中文摘要：

为分析喷射下入导管过程中钻头与海底土相互作用情况,建立了导管下入过程中钻头的力学模型.根据射流理论和土力学的分析,得到了喷嘴射流力与土层临界破坏力的计算方法.研究结果表明,钻头与海底土相互作用力可分为直接作用力和射流作用力,只有当射流力较小时才有钻头直接作用地层的压力,排量是影响其作用力的主要因素.通过对现场实际案例计算,对比出施工过程中射流力与土层抗冲蚀力并得出了喷射下入过程中钻头距井底的高度.该研究成果能够结合具体海域的海底土特性,进行喷射过程中钻头及钻柱受力分析,为深水钻井喷射下入导管的钻井参数设计提供理论依据.

英文摘要：

In order to analyze the interaction between the drill bit and subsea soil during the pipe ejection and lowering, the me-chanical model of drill bit during the pipe lowering has been established. According to the analysis of jet lfow theory and soil mechanics, the calculation method for nozzle jet lfow force and critical destruction force of soil layer is gained. According to the research results, the interaction force between drill bit and subsea soil may be divided into direct acting force and jet lfow acting force. The drill bit pressure directly acting on the stratum exists only when the jet lfow force is small. The displacement is a main factor affecting the acting force. After the calculation of actual cases on site, the jet lfow force and anti- erosion force of soil layer during the construction, and the height from drill bit to downhole during the ejection are ifgured out. Such research results are capable of analyzing the drill bit and drill string stress during the ejection based on the subsea soil characteristics in the speciifc sea areas, and providing a theoretical basis for the drilling parameter design of pipe ejection of deepwater drilling.