无隔水管海底泵举升系统井底压力计算与分析

在无隔水管海底泵举升系统(riserless mud recovery system, RMR)钻井中，当钻井泵停止工作时，可能会发生U型管效应，而U型管效应的发生势必会导致井底压力处于不平衡状，发生溢流的概率将大大增加。为了能够在U型管效应发生期间，对井底压力进行控制，保持井眼稳定，通过建立RMR系统在停泵工况下的U型管效应环空返速数学模型，对RMR系统在该期间的环空返速和井底压力变化进行了模拟，分析了在恒定井底压力下海底泵入口压力和海底泵出口流量的变化规律。结果表明：海底泵入口流量越小，可调区间越大；钻井泵停泵前流量越大，维持井底压力恒定下的时间越短，钻井泵停泵前27、32、37、42 L/s时流量可调的截止时间分别为21、19、18、16 min。形成了适用于RMR系统在该期间进行井底压力控制的流量调节方法，为实际作业时的井控方法和操作提供了理论指导。

Calculation and Analysis of Bottom Hole Pressure of Riserless Mud Recovery System

When the drilling of the Riserless Mud Recovery System(RMR), the drilling pump stops working, the U-tube effect may occur. Therefore the U-tube effect will inevitably cause the bottom hole pressure to be unbalanced, and the probability of overflow will be significantly increased. In order to control the bottom hole pressure and keep the wellbore stable during the occurrence of the U-tube effect, this study was carried out. The established mathematical model of the annular return velocity of the U-tube effect of the RMR system under the pump shutdown condition was used to simulate the annular return velocity and the bottom hole pressure change under this condition and analyzed the variation of the annulus return velocity under the condition of the constant bottom hole. The variation law of the inlet pressure of the subsea pump and the outlet flow of the subsea pump under pressure. The results show that the smaller the inlet flow rate of the subsea pump, the larger the adjustable interval; the more significant the flow rate before the drilling pump stops the pump, the shorter the time to maintain the bottom hole pressure is constant. The cut-off time for the adjustable flow rate at 27 L/s, 32 L/s, 37 L/s and 42 L/s is 21 min, 19 min, 18 min, and 16 min, respectively. It can be seen that this study has formed a flow adjustment method suitable for the bottom hole pressure control of the RMR system during this period and provided theoretical guidance for the well control method and operation in actual operation.