Transient prediction model for temperature in horizontal well drilling considering drill string and fluid dynamics

Accurately predicting temperature distribution in horizontal wells is essential for controlling bottom-hole temperatures and improving drilling efficiency. In this study, we developed a temperature field model based on energy conservation to examine the effect of frictional heat between the drill string and wellbore during horizontal drilling. The dynamic changes in the rheology of oil-based drilling fluids were also considered. Field data validated the model. The results indicate that frictional heat and fluid dynamics are critical factors in temperature prediction for horizontal wells. Findings also reveal that WOB significantly affects annular temperature distribution in the build section, whereas its effect on the vertical section is minimal. Increased rotary speeds enhance the frequency of contact between the drill string and wellbore, generating additional frictional heat and subsequently raising the annular fluid temperature. When WOB fluctuates between 50% and 200%, the associated change in bottom-hole temperature does not exceed 0.25%. When rotary speed adjusted within the range of 30% to 70%, it yields a temperature reduction rate of approximately 0.5%. The effect of various operational control parameters on the reduction of bottom-hole temperatures has been quantified. These parameters are ranked in terms of their effectiveness for temperature reduction as follows: inlet temperature > circulation rate > circulation time > drilling fluid density > WOB > rotary speed. These findings provide theoretical guidance for predicting bottom-hole temperatures and optimizing drilling strategies.