During the development of gas reservoirs, most gas wells experience a gradual decline in production over time, eventually leading to shutdown. There are numerous factors contributing to this issue, including declining reservoir pressure, water ingress, reduced gas flow rates, bottomhole liquid accumulation, and increased liquid volumes. Once liquid accumulates in a gas well, it results in continuously increasing bottomhole liquid column backpressure, leading to elevated bottomhole flow pressure, reduced production pressure, and a significant decline in production. At this point, effective liquid removal measures must be implemented to maintain normal gas well production. Commonly used processes include gas-lift drainage and foam drainage; however, regular liquid removal operations for gas wells can be highly costly. The function of the velocity tubing string is to lower a smaller-diameter continuous tubing into the original production tubing to serve as the production tubing. When gas flows into the continuous tubing, the reduced cross-sectional area compared to conventional production tubing causes the gas flow velocity to increase based on the principles of variable-diameter tubing fluid mechanics. This high-velocity fluid has a strong carrying capacity for bottomhole liquid, effectively delaying the onset of water ingress in the gas well. This enables prolonged normal production.
