The viability of using re-refined used lubricating oil (RULO) extracted with an aromatic selective normal methylpyrolidone (NMP) as base oil for the formulation of drilling mud was investigated. The rheological and other properties of this formulation were compared with formulations from three locally produced synthetic base oils. The synthetic base oils were Paradril® made from saturated linear ethylene polymer, Emcaid® manufactured from a blend of olefin isomers and Ty-Chem-Low Tox® made from catalytic dimerization of linear alpaolefins. RULO based mud, though alkaline in nature with a pH of 8.5 exhibits very poor filtration properties with the thickest filter cake when compared with the other formulations. It is also the least stable of the four formulations with an electrical stability (ES) of 480 volts. RULO formulation is very toxic as the cassava plant on which it was spilled survived for only 5 days compared to 15 days for Paradril®. It is therefore, not environmental friendly and may not also be cost effective as the cost of re-refining and extraction may far exceed the cost of producing synthetic base oil. RULO may not therefore be a viable alternative to existing base oils for the formulation of drilling mud.
Key words: Used lubricating oil, base oil, drilling mud, rheological properties, emulsifier, environment
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