Abstract: Accurate identification of complex downhole conditions, such as kick, leakage, and their co-existence, is crucial for ensuring drilling safety. To address the unclear thermal response mechanisms under co-existing kick and leakage conditions, a fully transient wellbore-formation coupled heat transfer model is developed, taking into account enhanced convective heat transfer and variable mass flow induced by kick and leakage. Additionally, a detection method is proposed for co-existing kick and leakage conditions based on the wellbore-formation temperature distribution characteristics. The results show that changes in wellhead temperature can be used to distinguish between kick and leakage conditions, but are insufficient for directly identifying their co-existence. By further comparing bottom-hole temperatures with those under normal circulation conditions, upper leakage/lower kick and upper kick/lower leakage modes can be effectively differentiated. On this basis, the spatial distribution of annulus-drill string temperature differential along the wellbore enables the identification of the kick and leakage zones. Furthermore, the wellbore temperature distribution under co-existing conditions exhibits sensitivity to both the spacing between the kick and leakage zones as well as their respective flow rates. Specifically, higher kick rates correlate with higher annular temperatures. The proposed method provides valuable technical support for kick control and lost circulation prevention and plugging.

Key words: drilling, heat transfer model, wellbore-formation temperature distribution, co-existence of kick and leakage, downhole condition detection

摘要： 溢流、漏失及溢漏同存等复杂工况的准确识别是保障钻井安全的重要前提。针对溢漏同存条件下井筒温度响应机理不清的问题,考虑溢流与漏失引起的对流换热增强及变质量流动,建立了溢漏同存条件下井筒—地层耦合系统的全瞬态传热模型,并提出了一种基于井筒—地层温度分布特征的溢漏同存工况检测方法。研究结果表明:井口温度变化可用于区分溢流工况与漏失工况,但难以直接识别溢漏同存工况;进一步结合井底温度与正常工况的对比,可区分上漏下溢与上溢下漏两类溢漏同存工况;在此基础上,利用环空—钻柱温度差沿井深的分布特征,可实现溢流层与漏失层位置的判定。此外,溢漏同存工况下井筒温度分布对溢流层与漏失层间距及二者速率关系较为敏感,溢流速率越大,环空温度整体越高。研究成果可为溢流压井及防漏堵漏作业提供参考。

关键词: 钻井, 传热模型, 井筒—地层温度分布, 溢漏同存, 井下工况检测