Methods of treating hydrocarbon fluids to reduce the apparent viscosity of hydrocarbon fluids encountered in petroleum operations and reducing deposits within a well annulus or a pipeline are disclosed. The method comprises contacting such fluids with a hydrophobically modified polysaccharide to create water external emulsions. The disclosed hydrophobically modified polysaccharides have been demonstrated to reduce interfacial tension to below 65 mN/m and thereby improve the transportability of inherently viscous hydrocarbon fluids, such as heavy crude oils.