Thomas Roth, vice president of cementing at Halliburton, denied that the company's cement design for the Macondo well was flawed, as BP has charged, or that nitrogen bubbles designed to make the cement foam up like shaving cream instead contaminated the cement, making it impossible to set.
Roth questioned the conclusions reached by BP in its internal investigation, which faults the cement design and execution in part for allowing hydrocarbons to seep into the well bore and reach the surface where they exploded.
Roth made his comments at a meeting of a committee formed by the US National Academy of Engineering to analyze the cause of the blowout, fire and oil spill and to recommend measures to prevent such a disaster in future. The group, formed at the request of Interior Secretary Ken Salazar, is expected to issue a preliminary report by the end of October.
Roth said BP ignored data showing that the cementing of the well could be compromised if BP used seven centralizers instead of the 21 Halliburton recommended. Roth also said that Halliburton's nitrogen-based cement passed all key tests and did not fail as BP has suggested.
Halliburton employee John Gisclair said BP's well design made it nearly physically impossible to run a cement bond log test, which was the only sure way to know if the cement job had set properly.
But under questioning from the scientists on the panel, Roth said that cement could have fractured an unstable hydrocarbon reservoir, causing gas and crude to enter the well undetected. He also said that channeling--a common result of using too few centralizers--was not by itself an unsafe condition.
Halliburton's presentation caused committee chair Donald Winter to wonder why Halliburton did not call a halt to drilling activities until the problems could be fixed.
"Given all the concerns that you voiced today...why did you pursue it? Why didn't you pull the red cord and say 'This is an unsafe operation?'" Winter asked.
Roth replied: "We didn't see it to be an unsafe operation as it was being executed."
The Halliburton executives repeated that they worked for BP and could not force the company to accept its recommendations or alter the well design.
Halliburton's presentation came after BP executives said company officials did not formally review the design of a cement job on the Macondo well.
Under questioning by Winter, the BP team said company officials met twice to discuss Halliburton's plans to use a nitrogen-based cement. Officials signed off on the plan that was eventually sent to the rig for execution, Mark Bly, BP group head of safety and operations, said.
But while BP agreed with Halliburton to use a lighter, foaming cement, BP did not conduct its own analysis of the cement slurry Halliburton used to seal the Macondo well.
"Was there a formal review done on the cement slurry design? No," Bly said.
Still, the report produced under Bly's leadership concluded that it was the design of the slurry, including how much nitrogen was pumped into the cement, that failed to keep hydrocarbons from entering the well in the hours before the explosion on the rig.
Another panel member questioned whether the cement design adequately took into consideration the differing pressures of the hydrocarbon reservoirs in the well.
Three layers of hydrocarbons existed and by using one cement design Halliburton may have inadvertently fractured one of the formations, causing hydrocarbons to flow, panel member Mark Zoback suggested.
China Chemical Weekly: http://news.chemnet.com/en/detail-1411716.html
