中文摘要：

针对深水喷射下表层导管工艺设计中选择钻头伸出量时无理论模型依据、存在作业盲目性和风险性的问题,通过理论推导和现场试验,建立钻头伸出量计算模型,为合理钻头伸出量的设计提供理论依据。通过理论分析,假设钻头水眼喷射出的射流束上边缘与表层导管下边缘内侧相切时钻头伸出量最优,根据这一假设推导出了合理钻头伸出量的计算公式,通过现场试验验证了理论假设的合理性和计算模型的正确性。现场试验结果表明：导管下入速度与钻头伸出量呈正相关,导管与周围土体的摩擦力恢复与钻头伸出量呈负相关。将计算模型应用于南海12口深水井的钻井作业,取得了良好的应用效果,平均每口井节约作业时间14.96 h,提高了作业时效,并达到了安全作业的要求。

英文摘要：

In view of the absence of a theoretical model for choosing the bit stick-out in deepwater conductor jetting operation, and the existing operational blindness and risks, a bit stick-out calculation model was built up fllrough theoretical derivation and field tests to provide the theoretical basis for the design of reasonable bit stick-out. Theoretical analysis assumes that bit stick-out is the best when the upper edge of the jet flow sprayed from the bit nozzle tip is internally tangent to the lower edge of surface conductor, based on which a formula to calculate the reasonable bit stick-out was derived, and the rationality of the theoretical assumption and correctness of calculation model were proved through field tests. Field test results show that the conductor running speed is in positive correlation with bit stick-out, while the restoration of friction between the conductor and surrounding soil body is in negative correlation with bit stick-out. The calculation model was applied in the drilling operation of 12 deepwater wells in the South China Sea and got good application effects. It saved 14.96 h per well on average, enhanced operational efficiency, and met the safety requirements at the same time.