Final Report on Gulf Oil Spill Disaster Shares the Blame

By MarEx 2011-09-14 12:59:27

A key US report released today says poor risk management, last-minute changes to plans and faulty cement work were responsible for the massive Gulf of Mexico rig explosion and oil spill. The report gives shared responsibility to BP, Transocean and Haliburton for the deadly rig explosion on April 20, 2010 that killed 11, injured 16 others, and spilled more than 200 million gallons of oil into the Gulf of Mexico. 

These findings come from an investigation conducted by the U.S. Coast Guard and the Bureau of Ocean Energy Management, formerly the Minerals Management Service, who oversees drilling operations in US waters.

The panel found that the central cause of the blowout was “failure of a cement barrier in the production casing string.” The panel did say that the reasons for the cement failure were unknown but were likely caused by the swapping of cement and drilling mud in the shoe track; containment of the show track cement; or pumping the cement past the target location in the well.

The report identifies BP as ultimately responsible for conducting safe operations at the Macondo well – including protection of personnel, equipment, natural resources, and the environment. Transocean was identified as being responsible for protecting personnel onboard the Deepwater Horizon rig and conducting safe operations onboard. Haliburton was indentified as being responsible for the cement job and monitoring the well. And Cameron was responsible for the design of the blowout preventer.

The panel found that a series of decision led to the complicating of cement operations and added to the risk and contributed to the ultimate failure of the cement casing. The panel identified the decision as follows:

• The use of only one cement barrier.  BP did not set any additional cement or mechanical barriers in the well, even though various well conditions created difficulties for the production casing cement job.  

• The location of the production casing. BP decided to set production casing in a location in the well that created additional risk of hydrocarbon influx.  

• The decision to install a lock down sleeve.  BP’s decision to include the setting of a lock down sleeve (a piece of equipment that connects and holds the production casing to the wellhead during production) as part of the temporary abandonment procedure at Macondo increased the risks associated with subsequent operations, including the displacement of mud, the negative test sequence and the setting of the surface plug.  

• The production casing cement job.  BP failed to perform the production casing cement job in accordance with industry?accepted recommendations.


The Panel also found evidence that BP and in some cases it contractors, violated federal regulation. The following is a list of those federal regulations:

• 30 CFR § 250.107 – BP failed to protect health, safety, property, and the environment by (1) performing all operations in a safe and workmanlike manner; and (2) maintaining all equipment and work areas in a safe condition;  7

• 30 CFR § 250.300 – BP, Transocean, and Halliburton (Sperry Sun) failed to take measures to prevent the unauthorized release of hydrocarbons into the Gulf of Mexico and creating conditions that posed unreasonable risk to public health, life, property, aquatic life, wildlife, recreation, navigation, commercial fishing, or other uses of the ocean;

• 30 CFR § 250.401 – BP, Transocean, and Halliburton (Sperry Sun) failed to take necessary precautions to keep the well under control at all times; 

• 30 CFR § 250.420(a)(1) and (2) – BP and Halliburton failed to cement the well in a manner that would properly control formation pressures and fluids and prevent the release of fluids from any stratum through the wellbore into offshore waters; 

• 30 CFR § 250.427(a) – BP failed to use pressure integrity test and related hole?behavior observations, such as pore pressure test results, gas?cut drilling fluid, and well kicks to adjust the drilling fluid program and the setting depth of the next casing string;  

• 30 CFR § 250.446(a) – BP and Transocean failed to conduct major inspections of all BOP stack components; and 

• 30 CFR § 250.1721(a) – BP failed to perform the negative test procedures detailed in an application for a permit to modify its plans.

The panel also acknowledged that “stronger” federal regulations and enforcement by the Minerals Management Service may have reduced the likelihood of the incident. The report includes recommendations to improve offshore drilling operations with regards to well design, well integrity testing, kick detection and response, right engine configuration, blowout preventers, remotely-operated vehicles.

The report includes the following conclusion:

As detailed in this Report, the blowout at the Macondo well on April 20, 2010 was the result of a series of decisions that increased risk and a number of actions that failed to fully consider or mitigate those risks.  While it is not possible to discern which precise combination of these decisions and actions set the blowout in motion, it is clear that increased vigilance and awareness by BP, Transocean and Halliburton personnel at critical junctures during operations at the Macondo well would have reduced the likelihood of the blowout occurring. 

BP well designers set the casing in a location that created additional risks of hydrocarbon influx.  Even knowing this, BP did not set additional cement or mechanical barriers in the well.  BP made two additional significant decisions that further increased risks – first, it decided to have the Deepwater Horizon crew install a lock?down sleeve as part of the temporary abandonment procedure.  Second, BP decided to use a lost circulation material as spacer, which risked clogging lines used for well integrity tests.    

BP personnel and Transocean personnel failed to conduct an accurate negative test to assess the integrity of the production casing cement job.  The Deepwater Horizon rig crew, therefore, performed temporary abandonment procedures while unaware of the failed cement job beneath them and the looming influx of hydrocarbons.  Unfortunately, the rig crew then limited its kick detection abilities by deciding to bypass the Sperry Sun flow meter when displacing fluid from the well overboard.  

The Deepwater Horizon rig crew missed signs of a kick and thus was delayed in reacting to the well control situation.  Once the flow reached the rig floor, the crew closed the upper annular and upper variable bore ram and diverted the flow to the mud gas separator.  The mud gas separator could not handle the volume of the blowout and explosions followed.  Additionally, forensic analysis by DNV strongly suggests that by the time a crew member on the bridge activated the emergency disconnect system, the explosions had damaged the Deepwater Horizon’s multiplex cable and hydraulic lines, which rendered inoperable the BOP stack’s blind shear rams. 

The force of the blowout, and possibly the force from drill pipe in the riser, buckled the drill pipe and placed it in a position where it could not be completely sheared by the blind shear ram blades.  As a result, the blind shear201 ram, when activated on either April 20 or April 22, could not shear the drill pipe and seal the wellbore.  Flow from the Macondo well continued for 87 days after the blowout, spewing almost 5 million barrels of oil into the Gulf of Mexico.