عنوان مقاله [English]
Nowadays, biopolymers are one of the most important parts of drilling fluids. Xanthan, a biopolysaccharide with high molecular weight, is produced from Xanthomonas campestris through fermentation processes. In this research, xanthan was produced from three strains of Xanthomonas campestris, b82, 1706DSMZ, SAM3301 and its application potential as a part of drilling fluid was evaluated. In a simultaneous study for decreasing the cost of final product, xanthan production was evaluated by one of these strains using sugar cane molasses. To study the efficiency in drilling fluids, these products were separately dissolved in fresh water, seawater (NaCl 40 g/L), saturated water (NaCl 400 g/L) and KCl 35 % (KCl 350g/L) in 0.5, 1 and 2 lbb concentrations and assessed before and after roll at 121°C. The best result was generally obtained using 2 ppb concentrations of biopolymers. Biopolymer produced by the strains b82 and SAM3301 showed the best efficiency according to high apparent viscosity (AV), Plastic viscosity (PV), Yield point (YP) and also increasing these parameters after role plus producing higher YP/PV ratio. The latter showed greater applicability because of its increased thermal stability and lower foaming. Xanthan sample produced using molasses had the best efficiency in sea water (higher YP/PV ratio), but its showed weaker properties than commercial xanthan (XC).