隔水管注气双梯度钻井井筒参数计算研究

Research on Calculation of Riser Gas Injection Dual-Gradient Drilling Wellbore Parameters

基于隔水管注气双梯度钻井过程中隔水管环空多相流特性,建立了隔水管注气双梯度钻井环空多相流模型,采用有限差分法对模型进行求解,结合墨西哥湾某口深水井现场数据,分析了钻井参数对井底压力和环空压力的影响,并对注气流量的影响因素进行讨论.研究结果表明:隔水管注气双梯度钻井井底压力比常规钻井更低,更适用于海底窄密度窗口钻井;隔水管注气双梯度钻井在钻井过程中注气流量的大小对井底压力和环空压力影响较大;水深和钻井液密度是影响注气流量的两个重要因素.在隔水管注气双梯度钻井参数设计时,应选择合适的注气流量,且钻井液密度不宜过大,以确保隔水管注气双梯度钻井安全.该研究对隔水管注气双梯度钻井设计及现场作业具有指导意义.

Based on the characteristics of multiphase flow in riser annulus during dual-gradient drilling with riser gas injection, a multi-phase flow model for the riser gas injection dual-gradient drilling wellbore was established. The model was solved with the finite difference method and combined with the actual parameters of a deep water well in the Gulf of Mexico. The influences of drilling parameters on the bottom hole pressure and the annulus pressure, and the influence factors on the gas injection flow rate were discussed. The research results show that, the bottom hole pressure of dualgradient riser gas injection drilling is lower than that of conventional drilling, and is more suitable for subsea narrow-density window drilling;the magnitude of the gas injection flow rate during the dual-gradient riser gas injection drilling process has great effects on the bottom hole pressure and the annulus pressure, and the water depth as well as the drilling fluid density are 2 important factors influencing the gas injection flow. In the design of the dual-gradient drilling parameters for riser gas injection, the appropriate gas injection flow rate should be selected and the drilling fluid density should not be too large to ensure the safety of dual-gradient riser gas injection drilling. The research has guiding significance for the design of dualgradient drilling with riser gas injection and field operations.