Commercially Imported Bentonite Versus Locally Derived Bentonitic Clays: A Comparative Assessment Study of Mineralogy and Geochemical properties, Anambra Basin, Southeastern Nigeria

This study aimed to investigate the mineralogy and chemical properties of the bentonites from the Imo Shale and Ameki formations, vis-a-vis commercially imported bentonite (CIC), for its suitability in formulation of drilling mud. 50 suspected bentonitic clays were studied, and properties of starting materials were utilized during screening. The CIC and four samples that met the API specification for drilling mud were subjected to X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses. XRD revealed SPL15 consists: 55% kaolinite, 20% quartz, 15% K-feldspar, and 10% hematite, suggesting kaolinite-type; and SPL6, SPL8, and SPL11 consist: 28-47% kaolinite, 26-32% quartz, and 12-20% nontronite, indicating smectite-type with significant amount of kaolinite co-existing, while the CIC consists of 12% quartz, 10% K-feldspar, 12% calcite, 41% nontronite, and 25% amorphous materials. XRF, showed Al2O3 (15.77-25.49) wt%, Fe2O3 (6.61-10.01) wt%, SiO2 (51.67-59.11) wt%, and loss on ignition (7.57-11.22) wt%, indicating variable degrees of alterations. Significant proportion of the CIC exists in an amorphous phase, suspected to be additives. Thus, comparison with the CIC revealed compositional disparity/deficits in the local clays. Consequently, treatment/beneficiations may be necessary to achieve the desired compositions. Based on these results, the primary criteria for the formulation of drilling fluid, using mineralogy and chemical compositions, are achievable.