A Numerical Study on the Thermal Behavior of Wellbores

The thermal behavior of a deepwater well was simulated by use of an existing mathematical model in which a rigorous flow-pattern-based multiphase-flow formulation is used to predict the pressure drop of the hydrocarbon stream. The heat-transfer model relied on the energy equation applied to the hydrocarbon mixture and on a radial thermal-resistance network between the wellbore and the formation. Different annulus-convection and thermal-formation models were evaluated. Production pressure and temperature results were compared with field data and with a commercial software package, showing good agreement with both. The model was able to capture important quantitative phenomena associated with the wellbore-heat transmission (e.g., lithologic column and annulus-fluid type). More specifically, the simulations showed that, for short production times, the heat transfer to the formation was significantly influenced by the wellbore-thermal resistances-namely, the cement sheaths and the nitrogen present in the production annulus. As the production time increased, the formation became the dominant thermal resistance.