How Much Can You Extend the Reach of Coiled Tubing in Horizontal Wells Using Pressure-Hammer/Pulsing Tools

Abstract Coiled Tubing (CT) has been widely used in well drilling, completion and work over operations. A characteristic challenge with CT is its inability to reach far in horizontal wells. As the lateral length extends, CT's stability to reach working depth decreases due to friction. Excessive friction causes work string lock-up and motor stall. The pulse pressure generated by hammer/pulsing tools has been proven to help change the CT from static to dynamic friction, resulting in extended-reach capability. It is not clear as how much can the hammer/pulsing tools extend the reach of CT in horizontal wells. This creates a gap between the design and application of the tools. This paper fills the gap. An analytical model was developed in this project to predict the extended reach of CT in horizontal wells. The model considers pressure-induced piston effect, ballooning effect, and buckling effect on the elongation/shortening of the work string. The time-dependent elongation/shortening can change the work string from static to dynamic condition. Due to the fact that the dynamic friction coefficient is less than the static friction coefficient, it is expected that the released friction force would be translated to the extended reach of the CT string. Model analyses show that the elongation/shortening of CT string for a given CT/well/hammer condition is negligible in a certain range of depth, meaning that the given hammer/pulsing tool will not work in this range of depth. This theory is found consistent with data from wells with hammer/pulsing tool installations. This paper provides well drilling and completion engineers a handy technique to select hammer/pulsing tools for their applications in CT operations.