深水压井节流管线内的气体交换效应分析

深水井控中压井节流管线细长,地层侵入气体进入节流管线内会产生气体交换效应,导致节流压力发生变化,增大了深水井控的难度。应用多相流动模型通过数值计算和实例模拟,从不同角度分析了深水压井节流管线内的气体交换效应,得到节流压力的变化规律。模拟发现,深水压井时节流管线内气体体积分数变化大且迅速,气体交换效应明显;节流压力随着循环流量的增大而降低,且变化幅度随着循环流量增大而增大,随着钻井液池增量的增大而增大;同样钻井液池增量下,钻进、停钻、起钻时对应的节流压力依次升高;深水压井过程中节流压力比陆地井控节流压力变化快;节流管线直径越小,节流压力初始值越低,峰值越高,节流压力变化越大,节流管线内气体交换效应越明显。研究结果可以更好地指导深水钻井压力控制。 

Analysis on Gas Exchange Effect in Choke Line with Deepwater Well Killing

In deepwater well control,gas exchange effect might happen when invading gas from formation flows into long and thin choke lines,which can affect the value of choke pressure significantly and increase the difficulty of well control.Therefore,it is very important to study the issue.The gas exchange effect occurring in choke lines and the choke pressure change caused by this effect were studied from different aspacts with numerical simulation and case study based on multiphase flow model.The simulation indicates that gas volume fraction in choke lines varies largely and rapidly and gas exchange effect is obvious during deepwater well killing;the value of choke pressure decrease as circulation volume increases and the changes of this value rise with the increase of circulation volume;choke pressure goes up with the rise of pit gain;choke pressure of standby is larger than the choke pressure while drilling,and choke pressure while tripping was higher than that of standby;the choke pressure during deepwater well killing would change faster than that onshore;the smaller the choke line,the lower the initial choke pressure,the higher the peak value and the larger variation of the choke pressure,and the more apparent the gas exchange effect in choke line.