Velocity-string unloading process for an offshore gas well
A velocity string creates a smaller production path inside the original tubing to increase gas velocity and liquid-carrying capacity. This case highlights hanger setting, pressure verification, DHSV compatibility, and a two-stage offshore deployment workflow.
Challenge
During late-life offshore gas-well production, liquid loading can reduce gas velocity and constrain stable export pressure. The well also contains a downhole safety valve and control lines, requiring compact tools, reliable setting and sealing, and a recoverable deployment path.
Tooling and verification
The velocity-string system combines small-diameter tubing, a tubing-internal hanger, setting and connection tools, swivels, a shear sub, and retrieval tools. Shop validation covered setting, sealing, hanging load, release, and retrieval behavior, including 35 MPa seal verification and a 20 kN hanging-capacity requirement.
Field execution
The operation used a two-stage velocity-string workflow. The first string was run to the deeper target interval, then the hanger was set, pressure tested, and released. A second upper string was then installed and verified. Finally, pressure activation opened the lower flow path and connected the velocity string with the producing interval.
Result value
After installation, the well entered a more stable gas and liquid production state. The case demonstrates that CT velocity-string technology can support offshore dewatering gas production and production recovery while working with existing completion components such as a DHSV.