Exploration and practice on well killing by coiled tubing in Tarim Oilfield

Tazhong I gas field of Tarim Oilfield is a typical deep carbonatite gas field of high temperature and high content of sulphur. While the string was run back after completion of Well S, the float valve at the bottom of completion string failed and the trapped pressure was released instantly, leading to high casing pressure at wellhead after well flow. This well had high casing pressure and not much down-hole string, and well killing by forward squeezing could not squeeze kill fluid into the wellbore, so conventional well killing methods could not be executed. By demonstrating the well kill method using coiled tubing, field tests on coiled tubing flow and emergency drill on well killing, the feasibility of well killing with coiled tubing was proved. Through careful well killing using coiled tubing, the problem of high casing pressure at overflow was safely addressed and the well was killed successfully, providing a new reference method for well killing jobs under special cases.