Theoretical study on coiled tubing velocity string completion technique in gas wells

According to the development need of coiled tubing techniques and equipment, a theoretical research on coiled tubing velocity string completion techniques is adopted, which is aimed at improving the completion efficiency and delaying the water breakthrough time. Combined liquid unloading by natural gas theory with wellbore multiphase flow theory and production performance analysis, this paper presents the theoretical basis and method to design of CT velocity string completion, discusses some existing problems in this process, and provides relevant countermeasures. Using the small diameter velocity string to accomplish the primary completion or the recompletion has much benefit for increasing the flowing velocity, preventing liquid loading, improving the breakthrough recovery, enhancing the lifting capacity, and insuring normal production of gas well. In the process of field completion design, it is necessary to consider the parameter optimization of CT string size, corrosion resistance, fatigue life, drag-reducing property besides the cost of settling velocity string itself, which affect the gas well production, so as to further improve the technique.