Subsea flowline jumper failure releases ~16,000 bbl, Mississippi Canyon 209
A fractured subsea wellhead jumper (KAA-0120) connecting the MC 209 SS001 wellhead to a PLET released an estimated 16,000 barrels of oil while going undetected for several hours during start-up.
Source information
- Source
- Bureau of Safety and Environmental Enforcement
- Investigating authority
- Bureau of Safety and Environmental Enforcement
- Report / reference no.
- BSEE Panel 2019-002
- Publication date
- Dec 30, 2019
- Last verified
- Oct 4, 2026
Event description
LLOG shut in Delta House on October 6, 2017 ahead of Hurricane Nate. During ramp-up on October 10–11, control room operators saw multiphase flow meter rates that did not match LACT meter rates; BSEE found the discrepancy was attributed to meter issues rather than a leak.
Source / investigation findings: BSEE
Probable / root cause
The failure resulted from internal corrosion within the jumper and mechanical stress added to the jumper from movement of the PLET and pipeline (BSEE panel conclusion).
Contributing factors
- LLOG did not have any sensors in place that would alarm due to a suspected subsea leak; a PSL was installed but set below hydrostatic pressure.
- Control room operators were not trained to shut in wells for unexplained pressure fluctuations or metering discrepancies.
- BSEE found a prevalent mindset that meters are prone to malfunction and that subsea flowlines rarely fail.
Recommendations
- Evaluate designs of applicable components for their tolerance under increased loads due to thermal expansion or other movement.
- Evaluate the use and placement of sleepers or other components that mitigate the buckling of pipelines.
- Evaluate the use of different surveying methods such as LIDAR to confirm pipeline systems remain within design tolerances throughout their service life.
- Consider revisions to API RP 17V that include a section on subsea leak detection best practices.
Lessons learned
Gulf of America educational summary
The numbers were telling operators something was wrong for hours, but the team assumed a bad meter. A leak alarm that could never trip and no rule to shut in on unexplained discrepancies let a large release continue.
- An unexplained flow or pressure mismatch is a possible leak until proven otherwise.
- Check that alarm setpoints can actually activate under real conditions.
- Post-hurricane restarts deserve extra scrutiny of subsea integrity.
Plain-language interpretation by Gulf of America. Not a finding of BSEE or any investigating authority.