Thermodynamic calculation on multiple fluid in thermal recovery wellbore

Aimed at the issues of the small platform space, high operating cost and difficult implementation of conventional thermal producing in offshore oil field, the multiple thermal fluid huff and puff technique was researched. The mathematical models for multiple thermal fluid flow and heat exchange in wellbore during the injection were established on the basis of two phase flow theory and heat transfer principle. The flow features and heat exchange rules of the mixture in wellbore were analyzed, and the effects of injection pressure and temperature on the pressure, temperature and steam quality of the mixture in the wellbore were discussed. The effect of different proportion of multiple thermal fluids on the temperature of the mixture flow was also discussed. The results showed that in the injection process, the rise and fall of pressure in wellbore depended on the gravity pressure drop and the friction pressure drop, and the fluctuation of temperature depended on the rise and fall of saturated steam partial pressure, with steam quality descending. If other conditions remain unchanged, reducing the injection pressure would increase the temperature at the bottom of the well and improve export steam quality at wellhead. Increasing nitrogen proportion, bottom temperature drop would become faster in the condition of constant total amount of nitrogen and carbon dioxide.