深水高温高压气井钻井循环温度压力耦合计算与分析

Coupling calculation and analysis of circulating temperature pressure distribution in deepwater HTHP gas well drilling

深水高温高压气井钻井过程中,井筒大温差、大压差效应会使钻井液性能发生较大改变,进而影响井筒流动参数和钻井施工安全,因此准确模拟井筒温压场对确保深水高温高压井安全钻进至关重要。根据深水钻井工艺和高温高压地层的特点,充分考虑了井筒温压场和钻井液性能相互影响,结合增压管线流体进入隔水管环空引起的传热和传质,建立了适用于深水高温高压气井钻井的井筒瞬态温度压力耦合计算模型,提出了相应的迭代求解算法,并通过实例计算,进行了参数敏感性分析。研究结果表明:本文模型计算值与现场实测数据基本吻合,验证了模型的正确性;隔水管增压管线排量会使环空温度显著降低,进而影响整个井筒温度,因此不可忽略增压排量的影响;钻井液性能受井筒温度和压力影响较明显,在计算过程中忽略温度,压力和钻井液性能之间的耦合作用会产生较大误差。本文研究成果可为深水高温高压气井钻井过程中井筒温压场预测及水力参数设计提供理论指导。

In the drilling process of deepwater HTHP gas wells, the large temperature difference and large pressure difference effect of the wellbore will greatly change the drilling fluid performance, and thereby affect the wellbore flow parameters and drilling safety. Therefore, accurate simulation of the wellbore temperature and pressure field is crucial to ensure the safe drilling of deepwater HTHP wells. According to the characteristics of deepwater drilling process and high temperature and high pressure formation, a new transient temperature-pressure coupling model for deepwater HTHP gas wells is developed by giving full consideration to both the interaction effect between wellbore temperature-pressure field and drilling fluid performance and the heat and mass transfer caused by boosting mud invading into the riser annulus. The corresponding iterative algorithm is presented, and the parameter sensitivity analysis is carried out through several case studies. The results show that the calculated results of the model are in good agreement with the measured data, which verifies the correctness of the model. The riser boosting rate can significantly reduce the annulus temperature, thus affecting the entire wellbore temperature. Hence, the influence of the boosting rate cannot be ignored. Drilling fluid performance is significantly affected by wellbore temperature and pressure. Therefore, if the coupling effect between temperature, pressure and drilling fluid performance is ignored in the calculation process, a large error will occur. The research conclusions of this paper can provide theoretical guidance for the wellbore temperature and pressure field prediction and hydraulic parameter design in the drilling process of deepwater HTHP gas wells.