Numerical Analysis of Heat Transfer Rate and Wellbore Temperature Distribution Under Different Circulating Modes of Reelwell Drilling

This paper aims to investigate the wellbore thermal behaviors in reelwell drilling. Combining the flow characteristics and heat transfer mechanisms in reelwell drilling, an integrated transient heat transfer model was developed for distinct thermal-associated regions based on the first law of thermodynamics. The model also coupled the variable temperature-mass flow resulted from the fluid transition in different flow channels. The model was solved using the finite difference method and validated using field measured data. The heat transfer rate and wellbore temperature distribution under two circulating modes were investigated comparatively. The results indicate that the radial heat exchange rate was always opposite to the axial heat convection rate in each flow channel, and they were approximately axisymmetric to the zero line when the wellbore temperature tended to a steady state. Additionally, the combined effect of heat transfer mechanism, temperature difference and flow rate difference resulted in the temperature relationship under circulating mode A satisfying: FC1 > FC3 > FC2, while that under circulating mode B showing: FC1 > FC2 > FC3. Moreover, the bottomhole temperature under circulating mode B was always significantly lower than that under circulating mode A, indicating that the former was favorable for drilling in ultra-high temperature formations