Tubing String Equipment Failure During a Plug and Abandonment Operation
Effective Date: 8/22/1985
 | Minerals Management Service Gulf of Mexico OCS Region |
Notice No. 145
August 22, 1985
Tubing String Equipment Failure During a
Plug and Abandonment Operation
While a tubing string was being pulled to unseat a subsurface tubing hanger and to pull the seal assembly out of a packer, a telescoping swivel sub in the string parted at 585 feet. Tubing pressure of 500 psi below a closed subsurface safety valve located at 504 feet forced approximately 500 feet of tubing out of the well. The blowout preventers were closed, the well was brought under control by pump-and-bleed procedures, and operations were completed routinely. There were no injuries. Two barrels of completion fluid were spilled into the Gulf waters. It was later found that the telescoping swivel sub failed prematurely because an old-design sub box was mismated with a new-design mandrel pin and that internal parts had buckled under compressive loads.
To prevent a recurrence of this type of accident, the operator recommends that, to the extent practicable, specialty tools and tools with a limited service history be examined carefully to ensure that they have been tested to withstand the worst-case service conditions.
The Minerals Management Service recommends that, whenever feasible, a well should be completely killed and any trapped pressure bled off before the completion string is unseated from the packer.