Numerical analysis of heat transfer rate and wellbore temperature distribution under different circulating modes of Reel-well drilling

Abstract

Reel-well drilling is a new method of ultra-deep well drilling, but the wellbore temperature distribution is not yet well understood. In this paper, considering the wellbore flow characteristics and heat transfer mechanisms under multiple flow channels and two circulating modes in Reel-well 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 resulting from the fluid transition in different flow channels. The model was solved using the finite difference method and validated using field measured data. The results indicate that 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. And the bottomhole temperature of the latter was eventually more than 30 °C lower than that of the former, indicating that the latter was favorable for drilling in ultra-high temperature formations. Additionally, except of the dual-channel valve position under circulating mode A, the dual-channel valve position and inlet temperature had little effect on the bottomhole temperature, not exceeding 10 °C.