Effects of Casing Program Change and Liner Tieback on Well Control

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 annulus 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 pressure 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.