel viscosity, apparent viscosity and water loss between 30 °C and 80 °C temperature range were obtained to be 58 to 55 seconds per quartz, 22 to 20 cP and 8.4 to 12.0 mL, respectively. The effect of particle sizes of the kaolinite water-based mud on marsh funnel and apparent viscosities revealed a proportional increase pattern, while in the case of water loss, an inverse relationship was observed. The best outcome in-line with API standards was achieved using 150 microns sieve size. Therefore, the beneficiated kaolinite clay of Ire-Ekiti has been discovered to have physiochemical and rheological properties adequate and sufficient to replace the commercial bentonite.