Guidance
CY 1991-1994 Addendum
CY 1991-1994 Addendum
- BSEE
- Guidance
- Line of FireProcess Safety
- Line of firePressure systemsWell control
- Well intervention
- Blowout preventerValve
- Upstream oil and gas
- Offshore installation
Summary
This addendum records a fatal workover incident at well B-2 in South Marsh Island. Retrieving a back-pressure valve released trapped pressure and expelled well fluids and objects, killing one worker and injuring two. It identifies probable gas migration beneath the valve and describes pipe rams shutting in the well.
Classifications: Line of fire; struck-by hazards.
Classifications: Pressure systems; stored pressure; pressurised systems; pressurized systems.
Classifications: Well control; kick control; loss of well control.
Classifications: Well intervention; workover; well servicing.
Classifications: Blowout preventer; BOP; blow-out preventer.
Classifications: Valve; valves.
Classifications: Upstream oil and gas; oil and gas extraction; upstream petroleum.
Classifications: Offshore installation; offshore platform; offshore rig.
Summary
Addendum describing a 1994 workover loss of well control that killed one and injured two when trapped pressure was released.
Themes: line of fire, process safety.
Addendum to Accidents Associated with Oil and Gas Operations, Outer Continental Shelf, 1991-1994 OCS Report MMS 95-0052
The following incident is listed under the Injury/Fatality section in the above report. It should also be included in the Blowout section of the report on p. 8.
March 15, 1994 – Exxon Corporation
Investigation: Completed Activity: Development Loss of Well Control / Lease: G8684 Event(s): Fatality (1) / Injury (2)
Area: South Marsh Island Operation: Workover
Block: 90 Cause: Human Error
Rig/Platform: Well No. B-2 Water Depth: ~ 163 feet
Remarks: Nobile Drilling Inc.’s jack up rig Percy Johns was skidded over well B-2 on 3/12/94. The well had a sustained casing pressure of 800 psi on the casing/tubing annulus which was bled down to 250 psi before the well was pressured up to 6800 psi and the surface controlled subsurface safety valve (SCSSV) was opened and calcium bromide was bullheaded down the tubing to kill the well. A back-pressure valve was set in the tubing hanger and the wellhead was removed. The blowout prevention (BOP) stack was nippled up and the BOP stack and associated equipment was pressure tested as required. Seawater was pumped from the BOP riser and tubing hanger. While attempting to retrieve the back-pressure valve from the tubing hanger, the tubing jumped several feet in the air and a loss of well control occurred as pressure was released, and fluids were expelled, from the wellbore. The tubing was not blown out of the riser but was bent. The pressure release also caused the rotary bushing inserts to be blown from the rotary table onto the drill floor. Almost immediately, the upper set of pipe rams were activated which shut in the well and stopped the release of pressure onto the drill floor.
An Exxon company man who was standing on the drill floor near the rotary table was struck in the chest by an object expelled from the well during the incident. No one witnessed the accident but one of the rotary bushing inserts was found next to the deceased. A Cooper employee was injured as the force of the pressure blew him into the pipe rack. A Noble employee was also injured as fluid from the wellbore was blown into his face.
The probable cause of the incident was the removal of the back-pressure valve with pressure trapped below it. After the well was killed and the SCSSV was closed, gas migrated up the wellbore and became trapped under the back-pressure valve. See OCS REPORT MMS 95- 0041.