ABSTRACT
Drilling fluids form the heart of the drilling operation. Drilling fluids play a role in the overall cost of drilling. This project work was undertaken to attempt in provide a substitute for foreign bentonite as a drilling mud, using local clay sourced from Onare Oviorie, Ethiope East Local Government Area, Delta State (Sample A) and Usen, Ovia South West Local Government Area, Edo State (Sample B). It evaluates and compares, by means of simple laboratory tests (such as mud density, viscosity, gel strength), the properties of the local clay sample and compared to the properties of the foreign bentonite. The results obtained showed a significant difference in the formulated drilling fluid’s mud density and rheological properties for each of the samples when compared with that of foreign bentonite. When beneficiated with 6.67 grams of barite, the mud density of Sample A increased from 7.5lb/gal to 8.5lb/gal while that of Sample B increased from 7.3lb/gal to 8.6lb/gal. With the addition of carboxymethyl cellulose, the apparent viscosity, plastic viscosity and gel strength (at 10 seconds and 10 minutes) increased from 2.5cp to 19.5cp, 2cp to 13cp, 3lb/100ft2 to 29lb/100ft2 (at 10 seconds) and 2lb/100ft2 to 25lb/100ft2 (at 10 minutes) respectively for Sample A, and from 3cp to20.5cp, 2cp to 14cp, 4lb/100ft2 to 30lb/100ft2 (at 10 seconds) and 5lb/100ft2 to 25lb/100ft2 (at 10 minutes) respectively for Sample B. Sample B was better than Sample A when compared, with higher values most of which fell within the API requirements. In comparison with the benchmark set by the foreign bentonite, it showed prospects in becoming a drilling mud.
