October 29, 2010
Flawed Cement Fingered As Possible Oil Spill Culprit
Officials participating in the federal government's investigation into the cause or causes of the Deepwater Horizon explosion and the ensuing oil spill appear to have found at least one potential culprit: faulty cement.
In a letter sent to members of the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, including Co-chairmen Bob Graham and William K. Reilly, Oil Spill Commission (OSC) chief counsel Fred Bartlit wrote that only one out of four preliminary tests conducted by Halliburton, the company which provided the cement used to seal the drilling rig, showed that their proposed concrete mixture would be able to hold.Furthermore, Bartlit claims that laboratory tests using materials provided by Halliburton were "unable to generate stable foam cement." Those tests were conducted at a Houston-based facility by cement industry experts at Chevron, Bartlit notes in his letter. Representatives from the laboratories are scheduled to speak to members of the Oil Spill Commission in November.
In response to the letter, Halliburton officials released a statement Thursday evening, in which they noted that the mixtures which failed initial testing were not "very similar" as was suggested in Bartlit's letter.
The company claimed that two of the tests, which were conducted in February, were "preliminary, pilot tests" and did not feature the same mixture used in later testing because "final well conditions were not known at that time."
Also at issue is how much BP knew about the quality of the cement, and what role they played in the testing process. Bartlit wrote in his letter that the British petroleum company "may or may not" have had results from the third test, a failed one which took place in April, prior to the evening of April 19, one day before the explosion that would kill 11 workers on board the Deepwater Horizon.
In their statement, Halliburton notes that BP "was made aware of the issues with that test" and that the test was "irrelevant because the laboratory did not use the correct amount of cement blend."
Furthermore, in the company's statement, Halliburton officials claim that following the one successful test, BP "subsequently instructed" them to make last-minute changes to the mixture, increasing the amount of retarder used from eight gallons per 100 sacks to cement to nine.
"Tests, including thickening time and compressive strength, were performed on the nine gallon formulation (the cement formulation actually pumped) and were shared with BP before the cementing job had begun. A foam stability test was not conducted on the nine gallon formulation," they added.
According to the Associated Press (AP), "The independent investigators do not address other decisions that could have contributed to the cement's failure and the eventual blowout, such as BP's decision to use fewer centralizers than recommended by Halliburton. Centralizers make sure the well's piping is centered inside the well so the cement bonds correctly."
"BP has also been criticized for not performing a cement bond long, a test that checks after the cement is pumped down whether it is secure," the AP also wrote on Thursday. "There are also questions about whether BP pumped down enough cement to seal off the bottom of the well, which was located more than three miles below sea level."
The April 20 explosion onboard the Deepwater Horizon resulted in what many are calling the worst environmental disaster in American history. For some five months after the leak began, just two days after the blast that caused the oil rig to sink, a total of 200 million gallons of petroleum leaked into the Gulf of Mexico, harming wildlife and crippling the region's fishing industry.
On Wednesday, as part of the ongoing investigation, a federal court in New Orleans ordered that a security perimeter be established around the site where the spill originated. The zone, which extends for 750 feet in all directions from where the Deepwater Horizon sank, was set up in order to prevent "tampering with the site and the surrounding area" and "is intended to serve as the equivalent of yellow crime-scene tape," according to Neela Banerjee of the Los Angeles Times.
On the Net:
- National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling