Transient wellbore temperature prediction model of ultra-deep wells considering lost circulation

Abstract Accurately predicting wellbore temperature is critical to safe and efficient drilling in ultra-deep wells. With their narrow safe density window, ultra-deep wells are prone to lost circulation, yet conventional temperature models often overlook their impact on wellbore heat transfer. A transient wellbore-formation heat transfer model was developed in this study that explicitly accounts for lost circulation effects. This model is discretized and solved by employing the finite difference method. Validation against field measurements and existing models demonstrates that the predicted bottomhole temperature exhibits an error of less than 2%. Furthermore, the model elucidates the critical influences of lost circulation location, lost circulation rate, and circulation time on the temperature distribution, thereby providing theoretical and methodological support for precise temperature prediction in high-risk drilling operations.