Well Killing Parameters’ Design of Coiled Tubing

Abstract Coiled tubing downhole operation has the advantages of low cost and high efficiency. However, due to the lack of understanding of formation pressure or improper human operation, lick and kick often occur, which will cause blowout accidents in serious cases. Considering that only the coiled pipe exists in the wellbore, the coiled pipe can be used as a kill string for kill design and construction, but the coiled pipe has the characteristics of small pipe diameter and spiral section, which is different from the calculation of flow parameters of the conventional string, and if the pressure is not calculated properly during the kill process, it is easy to cause the failure of the killing. Based on the principle of dynamic equilibrium of wellbore pressure in the process of coiled tubing killing, this question establishes the coiled tubing reverse circulation driller method and engineer method kill model considering the characteristics of the coiled tubing surface spiral section, gas invasion gas expansion and flow pattern, and the model considers the influence of fluid flow circulation pressure loss on casing pressure and standpipe pressure during the well killing process and also considers the influence of overflow rising on the wellhead pressure. Based on the establishment of the model, the well kill parameters were calculated, the factors such as casing pressure, standpipe pressure, cyclic pressure consumption, and well kill time were analyzed, the coiled tubing kill method and kill parameters were optimized, and the coiled tubing kill process was built to provide theoretical guidance for coiled tubing killing.