Bentonite used during drilling and cementing operations in Nigeria are imported into the country despite the availability of this raw material, which will increase the Gross Domestic Products (GDP) of this country if properly processed and utilized instead of imported bentonite. This investigation evaluated the performance of three selected Nigerian bentonites sourced from the South-Western part of Nigeria for oil well-cementing operation. The raw and beneficiated samples from each location were prepared and characterized using X-ray Fluorescence (IVT-20 XRF) to determine the elemental composition of each sample pre and post beneficiation. The beneficiated sample with properties close to that of Wyoming bentonite was chosen for the oil well cement slurry analysis. The measured parameters used in the analysis of the suitability of local samples used in oil well-cementing operation were compressive strength and rheological properties. Box-Behnken Design (BBD) was used for the study of the optimum quantity of bentonite required for cementing specification and bi-optimization values for both the comprehensive and rheological properties. The results of this investigation showed that all local clay samples in raw form failed the specification of the American Petroleum Institute (API). After beneficiation, Ibeshe Bentonite (IB) had the highest sodium content and the ratio of the exchangeable cations, 190% increment in sodium-ion was recorded in IB after beneficiation and the slurry yield of IB (2.7 ft³ per sack) was greater than that of Wyoming Bentonite (1.9 ft³ per sack) when both are subjected to the same experimental condition. Bi-optimization models predicted optimum experimental conditions with an accuracy of between 0.35% and 1.26% for both comprehensive and rheological parameters.