Group and elemental compositions and structures of hydrocarbon dispersions in super-viscous oil resulting from steam and heat exposure at 140-190 degrees C and 3-6 atm in the presence of hexane and benzene are established using simplified models of terrigenous and carbonate reservoirs. A relationship between the composition and structure of the oil dispersions after steam-heat action and a temperature dependence of viscosity are established. Solvate shells of increased thickness around complex structural unit nuclei and a greater proportion of dispersion medium are distinctive features of the low-viscosity displaced oil. Studies show that the dispersion medium impacts greatly the formation and properties of the oil dispersion. Benzene in the displacing agent decreases the degree of dispersion of the system and the viscosity of the displaced oil.