Recently, a kick was observed during the
wash-over of a gravel pack. Observed pressures were 1,100 psig on the casing and 1,800
psig on the workstring. Well-control operations were initiated by bull-heading into the
well, at which time pressure rose to 4,200 psig. The PSV located on the mud pump relieved,
allowing a mixture of gas, sand, and completion fluid to escape and inundate the area
around the drill floor and rig equipment. On at least two occasions prior to the incident,
the PSV had been subjected to pressures at or near its set pressure of 5,000 psig during
BOP tests.
It was concluded in an MMS investigation of
the incident that the PSV shear pin failed below its set pressure because of a possible
deformity of the pin resulting from repeated exposure to pressures at or near its set
pressure during testing. It was further concluded by MMS that an apparent failure to
inspect the shear pin visually after such pressure exposures would have revealed the
aforementioned deformity and thus represents a possible contributing cause of the
incident.
It is therefore recommended to operators and
contractors that:
PSV shear pins should be
visually inspected for integrity after having been exposed to pressures at or near their
relief pressures.
PSV’s should be
maintained in accordance with manufacturer’s recommendations.
PSV discharges should be
piped to a safe location so as to minimize interference with operations.
For details of the accident, see OCS Report MMS
2002-040. Copies of the report may be obtained from the MMS Public Information Office
located at 1201 Elmwood Park Boulevard, New Orleans, Louisiana 70123 (1-800-200-GULF or
local 504-736-2519).
