Congressional investigators released new documents Monday outlining “serious questions” that have been raised in their probe of the events leading up to the BP oil disaster. In a lengthy letter to BP CEO Tony Hayward, Reps. Henry Waxman (D-Calif.) and Bart Stupak (D-Mich.) outline numerous questions raised by evidence they have turned up about the possible causes of the blowout on April 20, advising Hayward that he should be prepared to respond to when he appears before the committee on Thursday.
The letter notes that, on April 15, five days before the explosion, BP’s drilling engineer referred to the well they were drilling as a “nightmare well.” “In spite of the well’s difficulties, BP appears to have made multiple decisions for economic reasons that increased the danger of a catastrophic well failure,” write the congressmen. “In several instances, these decisions appear to violate industry guidelines and were made despite warnings from BP’s own personnel and its contractors. In effect, it appears that BP repeatedly chose risky procedures in order to reduce costs and save time and made minimal efforts to contain the added risk.”
The letter highlights many issues about the operation that have come to light in the past weeks. Exploration at the well was behind schedule, which they note “appears to have created pressure to take shortcuts to speed finishing the well.”
The questions focus on five key points, which they note all “posed a trade-off between cost and well safety”:
(I) the decision to use a well design with few barriers to gas flow;
(2) the failure to use a sufficient number of “centralizers” to prevent channeling during the cement process;
(3) the failure to run a cement bond log to evaluate the effectiveness of the cement job;
(4) the failure to circulate potentially gas-bearing drilling muds out of the well; and
(5) the failure to secure the wellhead with a lockdown sleeve before allowing pressure on the seal from below.
The Energy and Commerce Committee has posted the letter and all the relevant documents here. The longer explanation of each point is below the jump:
Centralizers. When the final string of casing was installed, one key challenge was making sure the casing ran down the center of the well bore. As the American Petroleum Institute’s recommended practices explain, if the casing is not centered, “it is difficult, ifnot impossible, to displace mud effectively from the narrow side of the annulus,” resulting in a failed cement job. Halliburton, the contractor hired by BP to cement the well, warned BP that the well could have a “SEVERE gas flow problem” if BP lowered the final string of casing with only six centralizers instead of the 21 recommended by Halliburton. BP rejected Halliburton’s advice to use additional centralizers. In an e-mail on April 16, a BP official involved in the decision explained: “it will take 10 hours to install them . … I do not like this.” Later that day, another official recognized the risks of proceeding with insufficient centralizers but commented: “who cares, it’s done, end of story, will probably be fine.”
Cement Bond Log. BP’s mid-April plan review predicted cement failure, stating “Cement simulations indicate it is unlikely to be a successful cement job due to formation breakdown.” Despite this warning and Halliburton’s prediction of severe gas flow problems, BP did not run a 9- to 12-hour procedure called a cement bond log to assess the integrity of the cement seal. BP had a crew from Schlumberger on the rig on the morning of April 20 for the purpose of running a cement bond log, but they departed after BP told them their services were not needed. An independent expel1 consulted by the Committee called this decision “horribly negligent.”
Mud Circulation. In exploratory operations like the Macondo well, wells are generally filled with weighted mud during the drilling process. The American Petroleum Institute (API) recommends that oil companies fully circulate the drilling mud in the well from the bottom to the top before commencing the cementing process. Circulating the mud in the Macondo well could have taken as long as 12 hours, but it would have allowed workers on the rig to test the mud for gas influxes, to safely remove any pockets of gas, and to eliminate debris and condition the mud so as to prevent contamination of the cement. BP decided to forgo this safety step and conduct only a partial circulation of the drilling mud before the cement job.
Lockdown Sleeve. Because BP elected to use just a single string of casing, the Macondo well had just two barriers to gas flow up the annular space around the final string of casing: the cement at the bottom of the well and the seal at the wellhead on the sea floor. The decision to use insufficient centralizers created a significant risk that the cement job would channel and fail, while the decision not to run a cement bond log denied BP the opportunity to assess the status of the cement job. These decisions would appear to make it crucial to ensure the integrity of the seal assembly that was the remaining barrier against an influx of hydrocarbons. Yet, BP did not deploy the casing hanger lockdown sleeve that would have prevented the seal from being blown out from below.