BP spill: Lists reveal what is known, what could have happened

By OGJ editors
HOUSTON, May 14
-- Two documents were released May 12 at the hearing held by the US Oversight and Investigations subcommittee to inquire into the Deepwater Horizon Gulf Coast oil spill. These lists, entitled “What We Know” and “What Could Have Happened,” are reproduced below.

What We Know
• Before, during, or after the cement job, an undetected influx of hydrocarbons entered the wellbore.

• The 9-7/8-in. casing was tested, the 9-7/8-in. casing hanger packoff was set and tested, and the entire system was tested.

• After 16½ hr waiting on cement, a test was performed on the wellbore below the blowout preventer (BOP).

• During this test, 1,400 psi was observed on the drill pipe while 0 psi was observed on on the kill and the choke lines.

• Following the test, hydrocarbons were unknowingly circulated to surface while displacing the riser with seawater.

• As hydrocarbons rose to the surface, they expanded, further reducing the hydrostatic pressure. The well flowed and witness accounts suggest that the annular preventer in the BOP and the diverter were activated.

• An explosion occurred, followed by a power failure.

• Witness accounts that the emergency disconnect system was activated.

• The rig was evacuated.

• The BOP system failed to work as intended. Flow was not contained and the lower marine riser package did not disconnect.

• Modification have been discovered in the BOP system.

• Leaks have been discovered in the BOP hydraulics system.

• BP launched an investigation, which is ongoing.

Investigation themes 

• Cementing—design and execution.

• Casing—design and installation.

• Casing hanger—design and installation.

• BOP—configuration, maintenance, and operation.

• Well control practices.

What Could Have Happened
1. Before or during the cement job, an influx of hydrocarbon enters the wellbore.

2. Influx is circulated during cement job to wellhead and BOP.

3. 9-7/8-in. casing hanger packoff set and positively tested to 6,500 psi.

4. After 16½ hr waiting on cement, a negative test performed on wellbore below BOP. (~1,400 psi differential pressure on 9-7/8-in. casing hanger packoff and ~2,350 psi on double-valve float collar)

5. Packoff leaks allowing hydrocarbon to enter wellbore below BOP. 1,400 psi shut in pressure observed on drill pipe (no flow or pressure observed on kill line).

6. Hydrocarbon below BOP is unknowingly circulated to surface while finishing displacing the riser.

7. As hydrocarbon rises to surface, gas break out of solution further reduces hydrostatic pressure in well. Well begin to flow, BOPs and emergency disconnect system (EDS) activated but failed.

8. Packoff continues to leak allowing further influx from bottom.

Related Articles

Kulluk conical drilling unit

USCG: ‘Chain of errors’ led to Shell drilling unit running aground

04/04/2014 A US Coast Guard (USCG) investigation has found that a “chain of errors” led to the Royal Dutch Shell PLC conical drilling unit, the Kulluk, runnin...

Statoil farms out 15% interest in block offshore Angola

04/03/2014 Statoil ASA has agreed to farm out a 15% interest in Block 39 of the Kwanza presalt basin offshore Angola to WRG Angola Block 39 Ltd. (WRG). The de...

WoodMac: Bakken drilling, completion capex to top $15 billion in 2014

04/02/2014 Oil and gas industry analyst Wood Mackenzie Ltd. forecasts that operators in the Bakken shale will invest more than $15 billion on drilling and com...

Moody’s: Marcellus shale gas producers to benefit most in US

04/01/2014 Natural gas producers in the Marcellus shale will benefit more than producers elsewhere in the US because of many favorable circumstances, even if ...

Careers at TOTAL

Careers at TOTAL - Videos

More than 600 job openings are now online, watch videos and learn more!

 

Click Here to Watch

Other Oil & Gas Industry Jobs

Search More Job Listings >>
Stay Connected