气侵钻井过程中井底衡压的节流阀开度控制研究

Research on the Throttle Valve Opening Degree Control to Keep Bottomhole Pressure in Balance When Gas Influx Occurs During Drilling Operations

基于钻井中的多相流控制体方程,建立了井底衡压的节流阀套压补偿控制模型,通过节流阀的实时调节可补偿气相滑脱压降,使井底压力与地层压力保持平衡.结果表明,气侵发现得越早,井底衡压控制越容易实现,气侵早期发现依靠井底气侵监测装置;当发现井底气侵时,大幅调节节流阀开度,使节流阀产生的套压快速平衡地层压力,此时根据井底欠压差的变化调节节流阀;随气体沿环空上移,微调节流阀开度,实时平衡气体滑脱产生的压降,此时调节节流阀依靠补偿控制模型;随气体循环出井口,环空中呈现0气流,节流阀开度及套压趋于稳定.

Based on the micro control body equations of multiphase flowfor drilling operation,a model for compensation balance control of back pressure was proposed to adjust the throttle valve in real-time through compensation for gas slippage pressure drop,which can maintain balance between bottomhole pressure and formation pressure. R esults showthat the earlier the gas influx is detected,the easier the balance of bottomhole pressure can be achieved. The early detection of gas influx relies on the downhole detection tools. W hen gas influx occurs in the bottomhole,the throttle valve opening degree should be adjusted sharply to balance the formation pressure rapidly with the back pressure. Adjustment of the throttle valve opening degree depends on the change of pressure difference in the bottomhole. As the gas migrates upwards along the annulus,the throttle valve should be adjusted slightly in real-time to balance the pressure drop generated by gas slippage according to the compensation balance control model. W hen the gas flowaway from the wellhead with the circulation,0 gas flowappears in the annulus,and the throttle valve opening degree and back pressure tend to be stable.