井身结构变化及尾管回接对井控的影响分析

Effects of Casing Program Change and Liner Tieback on Well Control

在深井井身结构设计中,为了解决悬挂尾管后继续钻进是否需要进行尾管回接的问题,建立了钻遇高压气层发生气侵时的环空气液流动模型,模拟了井筒横向尺寸变化对环空气液两相流动规律的影响,分析了不同尾管悬挂深度下气侵过程中的井底压力、钻井液增量、监测到一定钻井液增量所需时间的变化规律,以及压井过程中套压峰值和套压峰值到达时间的变化规律。结果表明:尾管回接改变井身结构后,随着尾管悬挂深度的减小,井底压力和钻井液增量剧烈变化阶段先提前后延迟;尾管回接到井口后,溢流发现时间比尾管不回接时要短,有利于溢流的早期发现;在相同溢流量条件下关井,尾管回接到井口后的压井套压峰值比尾管不回接时大;套压峰值到达时间变化不显著。

In the casing program design for deep wells, whether liner should be tied back is not clear when drilling continues after cementation. A computing model was established to calculate the wellbore an- nulus pressure when gas invasion occurs in high pressure gas reservoirs, and the impact of casing size on the annulus two-phase flow. From the point of well control, the bottom hole pressure, mud volume increment, and time needed to detect drilling fluid increment, peak of casing pressure and time to reach the peak pres- sure were analyzed during gas kick and well killing process. The results showed that： as the liner hanger depth decreased the dramatic change stage of bottom hole pressure and mud volume increment advanced first and then delayed;the discovery time of gas kick after liner was tied back to the wellhead was shorter than when the liner was not tied back; the casing pressure peak was higher when the liner was tied back to wellhead than when the liner was not tied back; but the change in peak casing pressure arrival time was not obvious. Therefore, tie-back liner was conducive to the early detection of gas kick under the condition of safe killing.