深水喷射扰动对表层导管承载力的影响规律

摘要

深水油气井表层导管下沉是深水喷射钻井作业面临的主要风险之一,喷射扰动对海底土承载力影响是导致表层导管下沉的主要原因.为保证建井及生产期间水下井口稳定,建立了考虑时间效应的表层导管承载力计算模型,并基于表层导管结构特征和喷射法安装表层导管技术特点,对表层导管承载力进行了实验研究.研究结果表明喷射施工参数对表层导管与海底土侧向摩擦力恢复影响明显:表层导管承载力随静置时间呈指数关系增长,表层导管喷射下入到位初期为摩擦力快速恢复期,随着时间增长,承载力增长速度减小;表层导管侧向摩擦力随着喷射排量、钻头伸出量的增大而急剧减小;钻头喷嘴完全伸出导管外部后,钻头伸出量对表层导管承载力影响减小.在深水表层导管设计与施工过程,充分考虑喷射施工参数及静置时间对表层导管承载力的影响,设计合理入泥深度,对于保证表层导管稳定具有重要意义.%Surface conductor sinking is one of the main risks in deep water drilling operations.Disturbance caused by jetting on bearing capacity is the main reason of surface conductor sinking.In order to ensure the subsea well-head stability during well construction and production process,a calculation model of surface conductor bearing ca-pacity considering time effect was established.Based on the structural features of surface conductor and jetting in-stallation technique,jetting experiments were carried out to study the bearing capacity of the conductor.The results show that jetting parameters have significant influence on the recovery of the friction force between the conductor and the surrounding seabed soil.The surface conductor bearing capacity increased exponentially with time.The friction force restores quickly in an interval immediately after the conductor is jetted down to the designed depth.And the bearing capacity increases with time,but the rate of increase gets slower with time.Friction force of the conductor is inversely proportional to the flow rate and bit-out.Influence of bit-out on the bearing capacity decreases once the bit nozzle is completely out of the conductor.In jetting operations,it is significant to select the appropriate jetting param-eters and take into account the time effect on bearing capacity to guarantee the stability of surface conductor.