Coupled effects of swirl flow and drill-string vibration on deepwater wellbore temperature and cooling optimization

Accurate prediction of the wellbore temperature field in deepwater drilling is essential for operational safety. A few existing studies have considered the coupled effects of swirling flow and drill-string vibration, making it difficult to accurately characterize the downhole thermal environment. Based on wellbore heat transfer and drill-string dynamics, with the coupled effects of drill-string rotation–vibration accounted for, a transient heat-transfer model for deepwater drilling was developed. The sensitivity of bottom-hole temperature (BHT) in deepwater drilling to various factors was evaluated using a Plackett–Burman (P–B) screening design, followed by the proposal of targeted cooling methods. Compared to DRILLBENCH and models ignoring coupling effects, this model predicts annular temperatures closer to actual conditions, with a relative error of 1.02%, demonstrating higher accuracy and improved stability. An optimal insulation coating thickness can reduce BHT by up to 23 °C. Additional methods, such as adjusting the drill string rotation–vibration coupling factor and increasing fluid displacement, can lower BHT by 5–7 °C. The effectiveness of surface cooling methods exhibits pronounced diminishing marginal returns, with cooling capacity becoming increasingly limited as depth increases. Given the limited efficacy of individual cooling strategies, an integrated approach that combines multiple methods is recommended to achieve effective wellbore temperature reduction. The efficiency of surface-based cooling exhibits pronounced diminishing marginal returns. As well depth increases, its cooling capacity becomes increasingly limited. Given the limited effect of a single method, it is recommended to integrate multiple cooling techniques to effectively reduce wellbore temperature. The research results provide practical guidance for predicting and controlling wellbore temperature in deepwater drilling.