Heating of heavy oil by circulating hot waterin closed double casing in ultra-deep wells

In heavy oil production, the loss of energy to ambient surroundings decreases the temperatureof the heavy oil flowing upwards in a vertical wellbore, which increases the oil viscosity and the oil maynot flow normally in the wellbore. Therefore, it is necessary to lower the heavy oil viscosity by heatingmethods to allow it to be lifted easily. Heating of heavy oil in an oil well is achieved by circulating hotwater in annuli in the well (tubing-casing annulus, casing-casing annulus). In this paper, based on heattransfer principles and fluid flow theory, a model is developed for produced fluids and hot water flowingin a vertical wellbore. The temperature and pressure of produced fluids and hot water in the wellboreare calculated and the effect of hot water on heavy oil temperature is analyzed. Calculated results showthat the hot water circulating in the annuli may effectively heat the heavy oil in the tubing, so as tosignificantly reduce both oil viscosity and resistance to oil flow.