Investigating the Effects of Contaminants on the performance of Mineral Oil Based Versathin Dispersant

Abstract Flocculation occurs when particles in the drilling fluid agglomerate due to particle to particle attraction thus leading to uneven distribution of weighting material within the fluid. Dispersants majorly are used to deffloculate fluids that have these tendencies, and their performance lies in the ability to minimize sagging and hence control drilling fluid rheology(Yusuf et al). This work was undertaken to investigate the effect of clay and sea water (containing calcium and magnesium ions) contaminations on dispersant performance used in an oil based invert emulsion drilling fluid system. Barite (Ba2SO4) was used as the weighting agent; the based fluid used for the oil based invert emulsion mud was EDC-99, a specialized kind, different from the conventional diesel oil.The fluid were analysed before and after aging using, rheometer, filtration and emulsion stability tests. The dispersant employed for the fluid system was Versathin ®. Versathin is an oligomeric fatty acid in mineral oil, an oil-based dispersant which tend to also perform excellently in the invert emulsion system. From the experimental results, a general decrease in fluid rheology was observed in the dispersant sample as compared with the blank sample. The emulsion stability of the fluid decreased as contaminants were added, fluid loss increased when contaminants were added to the dispersant samples. Contaminations also increased the plastic viscosity and yield point for the dispersant sample but all were still within the API range. Increase in LSYP in the presence of sea water and clay revealed that sag may be less noticeable when drilling reactive formations, confirming earlier studies on water based mud and the suitability of clay as rheology controllers. Cumulatively the result shows that Versathin oil based dispersant can control flow behaviour of fluids when employed in the oil based invert emulsion system.